Palm fruits need to be killed before pressing palm oil (also known as inactivation of enzymes), mainly for the following reasons and effects:

Reasons

• Preventing Microbial Growth and Fermentation : After harvesting, palm fruits contain sugars and moisture that attract a wide range of microorganisms, such as yeasts and lactic acid bacteria. If sterilization is not performed promptly, these microorganisms will proliferate and ferment within the fruit pulp. This process can lead to the breakdown of sugars into alcohol and carbon dioxide, producing unpleasant odors and causing the oil to spoil, thereby degrading its quality.
• Impact of Enzymes : Palm fruits naturally contain various enzymes, including lipase, peroxidase, and polyphenol oxidase. Lipase can hydrolyze oils, generating free fatty acids and increasing the oil’s acidity, which negatively affects its quality and stability. Peroxidase catalyzes the oxidation of oils, producing peroxides and other harmful substances that impart a rancid taste and shorten the oil’s shelf life. Polyphenol oxidase oxidizes polyphenolic compounds in the fruit pulp, leading to darker oil coloration and an undesirable appearance.

Functions

• Inhibiting Enzyme Activity : The sterilization process effectively inhibits or deactivates these enzymes, preventing the aforementioned adverse effects and ensuring the oil’s quality and stability.
• Preventing Oil Oxidation : During the pressing process, the rupture of fruit cells exposes the oils to air. Without sterilization, the unsaturated fatty acids in the oils are prone to oxidation. Sterilization helps prevent this oxidation, reducing the formation of peroxides and other harmful substances, thereby ensuring the oil’s quality and safety.
• Maintaining Oil Color : By inhibiting the activity of polyphenol oxidase, sterilization prevents the darkening of the oils. This step is crucial for achieving the desired oil color during subsequent refining processes.
• Preventing Oil Loss : Sterilization prevents the loss and transformation of oils within the fruit pulp, ensuring that a greater amount of oil can be effectively extracted. This process ultimately increases the oil extraction rate.