EFFECT OF PROCESSING METHODS ON THE PHYSICO-CHEMICAL, MICROBIOLOGICAL AND SENSORY PROPERTIES OF ENRICHED MAIZE SNACK (IPEKERE AGBADO)

Abstract

The development of cheap, readily available and nutritious snack from indigenous crops (maize and cowpea blend) was done and evaluated. The objective of the study was to increase the nutrient content of the snack and improve the livelihoods of the rural consumers. The effect of processing method; oven-drying and oil-frying on the quality attributes of the snack was also investigated. Four blends were produced from maize and cowpea flours in the following ratios of maize:cowpea; 90:10, 80:20, 70:30. Stiff paste of the blends was divided into two parts; the first part was molded and deep-fried in palm oil while the second part was oven-dried at 150 oC for 2 hours. Physico-chemical analyses (proximate, mineral and functional properties), microbiological and sensory evaluation were carried out on the flour blends and the snacks produced. The proximate result showed that for the blends, protein content ranged from 8.85 to 10.52 %, total ash, 1.55 to 1.93 %; fat content, 10.50 to 11.96 %; moisture content, 5.05 to 5.77 % and fibre content ranged from 9.88 to 14.43 %. The blend with 30 % cowpea substitution gave the highest value of proximate content. For the snacks produced, protein content ranged from 5.86 to 12.50 %, total ash, 2.32 to 4.32 %; fat content, 8.89 to 25.04 %; moisture content, 8.90 to 17.47 % and fibre content ranged from 7.32 to 18.76 %. It was observed that fat content was not affected by cowpea substitution. Oil–frying had a significant (p<0.05) effect on the fat contents as the fat content of the fried samples gave higher value when compared with oven-dried samples. Conversely, oven-drying had a significant (p<0.05) effect on the proximate content except on ash content. Mineral determination showed that potassium, sodium, zinc, and iron contents increased with increased in cowpea substitution in both the blends and snacks, with 30 % cowpea substitution having the highest values. Calcium content was 3.34, 3.36, 3.39 mg/kg for 10 %, 20 % and 30 % cowpea substitution respectively; while calcium was not detected in 100 % maize, the calcium content of the snacks ranged from 4.31 to 6.61 mg/kg. Functional properties evaluation showed that bulk density, water and oil absorption, foaming and emulsion capacities and stabilities all increased with increased in cowpea substitution while least gelation and swelling index decreased with increased in cowpea substitution. Bulk density ranged from 0.72 to 0.81 g/ml, swelling index, 0.66 to 1.03 ml/g, least gelation, 2.10 to 6.11 %, foaming, 7.67 to 15.36 %, water absorption, 2.41 to 3.23 %, oil absorption 1.24 to 1.45 %, emulsion capacity, 8.76 to 37.15 % and emulsion stability 7.43 to 14.13 %. Microbiological evaluation for the flour blends and snacks showed that total viable count ranged from 3.80 to 4.7 x 103 and 1.80 to 2.70 x 103 Cfu/ml respectively, while yeast and mould count ranged from 2.2 to 3.17 x 103 and 1.0 to 1.9 x 103 Sfu/ml respectively for blends and snacks. Sensory evaluation showed that there were significant differences (p<0.05) among the snacks produced in terms of aroma, appearance, texture (crispness), taste and overall acceptability. Oven-dried samples were scored lower than oil-fried in aroma, taste and overall acceptability but were preferred in terms of appearance and crispness. The overall result showed that 20 % cowpea substitution is most adequate to produce an acceptable and nutritious snack (“ipekere agbado”). However, more studies would be needed to optimise the oven-drying process as an alternative method to deep-frying. In conclusion, addition of protein-rich cowpea to traditionally and culturally acceptable snack will improve nutrient intake and livelihoods of the rural community