Stability and Antioxidant Activity of Annatto (Bixa orellana L.) Tocotrienols During Frying and in Fried Tortilla Chips

The Effect of High-Temperature Heating on Amounts of Bioactive Compounds and Antiradical Properties of Refined Rapeseed Oil Blended with Rapeseed, Coriander and Apricot Cold-Pressed Oils

Cold-pressed oils are rich sources of bioactive substances, which may protect triacylglycerols from degradation during frying. Nevertheless, these substances may decompose under high temperature. This work considers the content of bioactive substances in blends and their changes during high-temperature heating. Blends of refined rapeseed oil with 5% or 25% in one of three cold-pressed oils (rapeseed, coriander and apricot) were heated at 170 or 200 °C in a thin layer on a pan. All non-heated blends and cold-pressed oils were tested for fatty acid profile, content and composition of phytosterols, tocochromanols, chlorophyll and radical scavenging activity (RSA) analyzed by 2,2-diphenyl-1-picrylhydrazyl (DPPH), and 2,2'-azino-bis(3-ethylbenzothiazoline-6-sulphonic acid) (ABTS) assays. Moreover, the stability of phytosterols, tocochromanols, DPPH and ABTS values was determined in heated blends. All tocochromanols were lost during the heating process, in particular, at 200 °C. However, there were some differences between homologues. α-Tocopherol and δ-tocopherol were the most thermolabile and the most stable, respectively. Phytosterols were characterized by very high stability at both temperatures. We observed relationships between ABTS and DPPH values and contents of total tocochromanols and α-tocopherol. The obtained results may be useful in designing a new type of fried food with improved health properties and it may be the basis for further research on this topic.

Effects of structural characteristics of phenolic compounds on oxidation of glycerol trioleate: Action rule and mechanism

Effects of structural characteristics of phenolic compounds on the oxidation of glycerol trioleate were investigated, and the action rule and mechanism were further explored. By using thermal and multispectral analyses, all tested phenolic compounds significantly inhibited the oxidation of glycerol trioleate, and reduced the decomposition of CC and ester bonds of glycerol trioleate, which were attributed to their capability to inhibit the production of free radicals. Quercetin and gallic acid were the most effective among the condensed and hydrolyzable phenolic compounds in present study, respectively. For condensed phenolic compounds, the hydroxyl groups in B ring, substitution in C ring, and the structure of C ring played a crucial role in their inhibitory action. For hydrolyzable phenolic compounds, the amount of hydroxyl groups and their molecular weight had obvious effects on their inhibitory action. According to the measurement of molecular electrostatic potential and frontier molecular orbitals by density functional theory, the large maximum electrostatic potential and the small energy gap value were beneficial to enhance the inhibitory capability of phenolic compounds on the oxidation of glycerol trioleate. All present results suggested the potential action rule and molecular mechanism about the inhibitory effects of phenolic compounds on the oxidation of glycerol trioleate.