title: Effects of Size and Stability of Native Fat Globules on the Formation of Milk Gel Induced by Rennet.
abstract: Rennet-induced gelation crucially impacts cheese structure. In this study, effects of the size and stability of native fat globules on the kinetics of rennet-induced coagulation were revealed by determining the caseinomacropeptide release rate and rheological properties of milk. Moreover, the mobility and stability of fat globules during renneting was revealed using diffusing wave spectroscopy and confocal laser scanning microscopy. By use of a 2-stage gravity separation combined centrifugation scheme, native fat globules were selectively separated into small (SFG, D4,3= 1.87 ± 0.02 μm) and large fat globules (LFG, D4,3= 5.65 ± 0.03 μm). The protein and fat content of SFG and LFG milk were then standardized to 3.2 g/100 mL and 1.2 g/100 mL, respectively. The milk containing different sized globules were then subjected to renneting experiments in the laboratory. Reduction of globule size accelerated the aggregation of casein micelles during renneting, giving a shorter gelation time and earlier 1/l*change. The gel produced from LFG milk was broken due to coalescent fat globules and generated coarser gel strands compared to the finer strands formed with SFG milk. Structural differences were also confirmed with a higher final storage modulus of the curd made from SFG milk than that from the LFG. In conclusion, the size of fat globules affects the aggregation of casein micelles. Moreover, fat globule coalescence and creaming during renneting, also affects the structure of the rennet gel. A better understanding of the size of globules effect on milk gelation could lead to the development of cheese with specific properties.
authors.affiliation: Beijing Advanced Innovation Center for Food Nutrition and Human Health, China Agricultural Univ., China.
authors.forename: Jie
authors.initials: J
authors.lastname: Luo
authors.affiliation: Key Laboratory of Functional Dairy, Co-constructed by Ministry of Education and Beijing Government, College of Food Science and Nutritional Engineering, China Agricultural Univ., China.
authors.forename: Yuhan
authors.initials: Y
authors.lastname: Wang
authors.affiliation: Beijing Laboratory of Food Quality and Safety, China Agricultural Univ., China.
authors.forename: Huiyuan
authors.initials: H
authors.lastname: Guo
authors.affiliation: Beijing Advanced Innovation Center for Food Nutrition and Human Health, China Agricultural Univ., China.
authors.forename: Fazheng
authors.initials: F
authors.lastname: Ren
mesh_terms: D000818:Animals; D002364:Caseins / Q000737:chemistry*; D002611:Cheese; D012085:Chymosin / Q000737:chemistry*; D004041:Dietary Fats; D005223:Fats / Q000737:chemistry*; D005782:Gels / Q000737:chemistry; D006801:Humans; D007700:Kinetics; D008823:Micelles; D018613:Microscopy, Confocal; D008892:Milk / Q000737:chemistry*; D010316:Particle Size; D010446:Peptide Fragments; D012212:Rheology
chemical_list: D002364:Caseins; D004041:Dietary Fats; D005223:Fats; D005782:Gels; D008823:Micelles; D010446:Peptide Fragments; C065989:caseinomacropeptide; C025350:rennet; D012085:Chymosin
keywords: coalescence; native milk fat globules; rennet induced gel; size