Develop a flow diagram for the plant, estimating the yield of crude soybean oil, isolated soy protein powder and phosphatide gum produced per tonne of dried soybeans.
Brief of the assignment
A small developing country currently produces and exports soy beans. There is an initiative to develop the food processing industry, including the production of soybean products for both domestic and overseas markets. You are asked to investigate the requirements of a plant for the manufacture of soybean oil plus protein isolates and lecithin-rich gum per tonne of dried soybeans, given the following information:
After harvest, beans are normally dried to approximately 10% (w/w) moisture content. The beans must be cleaned and dehulled before processing (note that the hulls make up about 7% (w/w) of the mass of dried soybeans). The dehulled beans contain about 10% (w/w) moisture, 36% (w/w) protein, 19% (w/w) fat, 31% (w/w) carbohydrate and 4% (w/w) ash.
The extent and rate of oil extraction, and solving requirement, are key economic considerations. Oil is usually extracted from flaked beans (approximately 0.3 mm thickness) using hexane, leaving a residual flour containing 0.5% (w/w) oil. The crude soybean oil contains 2% (w/w) phosphatides (lecithin-rich material), which can be removed as gum following addition of 1.5% (w/w) hot water to the oil.
The soluble proteins and carbohydrates are extracted from the defatted flour using dilute alkali (pH 8.5) in two stages, using water:flour ratios of 10:1 and then 6:1. The major protein fractions are precipitated at pH 4.5, and after washing to remove residual salts and carbohydrates, may be neutralised and dried to produce isolated soy protein powder containing 5% (w/w) moisture, 90% (w/w) protein, 4.2% (w/w) ash, 0.5% (w/w) fat and 0.3% (w/w) carbohydrate. It is a reasonable assumption that 85% (w/w) of the total protein from the defatted flour is recovered.
- Develop a flow diagram for the plant, estimating the yield of crude soybean oil, isolated soy protein powder and phosphatide gum produced per tonne of dried soybeans.
- Describe briefly the role of the individual unit operation of your flow diagram in the process.
- Discuss alternative unit operations where they exist in order to increase the sustainability of your process.
- Investigate and discuss which types of driers could be used to dehydrate soybeans from an initial moisture content of 70%, down to 10% (wet weight basis). Compare the advantages and limitations of the different driers.
- Identify and estimate the quantities of by-products (per tonne of dried soybeans) and discuss ways in which you can valorise them.
You are asked to critically discuss the questions and tasks given in the brief. The report must include references to appropriate primary sources of information. The report must include the following elements:
i. Introductory paragraph to provide a summary of the aims of the report
ii. The flow diagram of the process that you will develop in the workshop sessions
iii. Critical discussion of the questions given in the brief (you may use descriptive subheadings based on the questions outlined above for your report).
iv. List of references and sources of information used.
The report must be no longer than 3000 words(excluding reference list)
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