Thermal & Non-thermal Juice Stabilization Technologies:

an overview

Massimiliano Pelacci

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GOALS:

➢ Overview of the reduction kinetics for the Thermal stabilization processes

➢ Overview of the principal existing Non-Thermal technologies for juices stabilization

WHO WE ARE

SCIENCE & TECHNICAL

COMMISSION (STC)

METHOD OF ANALISYS

COMMISSION

LEGISLATION COMMISSION

MICRO BIOLOGY COMMISSION

MARKETING COMMMISSION

WORKING GROUP

Thermal & Non-thermalstabilization technologies

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STABILIZATION TECHNOLOGIES BY PHISICAL PRINCIPLE

• Electrical treatments

Microwave Heating (MW)

Ohmic Heating (OH)

• Heat Transfer treatments

(conduction and convection)

NON-CONVENTIONAL THERMALCONVENTIONAL THERMAL

STANDPOINTS FOR THE OVERVIEWS

2) ENZYME INACTIVATION

1) MICROBIOLOGICAL REDUCTION

3) NUTRIENT COMPOUNDS DETERIORATION

NON-THERMAL

• Electrical treatment

Pulsed Electric Field (PEF)

• High Pressure treatment

High Pressure Processing (HPP)

• Inert-gas treatment

Pressure Change Technology (PCT)

• Radiation treatments

UV light (UV)

high-intensity Pulsed Light (PL)

1) MICROBIOLOGICAL STANDPOINT

41 FDA: Guidance for industry acidified foods - 20102 ECFF: Recommendation for packaged chilled foods

2) ENZYME STANDPOINT

Enzymes are complex bio-active proteins with a very intricate tertiary structure

TYPICAL ENZIMES IN FRUIT AND VEGETABLE JUICES

POD:PEROXYDASE

Responsible for a wide range of OXIDATIVE, QUALITY AND FLAVOR ALTERATIONS.

PPO:POLI-PHENOL-OXYDASE

Responsible for BROWNING and DEGRADATION of natural PIGMENTS.

PME:PECTIN-METHYL-ESTERASE

Responsible for LOSS OF TEXTURE, SOFTENING and CLARIFICATION of juices and purees.

3) NUTRIENT COMPOUNDS STANDPOINT

EXAMPLE OF MAIN NUTRIENT COMPOUNDS CONTAINED IN FRUIT AND VEGETABLE PRODUCTS

ORANGE APPLE STRAWBERRY CARROT

• ORGANIC ACIDS: CITRIC, ASCORBIC, MALIC;

• CAROTENOIDS;• FLAVONOIDS, LIMONOIDS.

• ORGANIC ACIDS: MALIC, ASCORBIC, CITRIC;

• POLIPHENOSLS: FLAVONOIDS.

• ORGANIC ACIDS: CITRIC, ASCORBIC;

• POLYPHENOLS: ANTOCYANINS.

• CAROTENOIDS;• ORGANIC ACIDS: MALIC,

ASCORBIC;• POLYPHENOLS. 5

THERMAL REDUCTION KINETICS

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MICROBIAL THERMAL INACTIVATION PARAMETERS

D-value: Decimal reduction time [min]It represents the time required, at a fixed process temperature T, to decrease the microorganisms population by 90%.

z-value: Thermal resistance constant [°C]It represents temperature change necessary for the D-value tochange by a factor 10.

F: Thermal Death Time [min]It is the total time required to accomplish the desired reduction in a population of vegetative cells or spores. This time can be expressed as a multiple of the D-value: [min]

MICROBIAL INACTIVATION SIDE PROCESSING PARAMETERS SIDE

Slope = −1

𝐷

Log N

Slope = −1

𝑧

Log D

C0= Initial bioactive compounds Concentration

C = Final bioactive compounds Concentration

R = the gas constant (1,987 cal/mole °K)

T = absolute temperature (°K)

Ea= activation energy of the reaction

A = concentration of the substrate

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CHEMICAL REACTIONS PARAMETERS

k: Reaction rate constantThe opposite of the slope in a chart showing the logarithm of bioactive compounds concentration over time, at a fixed process temperature T.

Ea: Activation energy [kJ/mol]It is the energy required to take a molecule from its average restingenergy to a point were reactants can interact to become products.It indicates how rapidly the reaction rate (k) is affected by changes intemperature.

Ln C

Time

K = Slope

➢ Many certified methods ANSI-AAMI / ISO / SIGMA to assess these parameters

➢ Commonly, their behave can be described by a first order kinetic model

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A

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R = the gas constant (1,987 cal/mole °K)T = Reference temperature, often assumed = T1 (°K)T1 = Reaction temperature (°K)

Therefore, using D- and z- values, it is possible to summarize on the same time / temperature chart:

MICROBIOLOGICAL REDUCTIONc

ENZYME INACTIVATION

NUTRIENT COMPOUNDS LOSSES

Correlation between the activation energy (Ea) and the thermal resistance constant (z-value):

Correlation between the reaction rate constant (k) and the decimal reduction time (D-value):

CORRELATIONS BETWEEN PARAMETERS

1010

CHART FOR STRAWBERRY JUICE

Alternative treatment(shelf stable)110°C – 30 s

Colour changes during Storage

Time Storage at T = 20° C Storage at T = 4° C

After treatment (L*, a*, b*) (L*, a*, b*)

3 months (L*, a*, b*) (L*, a*, b*)

6 months (L*, a*, b*) (L*, a*, b*)

9 months (L*, a*, b*) (L*, a*, b*)

Colour changes during Storage

Time Storage at T = 20° C Storage at T= 4° C

After treatment (L*, a*, b*) (L*, a*, b*)

3 months (L*, a*, b*) (L*, a*, b*)

6 months (L*, a*, b*) (L*, a*, b*)

9 months (L*, a*, b*) (L*, a*, b*)

NON-CONVENTIONAL THERMAL TREATMENTS

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NON-CONVENTIONAL (ELECTRICAL) THERMAL TREATMENTS

MWH HIGHLIGHTS

TYPE OF TECHNOLOGY Electromagnetic waves

HEATING MECHANISM Ionic polarization, intermolecular friction

INACTIVATION MECHANISM THERMAL (temperature and time)

OH HIGHLIGHTS

TYPE OF TECHNOLOGY High frequency electric current

HEATING MECHANISM Joule effect

INACTIVATION MECHANISM THERMAL (temperature and time)

ENERGY EFFICIENCY 97%

MICROWAVE

OHMIC

ENERGY EFFICIENCY 85% (@ 900 MHz), 80% (@ 2,450 MHz)

PROS:➢ Fast and uniform heating (about ¼ for MWH and 1/10 for OH

with respect to conventional thermal)→ lower cooking value,lower nutrients degradation, better color preservation;

➢ Suitable for products containing dices or particulates.

CONS:➢ Electric energy is more expensive than steam.

NON-THERMAL TREATMENTS

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PULSED ELECTRIC FIELDS (PEF)

PEF HIGHLIGHTS

TYPE OF TECHNOLOGY Pulsed electric fields

INACTIVATION

MECHANISM

ELECTRO-PORATION (electric field strength,

pulses width, frequency and exposure time)

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1) Bevilacqua et al. (2018)2) Pellicer et al. (2017) 3) Elez-Martìnez et al. (2004)4) Uemura et al. (2003)5) Claudia Siemer PhD (2014)6) Liesbeth Vervoort et al. (2011)7) Sánchez-Moreno et al. (2005)

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FEATURE OH PEF

Main inactivation parameter

Temperature reached

and

holding time

Electric field strength, duration and

frequency of pulses, temperature

and time engaged

Microbial inactivation mechanism THERMAL ELECTROPORATION

Product heating RequisiteSide effect

(mild pre-heating required)

Electric field strength 0,05 ÷ 0,15 kV/cm 5 ÷ 60 kV/cm

Electrical architecture Frequency converter Banks of condensers

Specific energy 335 [kJ/Kg] 100 ÷ 270 [kJ/Kg]

Pulses width 1 ÷ 25 µs 1 ÷ 100 µs

Frequency 20.000 ÷ 30.000 Hz 1 ÷ 1.000 Hz

Effect on spores Remarkable Not suitable at low temperature

DIRECT COMPARISON: OHMIC VS PEF

HPP HIGHLIGHTS

TYPE OF TECHNOLOGY High (hydrostatic) Pressure Process

INACTIVATION

MECHANISM

Stresses due to HIGH-PRESSURE

(pressure level reached and holding time)

PRESSURE RANGE 100 ÷ 800 Mpa (1000 – 8000 Bar)

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HIGH PRESSURE PROCESS (HPP)

BATCH PROCESS TREATMENT APPLIED TO PACKAGED PRODUCT

1) Lucía Plaza et al. (2011)2) Bevilacqua et al. (2018) 3) Wang et al. (2012)4) Ma et al. (2010)5) Liesbeth Vervoort et al. (2011)6) Sánchez-Moreno et al. (2005)

PCT HIGHLIGHTS

TYPE OF

TECHNOLOGY

Compression and inert-gas saturation

→ gas penetrates cells during holding

time → quick expansion

INACTIVATION

MECHANISM

Cells membrane disruption due to

sudden gas expansion

1) Aschoff et al. (2016) 2) Bönsch et al. (2007)

PRESSURE RANGE 25 ÷ 50 MPa

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PRESSURE CHANGE TECHNOLOGY (PCT)

UV HIGHLIGHTS

TYPE OF TECHNOLOGY Continuous radiation with ultra-violet light

INACTIVATION MECHANISMPHOTOCHEMICAL (exposure causes damage at DNA

level which impairs the process of cell replication)

CHARACTERISTICS UNIT REFERENCE VALAUES

WAVELENGHT SPECTRUM [nm] 200 ÷ 400 nm (Mercury lamps)

RADIATION INTENSITY [J/cm2] 0,5 ÷ 80 J/cm2

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ULTRA VIOLET LIGHT (UV)

1) Akgün et al. (2017)2) Bevilacqua et al. (2018)3) Guevara et al. (2012)4) Tremarin et al. (2017)

PL HIGHLIGHTS

TYPE OF TECHNOLOGY Radiation with high-energy wide-spectrum pulsed light

INACTIVATION MECHANISM

PHOTOCHEMICAL (damage at DNA level)

PHOTOTHERMAL (membrane disruption due to a

momentous overheating)

PHOTOPHYSICAL (cytoplasmic membrane contraction)

CHARACTERISTICS UNIT REFERENCE VALAUES

WAVELENGHT SPECTRUM [nm] 100 ÷ 1.100 nm (Xenon lamps)

RADIATION INTENSITY [J/cm2] 5 ÷200 J/cm2

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PULSED LIGHT (PL)

1) Pataro et al. (2011)2) Pellicer et al. (2017)3) Ferrario et al. (2015)

SPECIFIC WORKING ENERGY CONSUMPTION COMPARISON

FOUNDAMENTAL HYPOTHESISASSUMED

• Product TIN = TOUT = 20°C

• Equivalent lethal effect for all treatments (Tmax ≤ 68°C)

• Results expressed in [KJ/Kg]

• Both cases of 0% and 80% heat recovery

COMPONENTS OF WORKING ENERGY DEMAND CONSIDERED

• Stabilization Treatment

• Fluids Pumping

• Heat Dissipation (OH, MW, PL)

• Product Cooling (THERMAL, OH, MW, PEF)

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➢ Conventional thermal treatments:• most common approach;• possible negative impact on nutritional, quality and fresh-like characteristics of the product;• significant potential for improvement by using the proposed 3-standpoints approach..

➢ Non-conventional thermal processes:• partial solution• possibility to reach high temperatures faster and more uniformly• lower cooking value, lower nutrients degradation and better color preservation

➢ Non-thermal approaches:• better nutrients and fresh-like characteristics retention;• variable effects on spoilage microorganisms and enzymes→ final products often requiring a refrigerated storage;• challenging scale-up from laboratory scale level

FINAL CONSIDERATIONS

using the SAME PRODUCT for all processes considered

establishing equal SHELF-LIFE target and

STORAGE CONDITIONS

considering together MICROBIAL reduction, ENZYME inactivation and

NUTRIENT COMPOUNDS losses.

➢ Further experimental tests are necessary to compare different approaches, but they should be performed:

➢ Thermal treatments are still the only processes able to obtain low acid shelf-stable products.

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