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.

Lemna minor (L. minor), the common duckweed, contains a high protein substance and is considered as a good source of potential bioactive peptides. The objective of this study is to investigate the effect of enzymatic hydrolysis times (60–180 min) and enzyme concentrations (0.5–3.5%v/w) with Alcalase and Flavourzyme on the recovery, hydrolysis degree (DH), and antioxidant properties of peptides derived from defatted L. minor. The protein recovery, hydrolysis degree (DH), and antioxidant activities obtained by enzymatic were compared with the alkaline treatment method. The results showed that the protein recovery, DH values, and antioxidant activities were enhanced by increasing the enzyme concentration and hydrolysis time. Specifically, the recovery of protein and DH values reached the highest level after the enzymatic hydrolysis by Flavourzyme or Alcalase at 1.5 v/w enzyme for 120 min. At the same enzymatic hydrolysis condition, the samples hydrolyzed by Flavourzyme had a higher inhibitory effect on the ABTS•+ and DPPH•+ radical scavenging than those hydrolyzed by Alcalase and the alkaline treatment. Further study also showed that the DH values, amino acid contents, and antioxidant activities of the protein extracts were positively correlated. Thus, the extractions with Flavourzyme and Alcalse were a good method to produce a significant amount of amino acids and smaller peptides.

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.

In this study, neutral oil was recovered from dried rice bran soapstock using ultrasound assisted solvent extraction (UASE). Response surface methodology (RSM) was employed to optimize the UASE parameters to obtain the maximum yield of neutral oil using face centered composite design (FCCD). The parameters included ultrasound power (0.5-4.5W/g), process temperature (35-55°C), and sonication time (4-26 min). The quadratic response models were generated and statistical analysis was performed to validate the models. The results showed that the optimum extraction conditions were ultrasound power of 3.75 W/g, process temperature of 49.71°C, and sonication time of 22.68 min. Ultrasound power and temperature were the most significant parameters for the extraction process. Under the optimal condition, the predicted neutral oil recovery was 98.10%, while corresponding experimental result was 98.21%, suggesting good agreement between the predicted and experimental data and high predictive ability of the models.

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