THE hot days of the dry season is once with us again. The scorching sun with its attendant thirst calls for demand for yoghurt. Yoghurt is a thirst assuaging and energy drink. It is pasteurized milk or low-fat milk fermented and conjugated to a custard-like constituency with mixed lactic acid culture. It may be flavoured or unflavoured. It is a nutritious food with refreshing qualities suitable for consumption even by the weight-conscious.
Yoghurt production is a very good business which can be run on a small scale operating even from home with minimal capital investment. A smart investor wishing to hit jackpot this Christmas has a good opportunity to invest in yoghurt production for quick and maximum returns, or profitability on his capital investment.

Production ingredients
In the production of yoghurt such ingredients as follows must be assembled:
Milk: milk solid non fact (MSNF) is essential in production of yoghurt. It can be obtained from liquid milk, liquid skim milk, skim milk powder (SMP), wey powder, condensed skim milk. In Nigeria, skim milk powder is very popular and therefore may be recommended for this project. It must be ensured that the skim milk powder is obtained from a good source. The skim milk powder is carefully dissolved in water in the mixing vessel at a temperature of 35-40oc. It is then stored in a cool clean dry environment for production processes. The MNSF contributes to the flavour and gives a desirable texture to the yoghurt.
Stabilizer: the function of the stabilizer is to (a) absorb as much as possible free water (b) retard the growth of ice crystals during freezing and storing of the yoghurt (c) enhance the body and texture (d) improve the melt down properties. In other words, the stabilizer forms gel with the water in the formular and gives a drier product which does not melt rapidly or leak water.
Sugar: this sweetens the product and counters the fatness of the fat. It provides the solids to build up the body smoothness and mouth feel of the product. Also, it lowers the freezing point of the mixture to prevent it from freezing to solid.
Starter: these are starters of pure culture obtained from commercial laboratories in dehydrated and concentrated frozen form. Prior to the addition of a starter, the mix is first heat-treated (pasteurized) to inactivate detrimental types of contaminating organisms. Lactic acid-culture, freeze-dried for direct addition to the mix and incubated at 43oc is recommended.
Preservative: this is a chemical preservative against bacteria, yeasts and moulds, employed to improve the keeping qualities of the product.
Added flavour: this gives varieties, otherwise the product is described as plain yoghurt. Banana, strawberry and vanilla flavours are some common flavours that can be used.
Production process: there are seven production stages to be observed in the yoghurt processing.
First, weighing or measuring of ingredients: large scale production, witnesses automatic measuring or weighing of the ingredients usually under computer control. But for a small scale backyard production, measuring and weighing can be done manually by hand. Accuracy is quite necessary is measuring out ingredients such as stabilizer, flavours, culture (starters) because small errors may have quite large effects on the product.
All ingredients must be carefully measured or weighed as appropriate and assembled ready to be mixed and heat-treated.
Second mixing: there is no laid down procedure for mixing. The sequence of mixing ingredients for the yoghurt mix is not absolutely vital, but common sense will indicate a suitable method.
It will obviously be necessary to place liquid ingredients in the vat first, followed by the solid, but soluble ones next and so on.
Third, heat treatment: the heat treatment vat may be heated by gas, electricity or by steam jacket automatic and electronics controls of both the temperature at which the mix is pasteurized. Despite the extra cost over the simple hand controlled vat, this automatic control is recommended to avoid error in processing. The regulations require minimum temperatures for vat pasteurization of 63oc for 15-30 minutes or 71-72oc for not less than 10 minutes or 85oc for 30 seconds. It is strongly advisable that these temperatures should not be exceeded unduly as overheating of mixes may cause the development of heat induced flavour changes in the final product.
These are not desirable. The times and temperatures of holding as required are sufficient to render the mix free from pathogenic (harmful organisms and from most spoilage organisms). The bacteriological quality of the mixes is then dependent on the hygienic standard of all equipment which is used to handle the pasteurized mix. During the whole process of heating, the agitator of the vat must be operating to ensure adequate mixing and emulsification.
Fourth production process is the cooling and addition of starter (culture). Following the holding period the mix must then be cooled rapidly to 43oC. Many pasteurized vats are available with water cooling from the mains followed by a refrigerated cooling operation. For micro scale producers, a separate cooling tank, jacketed with inlet and outlet arrangements for cooling water may be used. It is also equipped with a stirrer. As soon as the temperature of 43oc is attained, the culture (previously weighed) is added and stirred.
Fifth process is incubation: prior to the introduction of the cooled, culture-added mix, into the incubator, the latter must have been stabilized at 43oc. Fermentation takes place with an attendant production of lactic acid producing the characteristic sour taste, custard like consistency product. The culture of yeasts acts on the milk at the specific temperature of 43oc for a period of 3-4 hours. The length of incubation is basically determined by the level of culture added, the degree of sourness and the consistency required. These will be guided by the producers goal as well as market demand.
Sixth, addition of preservation and flavour: preservation and flavour are added where flavoured yoghurt is required. Mixing is effected followed by packaging and cooling.
Seventh, refrigeration/freezing: note that cooling and packing are a matter of choice. The product may be cooled prior to packaging or vice versa. On a large scale, the mix is passed through a plate heat exchanger where it is cooled by contact through stainless steel plates with the cooling media, that is, mains, cold water followed by chilled water.