ISOLATION AND SELECTION OF LOCAL YEAST STRAINS FOR THE PRODUCTION OF SWEET WINE USING PINEAPPLE AND WATERMELON JUICES
ISOLATION AND SELECTION OF LOCAL YEAST STRAINS FOR THE PRODUCTION OF SWEET WINE USING PINEAPPLE AND WATERMELON JUICES
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Date
2017-12
Authors
BASSEY, Nko Samuel
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Abstract
In developing countries like Nigeria 20-30% of fruits produced are wasted due to lack of proper utilization, post-harvest and processing technology. By converting these fruit into value added products like wine is a smart solution for this problem. This study was aimed at the isolation and identification of local yeast strains from spoilt fruits and alcoholic breverages for the production of sweet wines using pineapple and watermelon fruit juices as substrates. The organisms obtained were isolated by spread plating 0.1ml solution obtained from the serial dilution of 1ml of fruit juice obtained from the smashed spoilt fruit and alcoholic breverage. The organisms obtained were characterized culturally, morphologically, biochemically and confirmed using an API Test Kit. The organisms were further screened to obtain the one with the best fermentative property by carrying out the Stress exclusion test, ethanol tolerance test, temperature tolerance test, hydrogen sulfide production test and flocculation test. The wine was then produced by cell purification by washing the yeast cell obtained and preparation of inoculum using 400ml of water and 80g of sugar and these were used for the wine production which lasted for 14 days. During the fermentation the microbiological analysis of the wine was carried out to ascertain the quality of wine produced by identifying the bacteria present in the wine and these were confirmed to be safe for consumption. Finally, sensory evaluation of the wine produced were carried out to ascertain the organoleptic property of the wine produced. A total of seven species of yeast which include Candida sphaerica, Pichia spp, Candida pelliculosa, Cryptococcus humicola, Candida guilliermondii, Candida famata and Kloeckera apiculata were isolated. Candida pelliculosa provided the best fermentative property but since it is potentially pathogenic, an alternative yeast Kloeckera apiculata was used for the fermentation. The watermelon juice used as substrate for wine fermentation had initial specific gravity of 1.07g/cm3 and the fermentation ended at specific gravity of 0.01g/cm3 while pineapple juice used as substrate
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had its specific gravity as 1.10g/cm3 and fermentation ended at specific gravity of 1.03g/cm3, the total soluble solid of watermelon juice fermentation was started at 17% and ended at 3.8% while that of pineapple juice fermentation started at 23.6% and ended at 8.2%, these showed the gradual utilization of sugar by Kloeckera apiculata in both wines produced. The total titratable acidity in pineapple juice fermentation was started at 0.01% and ended at 0.25% while titratable acidity of watermelon juice fermentation was started at 0.01% and ended at 0.5%. It was observed that titratable acidity increased daily as the days increased. Also, the alcohol content increased daily as the sugar were being utilized because the alcohol in pineapple juice fermentation was started at 0% and ended at 12.9% while the alcohol in watermelon juice fermentation was started at 0% and ended at 7.5%. The temperature decreased gradually during the period of fermentation in pineapple wine from 30-180C and in watermelon wine from 28-17 0C. The pH also decreased gradually in pineapple wine from 4.1-3.9 while in watermelon wine from 3.8-3.5. At the end of fermentation the sensory evaluation of the wine showed that the color of the standard wine was preferred to the color of the pineapple and watermelon wine produced, however in terms of taste and aroma the pineapple and watermelon wine produced were preferred to the standard wine because of the presence of glycerol produced by the organism used. Thus, through fermentation, the highly perishable fruits can be converted into a highly nutritious wine which can be made available all year round.
Description
A DISSERTATION SUBMITTED TO THE SCHOOL OF POSTGRADUATE STUDIES, AHMADU BELLO UNIVERSITY, ZARIA IN PARTIAL FULFILLMENT FOR THE AWARD OF MASTER OF SCIENCE DEGREE IN MICROBIOLOGY DEPARTMENT OF MICROBIOLOGY, FACULTY OF LIFE SCIENCES, AHMADU BELLO UNIVERSITY, ZARIA, NIGERIA
Keywords
ISOLATION,, LOCAL YEAST STRAINS,, PRODUCTION,, SWEET WINE,, PINEAPPLE,, WATERMELON JUICES,