Effect Of Dry Heat Pre-Treatment (Toasting) On The Cooking Time Of Cowpeas (Vigna Unguiculata L. Waip)

ABSTRACT

Cowpea, an important protein food, is used for its nutritional and functional properties. One of the factors limiting its utilisation is its long cooking time. Four Cowpea varieties (Brown beans, Ololca beans, IAR48 and IT89KD-288) were toasted at 105°C, and used to study the effect of dry heat treatment on the cooking time and nutrient composition of Cowpea seeds and also its effect on the functional properties of resultant flour of the Cowpea seed varieties. Toasting reduced the cooking time for Brown and Oloka Cowpea varieties from 55.00-3 1.00 and 70.67-5 1.67 minutes, respectively. The cooking time for JAR48 and IT89KD-288 Cowpea varieties increased from 104.67 to 106.00 and 88.00 to 88.67 minutes, respectively. Moisture, crude protein, crude fat, crude fibre, ash and carbohydrate contents for raw Cowpea samples were in the percentage ranges of: 11.10-19.35, 17.04-23.70, 0.61-2.10, 1.88-4.51, 2.60-3.36, and 55.90-61.58 respectively. For toasted Cowpea samples, they were in the percentage ranges of 6.58- 10.23, 15.62-25.17, 1.02-2.46, 1.92-5.70, 2.12-2.62 and 62.96-64.82, respectively. Bulk density, water absorption capacity, oil absorption capacity, wettability, emulsion capacity, foaming capacity, foaming stability and swelling capacity for raw Cowpea samples were in the ranges of: 0.43-0.72, 0.00-5.00 glml, 0.00-2.17 glml, 84.67- 155.33secs, 48.33-58.67 %, 2.0-9.33 %, 94.57-98.50% and 4.97-6.63 gIg, respectively while for the toasted Cowpea samples, they were in the range of: 0.41-0.64, 1.00-6.00 g/ml, 0.44-2.00 glml, 52.33-101.67 secs, 42.33-54.00 %, 2.00-6.00 %, 96.00-99.00 % and 4.57-4.80g1g, respectively. The results indicate that the cooking time of Cowpea seeds can be reduced significantly on toasting, while maintaining their potential as functional agents in the food industry for nutrition and utilisation. Correlation between the amount of water imbibed by Cowpea seeds and their cooking time was -0.74, but was not significant at p0.05, suggesting that there is no significant relationship between the amount of water imbibed by Cowpea seeds and their cooking time.