The early stages of enzymatic and acid coagulation of homogenized milk were investigated using diffusing wave spectroscopy and rheology. The aggregation behaviour of homogenized milk was compared to that of skim milk. The presence of fat globules and their interfacial properties affected the enzymatic and acid-induced coagulation of casein micelles. Fat globules in homogenized milk participated in the protein network (as active fillers), although differences were shown in acid-induced coagulation of homogenized milk depending on when heating was applied. In addition to comparing the behaviour of homogenized milk with skim milk, polysorbates were added to homogenized milk to cause displacement of proteins from fat interface while maintaining protein composition and fat globules' sizes comparable to homogenized milk. This allowed the study of the behaviour of inactive fillers during milk gelation. It was also found that polysorbates alter casein micelles' sizes and their surface reactivity, affecting the rennet but not the acid coagulation properties of skim milk.
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