Title: Controlled humidity freeze drying process

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Claims: What is claimed is:

1. A method for limited freeze drying of foods comprising cooling the food to freeze water contained therein into ice, subliming the ice from the food in an atmosphere at a predetermined relative humidity, stabilizing the relative humidity in said atmosphere during the sublimation of ice from the food by continually contacting the atmosphere with a quantity of a hydrating salt.

2. The method of claim 1 wherein the relative humidity is stabilized by removing water vapor from the atmosphere through contact with a salt that changes from a first lower hydration state to second higher hydration state.

3. A method for limited freeze drying of foods comprising freezing the food and the moisture contained therein, subliming the moisture from said frozen food maintaining the relative humidity in the surrounding atmosphere at a predetermined relative humidity by contacting the atmosphere with a salt in a first lower hydration state and removing at least a portion of the moisture sublimed from the food from atmosphere by said salt undergoing transition to a second higher hydration state, and utilizing heat generated by the hydrating salt for sublimation of the frozen moisture from the food.

4. The method of claim 3 wherein the atmosphere is continually circulated between the frozen food and the hydrating salt.

5. In a method for limited freeze drying of food in which a food product is frozen to change water therein into ice and is subsequently introduced into a reduced pressure atmosphere to sublime the ice from the food product, the improvement comprising maintaining the relative humidity in said atmosphere at a preselected value by continually contacting the atmosphere with a hydrated salt that undergoes a transition from a first lower hydration state to a second higher hydration state during the freeze drying process.

6. the method of claim 5 wherein a further improvement comprises supplying thermal energy generated during the hydration transition of said salt to the frozen food product to furnish energy required to sublime the ice therefrom.

7. The method of claim 6 wherein the water content of said food product is reduced to from about 5 to about 25% by weight at termination of the limited freeze drying.

8. The method of claim 6 wherein the atmosphere is continually circulated between the freeze drying food and the hydrating salt.

9. The method of claim 6 wherein the food and hydrating salt are placed in alternating, adjacent layers and the atmosphere is circulated through the adjacent layers.
Other info:

Inventors: King, Cary J. (Kensington, CA, US)

Application Number: 584597
Filing Date: 1975-06-06
Publication_date: 1976-06-22
Assignee: The Regents of the University of California (Berkeley, CA)
Primary Class(es): 34/287
Other Classes:
US Patent Ref:

3438792	May, 1969	Kruger	34/5.
3466756	Sep, 1969	Tooby	34/5.
3716382	Feb, 1973	Chandrasekaran et al.	34/5.

Other Refs:
Primary Examiner: Camby, John J.
Assistant Examiner:
Attorney: Phillips, Moore, Weissenberger Lempio & Strabala