In this study, binary blends of palm stearin and soybean oil were interesterified using sodium methoxide. The changes in free fatty acids (FFA), slip melting point (SMP), solid fat content (SFC), plastic range, induction period of oxidation at 120 8C (IP 120 ) and rheological properties of fat blends, before and after interesterification, were investigated. All blends were trans-free and contained high essential fatty acids content. Interesterification modified the melting properties of fat blends by reducing SMP and SFC. FFA increased and IP 120 decreased after interesterification. Strain sweep, frequency sweep and temperature sweep tests were used to evaluate the rheology of fats. Briefly, the 10:90 and 30:70 (palm stearin : soybean oil) interesterified blends displayed increased storage (G 0 ) and loss (G 00 ) moduli, as compared with the initial blends. However, G 0 and G 00 moduli of interesterified 50:50 blend were lower than those of initial blends. The elastic character of interesterified 10:90, 30:70 and 50:50 blends was predominant up to 28.8, 37.9, and 41.8 8C, respectively. The interesterified blends of palm stearin and soybean oil showed desirable characteristics suited for production of trans-free soft tub, stick and Baker's margarine, all-purpose shortening and Iranian vanaspati. PRACTICAL APPLICATIONSIntake of high amounts of trans fatty acid (TFA) has been correlated with increased risk of heart diseases. In this context, chemical interesterification is an important technological option for production of trans-free fats with different food applications. The results obtained here provide information about the scientific aspects of the effect of interesterification on rheological and physicochemical properties of palm stearin and soybean oil blends. Practically, this study can find its application in development of formulations for production of trans-free fat products such as liquid, soft tub, stick and baker's margarine, allpurpose shortenings and Iranian vanaspati.

In this study, postmarketing surveillance (PMS) was conducted in terms of the parameters which are reliable indicators of the oxidative stability of cooking oils, frying oils, and vanaspati samples. The analyzed parameters were fatty acid composition, peroxide value (PV), free fatty acids (FFA), p‐anisidine value (p‐AV), induction period at 110°C (IP 110 ) determined by Rancimat test, and TOTOX value. For this purpose, different samples from four highly popular brands of mentioned products were randomly collected from Iran's market during 2016–2018. All monitored products had trans fatty acid <1.0%. In the case of FFA and IP 110 , the ranges of 0.03–0.08 (%) and 9.3–17.2 hr were obtained, respectively, being mostly in conformity with the National Standard of Iran (FFA < 0.1% and IP 110 > 15 hr). The ranges of PV of cooking oils, frying oils, and vanaspati samples were 1.2–2.7, 0.93–2, and 0.84–1.6 meq/kg, respectively. Our results revealed that p‐AV of frying oils and cooking oils was mostly outside of legal limits of Iran (p‐AV > 6) with the ranges of 4.2–12.5 and 4.3–12.3, respectively. In terms of TOTOX value, monitored products had a range from 5.2 to 13.0 (mostly <10) being nearly acceptable.

In this study, production of trans‐free fats through chemical interesterification of binary blends of palm stearin (PS) and sunflower oil (SFO) and their physicochemical changes after the process was investigated. Analyzed responses included fatty acid and triacylglycerol composition, iodine value, free fatty acid (FFA), soap content, peroxide value (PV), plastic range, slip melting point (SMP), solid fat content (SFC), and oxidative stability along with potential applications of the interesterified fats. Transfatty acid content of PS/SFO blends was lower than 0.36%. Chemical interesterification increased the FFA and soap content and also decreased PV and oxidative stability index (at 110°C). After the process, SMP and SFC were reduced, also the plastic range transferred to the lower temperatures. All the interesterified blends melted completely at the body temperature, and their SFC was <32%. The melting characteristics of the PS/SFO‐interesterified blends were suitable for many fat‐based products.

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This research was set up to identify the impact of the antioxidant compounds present in lemon balm extract (LBE) as obtained by the subcritical water (SBCW) method on the oxidative stability of corn oil. An extraction yield of 28.52% was obtained for the SBCW and rosmarinic acid was identified to be the predominant phenolic compound present in the LBE. The total phenolic content of the LBE was found to be 212.74 mg gallic acid/g extract. Subsequently, 200, 400, 800, 1600 and 3200 ppm of the LBE were added to corn oil and its peroxide value (PV), acid value (AV), conjugated diene (CD), carbonyl value (CV), oxidative stability index (OSI), total polar compound and total phenolic compounds were compared to control and the sample containing 200 ppm of the BHA throughout the 16-day Schaal oven test at 70°C. Our findings indicated that the corn oil containing greater LBE concentration had lower PV, AV, CD, and CV but greater OSI than the control sample. Evaluation of total polar compounds confirmed lower extent of the compounds with high polarity in the greater levels of the LBE. Finally, the LBE was able to slow down the rancidity of corn oil and the samples with higher LBE exhibited gentle oxidation rate.