Rheological Properties of Rennet‐induced Gels During the Coagulation and Cutting Process: Impact of Processing Conditions

Abstract

The effects of gelation temperature (GT), pH, milk solids nonfat (MSNF) content and aging time on the small and large deformation rheological properties of rennet‐induced skim milk gels were studied. Small amplitude oscillatory rheometry (SAOR) was used to study gel formation. A constant shear rate was applied to gels of various ages to try to simulate the cutting process used in cheese vats. Second‐order polynomial models successfully predicted (R2 ≥ 0.83) the relationship between processing parameters and rheological properties of gels. The processing parameters – gelation pH, GT and MSNF – had a significant effect on the rheological properties of rennet‐induced gels. The type and the nature of bonds in these networks and the time scale of applied deformation affected the rheological properties of rennet gels. As time after rennet addition increased, storage modulus, loss modulus and yield stress values increased. This resulted from an increase in the number and strength of bonds with time. The yield strain decreased with time probably because of rearrangements in the network making the gel shorter/brittle in texture. When the impact of the time scale of the applied deformation was compared between the small (storage modulus as a function of frequency) and large (yield stress as a function of constant shear rate) deformation properties of rennet‐induced gels, similar power law exponents were obtained. This similarity presumably reflects the type and relaxation behavior of bonds in this casein network. These results identify the impact of several important processing variables on both the small and the large deformation rheological properties of rennet‐induced gels, which could be useful in identifying gelation properties that improve cheese yield.

Rheological and physical properties of camel and cow milk gels enriched with phosphate and calcium during acid-induced gelation

“…3c, d). These results were in agreement with those of Ramasubramanian et al (2014) who observed an increase of G 0 for calcium-induced cow milk gels with increase of frequency from 0.1 to 10 Hz, reflecting that the formed bonds in the gels matrix have less time to relax when the time scale of the applied stress is shorter (Mishra et al 2005). Similar results for control milk gels were obtained with added phosphate (Fig.…”

The effect of pH at renneting on the microstructure, composition and texture of Cheddar cheese

“…The influence of milk pH at renneting (often referred to in other studies as the gelation or coagulation pH) on the properties of rennetinduced gel has been reported by various groups (Daviau, Famelart, Pierre, Goudedranche, & Maubois, 2000;Esteves, Lucey, Wang, & Pires, 2003;Hannon et al, 2006;Lucey, Johnson, & Horne, 2003;Mishra et al, 2005;Zoon et al, 1989). These reports offer valuable insights but are often limited to gels made using skim milk (Daviau et al, 2000;Esteves et al, 2003), non-fat milk (Mishra et al, 2005), ultrafiltered milk (Hannon et al, 2006) or reconstituted skim milk powder (Mishra et al, 2005).…”

“…These reports offer valuable insights but are often limited to gels made using skim milk (Daviau et al, 2000;Esteves et al, 2003), non-fat milk (Mishra et al, 2005), ultrafiltered milk (Hannon et al, 2006) or reconstituted skim milk powder (Mishra et al, 2005). Furthermore, the microstructure of the gel, curd or cheese and the composition of the final cheese product has not been the focus in the majority of these studies.…”

“…The pH of milk also influences the aggregation of casein micelles during cheese making due to the effect of pH on Ca 2+ activity (Mishra, Govindasamy-Lucey, & Lucey, 2005). The structure of CM still has not been unequivocally determined and there are different models of CM.…”

“…However, this variation in the surface potential is unlikely to have a significant effect on the aggregation rate. The increased aggregation rate is most likely due to the greater number of Ca 2+ ions that may provide salt bridging between the micelles (Mishra et al, 2005). Extensive solubilisation of CCP at very low pH may cause disassociation of casein micelles.…”