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A novel compound, 6,6'-(butane-1,1-diyl)bis(4-methylbenzene-1,2-diol) (BMB), was synthesized through an acid-catalyzed condensation reaction between 4-methylcatechol (HPC) and butyraldehyde. When evaluated by the Rancimat and deep frying methods, BMB exhibited a stronger antioxidant activity than TBHQ. Its DPPH radical scavenging activity was also fairly higher than TBHQ, but lower compared to its mother phenol, HPC, due to its relative ease of binding DPPH•. BMB had the strongest scavenging ability of the 4-methylcatechol analogues reported to date. It could be used effectively to retard lipid peroxidation in both moderate and high temperature food preparations.

The action of antioxidants to delay lipid oxidation in fats and oils is well known although most of the information is related to their effects at room temperature during storage or at the moderate temperatures of the accelerated tests to measure oil stability. However, oxidation at the high temperatures of food processes like frying, is more complex because the availability of air is unknown and both oxidative and thermal reactions are simultaneously involved. In this review, the main studies defining the action of natural and synthetic antioxidants at frying temperatures are summarized. This review has been divided into two main parts concerning the information on natural antioxidants, i.e. tocopherols and other phenolic compounds present in specific oils like olive, sesame and rice bran oils, and on synthetic antioxidants, i.e. BHA, BHT and TBHQ.

Sunflower oil is one of the vegetable oils most susceptible to oxidative reaction. Therefore the presence of natural (tocopherol) and/or synthetic (TBHQ) antioxidants is a prerequisite to secure the stability of this oil during its shelf life, especially with the increased use of PET packaging. On determining the total tocopherol content in 10 samples of deodorized sunflower oils, high losses in total tocopherol during deodorization were identified. In order to facilitate researche involving oxidative stability of vegetable oils, a method for isolated quantification of TBHQ using the isocratic elution system was developed.

Two novel compounds bearing four hydroxyphenyl groups were synthesized by the acid-catalyzed condensation reaction of glyoxal with toluhydroquinone (THQ) or tertiary butylhydroquinone (TBHQ), respectively. The antioxidant activity of the newly synthesized compounds was assessed by the Rancimat test, a 2,2-diphenyl 1-picrylhydrazyl (DPPH) assay and reducing power assay. In the Rancimat antioxidant test using lard oil as substrate, the performance of two newly synthesized compounds was superior to TBHQ at 140 °C. It was suggested that two newly synthesized compounds can be used to improve the oxidative stability of lipid products during high temperature processing. With regard to the DPPH radical scavenging activity and reducing power, the performance of synthesized compounds was inferior to their mother compounds, respectively. The results show that the DPPH radical scavenging activity and reducing power of a compound did not correlate with its ability to retard lipid oxidation.