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FACULTY OF TECHNOLOGY – NOVI SAD ТЕХНОЛОШКИ ФАКУЛТЕТ – НОВИ САД

ACTA PERIODICA TECHNOLOGICA

APTEFF, 40, 1-220 (2009)

ACTA PERIODICA TECHNOLOGICA - Novi Sad (formerly Zbornik rado-va Tehnološkog fakulteta and Proceedings of Faculty of Technology) publishes articles from all branches of technology (food, chemical, biochemical, pharmace-utical), process engineering and related scientific fields. Articles in Acta Periodica Technologica are abstracted by: Chemical Abs-tracts, Columbus, Ohio, Referativnii zhurnal – Khimija, VINITI, Moscow, listed in Ulrich’s International Periodical Directory, and indexed in the Elsevier Biblio-graphic data bases – SCOPUS. YU ISSN 1450 – 7188 CODEN: APTEFF UDC 54:66:664:615 Publisher University of Novi Sad, Faculty of Technology 21000 Novi Sad, Bulevar Cara Lazara 1, Serbia For Publisher Prof. Dr. Zoltan Zavargo, Dean Editor-in-Chief Prof. Dr. Sonja Đilas Editorial Board From Abroad Prof. Dr. Živko Nikolov Texas A and M University, Biological and Agricultural Engineering Department, College Station, TX, USA Prof. Dr. Erika Békássy-Molnár University of Horticulture and Food Industry, Budapest, Hungary Prof. Dr. Željko Knez University of Maribor, Faculty of Chemistry and Chemical Technology, Maribor, Slovenia Dr. T.S.R. Prasada Rao Indian Institute of Petroleum, Dehra Dun, India Prof. Dr. Đerđ Karlović Margarine Center of Expertise, Kruszwica, Poland Dr. Szigmond András Research Institute of Hungarian Sugar Industry, Budapest, Hungary Dr. Andreas Reitzmann Institute of Chemical Process Engineering, University Karlshruhe From Serbia Dr. Ratko Lazarević, Academician Prof. Dr. Petar Dokić Prof. Dr. Slobodan D. Petrović Prof. Dr. Spasenija Milanović Prof. Dr. Erne Kiš Prof. Dr. Vladimir Srdić

ACTA PERIODICA TECHNOLOGICA APTEFF, 40, 1-220 (2009)

CONTENT

FOOD TECHNOLOGY

Biljana R. Cvetković and Marija R. Jokanović EFFECTS OF PRESERVATION METHOD AND STORAGE CONDITION ON ASCORBIC ACID LOSS IN BEVERAGES 1 Gordana R. Dimić, Sunčica D. Kocić-Tanackov, Dušanka J. Pejin, Jelena D. Pejin, Ilija J. Tanackov and Danijela Tuco ANTIMICROBIAL ACTIVITY OF CARAWAY, GARLIC AND OREGANO EXTRACTS AGAINST FILAMENTOUS MOULDS 9 Ljubica P. Dokić, Marija I. Bodroža-Solarov, Miroslav S. Hadnađev and Ivana R. Nikolić PROPERTIES OF EXTRUDED SNACKS SUPPLEMENTED WITH AMARANTH GRAIN GRITS 17 Aleksandar Z. Fišteš and Đuro M. Vukmirović REDUCTION OF WHEAT MIDDLINGS USING A CONVENTIONAL AND EIGHT-ROLLER MILLING SYSTEMS 25 Gordana B. Koprivica, Nevena M. Mišljenović, Ljubinko B. Lević and Vjera S. Pribiš CHANGES IN NUTRITIVE AND TEXTURAL QUALITY OF APPLE OSMODEHYDRATED IN SUGAR BEET MOLASSES AND SACCHAROSE SOLUTIONS 35 Radomir V. Malbaša, Eva S. Lončar, Spasenija D. Milanović and Ljiljana A. Kolarov USE OF MILK-BASED KOMBUCHA INOCULUM FOR MILK

FERMENTATION 47 Anamarija I. Mandić, Sonja M. Djilas, Jasna M. Čanadanović-Brunet, Gordana S. Ćetković and Jelena J. Vulić ANTIOXIDANT ACTIVITY OF WHITE GRAPE SEED EXTRACTS ON DPPH RADICALS 53

Spasenija D. Milanović, Mirela D. Iličić, Katarina G. Duraković and Vladimir R. Vukić TEXTURAL CHARACTERISTICS OF FERMENTED MILK BEVERAGES PRODUCED BY KOMBUCHA 63 Dragan V. Palić and Sophia E. Coetzee PROTOCOL FOR USING PROTEIN SOLUBILITY AS AN INDICATOR OF FULL-FAT SOYBEAN HEAT TREATMENT 71 Dragan V. Palić and Klaas-Jan Leeuw COMPARISON OF THREE IN VITRO METHODS FOR DETERMINING AND PREDICTING THE ORGANIC MATTER DIGESTIBILITY OF COMLETE DIETS FOR RUMINANTS 79 Dragana Pešić-Mikulec and Gordana B. Niketić COMPOSITIONAL CHARACTERISTICS OF COMMERCIAL YOGHURT BASED ON QUANTITATIVE DETERMINATION OF VIABLE LACTIC ACID BACTERIA 87 Slađana M. Savatović, Aleksandra N. Tepić, Zdravko M. Šumić and Milan S. Nikolić ANTIOXIDANT ACTIVITY OF POLYPHENOL-ENRICHED APPLE JUICE 95 Mirjana A. Vasić, Biserka L. Vujičić, Aleksandra N. Tepić, Jelica M. Gvozdenović-Varga and Zdravko M. Šumić DIETARY FIBER CONTENT IN SOME DRY BEANS 103 Tanja D. Žugić-Petrović, Nataša M. Joković and Dragiša S. Savić THE EVOLUTION OF LACTIC ACID BACTERIA COMMUNITY DURING THE DEVELOPMENT OF MATURE SORDOUGH 111

CHEMICAL TECHNOLOGY AND PROCESS ENGINEERING Eva S. Lončar, Miroslava M. Radeka, Snežana B. Petrović, Andrea S. Skapin, Ognjen Lj. Rudić and Jonjaua G. Ranogajec DETERMINATION OF THE PHOTOCATALYTIC ACTIVITY OF TiO2

COATINGS ON CLAY ROOFING TILE SUBSTRATES – METHYLENE BLUE AS MODEL POLLUTANT 125 Nataša Lj. Lukić, Svetlana S. Popović and Jelena Dj. Marković MATHEMATICAL MODELLING OF FLUX RECOVERY DURING CHEMICAL CLEANING OF TUBULAR MEMBRANE FOULED WITH WHEY PROTEINS 135 Nevena M. Mišljenović, Gordana B. Koprivica, Ljubinko B. Lević, Bojana V. Filipčev and Tatjana A. Kuljanin OSMOTIC DEHYDRATION OF RED CABBAGE IN SUGAR BEET MOLASSES - MASS TRANSFER KINETICS 145

Slaviša S. Putić, Marina R. Stamenović, Branislav B. Bajčeta and Dragana D. Vitković DETERMINATION OF TENSION STRENGHT IN THE LONGITUDINAL AND CIRCUMFERENTIONAL DIRECTION IN GLASS-POLYESTER COMPOSITE PIPES 155 Aleksandar R. Stanić, Saša I. Jovanić, Nikola J. Marjanović and Zvonimir J. Suturović THE USE OF L-ASCORBIC ACID IN SPECIATION OF ARSENIC COMPOUNDS IN DRINKIG WATER 165 Marina B. Šćiban, Mile T. Klašnja and Mirjana G. Antov TREATMENT OF SUGAR BEET THICK JUICE SPENT WASH BY CHEMICAL AND NATURAL COAGULANTS 177 Ivana M. Šijački, Radmilo R. Čolović, Milenko S. Tokić and Predrag S. Kojić SIMPLE CORRELATIONS FOR BUBBLE COLUMNS AND DRAFT TUBE AIRLIFT REACTORS WITH DILUTE ALCOHOL SOLUTIONS 183

BIOCHEMICAL AND PHARMACEUTICAL ENGINEERING Marija M. Škrinjar and Nevena T. Nemet ANTIMICROBIAL EFFECTS OF SPICES AND HERBS ESSENTIAL OILS 195 Dušanka J. Pejin, Olgica S. Grujić, Jelena D. Pejin, Irena S. Došenović and Sunčica D. Kocić-Tanackov THE INFLUENCE OF CARBOXYMETHYLCELLULOSE, XANTHAN AND GUAR-GUM ADDITION IN BREAD DOUGH BEFORE FREEZING ON METABOLISM AND VIABILITY OF Saccharomyces cerevisiae 211

IN MEMORIAM

Prof. dr Nikola J. Marjanović 223

INSTRUCTION FOR MANUSCRIPT PREPARATION

ACTA PERIODICA TECHNOLOGICA APTEFF, 40, 1-220 (2009)

САДРЖАЈ

ПРЕХРАМБЕНА ТЕХНОЛОГИЈА

Биљана Р. Цветковић и Марија Р. Јокановић УТИЦАЈ МЕТОДЕ КОНЗЕРВИСАЊА И УСЛОВА СКЛАДИШТЕЊА НА ГУБИТАК АСКОРБИНСКЕ КИСЕЛИНЕ У ОСВЕЖАВАЈУЋИМ

БЕЗАЛКОХОЛНИМ ПИЋИМА 1 Гордана Р. Димић, Сунчица Д. Коцић-Танацков, Душанка Ј. Пејин, Јелена Д. Пејин, Илија Ј. Танацков и Данијела Туцо АНТИМИКРОБНА АКТИВНОСТ ЕКСТРАКАТА КИМА, БЕЛОГ ЛУКА И ОРИГАНА НА ФИЛАМЕНТОЗНЕ ПЛЕСНИ 9 Љубица П. Докић, Марија И. Бодрожа-Соларов, Мирослав С. Хаднађев и Ивана Р. Николић СВОЈСТВА ЕКСТРУДАТА СА ДОДАТКОМ КРУПИЦЕ ОД СЕМЕНА АМАРАНТУСА 17 Александар З. Фиштеш и Ђуро М. Вукмировић ЕФЕКТИ МЛЕВЕЊА ПШЕНИЧНОГ ГРИЗА У КЛАСИЧНОМ И ПОСТУПКУ СА ОСМОВАЉНОМ СТОЛИЦОМ 25 Гордана Б. Копривица, Невена М. Мишљеновић, Љубинко Б. Левић и Вјера С. Прибиш ПРОМЕНА НУТРИТИВНОГ КВАЛИТЕТА ЈАБУКЕ ПРИ ОСМОТСКОЈ ДЕХИДРАТАЦИЈИ У РАСТВОРИМА САХАРОЗЕ И МЕЛАСИ ШЕЋЕРНЕ РЕПЕ 35 Радомир В. Малбаша, Ева С. Лончар, Спасенија Д. Милановић и Љиљана А. Коларов ПРИМЕНА МЛЕЧНО-ФЕРМЕНТИСАНОГ ИНОКУЛУМА КОМБУХЕ ЗА ФЕРМЕНТАЦИЈУ МЛЕКА 47 Анамарија И. Мандић, Соња М. Ђилас, Јасна М. Чанадановић-Брунет, Гордана С. Ћетковић и Јелена Ј. Вулић АНТИOКСИДАТИВНА АКТИВНОСТ ЕКСТРАКАТА СЕМЕНА БЕЛОГ ГРОЖЂА НА DPPH РАДИКАЛЕ 53

Спасенија Д. Милановић, Мирела Д. Иличић, Катарина Г. Дураковић и Владимир Р. Вукић ТЕКСТУРАЛНЕ ОСОБИНЕ ФЕРMЕНТИСАНИХ МЛЕЧНИХ НАПИТАКА ДОБИЈЕНИХ ПРИМЕНОМ КОМБУХЕ 63 Драган В. Палић и Sоphia E. Coetzee ПОСТУПАК ЗА КОРИШЋЕЊЕ РАСТВОРЉИВОСТИ ПРОТЕИНА КАО ИНДИКАТОРА ТЕРМИЧКОГ ТРЕТМАНА ПУНОМАСНЕ СОЈЕ 71 Драган В. Палић и Klaas-Jan Leeuw ПОРЕЂЕЊЕ ТРИ IN VITRO МЕТОДЕ ЗА ОДРЕЂИВАЊЕ И ПРОЦЕНУ СВАРЉИВОСТИ ОРГАНСКЕ МАТЕРИЈЕ У ПОТПУНИМ СМЕШАМА ЗА ПРЕЖИВАРЕ 79 Драгана Пешић-Микулец и Гордана Б. Никетић КВАНТИТАТИВНО ОДРЕЂИВАЊЕ БАКТЕРИЈА МЛЕЧНЕ КИСЕЛИНЕ КОМЕРЦИЈАЛНИХ УЗОРАКА ЈОГУРТА 87 Слађана М. Саватовић, Александра Н. Тепић, Здравко М. Шумић и Милан С. Николић АНТИОКСИДАТИВНА АКТИВНОСТ СОКА ОД ЈАБУКА ОБОГАЋЕНОГ ПОЛИФЕНОЛНИМ ЈЕДИЊЕЊИМА 95 Мирјана А. Васић, Бисерка Л. Вујичић, Александра Н. Тепић, Јелица М. Гвозденовић-Варга и Здравко М. Шумић САДРЖАЈ ДИЈЕТЕТСКИХ ВЛАКАНА У НЕКИМ СОРТАМА ПАСУЉА 103 Тања Д. Жугић-Петровић, Наташа М. Јоковић и Драгиша С. Савић РАЗВОЈ ПОПУЛАЦИЈЕ БАКТЕРИЈА МЛЕЧНЕ КИСЕЛИНЕ У ТОКУ ФОРМИРАЊА ЗРЕЛОГ КИСЕЛОГ ТЕСТА 111

ХЕМИЈСКА ТЕХНОЛОГИЈА И ПРОЦЕСНО ИНЖЕЊЕРСТВО

Ева С. Лончар, Мирослава М. Радека, Снежана Б. Петровић, Андреа С. Скапин, Огњен Љ. Рудић и Јоњауа Г. Раногајец ОДРЕЂИВАЊЕ ФОТОКАТАЛИТИЧКЕ АКТИВНОСТИ TiO2 ПРЕВЛАКА НА ЦРЕПУ КОРИШЋЕЊЕМ МЕТИЛЕН ПЛАВОГ КАО МОДЕЛ ПОЛУТАНТА 125 Наташа Љ. Лукић, Светлана С. Поповић и Јелена Ђ. Марковић МАТЕМАТИЧКО МОДЕЛОВАЊЕ РЕГЕНЕРАЦИЈЕ ФЛУКСА ТОКОМ ХЕМИЈСКОГ ЧИШЋЕЊА ТУБУЛАРНЕ МЕМБРАНЕ ЗАПРЉАНЕ ПРОТЕИНИМА СУРУТКЕ 135

Невена М. Мишљеновић, Гордана Б. Копривица, Љубинко Б. Левић, Бојана В. Филипчев и Татјана А. Куљанин ОСМОТСКА ДЕХИДРАТАЦИЈА ЦРВЕНОГ КУПУСА У МЕЛАСИ ШЕЋЕРНЕ РЕПЕ – КИНЕТИКА ПРЕНОСА МАСЕ 145 Славиша С. Путић, Марина Р. Стаменовић, Бранислав Б. Бајчета и Драгана Д. Витковић ОДРЕЂИВАЊЕ ЗАТЕЗНЕ ЧВРСТОЋЕ У УЗДУЖНОМ И ОБИМНОМ

ПРАВЦУ У СТАКЛО-ПОЛИЕСТЕР КОМПОЗИТНИМ ЦЕВИМА 155 Александар Р. Станић, Саша И. Јованић, Никола Ј. Марјановић и Звонимир Ј. Сутуровић ПРИМЕНА Л-АСКОРБИНСКЕ КИСЕЛИНЕ ПРИ ОДРЕЂИВАЊУ

РАЗЛИЧИТИХ ОБЛИКА АРСЕНА У ВОДИ ЗА ПИЋЕ 165 Марина Б. Шћибан, Миле Т. Клашња и Мирјана Г. Антов ТРЕТМАН ЏИБРЕ ОД ГУСТОГ СОКА ХЕМИЈСКИМ И ПРИРОДНИМ КОАГУЛАНТИМА 177 Ивана М. Шијачки, Радмило Р. Чоловић, Миленко С. Токић и Предраг С. Којић ПРЕДВИЂАЊЕ ОСНОВНИХ ХИДРОДИНАМИЧКИХ И

МАСЕНОПРОЦЕСНИХ КАРАКТЕРИСТИКА У БАРБОТАЖНИМ КОЛОНАМА СА И БЕЗ УНУТРАШЊЕ ЦЕВИ СА РАЗБЛАЖЕНИМ РАСТВОРИМА АЛКОХОЛА 183

БИОХЕМИЈСКО И ФАРМАЦЕУТСКО ИНЖЕЊЕРСТВО

Марија М. Шкрињар и Невена Т. Немет АНТИМИКРОБНО ДЕЛОВАЊЕ ЕСЕНЦИЈАЛНИХ УЉА ЗАЧИНА И ЛЕКОВИТОГ БИЉА 195 Душанка Ј. Пејин, Олгица С. Грујић, Јелена Д. Пејин, Ирена С. Дошеновић и Сунчица Д. Коцић-Танацков УТИЦАЈ ДОДАТКА КАРБОКСИМЕТИЛЦЕЛУЛОЗЕ, КСАНТАНА И ГУАР-ГУМЕ У ХЛЕБНО ТЕСТО ПРЕ ЗАМРЗАВАЊА НА МЕТАБОЛИЗАМ И ВИЈАБИЛНОСТ Saccharomyces cerevisiae 211

IN MEMORIAM

Проф. др Никола Ј. Марјановић 223

УПУТСТВО ЗА АУТОРЕ

FOOD TECHNOLOGY

APTEFF, 40, 1-220 (2009) UDC: 663.86:577.164.2:663.053 DOI: 10.2298/APT0940001C BIBLID: 1450-7188 (2009) 40, 1-7

Original scientific paper

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EFFECT OF PRESERVATION METHOD AND STORAGE CONDITION ON ASCORBIC ACID LOSS IN BEVERAGES

Biljana R. Cvetković and Marija R. Jokanović

Global market is flooded with vitamin-enriched foods, mainly beverages. Major vita-mins for enriching beverages are the antioxidant vitamins A, C and E. Ascorbic acid is readily oxidized and lost during storage of the beverages, at rates depending on the con-ditions of storage. This fact is of great importance for the consumer who must know how to store beverages and when to consume them in order to get the maximum benefit of ad-ded vitamin C. The objective of this paper was to determine the amount of ascorbic acid lost in beverages applying different preservation methods and storage condition. Beve-rage was made in laboratory conditions with synthetic L-ascorbic acid added according to the national legislations. After 30 days of storage at 4-8oC ascorbic acid overall loss was from 81.01% to 90.27% in thermally pasteurized samples and from 97.83 % to al-most complete loss in samples preserved with sodium benzoate. KEY WORDS: L-ascorbic acid, colorimetric method, beverage, storage

INTRODUCTION L-ascorbic acid is largely accepted as additive in human diets because of its anti-oxidative potential. The richest natural vitamin C sources are fruits and vegetables like pepper, rose hip, citrus fruit, and green vegetables. Fruits and vegetables supply more than 90% of vitamin C in human diets (1). A high recommendation of daily intake for humans has been suggested, since stress in modern life is known to increase the requirement for vitamin C (2). L-ascorbic acid is nutrient that besides its vitamin action is valuable for its antioxidant effect, stimulation of the immune system and other health benefits, such as prevention of scurvy and mainte-nance of healthy skin, gums and blood vessels. Vitamin C also reportedly reduces the risk of arteriosclerosis, cardiovascular diseases and some forms of cancer. Vitamin C is a generic name for all compounds exhibiting the biological activity of L-ascorbic acid (AA). AA is the principal biologically active form but L-dehydroascorbic

Biljana R. Cvetković, B.Sc., [email protected], Institute for Food Technology, Bulevar Cara La-zara 1, 21000 Novi Sad; Marija R. Jokanović, M.Sc., Assist., [email protected], Faculty of Technology, Bulevar Cara Lazara 1, 21000 Novi Sad, Serbia



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acid (DHA), an oxidation product, also exhibits biological activity (3). Addition of syn-thetic ascorbic acid increases content of vitamin C, influences maintenance of colour, fla-vour and universal stability of the food products (fruit juices, beverages, baby food, etc.) (4). Natural and synthetic L-ascorbic acids are chemically identical and there are no known differences in their biological activities or bioavailability (5). Based on available biochemical, clinical and epidemiological studies, the current recommended daily acceptance for ascorbic acid is suggested to be 100-120 mg/day to achieve cellular saturation and optimum risk reduction of heart diseases, stroke and can-cer in healthy individuals (6). As a consequence of the common man’s increasing awareness regarding the im-portance of vitamin C, the global market is flooded with vitamin-enriched foods, mainly beverages. Major vitamins for enriching beverages are the antioxidant vitamins A, C and E. Vitamin C is usually added as ascorbic acid (7, 8). Fortification is a growing trend in soft drinks and in the dairy sector, and played a role in 8% of all new food and drink products introduced in 2003 (9). L-ascorbic acid application in the food industry increases quality and technological properties of food, as well as nutritional value (10). Ascorbic acid is highly sensitive to various modes of deterioration. The main factors that can affect ascorbic acid loss include temperature, salt and sugar concentration, pH, oxygen, light, metal catalysts, initial concentration of ascorbic acid, the ratio of ascorbic acid to dehydroascorbic acid, microbial load and protection by the container (11). The loss of nutritional quality during processing and storage of food has become an important problem. Since the discovery of the basic vitamins and their many forms, ef-forts have been made to retain them in foods during post-harvest, commercial processing, distribution, storage and preparation. Vitamin C is usually selected as an index of the nutrient quality because of its labile nature as compared to the other nutrients in food (1). The term beverages-soft drink originally applied to carbonated and non-carbonated drinks made from concentrates, although it now commonly refers to almost any cold drink that does not contain alcohol (12). Ascorbic acid added to beverages is readily oxidized and lost during staying, at a rate depending on the conditions of storage. This fact is of great importance to the consumer who must know how to store the beverages and when to consume them in order to get the maximum benefit of vitamin C content. (13). Determination of the nutrient content of foods is becoming extremely important as researchers learn more about the relationship between dietary intake and human health (14). Various methods have been reported in the literature for the quantitative deter-mination of vitamin C in foods or biological fluids. The usual methods include titration (AOAC), colourimetric, spectrophotometry, fluorometry, electrophoresis, and high per-formance liquid chromatography (HPLC). Objectives of this paper were:

a) preparation of non-alcoholic beverages in laboratory conditions with addition of synthetic ascorbic acid and two methods of preservation;

b) analysis of the amount of ascorbic acid loss in samples during 30 days under different storage conditions, in closed glass bottles, storage in the refrigerator, and in the dark at room temperature and in a thermostat at 37oC.



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EXPERIMENTAL

Materials

Beverage preparation. Beverage was prepared by diluting commercial beverage concentrate (Aretol no. 72 408, Celje, Slovenia) in water in a ratio 3:97. Sugar was added like inverted syrup (dry matter content in the final product about 9.5 %), and then citric acid was added to get appopriate sensory characteristics. There were alltogether prepared 12 samples. Ascorbic acid was added in two concentrations: 100 mg/l and 150 mg/l. For thermal pasteurisation were transferred into 200 ml glass bottles, second part of samples were first preserved with sodium benzoate and than transferred into 200 ml glass bottles. Preservation. Twelve samples (with both AA added concentrations) were divided in two parts:

a) One part was thermally treated (pasteurisation). Thermal pasteurisation condi-tions (85oC, 15 minutes) were selected to be the same as in a conventional pasteurisation of industrially produced beverages.

b) The other part was preserved with sodium benzoate in concentration of 130 mg /l, in the final product, which is in accordance with national legislations (15).

Shelf-life study. Samples of beverages thermally pasteurised or preserved with sodi-um benzoate were stored in three different temperatures conditions: refrigerator (4-8oC), room temperature (20-22oC), and in a thermostat at 37oC. Samples were evaluated after 30 days of storage, by measuring ascorbic acid content.

Method Determination of L-ascorbic acid. Ascorbic acid content was determined using co-lourimetric method. L-ascorbic acid reduces the tetrazolium salt MTT (3-(4,5-dimethyl-thiazolyl-2)-2,-diphenyltetrazolium bromide) in the presence of the electron carrier PMS (5-methylphenazinium methosulphate) at the pH 3.5 to a formazan (MTT-formazan), which is determined by measuring absorbance at 578 nm. Under the conditions stated in this procedure, assay is specific for L-ascorbic acid. The L-ascorbic acid content of these clear solutions was determined without any sample treatment. The detection limit of the method was 0.175 mg/l. Each value was measured in triplicate and averaged with standard deviation.

RESULTS AND DISCUSSION According to our results pasteurisation method had high influence on vitamin C content. Thermal pasteurisation gradually decreased L-ascorbic acid content. Ascorbic acid contents immediately after thermal pasteurisation in samples with 150 mg/l and 100 mg/l of added vitamin C, were 37.66 mg/l and 25.84 mg/ respectively (Table 1).



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Table 1. Average ascorbic acid content with standard deviation and it loss in samples immediately after pasteurisation and preservation

Ascorbic acid content (mg/l) Samples

Pasteurisation Sodium benzoate preservation 100 mg/l added ascorbic acid 25.84 ± 3.58 71.19 ± 8.02 150 mg/l added ascorbic acid 37.66 ± 2.98 113.40 ± 8.35

According to Blasco et al. (2004), there are two different rates of ascorbic acid degra-dation observed during the heating process: an aerobic degradation followed by an anae-robic degradation. In the beginning of the heating process oxygen remains in the bottle and therefore aerobic degradation of the ascorbic acid with oxygen in abundance takes place. With prolonged time of heating the atmosphere in the bottle becomes saturated with vapour, so that the oxygen concentration is minimal and the ascorbic acid is degra-ded anaerobically (16). During the preservation of beverages with sodium benzoate the loss of added ascorbic acid was much lower than in thermally treated samples. Immediately after preservation, the loss of ascorbic acid in samples with sodium benzoate was 24.40 % and 28.81 % for samples with 150 mg/l and 100mg/l added ascorbic acid, respectively.

74.16

28.81

74.89

24.4

0

10

20

30

40

50

60

70

80

Thermal pasteurisation Sodium benzoate preservation

Asco

rbic

aci

d lo

ss (%

)

100 mg/l added vitamin C150 mg/l added vitamin C

Fig. 1. Ascorbic acid loss immediately after the two methods of preservation

Table 2. Average ascorbic acid content (mg/l) with standard deviations in the beverages after 30 days of storage at 4-8, 20-22 and 37oC

Pasteurisation Preserved with sodium-benzoate Storage

temperature AA 150 mg/l AA

100 mg/l AA

150 mg/l AA

100 mg/l 4-8oC 28.37 ± 1.26 2.17 ± 0.30 14.6 ± 1.99 0.43 ± 0.08

20-22oC nd* nd nd nd 37oC nd nd nd nd

*nd - not detected; AA- ascorbic acid



5

97.83 99.57

81.0190.26

0

20

40

60

80

100

120

Thermal pasteurisation Sodium benzoate preservation

Asc

orbi

c ac

id lo

ss (%

)

100 mg/l added vitamin C 150 mg/l added vitamin C

Fig. 2. Ascorbic acid loss after 30 days of storage in a refrigerator (4-8 oC)

Storage temperature had a great influence on ascorbic acid loss. After 30 days of sto-rage at room temperature (20-22oC) and in thermostat at 37oC ascorbic acid was not de-tected in any sample. After 30 days of storage at 4-8oC and thermal pasteurisation the overall loss of ascorbic acid was 81.01 % in samples with 150 mg/l added ascorbic acid, and 97.83 % in samples with 100 mg/l added ascorbic acid. In the beverages preserved with sodium benzoate after one month of storage at 4-8oC ascorbic acid overall loss was from 90.27 % in samples with added concentration of 150 mg/l to almost complete loss for samples with 100 mg/l of added ascorbic acid (Fig. 2). Heating method had a definite influence on the retention of ascorbic acid. According to Vikram et al. (2005), by each heating method of orange juice, temperature had a greater influence and the degradation was rapid at higher temperatures (17). The decrease of ascorbic acid concentration to levels unacceptable by declaration or industrial practise often defines the product shelf life. During storage, the vitamin C con-tent gradually decreases at a rate depending on the processing and storage temperature. The more rapid decrease of ascorbic acid concentration at the beginning of the storage can be attributed to the immediate reaction of an amount of ascorbic acid with the dissol-ved oxygen (18). Degradation of ascorbic acid both by aerobic and anaerobic pathways depends upon many factors such as oxygen, heat, light, storage temperature and storage time. Oxidation of ascorbic acid occurs mainly during the processing, whereas, anaerobic degradation of vitamin C mainly appears during storage, which is especially observed in thermally pre-served juices (10).

CONCLUSION The decrease of vitamin C content to levels unacceptable by declaration or industrial practise often defines product shelf-life. During storage, the vitamin C content gradually decreases at a rate depending on processing and storage temperature. The more rapid de-crease of ascorbic acid concentration at the beginning of the storage can be attributed to the immediate reaction of an amount of ascorbic acid with the dissolved oxygen (18).



6

According to Blasco et al. (2004) there are two different rates of ascorbic acid de-gradation observed during the heating process: an aerobic degradation, followed by an anaerobic degradation. In the beginning of the heating process oxygen remains in the bottle and therefore aerobic degradation of the ascorbic acid with oxygen in abundance takes place. With prolonged time of heating, the atmosphere in the bottle becomes satu-rated with vapour, so that the oxygen concentration is minimal and the ascorbic acid is degraded anaerobically (16). The experiments have shown that L- ascorbic acid added like additive in non-alco-holic beverage is extremely unstable in water solution. The samples with a lower initial content of ascorbic acid lose it faster than those with a greater content. Ascorbic acid loss was greater in preserved than in pasteurised beverages. It should be recommended that beverage with ascorbic acid added should be consumed after preparation with no long time of storage.

ACKNOWLEDGEMENT The authors gratefully acknowledge the financial support from the Ministry of Scien-ce and Technological Development of the Republic of Serbia (Project TP-20068).

REFERENCES 1. Erentuk. S, Gualaboglu M.S. and S. Gultekin: The effects of cutting and drying

medium on the vitamin C content of rosehip during drying. Journal of Food Engine-ering 68 (2005) 513-518.

2. Olivier Fain: Musculoskeletal manifestations of scurvy, Review, Joint Bone Spine (2004).

3. Lee S. K. and Adel A. Kader: Preharvest and post harvest factors influencing vitamin C content of horticultural crops. Post harvest Biology and Technology 20 (2000) 207-220.

4. Del Caro A.: Changes of flavonoids, vitamin C and antioxidant capacity in minimally processed citrus segments and juices during storage. Food Chemistry 84 (2004) 99-105.

5. Lee H.S. and G. A. Coates: Vitamin C in frozen, fresh squeezed, unpasturized, poly-ethylene-bottled orange juice: storage study. Food Chemistry 65 (1999) 165-168.

6. Klimezak I., Malecka M., Szlahta M. and A. Gliszezynska-Swiglo: Effect of storage on the content of polyphenols, vitamin C and the antioxidant activity of orange juices. Journal of Food Composition and Analysis 20 (2007) 313-322.

7. Arya S. P., Mahajan M. and P.Jain: Non-spectrophotometric methods for the deter-mination of Vitamin C. Analytica Chimica Acta 417 (2000) 1-14.

8. Rodriguez-Comesana M., Garcia-Falcon M. S. and J. Simal-Gandara: Control of nu-tritional labels in beverages with added vitamins: screening of β-carotene and ascor-bic acid contents. Food Chemistry 79 (2002) 141-144.

9. Prieto P. S., Grande C. B., Falkon G. S. and S. J. Gandara: Screening for folic acid content in vitamin-fortified beverages. Food Control 17 (2006) 900-904.

10. Burdurly H. S., Koca N. and F .Karadeniz: Degradation of vitamin C in citrus juice concentrates during storage. Journal of Food Engineering 74 (2006) 211-216.



7

11. Zerdin K., Michael L. R. and J.Vermue: The vitamin C content of orange juice packed in an oxigen scavenger material. Food Chemistry 82 (2003) 387-395.

12. www.wikkipedia.org 13. Kabasakalis V, Siopidou D. and E. Moshatou: Ascorbic acid content of commercial

fruit juices and its rate of loss upon storage. Food Chemistry 70 (2000) 325-328. 14. Gokmen V., Kahraman N., Demir N. and J. Acar: Enzymatically validated liquid

chromatographic method for the determination of ascorbic and dehydroascorbic acids in fruit and vegetables. Journal of Chromatography A, 881 (2000) 309-316.

15. Bylaw of quality and other conditions for aditives and their mixtures for food pro-ducts (Službeni list SRJ articles no. 56/2003, 4/2002 and 16/2005).

16. Blasco R., Esteve M. J., Frigola A. and M. Rodrigo: Ascorbic acid degradation kine-tics in mushrooms in a high-temperature short time process controlled by a thermo-resistometer. Lebensm.-Wiss. u.-Technol, 37 (2004) 171-175.

17. Vikram V. B., Ramesh M.N. and S.G. Prapulla: Thermal degradation kinetics of nu-trients in orange juice by electromagnetic and conventional methods. Journal of Food Engineering 69 (2005) 31-40.

18. Polydera A.C, Stoforos N.G. and P.S. Taoukis: Comparative shelf life study and vitamin C loss kinetics in pasteurized and high pressure processed reconstituted oran-ge juice. Journal of Food Engineering 60 (2003) 21-23.

УТИЦАЈ МЕТОДЕ КОНЗЕРВИСАЊА И УСЛОВА СКЛАДИШТЕЊА НА

ГУБИТАК АСКОРБИНСКЕ КИСЕЛИНЕ У ОСВЕЖАВАЈУЋИМ БЕЗАЛКОХОЛНИМ ПИЋИМА

Биљана Р. Цветковић и Марија Р. Јокановић

Светско тржиште је преплављено витамински обогаћеним производима, углав-ном освежавајућим безалкохолним пићима. Најчешће се производи обогаћују антиоксидантима, односно витаминима А, Ц и Е. Л-асакорбинска киселина у осве-жавајућим безалкохолним пићима врло брзо оксидише и разлаже се током скла-диштења, у зависности од услова чувања. Ова чињеница је од велике важности за потрошаче који треба да знају како да чувају и када да конзумирају освежавајућа безалкохолна пића (која су обогаћена аскорбинском киселином) у циљу максимал-не користи од додатог витамина Ц. Задатак овог рада је био мерење опадања кон-центрације витамина Ц у узорцима током различитих услова скледиштења. Осве-жавајуће безалкохолно пиће је припремљено у лабораторијским условима у складу са важећим Правилником, уз додатак синтетске Л-аскорбинске киселине. Током складиштења од 30 дана на температури од 4-8оС губитак аскорбинске киселине је 81.01- 97.83% у пастеризованом узорку пића, а у конзервисаном 90- 99%.

Received 17 November 2008 Accepted 26 February 2009

APTEFF, 40, 1-220 (2009) UDC: 664.5:66.061.3:582.28 DOI: 10.2298/APT0940009D BIBLID: 1450-7188 (2009) 40, 9-16


9

ANTIMICROBIAL ACTIVITY OF CARAWAY, GARLIC AND OREGANO EXTRACTS AGAINST FILAMENTOUS MOULDS

Gordana R. Dimić, Sunčica D. Kocić-Tanackov, Dušanka J. Pejin, Jelena D. Pejin,

Ilija J. Tanackov and Danijela Tuco Inhibitory effect of caraway, garlic and oregano extracts (0.07, 0.1, 0.5, 1 and 2%), against four moulds species was investigated. The caraway extract had the strongest in-hibitory effect by inhibiting the germination of Emericella nidulans, Penicillium com-mune and P. implicatum at the concentration of 0.1% and Aspergillus tamarii at the con-centration of 0.5% during 7 days of incubation at 25oC. The extract of garlic only parti-ally inhibited the growth of A. tamarii and P. commune. However, it inhibited completely the growth of P. implicatum and E. nidulans at the doses of 0.5 and 1%. Oregano parti-ally inhibited all mould species, significantly reducing the growth of colonies, especially of E. nidulans (93.3%). KEY WORDS: Spice extracts, antifungal activity

INTRODUCTION Moulds highly prevail in nature and frequently contaminate human food. Some of them produce secondary metabolites such as aflatoxins, ochratoxin A, stergmatocystine, which are cytotoxic and carcinogenic, and as such present a potential health hazard for humans (1). Medium moisture food (0.75-0.90 aw), low moisture food (< 0.75 aw) and sour food are especially susceptible to the presence of moulds. The development of mo-ulds on food can be expected in cases when inappropriate sanitary practice is applied in production plants. Moulds occur more frequently than other microorganisms on food pro-ducts during storage and distribution as a consequence of inadequate conditions. Essential oils extracted from spices and other herbs, as well as their biologically active components, have been intensively investigated for their potential role in the pro-tection of food from microorganisms, especially the foodstuffs with short shelf-life, such as bread, bakery products, cakes, salads, fresh fruits and vegetable, fish, etc. which are the most susceptible to microbial spoilage. Being natural antimicrobial agents, their usage Dr. Gordana R. Dimić, Assoc. Prof., [email protected], Sunčica D. Kocić-Tanackov, M.Sc., Assist., Dr. Dušanka J. Pejin, Prof., Dr. Jelena D. Pejin, Assist., Faculty of Technology, University of Novi Sad, Bulevar Cara Lazara 1, 21000 Novi Sad, Serbia; Dr. Ilija J. Tanackov, Assoc. Prof., Faculty of Technical Science, University of Novi Sad, Trg Dositeja Obradovića 6, 21000 Novi Sad, Serbia; Danijela Tuco, B.Sc. Etol JVE d.o.o., Bulevar Vojvode Stepe 40, 21000 Novi Sad, Serbia



10

can minimize the application of synthetic preservatives and additives, preserving simulta-neously food freshness and sensory quality. Preserving properties of spices and their extracts have been recognized long ago; their residues have been found on old Egyptian mummies (2) and there are evidence of their usage as antiseptic agents (3). Studies have shown that some spices like vanilla do not possess antifungal activity (4) whereas some of them have a stimulating effect (5, 6, 7, 8). This study was aimed at investigating the antifungal potential of caraway, garlic, and oregano extracts against some food-borne fungi.

EXPERIMENTAL

Materials Commercially available food grade ethanol extracts of caraway, garlic, and oregano were provided from Etol, Celje, Slovenia. Test cultures for antifungal investigations, As-pergillus tamarii, Emericella nidulans, Penicillium commune and P. implicatum were ta-ken from the culture collection of the Laboratory for Food Microbiology, Faculty of Technology in Novi Sad, isolated from food. The cultures were maintained on potato-dextrose agar (PDA) slants at 4º C.

Preparation of inoculum Prior to the experiment, moulds were cultured on PDA slants for 10 days until fully sporulated. Spores were taken by adding 10 ml of medium which contained 0.5% Tween 80 and 0.5% agar in sterile distilled water (4), scraped with sterile loop and aseptically transferred into sterile test tubes. Spore suspension obtained in this way was adjusted to final concentration of 2×106 spores/ml using the hemocytometer, and used for further work.

Antifungal test The inhibition of mould growth was determined by performing daily measurements of the radial growth of colonies cultured on PDA medium which contained spice extracts (each plate separately) in the following concentrations 0.07, 0.1, 0.5, 1 i 2% (v/v). For test moulds, PDA plates without any added material were made and used as control pla-tes. The solid plates were inoculated with spore suspension containing 1µl (103 spo-res/ml) in the centre of the medium and were incubated for 7 days at 25oC. Diameter of the growth was determined by averaging the radial growrth of the colony in two ortho-gonal directions. Each test was run in triplicate.

RESULTS AND DISCUSSION Inhibitory concentrations for caraway, garlic and oregano extracts against A. tamarii, E. nidulans, P. commune and P. implicatum are presented in Table 1.



11

Table 1. The inhibitory activities of spice extracts against moulds

Inhibition colony growth (%) Extract Conc. (%) A. tamarii E. nidulans P. commune P. implicatum

Caraway 0.07 12.7 20.0 14.8 11.1 0.1 22.2 33.3 37.0 77.8 0.5 47.6 100 100 100 1 100 100 100 100 2 100 100 100 100

Garlic 0.07 1.6 22.2 11.1 11.1 0.1 14.3 31.1 18.5 33.3 0.5 25.4 73.3 26.0 100 1 30.1 100 33.3 100 2 33.3 100 59.2 100

Oregano 0.07 12.7 11.1 14.8 5.5 0.1 17.5 15.5 18.5 11.1 0.5 30.1 31.1 22.2 16.7 1 47.6 48.9 29.6 55.5 2 79.4 93.3 74.1 66.7

As can be seen from data presented, the caraway extract exhibited the strongest inhi-bitory activity that was particularly expressed against E. nidulans and both Penicillium species (P. commune and P. implicatum) which did not grow at extract doses over 0.1%. At this level, the growth of P. implicatum was markedly reduced (77.8%). The level over 0.5% was needed to completely inhibit A. tamarii. The garlic extract at 0.5 and 1% concentrations inhibited only partially the growth of A. tamarii and P. commune and completely the growth of P. implicatum and E. nidulans. If compared to A. tamarii, stronger antifungal activity against P. commune was observed in all applied concentrations. The level of growth reduction in the presence of garlic ex-tract for A. tamarii ranged from 1.6 to 33.3% and for P. commune between 11.1 to 59.2%. Although none of the tested species was completely inhibited by the oregano extract, high concentrations were found to significantly inhibit the growth of colonies. The 2% extract inhibited almost completely (93.3%) the growth of E. nidulans. Against A. tamarii and P. commune, the same extract concentration exhibited approximately 70% inhibition rate (79.4 and 74.1%, respectively), whereas P. implicatum was found to be the least sen-sitive species. The effect of caraway, oregano and garlic extracts on the germination and growth rate of moulds is presented in Figures 1-3. At the concentrations 0.1 and 0.5%, the caraway extract delayed the beginning of ger-mination of A. tamarii by two and three days, respectively, as compared to the control. The appearance of the growth of E. nidulans and P. commune was not under the influ-ence by the increased extract concentration; however, the differences in their growth rate were noticed during the next days. At 0.1% concentration, colonies of P. implicatum be-came visible only on the sixth day after the inoculation of agar plates.



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Fig. 1. Effect of caraway extract on the growth of moulds

Fig. 2. Effect of garlic extract on the growth of moulds



13

The growth rate decline with increase of garlic extract contents in the agar medium was especially pronounced in the case of P. implicatum and E. nidulans, pointing to the greater sensitivity of these spesies (Fig. 2). Higher concentrations did not significantly influence the appearance of A. tamarii, whereas P. commune did not grow in the presence of 2% garlic extract until the fourth day. At lower levels of oregano extract (Fig. 3), the begining of germination was delayed by two days only in the case of P. implicatum, at the concentration of 0.5%. The 1 and 2% concentrations delayed the growth of P. implicatum by two and four days and E. ni-dulans by two and five days. The growth of A. tamarii and P. commune was delayed only at the concentracion of 2%, for three days. Stronger inhibitory effect on the growth rate of E. nidulans was noticed at the concentrations over 0.1% for A. tamarii and P. implicatum over 0.5% and at P. commune over 1%.

Fig. 3. Effect of oregano extract on the growth of moulds The increasing concentrations of caraway, garlic and oregano extracts caused the ab-sence or delay in germination of tested fungi, showing various inhibitory effects on the growth rate reduction. Caraway was more efficient at lower concentrations, compared to garlic and oregano. Moreover, it was the only extract to inhibit the growth of three spe-cies (out of the four tested) during the whole period of incubation (7 days) at 25oC. Pre-vious studies also reported strong inhibitory effect of caraway on Penicillium species. Studies have shown that P. aurantiogriseum, P. corylophilum, P. commune and P. griseo-fulvum were completely inhibited at 1% dose (8, 9). Antifungal properties of the tested extracts are due to their major constitutive com-ponents, carvacrol (from caraway and oregano), limonene (from caraway), thymol (from



14

oregano) and sulfur compounds (from garlic) (10, 11). Phenol compounds such as car-vacrol, thymol, eugenol, vanillin, geraniol and cinnamaldehyd are known antimicrobial agents (11-17). Phenolic OH-group is very reactive and easily forms hydrogen bonds with active sites in enzymes (6). According to Soliman and Badea (18), caraway showed inhibitory effect on Aspergillus flavus and A. parasiticus at 2000 ppm dose and on A. ochraceus and Fusarium moniliforme at 3000 ppm. Nielsen and Rios (4) showed that esential oils of mustard, garlic and clove are effective in preventing the growth of moulds usually present in bread. Garlic show antifungal activity against certain Aspergillus, Pe-nicillium and Fusarium species (19, 20). Guyenot et al. (3) investigated the protective effect of essential oils of 16 spices against xerophilic fungi from genera Eurotium, Asper-gillus and Penicillium, common spoilage organisms in bakery products. It was also re-ported that oregano extract is capable to completely inhibit Aspergillus parasiticus at the level of 2% in agar medium (6), which is in compliance with our results. Essential oils of cinnamon and oregano proved to be very effective in growth inhibition of Fusarium proliferatum (21).

CONCLUSION This study proved that the tested spice extracts can be potentially protective agents against filamentous fungi, frequent contaminants of food. Caraway extract exhibited high efficacy already at 0.5% dose. Garlic was the most effective against E. nidulans and P. implicatum. Oregano exhibited strong inhibitory effect although was unable to comple-tely inhibit the fungal growth.

REFERENCES

1. van Egmond, P.H.: Mycotoxins: detection, reference materials and regulation, in Introduction to food- and airborne fungi. Eds. R.A. Samsin, E.S. Hoekstra and J.C. Frisvad, Ponson & Looyen, Wageningen, Utrech, Netherlands (2005) pp.332-338.

2. Silliker, J.H., R.P. Elliott, A.C. Bairol-Barker, F.L. Bryan, J.H.B. Christian, D.S. Clark, J.C. Olson and Jr.T.A. Roberts: Microbial Ecology of Foods. Vol.II, Academic Press, New York, London (1980).

3. Guynot, E.M., J. A. Ramos, L. Seto, V. Purroy, V. Sanchis and S. Marin: Antifungal activity of volatile compounds generated by essential oils against fungi commonly causing deterioration of bakery products. J. Appl. Microbiol. 94 (2003) 893-899.

4. Nielsen, V.P. and R. Rios: Inhibition of fungal growth on bread, by volatile com-ponents from spices and herbs, and the possible application in active packaging, with special emphasis on mustard essential oil. Int. J. of Food Microbiology 60 (2000) 219-229.

5. Mabrouk, S.S. and M.A.N. El-Shayeb: Inhibition of aflatoxin formation by some spices. Z. Lebensm. Unters. Forsch. 171 (1980) 344-347.

6. Özcan, M.: Inhibitory effect of spices extracts on the growth of Aspergillus para-siticus NRRL2999 strain. Z. Lebensm. Unters Forsch A 207 (1998) 253-255.

7. Boyraz, N. and M. Özcan: Antifungal effect of some spice hydrosols. Fitoterapia 76 (2005) 661-665.



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8. Dimić, G. and S. Kocić-Tanackov: Antifungal activity of spices extracts on the growth of Penicillium commune and Penicillium griseofulvum, 6th Congress of Medi-cal Microbiology, Beograd, 11-14 June 2008, Book of Abstracts, pp. 335-336.

9. Dimić, G., S. Kocić-Tanackov and D. Karalić: Inhibitory Effect of Spice Extracts on Growth of Penicillium aurantiogriseum and Penicillium corylophilum, 54th Interna-tional Meat Industry Conference, Vrnjačka Banja, 18-20 June 2007, Book of Abs-tracts, p. 89.

10. Baratta, M.T., H.J.D. Dorman, S.G. Deas, D.M. Biondi and G. Ruberto: Chemical composition, antimicrobial and antioxidative activity of laurel, sage, rosmary, orega-no and coriander essential oils. J. Essent. Oil Res. 10, 6 (1998) 618-627.

11. Ceylon, E. and C.Y. D. Fung: Antimicrobial activity of spices. J. Rapid. Meth. Au-tom. Microbiol. 12 (2004) 1-55.

12. Bullerman, L.B., F.Y. Lien and S.A. Seir: Inhibition of growth and aflatoxin pro-duction by cinnamon and clove oils, cinnamic aldehyde and eugenol. J. of Food Sci-ence 42 4 (1977) 11007-1116.

13. Hitokoto, H., S. Morozumi, T. Wauke, S. Sakai and H. Kurata: Inhibitory effects of spice on growth and toxin production of toxigenic fungi. Appl. Environ. Microbiol. 39 4 (1980) 818-822.

14. Moleyar, A.V. and P. Narasimham: Antifungal activity of some essential oil com-ponents. Food Microbiol. 3 (1986) 331-336.

15. Mahmound, A.L.E.: Antifungal action and antiaflatoxigenic properties of some essen-tial oil constituents. Lett. Appl. Microbiol. 19 (1994) 110-113.

16. Matamoros-Leon, B., A. Argaiz and A. Lopez-Malo: Individual and combined effects of vanillin and potassium sorbate on Penicillium digitatum, Penicillium glabrum, and Penicillium italicum growth. J. Food Protect. 62 5 (1999) 540-542.

17. Moriera, M.R., A.G. Ponce, C.E. del Valle and S.I. Rouza: Inhibitory parameters of essential oils to reduce a foodborne pathogen. LWT 38 (2005) 565-579.

18. Soliman,K.M. and R.I. Badeaa: Effect of oil extrated from some medicinal plants on different mycotoxigenic fungi. Food Chem. Toxicol. 40 (2002) 1669-1675.

19. Mei-chin, Y. and T. Shih-ming: Inhibitory effect of seven Allium plants upon three Aspergillus species. Int. J. Food Microbiol. 49 (1999) 49-56.

20. Benkeblia, N.: Antimicrobial activity of essential oil extracts of various onions (Alli-um cepa) and garlic (Allium sativum). LWT 37 (2004) 263-268.

21. Velluty, A., V. Sanchis, A.J. Ramos, J. Egido and S. Marin: Inhibitory effect of cin-namon, clove, lemongrass, oregano and palmarose essential oils on growth and fumo-nisin B1 production by Fusarium proliferatum. Int. J. Food Microbiol 89 (2003) 145-154.



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АНТИМИКРОБНА АКТИВНОСТ ЕКСТРАКАТА КИМА, БЕЛОГ ЛУКА И ОРИГАНА НA ФИЛАМЕНТОЗНЕ ПЛЕСНИ

Гордана Р. Димић, Сунчицa Д. Коцић-Танацков, Душанка Ј. Пејин, Јелена Д. Пејин,

Илија Ј. Танацков и Данијела Туцо Инхибиторнa активност екстраката кима, белог лука и оригана (0,07, 0,1, 0,5, 1 и 2%) је испитивана против четири врсте плесни. Екстракт кима је имао најјачи инхибиторни ефекат спречавајући герминацију Emericella nidulans, Penicillium com-mune и P. implicatum при концентрацији од 0,1% и Aspergillus tamarii при концен-трацији од 0,5% током седам дана инкубирања на 25°C. Екстракт белог лука је само парцијално инхибирао раст А. tamarii и P. commune и потпуно P. implicatum и Е. nidulans при концентрацијама 0,5 и 1%. Оригано је парцијално инхибирао све че-тири врсте плесни, али је раст колонија био значајно смањен, нарочито код Е. nidulans (93,3%).

Received 24 July 2009 Accepted 14 September 2009

APTEFF, 40, 1-220 (2009) UDC:664.64.016.71.8:664.641.15+664.641.2:664.696 DOI: 10.2298/APT0940017D BIBLID: 1450-7188 (2009) 40, 17-24


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PROPERTIES OF EXTRUDED SNACKS SUPPLEMENTED WITH AMARANTH

GRAIN GRITS

Ljubica P. Dokić, Marija I. Bodroža-Solarov, Miroslav S. Hadnađev and Ivana R. Nikolić

Extruded amaranth grain products have specific aroma and can be used as snack food, supplement in breakfast cereals, or as raw material for further processing. Extru-ded products of corn-amaranth grits blends, containing 20% or 50% amaranth grain grits, were produced by extrusion-cooking using a laboratory Brabender single screw extruder 20 DN. Extrudates with various texture were obtained. During extrusion process starch granules are partially degraded, hence rheological properties were examined. All samples exhibited thixotropic flow behavior. Those sam-ples in which part of the corn grits was replaced with amaranth one had lower viscosity and exhibited lower level of structuration during storage. KEY WORDS׃ Amaranth, extrudate, proteins, starch, rheological, properties

INTRODUCTION Amaranth grain has significant nutritional value. Its protein, mineral meters, fat and cellulose percentage are higher compared to cereals (1, 2). Since this plant has similar application as cereals, it is classified as pseudocereal (2). The origin of Amaranthus sp. is from middle and south America, but for the last few decades this cultivar was introduced in European countries as Austria, Poland, Hungary, Serbia and Montenegro (2, 3). Extruded amaranth grain products have specific aroma and can be used as snack food, supplement in breakfast cereals, or as raw material for further processing (4). Sanches–Marroquim et al. investigated extruded blends of Amaranth with wheat and outs flour. The optimal combination of these components, to their opinion is 5050׃, or 6040׃, res-pectively (5). Starch is an important industrial raw material for food products as well as for techni-cal products. Corn starch is relatively easily isolated by wet-milling procedure. Amaranth

Dr. Ljubica Dokić, Assoc. Prof, [email protected], Faculty of Tehnology, Bulevar Cara Lazara 1, 21000 Novi Sad, Serbia; Dr. Marija Bodroža-Solarov, Miroslav Hadnađev, M. Sc. Institute for Food Technology, Bulevar Cara Lazara 1, 21000 Novi Sad, Serbia; Ivana Nikolić, B. Sc., Faculty of Tehnology, Bulevar Cara Lazara 1, 21000 Novi Sad, Serbia



18

starch is interesting because of its small granular size, 1–2 μm, which provides specific functional properties, as good freeze–thaw stability and resistance to mechanical shear. Amaranth starch content is approximately 63%, while protein content is 15%. The starch has „waxy” characteristics and specific molecular composition, while proteins have high quality and major content of S–amino acids and lysine (6). There is no effective and easy method to isolate the starch from amaranth seed be-cause of its small granules and high protein content. Considering the fact that starch and protein are of high quality, some other methods were developed, like dry milling and separation or extrusion process with the aim to provide products useful for food or non-food purposes. During extrusion process, properties of native starch granules are modi-fied and pregelatinized starch with changed rheological characteristics is obtained (7). Numerous products with starch undergo thermal treatments during production and application, when starch gels with specific rheological characteristics are formed. Mo-dification of rheological properties can be achieved by mixing different starches. The aim of this work was to investigate rheological characteristics of gels of amaranth and corn grits blends, before and after extrusion process.

EXPERIMENTAL Amaranth and corn were acquired from local commercial sources. Grits was obtained by milling whole grain in laboratory mill (Bühler 202, Germany). Blends were prepared in the following ratios: amaranth:corn, 20:80, 50:50 and 0:100, respectively. Particle size distribution of grits is presented in Table 1.

Table 1. Particle size distribution of corn and amaranth grits

Grits blends were extruded using a laboratory Brabender single screw extruder 20 DN. Before extrusion, the moisture content of the grits was adjusted to 16%. Such mois-ture content enables optimal extrusion conditions. It was fed to the extruder under the following conditions׃ Compression ratio 41׃ Temperature of the first zone 120°C Temperature of the second zone 130°C Temperature of the third zone 160°C Die diameter 3 mm Screw speed 120 rpm The extruded product (flips) was analyzed for moisture (AOAC,1984, 8), bulk density and expansion ratio.

Fractions remained on sieves of particular size, (%) Sample 850 μm 650 μm 450 μm 350 μm 250 μm Corn grits 1.2 44.1 50.3 3.7 0.7 Amaranth grits 0.8 43.0 41.2 9.0 6.0



19

Extrudate density was calculated. Six products were randomly selected, weighted (m) and measured (L, D), and the density was calculated as follows:

Density = LDπ

m42

××

×

where m is the mass, L – length of cooled extrudate with the diameter D (9). Expansion ratio was calculated as the ratio of the diameter of extruded simple to that of the extruded die. Density and expansion ratio are given as average value of six calculations. Statistical Analysis. Analysis of variance (ANOVA) and least significant differen-ces (LSD) were performed by the Statistical Analysis System (Statistical, Tulsa, Oklaho-ma, USA). Strength, hardness and plasticity were determined on a universal instrument for tex-ture analysis INSTRON 4301. Determination of hardness was performed with head with 1.6 mm diameter running at speed of 60 mm/min. Softness of sample by cutting was examined using knife with 1 mm blade and at head speed of 60 mm/min. Probe for com-pression with 30 mm diameter was used to examine the force needed to compress extru-date from 1 cm length to 0.5 cm at the Instron head speed of 48 mm/min. The measu-rements were performed in the six replicates and average value for strength, hardness and plasticity were calculated. The gels for rheological measurements were obtained by heating 6.25% suspension of grits, in a Brabender viscoamylograph up to 95°C and then held at 95°C for 30 min. Gels were made from grits blends as well as from extruded products milled to grits on a laboratory mill. The obtained paste was cooled to room temperature and rheological mea-surements of the gels were carried out at 20°C. Measurements were carried out right after the cooling (0h) and 24 hours later (24h). Rheometer RheoStress 600HP (Haake, Ger-many) with measurement set plate–plate (PP60Ti), with 60 mm diameter and 1 mm dis-tance, was used. Flow curves were obtained by hysteresis loop method by the following cycle: ramp up 0-500 1/s in 4 min constant γ 500 1/s in 2 min ramp down 500-0 1/s in 4 min. Micrographs were taken on a scanning electron microscope (JEOL–JSM–6460LV).

RESULTS AND DISCUSSION Results of the determination of expansion index and density of extrudates are presen-ted in Table 2. The initial moisture level drop from 16% to the final average level of 7.5% for extru-dates, was within the expected range of 4-8%, reported by Koeppe (1987) as characte-ristic for an extruded snack products. The difference in moisture content of extrudates is not statistically important (Table 2).



20

Table 2. Extrudate properties

Sample Moisture content (%) (db) Expansion index Density (g/cm3)

100% corn grits 7.6 ± 0.09a 4.03 ± 0.21a 0.095 ± 0.02a 80% corn : 20% amaranth grits 7.4 ± 0.03a 2.83 ± 0.11b 0.132 ± 0.01b 50% corn : 50% amaranth grits 7.6 ± 0.05a 1.83± 0.18c 0.346± 0.04c

Results are mean ± SD of six measurements a Means with different letters in the same column for each sample are significantly different at the 5% level Addition of amaranth grits to extrusion blend proportionally reduced extrusion index and increased density of extrudates, due to its reduced expansion properties compared to corn. Reduced expansion resulted in a denser product with smaller air cell diameters as shown in Figure 1.

Fig. 1. Scanning electron micrographs of amaranth:corn 50:50 (A) and corn extrudate (B) It is difficult to produce expanded products by extrusion cooking of amaranth grain alone, due to its high fat content (6-8% in whole grain). Fat provides a powerful lubricant effect in extrusion cooking and reduced product expansion (11). Flips of 100% corn grits have the highest expansion (4.03) and lowest density (0.095 g/cm3), which provides demanded crispy structure during eating. Blend of 50% corn and 50% amaranth grits resulted in a decreased expansion index (1.83) compared to control 100% corn grits by 2.2 times, but in increased density (0.346 g/cm3 ) by 3.6 times.

Table 3. Texture of extrudates measured by Instron 4301 Sample Compression force

(N) Penetration force

(N) Cutting force

(N) 100% corn grits 13.2 ± 0.23a 3.2 ± 0.09a 19.2 ± 0.20a 80% corn : 20% amaranth grits 20.8 ± 0.32b 5.1 ± 0.11b 18.8 ± 0.18a 50% corn : 50% amaranth grits 24.5 ± 0.15b 11.6 ± 0.08c 18.4 ± 0.14a

a Means with different letters in the same column for each samples are significantly different at the 5% level Table 3 represents the differences in compression, penetration and cutting force (N) for the extrudate with amaranth grits supplement compared to the control with 100% corn



21

grits. Increasing the amount of amaranth grits in flips increased the resistance of extru-dates, thus the difference in force for compression and penetration compared to corn grits flips is significant. Cutting force which imitates biting, is not statistically much different among treatments. Hardness of flips with 50% amaranth grits represented by penetration force (11.6 N) is by 3.6 times higher than the penetration force for sample with 100% corn grits (3.2N), which is a major difference. Generally, the addition of grits from whole amaranth grain, as a fiber–rich raw ma-terial in extruded product formulations, resulted in increased density and hardness of the product (12). Figure 2 presents flow curves of gels obtained from corn grits and blends of corn and amaranth grits in the ratios 80:20 and 50:50, determined immediately after the prepara-tion and after 24h. All systems exhibited thixotropic flow behavior. Gels prepared from corn grits had the greatest value of shear stress, i.e. viscosity, and largest thixotropic loop area. The structure is weak and it was broken–down by low share rates. During storage for 24h the system with 100% corn grits is additionally structured and three–dimensional gel structu-re is formed as a result of retrogradation of amylase fractions. Since retrogradation is a process of binding by weak hydrogen bonds that are easily broken, the flow curve for 100% corn grits measured after 24 hours shows a peak characteristic for breaking such structures down at very low shear rates. Gels of examined grits blends had lower viscosi-ty than corn grits and during storage they did not build additional structure. This is a re-sult of replacing part of the corn grits, whose starch contains amylose and amylopectin, with amaranth grits whose starch includes small amount of amylose and high amount of amylopectin fractions (13).

0 100 200 300 400 5000

20

40

60

80

100

120

τ (P

a)

γ (1/s)

B B B

0 100 200 300 400 5000

20

40

60

80

100

120

140

τ (P

a)

γ (1/s)

### ### ###

Fig. 2. Flow curves of the gels from corn grits and corn–amaranth grits in the ratios 80:20

and 50:50 determined in 0 h and 24 h



22

In such a way fraction which structurate during time (amylose) is partially replaced by non gelling fraction. Increased amount of amaranth grits decreased viscosity and sur-face of thixotropic flow curves. From the flow curves, in Figure 2, fitting data in Herschel–Bulkley equation (14): • τ = τ 0 + k γn

the values for yield stress τ0 and coefficients k and n were calculated. Yield stress decreased with addition of amaranth grits, as part of the corn was replaced. Also, values of yield stress τ0 increased for gel samples after 24 hours of storage due to the struc-turation. Values of viscosity behavior index n for all samples are smaller than 1, which is characteristic for thixotropic behavior.

Table 4. Values of yield stress, consistency index and viscosity behavior index

Yield stress τo (Pa)

Consistency index k

Viscosity behavior index n

Sample

0h 24h 0h 24h 0h 24h 100% corn grits 3.97 4.59 2.78 10.46 0.59 0.38 80% corn : 20% amaranth grits 1.96 2.75 2.49 6.75 0.57 0.41 50% corn : 50% amaranth grits 0.72 0.92 2.89 3.93 0.52 0.44 100% corn extrudate 0 0.57 0.30 12.59. 0.72 0.21 50% corn : 50% amar. extrudate 0 0 0.05 0.05 0.06 0.06

0 100 200 300 400 5000

20

40

60

80

100

120

τ (P

a)

γ (1/s)

100% corn extrudate corn/amaranth 50:50% extrudate 100% corn grits corn/amarnth 50:50%

Fig. 3. Flow curves of the gels made from the corn grits and extruded snack, and from

50:50% corn:amaranth grits and extruded snack

Fig 3 presents flow curves of corn grits and grits blends of corn and amaranth in a ratio 50:50, as well as flow curves of obtained extrudated products. Flow curves of gels made from extrudates had lower viscosity than the gels made from corresponding grits.



23

Starch granules in extrudates after thermal treatment were partly damaged during extrusion process and they built weak gels. The obtained pastes had a lower viscosity, and they can be classified to the category of pregelatined starch granules.

CONCLUSION

Increasing amount of amaranth grits in the extrusion blend causes increase of density and hardness of the extrudated products and decrease in expansion index. When part of the corn grits is replaced with amaranth grits viscosity of gels decreases compared to pure corn grits. Also, extrusion process partially damages starch granules, thus obtained gels of extrudated products have lower viscosity than the initial grits.

REFERENCES

1. Saunders, R.M., and R. Becker: Amaranthus: A Potential Food and Feed Recourse in: Advances in Cereal Science (1984) 357-396.

2. Bodroža–Solarov, M.: Effects of Genotype and Sowing Date on Yield and Yield Components of the Genus Amaranthus L, Ph.D.Thesis, Faculty of Agriculture, Uni-versity of Novi Sad (2001) 1-113.

3. Kovacs, E.T., Maraz–Szabo, L., J. Varga: Influence of Variety and Type of Emulsi-fier for Functional Food Quality and Amaranth Basis, Proceedings of XIV Internatio-nal Congress „Cereal Bread 2000” (2001) 223-226.

4. Breene, W.M.: Food Uses of Grain Amaranth, Cereal Food World 36, 5 (1991) 426-429.

5. Sanchez–Marroquan, A., Del Valle, F.R., Escobedo, M., Avita, R., Maya, S., and M. Vega: Evaluation of whole amaranth (Amaranthus cruentus) flour, its air classified fractions, and blends of these with wheat and outs as possible components for infant formulas, J. Food Sci. 51, 5 (1986) 1231-1234.

6. Radosavljević, M., Jane J., L.A. Johanson: Isolation of Amaranth Starch by Diluted Alkaline–Protease Treatment, Cereal Chem. 75, 2 (1998) 212-216.

7. Gonzales, R. J., Torres R. L., De Greef, D. M., Tosi E., E. Re: Brazilian Journal of Chemical Engineering 19, 4 (2002) 391-395.

8. AOAC : Solids (total) and moisture in flour. Air oven method. In Official Methods of Analytic Chemists, 14th edn. (1984) pp. 249.

9. Ding Q., P. Ainsworth, A. Plunkett, G. Tucker, H. Marson: The Effects of Conditions on the Functional and Physical Properties of Wheat–Based Expanded Snacks, Journal of Food Engineering 73 (2006) 142-148.

10. Koeppe, S. J., Harris, M.A., Hanna, J. H., Rupnow, C. E. Walker, and S.L. Cupett: Physical Properties and Some Nutritional Characteristics of an Extrusion Products with Defatted Amaranth Seeds and Defatted Maize Gluten Meal (80:20 Ratio), Cereal Chemistry 64, 4 (1987) 332-336.

11. Ilo, S., Liu Y., E. Berghofer: Extrusion Cooking of Rice Flour and Amaranth Blends, Lebensm.–Wiss.u.–Technol. 32 (1999) 79-88.

12. Onwulata, C. I., Konstance R. P., Strange E. D., Smith P. W., V.H. Holsinger: High Fiber Snack Extruded from Triticale and Wheat Formulations, Cereal Food World 45, 10 (2000) 470-473.



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13. Bello–Perez, L. A., Colona, P., Roger, P., O. Peredes–Lopez: Macromolecular Fea-tures of Amaranth Starch, Cereal Chem. 75, 4 (1998) 395–402.

14. Mezger T. : The Rheology Handbook, Vinsentz Verlag, Hannover (2002) pp.46.

СВОЈСТВА ЕКСТРУДАТА СА ДОДАТКОМ КРУПИЦЕ ОД СЕМЕНА АМАРАНТУСА

Љубица П. Докић, Марија И. Бодрожа-Соларов, Мирослав С. Хаднађев

и Ивана Р. Николић Поступком екструдирања на лабораторијском Брабендеровом 20 ДН екструдеру добијени су екструдати мешавине кукурузног гриза са додатком 20% и 50% кру-пице од семена амарантуса. Добијени су екструдати различите текстуре. Пове-ћањем удела гриза од амарантуса у смеши за екструдирање долази до повећања густине, смањења степена експанзије, повећања тврдоће. У процесу екструдирања долази до делимичног оштећења скробне грануле те су испитане и реолошке карак-теристике. Сви системи су по типу протицања били тиксотропни. Узорци код којих је део кукурузне крупице замењен амарантусовом имали су ниже вискозитете и по-казивали низак степен просторног структурирања током стајања.

Received 15 June 2009 Accepted 9 September 2009

APTEFF, 40, 1-220 (2009) UDC:664.71-11:664.762:66.012 DOI: 10.2298/APT0940025F BIBLID: 1450-7188 (2009) 40, 25-34


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REDUCTION OF WHEAT MIDDLINGS USING A CONVENTIONAL AND EIGHT-ROLLER MILLING SYSTEMS

Aleksandar Z. Fišteš and Đuro M. Vukmirović1

Possibilities for the rationalization of the wheat flour milling process using the eight-roller mill on the 1M and 2M passages of the reduction system have been investigated. At the same roll gaps and under the same sieving conditions, the lower flour yield has been obtained using an eight-roller mill compared to the conventional milling system (5-8 %) followed by a higher energy requirements for grinding. By decreasing the roll gap setting and increasing the upper size limit of flour in the process with the eight-roller mill it is possible to increase flour yield and therefore decrease milling energy consumption per unit mass of flour produced without deterioration of flour quality as determined by ash content. With appropriate adjustments of the processing parameters in the eight-roller milling system it is possible to achieve similar milling results to those in the conventional system, while the overall investment, energy and maintenance costs are significantly lower. KEY WORDS: Wheat flour milling, process rationalization, eight-roller mill

INTRODUCTION

The objective of the wheat flour milling process is to separate the branny cover and germ of the wheat kernel from the endosperm and achieve as high as possible flour extraction with the lowest contamination of bran and germ that increase the ash content. Breaking the wheat kernel is affected by corrugated cast steel rolls that gradually separate the endosperm, bran and germ. Reduction of relatively pure endosperm to flour is achie-ved by using smooth rolls. Segregation between the kernel parts occurs in plansifters, where sieves separate particles of different size, and in purifires, where sieves and air-flow separate particles of different size, specific gravity and shape (1). Ever since the grinding of grain has been known to the mankind, possibilities and solutions have been sought out in order to simplify the grinding process and make it more efficient. New concepts and ideas only have chance of being successful if the yield as well as the quality of the finished products are not affected and requirements such as reduction of investment, operating and maintenance cost are met (2). The traditional Aleksandar Z. Fišteš, M.Sc., [email protected], Faculty of Technology, Bulevar Cara Lazara 1, 21000 Novi Sad, Serbia; Đuro M. Vukmirović, B.Sc., [email protected], Institute for Food Technology, Bulevar Cara Lazara 1, 21000 Novi Sad, Serbia



26

wisdom in flour milling is that after every grinding step the ground material should be sieved and the undersize material removed before regrinding (3). Over the years the main equipment used in the grinding system has been redesigned to such an extent that it has been possible to multiply the throughputs of these machines but flour process technology has not changed fundamentally since the introduction of the roller mill, the purifier and the plansifter (4). This is the reason why the double grinding of intermediate streams before sieving has been one of the most notable process developments in flour milling (3). Eight-roller mill (a total of 8 rolls in one housing) provides two grinding passages without any intermediate sifting. Compared to a conventional process with the four-roller mill, the introduction of the eight-roller mill into the milling flowsheet offers the following advantages (2, 4, 5-8):

• fewer pneumatic suction lifts (conveying the stock from the roll to the sifter) – resulting in lower material and installation costs

• lower pneumatic system air requirements – resulting in lower energy costs and lower filter surface requirements for cleaning the pneumatic conveying air

• reduction of sifter surface • smaller number of roll stands • less spouting and auxiliary components • lower space requirements for equipment installation – resulting in lower building

costs for the new milling plants or increase in grinding capacity within existing limited building space

• more compact building design makes it easier to keep clean with less area to fumigate

• with less equipment there is less cleaning and maintenance. On the other hand, twin stage grinding ignores the milling principle that, after grin-ding, coarse material is separated from the fines and therefore the conditions for con-trolled milling are less favorable. The decision as to how many double grinding passages can be applied in the flowsheet depends directly on the finished products to be made. It is not always possible to equip installations exclusively with eight-roller mills (4, 8). This is the reason why it is very important to define the passages and optimal roll parameters that allow the introduction of the eight-roller mill into the milling process without deterio-ration of the yield and quality of finished products. Even though the eight-roller mill has found its place in the modern flour milling process relatively little research has been performed on various factors affecting the milling results using this technique mainly focusing on the front passages of the break system (8-11) rather than the passages of the reduction system. It is evident that when the first and second breaks are combined into a twin passage, the particle size distribution of the stock will not be the same as with conventional single break system (2, 8, 11). There are several disadvantages of using this break system. First, it grinds fine material, coarse middlings, that should not pass to the next break roll, whose function is to separate endosperm from bran. Second, it produces more break flour and fine middlings and less coarse middlings and sizings that can be purified to produce clean middlings and low-ash flour. Third, the capacity of the lower roll is limited because the ground material is lower in density, which increases the volume to the roll (5). Tegeler (8) and Wanzenried (7)



27

stated that the granulation from flour produced in the eight-roller mill is finer while the flour color is slightly whiter compared to the ones in the conventional process. The research of Zwingleberg (9) and Zwingleberg and Artz (10) showed that appropriate adjustment of the roll parameters is needed regardless of whether the eight-roller mill is used on breakage or reduction passages. Under industrial conditions, only the roll gap settings and feed rate (to a limited degree) can be adjusted during the milling process. The aim of this work was to examine and compare the effect that roll gap changes have on the milling results (degree of particle size reduction, flour release, flour ash and milling energy requirements) obtained using the conventional process and process with an eight-roller mill employed on the 1st and 2nd midds (1M and 2M passages) of the reduction system.

EXPERIMENTAL

The samples were obtained from an industrial mill (120 t/day) intercepting the stream (middlings) that would have been sent to the 1M. In this particular mill (having five break, four sizing and six reduction passages) the eight-roller mills are not employed. The samples (50 kg) were separated using the automatic sampler divider (Gompper-Maschi-nen KG) into 0.5 kg batches and milled on a Variostuhl (model C Ex 2) – laboratory roll stand (Miag). Smooth rolls 0.1 m in length and 0.25 m in diameter were used. Table 1 summarizes the experimental range of variables tested. The experiments were designed to compare:

a.) conventional milling system – the entire stock following 1M was sieved for 3 min on a Bühler laboratory sifter (model MLU-300) and the part of the stock held on the sieve fitted with 150 μm bolting cloth was milled on 2M

b.) eight-roller milling system – the entire stock following 1M was milled on the 2M without intermediate sifting

Table 1. Summary of experimental range of variables tested

Milling system

Roll surface

Roll gap combinations

[mm]

Feed rate [kg/cm/min] Differential

Fast roll speed [m/s]

Conventional 1M-0.20; 2M-0.15*

Eight-roller

Smooth 1M-0.10; 2M-0.08 1M-0.10; 2M-0.05 1M-0.08; 2M-0.05 1M-0.20; 2M-0.20

1.25 5

*The slower feed rate on 2M corresponds to the amount of flour removed by intermediate sifting of the stock leaving 1M Sieve analysis of the entire stock following 2M was performed on the above Bühler laboratory sifter for 3 min. For the conventional milling system the sieve openings were 250, 200 and 150 µm, along with the bottom collecting pan. For the eight-roller milling system three different stacks of sieves were used. The first stack was the same as that mentioned above. In the second, the sieve with the 150 µm bolting cloth was replaced



28

with a sieve having 180 µm bolting cloth, and for the third stack the sieve openings were 250 and 200 µm. Two samples were milled and sieved under the same conditions. The weight distri-bution among the streams was highly reproducible. Based on the 3σ rule, the 99.7% esti-mated confidence interval for the data (weight percentages) presented in the paper is ±0.37%. Flour yield F (%) in the eight-roller and conventional milling systems was calculated from Equations (Eqs.) [1] and [2], respectively.

(%)100*(%) 2M

mF M= [1]

(%)100*(%) 21M

mmF MM += [2]

The symbols m and M stand for the weights of the flour and native feed, respectively. The subscripts indicate flour following 1M or 2M. The ash content of the total quantity of flour leaving the 2M was determined according to ICC standard method No.104/1 (12). The milling energy consumption during all grinding runs was determined from the wattmeter fitted as an integral part of the Variostuhl laboratory roll stand. Two different power readings were recorded corresponding to operation with (P, kW) and without (P*, kW) the material flow. The milling energy consumption, E kJ/kg, in the conventional and eight-roller milling systems was calculated by Eqs. [3] and [4], respectively.

MM

MMM

M

MM tm

PPt

mPP

E 22

*22

11

*11 −+

−= [3]

)()()(

212

*22

*11

MMM

MMMM ttm

PPPPE +

−+−= [4]

Here m (kg) is the mass of flour obtained and t (s) is the time of the grinding run determined by the chronometer. The significance of the differences between milling results obtained using investigated milling systems have been tested by the paired Stu-dent’s t-test.

RESULTS AND DISCUSSION

Changes in the particle size distribution of the stocks leaving 2M, brought about by the decrease of the roll gap, followed the same trends in both milling systems. Con-sidering that the 2M feeds were different for the two milling systems, yields of the size fractions of the milling output are not to be compared because the cumulative size distri-butions (Fig. 1a and 1b) were given relative to the mass of the material milled on the 2M and only serve to show the general trends. By decreasing the roll gap, the quantity of ma-terial >200 μm (size fractions >250 μm and 250/200 μm) tends to decrease while the flour yield (



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Fig. 1. Cumulative size distributions of the stocks following 2M milled through different

roll gaps in the a) conventional milling system and b) eight-roller mill system The factors affecting particle size reduction can be classified into those arising from the physicochemical properties of the material and those related to the design and operation of the milling equipment (13). In a roller mill particles are subjected to shear and compressive forces. The nature of deformation depends not only on the applied stresses but also on the particle components upon which the stresses act. Compressive stresses are more effective in causing the disintegration of the brittle endosperm material while bran (tough and fibrous) is more prone to the ductile fracture imparted by shear forces. The roll parameters such as roll gap, uniformity and the feed rate of stocks to rolls, roll velocities, differential and the type and condition of roll surface influence the magnitude of the stress and the relative contributions of compressive and shearing forces (14). Middlings are composed primarily of endosperm (they also contain adhering bran and germ) exhibiting viscoelasticity when fracturing. With roll differential closer to 1 the compressive forces dominate in the grinding zone. As the roll differential increases, greater shear stresses are imposed. Under the present grinding conditions, using the smooth rolls and relatively small differential – 1.25 (usual for this stage of grinding pro-cess), as the roll gap decreases greater compressive forces are imposed, thereby increa-sing the number of endosperm fractures creating more flour. Simultaneously, the tougher branny particles are flattened and remain in the coarsest size fractions of the milling output (>200 μm). In addition to that, decreasing the roll gap increases the grinding zone size (14) so the grinding action, under predominant compressive forces, is prolonged and also contributes to the greater flour release as a result of increased number of endosperm fractures. Ash is concentrated in the bran, with over half the total in the pericarp, testa and aleurone and the ash content increases from the inner (endosperm) to the outer (bran)



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part of the wheat kernel (15). The increase of the ash content of the coarsest fraction of the stock following 2M, while roll gap had no influence on flour ash content (Table 2), proves that bran particles remain intact. Scanlon and Dexter (16) and Scanlon, Dexter and Biliaderis (17), in their studies of the effect of smooth roll grinding conditions on reduction of wheat farina, also reported similar findings.

Table 2. Ash content in flour (250 μm) of the stock following 2M in the conventional and eight-roller milling systems

Ash content (%)dm

Conventional system Eight-roller system Roll gap [mm] >250 μm 250 μm



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These particles take on some of the stresses in the grinding zone which otherwise would be used to reduce the remaining middlings to flour, thereby explaining the lower flour release in the process with the eight-roller mill as well as the finer flour granulation as a result of further grinding of flour particles. Only one sifting operation in the process with eight-roller mill, compared to two in the conventional system, also contributed to lower flour yield. The amount of the flour in the stock following

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