Influence of Cross-linked Waxy Maize Starch on the Aggregation Behavior of Casein Micelles During Acid-induced Gelation |
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Authors: | Zohra Azim Marcela Alexander Max Koxholt Milena Corredig |
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Institution: | (1) Food Science Department, University of Guelph, Guelph, ON, N1G 2W1, Canada;(2) National Starch Food Innovation, 10 Finderne Avenue, Bridgewater, NJ 08807, USA; |
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Abstract: | The influence of cross-linked waxy maize starch on the aggregation behavior of casein micelles was investigated using a combination
of physico-chemical techniques. Milk was homogenized at two different temperatures (55 and 65 °C) and then heated at 95 °C
for 5 min in a pilot scale system. The possible interactions between modified starch and milk proteins during lactic acid
fermentation were evaluated. While 1% starch did not show differences in the whey protein complexes formed during heating
compared to milk with no starch (as measured by size exclusion chromatography), a higher (2.5%) concentration of starch clearly
showed an increased amount of heat-induced whey protein aggregates. The gelation pH also increased significantly with 2.5%
starch compared to that of the control samples. The storage modulus (G′) increased with increasing levels of starch, and confocal
microscopy confirmed that the microstructure of the casein gels was altered by the presence of modified starch. Milk-starch
mixtures preheated and homogenized at 55 or 65 °C exhibited similar physico-chemical behavior during acidification. The results
suggested a lack of interaction between starch granules and casein micelles during acidification, and scanning electron microscopy
images collected with a self-assembled monolayer technique also confirmed that starch granules were not attached to milk caseins
but only embedded in the protein gel matrix. |
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