Abstract
In this study, texture analysis method was used for the determination of rennet flocculation time (tfloc) and rennet clotting time (tclot) of rennet-induced reconstitued milk samples with different CaCl2 concentrations. The rennet flocculation time (RFT) and rennet clotting time (RCT) were also determined by using the Berridge test and sensory evaluation. The hardness value versus renneting time curves derived from texture analysis gave a good modified exponential relationship for each CaCl2 concentration and the curves were used to calculate flocculation time and clotting time parameters. It was found that the parameters (tfloc and tclot) appeared strongly correlated with RFT and RCT, respectively. Texture analysis was proved as a suitable method to control the rennet-induced coagulation and determine the rennet clotting time. It was also determined that enrichment of milk with CaCl2 leaded to a decrease in flocculation and clotting times and an increase in rate of clotting and gel hardness.
Highlights
The first stage of cheese manufacture is the conversion of liquid milk to cheese curd
The hardness values of the samples measured during 70 min after the addition of rennet were shown from Figure 1
It was observed that the hardness was increased to a maximum and it was kept almost constant for all CaCl2 concentration during the renneting
Summary
The first stage of cheese manufacture is the conversion of liquid milk to cheese curd. After the addition of chymosin to the milk, there is little apparent reaction for some time and the milk coagulates rapidly During this lag phase, the enzyme hydrolyses the κ-casein which stabilizes the casein micelles. Renneted micelles appear to be incapable of aggregating until about 60% 80% of their κ-casein has been destroyed, after which the concentration of micelles capable of aggregating increases rapidly. This behavior can be explained either by the loss of surface charge during renneting or by loss of steric stabilization [1]
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