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close this bookStrategies for market orientation of small scale milk producers and their organisations. Proceedings of a worshop held at Mogororo Hotel, Mogororo, Tanzania, 20-24 March 1995. (1995)
close this folderSession 4: Milk processing requirements
close this folderMilk processing requirements for satisfying the demand for various dairy products in Tanzania
View the document(introduction...)
View the documentIntroduction
View the documentMilk quality and Marketing
View the documentFermented milk
View the documentButter
View the documentGhee
View the documentMilk/Blood mixture
View the documentOrganisational set-up and training
View the documentConclusions
View the documentReferences

Butter

Traditionally, butter is made from sour milk using a gourd or earthnware jar (O'Mahony and Bekele, 1985; Kurwijila, 1988). Sour milk is normally churned by shaking the vessel until the butter separates out. Among the Maasai, the vessel with sour milk is hung on a tripod and women or children swing the vessel to and from until the butter separates. Churning is normally done in the morning or late evening when the temperatures are normally low (Kurwijila, 1988b).

Butter is normally over-churned and not washed, factors which favour a high moisture content in the butter with a consequent short shelf life. Since the smallholder farmers do not have refrigerators, butter is prone to deterioration (O'Mahony 1987). Many people in the rural areas do not use butter as a spread on bread or for baking. Most of the butter is converted to ghee (personal experience). Butter is normally not salted and is kept in small gourds or earthware jars.

During processing there are many losses which are unavoidable. Webb (1983) reported that wastages should not exceed 5 and 3% of total butterfat when butter is made from sour milk and cream, respectively.

Improvements which can be done are to shorten the churning time and increase butter yield or butter fat recovery. Time can be reduced by gathering cream from the top of the vessel after souring and thus churn only the concentrated creamy portion of the sour milk. Yields will be high since the churning will take shorter time and temperature rise which tend to melt the fat, leading to high fat loss in the butter milk, is minimised (O'Mahony, 1987). Churning efficiency can also be improved by using an agitator developed at ILCA (O'Mahony and Bekele, 1985; Mbaga et al 1990), provided the churning temperature is held below 16°C. For larger volumes of cream more than 300 litres especialy in co-operative farms band driven centrifugal separation of cream followed by agitators like the wooden churn and ILCA agitator figure 1 are more appropriate to churn cream with 35-40 BF of proper temperature < 16°C producing butter and 0.1 % BF buttermilk. Fermenting the cream 2-3 days to develop the serum acidity to 0.5 %, fat solidifies, becomes viscous and influence speed and effectivenes churning and aromatic flavour develops due to diacetyl, propionic and acetic acid during fermentation (O'Mahony and Peters, 1987). The process enables the efficient recovery of milk fat as butler of about 96) % of the total fat processed. Churning temperature can be reduced by evaporative cooling (Dule, 1991).

Cream separation offers more processing options than are available with sour milk. Therefore a hand cream separator can be used to separate whole milk into skimmed milk and cream. Churning cream to butter takes a very short time and gives high butter yield.

Mwakapala (1990) did compare churning efficiency and fat recovery by using traditional bottle gourd, ILCA's clay pot churn (O'Mahony and Bekele, 1985; Mbaga, et al 1990), a wooden butter churn and an electric butter churn as a control to churn sour whole milk and uncooled sour whole milk. He obtained the results shown in Table 7.

Table 7: Average churning time, fat recovery and fat content in buttermilk from different types of butterchurns (Mwakapala, 1990).

Type of churn

Cooled sour whole milk (in %)

Uncooled sour whole milk

Churning time (min)

%Fat in butter milk

%Fat recovery

Churning time (mill)

% fat in butter milk

% fat recovery

Traditional gourd

93

0.83

78.3

60

1.18

69.6

ILCA-clay pot

73.8

0.3

92.8

38.8

0.38

90.2

Wooden butterchurn¹

65.3

0.3

92.9

35

0.5

87.2

Electric (control)

705

0.15

96.2

35

0.35

91.0

1Mbaga et al, 1990

Adoption of ILCA' clay pot churn with an internal agitator and a wooden churn could be best and most appropriate option for traditional small scale butter making provided at that the quantity of the milk to be processed is reasonably high (at least 50 - 100 litres/day). Also churning sour whole milk at low temperature resulted in increased fat recovery. Cooling to 3 - 4°C below ambient dry bulb temperature can be achieved by evaporative cooling in charcoal lined metal cabinets (Fig. 2) (O'Connor, ILCA, personal communication).

Salting butter with 2% salt increases its shelf life and yield. Salted butter should contain 80% milk fat, 2% milk solids-not-fat and 15% moisture.

Buttermilk as a by-product of traditional butter making is usually consumed without further processing i.e. consumed in a similar way to fermented milk (Shallo and Hansen, 1973; Bekele and Kassaye, 1987). Processing larger volumes of milk into butter and skim milk gives the processor more efficient recovery of butterfat and provides more options for the disposal of separated milk, but also requires more equipment (O'Mahony, 1987).