Stab1hty lof F reeze-Dned F (mds
"‘
SAMUEL A. GOLDBLITH AND MARCUS KAREL
MASSACHUSE‘TTS INSTITUTE OF TECHNOLOGY
CAMBRIDGE (MASSACHUSETŒ) U.S.A.
.
.
-
_
€
INTRODUCTION
The quality of freeze—dehydrated foods is limited by deteriorative reactions which may be
of microbiological origin or may be due to physicO-chemical reaction. In the present paper
we discuss both major types of deterioration, as separate aspects of stability of freeze—
dehydrated foods. The rst section discusses physico—chemical aspects, and the second
the microbiological aspects. In actual practice, however, the two aspects are not always
_
distinct entities and often interact. An excellent example of this is given by Peterson (1961)
who points out, and illustrates With data, that many foods can and do become organoleptically unacceptable due to chemical changes and yet are microbiologically very acceptable. Moreover, many of the chemical changes are often a result of microbial growth and
reaction.
A. PHYSICO-CHEMICAL ASPECTS
The potentially high organoleptic and nutñtional quality of freeze-dehydrated foods is
limited by several physical and chemical deteriorative processes. In reviewing these processes
‘
(Karel, 1963 : Goldblith et al., 1963), the authors postulated that the deterioration is due
primarily to the following mechanisms :
_
1. Loss of volatiles during the process of dehydratmn.
_
_
2. Loss of water—holding capacity during dehÿdratlon and storage. '
3. Non—enzymatic browning.
4. Lipid oxidation.
_
_
,
5. Enzymatic reactions.
.
'
,
*
Contribution number 861 from the Department of Nutrition and Food Science, Massachusetts Institute of
Technology.
.
“
.
.
.
.
.
t d '
;… by USPHS Research Grants EF— 06376
and EF—00314 from the Dmsron of
Ilïlbopd Protection for which the authors ‘are grateful.
"‘
SAMUEL A. GOLDBLITH AND MARCUS KAREL
MASSACHUSE‘TTS INSTITUTE OF TECHNOLOGY
CAMBRIDGE (MASSACHUSETŒ) U.S.A.
.
.
-
_
€
INTRODUCTION
The quality of freeze—dehydrated foods is limited by deteriorative reactions which may be
of microbiological origin or may be due to physicO-chemical reaction. In the present paper
we discuss both major types of deterioration, as separate aspects of stability of freeze—
dehydrated foods. The rst section discusses physico—chemical aspects, and the second
the microbiological aspects. In actual practice, however, the two aspects are not always
_
distinct entities and often interact. An excellent example of this is given by Peterson (1961)
who points out, and illustrates With data, that many foods can and do become organoleptically unacceptable due to chemical changes and yet are microbiologically very acceptable. Moreover, many of the chemical changes are often a result of microbial growth and
reaction.
A. PHYSICO-CHEMICAL ASPECTS
The potentially high organoleptic and nutñtional quality of freeze-dehydrated foods is
limited by several physical and chemical deteriorative processes. In reviewing these processes
‘
(Karel, 1963 : Goldblith et al., 1963), the authors postulated that the deterioration is due
primarily to the following mechanisms :
_
1. Loss of volatiles during the process of dehydratmn.
_
_
2. Loss of water—holding capacity during dehÿdratlon and storage. '
3. Non—enzymatic browning.
4. Lipid oxidation.
_
_
,
5. Enzymatic reactions.
.
'
,
*
Contribution number 861 from the Department of Nutrition and Food Science, Massachusetts Institute of
Technology.
.
“
.
.
.
.
.
t d '
;… by USPHS Research Grants EF— 06376
and EF—00314 from the Dmsron of
Ilïlbopd Protection for which the authors ‘are grateful.