Casein production by lactic acid
1990
Sunanta Wiriyapirom
Coagulated casein at each pH in the range of 4.0-4.8 was 3.09-3.14 %. Skim milk pasteurized at temperature of 74+-1 deg. Celsius for 3 minutes was used as the starting material in lactic casein manufacturing. Lactic casein was produced by acidification to the desired pH, precipititation, cooking, separation, washing and then drying. At temperatures of 25, 35 and 45 deg. Celsius at pH 4.5. Analysis by the response surface method (RSM) showed that pH of 4.17-4.40 and temperature of 29.0-32.2 deg. Celsius were optimum conditions. Optimum pH of washing water of 4.5, which gave lowest loss during the process, was used for the following study. In scale-up lactic casein production, after precipitation at pH of 4.20-4.25 and temperature of 30 deg. celsius, the curd was washed three times in a vat. The ash content of casein ranged from 1.55-1.59 %. There was no difference in ash content between using wash water in a quantity equal to that of skim milk or to one-half the amount of skim milk, but with the latter treatment, lactose and free acidity were higher. There were no differences in free acidity, lactose and ash content in casein washed for 7 minutes or for 14 minutes. The optimum conditions were washing for 7 mimutes with an amount of water half the quantity of skim milk. The casein produced under these conditions had a moisture content of 6.57 %. On a dry basis, it was composed of 95.39 % protein, 1.55 % ash and 0.12 % lactose, which met the general standard specification, although the fat content (2.85 %) was higher.
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