The Production and Characteristics of an Orange Fleshed Sweet Potato Yogurt

Abstract: Yogurt is an ancient food, used for a better preservation of milk. Milk gets fermented by Streptococcus thermophilicus and Lactobacillus bulgaricus (lactic acid bacteria, LAB) which converts the lactose present in the milk to lactic acid. These probiotics support the microbial population balance of the gastrointestinal tract. Sweet potato, Ipomoea batatas, is an important security crop in developing countries. The variety Orange fleshed sweet potatoes (OFSP) is gaining attention due to its β-carotene and non-pro-vitamin A carotenoid. The aim of this report is to study the fermentations of four different OFSP, containing 30-, 40-, 50- and 60 % OFSP. Then the consumer liking in Ghana was evaluated by performing a hedonic test. The yogurts, including a control yogurt containing no OFSP, were all analysed for ten days (ph, brix, viscosity and acid number). The pH was the highest for the control yogurt and as for the yogurts containing OFSP the pH got lower with an increase of the OFSP percentage. OFSP has a high concentration of starch, which can be used as a carbon source for the LAB. The Brix and acid number results supported this. The carotenoids caused a red/yellow/orange color for the OFSP yogurts. Lastly, the hedonic test showed that the 40 % OFSP was preferred among the participants from the taste, however several comments of the lack of sweetness were made. The difference in the hedonic test was small enough for a decision to be made based on the economic value of the product, as replacing milk powder with OFSP is much cheaper. Hence, the 60 % OFSP is the best option. It was concluded that the addition of OFSP contributed to the LAB activity. An interview conducted with a market researcher in Ghana showed that the product would mainly be for the population in the middle class, and to those who are health conscious. It would sell best in the bigger cities. The health benefits of this product are important, hence it needs to be accessible for everyone. With plain/sour yogurts becoming bigger in Ghana, so will crop and unsweetened yogurts eventually.