Abstract

Glass transition temperature of pure milk, milk diluted with water, and pure milk in which sugars like glucose, fructose and sucrose were investigated by differential scanning calorimetry (DSC). The glass transition temperature T_g of pure milk (containing 89.2 kg water and 10.8 kg total solids per 100 kg milk) varied between -114 to -118^oC. Effect of change in composition of the milk varying the amounts of water and total solids content (77.47, 81.56, 83.81, 84.31, 85.76, 86.69, 89.43, 92.15, 93.16, 95.71 and 96.38 kg water to make each 100 kg milk sample) on the glass transition temperature of milk showed a linear relationship between glass transition temperature and composition of the milk expressed in %moisture content (w.b.). The addition of sugars (glucose, froctose and sucrose) also showed a significant change in glass transition temperature. Under applied conditions, adulterations in milk by dilution with water only and water and sugars were detectable even at 0.5 and 5 % respectively.

Key words: Milk, glass transition temperature, differential scanning calorimetry, adulteration.