Determination of volatile compounds formed in a glucose–selenomethionine model system by gas chromatography–atomic emission detector and gas chromatography–mass spectrometry

Effect of Vacuum Roasting on Total Selenium Content of Selenium-Enriched Rapeseed, Maillard Reaction Products, Oxidative Stability and Physicochemical Properties of Selenium-Enriched Rapeseed Oil

Selenium-enriched rapeseed (SER) is an emerging oil seed. Roasting is beneficial in improving oil yield and promoting the release of micronutrients into SER oil, but high temperatures and dry air lead to selenium loss and fatty acid degradation in SER. To minimize the selenium loss and improve the SER oil quality, this study investigated the effects of vacuum (VC) roasting (90-170 °C for 30 min) on the SER selenium content, Maillard reaction products, oxidative stability, and physicochemical properties of SER oil, with conventional dry air (DA) roasting as the control. The results showed that the selenium loss in VC-roasted SER meals increased from 7.17 to 19.76% (90-170 °C for 30 min), which was 47.13 to 80.48% of that in DA-roasted SER meals, while no selenium was detected in the SER oils. Compared to DA roasting, VC roasting (90-170 °C for 30 min) reduced lipid oxidation products (LOPs), Maillard reaction products (MRPs), and benzo[a]pyrene contents, and increased carotenoids, unsaturated fatty acid contents, reaching a maximum oil yield of 35.58% at a lower temperature (130 °C for 30 min). Selenium contents exhibited a highly significant negative correlation with MRPs and LOPs (p ≤ 0.005). The VC roasting retarded selenium loss and improved SER oil quality compared to conventional DA roasting.

Organic Selenium as Antioxidant Additive in Mitigating Acrylamide in Coffee Beans Roasted via Conventional and Superheated Steam

Selenium is an essential micronutrient with significant antioxidant activity promising in mitigating the formation of acrylamide during high-temperature roasting. In this study, green coffee beans pretreated with selenium (Se-coffee) were investigated on their selenium uptake, selenium retention in green and roasted beans, antioxidant activities, and formation of acrylamide during conventional and superheated steam roasting. Comparisons were made with positive (pretreated without selenium) and negative (untreated) controls. The acrylamide formation was significantly inhibited in Se-coffee (108.9-165.3 μg/kg) compared to the positive and negative controls by 73.9% and 52.8%, respectively. The reduction of acrylamide by superheated steam roasting only observed in the untreated coffee beans (negative control) by 32.4% parallel to the increase in its antioxidant activity. Selenium pretreatment significantly increased antioxidant activity of the roasted Se-coffee beans after roasting although soaking pretreatment significantly reduced antioxidant activity in the green beans. Acrylamide reduction in the roasted coffee beans strongly correlated with the change in antioxidant capacities after roasting (∆FRAP, 0.858; ∆DPPH, 0.836). The results indicate that the antioxidant properties of the organic selenium suppressed acrylamide formation during coffee roasting.

Determination of the volatiles from tobacco by capillary gas chromatography with atomic emission detection and mass spectrometry

A new gas chromatograph-atomic emission detector (GC-AED) coupled with Deans switching technique for analyzing volatiles from tobaccos were developed. The detector operating parameters (reagent gas pressure and make-up gas flow rate) were optimized. The detection limits for the elements carbon (193 nm), hydrogen (486 nm) and oxygen (171 nm) ranged 0.05-0.2, 0.05-0.3 and 1-11 ng, respectively, depending on the compound. The sensitivity and linearity for the elements carbon (193 nm), hydrogen (486 nm) and oxygen (171 nm) decreased in the order O>H>C. Calibration curves were obtained by plotting peak area versus concentration, and the correlation coefficients relating to linearity were at least 0.9359. Elemental response factors measured on these channels, relative to the carbon 193-nm channel, were hydrogen, 0.38-0.48 (mean %RSD=5.64), and oxygen, 0.085-0.128 (mean %RSD=14.9). The evaluation was also done for the new technique and for an established GC-MS technique for the same real samples. The results of GC-AED and GC-MS showed that there was a relatively good agreement between the two sets of data.