A STUDY OF THE FERMENTATION PROCESS <, AND MICROBIOLOGICAL CHARACTERISTICS OF AMABERE AMARURANU, A KISII FERMENTED MILK PRODUCT By Nyambane R. Bitutu (B.Sc. Food Science & Technology (Hons); University of Nairobi) A thesis submitted in partial fulfillment of requirements for the degree of Master of Science in Food Science and Technology of the University of Nairobi Department of Food Science, Nutrition and Technology 2014 \ ..';. 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 questionnaire, key informant interviews and observation. demonstrated the application of the indigenous accuracy of the process documentation. using a structured Some key informants technical knowledge to verify 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. LAB, yeasts and and identification tests characteristics. moulds, The total viable microorganisms, Enterobacteriaceae, for LAB was preformed according were enumerated. Pre- to the morphological 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 1 were previously different isolated combinations The production previous process cooled acidity, of amabere amaruranu involved in nature were tested 111 the addition of milk into a Fresh milk was sieved arrd boiled, held at boiling point for for 10-20 minutes and then inoculated at ambient temperature vessel and fermented was lumpy of amabere amaruranu samples for their ability to ferment fresh milk. batch product. 10-15 minutes; from ranging from 18 °C-32 "C. The product and was more preferred Two types of fermentation into the fermentation vessels when it had developed appreciable (ekerandi) and plastic were used; gourd 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 lactobacilli counts were 8.08 logrscfu/rnl plastic containers averaged container while the presumptive 4.65 loglOcfu/ml samples. loglocfu/ml The average lactococci for ekerandi counts were 7.85 log respectively. presumptive ~U1d6.07 IOC fu/rn for the I and 7.12 The yeasts and moulds loglocfu/ml for Enterobacteriaceae in ekerandi while their numbers Irom the plastic containers. The average for ekerandi and 7.26 logu.cfu/ml for ekcrandi and plastic containers, logll,cfuirnl counts for the plastic containers. for the plastic were below 1.00 were 2.17 logloc1'u/ml in milk samples 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. 2 I Predominant LAB species were identified Leuconostoc inesenteroides Predominant yeast species (20 %) as Streptococcus thermophilus (25 Lactobacillus and were identified bulgaricus as Saccharomyces (15 <)/0), %). cerevisiae (25 %), Trichosporum mucoides (15 %), Candida famara (10 %) and Candida albicans (lO Two LAB isolates: Streptococcus thertnophilus and Leuconostoc mesenteroides, and one yeast isolate, combinations effective Saccharomyces for their cerevisiae were investigated in different ability to ferment fresh mille The starter cultures tested were in fermenting the milk as indicated 6.44 :JO.OO to a range of 4.23+0.21- by a drop in the pH of the milk from 4.42 ::!:0.17 and increase from 0.06 J:O.OO to a range of 0.78 %:J:0.30-1.12 <),~) :l:1.00 in titratabJe acidity during the fermentation period. important Industrially Saccharomyces to identify development as such Streptococcus thermophilus and cerevisiae were isolated from the fermented milk. There is the need these organisms techno logical species properties molecular using modern of the dominant types methods to and characterize facilitate selection the and of starter cultures from them for the production of amabere amaruranu. 3