Water supply for food processing
Practical Action
Suspended soils can be removed by
allowing them to settle out in settling
tanks, see Figure 1 and/or filtering the
water through specially designed water
filters, see Figure 2. Both processes are
relatively slow and large storage tanks are
necessary if water is needed for washing or
incorporation into the product. Water
for cooling can be re-circulated. Although
some types of water filters also remove
micro-organisms, the easiest way of
destroying them is to add chlorine solution
(5-8ppm final concentration of chlorine
obtained by diluting bleach to
0.02-0.04%). Lower chlorine levels (eg
0.5ppm) are needed if the water is to be
Figure 2: Small-scale sand filter
used in a product to prevent 'off' flavours.
Chlorination of water supplies can be
simply arranged by allowing bleach to drip, at a fixed rate, into storage tanks or pipelines. The
rate of bleach addition is found by experiment, using simple chlorine paper or more
sophisticated probes to check the chlorine concentration. A less suitable alternative is to boil
water to sterilise it. Water should be heated to boiling and then boiled vigorously for at least 10
minutes. This of course has a high fuel requirement and will therefore increase processing
costs.
Processing equipment
The frequency and type of cleaning depends very much on the type of food being processed.
Equipment for dry foods and powder does not require more than a simple brushing down each
day whereas equipment that processes meat, milk and some vegetable products may need
careful cleaning with both detergents and sterilants every few hours (because these foods can
support the growth of potentially dangerous bacteria whereas dry foods cannot).
The type of cleaning depends on the nature of the soils on the equipment. In general, any
equipment in which foods are deposited on the surfaces and then heated will be heavily soiled
and difficult to clean. Table 1 shows examples of soils which are easy or hard to remove.
Soil
Solubility in water
Ease of removal
Typical foods
Sugar
Fat
Protein
Mineral
Salts
Soluble
Insoluble
Insoluble
Variable
Most soluble in acids
Starch
Soluble if not heated
Table 1: Soil removal
Easy
Difficult
Very difficult
Easy to difficult
Depending on
solubility
Easy to difficult
depending on heating
Preserves, fruit juices
Meat, dairy products
Meat, dairy products
Milk
Vegetables
2