ABSTRACT
Freezing of foods has been a common way of long-term food preservation for thousands of years because of the high product quality and long shelf life. During freezing, water is converted into ice and the formation of ice removes water from food systems. The reduced water activity helps to preserve foods for longer periods of time, and freezing temperatures reduce the rate of chemical reactions and the activity of microorganisms and enzymes, thereby extending the storage life of frozen foods. The nutritional quality of the food is also preserved better by freezing. It is known that the least vitamin loss occurs in frozen food preservation. The loss of quality of frozen foods mainly depends on packaging, storage temperature, length of storage time, and thawing procedure. Frozen foods are usually stored at −18°C, so thawing or tempering is needed for further processing or cooking. However, chemical, physical, and microbiological changes that occur during long thawing or tempering periods result in unacceptable changes in product quality. Therefore, selection of methods that shorten the thawing or tempering process and, in consequence, maximize the safety and quality retention of foods, are important for frozen food industry. The novel thawing methods are microwave thawing, high-pressure thawing, acoustic thawing, and Ohmic thawing. These innovative thawing methods can shorten thawing time, thus reducing drip loss and improving product quality (Li and Sun, 2002). Ohmic thawing has advantages over conventional thawing such as short thawing time, easy process control, high-energy conversion, and the absence of water usage and generation of waste water (Roberts et al., 1998).
