The rate of freezing and the formation of small ice crystals in freezing are critical to reduce tissue dam- age and drip loss in fruit thawing. Different types of freezing systems are designed for foods. The se- lection of suitable freezing systems is dependent on the type of product, the quality of frozen product, desire, and economical reasons. Freezing systems are divided according to the material of the heat- transmission medium (Rahman, 1999):
1. Freezing by contact with cooled solid or plate freezing: The product is placed between metal plates and then adjusted by pressure. This method is used for block or regular form products. 2. Freezing by contact with cooled liquid or immer-
sion freezing: The fluids usually used are sodium chloride solutions, glycol and glycerol solutions, and alcohol solutions.
3. Freezing with a cooled gas in cabinet or air-blast freezing: Air-blast freezing allows quick freez- ing by flowing cold air (−40◦C) at relatively high speed between 2.5 and 5 m/s.
4 Fruit Freezing Principles 75 4. Cryogenic freezing: Food is frozen by direct con-
tact with liquefied gases, nitrogen and carbon dioxide. Nitrogen boils at−195.8◦C and the sur- rounding food temperature reaches temperatures below −60◦C. This is a very fast method of freezing and the rapid formation of ice crystals reduces the damage caused by cell rupture, pre- serving sensorial and nutritional characteristics. Cryogenic freezing is recommended for cubes, slices, medium or small whole fruits but is not ap- propriate for whole medium and large fruits such as prunes, peaches, etc., due to the risk of crushing.
FUTURE PERSPECTIVES
Irradiation. Ionizing radiation has been used as a safe and effective method for eliminating bacte- rial pathogens from different foods and disinfecting fruit, vegetables, and juices. The application of low- dose (<3 kGy) irradiation to a variety of frozen plant foods to eliminate human pathogens has been stud- ied. The amount of ionizing radiation necessary to re- duce the bacterial population increases with decreas- ing temperature. Significant softening was achieved at−20◦C, but textural changes were not shown when lower ionization doses were employed at higher tem- peratures (−5◦C) (Sommers et al., 2004).
High Pressure. The quality of frozen/thawed prod- uct is closely related to freezing and thawing pro- cesses (Cano, 1996). The rate of freezing and the formation of small ice crystals in freezing are critical to minimize tissue damage and drip loss in thawing. Several reports have studied the use of high pres- sure at subzero temperature (Bing and Da-Wen, 2002; LeBail et al., 2002). The physical state of food can be changed by the external manipulation of pres- sure and temperature according to the water phase diagram. The main advantage of high-pressure freez- ing is that when pressure is released, a high supercool- ing can be obtained, and as a result the ice-nucleation rate is greatly increased and the initial formation of ice is instantaneous and homogeneous throughout the whole volume. The use of high pressure facili- tates supercooling, promotes uniform and rapid ice nucleation and growth, and produces small size crys- tals, resulting in a significant improvement of product quality (LeBail et al., 2002; Bing and Da-Wen, 2002). From a structural point of view, damage to cells during processing is diminished due to the small size of ice crystals, resulting in a significant improve- ment of product quality. These advantages have been
tested with different fruit tissues. Fruit tissues were frozen under pressure. Peach and mango were also cooled under pressure (200 MPa) to−20◦C without ice formation, and then the pressure was released to 0.1 MPa. By scanning electron microscope , it was observed that the cells of fruits frozen under pres- sure were less damaged compared to those frozen us- ing traditional freezing process, including cryogenic freezing (Otero et al., 2000).
High-Pressure Thawing. Thawing occurs more
slowly than freezing. During thawing, chemical and physical damage can occur, as well as microorgan- ism contamination that can reduce the quality of the frozen/thawed product. From a textural point of view, an incorrect thawing can produce an excessive soft- ening of the plant tissue. A quick thawing at low tem- perature to avoid rising temperature could help in as- suring the food quality. High-pressure thawing would be a new application of high-pressure freezing. Re- cent studies showed that high-pressure thawing can preserve food quality and reduce the necessary thaw- ing time. High-pressure thawing was more effective in texture improvement than was atmospheric pres- sure thawing (Bing and Da-Wen, 2002).
ACKNOWLEDGMENTS
This work was financed by the Spanish national research projects, AGL-2002-04059-C02-02 and AGL-2003-09138-C04-01, from Ministry of Sci- ence and Technology and the Spanish project 07G/0053/2003 from Consejer´ıa de Educaci´on, Co- munidad Aut´onoma de Madrid.
REFERENCES
Archer, L.D. 2004. Freezing: an underutilized food safety technology? International Journal of Food Microbiology 90:127–138.
Ashie, I.N.A., Simpson, B.K., Smith, J.P. 1996. Mechanisms for controlling enzymatic reactions in foods. Critical Reviews in Food Science and Nutrition 36(1):1–30.
Bartolom´e, A.P., Ruperez, P., F´uster, C. 1996a. Freezing rate and frozen storage effects on color and sensory characteristics of pineapple fruit slices. Journal of Food Science 61:154.
Bartolom´e, A.P., Ruperez, P., F´uster, C. 1996b. Changes in soluble sugars of two pineapple fruit cultivars during frozen storage. Food Chemistry 56:163.
Bartolom´e, A.P., Ruperez, P., F´uster, C. 1996c. Non-volatile organic acids, pH and tritable acidity changes in pineapple fruit slices during frozen storage. Journal of Science of Food and Agriculture 70:475
Beuchat, R.L. 2002. Ecological factors influencing survival and growth of human pathogens on raw fruits and vegetables. Microbes and Infection 4:413–423.
Billaud, C., Brum-M´erim´ee, S., Louarme, L. 2004. Effect of glutathione and maillard reaction products prepared from glucose or fructose with gluthathione on polyphenoloxidase from apple-II. Kinetic study and mechanism of inhibition. Food Chemistry 84:223–233.
Bing, L., Da-Wen, S. 2002. Novel methods for rapid freezing and thawing of foods: a review. Journal of Food Engineering 54(3):175–182.
Boileau, T.W.M., Moore, A.C., Erdman, J.W. 1999. “Carotenoids and vitamin A.” In Antioxidant Status, Diet, Nutrition and Health, edited by Papas, M. pp. 133–158. New York: CRC Press.
Browleader, M.D., Jackson, P.D., Mobasheri, A.T., Pantelides, S.T., Sumar, S.T., Trevan, M.T., Dey, P.M. 1999. Molecular aspects of cell wall
modifications during fruit ripening. Critical Reviews in Food Science and Nutrition 39(2):149–164. Cano, M.P. 1996. “Vegetables”. In Freezing Effects on
Food Quality, edited by Lester E. Jeremiah, pp. 247–297. New York: Marcel Dekker Inc. Cano, M.P., De Ancos, B. 1994. Carotenoids and
carotenoid esters composition in mango fruit as influenced by processing method. Journal of Agricultural and Food Chemistry 42:2737–2742. Cano, M.P., De Ancos, B, Lobo, M.G. 1996a. Effects
of freezing and canning of papaya slices on their carotenoid composition. Zeistchirft fuer Lebensmittel-Untersuchung und Forchung 202:270–284.
Cano, M.P., Lobo, M.G., De Ancos, B., Galeazzi, M.A. 1996b. Polyphenol oxidase from Spanish hermaphrodite and female papaya fruits (Carica
papaya cv Sunrise, Solo group). Journal of
Agricultural Food and Chemistry 44:3075–3079. Cano, M.P., De Ancos, B., Lobo, M.G., Santos, M.
1997. Improvement of frozen banana (Musa
cavendishii, cv Enana) color by blanching:
relationship among browning, phenols and polyphenol oxidase and peroxidase activities. Zeistchirft fuer Lebensmittel Untersuchung und Forschung. 204:60–65.
Cano, M.P., F´uster, C., Mar´ın, M.A. 1993a. Freezing preservation of four Spanish kiwi fruit cultivars (Actinidia chinensis, Planch): chemical aspects.
Zeitschirift fuer Lebensmittel-Untersuchung und Forschung 195:142–146.
Cano, M.P., Mar´ın, M.A., De Ancos, B. 1993b. Pigment and color stability of frozen kiwi-fruit slices during prolonged storage. Zeistchirft fuer Lebensmittel Untersuchung und Forschung 197:346–352.
Cano, M.P., Lobo, M.G., De Ancos, B. 1998. Peroxidase and polyphenol oxidase in long-term frozen stored papaya slices. Differences among hermaphrodite and female fruits. Journal of Food Science and Agriculture 76:135–141.
Cano, M.P., Mar´ın, M.A. 1992. Pigment composition and color of frozen and canned kiwi fruit slices. Journal of the Agricultural and Food Chemistry 40:2121–2146.
Cano, M.P., Mar´ın, M.A. 1995. Effects of freezing preservation on dietary fibre content of mango (Mangifera indica L.) fruit. European Journal of Clinical Nutrition 49(suppl 3):S257-S260. Cano, M.P., Mar´ın, M.A., F´uster, C. 1990a. Freezing
of banana slices. Influence of maturity level and thermal treatment prior to freezing. Journal of Food Science 55(4):1070–1072.
Cano, M.P., Mar´ın, M.A., F´uster, C. 1990b. Effects of some thermal treatments on polyphenoloxidase and peroxidase activities of banana (Musa cavendishii, var enana). Journal of Science of Food and Agriculture 51:223–231.
Castro, I., Goncalves, O., Teixera, J.A., Vicente, A.A. 2002. Comparative study of Selva and Camarosa strawberries for the commerical market. Journal of Food Science 67(6):2132–2137.
Chaovanalikt A., Wrolstad, R.E. 2004. Anthocyanins and polyphenolic composition of fresh and processed cherries. Journal of Food Science 69:FCT73-FCT83.
Chen, C.S. 1993. “Physicochemical principles for the concentration and freezing of fruit juices.” In Fruit Juice Processing Technology, edited by Steven Nagy, Chin Shu Chen, Philip E. Shaw. Auburndale, FL: Agscience, Inc.
Code Federal Regulation (CFR). 2004. Threshold of Regulation for substance Used in Food contact Articles. Code Federal Regulation, 21 CFR 170.39 (http://gpoaccess.gov/cfr.index.html).
Codex Alimentarius. 1976. Recommended
International Code of Practice For The Processing and Handling of Quick Frozen Foods (CAC/RCP 8–1976) (http://www.codexalimentarius.net/search/ searchindex.do).
Codex Alimentarius. 1999. Recommended Internatio- nal Code of Practice General Principles of Food Hygiene (CAC/RCP 1–1969, Rev.–1997.
4 Fruit Freezing Principles 77 Amd–1999) (http://www.codexalimentarius.net/
search/searchindex.do).
De Ancos, B., Gonz´alez, E.M., Cano, M.P. 1999. Differentiation of raspberry varieties according to anthocyanin composition. Zeistchirft fuer Lebensmittel Untersuchung und Forschung 208:33–38.
De Ancos, B., Gonz´alez, E.M., Cano, M.P. 2000a. Ellagic acid, vitamin C and total phenolic contents and radical scavenging capacity affected by freezing and frozen storage in raspberry fruit. Journal of Agricultural Food and Chemistry 48:4565–4570.
De Ancos, B., Iba˜nez, E., Reglero, G., Cano, M.P. 2000b. Frozen storage effects on anthocyanins and volatile compounds of raspberry fruit. Journal of Agricultural Food and Chemistry 48:873–879. Department of Health and Human Services (DHHS),
Center for Disease Control and Prevention. 1997. Hepatitis A associated with consumption of frozen strawberries. Michigan, March 1997. Morbidity Mortality Weekly Report 46, 288–289.
Escribano-Bail´on, T., Dangles, O., Brouillard, R. 1996. Coupling reactions between flavylium ions and catechin. Phytochemistry 41:1583–1592. European Commission (EC) Directive 90/128/EEC,
Plastic Materials and Articles Intended to Come into Contact With Foodstuffs. Official Journal of The European Communities L75, 21.03.1990. European Commission (EC) Directive 2002/72/EC,
Amending for the Directive 82/711/EEC Laying Down the Basic Rules Necessary for Testing Migration of the Constituents of Plastic Materials and Articles Intended to Come With Foodstuffs. Official Journal of The European Communities L220, 15.08.2002.
European Parliament and Council (EC) Regulation 178/2002. 2002. General principles and require- ments of food law, establishing the European Food Safety Authority and laying down procedures in matter of food. Official Journal of The European Communities L31, 01.02.2002. (http://europa.eu .int/comm/food/index and (http://www.efsa.eu.int). Food and Drug Administration (FDA). 2004. Good
manufacturing practices (GMPs) for the 21st Century Food are Published in Title 21 of the Code of Federal Regulations, Part 110 (21 CFR 110 Processing). http://www.cfsan.fda.gov/∼dms/gmp .toc.html
Fellows, P.J. 2000. Food Processing Technology. Boston: CRC Press.
Fennema, O.R. 1976. The U.S. frozen food industry 1776–1976. Journal of Food Technology 30(6):56–61, 68.
Fito, P., Chiralt, A. 1995. “An update on vacuum osmotic dehydration” In Food Preservation by Moisture Control: Fundamentals and Applications, edited by Barbosa-C´anova, G., Welti-Chanes, J., pp. 351–372. Lancaster, PA: Technomic Publishing Co. Friedman, M. 1996. Food browning and its prevention:
an overview. Journal of Agricultural and Food Chemistry 44:631–653.
Gardner, P.T., White, T.A.C., McPhail, D.B., Duthie, G.G. 2000. The relative contributions of vitamin C, carotenoids and phenolics to the antioxidant potential of fruit juices. Food Chemistry 68:471–474.
Garrote, R.L., Bertone, R.A. 1989. Osmotic concentration at low temperature of frozen strawberry halves. Effect of glycerol, glucose and sucrose solution on exudate loss during thawing. Food Science and Technology 22:264–267. Gonz´alez, E.M., De Ancos, B., Cano, M.P. 2000.
Partial characterization of peroxidase and polyphenoloxidase activities in blackberry fruits. Journal of Agricultural and Food Chemistry 48(11):5459–5464.
Gonz´alez, E.M., De Ancos, B., Cano, M.P. 2002. Preservation of raspberry fruits by freezing: physical, physico-chemical and sensory aspects. European Food Research and Technology 215:497–503.
Heaton, J.W., Lencki, R.W., Marangoni, A.G. 1996. Kinetic model for chlorophyll degradation in green tissue. Journal of Agricultural and Food Chemistry 44:399–402.
Hof, V.H.K.H, Boer, C.J., Tijburg, L.V.M., Lucius, B.R.H.M., Zijp, I., West, C.E., Hautvast, J.G.A.J., Westrate, J.A. 2000. Carotenoid bioavailability in humans from tomatoes processed in different ways determinated from the carotenoid response in the triglyceride-rich lipoprotein fraction of plasma after a single consumption and in plasma after four days of consumption. Journal of Nutrition 130:1189– 1196.
Hui Y.H., Cornillon P., Guerrero I., Lim M., Murrel K.D., Nip Wai-Kit. 2004. Hand Book of Frozen Foods. New York: Marcel Dekker Inc.
Institute International of Refrigeration (IIR). 1986. Recommendations for the Processing and Handling of Frozen Foods. 3rdedition. Ed. Institute
International of Refrigeration. Par´ıs.
Kmiecik, W., Jaworska, G., Budnik, A. 1995. Effect of thawing on the quality of small fruit frozen products. Roczniki Panstwowego Zakladu Higieny 46 (2): 135–143.
Larsen, M., Poll, L. 1995. Changes in the composition of aromatic compounds and other quality parameters
of strawberries during freezing and thawing. Zeistchirft fuer Lebensmittel Untersuchung und Forschung 201:275–277.
Lavelli, V., Peri, C., Rizzolo, A. 2000. Antioxidant activity of tomato products as studied by model reactions using xanthine oxidase, myeloperosidase, and copper-induced lipid peroxidation. Journal of Agricultural and Food Chemistry 48:1442–1448. LeBail, A., Chevalier, D., Mussa, D.M., Ghoul, M.
2002. High pressure freezing and thawing of foods: a review. International Journal of Refrigeration 25:504–513.
Lisiewska, Z., Kmiecik, W. 2000. Effect of storage period and temperature on the chemical composition and organolectic quality of frozen tomato cubes. Food Chemistry 70:167–173.
Lobo, G., Cano M. Pilar. 1998. Preservation of hermaphrodite and female papaya fruits (Carica
papaya L. cv sunrise, solo group) by freezing:
physical, physico-chemical and sensorial aspects. Zeistchirft fuer Lebensmittel Untersuchung und-Forschung A 206:343–349.
Lund, B.M. 2000. “Freezing.” In The Microbiological Safety and Quality of Food, edited by Lund, B.M., Baird-Parker, T.C., Goudl, G.W., vol I, pp. 122–145. Gaithersburg, MD: Aspen Publishers.
Mar´ın, M.A., Cano, M.P., F´uster, C. 1992. Freezing preservation of four Spanish mango cultivars (Mangifera indica, L.): chemical and biochemical aspects. Zeistchirft fuer Lebensmittel Untersuchung und Forschung 194:566–569.
Martiner, M.V., Whitaker, J.R. 1995. The biochemistry and control of enzymatic browning. Trends in Food Science and Technology 6:195–200.
Mastrocola, D., Manzocco, L., Poiana, M. 1998. Prevention of enzymatic browning during freezing, storage and thawing of cherimoya (Annona
Cherimola, Mill) derivatives. Italian Journal of Food
Science 10(3):207–215.
Miller, N.J., Rice-Evans, C.A. 1997. The relative contributions of ascorbic acid and phenolic antioxidants to the total antioxidant activity of orange and apple fruit juices and blackcurrant drink. Food Chemistry 60:331–337.
Mullen, W., Stewart, A.J., Lean, M.E.J., Gardner, P., Duthie, G.G., Grozier, A. 2002. Effect of freezing and storage on the phenolics, ellagitannins, flavonoids, and antioxidant capacity of red raspberry. Journal of Agricultural and Food Chemistry 50(8):5197–5201.
National Advisory Committee on Microbiological Criteria For Foods (NACMCF). 1997. Hazard Analysis and Critical Control Point Principles and Application Guidelines http://vm.cfsan.fda.gov/ ∼comm/nacmcfp.html).
Otero, L., Martino, M., Zaritzky, N., Solas, M., Sanz, P.D. 2000. Preservation of microstructure in peach and mango during high-pressure-shift freezing. Journal of Food Science 65(3):466–470.
Philippon, J., Rouet-Mayer, M.A. 1984. Blanching and quality of frozen vegetables and fruit. Review I. Introduction and enzymatic aspects. International Journal of Refrigeration 7(6):384–388.
Plocharski, W. 1989. Strawberries quality of fruits, their storage life and suitability for processing. Part VI. Quality of fruit frozen immediately after picking or frozen after cold storage under controlled atmosphere conditions. Fruit Science and Rep.(Skierniewice) 16(3):127. The reference journal is:
Rahman M. Sahafiur. 1999. “Food preservation by freezing.” In Handbook of Food Preservation, edited by Rahman M. Sahafiur, p. 259. New York: Marcel Dekker Inc.
Rao, A.V., Agarwal, S. 1999. Role of lycopene as antioxidant carotenoid in the prevention of chronic disease: a review. Nutrition Reviews 19:305–323. Reid, D. 1996. “Fruit freezing.” In Processing Fruits:
Science and Technology. Vol.1. Biology, Principles and Application, edited by Somogoyi, L.P., Ramaswamy, H.S., Hui, Y.H., p. 169. Lancaster, PA: Technomic Publishing.
Reid, T.M.S., Robinson, H.G. 1987. Frozen raspberries and hepatitits A. Epidemiology and Infection 98:109–112.
Rice-Evans, C., Miller, N.J., Paganga, G. 1996. Structure-antioxidant activity relationships of flavonoids and phenolic acids. Free Radical Biology Medical 20:933–956.
Robbers, M., Sing, R.P., Cunha, L.M. 1997. Osmotic-convective dehydrofreezing process for drying kiwifruit. Journal of Food Science 62(5):1039–1042.
Robinson, D.S., Eskin, N.A.M. 1991. Oxidative Enzymes in Foods. London: Elsevier.
Rodriguez-Amaya, D.B. 1997. Carotenoids and Food Preparation: The Retention of Provitamin A Carotenoids in Prepared, Processed and Stored Foods. Washington, DC: Agency for International Development, OMNI/USAID.
Sahari, M.A., Boostani, M., Hamidi, E.Z. 2004. Effect of low temperature on the ascorbic acid content and quality characteristics of frozen strawberry. Food Chemistry 86:357–363.
Salgado, S.M., Guerra, N.B., Melo-Filho, A.B. 1999. Frozen fruit pulps: effects of the processing on dietary fiber contents. Revista de Nitricao 12(3):303–308.
Simpson, K.L. 1986. “Chemical changes in natural food pigments.” In Chemical Changes in Food
4 Fruit Freezing Principles 79 During Processing, edited by Finley, J.W., pp.
409–441. Westport, CT: AVI.
Skrede, G. 1996. “Fruits”. In Freezing Effects on Food Quality, edited by Lester, E.J., pp. 183–245. New York: Marcel Dekker Inc.
Sommers, C., Fan, X., Niemira, B., Rajkowski, K. 2004. Irradiation of ready-to-eat foods at USDA’S Easter regional research center-2003 update. Radiation Physics and Chemistry 71:509–512. Spiazzi, E.A., Raggio, Z.I., Bignono, K.A.,
Mascheroni, R.H. 1998. Experiments on dehydrofreezing of fruits and vegetables mass transfer and quality factors. Advances in the Refrigeration Systems, Food Technologies and Cold Chain, IIF/IIR 6:401–408.
Steinmetz, K.A., Potter, J.D. 1996. Vegetables, fruit and cancer prevention: a review. Journal American Diet Association 53:536–543.
Suutarinen, J., Heiska, K., Moss. P., Autio, K. 2000. The effects of calcium chloride and sucrose pre-freezing treatments on the structure of strawberry tissues. Lensmittel Wissensachaft und Technologie 33:89–102.
Talens, P., Escriche, I., Mart´ınez-Navarret, N., Chiralt, A. 2002. Study of the influence of osmotic dehydration and freezing on the volatile profile of strawberries. Journal of Food Science
67(5):1648–1653.
Talens, P., Escriche, I., Mart´ınez-Navarret, N., Chiralt, A. 2003. Influence of osmotic dehydration and freezing on the volatile profile of kiwi fruit. Food Research International 36:635–642.
Tibble, D.L., Benson, J., Curtin, K., Ma, K.-N., Schaeffer, D., Potter, J.D. 1998. Further evidence of the cardiovascular benefits of diets enriched in carotenoids. American Journal of Clinical Nutrition 68:521–522.
Tregunno, N.B., Goff, H.D. 1996.
Osmodehydrofreezing of apples: structural and textural effects. Food Research International. 29:471–479.
Urbanyi, G., Horti, K. 1989. Color and carotenoid content of quick-frozen tomato cubes during frozen storage. Acta Alimentaria 18:247–267.
Willcox, J.K., Catignani, G.L., Lazarus, S. 2003. Tomatoes and caridovascular health. Critical Reviews in Food Science and Technology 43: 1–18.
Yueming-Jiang, Yuebiao-Li, Jianrong-Li. 2004. Browning control, shelf live extension and quality maintenance of frozen litchi fruit by hydrochloric acid. Journal of Food Engineering 63(2):147–151.
Zhao, Y., Xie, J. 2004. Practical applications of vacuum impregnation in fruit and vegetable processing. Food Science and Technology 15:434–451.