Effect of relative humidity on the oxidative and physical stability of encapsulated milk fat |
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Authors: | N Hardas S Danvirivakul J L Foley W W Nawar P Chinachoti |
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Affiliation: | (1) Department of Food Science, University of Massachusetts, 01003 Amherst, Massachusetts |
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Abstract: | Milk fat was used in this work as a model to study the effects of humidity and physical properties on lipid oxidation. Although
milk fat is considered a relatively stable fat because of its low content of unsaturated FA, it can oxidize significantly
under certain conditions, as observed, for example, in the case, of dairy-based powders. Humidity and physical properties
have a profound influence on the oxidative stability of powders, containing fat, and these factors affect the surface and
encapsulated fractions of the fat differently. To examine these effects, encapsulated milk fat powders were stored under conditions
of controlled relative humidity. Oxidation of the encapsulated fat as assessed by measurements of PV, losses of FA, and hexanal
production increased, with increasing relative humidity (RH). At higher RH, moisture penetrates into the hydrophilic wall,
interacting with and plasticizing the components, thereby making them less effective as moisture and oxygen barriers. Total
oxidation of the powders was strongly influenced by the extent of oxidation in the encapsulated fraction (>98% of total lipids)
although the surface fat fraction was oxidized more rapidly. Better protection against oxidation was obtained when fats were
encapsulated and stored at 14 and 44% RH than at 52% RH. |
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Keywords: | Encapsulation oxidation physical stability relative humidity spray drying |
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