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.

Popular Abstract

The yogurt market in Ghana is so dominated by sugary, fruit yogurts, with familiar flavors such as vanilla and strawberry. But how would a healthy, unsweetened sweet potato yogurt fit in?
What would the customer choose: A familiar, sugary fruity yogurt or a new, neutral/almost sour crop yogurt filled with great health benefits? When a new product gets introduced to the market where there is a similar product in the same category, which exists in every corner store and at a cheap price, there can be some challenges. This new product I am talking about is a fermented yogurt with an addition of orange fleshed sweet potatoes, with absolutely no sugar!

The importance of consumption for orange fleshed sweet potatoes has had a raised awareness recently, due to their high content of β-carotene which converts to Vitamin A when consumed (one of many great health benefits!). It would be great to consume this as an easy, to-go product! The addition of sweet potato in yogurt resulted in an increase of formed lactic acid. Yogurt is already a product of good health benefits because of its probiotics, which supply our bodies with good bacteria. Interestingly, the high content of starch in sweet potato became a great carbon source for the lactic acid bacteria, Streptococcus thermophilus and Lactobacillus bulgaricus. The bacteria got more substrate to convert into lactic acid, which resulted in a lower pH as more sweet potato was added.

This work could contribute to a shift in the yogurt market in Ghana, which would reduce the intake of sugar and add sweet potato to the consumers daily or weekly diet. Vitamin A deficiency is common in developing countries. This can lead to a special type of blindness when the deficiency is severe, by adding sweet potato to one's diet it may help prevent the condition. The deficiency is quite common in Ghana, especially amongst children, so it is important to start today! The sensory evaluation performed in this project showed that most Ghanaians wanted sugar added to it, since it was too sour. The product might not have a smooth and fast journey into the Ghanaian market, another reason why we should start today! This is most likely because of the perception that a yogurt is supposed to have a sweet taste. The local farmers would also obtain great benefits from this shift as the farming is highly efficient and profitable, it’s a win-win!
Surprisingly, the sensory evaluation showed participants coming from Europe found the sweet potato yogurt good, despite the sourness. This is due to a familiarity from their home countries. Hey! This means the sensory results could be completely different somewhere else.. It would be interesting to see how different nationalities enjoy this product.
In this study four different sweet potatoes were produced, 30-, 40-, 50- and 60 % sweet potato in the yogurts, alongside one containing no sweet potato. The best product was determinded to be the most accessible one, which is the cheapest and contains the sweetest potato. Throughout a storage of 10 days in a refrigerator different physical and chemical analyses were performed to see the bacterias activity.

• author: Kunfu, Ariam
• supervisor: Björn Bergenståhl; Faustina Okyere; Ruth Prempeh
• organization: Food Technology and Nutrition (M.Sc.)
• course: KLGM10 20221
• year: 2023
• type: H2 - Master's Degree (Two Years)
• subject: Agriculture and Food Sciences
• keywords: Sweet potato, fermentation, Ghana, yogurt, L. bulgaricus, S. thermophilus, food technology and nutrition
• language: English
• id: 9110932
• date added to LUP: 2023-02-16 11:20:56
• date last changed: 2023-02-16 11:20:56