Development of a functional beverage from the Kei apple fruit Dovyalis caffra / M-J. Gore

• Main Author: Gore, Mary Jane Cook
• Published: North-West University 2009
• Subjects: Kei apple (Dovyalis caffra); Functional beverage; Polyphenols; Product development; Consumer sensory testing
• Online Access: http://hdl.handle.net/10394/1198

Interest has grown over the last two decades in the health benefits of polyphenols, with particular relation to degenerative diseases. The Kei apple (Dovyalis caffra) is an indigenous plant to South Africa, thought to be rich in polyphenols. This study aimed to produce a functional beverage from the Kei apple, with demonstrable nutritional benefits, which should also be found acceptable by consumers due to its sensory attributes. A long term aim of the study is to assist in improving income of farmers in rural and urban areas by encouraging the participation of small holders in growing the Kei apple for subsequent economic benefit. A thorough literature review was conducted on functional foods, trends for beverages, legislation and on polyphenols as a class of functional ingredients, specifically focusing on fruits and the fate of polyphenols in the body. A review of fruit processing procedures, preservation techniques and legislation, followed by new product development (NPD) and the types of consumers desiring functional foods were investigated as well as the role of sensory evaluation and consumer research were examined. Methods Kei apples were collected from two areas of South Africa, namely Bloemhof in the North West Province in the 200212003 growing season and from the Eastern and Western Cape in the 200412005 growing season. The first set of Kei apples were used to produce a prototype functional beverage, from which future development would take place. The second set of Kei apples were used for pulping on an industrial scale and then a small-scale commercial production batch of the Kei apple beverages for consumer panel testing was produced. Various flavours were used to mask the strong characteristic taste and aroma of the Kei apple for the beverage and these were narrowed down to apple, vanilla and mint 8. vanilla. Consumer panel testing was undertaken with 152 consumers with a pre-tested questionnaire using hedonic scales for overall acceptance, ranking for preference, a Fwd Action Rating Scale (FACT) for consumption intent, and a ranking test for purchase intent. All evaluations were carried out under strictly controlled sensory evaluation requirement and respondents were asked to fill in anonymous questionnaires at North West University, Potchefstroom Campus. Results and Discussion Statistical analysis of the results were determined by the Statistic* programme, version 7. In summary for all of the consumer testing, it was found that consumers regarded the apple flavoured Kei apple beverage statistically significantly more acceptable than the other flavours. The apple flavoured beverage was found to be rated practically significantly higher for the attributes of taste and overall acceptance, as well as for consumption intent, purchase intent and preference. There was, however, no significant differences in any of the attributes or evaluated consumption and purchase intent between the vanilla and mint & vanilla. The total polyphenols, determined by UV spectrophotometry as gallic acid equivalents per litre (GAE/I), were found to be slightly less then expected, with the apple and mint & vanilla showing similar results (as GAEII) 101.7 versus 106.1 for the latter two, whilst vanilla was 143.0 which may have been attributed to the vanillic acid molecule itself which also has a phenolic structure. This lower-than-expected level of total polyphenols may have been due to degradation during processing. There was a clear difference in the polyphenol content between the different harvests from the two regions. The former showed greater acidity as determined by total citric acid 4.81% w/w and sugar 16.3% versus 2.54% w/w and 8.4% This may be due to various factors of climate, soil and ripeness. For comparison purposes, a commercial product from the USA, Ocean Spray ® Cranberry, was also found to have more polyphenols present than the Kei apple beverage. This was also demonstrated by the amount of ascorbic acid, free and bound. The Kei apple beverage subjected to pasteurization probably lost most of its vitamin C content due to the heat treatment and the exposure to oxygen during pulping. Conclusion and Recommendations The development of a functional beverage from the Kei apple is feasible. As with most new product developments, further formulation modifications which are not insurmountable are required. The consumer panel was positive towards the apple flavoured beverage and this flavour should be taken forward for future development. The key stumbling block to the success of this project is the lack of an effective organizing body that could liaise with the growers to form a cooperative and provide a consistent supply of Kei apples. The effect of variations in harvesting time, soil conditions and climate must also be evaluated. The improvement of income of farmers may only be achieved by the involvement of other stake holders and the formation of a Kei apple grower's co-operative === Thesis (M.Sc. (Nutrition))--North-West University, Potchefstroom Campus, 2006.