Validity of total polar compound and its three components in monitoring the evolution of epoxy fatty acids in frying oil: Fast food restaurant conditions.

This study evaluated the validity of total polar compounds (TPC) and its three components in monitoring the evolution of epoxy fatty acids in frying oil under fast food restaurant conditions. The content of epoxy fatty acids can be predicted using the TPC rather than oxidized triglyceride monomer. When TPC content reached 24 g/100 g, 25 g/100 g, and 27 g/100 g, the epoxy fatty acid content in oil was found to be 1.47-3.63 mg/g, 1.58-4.06 mg/g, and 1.83-5.08 mg/g, respectively. More epoxy fatty acids were generated in high oleic sunflower oil than in canola and cottonseed oil during frying. At current discarding points of TPC 24-27 g/100 g, its epoxy fatty acid content was 3.63-5.08 mg/g, which was lower than the limit of 7 mg/g recommended by Max Rubner-Institut in Germany. Our results indicate that the risk of epoxy fatty acids can be monitored using the current TPC index.

2,3,7,8-Tetrachlorodibenzo-p-dioxin induces liver lipid metabolism disorder via the ROS/AMPK/CD36 signaling pathway.

2,3,7,8-Tetrachlorodibenzo-p-dioxin (TCDD) is widely considered as the most toxic and common carcinogen in the world. Exposure to TCDD causes liver lipid metabolism disorder and steatosis. However, the molecular mechanism of TCDD-induced liver lipid accumulation is not completely clear. Here, we found that a 5 µg/kg TCDD exposure for 3 weeks induced hepatocyte lipid deposition, increased CD36 expression, and promoted AMP-activated protein kinase (AMPK) ɑ phosphorylation in the liver of C57BL/6J mice. Furthermore, sulfo-N-succinimidyl oleate, a CD36 inhibiter, blunted TCDD-induced lipid deposition in Huh7 cells, confirming the critical role of CD36 in TCDD-induced hepatic steatosis. In terms of molecular mechanisms, we found that TCDD exposure increased reactive oxygen species (ROS) levels in Huh7 cells, which activated AMPK. Moreover, the activated AMPK upregulated CD36 expression. Therefore, we can see that the increase in CD36 expression induced by TCDD was regulated by ROS/AMPK/CD36 signaling pathway. Our results help to clarify the molecular mechanism of TCDD-induced hepatic steatosis.

Investigation of oxidized triglyceride monomer (oxTGM) produced in deteriorated soybean oil at frying temperatures: A kinetic study.

This work evaluated the feasibility of total polar compound (TPC) and its five components to monitor the deterioration of soybean oil at frying temperatures, and traditional indicators were used as a reference. The preliminary correlation analysis showed that polar compounds accumulated earlier than classical oxidation products like the peroxide value (PV). Equations for two types of characteristic kinetic time, the induction time (turning point of sigmoid curve) and intersection time (intersection point of two tangent lines representing the initiation and propagation reaction), were also derived. Their mathematical difference and relationship were then evaluated. Based on the kinetic analysis, the overall cumulative process of oxidation products of triglycerides (oxTGM) was found to be 2.35%-12.35% earlier than that of fatty acids (PV). Our results supported the index of oxTGM in TPC to be a better indicator to monitor the deterioration of heated edible oil.

LF-NMR intelligent evaluation for lipid oxidation indices of polar compound distribution, fatty acid unsaturation, and dynamic viscosity: Preference and mechanism.

The Low Field Nuclear Magnetic Resonance (LF-NMR) intelligent analysis for lipid oxidation indices of polar compound distribution, fatty acid unsaturation, and dynamic viscosity was established and compared. LF-NMR curves obtained from the multivariate approach were more suitable for the establishment of prediction models. Results proved the ability of LF-NMR for the aging evaluation of edible oil, but different prediction performance was found for various indices. The order from the good to bad prediction was: fatty acid unsaturation > polar compound > dynamic viscosity. It demonstrated the preference of LF-NMR for reporting the information of fatty acid than triglyceride in oxidized oil. Two mechanisms for the LF-NMR method were summarized and expressed by equations. Results also supported that the peak 21 in the LF-NMR curve provided unique information about polar and low-molecular-weight products rather than polymer compounds. Data were expected for a better understanding of LF-NMR signals and to accelerate its wide application in the food industry.