A Study of the Fermentation Process and Microbiological Characteristics of Amabereamaruranu, a Kisii Fermented Milk Product

Bitutu, Nyambane R (2014) A Study of the Fermentation Process and Microbiological Characteristics of Amabereamaruranu, a Kisii Fermented Milk Product. Masters thesis, University of Nairobi.

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Amabere amaruranu is a popular traditionally fermented milk product from the Kisii community, Kenya. The objective of this study was to document the production process of amabere amaruranu, to determine and study the predominant microbial groups present and to identify and characterize the dominant lactic acid bacteria (LAB) and yeasts from samples obtained in the field as a basis for possible development of starter cultures. A survey was undertaken to study the traditional processing of the product among 27 traditional milk processors.Interviews were conducted using a structured questionnaire, key informant interviews and observation. Some key informants demonstrated the application of the indigenous technical knowledge to verify accuracy of the process documentation.A total of 16 samples of the traditionally fermented milk product were obtained from several families in Kisii for laboratory analysis. The pH of the field samples was determined, as well as enumeration and isolation of the predominant micro-organisms.The total viable microorganisms, LAB, yeasts and moulds, and Enterobacteriaceae, were enumerated. Preidentification tests for LAB was preformed according to the morphological characteristics, namely catalase test, Gram stain, growth at 15°C and 45°C, CO2 production from glucose and arginine hydrolysis. Amongst the LAB strains, 90% were phenotypically identified using API 50 CH. Yeast strains were identified using phenotypic methods and API 20C AUX.Two LABisolates and one yeast isolate that were previously isolated from samples of amabere amaruranu were tested in different combinations for their ability to ferment fresh milk. The production process of amabere amaruranuinvolved the addition of milk into a previous batch product. Fresh milk was sieved and boiled, held at boiling point for 10-15 minutes; cooled for 10-20 minutes and then inoculated into the fermentation vessel and fermented at ambient temperature ranging from 18 °C-32 °C. The product was lumpy in nature and was more preferred when it had developed appreciable acidity. Two types of fermentation vessels were used; gourd(ekerandi) and plastic containers. The average total viable counts (TVC) of the milk samples were 8.06 log10cfu/ml for ekerandiand 8.24 log10cfu/ml for the plastic containers.The average presumptive lactobacilli counts were 8.08 log10cfu/ml for ekerandiand 7.26 log10cfu/ml for the plastic containers while the presumptive lactococci were 7.85 log10cfu/ml and 7.12 log10cfu/ml for ekerandi and plastic containers, respectively. The yeasts and moulds counts averaged 4.65 log10cfu/ml for ekerandi and 6.07 log10cfu/ml for the plastic container samples. The average counts for Enterobacteriaceae were below 1.00 log10cfu/ml in ekerandi while their numbers were 2.17 log10cfu/ml in milk samples from the plastic containers. The mean pH of the 16 samples that were obtained from the field ranged from 3.65 ±0.67 to 4.7 ±0.55, with an average of 4.00 ±0.93, for all the samples. Predominant LAB species were identified asStreptococcus thermophilus (25%), Leuconostoc mesenteroides(20%)and Lactobacillus bulgaricus (15%).Predominant yeast species were identified as Saccharomyces cerevisiae(25%), Trichosporum mucoides(15%), Candida famata(10%)andCandida albicans (10%). Two LAB isolates:Streptococcus thermophilus and Leuconostoc mesenteroides, and one yeast isolate, Saccharomyces cerevisiaewere investigated in different combinations for their ability to ferment fresh milk. The starter cultures testedwere effective in fermenting the milk as indicated by a drop in the pH of the milk from 6.44 ±0.00 to a range of 4.23 ±0.21- 4.42 ±0.17 and increase in titratable acidity from 0.06 ±0.00 to a range of 0.78 % ±0.30-1.12 % ±1.00 during the fermentation period. Industrially important species such as Streptococcus thermophilus and Saccharomyces cerevisiae were isolated from the fermented milk.There is the need to identify these organisms using modern molecular methods and characterize the technological properties of the dominant types to facilitate selection and development of starter cultures from them for the production of amabere amaruranu.

Item Type: Thesis (Masters)
Subjects: S Agriculture > S Agriculture (General)
T Technology > TX Home economics
Divisions: Africana
Depositing User: NLANDU Ephraim DIKUIZA
Date Deposited: 21 Jul 2016 10:27
Last Modified: 21 Jul 2016 10:32
URI: http://thesisbank.jhia.ac.ke/id/eprint/763

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