Improved Extraction Efficiency and Antioxidant Activity of Defatted Canola Meal Extract Phenolic Compounds Obtained from Air-Fried Seeds

Abstract

This study investigated the efficacy of roasting pre-treatment by air frying to enhance the extraction and recovery of the predominant sinapic acid derivatives (SADs) from roasted canola meal and the antioxidant potential of the methanolic extracts. Canola meal was obtained by air frying canola seed at 160, 170, 180 or 190 °C for 5, 10, 15 or 20 min. Oil was extracted using the Soxhlet method, and the de-oiled meal fraction was air-dried. Phenolic compounds were isolated using ultrasound-assisted extraction with 70% (v/v) methanol and then quantified by high-performance liquid chromatography-diode array detection. The antioxidant potential of the defatted meal methanolic extracts was evaluated using 2,2-diphenyl-1-picrylhydrazyl (DPPH), ferric reducing antioxidant power (FRAP), and metal ion-chelating activity (MIC) assays. The highest total phenolic content of 3.15 mg gallic acid equivalent/g dry weight was recorded in the defatted meal extract from seeds pre-treated with air frying at 190 °C for 15 min. Sinapine, sinapic acid and an unknown compound at a retention time (RT) of 26.6 min were the major sinapates identified in the defatted meal with the highest concentrations of 7572 ± 479.2 µg/g DW, 727 ± 43.45 µg/g DW and 1763 ± 73.5 µg/g DW, respectively, obtained at 160 °C for 5 min. Canolol (151.35 ± 7.65 µg/g DW) was detected after air frying at a temperature of 170 °C for 20 min. The FRAP and MIC correlated positively (r = 0.85) and generally decreased with increased air frying temperature-time conditions. The highest FRAP and MIC values of 0.53 mM and 80% were obtained at 160 °C for 5 and 20 min, respectively. The outcome of this study will contribute new knowledge that could improve the value addition and by-product utilization of canola seeds.

Thermal Processing via Air Frying Improves the Antioxidant Properties of Brassica Vegetables

“…Statistical analysis indicated that type of vegetable, method of processing and interaction between them were significant in the model statistics with an adjusted R 2 value of 0.996 (Table 1a). The previous studies by Nandasiri, et al [16] and Fadairo, et al [7,8] also showed improved TPC in canola and mustard by the application of air-frying. They observed highest TPC values for the canola meal substrate conditions at 190 o C for 15 minutes (3.15 ± 0.14 mg GAE/g DW) and 20 minutes (3.05 ± 0.02 mg GAE/g DW), respectively.…”

“…Air-frying/roasting of the vegetables was conducted using the method described by Fadairo et al [7,8] with slight modifications. The same instant pot (Instant Pot Duo Mini 3 Qt Model number: IPDUOMINI 3Qt) was used in here with the air-fryer extension.…”

“…The application of higher temperatures (>140 o C) for shorter time intervals during the process of air-frying and consistent circulation of hot air throughout the system make its ideal to preserve the nutrients and phenolic compounds without leaching out [7]. Furthermore, in both canola and mustard it was observed that certain thermo-generative phenolic compounds were also formed during the thermal process of air-frying including canolol [7,8,16,30,31]. Canolol and other thermo-generative phenolic compounds has demonstrated higher antioxidant potential in the respective studies.…”

The effect of pH on the phenolic content and antioxidant properties of three different mustard extracts

“…Extraction of phenolic compounds from oilseeds, including mustard, has been carried out for many years using a wide variety of methods in which canolol has gained considerable attention lately. Canolol is a thermally generated phenolic compound that is not naturally present (Fadairo et al., 2022; Nandasiri, Fadairo, et al., 2023; Nandasiri, Semenko, et al., 2023). However, with the application of thermal treatments, canolol is formed via decarboxylation of sinapic acid (Nandasiri, Fadairo, et al., 2023; Nandasiri, Semenko, et al., 2023).…”