Abstract
Milk protein is often standardised prior to cheese-making using low concentration factor ultrafiltration retentate (LCUFR) but the effect of LCUFR addition on the microstructure of full fat gel, curd and Cheddar cheese is not known. In this work, Cheddar cheeses were made from cheese-milk with or without LCUFR addition using a protein concentration of 3.7%–5.8% w/w. The fat lost to sweet whey was higher in cheese made from cheese-milk without LCUFR or from cheese-milk with 5.8% w/w protein. At 5.8% w/w protein concentration, the porosity of the gel increased significantly and the fat globules within the gel and curd tended to pool together, which possibly contributed to the higher fat loss in the sweet whey. The microstructure of cheese from cheese-milk with a higher protein concentration was more compact, consistent with the increased hardness, although the cohesiveness was lower. These results highlight the potential use of LCUFR for the standardization of protein concentration in cheese-milk to 4%–5% w/w (equivalent to a casein to total protein ratio of 77%–79% w/w) to increase yield. Beyond this concentration, significant changes in the gel microstructure, cheese texture and fat loss were observed.
Highlights
The protein concentration of milk varies according to the season, weather, feed type, stage of lactation and breed of lactating cows
The number of the total lactobacilli present was variable between treatments, possibly reflecting variation that can be encountered at a pilot scale in an industrial setting. This pilot scale study highlights the potential of using cheese-milk with increasing concentrations of protein to increase the total cheese yield of Cheddar cheese by up to 6% w/w and yield in dry matter by up to 4% w/w for every kg of cheese-milk
These modifications result in minimal changes to the cheese composition, provided the setting time and starter concentration are adjusted during cheese making
Summary
The protein concentration of milk varies according to the season, weather, feed type, stage of lactation and breed of lactating cows. Studies on the effect of LCUFR on the microstructure of the gel, curd and cheese are, limited. In a previous study where skim milk retentate was used to give 3%–19% w/w protein, the gels formed from UF concentrated milk were much firmer, as the increased milk protein concentration decreased the mean distance between casein micelles [10]. This proximity increased the rate of aggregation of para-casein micelles, as aggregation depends on the number of effective collisions. This study provides useful insight into the structure of gels made using UF concentrated skim milk, no cheese making was performed to examine the effect of the altered gel structure on the microstructure of curd and final cheese. The influence of microstructure on the composition, texture and yield of the final cheese product is examined
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