The nutritional, physico-chemical and sensory properties of stirred yoghurt fortified with orange-fleshed sweet potato extract

Abstract

Background: Vitamin A deficiency is a major global health challenge that leads to blindness, retarded growth and death, particularly in developing countries. There is need to fortify food products like yoghurt with pro-vitamin A rich Orange-fleshed sweet potato (OFSP) to forestall this deficiency.
Objective: The aim of the study was to evaluate the effect of incorporation of OFSP extract on the nutritional, phytochemical, physico-chemical and sensory qualities of stirred yoghurt.
Methods: OFSP extract was added to yoghurt mix at 0, 5, 10, 15, and 20% levels prior to fermentation with yoghurt starter culture. The samples were designated as OFY0, OFY5, OFY10, OFY15 and OFY20 respectively. The proximate, phytochemical, physico-chemical compositions of the yoghurt samples were evaluated. Microbiological and sensory properties of the samples were also determined.
Results: The moisture content of the samples increased (p<0.05) with increase in the levels of OFSP extract. The protein content decreased (p<0.05) from 5.71% for OFY0 to 4.81% OFY20. The β-carotene level of the samples increased signicantly (p<0.05) with increase in extract content. Total flavonoid content of the samples increased (p<0.05) from 0.65mgGAE/100g to 6.20mgGAE/100g for OFY0 and OFY20 respectively. The viscosity and titratable acidity of the samples reduced (p<0.05) with increasing extract levels. Lactic acid bacteria count decreased with increase in extract level. There were no signicant (p>0.05) differences among the samples in overall acceptability except for OFY20 which had a lower score.
Conclusion: Acceptable β-carotene rich stirred yoghurt could be produced by incorporating OFSP extract up to 20% level into yoghurt mix.