The effect of cooking and washing temperature during pilot‐scale rennet casein manufacture on casein hydration characteristics in disodium orthophosphate solution

Abstract

Variations were observed in the hydration behaviour of rennet caseins in a solution (0.4%, w/w) of disodium orthophosphate (DSP). These caseins were manufactured on a pilot scale from curds cooked at 45, 65 or 75°C and from curds washed at a hot‐wash temperature of 60, 70, 78 or 86°C. The influence of cooking temperature and hot‐wash temperature on various compositional characteristics, the electrophoretic resolution and particle size parameters of the milled rennet caseins were determined. Relationships between all of these parameters and hydration characteristics in DSP solution were also investigated. Cooking temperature or hot‐wash temperature did not influence electrophoretic resolution, the level of Maillard reaction compounds or the particle size parameters of the caseins. Increasing the cooking temperature increased whey protein levels and decreased calcium levels in the curd, leading to slower hydration rates. This suggested that increased whey protein denaturation and its precipitation onto the rennet casein curd retarded subsequent rennet casein hydration. Hot‐wash temperature influenced certain aspects of rennet casein hydration in 0.4% (w/w) DSP; however, the hydration characteristics of these caseins did not appear to be related to any of the other characteristics investigated.