Excerpt from In-Package Desiccation of Dehydrated Foods

The first record of desiccant packaging appears to be that ofven English patent granted to w. T. Yule ih lbhs' (141) for keeping animal and vegetable matters dry, when preserving them in c'e'sed vessels 3 by placing chloride of calcium or other chemical absorbent in such vessels, but not in contact with th�' matters to be preserved Patents were granted to 0hlhaver in 1911 and 1912 for the packaging of dry yeast with a desiccant. Other patents-(t2373 2li 31) issued before World War II were for contain ers, and for drying agents, for the desiccant packaging of metal goods, of pharmaceuticals, and of foodstuffs such as cereal products, crisp bakery goods, candy, pepper, and coffee. During World War II, desiccant packaging was used on a large scale (9 the Armed Forces in the Method II packaging of instruments, equipment and machinery for maintenance of the humidity be low that at which metals rust. In the past five years a number of publica tions (8, lg, 20, 25) have appeared on the desiccant packaging of a range of food in 1950 a patent was issued to Cotton and Schroeder (assigned to National Research Corp.) for application of the process to citrus juice powders.

The desiccants most commonly specified in these publications and patents are the physical-adsorption type silica gel, alumina, and montmorillonite). Such desiccants have high moisture adsorptive capacity at the moderate rela tive humidities that are effective in preventing moisture absorption of many foods. Desiccants of this type, and also calcium sulfate, are listed in the citrus wder patent of Cotton and Schroeder; however, such desiccants have low capa ity at the low humidities necessary for the efficient continued drying of foods that have been dehydrated. Calcium chloride is specified as the desiccant in a number of the' early patents, but even this drying agent has but moderate capacity in the relative huntidity range bf l to 5 percent, ne'eded'for adequate desiccation of some dehydrated foods. Minimizing the sacrifice of container volume to the desiccant is of course important. For this reason, calcium oxide was selected fer most of the ih-package desicca tion studies at this laboratory. A relatively small amount of this drying agent can effectively desiccate dehydrated foods, since it has full capacity at very low relative humidities. The problem of expansion of the calcium oxide on hydration is important, and a considerable amount of work has been necessary to develop desiccant containers which will withstand this expansion.

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