Plants & Machinery for Milk Processing Industry
Plants & Machinery for Milk Processing Industry

Line for stirred yoghurt

Stirred yogurt production starts with milk fat and proteins standardization after which milk is homogenized and pasteurized. Heat treatment temperature and time are approximately 90°C for 5 minutes.

After homogenization and pasteurization, milk is let fermenting in ripening tank/s of variable size and equipped with an internal stirring system. Milk temperature at this stage is usually between 35-44°C.

During the fermentation, with inoculated milk completely resting, important physical, chemical, microbiological, organoleptic and nutritional modifications occur completely changing the characteristics of milk. Lactic acid starters use the lactose in milk and transform it into lactic acid.

Milk pH is reduced causing the consequent precipitation of the caseins. Fermentation completed, the mass of the alive lactic acid bacteria is approximately 1% of the total mass of the yogurt. The coagulum formed and the desired acidity reached, yogurt is stirred to obtain a homogeneous and creamy structure.

From the technological point of view the coagulum rupture is a very important phase of production enabling to obtain a product without lumps and whey separation.

The cooling phase is necessary to slow down the metabolic activities of lactic acid bacteria and to start product cooling.


To improve yoghurt commercial shelf-life, the product can undergo a thermal process by means of a dedicated tubular heat exchange.

Fruit mixer

Fruit and/or flavours can be added to stirred yoghurt before the filling. Yoghurt can also be added with fruit jam with pieces and, for this purpose, Sordi manufactures the ''Fruit Mixer'', an in-line yoghurt/fruits dosing system.

The double positive pump (yoghurt/fruit) system with flow-meters control is also used for the addition of fruits. Two flow-meters control the hourly output and consequently the yoghurt/fruit ratio.

The yoghurt plants can be controlled in automatic and/or manual mode.

Yoghurt ripening tanks

Tank with jacket for the passage of pressurized service fluids up to 4 kg/cm2 (max. test pressure 8 kg/cm2) and insulation by high-degree insulating material. The tank may be "ultraclean" type with sterile air or nitrogen. Sordi yoghurt ripening tanks are fitted with special variable speed agitator.

Available types of tanks:

  • With paddles
  • Tubular with circulation of the heating or cooling fluids
  • "U" shaped, for optimal cooking of the yoghurt coagulum