Many dairy farmers lose their produce soon after milking. The post-harvest loss leads to reduced revenue as one cannot sell the spoilt milk.
Spoilage is the deterioration in texture, colour, odour or flavour of milk to the point that it is unappetising or unsuitable for human consumption.
Spoilage is mainly due to acidity, adulteration, presence of antibiotics and aflatoxin. The acidity leads to breakdown of lactose to lactic acid resulting into milk souring. Natural acidity of milk is between 0.16 per cent and 0.18 per cent.
The sources of microbes that lead to milk spoilage are many.
First is dirty udder, cow dung, dirty milking facility and improperly cleaned equipment (milk cans and bulking tanks). Second, improper cooling and refrigeration of raw milk during storage and transport.
Third is addition of water or solids to increase milk volume, density and fat content.
Fourth, antibiotics used to treat cows. If the animals are milked before the end of the withdrawal period, then the milk might get spoilt.
Fifth, aflatoxins, which find their way into milk after cows feed on fodder that has developed moulds.
CURBING MILK SPOILAGE
The most basic thing to do is keep animals clean and healthy. Milking personnel should maintain high standards of hygiene by washing hands with soap and clean warm water, wearing clean clothes and upholding general body hygiene.
The cow’s udder should also be washed with warm water and dried with a clean towel before milking.
The milking parlour should be frequently cleaned to remove slurry. Milking and milk storage containers must be made of food-grade materials, preferably aluminium and animal feeds should kept under dry conditions.
Store and transport milk under low temperatures, about 4 degres Celcius. Processing techniques that transform milk into dairy products like mursik, mala and suusa can be used to improve milk shelf-life reducing spoilage.
MAJOR QUALITY TESTS
Most farmers take their milk at collection centres before it is picked by processors. There are basic tests that must be done at these centres to guarantee quality and avoid spoilage.
These include the alcohol test done using an alcohol gun and lactometer test done using a lactometer. The alcohol test analyses milk quality on the basis of stability of milk protein. This is related to acidity in milk as a result of clinical or sub-clinical mastitis infection of the animal’s udder.
The lactometer test is used to check if milk has been adulterated. It is based on the fact that the density of milk ranges from 1.026 to 1.032g per millilitre. Adding water in milk lowers its density, while addition of solids increases the density.
MILK PRODUCTION AND HANDLING
Farmers need to update regularly their milk handling skills. This can be done at agricultural institutions and during field days organised by dairy sector professionals, or during agricultural shows.
The Ministry of Agriculture, Livestock and Fisheries, through livestock extension officers and the Kenya Dairy Board, also train farmers and collection centres’ workers on milk production and handling.
Kashongwe Olivier, Nato Samwel and Ndungi Faith work at the Animal Science Department, Egerton University