ABSTRACT

The nutrient composition, mineral contents and anti-nutrient properties of fresh, steamed and microwaved tofu coagulated with grape fruit was studied. The results showed that moisture content ranged from (31.71% - 64.83%), crude protein (16.46% - 17.65%), fat content (2.73% - 3.85%), crude fibre (0.32% - 0.94%), ash content (1.18% - 1.83%), carbohydrate contents (14.45% - 44.02%) and energy value (148.19 Kcal - 281.33 Kcal). Microwaved tofu sample had better proximate composition compared to fresh and steamed tofu samples. Mineral contents in fresh tofu samples were higher than those obtained in heat treated tofu samples and the contents ranged from 109.27 mg/100 g - 110.49 mg/100 g, 121.33 mg/100 g - 122.14 mg/100 g, 57.49 mg/100 g - 58.58 mg/100 g, 3.83 mg/100 g - 4.21 mg/100 g and 3.76 mg/100 g - 4.03 mg/100 g for calcium, magnesium, potassium, sodium and iron respectively and Magnesium was found to be the most abundant mineral in the tofu samples and then calcium. Anti-nutrient content was found to reduce in the heat treated products, particularly in microwaved (MVT) tofu sample. Anti-nutrient values ranged from 0.90 mg/100 g - 1.56 mg/100 g for tannin, 0.65 mg/100 g - 0.86 mg/100 g for saponin, 0.73 mg/100 g - 0.95 mg/100 g for phytate and 0.22 mg/100 g - 0.35 mg/100 g for oxalate. Sensory analysis revealed that the microwaved sample possessed better organoleptic property with a general acceptability rate of 5.05. Furthermore, this study have demonstrated the influence of heat treatment on tofu samples as the chemical composition of the sample increased and decreased with each heat treatment (steaming and microwaving) administered. The proximate analysis showed that there was a notable increase in the crude protein content, fat content, crude fibre, ash content, carbohydrate and energy value, meanwhile there was a marked reduction in the moisture content thus improving the shelf life of tofu. The mineral analysis showed that there was a reduction in the calcium, magnesium, potassium and sodium content but an increase in the iron content, thus consuming tofu together with other iron rich food could reduce the occurrence of Anemia. The antinutrient content was reduced with heat treatment and was below the permissive level making tofu safe for human consumption. The sensory evaluation showed that the microwaved tofu had a higher acceptance rate than all other tofu samples. Microwaved tofu may be recommended to individuals who suffer from certain health challenges, for example those who suffer from Protein Energy Malnutrition, those who seek to reduce their fat intake, vegetarians, vegan and even non vegetarians who seek to reduce their meat and meat product consumption and diabetes patients but in controlled portions.