A study of the fermentation process <, and microbiological characteristics of Amabere Amaruranu, a Kisii fermented milk product
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Date
2014Author
Nyambane, Ruth Nyambane
Type
enLanguage
enMetadata
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Abstract
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 pl-l 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 APT 50 CH. Yeast strains were identified using
phenotypic methods and API 20C AUX. Two LAB isolates and one yeast isolate that
were previously isolated from samples of amabere amaruranu were tested 111
different combinations for their ability to ferment fresh milk.
The production process of amabere amaruranu involved the addition of milk into a
previous batch product. Fresh milk was sieved arrd 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 logloch.l/ml for
ekerandi and 8.24 logj.cfu/ml for the plastic containers. The average presumptive
lactobacilli counts were 8.08 logrscfu/rnl for ekerandi and 7.26 logu.cfu/ml for the
plastic containers while the presumptive lactococci were 7.85 log IOC fu/rn I and 7.12
logll,cfuirnl for ekcrandi and plastic containers, respectively. The yeasts and moulds
counts averaged 4.65 loglOcfu/ml for ekerandi ~U1d6.07 loglocfu/ml for the plastic
container samples. The average counts for Enterobacteriaceae were below 1.00
loglocfu/ml in ekerandi while their numbers were 2.17 logloc1'u/ml in milk samples
Irom the plastic containers. The mean pl-I of the 16 samples that were obtained from
the field ranged from 3.65 ±(),67 to 4.7 ±0.55, with an average of 4.()O ±O.93, for all
the samples.
Predominant LAB species were identified as Streptococcus thermophilus (25 <)/0),
Leuconostoc inesenteroides (20 %) and Lactobacillus bulgaricus (15 %).
Predominant yeast species were identified as Saccharomyces cerevisiae (25 %),
Trichosporum mucoides (15 %), Candida famara (10 %) and Candida albicans (lO
Two LAB isolates: Streptococcus thertnophilus and Leuconostoc mesenteroides, and
one yeast isolate, Saccharomyces cerevisiae were investigated in different
combinations for their ability to ferment fresh mille The starter cultures tested were
effective in fermenting the milk as indicated by a drop in the pH of the milk from
6.44 :JO.OO to a range of 4.23+0.21- 4.42 ::!:0.17 and increase in titratabJe acidity
from 0.06 J:O.OO to a range of 0.78 %:J:0.30-1.12 <),~) :l: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
techno logical properties of the dominant types to facilitate selection and
development of starter cultures from them for the production of amabere amaruranu.
Citation
M.Sc (Food Science & Technology) ThesisSponsorhip
University of NairobiDescription
MSc thesis