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, D = 1.87 ± 0.02 μm) and large fat globules (LFG, D = 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.

Genetic parameters for cheese-making properties and milk composition predicted from mid-infrared spectra in a large data set of Montbéliarde cows

“…In the present study, the relative content of different fatty acids was not strongly genetically associated with coagulation properties with 1 exception: high levels of C18:0, which has been found to be associated with larger fat globules (Timmen and Patton, 1988), were genetically associated with undesirable coagulation properties (longer curd-firming time and less-firm curds). Our results are therefore in agreement with those of Luo et al (2017) and support their observation that a reduction of fat globule size accelerated the aggregation of casein micelles during renneting and increased curd firmness.…”

“…Logan et al (2015) found that large fat globules, combined with small casein micelles, gave the firmest curds. Luo et al (2017) showed that a reduction in fat globule size accelerated casein micelle aggregation during renneting and led to firmer gels. In the present study, the relative content of different fatty acids was not strongly genetically associated with coagulation properties with 1 exception: high levels of C18:0, which has been found to be associated with larger fat globules (Timmen and Patton, 1988), were genetically associated with undesirable coagulation properties (longer curd-firming time and less-firm curds).…”

Effect of Enzyme Modified Soymilk on Rennet Induced Gelation of Skim Milk

“…Compared with the control and S1, the decrease of ĸ-casein in L1 and H1 had little effect on casein aggregation. The main contributor may be the reduction of protein size in enzyme modified soymilk as monitored by sodium dodecyl sulfate polyacrylamide gel electropheresis (SDS-PAGE), which was similar to the report of Luo et al [25]. They studied the effect of native fat globule size on gel formation, and found storage modulus of the curd with small fat globules was higher than that of the curd with large fat globules.…”

The influence of yak casein micelle size on rennet‐induced coagulation properties

“…As described previously by Luo et al 18 . and Zhang et al ., 8 immediately after addition of rennet (Chr‐Max Powder Extra, 2235 International Milk Clotting units (IMCU)/g; Chr.…”