Evaluation of the effect of honey sweetener on yoghurt shelf life
Muliika, Belcher Kelly
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Yoghurt is a fermented dairy product with a short shelf life of about 3 weeks or less and should be stored at low a temperature which has the implication of increasing the cost of storage hence limiting its sustainable consumption in poor communities where electricity is in short supply. The main purpose of this research was to evaluate the effect of honey sweetener on the shelf life of yoghurt. Honey Sweetened Yoghurt (HSY) was prepared together with Sucrose Sweetened Yoghurt (SSY) as experimental control. The pH, titratable acidity, Susceptibility to Syneresis (STS) and Water Holding Capacity (WHC) were measured under refrigeration and room temperature storage conditions over a period of 26 days for both yoghurt samples. The shelf lives of both honey sweetened yoghurt and sucrose sweetened yoghurt stored at room temperature were also estimated. Finally, sensory evaluation of both yoghurt samples was carried out using the 9-point hedonic scale. The pH of both SSY and HSY decreased during storage at refrigeration temperature and the decrease was significant (P<0.05) for SSY (4.84 to 4.62) compared to that of HSY (4.69 to 4.67) where the decrease was not significant. However, at room temperature storage, there was a significant decrease in pH for both yoghurt samples. There was no significant increase (P>0.05) in the titratable acidity of both yoghurt samples at refrigeration temperature but the increase was significant at room temperature with the highest value of 1.53±0.04% for SSY and 1.32±0.13% for HSY. The STS at refrigeration temperature was higher in HSY with the highest value of 67.00±2.65% but at room temperature it was higher in SSY with the highest value of 65.33±0.58%. The WHC decreased at both storage conditions but the decrease was more rapid at room temperature. The lowest WHC was 31.33±1.15% for SSY at room temperature. The shelf life of SSY at room temperature was 8 days while that of HSY under the same storage conditions was more than 11 days hence, honey had an effect of extending the shelf life of yoghurt for about 3 days under room temperature storage. On the other hand, the yoghurt samples stored at refrigeration temperature did not expire even after the 26 days of storage thus; yoghurt storage at refrigeration temperature remains advantageous and highly recommended even in cases where honey is used as a sweetener. Upon sensory evaluation, HSY had higher scores for all the sensory attributes tested compared to Sucrose Sweetened Yoghurt and the preference for HSY was also confirmed with the overall acceptability score of 7.00±0.63 for HSY and 6.73±1.62 for SSY. Therefore, in addition to extending shelf life, sweetening yoghurt with honey also enhanced its sensory attributes.