Deteriorative reactions are low and food quality high if intermediate moisture content of a food is held at a water activity of 0.6 to 0.75. Information is of interest to food processing and packaging industry

Labruza, T. P.

English

NASA Technical Reports Server

August 1971	 Brief 71-10332 
NASA TECH BRIEF 
Manned Spacecraft Center 
NASA Tech Briefs announce new technology derived from the U.S. space program. They are issued to encourage 
commercial application. Tech Briefs are available on a subscription basis from the National Technical Information 
Service, Springfield; Virginia 22151. Requests for individual copies or questions relating to the Tech Brief program may 
be directed to the Technology Utilization Office, NASA, Code KT, Washington, D.C. 20546. 
The Deterioration of Intermediate Moisture Foods 
A recent study of the mechanism of intermediate 
moisture foods has disclosed some significant facts which 
will be of interest to the food processing and packaging 
industry. 
The value of intermediate moisture foods lies in 
their stability over protracted periods of time without 
their being canned, refrigerated, or frozen. Fabrication 
is accomplished by reducing and maintaining the normal 
water content of the foods to levels below which micro-
organisms can grow. But the process which requires 
humectants to be added can produce a chemical en-
vironment which provides increased deteriorative reac-
tions - lipid oxidation and non-enzymatic browning being 
among them. 
For this study, which concentrated on finding 
means of preventing these reactions, model systems were 
developed having the same water activity/water content 
relationship of intermediate moisture foods. Models 
were based on a cellulose-lipid and protein-lipid system 
with glycerol added as the humectant. Experiments with 
both systems indicated that significant lipid oxidation 
is promoted in the intermediate moisture range. As the 
rates of oxidation increased when the amount of water 
in the system reached a level where capillary condensa-
tion occurred, the oxidation effect appears to be related 
to the increased mobility of either the reactants or the 
catalysts. With glycerol the increase in oxidation rate oc-
curs at a lower relative humidity. One important factor 
in the design of stable food items derives from the evi-
dence that the oxidation rates were maximized at 61% 
RH; the latter effect was probably due to dilution. 
No significant non-enzymatic browning occurred in 
the protein-lipid systems. Prevention of oxidation by the 
use of metal chelating agents was enhanced in the cellu-
lose system. On the other hand, with protein present,
the lipid soluble chain terminating antioxidants (such as

butylated hydroxy anisole, BHA) worked equally as well.

Preliminary studies of foods adjusted to the intermediate 
moisture range confirm the results of oxidation in the 
model systems. It appears that the reaction which will

set the limit on the stability of an intermediate moisture 
food will be rancidity. However, water soluble chelating

agents will delay the development of rancidity, improve

the stability of the foods and give them a longer shelf

life. Phenolic antioxidants also have good activity espe-

cially in high protein systems. Although non-enzymatic 
browning may also cause some deterioration if the foods 
are protected from oxidative rancidity, it is predicted

that this may not occur until after the normal shelf life.

The conclusion of this study is that good quality

will be ensured if the intermediate moisture content of
a food is held at a water activity of 0.6 to 0.75. 
Note:
Requests for further information may be directed 
to:
Technology Utilization Officer 
Manned Spacecraft Center, Code JM7 
Houston, Texas 77058 
Reference: TSP71-10332 
Patent status: 
No patent action is contemplated by NASA. 
Source: Dr. Theodore P. Labruza

Massachusetts Institute of Technology

under contract to

Manned Spacecraft Center

(MSC-13827) 
Category 05 
This document was prepared under the sponsorship of the National 
Aeronautics and Space Administration. Neither the United States 
Government nor any person acting on behalf of the United States
Government assumes any liability resulting from the use of the 
information contained in this document, or warrants that such use 
will be free from privately owned rights.
https://ntrs.nasa.gov/search.jsp?R=19710000330 2020-03-17T02:28:37+00:00Z


The deterioration of intermediate moisture foods

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