Effect of Cooking Temperature on Some Quality Characteristics of Soy Milk

The effect of different processing temperatures on some quality characteristics of soymilk was determined. Soybean was processed at varying temperatures (80, 90 and 110°C), to produce soymilk samples A, B and D, with product processed using the normal boiling temperature of 100°C (sample C) as standard. The soymilk products were subjected to physiochemical, microbiological and sensory analyses using standard analytical methods. The moisture and crude fat contents decreased significantly (p＜0.05) with increase in temperature from 92.05 to 89.78% and 2.26 to 2.04% respectively; while the converse was true of crude protein, crude fibre, ash and carbohydrate contents, which all increased significantly (p＜0.05). Total solids and pH increased from 7.95 to 10.90 and 6.50 to 6.58 respectively. The Total Viable Count (TVC) ranged from 1.4×10^3-2.3×10^3 CFU/mL, while yeast and mould count ranged from 0.3×10^2 to 1.2×10^2 CFU/mL, with the lowest values coming from the products processed at 110°C, thus making sample D microbiologically safer than the others. Mean sensory scores for colour and flavour ranged from 5.90 to 7.00 and 5.87 to 8.33, respectively. Though all the soy milk products were acceptable, milk processed at 100°C (sample C) had the highest acceptability score (8.33) followed by samples B (6.60), A (5.89) and D (5.87) in that order. Processing at 100°C gave the best product in terms of all the attributes measured and is therefore, recommended for soy milk processors.