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Comparative Study Of Antibacterial Activity Of Two Selected Medicated Soap And One Local Black Soap On Staphylococcus Aureus From Wound Infection
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VISIBLE EFFECTS
Visible Growth:
When
micro-organisms can actually be observed in or on a product then there
is obviously no doubt that microbial spoilage has occurred. In fact,
this is probably the most common way in which it is manifest. In liquid
formulations contaminants may be seen as a sediment, turbidity or a
pellicle while on more solid preparations colonies, often coloured, of
bacteria, yeasts or mould may form.
Colour changes
Sometimes
visible spoilage is more striking, particularly if a colour change is
involved. Colour changes due to alternations in the components of a
product may result from pH.Redox or other changes caused by the
metabolic activities of an organism, or to pigment production by the
contaminants themselves.
Members of the Pseudomonas genus are often
implicated in spoilage of this type. These organisms metabolize a very
broad range of compounds, and can also produce soluble pigments ranging
in colours from blue-green to brown. In addition, they can render
conditions suitable for less adaptable spoilage organisms; for example
they can create conditions favouring the growth of anaerobes. Similarly,
in an acidic product, oxidative yeasts can cause a rise in pH by
utilizing organic acids and this will encourage bacterial growth.
Gas production
If
microbial metabolism produces gas in a sufficient amount to exceed its
solubility in a product, visible bubbles, frothing and other
manifestations of an increase in pressure occur. Products containing
carbohydrates or other fermentable substrates are particularly
susceptible to this type of spoilage. Of the latter, glycerol, an
essential ingredient in many cosmetic preparations, is fermented
particularly readily by some common waterborne organisms.
Other changes
Microbial
metabolism can result in the composition of a homogeneous product
becoming visibly heterogeneous. Emulsions, for instance, are notoriously
susceptible to changes in physicochemical conditions; hydrolysis of the
oil phase or changes in the pH of the aqueous phase will upset the
equilibrium and thus cause visible changes. In liquid product changes of
viscosity can be seen to occur when contaminants have broken down large
molecules, utilized sugars or caused the aggregation of particles in
suspension.
Olfactory effects
It has long been known that many
micro-organisms produce characteristics odours and as early as 1923 a
variety of aroma=producing bacteria had been listed (Omelianski, V.
C.(1923). These aromas include the highly characteristics ones of
sulphur-containing metabolites such as hydrogen sulphide, the sickly
smells of the fatty acids, the ‘fishy’ odours of the amines and the
astringency of ammonia. Often these are combined to produce the ‘off’
odours of a spoiled product. Changes in the aroma of a product due to
contaminants vary from the production of a nauseating smell to a slight
change in the bouquet but all can be disastrous, particularly to
cosmetic and toiletry preparations which depend so much upon their
specific perfumes. One of the most common olfactory warnings of spoilage
is the typical smell of mould. The responsible aromatic elements have
not been clearly identified but some actinomycetes which taint water
with undesirable earthy odours have recently been shown to produce
goesmin, a strongly earth-smelling, neutral oil (Gerber, N. N. and
Lechevalier,H . A.(1965). An alcoholic odour, produced from fermentable
substrates, is typical of spoilage by yeast.
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ABSRACT - [ Total Page(s): 1 ]Cosmetic(creams) need not be sterile,however they must not be unduly contaminated with micro-organism and should remain in a stable state throughout the shelf life of the product (or when be used by the consumer).the aim of this project was to determine the microbial load in selected creams and to identify the specific contaminants.For the determination of the number of contaminants, 1 mL of each cream was diluted to a factor of 104,1mL of this dilution was mixed with cool nutrient agar and macC ... Continue reading---
