Document Type

Thesis - Open Access

Award Date

1964

Degree Name

Master of Science (MS)

Department

Foods and Nutrition

Abstract

Natural drying of edible seeds and fruits with the aid of the sun and wind is one of the oldest methods of preserving food and was practiced even by the people of the Stone Age. Drying means the removal of water, whereas dehydration means the application of special techniques for the removal of water with minimum damage to appearance, flavor, texture, and nutritive value. Among various methods of dehydration, freeze-drying most satisfactorily fulfills the requirements of minimum damage. Freeze-drying, also known as lypohilization, was introduced as a method of treating glands for pharmaceutical purposes. Being a slow and expensive process, it was applied only to labile materials of high value such as pharmaceuticals, blood plasma, and penicillin. By quick freezing, the constituents of the tissues, solids, and fluids are immobilized, and thereafter the water can be removed by sublimation so that practically no concentration of salts occur, and there is little denaturation of protein, or gelling of starches or twisting of fibers. Thus, the final product is as little changed as it can be and when water is added, it instantly perfuses honeycomb of sponge-like tissue, swelling it out and reconstituting the food to its original condition within a few minutes. Today practically every large food manufacturer in the United States as well as in Europe is promoting extensive research on perfecting freeze-drying techniques that will preserve nutritive value and palatability, and reduce production costs. In times to come, freeze-drying may provide an answer to two problems. In western world, there is a continuous demand for convenient foods of quality closer to that of fresh foods. In large part of the rest of the world, there is a demand for foods of almost any kind. If freeze-dried foods can be more easily transported, can be stored without refrigeration, and maintain their quality and nutritive value, then the process may also have a part to play in helping to solve world food problems. Because of the current interest in this method of preservation, this study was undertaken to obtain information on the effect of freeze-drying on palatability, texture, and Vitamin C retention. Since palatability of a product is a critical factor affecting its acceptance, some taste tests were conducted on the freeze-dried products. Thus, the object of this research was to determine the effect of freeze-drying at different temperatures in the nutritive quality and palatability of freeze-dried products. A second objective was to study the effect of storage at different temperatures and conditions on the palatability of freeze-dried products.

Library of Congress Subject Headings

Food -- Preservation
Dried foods
Frozen foods

Description

Includes bibliographical references

Format

application/pdf

Number of Pages

50

Publisher

South Dakota State University

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