Hemp seeds can be processed just like any other oilseed to produce oil (see fact sheets FAPC-153 Oil and Oilseed Processing I: Oilseed Handling, Storage and Pre-treatment; FAPC-159 Oil and Oilseed Processing II: Oil Extraction Techniques; and FAPC-160 Oil and Oilseed Processing III: Crude Oil Refining and Preparation for Biodiesel Production). In summary, seeds are separated from foreign matter such as stones, metal pieces and other seeds and plant parts. Then, they are conditioned to adjust seed moisture. Mechanical pressing and/or solvent extraction, usually with hexane, are two common techniques used to recover oil from seeds. Crude oil from the extraction process goes through a series of refining processes depending on the end use.
Appearance of hemp derived oils on grocery shelves have caused some confusion with consumers. Although hemp seed oil use is legal for food products, CBD oil is not. CBD oil is an essential oil obtained from the leaves and flowers of hemp plant and has very different chemical composition than hemp seed oil.
Hemp, Cannabis sativa L., is an ancient crop. Although there is no recorded corroboration, it is believed hemp might have been grown in China 20,000 years ago. By the 16th century, hemp was a cash crop widely utilized for both its fiber and seed in Europe. Hemp was introduced to America in the New England region in 1645. Hemp-derived products were replaced with cotton products during the late 1800s due to the technical advancements in cotton ginning and reduced labor cost. Cordage and sailcloth were mainly made of hemp fiber, but demand for hemp further declined with the introduction of steam and petroleum powered ships.
Hemp seed oil contains high concentration of polyunsaturated fatty acid (PUFA) (70-90%) and is a good dietary source of essential fatty acids, linoleic and linolenic acids (see fact sheet FAPC-196 Lipid Glossary). Linoleic acid (50-70%) is the major fatty acid in the seed oil. Hemp seed oil is considered healthy because of its desirable omega-6: omega-3 fatty acid ratio, 3:1 (see fact sheet FAPC-135: Foods, Health and Omega-3 Oils). Although the omega-6: omega-3 ratio between 3:1 and 5:1 is considered optimal for good health, the topic is still controversial. Unlike many other commodity seed oils, hemp seed oil contains significant amount of γ -linolenic (GLA), 0.5-6%, and stearadonic acid (SDA), 0.3-2.5%. GLA is an omega-6 PUFA found in human milk and several botanical seed oils such as borage, blackcurrant and evening primrose and typically consumed as a dietary supplement. There are scientific reports indicating GLA supplemented diets decrease various inflammatory reactions. SDA is an omega-3 fatty acid that serves as a precursor for production of other omega-3 fatty acids. In humans, dietary SDA is easily converted to health beneficial long chain omega-3 fatty acid eicosapentaenoic acid (EPA) (see fact sheet FAPC-135: Foods, Health and Omega-3 Oils). Hemp seeds grown in extreme northern and tropical regions are reported to have higher GLA and SDA concentrations than the seeds grown in moderate climates. Saturated fatty acid content, palmitic and stearic acids of hemp seed oil range from 5-9% and 2-3%, respectively.
Solvent extracted hemp seed oil is liquid at room temperature and has a yellow color, bland taste and a nutty aroma. Organoleptic properties of hemp seed oil may vary depending on the seed growth location, oil extraction conditions and seed maturity. It may have a strong, pungent flavor. The taste of the oil also is affected by postharvest management practices, i.e. high temperature drying, leading to formation of increased amount of volatile compounds, peroxides and free fatty acids, and quality deterioration (see fact sheet FAPC-197 Edible Oil Quality). The refractive index and specific gravity of refined oil at 40 degrees C and 20 degrees C are 1.4570 and 0.8927, respectively. Crude hemp seed oil has a higher specific gravity, 0.9200, than for refined oil. Hemp seed oil has lower melting and smoke points than commodity cooking oils because of its high PUFA content.
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