Agriculture Reference
In-Depth Information
clean and the increased risk of depositing an insoluble
calcium silicate scale.
many products to use. In meat plants, the biggest single
volume of detergent used is normally an alkaline foam
cleaner of some sort, with non-foaming crate wash deter-
gent, manual neutral detergents and acidic foam descal-
ers also finding use. Depending on the degree of further
processing, other specialist products may be needed. As a
rule, when choosing products for particular applications,
the mildest, safest, least corrosive options should be tried
first, with the 'heavier guns' being brought in as needed.
Detergent formulations may vary substantially in their
effectiveness; failure to perform is usually not a question
of a 'poor' product (though active ingredient levels can
be inadequate in some cases) but rather of the choice of
the wrong product, applied and controlled in an inap-
propriate fashion.
While a 'detergent' is designed to remove soils, another
term - 'sanitiser' - is often used for some products of a
similar type. In Europe, the term 'sanitiser' is taken to
mean a combined detergent-disinfectant, while 'disin-
fectant' means a product designed to kill microbes but
without deliberately employing a soil-removal effect.
Enzymolysis
Protease, lipase or amylase enzymes may
find use in specialist detergents where they can be quite
effective at mild pH conditions. They split the large
organic molecules with the same objective as alkaline or
acid hydrolysis though enzymes can be more thorough in
their effect. They are generally more difficult to formulate
in a stable product.
Detergents: Design and choice
It can be seen, from the physical and chemical tasks
needed for detergents to remove deposits, that the design
of a detergent may be quite complex. In general, the
more complex and varied the soil, the more different
components need to be employed in the detergent. Other
critical variables are the water hardness, the temperature
and method of application, the safety considerations for
operators and plant surfaces and the possible effects on
the effluent system. To meet these varying requirements,
the detergent manufacturers will have a range of differ-
ent formulations. The main components, which may or
may not be jointly present, include:
•
Alkalis: caustic soda, caustic potash, carbonate, sili-
cate and phosphate
•
Acids: phosphoric, nitric, citric, glycolic, sulphamic
and hydrochloric
•
Chelating agents: EDTA, gluconate, glucoheptonate,
citrate and polymers
•
Solvents: isopropanol, propylene glycol, butyl diglycol
and ethers
•
Surfactants: anionic, cationic, non-ionic and ampho-
teric (many different types exist)
•
Corrosion inhibitors: organic and inorganic
•
Enzymes: protease, lipase and amylase
•
Oxidising agents: hypochlorite, isocyanurates and
peracids
•
Stabilisers
•
Viscosity modifiers
Any one detergent formulation may contain as little as 2
or even >15 individual components, blended carefully to
the application and all its variables. Perfumes, such as
pine, should not be incorporated in food plant cleaning
chemicals as they can severely taint meat, even without
direct physical contact.
In order to cover all the needs of the food and beverage
industry, a detergent manufacturer's product range may
comprise several hundred different formulations, but for
any one plant, the choice is usually narrowed down to
2-10 products. The skill of the user, in conjunction with
the hygiene chemical supplier, is in choosing which of the
Principles of disinfection
Soil deposits in a food plant would be bad enough if the
problem was simply their rather unsightly appearance.
However, the fact that they harbour, nourish and protect
spoilage or pathogenic micro-organisms that are invisi-
ble to the naked eye makes the job somewhat harder. The
soil must of course be removed as completely as possible
by effective cleaning using the detergents discussed ear-
lier. Typically, the reduction in the total viable bacterial
count achieved by cleaning is of the order of 3-4 logs/
cm
2
. If the initial loading was 10
6
CFU/cm
2
, which is fre-
quently the case and higher in meat processing, there
will remain counts of 10
2
-10
3
/cm
2
after cleaning. It is
then necessary to reduce the bacterial numbers further,
by the process of
disinfection
, to levels of less than a few
hundreds. Complete
sterilisation
, the elimination of all
life, is neither practical nor necessary in the disinfection
of food plant surfaces. The reduction of microbes
between the cleaning steps and the disinfection steps is
variable, affected by the plant surfaces, soil type/level,
cleaning programme and of course the chosen measure-
ment of cleaning success. For instance, a study of clean-
ing techniques on the removal of biofilms described
lower orders of effect during both the cleaning and dis-
infectant stages (Gibson
et al
., 1999).
Biocidal active components
The class of hygiene chemicals known as
disinfectants
shares some components with detergents, but other
aspects of the formulations are very different. Their
