This chapter discusses that freezing has become an important method of food preservation during the last 30 years. If the most desirable food quality is that of the freshly harvested fruit or vegetable, then the ultimate in frozen food would be perfect preservation of the living state. Water is the major component of plants and most plant parts (except seeds and woody stems) and the major component undergoing a phase change during freezing. Water, the major component of plants, undergoes a phase change during freezing. When solutions freeze, loss of water to the solid phase leaves the remaining solution more concentrated. Plants differ widely in their responses to low temperatures. Seeds are a means of reproducing and increasing the number of plants. In plants, beyond the young seedling stage, a number of responses to chilling have been observed. Most plants that survive freezing temperatures during winter experience a frost-free season during which their major growth takes place. Dehardening (loss of the ability to survive low temperatures) is the response of hardened plants to temperature increases. Fruits and vegetables include a wide range of plant parts harvested and eaten at various stages of maturity. Fresh fruits and vegetables are living organs that continue their metabolic processes after they have been harvested. The chapter discusses that fruits and vegetables are obtained from a variety of plants whose edible parts are harvested at times ranging from the extreme immaturity of germinating seedling to the senescence of mature fruit.
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