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Thomson navel orange peel is a by‐product of citrus processing, which contains high levels of bioactive compounds advantageous to human health, nevertheless due to its high moisture content it is exceedingly perishable. Drying is among the most common preservation methods, which could prolong the plants shelf‐life via reducing their moisture value. Taking this into account, depending on their type and conditions, drying techniques could degrade plant heat‐sensitive metabolites and lead to quality decline. Therefore, the goal of this paper was to investigate the influence of seven drying methods named sun, shade, oven, vacuum oven, microwave, and freeze‐drying with different drying conditions on the physical properties, for example, bulk density and color (L*, a*, b*, ΔE, and browning index (BI)) and essential oil characteristics such as extraction yield, chemical composition, antioxidant (total phenolic content (TPC), DPPH, and FRAP essays), and antimicrobial (MIC and MBC) activities of Thomson peel and determine the superior drying procedure. Results showed that freeze‐dried sample had the highest retention of L* (48.54) and b* (49.00) values, lowest BI (216.11) as well as highest EO extraction yield (6.90%), TPC (60.10 GAE/100 g), FRAP (0.52% at 80 mg/ml), and lowest IC50 (5.00 mg/ml), MIC and MBC compared with other drying treatments. Therefore, it could be inferred that freeze‐drying is the most efficient drying approach in respect of preserving both physical and EO attributes of Thomson peel.

Soybean oil is an essential ingredient for cooking (Yu et al., 2019), which still has the largest share of vegetable oil production around the world. Due to high levels of polyunsaturated fatty acids including linoleic acid (C18:2) and linolenic acid (C18:3) the soybean oil has low oxidative stability. The oxidation reactions decrease the nutritional value, organoleptic quality, and the shelf life of the oils and fats (Lanna, José, Oliveira, Barros, & Moreira, 2005). In addition, the formation of oxidized products such as free radicals can cause premature aging, heart disease, and cancer (Yassari & Yasari, 2013). The use of antioxidants is generally recognized as an efficient method to stabilize edible oils and prevent peroxide reactions (Ghaderi-Ghahfarokhi, Barzegar, Sahari, & Azizi, 2016). Utilization of synthetic antioxidants such as tert-butyl hydroquinone (TBHQ) to prevent lipid oxidation is a common method, but because of their possible adverse effects on health, the demand to utilize natural antioxidants has increased in recent years. Several studies have explored

In this study, the effect of solvent ratio of hexane to isopropanol (0:100, 50:50, and 100:0 v/v%), extraction temperature (30, 45, and 60°C), and time (30, 60, and 90 min) were investigated on the oil extraction efficiency, total phenol content, DPPH radical scavenging, peroxide value, and oil color index. Extraction conditions were optimized by response surface methodology and Box–Behnken design. The optimal conditions were obtained as hexane‐to‐isopropanol ratio of approximately 3:2, temperature of 40.26°C, and ultrasonication time of 54.40 min. Then, the hemp seed oil was extracted under the optimal conditions. The optimal predicted contents for oil yield (31.22%), total phenolics (3.19 mg GA/g oil), DPPH inhibition (73.86%), peroxide (4.62 meq/kg), and color index (28.2) were agreed with the predicted conditions because the RSE values were less than 5%. Hemp seed oil can be used extensively due to its high nutritional values, and antioxidant potential and ultrasound can improve oil extraction as a simple and fast method.

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