Laboratory-Scale Optimization of Hemp Seed Roasting Temperature and Time for Producing a High-Quality Pressed Oil

Abstract

Roasting is widely applied in oil processing to improve the extraction yield and desired sensory characteristics. The current study is aimed at optimizing roasting conditions (time and temperature) of hemp (Cannabis sativa L.) seeds prior to seed pressing to improve the oil yield and antioxidant capacity, using response surface methodology based on central composite design (CCD). Hemp seeds were roasted at five temperatures (132, 140, 160, 180, and 188°C) and for five duration times (9, 15, 30, 45, and 51 min). Mathematical models have shown that roasting conditions significantly affected response variables ( p < 0.05 ), including oil yield, total phenolic content (TPC), radical scavenging activity, and oxidative stability index (OSI). The CCD led to the following optimum roasting conditions: 163°C for 15 min, which improved the extraction yield by 45% and oxidative stability by 80%. Thus, the oil produced under these conditions showed a yield of 23.09%, TPC of 121.21 mg GAE kg-1, and OSI of 21.37 hours. In addition, roasting hemp seeds under optimal conditions did not negatively influence the oil quality. Only chlorophylls, tocopherols, and palmitic acid slightly decreased ( p < 0.05 ) after roasting (from 39.10 to 36.54 mg kg-1, 483.06 to 469.77 mg kg-1, and 7.65 to 7.29%, respectively). Furthermore, the concentrations of most volatile compounds identified in unroasted hemp seeds decreased after roasting under optimal conditions, with the formation of new compounds sought for their positive attributes, such as pyrazines and aldehydes derived from the Strecker degradation, responsible for the roasted, nutty, and almond odors. The main volatile compounds in raw and roasted hemp seeds were β-myrcene (3170.30 and 1177.69 ng g-1, respectively) and D-limonene (1347.25 and 470.35 ng g-1, respectively). The results obtained in this study could provide valuable information for the food industry to produce hemp seed oil with high nutritional quality that meets consumer demands.

The Influence of the Used Bleaching Earth on the Content of Natural Dyes in Hemp (Cannabis sativa L.) Oils

“…Based on this, it can be concluded that their use to change color will be most justified, but in strictly controlled doses. Figure 1b shows that the mass of added bleaching earth is crucial in determining the effectiveness of color change in the CIE-Lab method, which is further confirmed by the work of Marrakchi et al [40] Doses of 2.5% by mass of BE5, BE6, and According to the work of Mansouri et al [43] and Tura et al [44] the initial content of natural dyes depends mainly on the hemp variety and pressing temperature. Moreover, increasing the processing temperature improves the solubility of chlorophylls and carotenoids in oils, which makes their removal more difficult.…”

“…BE7 had the most effective impact on the tested samples; the impacts of BE1 and BE2 were slightly lower, and BE5 and BE6 also had a considerable impact (Figure 2a). The remaining BEs did not significantly According to the work of Mansouri et al [43] and Tura et al [44] the initial content of natural dyes depends mainly on the hemp variety and pressing temperature. Moreover, increasing the processing temperature improves the solubility of chlorophylls and carotenoids in oils, which makes their removal more difficult.…”

Chemosensory of hemp seed oil extracted with hemp seed(Cannabis sativa L.) roasted under various conditions using electronic sensors and GC–MS/Olfactometry

“…The pyrazines detected in this study, including 2,5-dimethylpyrazine, 2,5-diethyl-3-methylpyrazine, and 2-ethyl-3,5-dimethylpyrazine, are known to be the aromas detected in roasted sunflower seeds, pumpkin seeds, and almonds( Mansouri et al, 2023 ). In particular, 2-ethyl-3,5-dimethylpyrazine exhibited values above the threshold and is believed to be the aroma of roasted hemp seeds( Mansouri et al, 2023 ), also exhibited the highest odor activity in this study and is believed to be the major odor active compound. The p-cymene, which was found to be responsible for the overall scent of the raw, is known to be one of the volatile compounds of the important terpenes found in Cannabis( Srivastava & Singh, 2019 ).…”

Hemp Seeds (Cannabis sativa L.) as a Valuable Source of Natural Ingredients for Functional Foods—A Review

“…The terpenes found in the highest concentration in hemp seed oil, which are considered key contributors to the unique aroma with odor activity values, are presented in Table 4. Studies have highlighted that terpenes in hemp seed oil play significant roles in protecting it against oxidative stress [19], due to their ability to scavenge free radicals [73]. Furthermore, research suggests terpenes can enhance well-being within a healthy lifestyle.…”