Agromisa 
Interdev Agroalimentaire  

Yoghurt making on household level

	Type de fiche	Techniques/Technologies
	Mise en œuvre	Agromisa(Pays Bas)
	
	Zone géographique	; 
	Mots clés	YAOURT

	Echelle d’action	Famille/Exploitation familiale
	Public(s) cible(s)	Individual dairy producers owning one or two heads of cows or a few goats or sheep

Problématique / Objectifs
Pasteurizing the milk before adding the culture bacteria
Availability of yoghurt bacteria
Possibility to keep the volume of milk to be processed at a constant temperature of 45 C.
Possibility to cool the end product and keep it cool (below 10 C)
Description/Mise en oeuvre
Yoghurt is produced when milk is soured by certain bacteria. The milk should be heated to 85 OC to make sure useful bacteria grow and harmful, unwanted bacteria in the milk are killed. After the milk has been soured, the yoghurt bacteria are still viable. That is why a little of the old yoghurt can be used to make fresh yoghurt by adding it to fresh milk.Basic recipe for yoghurt.You will need: raw milk, a heat source, a saucepan, cooling facility ( e.g. a large pan with cold water), a wooden spoon (boiled), thermometer, yoghurt culture, starter for yoghurt or some fresh yoghurt, thermos flask or haybox, a cool place (refrigerator or cellar).Stir the milk, heat it to 85 oC or its boiling point and keep it at this temperature for 3 minutes. Cool the milk as quickly as possible to 45 oC (e.g. in a second saucepan with cold water). Add 50 ml. (3 tablespoons) of yoghurt to each litre of milk; the yoghurt should not be more than one day old. Instead of yoghurt you can use a yoghurt culture. Stir the milk thoroughly and leave it to sour. The time required for the milk to sour depends on the temperature. To give you an idea:-	at 40 - 45oC it takes 3 to 6 hours-	at 35 - 37 oC it takes 15 to 20 hours-	at 30 oC it takes about 24 hoursThe ideal temperature to make pleasant tasting yoghurt is 45 oC.It is not possible to produce yoghurt at temperatures below 30 oC or above 50 oC. Yoghurt is ready for consumption once the incubation period is finished. If cooled, yoghurt can be kept for one week.Yoghurt made from milk-powder.Make milk from milk-powder according to the instructions, but add 10 to 15% extra milk-powder. Dissolve the milk-powder in boiling water and let it cool off to 45 oC. Stir in 3 tablespoons of fresh yoghurt or a yoghurt culture per litre of milk. Cover the saucepan and put it in a warm, insulated place (e.g. a haybox). After 3 - 6 hours the yoghurt should be ready for consumption.Remarks.-	It is best to use fresh milk to make yoghurt. Milk-powder can also be used. Sterilized milk gives a thinner yoghurt than pasteurized milk.-	After incubation, cooling is desirable, preferably below 10 oC, so that souring is stopped (the taste remains good) and the bacteria remain more viable, while the yoghurt can be used to inoculate milk again. If it is not possible to cool below 10 oC, some yoghurt should be added to fresh milk immediately after yoghurt making (when it is still sour enough). Otherwise the bacteria will die because the yoghurt becomes too sour. -	Make sure the milk sours as quickly as possible, preferably at 40 - 50 oC rather than 30 oC. Harmful bacteria have less opportunity to develop if the incubation period is shorter.-	A thicker yoghurt can be produced by adding 2 to 3 tablespoons of milk-powder to each litre of milk before heating it to 85 oC.-	It is not advisable to use fruit yoghurt from a shop as a culture because it contains a lot of additives. Plain yoghurt from a shop can be used if it is not too old. Sterilized yoghurt is not suitable either because the bacteria have been killed.-	When using yoghurt from a carton or a pot as a starter, first remove the top layer and take the yoghurt from the centre to make fresh yoghurt. This is because the bacteria in the middle are probably the most diverse and active.-	Stir as little as possible to avoid any extra risk of incorporating undesirable bacteria.-	At household level, yoghurt making in a thermos flask can be a good method.Heat the milk to 85 oC, then cool it to 45 oC. Pour 90% of the milk into a thermos flask which has been rinsed with hot water. Mix a tablespoon of yoghurt made the day before or a yoghurt culture with the rest of the milk and add this to the thermos flask. Close the flask well, shake it and leave to stand for 3 - 6 hours. Remove the yoghurt from the thermos flask and store in a cool place. Yoghurt made of sheep's milk is very thick and not suitable to be made in a thermos flask-Utensils should be easy to clean, and if available made of stainless steel. For pasteurising a double-wall combination vessel is recommended, where boiling water or cold water can stream into the double wall. Furthermore a thermometer, and a stirring utensil (spoon) are required. 

Auteur : Rob Witte
Saisie le : 19/11/2001 

		Pour aller plus loin

	Contact	AgromisaP.O. Box 41, 6700 AA, Wageningen
Tel.:(31) 317 412 217, Fax: (31) 317 419 178, E-mail: agromisa@wxs.nl
Site web: www.antenna.nl/~agromisa/