Studies on the microflora in suusac, a Kenyan traditional fermented camel milk product

Citation:
Lore T. Studies on the microflora in suusac, a Kenyan traditional fermented camel milk product. K. MS, J. W, eds. University of Nairobi; 2004.

Thesis Type:

MSc Thesis

Abstract:

The purpose of the study was to determine the lactic acid bacteria (LAB)and yeasts
associated with the traditional fermented camel milk product (suusac) of the Somali
community in Kenya. The traditional method of suusac production was studied by use
of questionnaire and documented. The microbial content profile and changes during
fermentation were then determined.
From 15 samples of traditionally fermented suusac, 45 LABand 30 yeast strains were
isolated ~d identified using API 50 CHL and API 20C AUXidentification systems,
respectively. The total viable microorganisms, LAB,coliforms, and yeasts and molds
were enumerated. The isolates were investigated for their functional roles in the
fermentation process, namely, acidification, flavour/aroma production and proteolytic
activity. Fermentation trials with single and mixed strain cultures were investigated to
assess their acidification and flavour-producing properties.
The traditional production of suusac involves spontaneous fermentation of camel milk
in smoked gourds at ambient temperature for 1-2 days. The milk is not subjected to
heat treatment prior to fermentation. The isolated LAB species were identified as
Lactobacillus curvatus (8% of total isolates), Lactobacillus plantarum (16%), Lactobacillus
soliuarius (8%), Lactococcus raffinolactis (4%) and Leuconostoc mesenteroides subsp.
mesenteroides (24%). The isolated yeasts were Candida krusei (20%), Geotrichum
penicillatum (12%) and Rhodotorula mucilaginosa (8%). In traditional suusac, LAB
counts averaged 6.77 logrocfu Zml, while yeast counts were relatively lower (2.05
log.ocfuZml]. Low coliform numbers were encountered « 1 log cfu /rnl].
The LAB produced considerable acidity and majority (60%) were homofermentative.
The primary functional role of the LAB was fermentation of lactose to lactic acid,
resulting in acidity levels ranging from 0.46-0.67% lactic acid equivalent. All the LAB
isolates recorded high proteolytic activity, except for L. raffinolactis, which did not
exhibit any proteolytic activity. The LAB showed varying degrees of diacetyl
production. Of the LAB, L. curvatus recorded the highest diacetyl flavour score,
corresponding to >30 mg diacetyl/ 100 ml of milk.
The yeast isolates showed limited carbohydrate-assimilating capabilities, but played a
role in flavour development and proteolysis. G. penicillatum produced diacetyl (3.1-10
mg/lOO ml), although it did not exhibit any proteolytic activity. C. krusei exhibited
some proteolytic activity, although its diacetyl-producing capacity in camel milk was
minimal (0.5-3 mg/ 100 ml).
C. krusei also played a role in mixed starter fermentation of camel milk by increasing
the activity of the LAB cultures and improving product flavour. The use of C. krusei +
1. plantarum (1: 1) and C. krusei + L. curvatus (1: 1) reduced the fermentation time by
half as compared to the use of the cultures individually.

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