Ziziphi s pinosae Semen Oil Enhance the Oxidative Stability of Soybean Oil under Frying Conditions

Effect of Natural Antioxidants from Fruit Leaves on the Oxidative Stability of Soybean Oil during Accelerated Storage

Plant by-products are safe, sustainable, and abundant natural antioxidant sources. Here we investigated the antioxidant activity of a mixture of lyophilized pomegranate, guava, and grape (PGG) leaves water extract (1:1:1) and examined its ability to retard the rancidity of soybean oil during accelerated storage at 65 °C for 30 days. To achieve this, we evaluated the oxidative stability of soybean oil enriched with PGG extract at 200, 400, and 800 ppm. We also compared the effect of PGG extract with butylated hydroxytoluene (BHT) (400/100 ppm) with that of only BHT (200 ppm). We observed that 8.19 and 1.78 µg/mL of the extract could scavenge 50% of DPPH• and ABTS•, respectively, indicating its enhanced antioxidant activity. Enriching soyabean oil with the extract at 800 ppm improved its oxidative stability by reducing the acid value to 1.71 mg/g and the total oxidation to 99.87 compared to 2.27 mg/g and 150.32 in the raw oil, respectively. Moreover, PGG-800 ppm inhibited oxidation by 46.07%. Similarly, PGG-400 ppm reinforced BHT (100 ppm) to provide oxidative stability as BHT (p > 0.05), with TOTOX values of 87.93 and 79.23, respectively. PGG-800 ppm and PGG/BHT mix potently inhibited the transformation of polyunsaturated fatty acids into saturated ones. Therefore, the PGG extract might be an efficient substitute for BHT (partially or totally) during industrial processes.

Separated from the Essential Oil of Coriandrum sativum L. Leaves, Carvacrol and Limonene Showed Antioxidant Effects in Sunflower Oil under Frying Conditions

The frying process, a popular cooking technique, is widely used in the food industry around the world for the production of fried foods. Nevertheless, it is always accompanied by potential challenges including lipid peroxidation of vegetable oils. In this study, the influence of the coriander leaves essential oil (CLEO) on the oxidative stability of sunflower oil under frying conditions and the sensory attributes of fried food (Chinese Mahua) during the sensory evaluation were investigated. The results indicated that compared with the control, CLEO at 0.12 g/kg could obviously suppress the increases for the total polar compounds (TPC), thiobarbituric acid (TBA), color, conjugated dienes (CD), conjugated trienes (CT) and viscosity of sunflower oil, and prominently restrain the oxidization procedure of unsaturated fatty acid (UFA). Meanwhile, the decline in the sensory attributes for the Chinese Mahua was significantly inhibited. Furthermore, the study revealed the antioxidant effect of CLEO was mainly attributed to two compounds, carvacrol and limonene, which were separated by the bioassay-guided fractionation. Consequently, CLEO and the two compounds may be employed as potential natural antioxidants to improve the oxidation stability of sunflower oil under frying conditions.

Oil bodies extracted from high-oil soybeans (Glycine max) exhibited higher oxidative and physical stability than oil bodies from high-protein soybeans

Reports concerning the characteristics of soybean oil bodies (SOBs) isolated from high protein genotypes and high oil genotypes of soybeans available in the literature are insufficient and limiting. In this study, fatty acid compositions, total phenol and tocopherol contents, antioxidant capacity, and physicochemical stability of SOB emulsions recovered from three high-protein and three high-oil genotype soybeans were comparatively investigated. Principal component analysis showed that all six SOB samples could be easily discriminated based on the cultivar characteristics. Overall, the SOBs derived from the high-protein soybeans exhibited higher polyunsaturated fatty acid (PUFA) contents, while the SOBs derived from the high-oil soybeans had higher extraction yields and tocopherol contents; the tocopherol content was also positively correlated with the antioxidant capacity of the lipophilic fraction, but the difference in the total phenolic content between the two genotypes was not significant. The SOBs derived from the high-protein soybeans were more easily oxidized during storage, with 1.38- and 4-fold higher accumulation rates of lipid hydroperoxides (LPO) and thiobarbituric acid reactive substances (TBARS), respectively, in the high-protein-derived SOBs than in the high-oil-derived SOBs. In addition, the SOBs from the high-protein soybeans exhibited pronounced coalescence during storage, which was corroborated by focused confocal microscopy. These results confirmed that SOBs obtained from high-oil soybean genotypes are more suitable to manufacture OB-based products due to their superior physicochemical stability.