Hemp (Cannabis sativa L.) is a source of nutritious seeds that have been used as human food for thousands of years. The seeds contain nonmedicinal levels (<0.3%) of the psychoactive compound called δ-9-tetrahydrocannabinol (THC) and, therefore, are different from medicinal marijuana. Currently, hemp seed is processed mainly by mechanical pressing to extract the valuable oil, while the residue is used to produce various protein-rich food products. Hemp seed contains the salt-soluble globulins or edestin (
75%) and the water-soluble albumin (
25%) as the main storage proteins. Hemp seed proteins have a high level of arginine and a sulfur-rich protein fraction, two unique features that impart high nutritional values. Functional property evaluations have shown that hemp proteins form high-quality emulsions with oil droplet sizes similar to those of milk-based emulsions. A novel hemp seed protein concentrate has been shown to have >70% solubility at pH 4.0–6.0, whereas most plant proteins are typically insoluble. Addition of hemp seed protein to polycystic kidney disease rat diet led to reduced pathological intensity of renal disease and amelioration of associated cardiovascular impairment. Moreover, hemp seed enzymatic hydrolysates have proven effective during in vitro and in vivo tests as antioxidant and antihypertensive agents. Therefore, hemp seed proteins and hydrolysates have the potential to be used as ingredients to formulate functional foods.
In this study, eight cultivars of hempseed were collected from different regions of China for analysis of physiochemical properties and chemical composition, as well as for seed indexes and proximate composition of seed kernel. The results indicated that Yunma No. 1 and Bama Huoma, with more than 50% oil and 30% protein in dehulled seed, could be considered as oil extraction material and protein source with respect to kernel yield. Iodine values ranging from 153.6 to 169.1 g/100 g reflected the high degree of unsaturation. The concentration of unsaturated fatty acids exceeded 90%, higher than most conventional vegetable oils. Moreover, polyunsaturated fatty acids ranged from 76.26% to 82.75% and were mainly composed of linoleic acid and α-linolenic acid with a ratio close to 3:1. γ-Tocopherol was found at an average concentration of 28.23 mg/100 g of hempseed oil. The results indicated that hempseed oil is a potentially valuable vegetable oil.
High PUFA content and favorable omega-6: omega-3 fatty acid ratio of hemp seed oil provides opportunities for development of specialty nutritional formulations. Currently, hemp seed and oil markets are quite small due to the limited production and processing capacity available. Most of the products can be categorized as specialty rather than commodity products. Protein powders, specialty oils, energy bars and drinks, hemp milk and butter are some of the popular edible products. Mechanically pressed hemp seed oil is utilized as salad dressing, but oil is not suitable for high temperature applications because of its high unsaturated fatty acid content. Hemp seed oil is the main ingredient in a wide range of cosmetic products including liquid and bar soaps, creams, lotions and lip balm. Adulteration of hemp seed oil can be an issue due to its relatively higher value than commodity oils.
Hemp seeds, which are fruits of Cannabis sativa, have round shapes with diameters ranging from 3.0 to 5.0 mm and are dark red brown color. Seeds are covered by a thin two layered pericarp and have an endosperm and two cotyledons inside. Hempseeds contain about 25-30% oil, 25-30% protein, 30-40% fiber and 6-7% moisture. Chemical composition of the seeds varies significantly depending on the hemp cultivar planted.
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.
Properties of Hemp Seed Oil
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.
There are more than 40 hemp cultivars. Finola is the most common cultivar planted for commercial purposes. Hemp can be grown for seed, fiber or oil. Industrial hemp seeds are planted very closely to encourage fiber production and depress leaf development, whereas hemp grown for seed is planted farther apart. Hemp can be used in food or feed formulations provided the products are approved by the Food and Drug Administration (FDA) for food and the Association of American Feed Control Officials (AAFCO) for feed products. Hemp seed and hemp seed oil can be utilized in food products. Currently, there is no approved use for any form of hemp as a feed ingredient.
Commercially refined hemp seed oil contains significantly higher unsaponifiable (see fact sheet FAPC-196 Lipid Glossary) content than that of many commodity oils. This is partly due to the high phytosterol (plant sterols) content of the oil. Numerous studies have demonstrated ingestion of phytosterols lowers low-density lipoprotein (LDL) levels in human blood. Tocopherols are the most important natural antioxidants. Tocopherol content of hemp seed oil varies between 76.4 and 92.1 mg/100 g oil, which is similar to many other seed oils such as soybean and sunflower 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.