Fish oil is a substance derived from the tissues of oily fish. It is recognized for its valuable content of omega-3 fatty acids, specifically eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA). The oil extracted from these fish is processed for various applications, including dietary supplements for human consumption.
Key Fish Species Used
Commercial fish oil is primarily sourced from several species of small, oily, and cold-water fish. Among the most common are anchovies, sardines, mackerel, and herring. These species are often found in large schools, making them efficient targets for fisheries. While some fish oil may also come from salmon or tuna, the smaller, more abundant species generally form the backbone of the industry.
Anchovies are a significant source, contributing substantially to global fish oil production. Sardines are also widely utilized. Mackerel and herring are similarly important sources for fish oil.
Why Specific Fish are Chosen
These particular fish species are selected for fish oil production due to their high content of beneficial omega-3 fatty acids, primarily EPA and DHA. Fish do not synthesize these omega-3s but accumulate them from their diet, making certain species naturally rich in these compounds.
Another reason for their preference is their position low on the marine food chain. Smaller, shorter-lived fish like anchovies and sardines tend to accumulate fewer contaminants, such as mercury, compared to larger, predatory fish. Mercury levels increase through a process called biomagnification as it moves up the food chain.
These small pelagic species are also chosen for their relative abundance and reproductive rates, contributing to their sustainability. Despite their importance as a food source for other marine life, their fast growth and short lifespans allow for more consistent populations compared to larger, longer-lived fish. This biological characteristic supports the consistent supply needed for large-scale fish oil production.
From Fish to Oil: The Extraction Process
The journey from fish to oil typically begins with a process known as wet rendering or wet pressing. First, the raw fish material is cooked at temperatures ranging from 90 to 100 degrees Celsius. This cooking step breaks down the fish tissues, coagulates proteins, and releases the oil and water components.
Following cooking, the cooked fish mass undergoes mechanical pressing to separate the liquid fraction, which contains the oil and water, from the solid fish meal. The liquid mixture then proceeds to decantation and centrifugation, where the oil is separated from the water and any remaining dissolved solids. This initial separation yields crude fish oil.
The crude oil then undergoes a series of refining and purification steps to ensure its quality and safety. These steps often include degumming to remove phospholipids, neutralization to eliminate free fatty acids, and bleaching to improve color and remove oxidation products. Finally, deodorization is performed to remove volatile compounds responsible for fishy odors, resulting in a more palatable product. For high-purity applications, an additional step called molecular distillation may be employed to further concentrate omega-3s and remove heavy metals or environmental contaminants.