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Studies on the Processing and Properties of Soymilk

A. Aziz Sarker
Soyabean Project, BARC,, Dhanmondi, Dhaka.

A. Khaleque
Director
Division of Food Science and Technology, BCSIR- Laboratories, Dhanmondi, Dhaka.

Abstract/ Executive Summary:

The effect of pH, temperature and calcium salt on the precipitation of protein from soymilk has thoroughly been studied and the optimum conditions for its recovery have been standardised. The highest recovery of protein was obtained at pH 4.5 after heating the sample at a temperature of 65°C for a short time. The recovery of protein precipitated by adding 1% calcium salt plus heated to 65^oC, was very similar to that obtained by isoelcctric precipitation. The proximate composition of the protein isolates and whey solids has been determined and their possible utilization have been discussed. The composition of its component parts have also been reported.

Keywords: Soy milk, Human consumption, Processing, Protein recovery

Location: Division of Food Science and Technology, BCSIR- Laboratories,Dhaka.

Start Date: 00-00-0000

End Date: 00-00-0000

Program Area: Postharvest and Agro-processing

Commodity: Milk

Objectives:

1. To standardize the conditions for separation of proteins from soymilk for using in various food products instead of protein from cow milk .

2. To evaluate protein quality for human consumption.

Methodology:

The variety of soybean used throughout this study was Lee- 74. The milk was prepared according to the method described in the previous communication. Moisture, fat, ash and crude fibre contents were determined by the AOAC methods (1955). The nitrogen was determined by the kjeldahl method and the protein content was calculated by using the conversion factor 6.25. The carbohydrate level was estimated by difference. 100 ml of soymilk were taken in each beaker and adjusted the various pH levels by slowly adding in hydrochloric acid. Each sample was centrifuged at a speed of 2000 rpm for 10 minutes. The curd fraction was dried in a hot air oven at a temperature of 105⁰C±2^oC until constant weight was achieved. The protein of the dried curd fraction was determined and the p^Hat which maximum protein obtained was selected for further experiments. The p^H of the soymiIk was adjusted to the level at which highest yield of protein obtained and the contents were heated at various temperatures for 3-5 minutes. After cooling the samples, the protein was separated in the same way as mentioned above.

The protein fraction was precipitated from the soymilk sample by adding a suspension of calcium sulphate in various proportions. The contents were heated at a temperature of 65⁰C until the whey was clear. The precipitate was separated by centrifugation and dried. The protein content was determined in the same way as described above.100 ml of the soymilk whey were taken in a porcelain basin and evaporated to dryness on a water bath. The sample was further dried in an oven at 1 05⁰C±2°C until constant weight was achieved. 100 ml of soymilk whey were taken and concentrated to 25 ml over water bath. 50% trichloroacetic acid (TCA) solution was added drop wise until the precipitation of proteins was completed. The sample was kept over night at a temperature of 1°C and centrifuged at a speed of 2000 rpm for 10 minutes. The nitrogen content in the supernatent was determined by kjeldahl method as described above.

Source of Information: Bangladesh Journal of Agriculture, Vol-3, No-1, June-1978,Page:277-282

Article Link (Online Journal):

Funding Source:

1. Bangladesh Agricultural Research Council

Budget:

Total Budget (Tk.) :

Achievement/Findings:

The highest recovery of protein was obtained at pH 4.5 after heating the sample at a temperature of 65°C for a short time. The recovery of protein precipitated by adding 1% calcium salt plus heated to 65^oC, was very similar to that obtained by isoelectric precipitation. The proximate composition of the protein isolates and whey solids has been determined and their possible utilization have been discussed.

Knowledge Management: Journal