THE EFFECT OF PROCESSING TREATMENTS ON MILK COAGULATION WITH RENNET AS MEASURED BY VISCOSITY-TIME CURVE | ||||
| Journal of Food and Dairy Sciences | ||||
| Article 3, Volume 29, Issue 6, June 2004, Page 3361-3374 PDF (1.68 MB) | ||||
| Document Type: Original Article | ||||
| DOI: 10.21608/jfds.2004.240380 | ||||
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| Authors | ||||
| A. M. M. Metwally; Hoda M. EI-Zeini | ||||
| Dairy Science & Technology Department, Fac. of Agric.,Cairo University | ||||
| Abstract | ||||
| The change in milk viscosity upon addition of rennet was used to study the effect of various milk treatments on cenneUng reaction. The change in milk viscosity after the addition of rennet when recorded versus time gave a curve that passed through 4 turning points (T, to T .). An induction period with no change in viscosity (T,) ended with a rise in the viscosity to a first maximum (T2) then viscosity decreased to a minimum with milk still in the liquid form (TJ) followed by a rapid increase to reach a final maximum forming a plateau (T 4) when coagulation occurred. The effect of milk cooling, freezing. heat treatments, calcium addition. rennet concentration, addition of NeCI and homogenization on vlscosity-tlme curve was studied. Milk cold storage. freezing. heat treatments and the addition of NaCI elongated the periods of 4 phases periods than of (aw mil~ periods. The delaying effect in descending order was the addition of NaCI > freezing :> cooling > heat treatments. Mosllhe delay was in the tag phase (T,). Heal treatments delay of T, was proportional to the temperature. There was a good correlation with r = 0.98 (p < O.01) between T\ and the temperature. Increasing the concentration of rennel was more effective in correcting the effect of heating than the addition of calcium. Heat treatments caused a large increase in viscosity of the first maximum than the raw milk value. Homogenization was very effective in correcting the effect of milk heat treatments and shortened TI than the value of raw milk. The end of the lag phase (Tr) leading to the first rise in viscosity occurred at a certain amount of casein hydrolysis depending on to milk treatment. | ||||
| Keywords | ||||
| Milk coagulation; Rennet; Viscosity; Milk heat treatments | ||||
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