ANSWER
Maintaining proper storage temperatures and storage conditions are crucial to obtain superior quality of frozen fruits. Temperature fluctuations during storage or change in temperature within the product will cause moisture migration which can greatly affect the texture and overall quality of the frozen fruits (Sehrawat et al., 2018).
The use of freezing process to increase the fruit’s viability has gained widespread attention since the reduction of available water due to ice crystal formation and subzero temperatures provide an environment which favors reduced chemical reactions leading to increased storage. Moreover, the formation of ice results in textural changes and disruption of cell compartments. The firmness values of all of the frozen-thawed fruits decreased with respect to that of the fresh fruits (Sirijariyawat & Charoenrein, 2012).
According to USDA (2013), it is safe to refreeze if the fruit still contains ice crystals or is 40 °F or below. However, partial thawing and refreezing may reduce the quality of some food, but the food will remain safe to eat.
The freezing rate has a major impact on ice crystal size since it affects the relative rates of nucleation and crystal growth (Degner et al., 2013). Small ice crystals can be formed by rapidly cooling a food material well below its freezing point. The formation of small ice crystals during freezing is typically thought to be desirable for maintaining the quality and stability of fruits since it minimizes cell rupture (Degner et al., 2014).
Both freezing rate and thawing rate will affect the survival of microorganisms. It was concluded that the combination of rapid freezing and slow thawing may kill more bacteria than slow freezing and rapid thawing. It was found that rapid thawing may increase the survival of microorganisms although freezing rate is more important than thawing rate (Kennedy, 2005).
Since thawing and freezing of unopened packages will not generate a health hazard, it is recommended that such products be used immediately in bakery goods, ice cream, wine, or alcoholic products (Woodroof, 2012).
Multiple freeze-thaw cycles will significantly affect the texture of frozen fruits (Charoenrein and Owcharoen, 2016). When the frozen fruits thaw or partially thaw, and are then refrozen, some of their aesthetic qualities including texture, colour, flavor and aroma will be greatly deteriorate, depending upon the rate at which thawing and refreezing occur. Worry not, Vitamins will be least affected (Woodroof, 2012).
References
Sehrawat, R., Khan, K. A., Goyal, M. R. & Paul, P. K. (2018). Technological Interventions in the Processing of Fruits and Vegetables. Boca Raton: CRC Press.
Charoenrein, S. & Owcharoen, K. (2016). Effect of freezing rates and freeze-thaw cycles on the texture, microstructure and pectic substances of mango. International Food Research Journal, 23(2), 613-620.
Degner, B. M., Chung, C., Schlegel, V., Hutkinds, R. & McClements, D. J. (2014). Factors Influencing the Freeze‐Thaw Stability of Emulsion‐Based Foods. Comprehensive Reviews in Food Science and Food Safety, 13(2), 98-113. https://doi.org/10.1111/1541-4337.12050.
Degner, B. M., Olson, K. M., Rose, D., Schlegel, V., Hutkins, R., McClements, D.J. (2013). Influence of freezing rate variation on the microstructure and physicochemical properties of food emulsions. Journal of Food Engineering, 119(2), 244-253. https://doi.org/10.1016/j.jfoodeng.2013.05.034
USDA. (2013). Food Safety Education: Keeping Food Safe During an Emergency.
Sirijariyawat, A. & Charoenrein, S. (2012). Freezing characteristics and texture variation after freezing and thawing of four fruit types. Songklanakarin Journal of Science and Technology, 34(5), 517-523.
Woodroof, J. G. (2012). Commercial Fruit Processing (pp. 590-594). Heidelberg, Germany: Springer Science & Business Media.
Kennedy, C. J. (2005). Managing Frozen Foods (pp. 7-11). Cambridge: CRC Press.
