QUALITY AND MICRIOBIOLOGICAL EVALUATION OF AFRICAN YAM BEAN YOGHURT SUPPLEMENTED WITH COW MILK

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August – September 2014, vol 4, no. 1
pages: 70-74
Article type: Microbiology of Microbiology
DOI: 10.15414/jmbfs.2014.4.1.70-74
Abstract: The utilization of African yam bean for the production of yoghurt substituted with cow milk was studied. African yam bean milk was extracted from dehulled seed, pasteurized and fermented with Yoghurmet® in ratios with reconstituted cow milk powder in the ratios 50:50, 70:30, 90:10, 100:0 and 0:100 (African yam bean milk:Cow milk). Sample 0:100 which was 100% cow milk yoghurt served as the control. The samples were stored for 14 days at 4oC and 3 days at room temperature. The results of the proximate composition of the fresh samples in percentages are; Moisture: 82.76, 81.62, 83.62, 86.53 and 85.42. Total solids: 17.25, 18.47, 16.35, 13.47and14.57. Protein: 5.93, 4.27, 5.87, 5.57 and 5.14. Ash: 0.94, 0.83, 0.91, 0.90 and 0.87. Fat: 1.07, 2.53, 1.18, 1.45 and 1.75. Carbohydrate: 9.09, 10.73, 8.33, 5.53 and 6.78 for the samples 100:0, 0:100, 90:10, 70:30 and 50:50 respectively. The moisture, total solids, fat and carbohydrate contents differed significantly (p≤0.05) in all the samples. The protein content of 100:0 and 90:0 did not differ significantly but differs in other samples. 0:100 differ significantly from other samples in ash content. There was no fiber in the samples. The total viable microbial count was highest in 70:30 (1×107cfu/ml) for refrigerated storage samples while 50:50 (9.5×106cfu/ml) had the highest count in room temperature storage samples. There were no yeasts/moulds enumerated in the refrigerated storage samples while yeast/moulds appeared in 100:0 (3×106cfu/ml) and 70:30 (1×106cfu/ml) on the 3rd day of room temperature storage. The titratable acidity of all the samples increased gradually throughout the storage period while their pH decreased. The specific gravity of the samples also decreased gradually throughout the storage period. The anti-nutritional composition of the samples containing African yam bean was also determined. The sensory properties showed that samples stored at refrigeration temperature maintained good quality up to 14 days of storage and that sample 50:50 was most preferred.
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