Advances in fruit processing technologies.pdf

Contemporary Food EngineeringSeries Editor

Professor Da-Wen Sun, DirectorFood Refrigeration & Computerized Food Technology

National University of Ireland, Dublin(University College Dublin)

Dublin, Ireland http://www.ucd.ie/sun/

Advances in Fruit Processing Technologies, edited by Sueli Rodrigues and Fabiano Andre Narciso Fernandes (2012)

Biopolymer Engineering in Food Processing, edited byVnia Regina Nicoletti Telis (2012)Operations in Food Refrigeration, edited by Rodolfo H. Mascheroni (2012)Thermal Food Processing: New Technologies and Quality Issues, Second Edition,

edited by Da-Wen Sun (2012)Physical Properties of Foods: Novel Measurement Techniques and Applications,

edited by Ignacio Arana (2012)Handbook of Frozen Food Processing and Packaging, Second Edition,

edited by Da-Wen Sun (2011)Advances in Food Extrusion Technology, edited by Medeni Maskan and Aylin Altan (2011)Enhancing Extraction Processes in the Food Industry, edited by Nikolai Lebovka, Eugene

Vorobiev, and Farid Chemat (2011)Emerging Technologies for Food Quality and Food Safety Evaluation,

edited by Yong-Jin Cho and Sukwon Kang (2011)Food Process Engineering Operations, edited by George D. Saravacos and

Zacharias B. Maroulis (2011)Biosensors in Food Processing, Safety, and Quality Control, edited by Mehmet Mutlu (2011)Physicochemical Aspects of Food Engineering and Processing, edited by

Sakamon Devahastin (2010)Infrared Heating for Food and Agricultural Processing, edited by Zhongli Pan and Griffiths

Gregory Atungulu (2010) Mathematical Modeling of Food Processing, edited by Mohammed M. Farid (2009)Engineering Aspects of Milk and Dairy Products, edited by Jane Slia dos Reis Coimbra

and Jos A. Teixeira (2009)Innovation in Food Engineering: New Techniques and Products, edited by Maria Laura Passos

and Claudio P. Ribeiro (2009) Processing Effects on Safety and Quality of Foods, edited by Enrique Ortega-Rivas (2009)Engineering Aspects of Thermal Food Processing, edited by Ricardo Simpson (2009)Ultraviolet Light in Food Technology: Principles and Applications, Tatiana N. Koutchma,

Larry J. Forney, and Carmen I. Moraru (2009)Advances in Deep-Fat Frying of Foods, edited by Serpil Sahin and Servet Glm Sumnu (2009) Extracting Bioactive Compounds for Food Products: Theory and Applications,

edited by M. Angela A. Meireles (2009)Advances in Food Dehydration, edited by Cristina Ratti (2009)Optimization in Food Engineering, edited by Ferruh Erdogdu (2009) Optical Monitoring of Fresh and Processed Agricultural Crops, edited by Manuela Zude (2009)Food Engineering Aspects of Baking Sweet Goods, edited by Servet Glm Sumnu

and Serpil Sahin (2008)Computational Fluid Dynamics in Food Processing, edited by Da-Wen Sun (2007)

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v

ContentsSeries Preface ...........................................................................................................viiSeries Editor ..............................................................................................................ixPreface.......................................................................................................................xiEditors .................................................................................................................... xiiiContributors .............................................................................................................xv

Chapter 1 Ultraviolet Light for Processing Fruits and Fruit Products ..................1

Tatiana Koutchma and Marta Orlowska

Chapter 2 High-Pressure Processing .................................................................. 37

Fabiano A.N. Fernandes

Chapter 3 Ultrasound Applications in Fruit Processing ..................................... 51

Fabiano A.N. Fernandes and Sueli Rodrigues

Chapter 4 Membrane Applications in Fruit Processing Technologies ................87

Sunando DasGupta and Biswajit Sarkar

Chapter 5 High-Intensity Pulsed Electric Field Applications inFruitProcessing ........................................................................... 149

Ingrid Aguil-Aguayo, Pedro Elez-Martnez, RobertSoliva-Fortuny, and Olga Martn-Belloso

Chapter 6 Applications of Ozone in Fruit Processing ...................................... 185

Patrick J. Cullen and Brijesh K. Tiwari

Chapter 7 Irradiation Applications in Fruit and Other Fresh ProduceProcessing ..........................................................................203

Rosana G. Moreira and Elena M. Castell-Perez

Chapter 8 Minimal Processing ......................................................................... 217

Ebenzer de Oliveira Silva, Maria do Socorro Rocha Bastos, NdioJairWurlitzer, Zoraia de Jesus Barros, and Frank Mangan

vi Contents

Chapter 9 Enzyme Maceration ......................................................................... 235

Sueli Rodrigues

Chapter 10 Fruit and Fruit Juices as Vehicles for Probiotic Microorganisms and Prebiotic Oligosaccharides ........................................................ 247

Sueli Rodrigues

Chapter 11 Freeze Concentration Applications in Fruit Processing ................... 263

Merc Ravents, Eduard Hernndez, and Josep Maria Auleda

Chapter 12 Refrigeration and Cold Chain Effect on Fruit Shelf Life .................287

Jos Maria Correia da Costa and Edmar Clemente

Chapter 13 Vacuum Frying of Fruits Applications in Fruit Processing ............. 331

Rosana G. Moreira

Chapter 14 Edible Coatings ................................................................................ 345

Henriette Monteiro Cordeiro de Azeredo

Chapter 15 Thermal Treatment Effects in Fruit Juices ....................................... 363

Ftima A. Miller and Cristina L.M. Silva

Chapter 16 Effect of Fruit Processing on Product Aroma .................................. 387

Narendra Narain and Jane de Jesus da Silveira Moreira

Chapter 17 Sensory Evaluation in Fruit Product Development .......................... 415

Deborah dos Santos Garruti, HeliofbiaVirginia de Vasconcelos Facundo, Janice RibeiroLima, and Andra Cardoso de Aquino

vii

Series PrefaceContemporary Food Engineering

Food engineering is the multidisciplinary field of applied physical sciences combined with the knowledge of product properties. Food engineers provide the technological knowledge transfer essential to the cost-effective production and commercialization of food products and services. In particular, food engineers develop and design pro-cesses and equipment to convert raw agricultural materials and ingredients into safe, convenient, and nutritious consumer food products. However, food engineering top-ics are continuously undergoing changes to meet diverse consumer demands, and the subject is being rapidly developed to reflect market needs.

In the development of food engineering, one of the many challenges is to employ modern tools and knowledge, such as computational materials science and nano-technology, to develop new products and processes. Simultaneously, improving food quality, safety, and security continues to be a critical issue in food engineering study. New packaging materials and techniques are being developed to provide more pro-tection to foods, and novel preservation technologies are emerging to enhance food security and defense. Additionally, process control and automation regularly appear among the top priorities identified in food engineering. Advanced monitoring and control systems are developed to facilitate automation and flexible food manufac-turing. Furthermore, energy saving and minimization of environmental problems continue to be important food engineering issues, and significant progress is being made in waste management, efficient utilization of energy, and reduction of effluents and emissions in food production.

The Contemporary Food Engineering Series, consisting of edited books, attempts to address some of the recent developments in food engineering. The series covers advances in classical unit operations in engineering applied to food manufacturing as well as such topics as progress in the transport and storage of liquid and solid foods; heating, chilling, and freezing of foods; mass transfer in foods; chemical and biochemical aspects of food engineering and the use of kinetic analysis; dehydration, thermal processing, nonthermal processing, extrusion, liquid food concentration, membrane processes, and applications of membranes in food processing; shelf-life and electronic indicators in inventory management; sustainable technologies in food processing; and packaging, cleaning, and sanitation. These books are aimed at pro-fessional food scientists, academics researching food engineering problems, and graduate-level students.

The editors of these books are leading engineers and scientists from many parts of the world. All the editors were asked to present their books to address the markets need and pinpoint the cutting-edge technologies in food engineering.

viii Series Preface

All the contributions have been written by internationally renowned experts who have both academic and professional credentials. All the authors have attempted to provide critical, comprehensive, and readily accessible information on the art and science of a relevant topic in each chapter, with reference lists for further informa-tion. Therefore, each book can serve as an essential reference source to students and researchers in universities and research institutions.

Da-Wen SunSeries Editor

ix

Series EditorProfessor Da-Wen Sun, PhD, is a world author-ity on food engineering research and education; he is a member of the Royal Irish Academy, which is the highest academic honor in Ireland; he is also a member of Academia Europaea (The Academy of Europe). His main research activities include cooling, drying, and refrigeration processes and systems; quality andsafety of food products; bio-process simulation and optimization; and computer vision technology.

In particular, his innovative studies on vacuum cooling of cooked meat, pizza quality inspection using computer vision, and edible films for shelf-life extension of fruits and vegetables have been widely reported in the national and international media. Results of his work have been published in about 600 papers, including over 250 peer-reviewed journal papers (h-index = 36). Hehas also edited 13 authoritative books. According to Thomson Scientifics Essential Science IndicatorsSM updated as of July 1, 2010, based on data derived over a period of ten years and four months (January 1, 2000April 30, 2010) from the ISI Web of Science, a total of 2554 scientists are among the top 1% of the most cited scientists in the category of agriculture sciences, and Professor Sun is listed at the top with a ranking of 31.

Dr. Sun received his first class BSc honors and his MSc in mechanical engineer-ing, and his PhD in chemical engineering in China before working at various univer-sities in Europe. He became the first Chinese national to be permanently employed in an Irish university when he was appointed a college lecturer at the National University of Ireland, Dublin (University College Dublin [UCD]), in 1995. He was then continuously promoted in the shortest possible time to the position of senior lec-turer, associate professor, and full professor. Dr. Sun is now a professor of food and biosystems engineering and director of the Food Refrigeration and Computerized Food Technology Research Group at UCD.

As a leading educator in food engineering, Dr. Sun has contributed significantly to the field of food engineering. He has guided many PhD students who have made their own contributions to the industry and academia. He has also, on a regular basis, given lectures on the advances in food engineering at international academic institu-tions and delivered keynote speeches at international conferences. As a recognized authority in food engineering, Dr. Sun has been conferred adjunct/visiting/consulting professorships by over ten top universities in China, including Zhejiang University, Shanghai Jiaotong University, Harbin Institute of Technology, China Agricultural University, South China University of Technology, and Jiangnan University. In rec-ognition of his significant contribution to food engineering worldwide and for his outstanding leadership in the field, the International Commission of Agricultural and

x Series Editor

Biosystems Engineering (CIGR) awarded him the CIGR Merit Award in 2000 and again in 2006; the U.K.-based Institution of Mechanical Engineers named him Food Engineer of the Year 2004; in 2008, he was awarded the CIGR Recognition Award in recognition of his distinguished achievements as the top 1% of agricultural engi-neering scientists around the world; in 2007, he was presented with the only AFST(I) Fellow Award in that year by the Association of Food Scientists and Technologists (India); and in 2010, he was presented with the CIGR Fellow Award (the title of Fellow is the highest honor in CIGR and is conferred upon individuals who have made sustained, outstanding contributions worldwide).

Dr. Sun is a fellow of the Institution of Agricultural Engineers and a fellow of Engineers Ireland (the Institution of Engineers of Ireland). He has also received numerous awards for teaching and research excellence, including the Presidents Research Fellowship, and has received the Presidents Research Award from UCD on two occasions. He is also the editor in chief of Food and Bioprocess TechnologyAn International Journal (Springer) (2010 Impact Factor = 3.576, ranked at the fourth position among 126 ISI-listed food science and technology journals); series editor of the Contemporary Food Engineering Series (CRC Press/Taylor & Francis Group); former editor of Journal of Food Engineering (Elsevier); and an editorial board member of Journal of Food Engineering (Elsevier), Journal of Food Process Engineering (Blackwell), Sensing and Instrumentation for Food Quality and Safety (Springer), and Czech Journal of Food Sciences. Dr. Sun is also a chartered engineer.

On May 28, 2010, he was awarded membership to the Royal Irish Academy (RIA), which is the highest honor that can be attained by scholars and scientists working in Ireland. At the 51st CIGR General Assembly held during the CIGR WorldCongress in Quebec City, Canada, in June 2010, he was elected as incom-ing president of CIGR and will become CIGR president in 20132014. The term of the presidency is six yearstwo years each for serving as incoming president, president, and past president. On September 20, 2011, he was elected to Academia Europaea (The Academy of Europe), which is functioning as European Academy of Humanities, Letters and Sciences and is one of the most prestigious academies in the world; election to the Academia Europaea represents the highest academic distinction.

xi

PrefaceFruits are major food products and key ingredients in many processed foods. They are a rich source of vital nutrients and constitute an important component of human nutrition. Consumers nowadays are more aware of the importance of healthy foods and require food products with high nutritional value along with high standards of sensory characteristics. Thus, fruit processing has to preserve the nutritional value of the fruit, while also preserving its natural color and flavor. This book reviews new advances in fruit-processing technologies.

Fruits are highly perishable, and about 20%40% of the fruits produced are wasted from the time of harvesting till they reach the consumers, either in natural form or in processed form. To reduce fruit loss and improve final sensory characteristics of processed fruits, new or improved technologies have been applied to fruit processing. This book reviews new technologies, such as ozone application, ultrasound process-ing, irradiation application, pulsed electric field, vacuum frying, and high-pressure processing, and improved technologies, such as ultraviolet and membrane processing, enzymatic maceration, freeze concentration, and refrigeration.

The effect of processing on sensory characteristics and nutritional value is addressed in each chapter. New trends in modified atmosphere packaging, effects of processing on aroma, and the use of fruit juices as a vehicle for probiotic microor-ganisms and prebiotic oligosaccharides as an alternative for dairy products are also covered in this book.

xiii

EditorsSueli Rodrigues is currently a professor of food engineering at the Federal University of Cear, Fortaleza, Brazil, where she teaches and does research on pro-cess and product development. She graduated in chemical engineering from the State University of Campinas, Campinas, So Paulo, Brazil, and received her PhD in chemical engineering in 2003 from the same university.

Dr. Rodrigues has published more than 65 papers in scientific journals. Her research interests include bioprocess, ultrasound, and drying technology, especially with fruit and functional food processing.

Fabiano Andr Narciso Fernandes is currently a professor of chemical engineer-ing at the Federal University of Cear, Fortaleza, Brazil, where he teaches and does research on process and product development. He graduated in chemical engineering from the Federal University of So Carlos, So Carlos, So Paulo, Brazil. He received his PhD in chemical engineering in 2002 from the Sate University of Campinas, Campinas, So Paulo, Brazil.

Dr. Fernandes has published more than 90 papers in scientific journals. His research interests include drying technology, ultrasound technology, and the field of reaction engineering.

xv

Contributors

Ingrid Aguil-AguayoDepartment of Food TechnologyUniversity of LleidaLleida, Spain

Andra Cardoso de AquinoDepartment of Chemical EngineeringFederal University of CearCear, Brazil

Josep Maria AuledaDepartment of Agri-Food Engineering

and BiotechnologyTechnical University of CataloniaBarcelona, Spain

Henriette Monteiro Cordeiro de AzeredoEmbrapa Tropical AgroindustryBrazilian Agricultural Research

CorporationFortaleza, Brazil

Zoraia de Jesus BarrosDepartment of Plant, Soil, and Insect

SciencesUniversity of MassachusettsAmherst, Massachusetts

Maria do Socorro Rocha BastosEmbrapa Tropical AgroindustryBrazilian Agricultural Research


Elena M. Castell-PerezDepartment of Biological and

Agricultural EngineeringTexas A&M UniversityCollege Station, Texas

Edmar ClementeDepartment of ChemistryState University of MaringMaring, Brazil

Jos Maria Correia da CostaDepartment of Food TechnologyFederal University of CearFortaleza, Brazil

Patrick J. CullenSchool of Food Science and

Environmental HealthDublin Institute of TechnologyDublin, Ireland

Sunando DasGuptaDepartment of Chemical EngineeringIndian Institute of TechnologyKharagpur, India

Pedro Elez-MartnezDepartment of Food TechnologyUniversity of LleidaLleida, Spain

Heliofbia Virginia de Vasconcelos FacundoDepartment of Food and Experimental

NutritionUniversity of So PauloSo Paulo, Brazil

Fabiano Andr Narciso FernandesDepartment of Chemical EngineeringFederal University of Cear Fortaleza, Brazil

xvi Contributors

Deborah dos Santos GarrutiEmbrapa Tropical AgroindustryBrazilian Agricultural Research


Eduard HernndezDepartment of Agri-Food Engineering


Tatiana KoutchmaGuelph Food Research CenterAgriculture and Agri-Food CanadaGuelph, Ontario, Canada

Janice Ribeiro LimaEmbrapa Tropical AgroindustryBrazilian Agricultural Research


Frank ManganDepartment of Plant, Soil, and Insect

SciencesUniversity of MassachusettsAmherst, Massachusetts

Olga Martn-BellosoDepartment of Food TechnologyUniversity of LleidaLleida, Spain

Ftima A. MillerCenter of Biotechnology and Fine

ChemistryBiotechnology Higher SchoolCatholic University of PortugalPorto, Portugal

Jane de Jesus da Silveira MoreiraDepartment of Food TechnologyFederal University of SergipeSo Cristvo, Brazil

Rosana G. MoreiraDepartment of Biological and

Agricultural EngineeringTexas A&M UniversityCollege Station, Texas

Narendra NarainDepartment of Food TechnologyFederal University of SergipeSo Cristvo, Brazil

Marta OrlowskaGuelph Food Research CenterAgriculture and Agri-Food CanadaGuelph, Ontario, Canada

Merc RaventsDepartment of Agri-Food Engineering


Sueli RodriguesDepartment of Food TechnologyFederal University of CearFortaleza, Brazil

Biswajit SarkarUniversity School of Chemical

TechnologyGuru Gobind Singh Indraprastha

UniversityNew Delhi, India

Cristina L.M. SilvaCenter of Biotechnology and Fine

ChemistryBiotechnology Higher SchoolCatholic University of PortugalPorto, Portugal

xviiContributors

Ebenzer de Oliveira SilvaEmbrapa Tropical AgroindustryBrazilian Agricultural Research


Robert Soliva-FortunyDepartment of Food TechnologyUniversity of LleidaLleida, Spain

Brijesh K. TiwariHollings FacultyManchester Food Research CentreManchester Metropolitan UniversityManchester, United Kingdom

Ndio Jair WurlitzerEmbrapa Tropical AgroindustryBrazilian Agricultural Research


1

1 Ultraviolet Light for Processing Fruits and Fruit Products

Tatiana Koutchma and Marta Orlowska

CONTENTS

1.1 Introduction......................................................................................................21.2 BasicsofUVProcessingofFoodsofPlantOrigin..........................................3

1.2.1 UVLightSources.................................................................................31.2.1.1 MercuryLamps......................................................................31.2.1.2 EnvironmentalImpact...........................................................51.2.1.3 PulsedLamps.........................................................................61.2.1.4 LightEmittingDiodes...........................................................7

1.2.2 UVLightPropagation..........................................................................71.2.3 BasicPrinciplesofPhotochemistry......................................................8

1.3 UVLightControlMeasuresinFruitProcessingFacilities..............................91.3.1 AirTreatment........................................................................................91.3.2 WaterTreatment...................................................................................91.3.3 NonfoodandFoodContactSurfaceDisinfection.............................. 101.3.4 Packaging............................................................................................ 101.3.5 FreshFruitandCutFruitSurfacesTreatment.................................... 11

1.4 UVTreatmentofWholeFreshFruits............................................................. 111.4.1 AntimicrobialEffect........................................................................... 111.4.2 PlantAntimicrobialDefenseMechanismTriggeredbyUV.............. 131.4.3 EffectsonBioactiveCompounds........................................................ 141.4.4 StorageofPost-UV-TreatedFruits...................................................... 161.4.5 FormationofVitaminD..................................................................... 161.4.6 EffectsonGeneralAppearance.......................................................... 18

1.5 UVTreatmentofFresh-CutProduce.............................................................. 181.6 UVPasteurizationofFreshJuices.................................................................. 21

1.6.1 UVAbsorptionofFreshJuices........................................................... 211.6.2 DesignofUVSystems........................................................................231.6.3 InactivationofPathogenic,Nonpathogenic,

andSpoilageOrganisms..................................................................241.6.4 InactivationofEnzymes.....................................................................241.6.5 EffectsonEssentialVitamins.............................................................27

2 Advances in Fruit Processing Technologies

1.1 INTRODUCTION

Duringthelastdecade,therehasbeenanincreaseintheproductionoffreshfruitandfruitproductsduetothehealthpropertiesoffruits.Fruitproductscanbecon-sumedinraw,minimallyprocessedorprocessed,ready-to-eat/ready-to-drinkformsaswholefreshfruits,fresh-cutfruits,andfruitsasingredients,beverages,juices,andjams.Theprocessingoffruitsstartsafterharvestingandconsistsoffouractivities:stabilizationorpreservation,transformation,productionofingredients,andproduc-tionoffabricatedfoods.Theroleofprocessingtechnologyineachstageimpliesthecontrol ofmicrobiological, chemical, andbiochemical changes,whichoccur as aresultofmicrobialandenzymaticactivities,andoxidationreactions,whichcanleadtoproblemsofsafety,color,flavor,taste,andtexture.Processingtechnologiesthatdonotsignificantlyaltertheorganolepticornutritionalqualitiesoffruitsanddonotformanyundesirablechemicalcompoundsintheproducthaveobviousadvantagesinmodernfoodproduction.Theinterestinso-calledminimalprocessingtechnolo-giesledtothedevelopmentofnonthermalormildheathigh-techmethodsthathavethepotentialtoreplacetraditionalthermalpreservationtechniques.Theyresultnotonlyinbetterqualityandlongershelflifebutalso,potentially,inhighernutritionalvalueorproductswithhealthbenefits.A largenumberofstudieshaveassociatedconsumptionoffruitsandtheirproductswithdecreasedriskofdevelopmentofdis-easessuchascancerandcoronaryheartdisease(Hansenetal.,2003).Thismaybedue to thepresenceofhealth-promotingphytochemicals suchas carotenoids,fla-vonoids,phenoliccompounds,andvitamins(Gardneretal.,2000),whichhave,insomecases,beenshowntohavedisease-preventingproperties.Inthisrespect,itisofparamountimportancetodevelopprocessingmethodsthatpreservenotonlythesafetyoffruitsbutalsothesensorialandnutritionalqualityandbioactivityoftheconstituentspresentinfruitsandtheirproducts.

Ultraviolet(UV)lighttreatmentoffoodsisanonthermalphysicalmethodofpres-ervationthatisfreeofchemicalsandwasteeffluents,whichmakesitecologicallyfriendly.Itdoesnotproduceby-products.Itissafetouse,althoughprecautionsmustbetakentoavoidhumanexposuretoUVlightandtoevacuateozonegeneratedbyvacuumandfarUVwavelengths.Basedonrecentengineeringadvancesandnewscientificdata,UVlighttechnologyincontinuousandpulsedmodes(cUVandPL)offersthepromiseofenhancedmicrobiologicalsafetyoffreshfruitsandimprovedqualityoffruitproductsthathaveafreshnessofflavor,color,texture,andnutritionalvaluecloser to thoseofnontreatedproducts.ThediscoveryofUVinactivationofthechlorine-resistantparasitesCryptosporidium parvumandGiardiasp.hascata-lyzed the use of UV light in the water industry (Hijnen et al., 2006). UV hasbeenutilizedsimilarlyinthedisinfectionofair,nonfoodcontact,andfoodcontactsurfaces,andrecentlywasusedfortreatmentsofsurfacesofsolidfoodsandliquid

1.6.6 DestructionandFormationofFuran..................................................281.6.7 DestructionofPatulin.........................................................................29

1.7 ConclusionsandFutureTrends......................................................................29ListofAbbreviations................................................................................................ 31References................................................................................................................ 31

3Ultraviolet Light for Processing Fruits and Fruit Products

foods,beverages,andingredients.ReportsareavailablethatindicatethatapplicationofUVlightcanalsoimprovethetoxicologicalsafetyoffoodsofplantoriginthroughitsabilitytoreducelevelsoftoxinssuchaspatulinmycotoxininfreshapplecider(Dongetal.,2010)andpossiblytocontrolbrowningthroughitseffectsonenzymes(Manzoccoetal.,2009).Regardingthepreservationoforganolepticandnutritionalattributes,recentresearchhasshownpromisingresultsintheexposureoffruitprod-uctstoUVirradiation.Inadditiontohighercost-efficiency,sustainability,andbroadantimicrobialeffects,UVlightnotonlyminimallyaffectsqualityattributesbutalsohasbeneficialeffectsonthecontentofbioactivecompounds.Ithasthepotentialforobtainingpremiumqualityproductsthatcanleadtofastercommercialization.

This chapter aims to provide detailed and critical information on the latestapplicationsofcontinuousandpulsedUVlightforprocessingfreshfruitsandfruitsproducts.ThefundamentalprinciplesandfeaturesofUVlightgeneration,propa-gation, and photochemistry are briefly reviewed, and the control measures to beadoptedwhereUVtechnologycanbeutilizedtoenhancesafetyduringfruitproduc-tionareanalyzed.ParticularfocusisgiventotheeffectsofUVlightonthesurvivalofpathogenicand spoilagemicroorganisms typical to fruits and theenvironmentessentialinfruitprocessingfollowedbyadiscussionofrecentresearchintoeffectsofUVlightonqualityandbioactivecompounds.

1.2 BASICSOFUVPROCESSINGOFFOODSOFPLANTORIGIN

1.2.1 UVLightSoUrceS

Lightisemittedfromgasdischargeatwavelengthsdependentonitselementalcom-position and the excitation, ionization, andkinetic energyof those elements.Gasdischarges are responsible for the light emitted from UV lamps. UV light trans-ferphenomenonisdefinedbytheemissioncharacteristicsoftheUVsourcealongwith considering long-term lamp aging and absorbance/scattering of the product.Consequently,theperformanceofaUVsystemdependsonthecorrectmatchingoftheUVsourceparameterstothedemandsoftheUVapplication.ThecommerciallyavailableUVsourcesincludelow-andmedium-pressuremercurylamps(LPMandMPM),excimer lamps(EL),pulsed lamps(PL),and light-emittingdiodes (LED).LPM and EL are monochromatic sources, whereas emission of MPM and PL ispolychromatic.TherearenoreportsontheapplicationofELinfruitprocessing,sothisUVsourceisnotdiscussedinthischapter.

1.2.1.1 MercuryLampsMercuryvaporUVlampsourceshavebeensuccessfullyusedinwatertreatmentfornearly50yearsandareconsideredas reliable sources forotherdisinfectiontreatments thatbenefit from theirperformance, lowcost, andquality.Typically,three general types of mercury UV lamps are used: low-pressure (LPM), low-pressurehigh-output(LPHO),andmedium-pressure(MPM).Thesetermsarebasedonthevaporpressureofmercurywhenthelampsareoperating.Theeffectsofmer-curyvaporpressureonspectradistributionisshowninFigure1.1.Vapordischargelamps consist of aUV-transmitting envelopemade froma tubeof vitreous silica

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FIGURE1.1 Effectsofvaporpressureofmercuryonoutputspectradistribution.


glass sealed at both ends. The envelope is filled with mercury and an inert gas.Argon,themostcommonfiller,hasionizationenergyof15.8eV,whereasthelowestactivatedmetastablestateisat11.6eV(MasscheleinandRice,2002).

LPMlampsareoperatedatnominaltotalgaspressuresof102103Pa,whichcor-respondstothevaporpressureofmercuryatatemperatureof40C.TheemissionspectrumofLPMisconcentratedattheresonancelinesat253.7and185nm.The253.7nmlinerepresentsaround85%ofthetotalUVintensityemittedandisdirectlyrelatedtothegermicidaleffect.Thewavelengthof253.7nmismostefficientintermsofgermicidaleffectsincephotonsareabsorbedmostbytheDNAofmicroorganismsatthisspecificwavelength.Lightwithawavelengthbelow230nmismosteffectivefor the dissociation of chemical compounds. At wavelengths of 185nm, ozone isproduced fromoxygenandorganiccompoundscanbeoxidized(Voronov,2007).Thephotonswith thewavelengthof185nmareresponsibleforozoneproduction,andthecombinationofbothwavelengthsisaveryeffectivemeansforphotochemi-calairtreatment.Theratiooflightat185nmtolightat253.7nmvariesfrom12%to34%dependingontheoperatingcurrent,walltemperature,andinertgas.TheU.S.FDAregulationsapprovedtheuseofLPMlampsforjuiceprocessing,andtheyhavealreadybeensuccessfullycommercialized(U.S.FDA,CFRpart179,2000).

MPMlampsareoperatedatatotalgaspressureof104106Pa(MasscheleinandRice,2002).ComparedwiththeLPMlamps,thecoolestpossibletemperatureoftheMPMisabout400C,whereasitgoesupto600Candeven800Cinastableopera-tion.MPMlampsoperateinthepotentialgradientrangeof530W/cm.Theemis-sionspectrumofMPMcoverswavelengthsfromabout250nmtoalmost600nm,whichresultsfromaseriesofemissionsintheUVandinthevisiblerange.MPMlampsarenotconsideredtobeusefulfor targetedgermicidal treatment;however,theirstrongUVradiationfluxresultsinhighpenetrationdepth.Byvaryingthegasfilling,doping,andthequartzmaterial,thespectrumaswellastheradiationfluxoftheUVlampscanbevariedandmatchedtosuitspecificfoodprocessingapplica-tions,especiallyforoxidationorphotodegradation.

Recently,LPHOamalgamlampsthatcontainamercuryamalgamwasdevelopedand incorporated intodisinfection applications; however,LPMandMPMare thedominantsourcesforUVdisinfectiontreatment.

1.2.1.2 EnvironmentalImpactThe potential mercury exposure due to lamp sleeve breakage is a health concern.Breakageoflampscanoccurwhenlampsareinoperationandduringmaintenance.ThemercurycontainedwithinaUVlampisisolatedfromexposurebythelampenve-lopeandsurroundinglampsleeve.Forthemercurytobereleased,boththelampandlamp sleeve must break. The mercury content in a single UV lamp used for watertreatment typically ranges from 0.005 to 0.4g (5400mg). LPM lamps have lessmercury (550mg/lamp)comparedwithLPHO(26150mg/lamp)andMPMlamps(200400mg/lamp).TheEPAestablishedamaximumcontaminantlevel(MCL)formercuryat0.002mg/L.TheEPAhasfoundmercurytopotentiallycausekidneydam-agefromshort-termexposuresatlevelsabovethe0.002mg/LMCL(EPA,1995).Theconcernovertheimpactofmercuryreleaseintothefoodplantenvironmentstimulatedthedevelopmentandvalidationoflampswithmercury-freespecialtechnologies.


1.2.1.3 PulsedLampsTheefficacyofpulsedflashlamps(PL)ispotentiallygreaterthancontinuoussourcesduetohighintensityandbroaderspectrum.PLtechnologiesarepromisingduetotheirinstantstart,highintensity,androbustpackagingwithnomercuryinthelamp,butmore research is needed to establish them for fruit treatment applications. Inthistechnology,alternatingcurrentisstoredinacapacitorandenergyisdischargedthroughahigh-speedswitchtoformapulseofintenseemissionoflightwithinabout100ms.Theemissionissimilar inwavelengthcompositiontothesolar light.TheUVpulseddevicescandeliverhigh-intensityUV,whichcanbothpenetrateopaqueliquidsbetterthanmercurylampsandprovideenhancedtreatmentrates.Figure1.2shows the normalized spectra of these three UV sourcesLPM, MPM, and PL.IndividualspectraarenotcomparableonaUVintensitybasisbutarecomparableon a spectral basis with reference to which wavelengths dominate the respectivewavelengthoutputs.

Table1.1providesasummaryofsomeof thebasiccharacteristicsofcommonUVsources incommercialuseandunderdevelopment thatcanbeusedforcom-parison purposes. It is evident that no single lamp technology will represent thebestsourceforallfoodapplications.However,situation-specificrequirementsmaydictateaclearadvantageforagivenprocesstechnology.ForUVreactorscontainingLPMorLPHOmercurylamps,UVabsorbanceandtransmittanceat253.7nmareimportantdesignparameters.However,forbroadbandUVlamps,suchasMPMorPLUVlamps, it is important tomeasurethefullscanofabsorbanceortransmit-tanceinthegermicidalregionfrom200to400nm.LampswithspecialtechnologiessuchasPLUVandELarepromisingduetothedifferentspectralbandsorspecificwavelengthsthattheycanprovidewithregardtoeffectsonqualityattributes.Theyalsohaveinstantstartandrobustpackagingwithnomercuryinthelamp.However,moreresearchisneededtoestablishtheirsuitabilityforfruitprocessingapplications.

2000.000

0.002

0.004

0.006

0.008

0.010

Nor

mal

ized

spec

trum

0.012

0.014

0.016

0.018

0.020

PL lamp

MPM lamp

LPM lamp210 220 230 240 250

Wavelength (nm)260 270 280 290 300

FIGURE1.2 Comparisonofspectrumsofcontinuous(LPMandMPM)lampsandPLUVsources.


1.2.1.4 LightEmittingDiodesInrecentyears,UV-LEDshavebeendevelopedwiththefollowingadvantages:lowcost, energyefficiency, long life, easycontrolof emission, and no production ofmercury waste. The wavelength of the commercial UV-LED is around UV-Arange(315400nm)andenablesnewapplicationsinexistingmarketsaswellasopennewareas.AnLEDisasemiconductordevicethatemitslightwhencarriersofdif-ferentpolarities(electronandholes)combinegeneratingaphoton.Thewavelengthof thephotondependson theenergydifference thecarriersovercomeinorder tocombine.AnexampleofaUV-LEDsystemthatoperatesbetween210and365nmistheoneformedbyaluminumnitride(AIN),galliumnitride(GaN),andintermedi-atealloys.Currently,UV-LEDsarecommerciallyavailable inresearchgradeandlimitedquantitiesandtheirlifetimesreachtheorderof200h.Itisverylikelythatinthenearfuture,manyapplicationsthatmakeuseofmercurylampstodaywillbecarriedoutbyUV-LEDs.

1.2.2 UVLightProPagation

UVlightemittedfromtheatomsandionswithinthegasdischargeofaUVsourcewillpropagateawayfromthoseatomsandions.AsUVlightpropagates,itinteractswiththematerialsitencountersthroughabsorption,reflection,refraction,andscat-tering.EachofthesephenomenainfluencestheintensityandwavelengthoftheUVlightreachingthebacteriaorchemicalcompoundonthesurfaceorintheliquid.

Absorption(A)oflightisthetransformationofenergyoflightphotonstootherformsofenergyasittravelsthroughasubstance.Reflection(R)isthechangeinthedirectionofpropagationexperiencedbylightdeflectedbyaninterface.Scatteringis the phenomenon that includes any process that deflects electromagnetic radia-tionfromastraightpaththroughanabsorberwhenphotonsinteractwithaparticle.

TABLE1.1ComparisonofEfficiencyCharacteristicsofContinuousandPulsedUVSources

UVSource

ElectricalEfficiency

(%)

UVEfficiency

(%)

UVIntensity(W/cm2)

LampSurfaceT

(C)Lifetime,Month

OutputSpectrum

LPM 50 38 0.0010.01 40 1824 Monochromatic253.7nm

Excimer 1025 1030 0.050.5 Ambient 13 Monochromaticselectable

MPM 1530 12 12 4001,000 0.5 Polychromatic200400nm

Flashxenon 4550 9 600 1,00010,000

1 Polychromatic1001000nm

Surfacedischarge

1520 17 30,000 NA NA Polychromatic200800nm


Thescatteringphenomenonplaysanimportantroleindisinfectingfoodliquidscon-tainingparticles.Experimentalmeasurementsareusuallymadeintermsoftrans-mittanceofasubstance(T)or(UVT),whichisdefinedastheratioofthetransmittedtotheincidentlightirradiance.AconvenientwayofpresentinginformationaboutUVTofmaterialsistogivethevaluesoftheirabsorptioncoefficientatvariouswave-lengths,overagivendepth(e.g.,1cm).Knowingthis,thetransmittanceforanypar-ticulardepthandthedepthoftheliquidthatwillabsorb90%oftheenergyat253.7nmcan be calculated. Other important terms to characterize UV light treatments infruitprocessingarefluence rateandfluence.Fluencerateisthetotalradiantpowerincidentfromalldirectionsontoaninfinitesimallysmallsphereofcross-sectionalareadA,dividedbydA(BoltonandLinden,2003).Fluenceisdefinedastheflu-enceratemultipliedbytheexposuretime.ThetermUV doseshouldbeavoidedasasynonymoffluencebecausedoserefersinothercontextstoabsorbedenergy,butonlyasmallfractionofallincidentUVlightisabsorbedbymicroorganisms(BoltonandLinden,2003).InthecaseofPL,fluenceisdeterminedasenergyperpulsemul-tipliedbythenumberofpulses.Theabsorbedfluenceindicatesthatradiantenergyisavailablefordrivingthesolutionreaction.However,whenUVlightisabsorbedbysolution,itisnolongeravailableforinactivatingthemicroorganisms.Theremaininginteractions,includingreflection,refraction,andscattering,changethedirectionofUVlight,butthelightisstillavailableforinactivation.TheradiantenergydeliveredtothemoleculeormicroorganismiscalledtheeffectiveordeliveredgermicidalUVdose.Microbialinactivationdependsprimarilyontheeffectivedose.TheformulasforcalculationsofthecriticalUVprocessparametersareavailableintheliterature(Koutchmaetal.,2008).

1.2.3 BaSicPrinciPLeSofPhotochemiStry

Photochemical reactions proceed as a direct result of radiation energy (photons)beingintroducedtoasystem.InviewofthewavelengthsusedinmostUV-lighttreatments, the molecules (A) are primarily affected by energy absorption thatresultsinphotochemicalreactions.Inthegeneralcase,theprocessmaybeviewedas

A h A Products+ ++v (1.1)

Thefirststepinthisreactionistheabsorbanceofaphotonbyareactantmolecule(A),leadingtotheproductionofanelectronicallyexcitedintermediate.Theexcitedstatecanbeforaperiodof1010108sinwhichtheenergyoftheelectronsisincreasedbytheamountofphotonenergy.Undersomeconditions,theintermediatemayundergoachemicalchangetoyieldproductsthatarerelativelystable.Foraphotochemicalreactiontoproceed,photonsmusthavesufficientenergytopromotethereactiontobreakorformabondandphotonenergymustbeabsorbedtopromotereactions.ThebondenergiesofinterestaregenerallycoincidentwithphotonenergiesintheUVportionofthespectrum.Inparticular,radiationwithwavelengthlessthanapproxi-mately320nmappearstobesufficientlyenergetictopromotephotochemicalreac-tionsinbiomolecules.Theextentofchemicalreactiondependsuponthequantumyieldandfluenceofincidentphotons.Aquantumyieldisaratioofabsorbedphotons


thatcauseachemicalchangetothetotalabsorbedphotons.UVlightat253.7nmhasaradiantenergyof(472.27kJ/Einstein)112.8kcal/Einstein(oneEinsteinrepresentsonemoleofphotons).Itistheoreticallypossiblefor253.7nmlighttoaffecttheOH,CC,CH,CN,HN,andSSbondsifitsabsorbed.

1.3 UVLIGHTCONTROLMEASURESINFRUITPROCESSINGFACILITIES

Duringthemanufacturingprocess,fruitscanbeexposedtomicrobiologicalcross-contaminationfromsurfaces,water,andtheair,whichcancausetheirspoilageandraisesafetyissues.Thetraditionalapproachtocontrollingsuchcontaminationhasbeentotargetspecificsiteswithinthemanufacturingenvironmentwithcleaninganddis-infectionregimes.Sanitation,disinfection,andoxidationwithUVlightisaversatile,environmental-friendlytechnology,whichcanbeusedinfruitprocessingfacilitiesforthetreatmentofair,surfaces,andwatertoreducemicrobialcontaminationindifferentunitoperationsofplantfoodsproductionthatarebecomingmoreandmorepopular.

1.3.1 airtreatment

Clean,freshairisthebasisoftheindustrialproductionoffoodproductsofplantorigin.Microorganismsintheair,suchasviruses,bacteria,yeasts,andfungi,cancontami-naterawmaterialsandintermediateproductsandspoilfinishedproductsduringtheirprocessingandpackaging.LPMsourcesareusedverysuccessfullyintheseapplica-tions,fordisinfectioninairintakeductingandstoreroomsandtoensureairofverylowgermcontentinproductionareas.Short-waveUVradiationat185nmproducesozonefromtheoxygen in theambientairso that this isactivatedfor theoxidationprocess.UVoxidationbreaksdownpollutantsintheexhaustair.Forprovidingcleanairinsensitivemanufacturingfoodfacilities,acombinationoffiltersandUVlighthasbeenrecommended.Basically,twoapplicationsofUVarebecomingcommon.Inone,themovingairstreamisdisinfectedinmuchthesamemanneraswithawatersystem.Intheotherapplication,stationarycomponentsofthesystemsuchasairconditioningcoils,drainpans,andfilter surfacesareexposed tohelppreventmoldandbacteriagrowthortodisinfectthefiltertoaidinhandling.TheUVTinairishigherthanthatinwater,and,therefore,thenumberoflampsrequiredinalargeductisquitereason-able. Common airborne virus and bacteria are readily deactivated with UV. Fungi(moldsandspores)requiremuchhigherdoses.Inthemovingairstream,highwattagelampsareused,usuallywithoutaquartzsleeve.UVlampfixturesareplacedinsuchamannerastocompletelyirradiatesurfaceswherebacteriaandmoldmightcollectandgrow.Mathematicalmodelingsoftwareandbioassaytestinghavebeendevelopedtoallowefficientdesignandvalidationofthesesystems(KowalskiandBahnfleth,2002).LowoperatingcostsandreasonableequipmentcostscanmakeUVverycosteffective.

1.3.2 Watertreatment

Controlofmicroorganismsinindustrialprocesswatersisoftennecessarytomain-tainqualityoftheproductorprocess.Thefruitindustryisalarge-volumeconsumer


ofwater,andthepotentialforreuseorrecyclingoffruitprocessingwaterrepresentsanattractiveeconomicbenefittotheindustry.AcombinationofUVlightandozonehasapowerfuloxidizingactiontoreducemicrobialloadandtheorganiccontentofwatertoverylowlevels.

1.3.3 nonfoodandfoodcontactSUrfacediSinfection

UVlight isaneconomicalsteptowardimprovedhygienecontrolmeasures in thefoodindustry.Moldandbiofilmscandeveloponnonfoodsurfaces(ceilings,walls,floors)andequipmentincludingtanksandvats,coolingcoils,andfoodcontactsur-facesofequipmentsuchascuttingequipmentandconveyorbelts(Kowalski,2006).Ingeneral,standardcleaninganddisinfectionproceduresareadequate tocontaintheseproblems,butalternativesareavailable,includingantimicrobialcoatingslikecopperandTiO2.UVirradiationoffoodprocessingequipmentandsurfaces,coolingcoildisinfectionsystems,wholeareaUVdisinfection,andafter-hoursirradiationofroomswhenpersonnelarenotpresentareallviablecontroloptionsformaintain-inghighlevelsofsanitationanddisinfectioninfoodindustryfacilities(KowalskiandDunn,2002).UVlightkillsupto99.9%oftotalgermsonconveyorbeltsfortransportingfruitsandvegetables.

1.3.4 Packaging

The packaging technologies play an important role in extending the shelf life offruits.UVlightmightbeappliedaspre-orpostpackagingtechnologytoreducethemicrobialspoilage.Asaprepackagingcontrolmeasure,UVtreatmentofpackagingin fruitfillingplants, for example, for lids, cups, sealing, andpackaging foils fordrinksandbeverages,helpstoextendtheshelflifeoffruitstuff.WhenusingcUVand PL as postpackaging treatment for packaged fruits, the considerations abouttransparencyarereferredtothepackagingmaterials.Forexample,materialssuchasglass,polystyrene,andPET,whichallowvisible light topenetrate through thecontainer,arenottransparenttotheUVwavelengthsthatareessentialformicrobialinactivation, and therefore, they are not suitable for cUV and PL treatments. Ontheotherhand,polymerssuchaspolyethylene,polypropylene,polybutylene,EVA,nylon, Aclar, and EVOH transmit UV light and hence meet the requirements forPLTverywell(Anonymous,2000).Inaddition,ink-printedlabelsordrawingscouldinterferewiththelightabsorptionofthetreateditemandshouldbeavoidedonthesurfaceofpackagingmaterials.Besidestheintrinsictransparencyofthematerial,forthesuccessofaUVprocessitisverycriticalthattheconditionoftheitemtobetreatedissuitableforthepenetrationofthelight.Thismeansthattheproductsurfaceshouldbesmooth,clear,andwithout roughness,pores,andgrooves,whichcouldshadowthemicrobialcells fromthe light,causing lesscomplete lightdiffusionandthusreducingprocesseffectiveness;forthesamereason,theitemtobetreatedshouldbecleanandfreeofcontaminatingparticulates.Inaddition,itemsthathaveacomplexgeometrycouldhaveareashiddenfromthelightandcouldrequireamoreaccuratedesignofthetreatmentchamberinorderforthelightpulsestoreacheachpointoftheproductsurface.


1.3.5 freShfrUitandcUtfrUitSUrfaceStreatment

CUVandPLtreatmentsresultinvariouslevelsofinactivationofspoilageandpatho-genic microflora on the surface of a wide variety of solid foods. ComprehensivereviewsoftheliteratureinthisfieldhavebeencompiledbytheU.S.FDA(2000)andbyWoodlingandMoraru(2005).Thevariabilityoftheresults(a2-to8-logreductionwasgenerallyreported)ismostlikelyduetothedifferentchallengemicroorganismsusedinvariousstudies,theintensityofthetreatment,andthedifferentpropertiesofthetreatedsubstrates.WoodlingandMoraru(2005)demonstratedthattheefficacyof PL is affected by substrate properties such as topography and hydrophobicity,whichaffectboththedistributionofmicrobialcellsonthesubstratesurfaceandtheinteractionbetweenlightandthesubstrate(i.e.,reflectionandabsorptionoflight).Surfacedisinfectionoffreshandcutfruitproductsisabasisforlongershelflife.IndesigningaPLtreatmentforfruititems,bothsource(lightwavelength,energyden-sity,durationandnumberofthepulses,intervalbetweenpulses)andtarget(prod-ucttransparency,color,size,smoothness,andcleanlinessofsurface)parametersarecriticalforprocessoptimization,inordertomaximizetheeffectivenessofproductmicrobial inactivationand tominimizeproduct alteration.SuchalterationcanbemainlydeterminedbyanexcessiveincreaseintemperaturecausingthermaldamagetofruitsandalsobyanexcessivecontentofUV-Clight,whichcouldresultinsomeundesiredphotochemicaldamagetofruititselfortopackagingmaterials.Table1.2summarizescurrentandfutureapplicationsofcUVandPLavailablesourcesinfruitprocessingforair,surface,water,andlowUVTfruitdrinksandbeverages.

1.4 UVTREATMENTOFWHOLEFRESHFRUITS

1.4.1 antimicroBiaLeffect

Traditionally UV-light applications for treatments of whole fruits and vegetableswerefocusedonthedisinfectionrolewiththeobjectivetoextendtheshelflifeasnaturallyoccurringmicrofloramaypresentonthesurfaceofrawproducebothofnonpathogenicorspoilageandpathogenicnature(Table1.3).

TABLE1.2ApplicationofUVLightSourcesasaControlMeasureinFruitProcessing

UVSource

ReportedApplications

ProcessedWater Air Surfaces LowUVTJuices

LPM X X X X

MPM X X

Excimerlasers X X X

Pulsed X X

LED X X X


Duringstorage, fruitsundergobiochemicalandphysiologicalchanges thatcanresult in loss of nutrients, color changes, and tissue disruption. Along with theseundesirable changes, crops become more susceptible to pathogenic decay, whichincreasesthepossibilityofillnessincidencesandalsocauseslargeeconomiclosses.

Enhancedshelf lifeofUV-treatedfruitscanbeassociatedwiththegermicidaleffectonpathogensthatmaybepresentonthesurfaceofthecrops.However,theUVtreatmentrequiresthatthewholesurfaceoftheobjectisexposedtotheUVlightforatimesufficientforanymicroorganismspresenttoaccumulatealethaldose.ThisalsomeansthatthetopographyofthesurfacedeterminestheefficacyofUVtreat-mentandpresentsitslimitationduetoshieldingeffects.TheimportanceofthefruitpositioningduringtheUV-CexposureofstrawberrieswasreportedbyStevensetal.(2005).TheauthorsfoundthatirradiationofthestemendsofthefruitsresultedinlowerdecayduringsubsequentstorageincomparisonwiththefruitsexposingonlyoneortwodifferentsidestoUV-Clight.

SeveralstudieshaveshownthatUVprocessingoffreshproduceiseffectiveinthereductionofpathogenicbacterialpopulation.Forinstance,Yaunetal.(2004)inocu-latedthesurfaceofRedDeliciousapples,leaflettuce,andtomatoeswithculturesofSalmonella spp.orEscherichia coli O157:H7.UV-C(253.7nm)appliedtoapplesinoculatedwithE. coli O157:H7 resulted in thehighest log reductionofapproxi-mately3.3 logsat240W/m2.Lower log reductionswereseenon tomatoes inocu-latedwithSalmonella spp.(2.19logs)andgreenleaf lettuceinoculatedwithbothSalmonella spp.andE. coli O157:H7(2.65and2.79logs,respectively).PLUVlight

TABLE1.3FreshProduceandTypicalMicrofloraPresentontheSurface

Commodity Microflora Reference

Fruits(ingeneral) Fungi:B. cinerea,Aspergillus niger; Martin-Bellosoetal.(2006)

Yeasts:Canidia,Cryptococcus,Fabospora,Kluyveromyces,Pichia,Saccharomyces,andZygosaccharomyces;

Bacteria:Shigellaspp.

Carrot B. cinerea Mercieretal.(1993)

Lettuce Enterobacter, Erwinia, Escherichia, Leuconostoc, Pantoea, Pseudomonas, Rahnela, Salmonella, Serratia,andYersinia

Allendeetal.(2006)

Tomato B. cinerea Charlesetal.(2008)

Apple E. coliO157:H7 Martin-Bellosoetal.(2006)

Raspberry Cyclospora cayetanensis Martin-Bellosoetal.(2006)

Strawberry Campylobacter jejuni Martin-Bellosoetal.(2006),Erkanetal.(2008),Pomboetal.(2011)

B. cinerea

Watermelon Salmonellaspp.,Shigellaspp. Martin-Bellosoetal.(2006)

Cantaloupe Campylobacter jejuni Martin-Bellosoetal.(2006)

Pineapple E. coli O157:H7,Salmonella StrawnandDanyluk(2010)


wasalsoappliedtoreducethepopulationofpathogenicbacteriaonthesurfaceoffruits.Forinstance,BialkaandDemirci(2007,2008)exposedblueberriesinoculatedwithE. coliO157:H7andSalmonellatothePL(XenonCorp.)emittinginarangefrom100 to1100nm for 5, 10, 30, 45, and60s.The authors reported reductionsbetween1.1and4.3log10CFU/gofE. coliO157:H7and1.1and2.9log10CFU/gofSalmonella.Duetothehigh-intensitynatureofthePLsource,substantialincreaseinthetemperaturewasobservedduringfruitprocessingthatcouldcontributetothemicrobialreduction.TheimpactofthePLtreatmentonthenutrientsoftreatedcropshasnotbeenstudiedyet.

Thedeteriorationofmanyfreshfruitscanbecausedbyfungi,whichgiverisetovariousinfectionsonharvestedplantproduce.Forexample,Monilinia fructicolaisthemaincauseofbrownrotinpeaches,apricots,nectarines,andplums.Stevensetal.(1998)revealedthatUVtreatmentcanreducethefungalpopulationonpeaches.ThesurfacesofpeacheswereinoculatedwithsporesoftheM. fructicolaandthenfruitsweresubjectedtotheUVlight.AtUVfluenceof4.8kJ/m2,adecreaseingrowthofM. fructicolabyapproximatelyoneorderofmagnitudewasobserved.AnotherstudyperformedbyStevensetal.(2005)hasshownthatUV-C(253.7nm)treatmentat7.5and1.3kJ/m2resultedinhigherresistancetobitterrot(Colletotrichum gloeospori-oides),brownrot(M. fructicola),andgreenmold(Penicillium digitatum)inapples,peaches, and tangerines. Gonzlez-Aguilar et al. (2001, 2007) demonstrated thatexposure toUV-C light in the rangeof250280nmat4.93kJ/m2 lowered fungaldecayofmangofruitsstoredfor18daysat25Cby60%.Significantlylowerinci-denceofdecaywasalsoobservedafterUV-Ctreatmentinkumquatfruitandbitterorange(Citrus aurantium)inoculatedwithP. digitatum(Rodovetal.,1992;Arcasetal.,2000).InthecaseofpapayafruitsinoculatedwithColletotrichum gloeospori-oides,noneoftheUV-C(253.7nm)treatments(0.22.4kJ/m2)waseffectiveagainstanthracnosefungalsporulation(Ciaetal.,2007).Anotherfungus,Botrytis cinerea,isthemaincauseofgraymoldrotinmanycrops.ExposuretotheUV-Clightwiththepeak at thewavelengthof253.7nm reduced theB. cinerea growth in carrots(Mercier et al., 1993), tomatoes atUVfluenceof3.7kJ/m2 (Charles et al., 2008),pepperfruitsatUVfluenceof7kJ/m2(Vicenteetal.,2005),andstrawberries(Erkanet al., 2008; Pombo et al., 2011). Erkan et al. (2008) reported that in UV-treatedstrawberriesatfluencelevelsof0.43,2.15,and4.30kJ/m2,after20daysofstorageat10Cthepercentageoffungaldecaywas49.6,29.6,and27.98,respectively,whileincontrolfruitsthedecayreached89.98%.SimilarobservationshavebeenreportedbyPomboetal.(2011)whoinoculatedStrawberrieswithB. cinerea8hafterUV-Ctreatmentatthedoseof4.1kJ/m2.ThereductionoffungalgrowthwasfoundandcanbeattributedtotheplantdefensemechanismagainstpathogensinducedbyUVlight.

1.4.2 PLantantimicroBiaLdefenSemechaniSmtriggeredByUV

ExposuretoUVatverylowdosesoverhoursorevendaystriggersaseriesofbio-chemicaleventswithintheplanttissue.Thetermhormesishasbeenappliedtothistype of UV treatment. According to Shama (2007), hormesis involves the use ofsmalldosesofpotentiallyharmfulagentsdirectedagainstalivingorganismorliv-ing tissue to elicit a beneficial or protective response. Hormetic UV treatment is


distinguishedfromconventionalUVtreatment.Inconventionaltreatment,theUVis directed toward microorganisms that are present on the surfaces of an object,whereas in thecaseofhormeticUVtreatment, theobject itself isexposed to theincidentUV.Thepurposeofthetreatmentistoelicitanantimicrobialresponseinthefruittissue.BothtypesofUVtreatmentemploythesamewavelengths;however,forhormetictreatmentsonlylowUVdosesareapplied(ShamaandAlderson,2005).TheplantdefensemechanismthatistriggeredbythehormeticUVdoseisnotyetfully known and understood. Figure 1.3 schematically presents some of the bio-chemicalresponsesofplantmembranethatwererecentlyreported.ItwasfoundthatUV-ChormetictreatmentatUVfluencesintherangeof0.44.3kJ/m2stimulatestheactivityofseveralgroupsofenzymesthatplaydifferentrolesinplantantimicro-bialdefenseactions.Thisincludes(1)enzymesofperoxidasesandreductasesthatareresponsiblefortheoxidativeburstandformationofligninpolymersgeneratingstructural barriers against invading pathogens; (2) glucanases and chitinases thatexhibitlyticactivitiestowardmajorfungalcellwallcomponents;and(3)l-phenyl-alanine ammonia lyase (PAL)involved in biosynthesis of phenolics, which arecharacterizedbyantioxidantandantimicrobialactivities(Erkanetal.,2008;Pomboetal.,2011).

ItwasfoundthatthehigheraccumulationofrishitininUV-C-treated(253.7nm,3.7kJ/m2)tomatofruitswaspositivelycorrelatedwithenhancedresistanceagainstgraymoldrot(Charlesetal.,2008).Inaddition,thehormeticUVtreatmentsresultin protective effects against microorganisms throughout the entire tissue ratherthanatitssurfaceonly.Stevensetal.(1999)showedthatsweetpotatoesinoculatedwithsporesofFusariumsolaniatadepthof12mmbelowthesurfacecouldbesuc-cessfullyprotectedfrominfectionfollowinghormeticUVtreatment.TheresearchattentionwasalsofocusedoncitrusfruitsandinfruitswheretheenhancementofresistancetophytopathogenssuchasP. digitatumhasbeenattributedtoaccumula-tionofthephytoalexinsscoparone.Asexample,Ben-Yehoshuaetal.(1992)reportedthat UV illumination of lemon reduced susceptibility to P. digitatu, which wasdirectlyrelatedtothelevelofscoparoneinthetreatedfruit.

1.4.3 effectSonBioactiVecomPoUndS

ThereportsrelatedtoUVhormesisinfreshproduceshowedthatduetotheinduc-tionofplantdefensemechanismsaccumulationofthephytochemicalsintheplantcellscanoccur.Theirantimicrobialandantioxidantpropertiesarehighlydesirableas they can contribute to delaying the onset of ripening and consequently reduc-ingeconomiclossesduetospoilage.Moreover, theformationofbioactivepheno-liccompoundssuchasphenolicacidsandflavonoidsincreasesthenutritionalvalueof UV-treated commodities. Phenolic acids and flavonoids are characterized byessentialhealthpromotingpropertiessuchasantiinflammatory,antihistaminic,andantitumoractivities.

Severalstudiesreportedincreaseinandbettermaintenanceofphenolicsandfla-vonoidcompoundsincropsprocessedwiththeUVlight.Thetypeofthepolyphe-nolsaswellastheiraccumulationandbettermaintenanceduringstoragewashighlydependenton thecropcommodityandappliedUVdose.Gonzlez-Aguilaret al.

15U

ltraviolet Ligh

t for Pro

cessing Fru

its and

Fruit Pro

du

cts

Cellmembrane

Accumulationof ROS (reactiveoxygen species)

Active species:ABACATCHSGSHJAMDARPALPMEPODSOD

Arabic acidCatalaseChalcone synthaseGlutathioneJasmonic acidMonodehydroascorbate reductasePhenylalanine ammonia lyasePectin methylesterasePolyphenol oxidaseSuperoxide dismutase

Eects

UVlight

O

O

H

O

OH

Presence of ROS induce activity of:- Antioxidant enzymes: SOD, CAT, POD, MDAR- GSH-Maintains cellular redox status

O2SOD

H2O2

H H

H OHO2

H2O2

Hydroxyl radicalSuperoxide radicalHydrogen peroxide

ABA Biosynthesis of JA

Activation of defensive gene expressions

Antioxidants

- Enzymatic antioxidant system - Phytoalexins

- Reduction of cell wall degrading enzymes (PME, cellulase, xylanase)

- Cell wall strengthening by formation of lignin polymers (peroxidases)

- Flavonoids- Chitinases and reductases (degrade fungal; cell walls)- Quinones (PPO)

- Phenolic compounds; phenolic acids, avonoids, anthocyanins (PAL, CHS)- Carotenoids- Lignans- Vitamin C

Hor

met

ic re

spon

se

Antimicrobialspecies

Cell wallreinforcement

H

H

FIGURE1.3 SchematicrepresentationofbiochemicalresponsesintheplanttissuemembranetriggeredbythehormeticUVtreatment.Enzymesthatplaycrucialrolesintheplantdefensivemechanismareshown.


(2001, 2007) found higher levels of total phenols and polyamine compoundsinmangoesirradiatedwithUV-Cat4.93kJ/m2thaninfruitsexposedto2.46or9.86kJ/m2. In other studies, authors also observed induction of polyamine com-poundsinpeachesafterUV-Cexposure(Gonzlez-Aguilaretal.,2004).Theaccu-mulationofpolyaminesincropsmightbebeneficialinincreasingtheresistanceoffruittissuetodeteriorationandchillinginjury.Inparticular,exposureofcitrusfruitstoUVlightwasfoundtobeadvantageousin termsof theformationofflavonols.Forexample,Arcasetal.(2000)notedthatduetoUV-Cexposureat0.72kJ/m2,thecontentofnaringinandtangeretininthepeelofCitrus aurantiumfruitsincreasedby7%and55%,respectively.Table1.4summarizesresultsoftherecentstudiesofUVtreatmentsoffruitswhereUV-relatedenhancementinthecontentofthebioactivecompoundswasobserved.

1.4.4 StorageofPoSt-UV-treatedfrUitS

Thestorageconditions,suchastemperatureormodifiedatmosphere,canadverselyaffectthelevelsofUV-formedphytochemicals.Forinstance,Vicenteetal.(2005)observedincreaseintheantioxidantcapacityinpepperfruitsimmediatelyaftertheUV-Cexposure.Duringsubsequentstorageat10C,theantioxidantcapacityofpepperdecreased.However,after18daysofstorage,UV-treatedfruitsshowedmoreanti-oxidantsthancontrolfruit.Allendeetal.(2007)studiedtheeffectofthemodifiedatmosphere packaging on the quality of the UV-treated strawberries. The resultsrevealedthatstrawberriesstoredundersuperatmosphericO2andCO2-enrichedcon-centrationsat2Cshowedlowertotalphenoliccontentsafter5daysandavitaminCreductionafter12dayswhencomparedwiththefruitsthatwerekeptintheair.

1.4.5 formationofVitamind

MushroomsaretheonlyplantsourceofvitaminD2becausetheycontainahighamountofergosterol thatcanbeconvertedtovitaminD2afterexposuretoUVirradiation(Mauetal.,1998;JasingheandPerera,2005).Allthreec-UVbands(UV-A,UV-B,andUV-C)wereapplied for thepostharvest treatmentof ediblemushrooms.Mauetal.(1998)foundUV-B(310nm)lightmoreeffectivethanUV-C(253.7nm)incon-versionofergosterol tovitaminD2incommon(Agaricus bisporus)mushrooms.Itwasfoundthatduetoexposurefor2htoUV-B(9.86kJ/m2)andUV-C(14.71kJ/m2)light, the vitamin D2 content in common mushrooms increased from 2.20g/g ofdryweight to12.48and7.30g/g, respectively.UV-Birradiationalsoaffected thevitaminD2formationinShiitakeandStrawmushrooms,withtheincreaseratesof2.15and1.86g/h,respectively.However,Jasingheetal.(2006)reportedthatUV-Cexposure(23.0kJ/m2)for2hresultedinhigheryieldsofvitaminD2inalltreatedkindsofmushrooms,Shiitake,Oyster,Abalone,andButton,whencomparedwiththeUV-A(25.2kJ/m2).Itisknownthattheincreaseinphenolcontentmightbeaccompaniedbytissuebrowning.InthecaseoftreatmentsofShiitakeandStrawmushrooms(Mauetal.,1998;Jiangetal.,2010),thechangesincolorwerenotobserved.However,Mauetal.(1998)observedthatbothUV-BandUV-Ctreatmentsfor2hresultedindiscol-orationofcommonmushrooms.Therefore,theoptimalconditionsforUVprocessing


TABLE1.4ExamplesofUVTreatmentsofFruitswiththeAccumulationofDifferentPhytochemicals

CommodityAffectedBioactive

CompoundsNumber/UVLamp/

PowerFluence Reference

Strawberries Increaseinantioxidantcapacityandtotalphenoliccontent

3/LPM/8W Erkanetal.(2008)

2.15kJ/m2

Blueberries Increaseinantioxidantcapacity,totalphenolicandanthocyaninscontent

15/LPM/8W, Wangetal.(2009)

2.15and4.30kJ/m2

Increasedtotalphenoliccontent 1UV-Bfluorescentlamp(305310nm)

Eichholzetal.(2011)

0.54kJ/m2

Grapeberries Increasedresveratrolderivativescontent

1/LPM/N/A Cantosetal.(2000)

0.01kJ/m2

3/UV-Blamp(340nm)/80W

Cantosetal.(2000)

N/A/LPM/510W Gonzlez-Barrioetal.(2009)

Apples Enhancedanthocyaninscontent UV-Blamp(320nm) Ubietal.(2006)

Peaches Enhancedcontentofpolyaminecompounds

N/A/LPM/15W Gonzalez-Aguilaretal.(2004)8.22W/m2

Mangoes Enhancedcontentsofphenolsandpolyaminecompounds(spermidine,putrescine,spermine)

N/A/LPM/15W Gonzlez-Aguilaretal.(2001,2007)8.22W/m2

Kumquat Enhancedphytoalexinscoparonecontent

LPM Rodovetal.(1992)

0.21.5kJ/m2

Orange Enhancedphytoalexinscoparonecontent

LPM Rodovetal.(1992)

1.59.0kJ/m2

Bitterorange Enhancedflavonolscontent(tangeretin)

1/LPM/N/A Arcasetal.(2000)

0.1W/m2

Limon Increasedtotalphenoliccontent 6/UV-Blamp(280400nm)/N/A

Interdonatoetal.(2011)

0.052and0.077kJ/m2

Pepperfruits Increasedantioxidantcapacity 4/LPM/30W Vicenteetal.(2005)

1,3,7and14kJ/m2

Greentomatoes

Increaseintotalphenoliccontent 2/UV-Blamp(311nm)/N/A

Liuetal.(2011)

20and40kJ/m2

Onions Enhancedquercetincontent UV-A(352nm) Higashioetal.(2005)

1.84W/m2

Shiitakemushrooms

EnhancedvitaminC,totalphenolic,andtotalflavonoidslevels

N/A/LPM/20W Jiangetal.(2010)

4kJ/m2


stillneedtobedetermined.AsJasingheetal.(2006)concludedthattheirradiationof5goffreshShiitakemushroomsfor15minwithUV-AorUV-BissufficienttoobtaintherecommendedallowancesofvitaminDforadults(10g/day).

1.4.6 effectSongeneraLaPPearance

Nutritionalvalue,color,flavor,andtextureoffruitsarethemajorfactorsthatindi-cateproduct freshnessandhighly influence theconsumerschoice.Deteriorationandripeningduringstorageresultintissuedamage,discoloration,andformationofoff-flavor.UVtechnologycanbealsoprotectiveagainstthesesymptomsofsenes-cenceduetotheactivationoftheplantdefensivemechanismbythehormeticUVdoses.AccordingtoPomboetal. (2009),delayin thesofteningofplantproducecouldbeassociatedwithadecreaseintheexpressionofasetofgenesinvolvedincell-walldegradation,duringthefirsthoursafterUVtreatment.ItwasreportedthatoptimalUVtreatmentcanincreasetheshelflifeofstrawberries,apples,peaches,tomatoes,peppers,andbroccolibyreducingtherespirationrateandweight loss,retainingoverallvisualquality,delayingtheripeningandelectrolyteleakage,andmaintainingfirmness fora longer time,whencomparedwithcontrols (Luetal.,1991; Baka et al., 1999; Marquenie et al., 2002; Gonzalez-Aguilar et al., 2004;Lammertyn et al., 2004; Vicente et al., 2005; Costa et al., 2006; Allende et al.,2007;Lemoineetal.,2007;Pomboetal.,2009).Inordertoincreaseshelflife,theprocessingconditions,UVdose(kJ/m2),andemissionspectrumsshouldbeopti-mizedforagivencommodityofcrops.Lammertynetal.(2004)andAllendeetal.(2007) recommended 1.0kJ/m2 as optimal fluence for the UV-C processing ofstrawberriessinceathighertreatmentsauthorsobservedbrowninganddehydrationofthesepals.UV-Cfluencelevelsofabout45kJ/m2werefoundtohavethemostbeneficialeffectonshelflifeandqualityofmangofruits(Gonzlez-Aguilaretal.,2001,2007)andShiitakemushrooms(Jiangetal.,2010).ReportsareavailablethatapplicationofUVlightcanprotectthecolorofgreencommodities.Forinstance,Costaetal.(2006)andLemoineetal.(2007)reportedthatexposuretotheUV-Catpeakemissionof253.7nmandatfluencelevelsof78kJ/m2allowedretainingthehighestlevelsofchlorophyllandhencepreservesthegreencolorofbroccoliflorets.Similarly,UV-B(312nm)treatmentat8.8kJ/m2delayedthechlorophyllbreakdowninthebroccoliandlimepeel.Moreover,UVtreatmentresultedinreducedweightlossandshrivelingofthelimefruits(Aiamla-oretal.,2009;Srilaongetal.,2011).Aiamla-oretal.(2009)reportedthatattemptstodelaytheyellowingofbroccolibyUV-Alight(342nm)at4.5and9.0kJ/m2werenoteffective.

1.5 UVTREATMENTOFFRESH-CUTPRODUCE

Fresh-cutfruitsbecamepopularamongconsumersduetoincreasedpreferenceforminimallyprocessedfresh-likeandready-to-eatproducts.Mechanicaloperationsoffresh-cutfruitsproduction,suchaspeeling,slicing,shredding,etc.,oftenresultinenzymaticbrowning,off-flavors,texturebreakdown,andlowerresistanceoffresh-cutproducetomicrobialspoilageincomparisonwiththeunprocessedcommodities(Lemoineetal.,2007)becauseofpresenceofnaturalmicrofloraonthesurfaceof


rawcommoditiesasshowninTable1.3.Therefore,duringoperationsofcuttingandshredding,cross-contaminationmayoccur,whichmightincreasetherisksoffood-borneoutbreaks.

To improvehygieneand safetyduringmechanicalprocessing, sanitizinganddripping treatments are commonly applied. During washing and dipping steps,raw or fresh-cut material is immersed into the tap water containing sanitizingagents(chlorine,sodiumhypochlorite)toremovespoilagemicroorganisms,pesti-cideresidues,andplantdebrisfromproductsurface(Martin-Bellosoetal.,2006).Toreducetheusageofsanitizingchemicals,UVlightaloneorincombinationwithozoneoranotherpreservativeagentwasexploredasnovelprocessingalternatives.FonsecaandRushing(2006)examinedtheeffectsofUV-Clight(1.413.7kJ/m2at253.7nm)onthequalityoffresh-cutwatermeloncomparedwiththecommonsani-tizingsolutions.Dippingcubesinchlorine(40L/L)andozone(0.4L/L)wasnoteffectiveinreducingmicrobialpopulations,andcubequalitywasloweraftertheseaqueous treatments compared with UV-irradiated cubes or control. In commer-cialtrials,exposureofpackagedwatermeloncubestoUV-Cat4.1kJ/m2producedmore than 1-log reduction in microbial populations by the end of the productsshelflifewithoutaffectingjuiceleakage,color,andoverallvisualquality.HigherUVdosesneithershoweddifferencesinmicrobialpopulationsnorresultedinqual-ity deterioration (13.7kJ/m2). Spray applications of hydrogen peroxide (2%) andchlorine (40L/L)without subsequent removalofexcesswater failed to furtherdecreasemicrobialloadofcubesexposedtoUV-Clightat4.1kJ/m2.Itwascon-cludedthatwhenproperlyused,UV-Clightistheonlymethodtestedthatcouldbepotentiallyusedforsanitizingfresh-cutwatermelon.Similarly,exposureofslicedapplestoUV-Cresultedinhigher(1log)reductionofListeria innocuaATCC33090,E. coliATCC11229,andSaccharomyces cerevisiaeKE162incomparisonwithapplespretreatedwithantibrowningandsanitizingagents(1%w/vascorbicacid0.1%w/vcalciumchloride).ThecombinationofUV-Cwithantibrowningpretreatmentbetterpreservedthecolorofslicedapplesduringstorageat5Cfor7days(Gmezetal.,2010).OtherstudieshaveshownthatUV-Ctreatmentappliedalonewasefficient in thereductionof thenumberofmicrobiologicalorganismspresentonthesurfaceoffresh-cutcrops.TheexamplesofsuccessfulapplicationsofUV-ClightaregiveninTable1.5.

Similarlytorawcrops,theeffectivenessofUVtreatmentonreductionofmicro-bialdeteriorationandqualityretentionwasdefinedbythedeliveredUVdoseandoverallcharacteristicsofthesurfaceexposedtotheUVlight.Allendeetal.(2006)foundabetterpreservationofRedOakLeaflettuceirradiatedbyUV-Clightonbothsidesoftheleaves.AsoptimalconditionfortheincreasingoftheshelflifeofRedOakLeaf lettuce, theauthors recommended theUVfluenceof2.37kJ/m2.Undesirablequalitychangesoccurringathigherfluencesincludedtissuesofteningand browning. Lamikanra et al. (2005) stressed that the moment of the applica-tionofUVlightduringthefruitprocessingisanimportantfactor.Intheirstudies,theauthorsexposed thecantaloupemelon toUV-Cat254nmduringcuttingandaftercuttingofthefruits.CuttingofcantaloupemelonundertheUV-Clightwasaseffectiveaspostcuttreatmentinreductionofyeast,molds,andPseudomonasspp.populations.However,fruitcuttingduringsimultaneousexposuretoUV-Cresulted


inimprovedproductquality,thatis,reducedrancidityandrespirationrate,andalsoincreased firmness retention, when compared with postcut and control samples.BetterpreservationoffruitsprocessedduringtheUVexposurecanberelatedtothedefenseresponseofthewoundedplantenhancedbytheUV.Mechanicalinjuryoftheplanttissuesactivatestheexpressionofwound-induciblegenes.UVradiationis

TABLE1.5SummaryofStudiesoftheEffectofUV-CLightonReductionofMicroorganismsinFresh-CutProduce

Fresh-CutCommodity MicrobiologicalOrganism

Number/UVLamp/PowerFluence Reference

Watermelon Mesophilic,psychrophilic,andenterobacteria

15/LPM/36W Arts-Hernndezetal.(2010)1.6,2.8,4.8,7.2kJ/m2

Cantaloupemelon

Yeast,mold,Pseudomonasspp.,mesophilicaerobes,lacticacidbacteria

1/LPM/N/A Lamikanraetal.(2005)

0.0118kJ/m2

Apple L. innocuaATCC33090;E. coliATCC11229andSaccharomyces cerevisiaeKE162

2/LPM/15W Gmezetal.(2010)

5.60.3;8.40.5and14.10.9kJ/m2

Pear L. innocuaATCC33090,Listeria monocytogenesATCC19114D,E. coliATCC11229,andZygosaccharomyces bailiiNRRL7256

2/LPM/15W Schenketal.(2007)

15,31,35,44,56,66,79,and87kJ/m2

RedOakLeaflettuce

Enterobacter cloacae,Enterobacter asburiae,Erwinia carotovoraECC71,E. coliRecA_HB101andRecA+MC4100,Escherichia vulneris,Escherichia hermannii,Leuconostoc carnosum,Pantoea agglomerans,Pseudomonas fluorescensBiotypeGandA,Pseudomonas corrugata,Pseudomonas putidaC552,Pseudomonas tolaasii,Rahnela aquatilis,Salmonella typhimurium,Serratia ficaria,Serratia plymuthica,Serratia liquefaciens,Yersinia aldovae

15/LPM/15W Allendeetal.(2006)

1.18,2.37,7.11kJ/m2


capableofinducingtheexpressionofplantdefense-relatedproteinsthatarenormallyactivatedduringwounding.Forexample,Lamikanraetal.(2005)reportedsignifi-cantincreaseinascorbateperoxidaseenzymeactivityduringstorageofcantaloupemelonprocessedunderUV-Clight.Peroxidasesprotectplantcellsagainstoxidation.Higherlevelsofterpenoids(-cyclocitral,cis-andtrans--ionone,terpinylacetate,geranylacetone,anddihydroactinidiolide)werefoundincantaloupetissues,whichcanplayimportantrolesasphytoalexinsinthediseaseresistanceofavarietyofplantfamilies(Lamikanraetal.,2005;Beaulieu,2007).Significantincreaseinantioxida-tivecompounds,suchasphenolicsandflavonoids,wasalsoobservedbyAlothmanetal.(2009)inUV-treatedfresh-cutbanana,pineapple,andguavafruits.However,decreaseinvitaminCwasobservedinallfruits.

In termsofUVeffectsonfruitsflavor,Beaulieu(2007)andLamikanraetal.(2005) reported that fruits processedwithUV light preserved their aroma to thesameextentasnontreatedcontrolsamples.Detailedstudiesofvolatilecompoundsinthin-slicedcantaloupetissuesrevealedthatUVtreatment isnotresponsibleforthechemicaltransformationstoesterbonds,esterase,andlipasedecrease.However,Beaulieu(2007)indicatedthatimpropercutting,handling,sanitationtreatment,andstoragecanradicallyalterthedesirablevolatilearomaprofileincutcantaloupeandpotentiallyleadstodecreasedconsumeracceptance.

1.6 UVPASTEURIZATIONOFFRESHJUICES

Fresh juices are popular beverages in the worlds market. They are perceived aswholesome,nutritious, alldaybeverages.For itemssuchas juicesor juicebever-ages,minimalprocessingtechniquesareexpectedtobeusedtoretainfreshphysical,chemical,andnutritionalcharacteristicswithextendedrefrigeratedshelf life.TheU.S.FDAapprovalofUVlightasanalternativetreatmenttothermalpasteurizationoffreshjuiceproducts(U.S.FDA,2000)ledtothegrowinginterestandresearchinUVtechnology.KeyfactorsthatinfluencetheefficacyofUVtreatmentoffruitjuicesincludeopticalproperties,designofUVreactors,andUVeffectsoninactiva-tionofpathogenicandspoilageorganisms.ThereareanumberofstudiesrecentlypublishedthatexaminedUVlightnotonlyasapotentialmeansofalternativepas-teurizationbystudyingeffectsonmicroflorabutalsoitseffectsonflavor,color,andnutrientcontentoffreshjuicesandnectars(Koutchma,2009).

1.6.1 UVaBSorPtionoffreShJUiceS

Fruitjuicesarecharacterizedbyadiverserangeofchemical,physical,andopticalproperties.Chemicalcomposition,pH,dissolvedsolids(Brix),andwateractivityhavetobeconsideredashurdlesthatcanmodifytheefficacyofUVmicrobialinac-tivation.Opticalproperties(absorbanceandscattering)arethemajorfactorsimpact-ingUVlighttransmissionandconsequentlymicrobialinactivation.UVabsorbanceandtransmittanceat253.7nmareimportantparameterstodesignUVpreservationprocessusinganLPMorLPHOsource. In thecaseof thebroadbandcontinuousUVandPL,itisimportanttomeasurethespectraoftheabsorbanceortransmittanceintheUVgermicidalregionfrom200to400nm.Thejuicescanbetransparentif


10%3.5J/cm2)inthefreshlypreparedciderthaninthecommercialone.Inthecommercialfreshapplecider,UVCinducedlittlefuranatdoseslessthan3.5J/cm2.WhenfreshappleciderswereUVtreatedtoachievethe5-logreductionofE. coli,asrequiredbytheU.S.FDA,lessthan1ppbfuranwasfound. Itwasconcluded that a significant amountof furancouldbeaccumulatedif apple ciderwasovertreated.Overall, these results suggested that little furan isinduced inapplecider ifUV-Cprocessing isused for thepurposeof appleciderpasteurization.Thedestructionofd4-furanbyUV-Cindifferentsolutionsandappleciderwasalsoanalyzedinthisstudy.Therewaslittledestructionofd4-furanatadoseof0.9J/cm2whend4-furaninwater,glucose,sucrose,ascorbicacid,orappleciderwasUVtreated,butinfructosesolutions,88%ofd4-furanwasdestroyed.Inwater, lessthan10%ofd4-furanwasdestroyedevenatadoseof9J/cm2.Infruc-tosesolution,alld4-furanwasdestroyedat9J/cm2.Inadoseresponsestudy,itwasdemonstratedthatmostd4-furanwasdegradedeveninthelowdose(


ofundesirablepathogenic,nonpathogenic,andspoilagemicroorganismsonthesurfacesoffreshfruitsandfruitproductsandinjuices.Inordertoachievetherequiredmicrobialreductionalongwithcolor,texture,andflavorpreservation,optimalUVprocessingconditionsandproperUVsourcehastobefoundforagivenproduct.RecentstudiesreportedapotentialofUVlightforenhancementofhealthpromotingcompoundssuchasantioxidants,polyphenols,andflavo-noids.Moreover,UVlightcanberecommendedaseffectivemeanstocontrolmicrobial loads in theair,water,nonfood,and foodcontact surfaces in fruit-processing facilities. A variety of UV sources are commercially available orcurrently under development that can be applied for specific fruit processingpurposes,whereasLPMlampsandxenonPLarecurrentlythedominantsourcesforUVtreatmentoffruitssincetheywereapprovedbytheU.S.FDAandHealthCanada.AnumberofUV-lightcontinuousflowsystemsthatincludedannularlaminarandturbulentflowreactors,thin-filmdevices,andstaticanddynamicmixersweredevelopedandvalidatedforavarietyoffruitjuicesforpasteuriza-tionpurposes.ThecorrectUVdesigncanreducetheinterferenceoflowUVTandviscosityassociatedwithsomejuicesandthereforeimprovestheUVinac-tivationefficiency.MoreworkisneededinregardtothedesignofUVsystemscapableofdeliveringsufficientUVdosestoallpartsofthetreatedliquidwithlowUVRsuchasfruitjuices.

NumerousstudiescitedherehaveshownthebeneficialeffectsoftheUVtreatmentonthepreservationofmanyfruits,bothrawandfreshcut.However,onthebasisoftheavailableliterature,themechanismthatunderliesthehormeticresponseinfreshproduceisstillopentodebate.InresponsetotheexposureofUVlight,plantsacti-vatedifferentenzymesperoxidases,reductases,andchitinases,whichdifferintheirchemical structure and absorptive properties in UV-A, UV-B, and UV-C ranges.Therefore,plantresponsevariesdependingonappliedUVemissionspectrumandUVdose.ToimprovethestateoftheexistingknowledgeonUVprocessingoffreshproduce,furtherstudiesarenecessarythatwillmeasureandreportconditionsandparametersoftheUVtreatment,suchaslampcharacteristics,emittedwavelength,andUVfluencelevels.

TheeffectofUVlightonthequalityoffruitsrequiresfurtherstudies.DespitethefactthatUVispurelyanonthermaltreatment,thepossibleundesirableeffectsmay include damage to vitamins and proteins, destruction of the antioxidants,changesincolor,andformationofoff-flavorsandaromasdependingonUVspectraandapplieddose. Inaddition, theeffectsofUV lighton thepotential formationofchemicalcompoundsinfoodsthatmaypresentahealththreatshouldbeevalu-atedtodeterminewhether thereisanytoxicologicalorchemicalsafetyconcernsassociatedwithproducts thathaveundergoneUVtreatment.CloserexaminationofUV-lightpotentialtodestroyundesirablecompoundsorpollutantsalsodeservesmoreattention.Due to lowpenetrationofUVlight, thecombinationswithotherpostharvesttechnologies(ozone,ultrasound,modifiedpackagingatmosphere,sani-tizing,andantibrowningagents)mightbeattractiveforprocessorsandmoreeffi-cient.LimiteddataareavailableonUVprocessingcombinedwithothertreatments,andfurtherstudiesarenecessary.


LISTOFABBREVIATIONS

A AbsorptionAIN AluminumnitrideEL ExcimerlampEPA U.S.EnvironmentalProtectionAgencyEVA EthylenevinylacetateEVOH EthylvinylalcoholcopolymerFDA U.S.FoodandDrugAdministrationLED LightemittingdiodesLPHO Low-pressurehigh-outputlampLPM Low-pressuremercurylampMCL MaximumcontaminantlevelMPM MediumpressuremercurylampPBS Phosphate-bufferedsalinePL PulsedlampPME PectinmethylesterasePPO PolyphenoloxidaseR ReflectionRDA RecommendeddailyallowanceTorUVT TransmittanceortransmittanceofmaterialintheultravioletrangeUV UltravioletUV-A Ultravioletlightrange:315400nmUV-B Ultravioletlightrange:280315nmUV-C Ultravioletlightrange:200280nmcUV ContinuousultravioletmodeVUV Vacuumultravioletradiation(100200nm)

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