Composition, Gel Properties and Microstructure of Quarg as Affected by Processing Parameters and Milk Quality

Abstract

Abstract Qarg cheese was manufactured on a small scale from batches of milk which had received different heat treatments (72°C for 15 s or 90°C for 10 min), different levels of added KIO 3 (0 or 0.1 m m ) and different levels of plasmin proteolysis premanufacture (none or 6 mg L -1 plasmin added and incubated at 37°C for 6 h). Plasmin digestion premanufacture affected the microstructure (changed appearance in electron micrographs) and rheology (lower G ′ values) of quarg. Plasmin digestion also increased cheese moisture ( P P β -lactoglobulin and α -lactalbumin levels in whey were decreased by this treatment ( P 3 before high-heat treatment reduced α -lactalbumin denaturation, but gave a cheese of similar composition to that made from high heated milk controlled. Rheological properties of the KIO 3 -treated samples were poor, and microstructures appeared different. Milk quality (plasmin content) and processing conditions used (extent and nature of whey protein denaturation) appear to significantly affect the composition and structure of quarg.