chapter  7
88 Pages

Thermodynamic Properties of Foods in Dehydration

WithS. S. H. Rizvi

As the most abundant and the only naturally occurring inorganic liquid material on Earth, water is known to exhibit unique and anomalous behavior. Held together by a random and fluctuating three-dimensional network of hydrogen bonds, no single theory to date has been able to explain the totality of its unusual molecular nature. Yet, throughout history, people have learned that either removing water or making it unavailable via binding to appropriate matrices can extend the period of usefulness of perishable products. It otherwise provides the critical environmental factor necessary for the ubiquitous biological, biochemical, and biophysical processes that degrade foods and ultimately render them unfit for human consumption. Any reduction in water content that retards or inhibits such processes will indeed preserve the food. Thus, dehydration as a means of preserving the safety and quality of foods has been at the forefront of technological advancements in the food industry. It has greatly extended the consumer-acceptable shelf life of appropriate commodities from a few days and weeks to months and years. The lower storage and transportation costs associated with the reduction of weight and volume due to water removal have provided

additional economic incentives for widespread use of dehydration processes. The expanding variety of commercial dehydrated foods available today has stimulated unprecedented competition to maximize their quality attributes, to improve the mechanization, automation, packaging, and distribution techniques, and to conserve energy.