Yield, Sensory Properties, and Nutritive Qualities of Quarg Produced from Lactose-Hydrolyzed and High Heated Milk

Abstract

Quarg was produced from homogenized milk with or without lactose hydrolysis or prior heating to 95°C for 15min. Increased yields of 9.2 and 13.3% were obtained for unhydrolyzed and hydrolyzed high heated milk, respectively, in comparison with the corresponding unheated milk. The recovery of whey proteins in quarg from high heated milk was 40.5% in unhydrolyzed milk and 42.7% in hydrolyzed milk. No effect of lactose hydrolysis on yield was observed. The time required to attain the desired pH 4.5 in the quarg fermentation was reduced in lactose-hydrolyzed milk by 7.1 and 4.6% for the unheated and high heat-treated milk, respectively. The results of sensory evaluation indicated that heating resulted in graininess and hydrolysis plus high heating induced an unclean flavor in the quargs. In nutritional evaluation by bioassay methods, no differences were found in protein digestibility among any of the quargs studied; however, protein efficiency ratio, biological value, and net protein utilization values indicated that lactose hydrolysis plus high heating had a negative effect on the nutritional value of milk. Amino acid analysis of quarg samples indicated possible lowering of lysine content for the hydrolyzed quargs.