Comparing coagulation behaviour of reassembled and native casein micelles during renneting, acid gelation and gastric clotting

Casein micelles are important structuring elements in dairy products due to their coagulation properties during both manufacture and digestion. A possible approach to high-quality dairy alternatives is therefore the assembly of recombinant casein into casein micelles. However, to effectively assemble caseins produced by precision fermentation in functional casein micelles, we first need to understand how the coagulation properties of bovine casein micelles assembled in-vitro might differ from native casein micelles. The aim of this study was therefore to compare the coagulation behaviour of bovine reassembled casein micelles (RCM) to native casein micelles (NCM) during renneting, acid gelation and gastric clotting. Assembly of bovine caseins led to RCM that were able to coagulate in all three conditions. Coagulation behaviour of RCM differed from NCM, forming stronger rennet gels (G′ 82 ± 7 Pa vs 34 ± 12 Pa) and weaker acid gels (G’ 0.7 ± 0.2 Pa vs 3.0 ± 1.3 Pa) than NCM. Gastric clotting behaviour was surprisingly similar. RCM were smaller (120 ± 3 nm vs 157 ± 4 nm), more hydrated (3.89 ± 0.04 g/g vs 2.61 ± 0.07 g/g) and less mineralized (14.8 ± 0.2 mM Ca vs 18.7 ± 1.7 mM Ca) than NCM, which may explain the differences in coagulation behaviour. These results showed that assembly leads to functional casein micelles, with differences in coagulation behaviour relatable to micellar properties. These learnings can inform casein micelle assembly of recombinant casein, as basis for high-quality dairy alternatives. • Reassembled casein micelles coagulated in all three dairy-relevant conditions. • A firmer rennet gel was formed by reassembled casein micelles than by native. • A weaker acid gel was formed by reassembled casein micelles than by native. • Gastric clotting was surprisingly alike for reassembled and native casein micelles. • Learnings can inform future assembly of recombinant casein for dairy alternatives.