Rapeseed Kernel Oil and Protein Recovery via Steam-Expanded Press Cake
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Solution Overview
Problem
Existing methods for processing rapeseed to extract oil and protein are inefficient, result in high residual oil content, and do not produce high-quality cold-pressed rapeseed oil or rapeseed protein concentrate suitable for food and animal feed due to issues like protein denaturation, high hull content, and contamination risks.
Innovation Solution
A method involving hulling rapeseed kernels, limiting cake temperature to 70°C during pressing, expanding press cake with steam to create collets, and recycling a portion of the press cake to increase friction and reduce residual oil content, followed by solvent extraction to produce high-quality cold-pressed rapeseed oil and rapeseed protein concentrate.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If rapeseed kernels are hulled before pressing to obtain a hull-free press cake, then the quality of the press cake is improved, but the residual oil content becomes significantly higher than 15 percent by weight
Solution Approach 1:
The rapeseed kernels are hulled before pressing to remove hulls in advance, creating a hull-free or low-hull grain fraction that presses more efficiently with better temperature control and lower residual oil content
Solution Approach 2:
The water content of the low-hull grain fraction is optimized to 4 to 7% by weight before pressing, which improves pressing efficiency and reduces residual oil content while maintaining cake temperature below 70°C
2Object-affected harmful factors
If cold pressing is used to maintain temperatures below 50°C, then the trans fatty acid content is reduced to below 0.2%, but the residual oil content cannot be reduced below 15 percent by weight
Solution Approach 1:
The water content of the low-hull grain fraction is optimized to 4 to 7% by weight, which improves pressing efficiency and allows for lower residual oil content (18 to 28% by weight of dry mass) while maintaining cake temperature below 70°C and trans fatty acid content below 0.2%
Solution Approach 2:
A portion of the press cake is returned, mixed with the low-hull grain fraction before pressing, and pressed again, continuously improving oil extraction efficiency and reducing residual oil content
3Loss of substance
If rapeseed meal is produced by solvent extraction to reduce residual oil content, then the oil content is reduced to less than 1 percent by weight, but the meal cannot be used as a complete feed due to toxins and anti-nutritional ingredients
Solution Approach 1:
Hulls are separated from the rapeseed kernels before pressing through sieving and/or air classification, removing the primary source of toxins and anti-nutritional ingredients, so that the low-hull grain fraction contains no more than 4% by weight of hulls in the resulting press cake
Solution Approach 2:
The water content is optimized to 4 to 7% by weight and cake temperature is limited to 70°C, preserving protein quality and amino acid composition while achieving low residual oil content (18 to 28% by weight of dry mass) without requiring solvent extraction
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
This process achieves high-quality cold-pressed rapeseed oil with low trans fatty acid content and a rapeseed protein concentrate with over 60% protein content, suitable for food and animal feed, while maintaining amino acid composition and ensuring hygienic safety.
Implementation Method 1
The press cake is expanded with pressurized steam so that the press cake is temporarily heated to over 100°C under the influence of the steam, and the collets have a temperature of 80°C to 95°C after expansion
Implementation Method 2
a cake temperature in a resulting press cake is limited to 70°C
Implementation Method 3
The collets are extracted with an organic solvent, with a second residual oil content being reduced to 2% by weight or less of the dry mass of the collets
Data Source
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AI summary
In industrial processing, grains (4) of rapeseed are dehulled. Cold-pressed rapeseed kernel oil (25) is pressed from a low-hull grain fraction (6) having at most 4 weight percent of hulls and a water content of 4 to 7 weight percent. In a produced press cake (9), the cake temperature is limited to 70°C and a first residual oil content is reduced to 8 to 28 weight percent of the dry mass. Pressurized steam (30) is supplied, and the press cake (9) is subsequently expanded to form collets. The steam is metered in such a way that the press cake (9) is temporarily heated to above 100°C and that the collets have a temperature of 80°C to 95°C after the expansion. The collets are extracted by means of an organic solvent, a second residual oil content being reduced to 2 weight percent or less of the dry mass. After the expansion, some of the collets are returned and, before being pressed, are mixed with the low-hull grain fraction (6) in order to increase the friction when said collets are pressed again.