| 摘要 |
1398799 Fermented milk products STICHTING BEDRIJVEN VAN HET NEDERLANDS INSTITUUT VOOR ZUIVELONDERZOEK 3 April 1973 [7 April 1972] 15886/73. Heading A2B Fermented milk products e.g. yoghurt, cultured buttermilk, and lactic starters, are made continuously by a method comprising the following steps:- (a) continuously adding milk to a fermenting mixture comprsing milk and a starter in a pre-fermenting tank 6, while maintaining the pH at a value above that at which stiring causes syneresis, (b) passing the fermenting mixture from the pre-fermenting tank 6 to a coagulating tank 12 having an outlet in its base, the rate of supply of fermenting mixture to the coagulating tank being substantially equal to the rate of supply of milk from the tank 1 to the pre-fermenting tank, (c) passing the fermenting mixture through the coagulating tank in the form of a plug stream, thus allowing further fermentation and coagulation to take place, (d) shearing the part of the plug stream having acidity sufficiently high that stirring does not cause syneresis, and (e) collecting the sheared material of step (d) as product. If the product is yoghurt step (a) is carried out at 42 to 48‹C and above pH 5.6 and in step (d), the part of the plug stream at 33 to 37‹C and below pH 4.7 is sheared. If the product is Bulgarian yoghurt step (a) is at 42 to 48‹C and above pH 5.6 whilst shearing in step (d) is at 33 to 37‹C and below pH 5.1. If the product is cultured buttermilk or lactic starter step (a) is at 20 to 35‹C and above pH 5.3 whilst shearing in step (d) is below pH 4.7. The prefermented mixture may be passed through a cooler 10 on its way to the cogaulating tank. The prefermented mixture may be sprayed into the coagulating tank through a distributing device 11 and the walls of the coagulating tank may be coated with a surface active compound e.g. lacithin or PTFE. The rate of travel of the plug stream is at most 5 cm/min. The pH of the material in the prefermenting tank is kept constant by a pH sensor 5 which controls the pump 2 for pumping milk from the tank 1. The pre-fermenting tank also contains a stirrer 7 and a temperature sensor 8. The distributing device 1 1may be a rotatable disc. The coagulating tank may be double-walled. The shearing means 14 may be a perforated plate movable axially in the coagulating tank, the perforations occupying not more than 20% of the area of the plate. The plate is moved upwardly at at least 1 cm/sec and downwardly at not more than 5 cm/min. The pump 13 in the outlet of the coagulating tank is activated by a pH sensor 15 or a level sensor 16 or it may be activated at a predetermined time after the commencement of filling of the coagulation tank.
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