National Academies Press: OpenBook

Dehydration and Compression of Foods (1982)

Chapter: SUMMARY

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Suggested Citation:"SUMMARY." National Research Council. 1982. Dehydration and Compression of Foods. Washington, DC: The National Academies Press. doi: 10.17226/18526.
Page 1
Suggested Citation:"SUMMARY." National Research Council. 1982. Dehydration and Compression of Foods. Washington, DC: The National Academies Press. doi: 10.17226/18526.
Page 2
Suggested Citation:"SUMMARY." National Research Council. 1982. Dehydration and Compression of Foods. Washington, DC: The National Academies Press. doi: 10.17226/18526.
Page 3

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SUMMARY The armed forces has long used dehydrated foods during times of conflict, procuring large amounts and thus enabling such foods to be reasonably cost effective. During peacetime procurement levels are low because these foods are used primarily in training exercises. In addition, small procurements of this type of food for research and development have forced the cost of dehydrated foods, particularly freeze-dried components, well beyond the costs of competing foods preserved by heat or freezing. Dried compressed foods may be the only source of nutrition for troops during extended periods in the field. While not a subject of this workshop, the nutritional value and safety of dried compressed foods will continue to be evaluated along with other quality factors such as flavor, structure, and color. Ultimately, operational performance requirements are the basis for acceptance of any new technology and these include nutritional value and safety as well as acceptance. The compression of dried food to reduce volume, as well as trans- portation and packaging costs has increased the discrepancy between products for civilian use and those suitable only for military pro- curement. The compression step is usually carried out directly after freeze-drying; these compressed products must be produced for military procurements rather than added on to production runs for civilian use. Air-dried foods have not proved suitable for compression in comparison to freeze-dried products. The limited needs of the military for compressed dehydrated food during peacetime, coupled with the need to maintain a broad supplier base, has led to small procurements. Since many items are produced seasonally, raw material should be contracted when the seed goes into the ground in order to obtain the variety most suitable for de- hydration and compression. Small procurements and the need to maintain a broad supplier base preclude effective crop scheduling. TOWARD COST-EFFECTIVENESS Detailed systems cost analyses should be carried out on a regular basis. The procurement, manufacturing, distribution, and use of compressed freeze-dried foods have been, and are being, subjected to

systems analysis to ensure a maximum cost-benefit under projected conditions of use. Findings of these reports should be given maximum publicity and incorporated into procurement, funding, and research programs as quickly as possible. These systems analysis studies can help in identifying spin-offs to additional nonmilitary uses for freeze-dried and compressed freeze-dried products to help broaden the marketing base for these products. Industry should develop export markets and identify additional uses in food service. Research in support of systems analysis findings for new product applications should be a joint effort. Industry funds should be applied to air-drying studies on lower cost components such as fruits, vegetables, and specially formulated products. Efforts are needed to produce suitable compressed dried products from air-dried starting materials. Raw materials for dehydration and compression must be selected to optimize the performance and acceptability of the reconstituted product. Since specific varieties of fruits and vegetables may not be available when contracts are awarded, frozen starting materials should be used so that the foods can be procured regularly and distributed among several vendors. Freeze-dehydration allows the use of a wide selection of frozen, preprocessed stored foods. However, the low unit cost and high water content of most fruits and vegetables make freeze- drying an expensive method for water removal. There may be a need, moreover, for a change in policy to allow procurement to start with the planting of the seed of special varieties. Frozen starting materials may be difficult to air dry to a quality product. Research and development programs are needed to allow air de- hydration or other relatively new low-cost technologies for water removal to be substituted for freeze-drying. For example, one of these new techniques is microwave-assisted heat transfer, which appears to be most promising for reducing the cost of freeze-drying and improving the efficiency of compression. Preliminary studies indicate that drying times can be reduced significantly, perhaps to four hours, if microwave energy is applied at the start and in the low-moisture portion of the drying cycle. Microwaves have also been used to heat partially dried food prior to compression to facilitate moisture distribution before compression and after compression to hasten finish-drying. Large-scale applications of microwave energy may require strategic planning since units are costly. Packaging appears to be adequate for the protection of dried compressed foods. Strategic reserves of certain seasonal food materials suitable for dehydration and compression, in dehydrated or dehydrated and compressed form, can be maintained at three levels. Military purchase of frozen foods destined for dehydration and compression can be maintained at a predetermined level. These stocks can be rotated through issue as frozen foods. A second level of inventory can be maintained as freeze-dried components, noncompressed, which can be rotated through civilian products or converted to com- pressed form. A third inventory would be maintained in the compressed dried form. All stored items, full, part moisture or dried, would be stored below -18°C (0°F) until issued to ensure maximum shelf life upon issue.

Continued basic research is needed to help predict the shelf life remaining in dehydrated compressed foods stored at room or elevated temperatures. Since military storage requirements are far more stringent than civilian, this work should be supported by DOD funds. New research findings indicate the potential for early detection of chemical precursors of deterioration. As more knowledge is developed on pathways for flavor, color, and structure changes as a function of temperature, composition, water activity, and packaging environment, the significance of selected precursors, their detection, and the measurement of their concentration will increase. This knowledge will speed developments obviating storage deterioration by reducing the need for lengthy shelf life testing.

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