Comparison between extraction techniques: Cold press techniques and ultrasound assisted maceration (uam) method

Hemp seed oils from Uso 31 monoecious variety were differently obtained by cold pressing or ultrasound-assisted maceration (UAM). In particular, the cold pressing technique was performed using an industrial scale plant and the extraction process was optimized by using nozzle of different diameters (6 mm, 8 mm and 15 mm), capable of imposing a different pressure, and therefore a different extraction temperature. These parameters influence the final product in terms of quality and chemical composition. Photosynthetic pigments (chlorophylls and carotenoids), total phenols, and total cannabidiol (CBD) were comparatively assessed, as well as the formation of conjugated dienes and trienes. The UAM technique gave a higher oil yield (+ 6.5%) than that obtained with the traditional cold extraction system. The analysis of photosynthetic pigments has shown that the chlorophyll content in cold extracted oils decreases with the increase in the diameter of the bush, and that this content is in any case higher (+ 56%) than the oil mixture obtained with UAM. Considering the carotenoid/chlorophyll ratio, it was possible to observe that UAM technique appears to relatively favor a quantity of carotenoids higher than chlorophylls. Values of ΔK lower than 0.010 were obtained for cold extracted oil with a 15 mm nozzle and for oils extracted with UAM. The data seem to confirm that the use of a larger bush provides the enrichment of the oil and does not compromise the goodness of the constituents with beneficial action. The ultrasound technology also benefits the extraction of phenolics and cannabidiolic acid. The results obtained, although they require further investigation, allow us to assert that the complexity of the hemp oil mixture needs to be evaluated in its fullness and in a different way from what is commonly used for other edible oils.