Marahaini, Musa
(2009)
Effect of ph changes on the growth of selected
bacteria in coconut milk.
Other.
Universiti Sains Malaysia.
(Submitted)
Abstract
Coconuts (Cocos nucifera) are found growing around the world in lowland, tropical and
subtropical habitats and have been used as a valuable source not only for food but also as
medicine. One of the coconut's product used as medicine is coconut milk. Coconut milk is the
aqueous extract of the solid coconut endosperm. It is a low-acid liquid food, with a pH of around
6.2 and very rich in nutrient. These properties of coconut milk provides suitable medium for
growth of microorganisms. Effective methods of sterilization are practiced to eliminate hannful
microorganism, making coconut milk safe to be consumed. A preservation technique used in
general food preservation is by the addition of chemicals. These chemicals include acids and
bases which alter pH of food and inhibit growth of certain bacteria. In this research, we study
effect of pH changes on selective bacteria growing in coconut milk. Coconut milk samples are
subjected to different pH ranging from acidic to alkaline, started from pH 1 0, 8, 6, 4 and 2.
Control sample is prepared without addition of chemicals. Sample is inoculated on MacConkey
and MRS agar in order to identify selective bacteria growing in coconut milk. Morphology of
bacteria is examined under microscope and biochemical tests are conducted for identification of
bacteria. pH reductions are recorded throughout the experiment except for pH 2 group. Bacteria
count (CFU/ml) is recorded over time. We found that pH changes affect the growth rate of
bacteria in coconut. Klebsiella pnemoniae, Acenitobacter and Staphylococcus prefer alkaline
condition whereas Lactobacillus grows better at acidic pH. Gathered information could provide
clearer guidance towards activities which need information about bacterial growth, for example
in development of new media for growth of selected bacteria.
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