Influence of Temperature on the Fatty Acid Profile of Hemp (Cannabis sativa L.) Oil Grown in the Mediterranean Region

Considering the effects of increasing heat waves already underway, especially in several areas of the Mediterranean region, the study of the effect of temperature on the qualitative yield of hemp oil becomes necessary. Given this, an experiment was conducted in order to evaluate the effect of temperature during the grain-filling period on fatty acid accumulation and composition in hemp seed, comparing two locations with different temperature regimes, two years, two sowing times and two monoecious hemp varieties, characterized by different earliness. The accumulation of different fatty acids in hemp seeds at maturity seems to depend on the genetic background of the two genotypes studied. However, high temperatures also affect the activity of desaturase Δ12 and Δ15, which are responsible for the production of polyunsaturated fatty acids, in particular if greater than an 18 °C minimum night temperature and 30 °C maximum daily temperature, respectively. This result makes it possible to orient, even if partially, the qualitative characteristics of hemp oil for different uses, by identifying the suitable cultivation environment. Considering the Mediterranean area, hilly and foothill environments would favor the percentage of polyunsaturated fatty acid in the oil, with an improvement of the n-6/n-3 ratio, while the plain and warmer area, characterized by heat stress during the grain-filling period, would give an oil with an increased percentage of monounsaturated acids to the detriment of polyunsaturated fatty acid.