食品专业英语 LESSON 10 Principles Of Food Preservation By Dr

Drying is one of mans oldest s of food preservation. It is a process copied from nature; we have improved certain features of the operation. Drying is the most widely used of food preservation. All the cereal grains are preserved by drying, and the natural process is so efficient it hardly requires added effort by man. However, there have been periods in history when climatic factors were such that grains failed to dry properly in the fields. In these instances, man attempted to assist the natural action by supplying heat to the grains which otherwise would decompose. Grains, legumes, nuts and certain fruits mature on the plants and dry in the warm wind. More fruits are preserved by drying than by any other of food preservation. The natural sun drying of foods yields highly concentrated materials of enduring quaity. yet a highly complex civilization cannot be so dependent upon the elements-they are unpredictable. Sun drying remains the greatest food preservation action. Dehydration-Artificial Drying The use of heat from a fire to dry foods was discovered independently by many men in the New and Old Worlds. Ancient man dried foods in his shelters; pre-Columbus American Indians used the heat from fire to dry foods. However, it was not until about 1795 that a hot air dehydration room was invented. The team of Masson and Challet in France developed a vegetable dehydrator which consisted of hot air40℃ flow over thin slices of vegetables. It is worth noting that both canning and dehydration came into being at approximately the same time, nearly a century and a half ago. Evaporation and desiccation are terms which perhaps note the same action. The term dehydration has taken the meaning in the food industry as that Process of artificial drying. Dehydration vs. Sun Drying Dehydration implies control over climatic conditions within a chamber, or microenvironment control. Sun drying is at the mercy of the elements. Dried foods from a dehydration unit can have better quality than sun-dried counterparts. Less land is required for the drying activity. Sun drying for fruit requires approximately one unit of drying surface per 20 units of crop land. Sanitary conditions are controllable within a dehydration pant, whereas in open fields contamination from dust, insects. birds and rodents are major problems. Dehydration obviously is a more expensive process than sun drying, yet the dried foods may have more monetary value from dehydration due to improved quality. The yield of dried fruit from a dehydrator is higher inasmuch as sugar is lost due to continued respiration of tissues during sun drying, and also due to fermentation. The color of sun-dried fruit may be superior to dehydrated fruit under optimum conditions of operation of both. Color development in certain immature fruits continues slowly during sun drying. This does not occur during. dehydration . In