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EFFECT OF TEMPERATURE AND RATE OF ACIDIFICATION ON THE RHEOLOGICAL PROPERTIES OF ACID SKIM MILK GELS
Author(s) -
ANEMA SKELTE G.
Publication year - 2008
Publication title -
journal of food processing and preservation
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.511
H-Index - 48
eISSN - 1745-4549
pISSN - 0145-8892
DOI - 10.1111/j.1745-4549.2008.00230.x
Subject(s) - skimmed milk , chemistry , rheology , yield (engineering) , food science , materials science , metallurgy , composite material
Acid skim milk gels were formed by acidifying milk samples to pH 4.6 at different rates (1–7 h) and at different temperatures (25–40C). At each temperature, the stiffness (storage modulus or G′ ) of the gel increased with increasing acidification time up to 3 h, with smaller changes at longer acidification times. The tan δ of the set gels was independent of the acidification temperature, but decreased markedly with increasing acidification time. The yield stress and yield strain of the acid gels decreased with increasing acidification time. Acidification temperature generally decreased the yield stress and yield strain, although a different behavior was observed at 25C (for yield stress) and 40C (for yield strain). These results are related to changes in the casein micelles on acidification, and the effects of temperature and rate of acidification on these changes.PRACTICAL APPLICATIONS Food gels can be prepared from dairy products, and these are often formed by the acidification of the food system. This research has shown that it is possible to substantially alter the textural properties of set acid skim milk gels by altering the temperature at which the gels are formed and/or the rate of acidification. Therefore, it may be possible to produce acid milk products with a range of textural characteristics by carefully controlling or manipulating the acidification conditions during product manufacture.