This research investigates the effects of different extraction processes on the extractability and quality of rice bran oil. The extraction processes included hexane extraction (HE) as Control 1, cold press extraction (CE) as Control 2, ultrasonic pre-treatment combined with cold press extraction (UCE), and thermal cooking combined with cold press extraction (CCE). The results showed that oil extractability was positively correlated to ultrasonic power and duration; and to thermal cooking time. Meanwhile, the oil quality and ultrasonic intensity and thermal cooking period were inversely correlated. Specifically, the oxidative stability, and unsaturated fatty acids of short-period CCE oil were significantly higher than those of long-period CCE oil and higher-power and longer-duration UCE oil. Similar to HE and CE oils, oleic, linoleic, and palmitic acids were the dominant fatty acids in short-period CCE oil. Essentially, short-period CCE is optimal for rice bran oil extraction due to improved oil extractability and quality. Practical applicationsRice bran oil is an excellent source of unsaturated fatty acids and natural antioxidants. It also has many proven health benefits. There are two conventional production methods of rice bran oil:pressing and solvent extraction. While the pressing method achieves low oil extractability, solvent extraction could deteriorate the oil quality. This research, thus, proposes two chemical-free extraction techniques for rice bran oil that improves the oil extractability and preserves the oil quality: ultrasonic pretreatment combined with cold press extraction (UCE) and thermal cooking pretreatment combined with cold press extraction (CCE). The findings are expected to offer a possible solution to the extractability-quality challenges associated with the conventional extraction methods.

This research establishes the optimal microwave‐assisted alkali pretreatment (MAP) condition of cassava rhizome (CR) using response surface methodology with Box–Behnken design for enhanced enzymatic hydrolysis glucose yield. The pretreatment parameters included microwave power (300–900 W), irradiation time (5–15 min), and NaOH concentration (3%–7% w/v); and the enzymatic hydrolysis was 24 and 48 hr. Quadratic models were generated and statistical analysis performed to validate the adequacy of the models. The results indicated that the optimal MAP condition was 840 W microwave power, 9 min irradiation time, and 3% w/v NaOH concentration. Under the optimal condition, the predicted and experimental glucose yields were 15.39 and 15.82 g/100 g native cassava rhizome (NCR) for 24 hr hydrolysis, and 16.40 and 16.95 g/100 g NCR for 48 hr hydrolysis, indicating good agreement. In addition, this study examined the effect of MAP on the physical characteristics and morphology of NCR and pretreated CR. The results showed significant structural changes in pretreated CR, indicating that MAP enhanced enzymatic accessibility and glucose yield.

The aim of this study was to determine the effect of germination process (i.e., soaking time and temperature, germination time, and ultrasound treatment) on the germination rate of germinated paddy. In addition, gamma-aminobutyric acid (GABA) content, and morphology of starch granule of dehulled germinated paddy (germinated brown rice, GB) were characterized. The results showed that extended soaking time from 4 h to 24 h insignificantly increased the germination rate, and increased soaking temperature from 30°C to 40°C had no effect on germination rate (p>0.05). However, extended germination time from 14 h to 48 h significantly improved the germination rate, given soaking time and temperature of 2-8 h at 30°C (p<0.05). Ultrasound treatment for 15 min after 8 h soaking significantly increased the germination rate of 24 h germination, compared with non-ultrasound and ultrasound treatment for 15 min before 8 h soaking. Meanwhile, extended germination time to 48 h, the ultrasound treatment had no effect on the germination rate (p>0.05). The germination process did not affect the morphology of the GB starch granule, compared with brown rice (BR). However, GaBa content of GB (11.67 mg/l00g) was significantly higher than that of BR (1.08 mg/100g) (p<0.05).

This research investigated the physicochemical properties, bioactive compounds, and microstructure of brown rice (BR) and non-parboiled and parboiled germinated brown rice (GBR and PGBR). The GBR and PGBR were treated by sun, hot-air oven, or infrared irradiation (IR) drying. The results showed that IR drying enhanced the bioactive compounds of non-parboiled GBR, including γ-aminobutyric acid, α-tocopherol, and total phenolic compounds, while γ-oryzanol and antioxidant activity were comparable to BR. Meanwhile, IR drying significantly improved the head rice yield (HRY) of PGBR while reducing fissured grains. Parboiling also affected the color values of rice grains, suggesting the diffusion of husk color into endosperm and the formation of brown polymers by the Maillard reaction. In addition, IR drying altered the internal structure of rice grains, resulting in abundant intercellular voids. Specifically, the IRdried non-parboiled GBR significantly enhanced essential bioactive compounds and improved HRY while maintaining the color of standard BR.

This research investigates the effects of different extraction processes on the oil extractability, oxidative stability, bioactive compounds, and antioxidant activity of crude rice bran oil (CRBO). The experimental extraction processes include hexane extraction (HE), cold press extraction (CE), thermally pretreated cold press extraction (CCE), and ultrasound-pretreated cold press extraction (UCE). The results show that thermal cooking and ultrasound pretreatment significantly improve the oil extractability of the cold press extraction process. The oil yields of CE, CCE, and UCE were 14.27, 17.31, and 16.68 g oil/100 g rice bran, respectively. The oxidative stability of CE and CCE oils was higher than HE and UCE oils, as evidenced by the synchrotron-radiation-based Fourier transform infrared (SR-FTIR) absorption peak. The ρ-anisidine values of HE, CE, CCE, and UCE were 0.30, 0.20, 0.91, and 0.31, respectively. Meanwhile, ultrasound pretreatment significantly reduced the bioactive compounds and chemical antioxidant activity of UCE oil. The CE, CCE, and UCE oils (0.1% oil concentration) exhibited higher inhibitory effects against hydrogen-peroxide-induced cellular oxidative stress, compared to HE oil (0.39% oil concentration). Essentially, CCE is operationally and environmentally suitable for improving the oil yield, oxidative stability, bioactive compounds, and antioxidant activities of CRBO.