Synthesis of 7-hydroperoxycholesterol and its separation, identification, and quantification in cholesterol heated model systems

Microwave assisted direct saponification for the simultaneous determination of cholesterol and cholesterol oxides in shrimp

A novel microwave-assisted direct saponification method for the simultaneous determination of cholesterol and cholesterol oxides in shrimp was developed and validated. Optimal saponification conditions, determined by means of an experimental design, were achieved using 500mg of sample and 20mL of 1mol/L KOH ethanol solution for 16min at 45°C at maximum power at 200W and magnetic stirring at 120rpm. Higher extraction of cholesterol oxides in a reduced saponification time (∼75 times) was achieved in comparison with the direct cold saponification method. The new method showed low detection (≤0.57μg/mL) and quantification (≤1.73μg/mL) limits, good repeatability (≤10.50% intraday and ≤8.56% interday) and low artifact formation (evaluated by using a deuterated cholesterol-D6 standard). Raw, salted and dried-salted shrimps were successfully analyzed by the validated method. The content of cholesterol oxides increased after salting and decreased after drying.

Influence of salt on lipid oxidation in meat and seafood products: A review

Sodium chloride, commonly known as salt, is a widely used additive in food industry due to its preservation and antimicrobial properties provided by its ability to reduce water activity. Moreover, the addition of salt to meat and seafood aims at improving water retention capacity and enhancing flavor due to its influence on the activity of some enzymes responsible for flavor development. On the other hand, salt added in meat and seafood can favor lipid oxidation, which is one of the main responsibles for quality losses in the food industry. In this review, the main mechanisms of fatty acids and cholesterol oxidation are described as well as the influence of salt on lipid oxidation in meat and seafood. Besides, the possible mechanisms of the pro-oxidant action of sodium chloride are presented and potential solutions to inhibit the salt action in lipid oxidation and decrease the salt content in food are discussed.

Recent advances in cholesterol chemistry

This review article presents advances in cholesterol chemistry since 2000. Various transformations (chemical, enzymatic, electrochemical, etc.) of cholesterol are presented. A special emphasis is given to cholesterol oxidation reactions, but also substitution of the 3β-hydroxyl group, addition to the C5-C6 double bond, C-H functionalization, and C-C bond forming reactions are discussed.

Inhibitory activities of some vitamins on the formation of cholesterol oxidation products in beef patties

The capacities of 15 vitamins to inhibit the formation of 7α-hydroxycholesterol, 7β-hydroxycholesterol, and 7-ketocholesterol were examined in beef patties. Their inhibitory activities were tested at a concentration of 0.4 mmol in 30 g of beef. Among them, L-ascorbic acid, retinoic acid, and α-(±)-tocopherol were found to exert a potent inhibitory effect (30-50%) on 7-ketocholesterol formation and (~20%) on 7α-hydroxycholesterol and 7β-hydroxycholesterol formations. Pyridoxamine inhibited 7-ketocholesterol formation by 60% with a statistically significant difference (p < 0.05) from that achieved in the control setup. To further elucidate the possible inhibitory mechanism of pyridoxamine against cholesterol oxidation, a chemical model with pyridoxamine added in the cholesterol oxidation system (heated at 140 °C for 240 min in dimethyl sulfoxide) was employed. It was demonstrated that pyridoxamine could directly react with 7-ketocholesterol via the addition reaction. The reaction involved a nucleophilic attack of the free amine group of pyridoxamine on 7-ketocholesterol (an α,β-unsaturated carbonyl compound). This type of reaction was also found to occur in beef patties by chromatographic and spectral analyses.

Formation and inhibition of cholesterol oxidation products during marinating of pig feet

Cholesterol oxidation products (COPs), formed during the heating of cholesterol-rich foods, have been shown to cause cancer and coronary heart disease. The objectives of this study were to develop a GC-MS method for the determination of COPs in pig feet meat, skin, and juice during marinating and to study the formation and inhibition of COPs as affected by the incorporation of soy sauce and sugar. Results showed that an HP-5MS column could provide an adequate separation of cholesterol, 5α-cholestane (internal standard), and seven COPs, including 7α-OH, 7β-OH, 5,6β-OH, 5,6α-OH, triol, 25-OH, and 7-keto, within 15 min with a temperature-programming method. Most COPs in pig feet meat were generated at a larger amount than in pig feet skin and marinating juice over a 24 h heating period at about 100 °C. The Maillard browning index rose with increasing heating time, whereas the pH showed a slight change in marinated juice. Both reducing sugar and free amino acid contributed to the formation of Maillard reaction products. The incorporation of soy sauce and crystal sugar into fresh juice was effective in inhibiting COPs formation in pig feet, skin, and juice over a 30 min preheating period.