A New Insight into the Evaluation of Used Frying Oils Based on the Kinetics of Chemical Changes during the Process

Kinetics of change in total polar compounds (TPC), carbonyl value (CV), and conjugated diene value (CDV) were simultaneously investigated during the frying of potato strips in eight oil samples at 170 °C. The CDV at the turning point of the sigmoidal kinetic curves (CDV_T) with an average of ~19 mmol/L, which was almost equivalent to the TPC and CV of ~14% and ~24 μmol/g, respectively, was found to be as a sensory cut-off value for rejection. To discard frying oils from a toxicological standpoint, the CDV at the mean of the times required to reach the CDV_T and the CDV_max with an average of ~28 mmol/L (almost equivalent to the TPC and CV of ~22% and ~41 μmol/g, respectively) was determined as the corresponding cut-off value.

Effect of phenolic extracts from Camellia oleifera seed cake on the formation of polar compounds, core aldehydes, and monoepoxy oleic acids during deep-fat frying

The frying process is an excellent way to obtain food with desirable sensory. However, some harmful substances, such as aldehydes and monoepoxy oleic acids, could also be produced. This study mainly explores the inhibition of polyphenols from the Camellia oleifera seed cake extract (CSCE) on the formation of polar compounds, core aldehydes, and monoepoxy oleic acids during deep-fat frying. The results showed that the CSCE could significantly decrease peroxide, p-anisidine, total polar, and monoepoxy oleic acids compared with other groups. In addition, the CSCE could significantly inhibit the generation of oxidized triacylglycerol polymer (TGP) and oxidized triacylglycerol (ox-TG), indicating its anti-polymerization activity. The total amount of core aldehydes and glycerol ester core aldehydes (9-oxo) in soybean oil was significantly reduced. Furthermore, CSCE had a better inhibitory effect on monoepoxy fatty acids than TBHQ. Our results might be helpful to provide a basis for the search for new natural antioxidants.

Potential of using basa catfish oil as a promising alternative deep-frying medium: A thermo-oxidative stability study

Basa catfish is a good source for fish oil extraction, which was believed to have good thermo-oxidative stability because of its similar fatty acid composition to that of palm olein (PO). The thermo-oxidative stability of PO, basa catfish oil (FO), and palm olein-basa fish oil blend (PO-FO; ratio 1:1) was evaluated after 75 frying cycles. No significant difference was observed in p-anisidine value, TOTOX value, conjugated trienes, monomeric oxidized triacylglycerols, and free fatty acids concentration after frying. Moreover, compared to PO, FO exhibited lighter color, lower acid value, conjugated dienes, polymerized triacylglycerol, and total polar content. The PO-FO blend also demonstrated a more favorable frying stability compared to the other two frying systems. These findings indicated that FO could be proposed as a promising alternative to common PO, and its blending with other vegetable oils at an appropriate ratio might improve the overall oil frying quality for future industrial applications.

Effect of Anti-Clouding Agent on the Fate of 3-Monochloropropane-1,2-Diol Esters and Glycidyl Esters in Palm Olein during Repeated Frying

Issues on 3-monochloropropane-diol-1,2-diol (MCPD) esters and glycidyl esters in refined oil have gained much attention when these heat-induced contaminants are associated with health implications. Oil that undergoes the frying process could influence the fates of 3-MCPD esters and glycidyl esters, especially with the addition of an anti-clouding agent. In this study, we investigated the effect of polyglycerol fatty acid esters (PGE) on the transients of 3-MCPD esters and glycidyl esters in palm olein (POo) during intermittent frying. Thermal resistance of POo fortified with PGE (0.1% to 0.4%) was assessed for 8 h of daily frying operations at 180 °C across five consecutive days. The addition of PGE decelerated the reduction of 3-MCPD esters and glycidyl esters with the progression of frying. The presence of these compounds coincided with the amount of oil taken up by the fried product. The inclusion of PGE in POo also induced higher augmentation of polar compound fractions, i.e., oxidised triacylglycerols (OxTAG) and polymerised triacylglycerols (PTAG), but gave comparable free fatty acid (FFA), p-anisidine value (AnV), total chloride and fatty acid composition (FAC) with control oil (POo). The results also showed that the presence of chloride in POo did not onset further formation of 3-MCPD esters and glycidyl esters throughout the frying period. As the behaviours of 3-MCPD esters and glycidyl esters were affected by PGE, only a sufficient amount should be added into POo to ensure oil clarity at a realistic period.

Oxidative stability of canola oil by Biarum bovei bioactive components during storage at ambient temperature

In this study, antioxidative activities of aqueous extract of Biarum bovei (BBE) in stabilizing of canola oil during storage at 20°C was evaluated. For this purpose, the total phenolic (TP), flavonoids (TFC), and tocopherol content (TTC) of the extract were determined and β-carotene bleaching system was used to assess the antioxidant efficacy of BBE. The amount of TP, TFC, and TTC in BBE indicated high antioxidant activity. So, different concentrations (0, 200, 800, and 1400 ppm) of BBE and butylatedhydroxyanisole (BHA; 100 ppm), were added to canola oil for 60 days at 20°C. Peroxide value (PV), carbonyl value (CV), Total polar compounds (TPC), acid value (AV), iodine values (IV), and conjugated dienes (CD) were employed to evaluate the BBE effect on canola oil stabilizing. Results indicated that 1,400 ppm of BBE exhibited stronger antioxidant activity in canola oil than BHA.