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Manufacture of high protein yogurts with Low-Ca MPC
The purpose of this study was to evaluate and compare the effects of high protein yogurt produced with calcium reduced milk protein concentrate (low-Ca-MPC) and regular milk protein concentrate (MPC). The yogurt properties studied were viscosity, syneresis and quantity of acidifying agent required for the yogurt. Reduced Ca MPC was manufactured from ultra and dia-filtration process of skim milk that was injected with CO2 prior to and during the ultra-filtration process. Three different high protein yogurt formulations containing 8% protein were prepared with regular MPC (T-1), low-Ca-MPC with the pH neutralized to 6.7 (T-2) and low-C-MPC at pH 5.9 (T-3). The MPC was the primary source of protein contributing approximately 97% in the all the formulations and the remaining 3% was coming from de-proteinized whey which was used for balancing the lactose content of each formula. All three treatments were manufactured in triplicate from three replicates of low-Ca MPC and regular MPC. Each yogurt formulation was heat treated to 93°C, held for 6 min and then cooled to 45°C. The formulations were then acidified with Glucono-delta-Lactone (GDL) at 45°C and then incubated for 2 hrs. The amount GDL required to reach a pH of 4.6 for 30g of yogurt was 0.7g, 0.6g and 0.55g respectively for T-1, T-2 and T-3. The T-3 yogurt formulation required 21% less GDL to reach the same pH due to the lower initial pH of the T-3 formulation. The T-2 yogurt formulation also used 14% less GDL than T-1 even though the initial pH of both the formulations was same. The undisturbed low-C yogurt formulations (T-2 & T-3) had approximately 40% higher viscosity than the control T-1 formulations. However after stirring all yogurt formulations had similar viscosities. The control yogurt formulation T-1 also had 10% higher syneresis than T-2 and T-3 yougurts. These results indicate that, the use of low-Ca MPC reduces both syneresis and amount of acid required to ferment yogurt.
Keywords: Low-Ca MPC, Calcium, Yogurt, MPC