Series of compounds called humectants were found to decrease rate of browning when added to intermediate-moisture foods. Twenty percent level of humectant can increase shelf life of foods by factor of 5 or 6

Buckle, K. A.

Labruza, T. P.

Warmbier, H. C.

English

NASA Technical Reports Server

. December 1975	 B75-10317 
NASA TECH BRIEF 
Lyndon B. Johnson Space 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. 
Control of Nonenzymatic Browning in Intermediate-Moisture Foods 
.
The problem: 
When stored for long periods of time, many 
dehydrated and intermediate-moisture foods show a 
tendency to lose nutritional value and flavor. Many of 
these deteriorative conditions are brought about by a 
series of chemical reactions classified as "nonenzy-
matic browning". Nonenzymatic browning occurs 
because of a reaction between an amine group and a 
reducing compound; an example of particular interest 
is the reaction between dextrose (a reducing sugar) 
and lysine (an amino acid). Lysine is an essential 
amino acid (meaning it cannot be manufactured by 
the body but must be obtained in the diet) and is 
found as a part of protein molecules. When the lysine 
reacts with the sugar, the digestibility of the entire 
protein may be lowered, and the nutrient value of the 
lysine is lost. The only allowable food additives known 
to inhibit this reaction were sulfite compounds, but 
these destroy the B-complex vitamins in protein-based 
foods. 
The solution: 
A series of compounds, called humectants, are 
known to have an affinity for water and are able to 
control the water content of materials with which they 
are mixed. Several of these humectants have been 
tested and found to control nonenzymatic browning in 
intermediate-moisture foods. 
How it's done: 
Several glycols that are humectants (propylene 
glycol, glycerol, butylene glycol, and sorbitols) were 
found to decrease the rate of browning when added to 
intermediate-moisture foods. A 20-percent level of 
humectant can increase the shelf life of foods by a 
factor of 5 or 6, and even a 5-percent level can 
significantly decrease the rate of nonenzymatic 
browning. 
The effect of the humectants was found to depend 
upon the relative volume of the liquid phase developed 
in the food, its viscosity, and the interactions with the
food surface. The rate of browning had been 
previously considered to depend only on the water 
activity (aw) which is related to the amount and 
availability of water in the food. However, these 
studies have shown that the browning rate increases 
with aw to a maximum and then declines as more 
water is added. (The addition of more water is not an 
acceptable method of protecting against browning as 
it increases the food susceptibility to bacteriological 
growth.) 
It was found that the browning rate is also related 
to the viscosity of the aqueous phase in the food. 
Apparently, up to a certain point, increased water 
content decreases viscosity and increases browning. 
After this point, the addition of further water acts as a 
dilutant to decrease the liquid-phase concentration of 
the reacting compounds, and the browning rate 
decreases. 
Note: 
Requests for further information may be directed 
to:
Technology Utilization Officer 
Johnson Space Center 
Code AT3 
Houston, Texas 77058 
Reference: T5P75-10317 
Patent status: 
Inquiries concerning rights for the commercial use 
of this invention should be addressed to: 
Patent Counsel 
Johnson Space Center 
Code AM 
Houston, Texas 7705 
Source: K. A. Buckle, T. P. Labuza,

and H. C. Warmbier of 
University of Minnesota

(MSC-14835) 
Categories: 04 (Materials) 
05 (Life Sciences) 
This document was prepared under the sponsorship of the National
	
Government assumes any liability resulting from the use of the 
Aeronautics and Space Administration. Neither the United States
	
information contained in this document, or warrants that such use 
Government nor any person acting on behalf of the United States
	
will be free from privately owned rights.
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Control of nonenzymatic browning in intermediate-moisture foods

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