HEAT-STABILITY AND SENSORY QUALITY OF PROTEIN-STANDARDIZED 2-PERCENT FAT MILK

The protein content of 2 % fat milk was increased from 3.44 % to value s in the range similar to 3.6-4.0 % by fortification with a dried isol ate of alpha-lactalbumin (alpha-is) or skim milk: ultrafiltration rete ntate (SMR), or reduced in the range similar to 3.2-2.0 % by mixing wi th skim milk ultrafiltration permeate (SMP). The heat stability was de termined at unaltered pH (similar to 6.7) and 140 degrees C, by measur ing the heat coagulation time or the mass of pellet obtained after low speed centrifugation (900 x g) of the heated milk. Triangle tests wer e used to determine the effect of protein standardization on the senso ry quality of 2 % fat milk. The addition of increasing amounts of alph a-is to 2.0 % fat milk led to a progressive decline in heat stability, probably due to the presence of low amounts of beta-lactoglobulin in the alpha-is. Milk enriched with increasing amounts of SMR exhibited a very gradual decline in heat stability. Reducing the protein content by addition of SMP, led to an increase in heat stability. It was very difficult to differentiate sensorically between normal 2.0 % fat milk and 2.0 % fat milk with an increased or decreased protein content, ind icating that milk protein had a low sensory impact.