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The emulsification properties of an isolate of β-lactoglobulin (β-LGI) and a whey protein fraction (WPF) of reconstituted skim milk were studied in a milk-based environment containing anhydrous milk fat at 4 and 18% by modifying protein concentration. At a similar protein-to-fat ratio, fat content per se was not associated with changes in initial particle size, but was related to stability during storage. In the more concentrated emulsions, creaming was inhibited and no longer affected time-dependent aggregation of fat globules, except under the most extreme conditions (i.e. in the presence of a higher proportion of α-lactalbumin, at high initial particle size and at high storage temperature). However, aggregation was enhanced by the presence of a higher proportion of α-lactalbumin, which was detrimental to physical stability. Using laser desorption mass spectroscopy, the molecular mass of a significant proportion of WPFs whey protein was observed to be increased, possibly as a result of lactolation. In addition, β-LGI contained some calcium, which slightly increased the concentration of calcium in emulsions made with β-LGI. These differences in molecular mass and calcium concentration did not enhance the stability of emulsions prepared with β-LGI over that of those prepared with WPF. |
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