The process of making vegetable oil from palm kernels involves several key steps to extract and refine the oil. Here's a breakdown:
The provided short answer outlines the refining process after the oil has been extracted. Let's first address the oil extraction itself, and then the refining.
I. Palm Kernel Oil Extraction
Palm kernel oil is extracted from the kernel, or seed, inside the palm fruit. The primary methods are:
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Mechanical Pressing (Expelling): This involves using a screw press to physically squeeze the oil out of the kernels. It's a simpler and more traditional method.
- The kernels are first cleaned and dried to reduce moisture content.
- Then, they are fed into the screw press, which applies high pressure.
- The oil is expelled, and the remaining solid material (kernel cake) is separated.
- This crude oil contains impurities and requires further refining.
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Solvent Extraction: This method uses a solvent, typically hexane, to dissolve the oil from the kernels. It's more efficient than mechanical pressing and extracts a higher percentage of oil.
- The kernels are prepared similarly to mechanical pressing.
- The kernels are then mixed with hexane, which dissolves the oil.
- The solvent-oil mixture (miscella) is separated from the solid residue.
- The solvent is then evaporated from the miscella, leaving behind the crude oil.
- The solvent is recovered and reused.
- This crude oil also requires refining.
II. Palm Kernel Oil Refining
Once the crude palm kernel oil is extracted, it needs to be refined to remove impurities and improve its quality, color, and odor. The refining process generally includes the following steps:
1. Degumming (Hydration Degumming)
- Purpose: To remove phospholipids (gums) which can cause problems during processing and affect oil quality.
- Process: Hot water or acid is added to the crude oil. This hydrates the phospholipids, making them insoluble and allowing them to be separated from the oil through settling or centrifugation.
2. Deacidification (Alkaline Neutralization)
- Purpose: To remove free fatty acids (FFAs), which contribute to rancidity and poor flavor.
- Process: An alkali solution (e.g., sodium hydroxide) is added to the oil. The alkali reacts with the FFAs to form soapstock, which is then separated from the oil.
3. Bleaching (White Soil Adsorption Decolorization)
- Purpose: To remove pigments and other color impurities, resulting in a lighter-colored oil.
- Process: The oil is treated with an adsorbent material, such as bleaching earth (clay), which adsorbs the color pigments and other impurities. The bleaching earth is then filtered out, leaving behind a decolorized oil.
4. Deodorization (High Temperature Distillation Deodorization)
- Purpose: To remove volatile compounds that cause undesirable odors and flavors.
- Process: The oil is subjected to high temperatures (typically 200-250°C) and a vacuum, and steam is injected. This process volatilizes the odoriferous compounds, which are then removed, leaving behind a bland, odorless oil.
After deodorization, the refined palm kernel oil may undergo further processing, such as fractionation (separation into different fractions based on melting point) or modification (e.g., hydrogenation) to meet specific application requirements.
