Effects of coagulation methods on quality of cream cheese

Abstract: As a kind of fresh cheese spread, spreadability is one of the most important textural properties of cream cheese. Renneting and acidification, as two important coagulation methods, have significant effects on spread ability. There have been great advances in understanding of the effects of acid or rennet induced coagulation on the spreadability of cream cheese, whereas less is understood about how combination of acid and rennet affects its spreadability. So the objective of the present study was to determine the effects of combined acid and rennet on the spread ability of cream cheese.Combined with texture profile analysis (TPA) and rheological technique, we investigated the effects of coagulation methods on chemical compositions, cheese yield and the spreadability of cream cheese. The coagulation methods in this research included strictly acidification with no rennet (NR), strictly renneting with no acid (NA) and combined acid and rennet with different acidification degrees, rennet with lower acid (RLA), rennet with medium acid (RMA) and rennet with higher acid (RHA).Cream cheeses with pH values near the isoelectric point exhibited higher moisture, lower fat and protein than those with higher pH values. With combination of acid and rennet, as the cutting pH rising from 4.6 to 6.1, the content of fat and protein in cheese were increased, while the water content was decreased to 47.75%. These results confirmed the remarkable effect of coagulation methods on the composition of cream cheese. On the other hand, coagulation methods also affected the cheese yield and component recoveries. In the rennet or combined acid and rennet induced cheese, there was a significant increase in the yield and component recoveries. In contrast acid-induced cream cheese had lower yield and component recoveries. This could arise from the different changes in the interactions between the casein micelles as a result of rennet and acid action in two ways. Eventually, coagulation methods changed the spreadability. RHA with the lowest shear work (19.23N?s) and yield stress (195.67 Pa) has especially remarkable in spreadability. It was found that rennet-induced cream cheese had higher hardness and was the most difficult to spread. Acid-induced cream cheese had medium spreadability. With the decrease of pH, cream cheese with a combination of acid and rennet coagulation had moderate hardness, smoother texture and was easier to spread.These results may be attributed to the complex interparticle forces in combination of acid and rennet gels. In rennet gels, casein micelles bond together through hydrophobic and Ca2+-bridging interactions while the aggregating particles coagulate through attractive interactions in the acid gels. So the forces in combination of acid and rennet gels would be different from these strictly acid or rennet gels. For the RHA gels in our research, it formed special structure with the interactions which may contain hydrophobic, Ca2+-bridging and attractive interactions. Rennet with higher acid (RHA) was the best way to produce cream cheese for better spreadability. Apparently, with the coagulation method of combined rennet and acid, the spreadability of cream cheese could be significantly improved.