| Abstract
| - Thermal association of β-lactoglobulin AB (β-Lg) purified fromCheddar whey, a major source ofcommercial whey ingredients, was studied by dynamic light scattering(DLS). The objective was toobserve the effect of the process and/or possible micromolecules inthis β-Lg source of commercialrelevance. Protein solution (8%, w/v) was heated (25−90 °C)at pH 3.5, 7, and 9.0. DLS data wereanalyzed according to the method of Cumulants for apparent meandiameter and by the Continmethod for percentile size distribution. Data indicated gradualchange in mean size that startedat 35 °C, much below the reported denaturation temperature of 70°C. Moreover, the percentiledistribution of various micrometer- and submicrometer-sized aggregatesdiffered at the differentpH values studied, conceivably indicating conformational alterationlimiting spatial freedom forintermolecular association. Monomeric/dimeric form (1−9 nmrange) was seen only at pH 3.5 attemperatures below 65 °C. The ubiquitous aggregate size rangewas 100−599 nm (Agg3), andgreatest changes in aggregate size and distribution were detectedaround 70 °C. Micrometer-sized(>1000 nm) aggregates were formed at this temperature and above,concomitant with disappearanceof Agg3. On the basis of polydispersity data and rate kineticsdependent on the disappearance ofAgg3, the association tendency between 25 and 70 °C was in the orderpH 7.0 > pH 3.5 > pH 9.0. Keywords: Thermal; association; gelation; whey;β-lactoglobulin
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