Comparison of Furans Formation and Volatile Aldehydes Profiles of Four Different Vegetable Oils During Thermal Oxidation.

The evolution of volatile aldehydes and the conversion of oxygenated ityß-unsaturated aldehydes (OαßUAs) into furans were compared in four vegetable oils (soybean oil, olive oil [OVO], peanut oil [PO], and perilla oil [PAO]) thermally oxidized at temperatures of 150, 180, and 210 °C for 10 hr/day over a 3-day period. Results showed that 2 alkyl furans and 23 volatile aldehydes including 4 toxic OdßUAs were detected by GC-MS. The original fatty acid compositions of the oils played a key role in the type and concentration of those volatile compounds. 4-Hydroxy-2-hexenal (HHE) and ethyl furan were only detected in PAO with a high content of linolenic acid, while the greatest level of pentyl furan was detected in PO with abundant linoleic acid. Greater amounts of 4-hydroxy-(E)-2-nonenal (HNE) and 4-oxo-(E)-2-nonenal (ONE) were formed in the OVO with abundant oleic acid. The close relativity of HHE and ethyl furan was also demonstrated. With principal component analysis, these vegetable oils could be discriminated based on their fatty acids and volatile compounds. The loading plot confirmed that HHE and ethyl furan were derived from the linolenic acid oxidation and degradation. PRACTICAL APPLICATION: The chemometric results showed that the formation of the volatile components during heating in different vegetable oils has close correlation with the original fatty acids composition of vegetable oils. Our research has also confirmed the presence of toxic OɑßUAs in oils after heating. Considering that they are proven to generate lots of degenerative diseases, further studies are needed to establish the risk level of using certain oils in frying and seek effective methods to inhibit their formation.

Prediction of fatty acid composition in camellia oil by 1H NMR combined with PLS regression.

A rapid method for the determination of fatty acid (FA) composition in camellia oils was developed based on the 1H NMR technique combined with partial least squares (PLS) method. Outliers detection, LVs optimization and data pre-processing selection were explored during the model building process. The results showed the optimal models for predicting the content of C18:1, C18:2, C18:3, saturated, unsaturated, monounsaturated and polyunsaturated FA were achieved by Pareto scaling (Par) pretreatment, with correlation coefficient (R2) above 0.99, the root mean square error of estimation and prediction (RMSEE, RMSEP) lower than 0.954 and 0.947, respectively. Mean-centering (Ctr) was more suitable for the model of C16:0 and C18:0 with the best performance indicators (R2 ≥ 0.945, RMSEE ≤ 0.377, RMSEP ≤ 0.212). This study indicated that 1H NMR has the potential to be applied as a rapid and routine method for the analysis of FA composition in camellia oils.

Comparison of (poly)phenolic compounds and antioxidant properties of pomace extracts from kiwi and grape juice.

The aim of this study was to evaluate the phenolic profile of grape and kiwi juice pomace by HPLC-ESI-MS, and their correlation with antioxidant properties determined with DPPH, FRAP and OH scavenging assays. A total of 32 compounds have been identified including anthocyanins, flavonols, flavan-3-ols and phenolic acids. Significantly higher relative amounts of anthocyanin monoglucosides, flavan-3-ols (catechin, epicatechin, and procyanidin), and flavonols (quercetin and its derivatives) were found for grape pomace. Whereas kiwi pomace contained higher amounts of quinic acid, caffeic acid and its derivatives. Although grape pomace had higher total phenolic content (TPC), it showed lower OH scavenging capacity than kiwi pomace, but better DPPH scavenging activity and reducing power. This indicated that the antioxidant activities do not only rely on the TPC but also associate with their phenolic profiles. Overall the two pomaces could potentially be exploited as an inexpensive source of natural antioxidants for food production.