The distribution of rennet activity between the cheese aging process and whey is not influenced by the association of enzymes with caseins

Abstract

The division of rennet in cheesemaking is split between the curd and whey, influencing the taste and texture of aged cheeses. Our study aimed to examine how raising the protein concentration in reconstituted skim milk (up to 8.8 %) affects the distribution of calf rennet activity (RA) in rennet curds produced through two methods: renting only and renneting with glucono-δ-lactone (GDL) to achieve slow acidification. The distribution of rennet activity (RA) into curds increased as the concentration of skim milk rose, ranging from 8.6 % to 29.1 % without acidification, and from 6.5 % to 19.4 % when combined with slow acidification. This increase seemed to be related to the retention of moisture and protein. Surprisingly, the concentration of residual RA in the whey (measured in international milk clotting units, IMCU/mL) remained unaffected and remained consistent with the initial IMCU/mL of milk. This suggests that the division of RA between curd and whey is not influenced by the association of enzymes with caseins (CNs). Instead, it is possible that the strength of interactions between CNs themselves plays a significant role. These findings could be valuable for research focused on enhancing the cheese aging process.

Keywords: Calf rennet; Milk concentration; Rennet activity partitioning; Rennet curd; Rennet whey.

Fig. 1

Experimental design.

Fig. 2

Displays two typical chromatograms: (A) the initial heptapeptide (Pro–Thr–Glu–Phe–[NO₂–Phe]–Arg–Leu) and (B) the heptapeptide residue and the resulting hydrolysate ([NO₂–Phe]–Arg–Leu) after incubation at 30 °C for 25 min with the ultracentrifugal supernatant of reconstituted skim milk containing 0.02 International Milk Clotting Units (IMCU) of calf rennet. Glucono-δ-lactone (GDL) and rennet activity (RA) are denoted abbreviations in this context.

Fig. 3

Illustrates the alterations in peak areas of the hydrolysate of a synthetic heptapeptide caused by the action of calf rennet, which was introduced into ultracentrifugal supernatants (peak area-control) or recovered in whey (peak area-whey). Additionally, the concentration of residual rennet activity (RA) in terms of International Milk Clotting Units (IMCU) was estimated in the whey obtained from reconstituted skim milk with varying protein concentrations. Panel (A) represents samples that were treated with glucono-δ-lactone (GDL), whereas panel (B) portrays samples without GDL.

Fig. 4

Alterations in the yields of fresh curd and the retention of total protein (T-Protein), moisture, and rennet activity (RA) were observed in rennet curds manufactured from skim milk that had been reconstituted with varying levels of protein concentration. (A): samples containing glucono-δ-lactone (GDL), and (B): samples lacking GDL.