DETERMINING THE POTENTIALS OF LACTIC ACID BACTERIA ISOLATED FROM „NONO‟ FOR USE AS STARTER CULTURES IN YOGHURT PRODUCTION
DETERMINING THE POTENTIALS OF LACTIC ACID BACTERIA ISOLATED FROM „NONO‟ FOR USE AS STARTER CULTURES IN YOGHURT PRODUCTION
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Date
2016-04
Authors
DUNGUS, FALMATA BASHIR MAINA
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Abstract
This study was aimed at isolating, characterizing and optimizing lactic acid bacteria from „nono‟ for use as starter culture in yoghurt production. The Lactic acid bacteria were grown on de Mann Rogosa and Sharpe medium agar (MRS agar, Oxoid) and β-disodium glycerophosphate agar (M17 agar, Oxoid). After several presumptive tests which included microscopy and conventional biochemical tests, the isolates were further characterized base on their different sugar fermentation profiles using Analytical profile index (API KIT, Biomereux, France). Six different strains were obtained and identified as Lactococcus lactis sub specie lactis, Streptococcus thermophilus, Pediococcus pentasaceus, Lactobacillus fermentum, Lactobacillus brevis, and Lactobacillus pentosus. These lactic acid bacteria were further subjected to tests for exopolysaccharide (EPS) production where Streptococcus thermophilus and Lactococcus lactis were discovered to be EPS producing strains which is a desirable quality in yoghurt production. The co-culture of these two strains was then termed the “local starter culture” and the specific growth rates, doubling times and acidification rates in cow, soy and goat milk fermentations were determined. Comparatively, findings from this study showed no variation (p ≥ 0.05) in the acidification rates of the local starter culture with that of foreign starter cultures which further affirmed the potentials of the local starter culture in yoghurt production. The yoghurt samples produced with the local starter cultures were compared with their counterparts produced from foreign commercial starter culture and compared base on their physicochemical, proximate, microbiological, viscosity, sensory properties and shelf-life. Profile of the physicochemical analysis of the yoghurts produced with the local starter culture showed decrease in pH from 5.74 to 4.27 while titratable acidity increased from 0.38% to 1.32%
after 6 hours of fermentation with no significant difference (p≥ 0.05). Similarly, the local starter culture impacted no significant variation (p≥ 0.05) in the proximate composition of the yoghurt samples with moisture contents of 86.01% and total solids of 15.02%. Results from this study showed no significant difference (p≥ 0.05) in the general acceptability of all the yoghurt samples. The shelf-life study depicts the importance of keeping yoghurts at low temperature irrespective of the type of milk or starter culture used in order to slow down spoilage. Findings from this study demonstrate the potentials of local starter cultures to perform equally good like the exotic strains in yoghurt production
Description
A THESIS SUBMITTED TO THE SCHOOL OF POSTGRADUATE STUDIES AHMADU BELLO UNIVERSITY, ZARIA IN PARTIAL FULFILLMENT OF THE REQUIREMENTS FOR THE AWARD OF MASTER DEGREE (M.Sc.) IN MICROBIOLOGY
DEPARTMENT OF MICROBIOLOGY,
FACULTY OF SCIENCE,
AHMADU BELLO UNIVERSITY,
ZARIA, NIGERIA
Keywords
DETERMINING,, POTENTIALS,, LACTIC ACID BACTERIA ISOLATED,, „NONO‟,, USE,, STARTER CULTURES,, YOGHURT PRODUCTION