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Comparison Of Jersey And Holstein-Friesian Milk Composition And Coagulation Properties
Holstein-Frisian milk is increasingly blended with Jersey milk by cheesemakers to improve cheese yield. However, to date, no study has investigated the impact of blending on milk composition and properties. The objective of this study was to compare the composition and milk coagulation properties of Jersey and Holstein-Friesian milk produced in the United Kingdom. In addition, the effect of blending the two types of milk at different ratios (0 to 100% Jersey milk in Holstein-Friesian at 10% intervals), was evaluated. This knowledge could assist cheesemakers in optimising the blending process.
Raw bulk milk composition from both breeds was measured every three months over a year (n=55). Significant variations in fat, protein, fat to protein ratio, casein, casein to protein ratio, fat globule size (D(4.3), D(0.5) and span), casein micelle size and titratable acidity were observed (P<0.05). However, no significant difference in lactose, urea, somatic cell count, calcium ions, fat globule surface area mean particles D(3.2) and pH were seen. Blending the milks resulted in a linear trend for all significant variables with the exception of the fat globule volume mean diameter D(4.3) and casein micelle size which followed a quadratic trend (P<0.05), which is believed to be due to change in the mineral balance.
Coagulation properties were measured using a C-VOR controlled stress rheometer using raw milk at natural pH. Rennet Coagulation Time (RCT) (min) was defined as at the time at which a firmness of 0.5 Pa was attained, Curd Firmness (CF) (Pa) was taken 10 min after coagulation and Curd Firming Rate (CFR) (Pa min-1) was calculated from the time for the gel to firm from 0.5 Pa to 2 Pa. Mean RCT of Holstein-Friesian was 58.7 min compared to 24.0 min for Jersey milk (P<0.001). CF was 2.01Pa compared to 12.50 Pa and CFR 0.14 Pa min-1 compared to 0.49 Pa min-1 respectively (P<0.001). CFR increased linearly with increase percentage of Jersey milk (R2=0.940, P=0.003) whereas RCT and CF followed a quadratic trend with increased percentage of Jersey milk (R2=0.9903, P=0.007 and R2=0.9965, P=0.001 respectively). This could be linked to the non-linear trend found in fat globule volume mean diameter D(4.3) and casein micelle size.
This study demonstrates that Jersey milk composition and coagulation properties are more suited for cheese making than Holstein-Friesian and additionally indicated that blending the two milk types gave beneficial synergistic effects for cheese.
Keywords:
Milk composition, Milk coagulation, Breed