Abstract

Peanuts worldwide are popular for their nutritional quality and commercial potential. Their consumption in Uganda is high and second after common beans thus making them a suitable food for fortification to fight the increasing vitamin A deficiency in the country. Consumption of orange fleshed sweet potato (OFSP) is equally high in the country and this too offers potential to fortify peanut butter for increased intake of vitamin A. The objective of this study was to investigate the potential of producing a nutritious peanut butter, with high shelf-life. An OFSP ratios of 0% (Control), 5% (Treatment 1), 10% (Treatment 2) and 15% (Treatment 3) were mixed with peanut butter. The product was assessed for proximate composition using AOAC methods and sensory qualities. The shelf-life of product was also established by determining the fat quality, beta-carotene retention and microbial quality. Fortifying peanut butter with OFSP significantly increased the protein content from 20.47 to 27.76%, fat from 30.8 to 32.4%, sugars from 2.96 to 25.51% and, beta-carotene from 244 to 1388μg 100g-1. In all treatments, the control had the lowest amount of nutrient, while OFSP that was fortified with 15% peanut butter had the highest levels of the nutrient. When OFSP was fortified with 10 and 15% peanut butter it resulted in higher retention of β-carotene between 400 to 600μg 100-1g which could meet the daily World Health Organization (WHO) recommendations of 350 to 500μg 100-1g. After storing the product for five months, OFSP that was fortified with 10 and 15% peanut butter had good fat quality as reflected by the low acid value (AV) below 0.9mg KOH-1 and peroxide value (PV) below 4mEq kg-1 respectively. There was a strong negative correlation (r=0.049; p˂0.05) between peroxide formation and the amount of β-carotene in the peanut butter. All peanut butter samples were free of dangerous levels of microbes. The peanut butter treated with OFSP had acceptable sensory score of 6-7 on the scale of 1 to 9. The results suggest that peanut butter fortified at 15% OFSP had greater shelf-life and meet the vitamin A requirements of school going children.

Keywords: Peanut butter; OFSP; β-carotene; Fat quality