Efficiency of millet-derived versus commercial yoghurt cultures in lactose elimination

Abstract

Lactase deficiency is present in up to 15 % of persons of northern European descent, up to 80 % of blacks and Latinos, and up to 100 % of American Indians and Asians. About 78% of Africans have lactose Intolerance and 58% in Ugandans. Probiotic yogurt, comprised of a Fiti sachet containing Lactobacillus rhamnosus GR-1 and Streptococcus thermophilus C106, has been used in the developing world, notably Africa, to alleviate malnutrition and disease. In sub-Saharan African countries, fermentation of cereals such as millet, is culturally significant. The aim of this study was to investigate milk fermentation capability of fermented finger millet extract when compared to commercially available yoghurt starter cultures. The objectives were: (i) to determine the time taken by the different yoghurt cultures to attain a pH of 4.5; (ii) to compare the efficiency of lactose fermentation of the locally made-culture and the commercial yoghurt cultures and (iii) to determine the shelf-life of yoghurt made by the different yoghurt cultures. The local culture was prepared by sprouting finger millet, and then fermenting it together with millet flour for 18 hours. The yoghurt samples were then made from the cultures. These yoghurt samples were the evaluated for shelf life tests, organoleptic tests, and time taken for the attainment of a pH 4.5 in each of the yoghurt samples made from the different cultures for 21 days. Lactose content evaluation was carried out after a period of 24 hours for three days, using Benedict’s test. Lactose reduced in all fermented products. After three days of observation, lactose content in yogurt made from fermented finger millet extract reduced to 1.4g/20mls compared to <0.5g/20mls in Danisco Yo-Mix and Hansen Yoflex commercial yoghurt starter cultures. Yoghurt from Hansen took 2 hours. to attain pH 4.5 Yoghurt produced from commercial starter cultures had the longest shelf life of up to three days compared to that from the fermented finger millet extract that lasted for only two days. In conclusion, fermented millet extract is capable of producing novel, tasty yoghurt, with a considerable amount of lactic acid produced from milk fermentation. However low pH seems to be the main limiting factor for microbial growth, as fermentable sugars were still detected at the end of the fermentation. Yoghurt shelf life was sustained during 15 days of refrigerated storage and five days of room temperature storage, for Hansen and Danisco. This is easily reproducible in community kitchens. The sensory evaluation showed a preference for yogurt made from Hansen and Danisco.