Quality of repeatedly heated oil: Modeling of vitamins degradation kinetics and in vivo deleterious health effects

Vegetable oil has been used by several countries, including Oman, as a vehicle for fat-soluble vitamins in food fortification strategies. According to the Ministry of Health, a group of population is suffering from deficiency of vitamins A and D. The Ministry of Commerce and Industries issued a mandatory regulation to fortify vegetable oils with those vitamins as an intervention strategy. One of the major uses of vegetable oils is deep-fat frying. The process product food with unique organoleptic properties. However, chemical changes that take place affect the quality of the frying oil. Polymerization, hydrolysis and oxidation take place during frying result in the formation of chemical substances that are believed to be toxic for human being. Vegetable oils are fortified with fat-soluble vitamins as part of intervention strategies to resolve deficiencies issues. However, the stability of those vitamins is questionable and consequently the success of the intervention. Several factors affect the stability of oil under frying and hence the stability of the vitamins. Factors include the types of oil, frying temperature, presence of antioxidants and the food being fried. Hence, the stability of added vitamins will vary according to the variation in the above-mentioned factors. In this project, different types of oils will be fortified with vitamins A and D because of national concerns. The oil will be used in intermittent deep-fat frying for 7 hours per day for 5 days. Oil and food samples will be collected at the end of each day. When oil replenishment is applied, oil samples will be taken after addition of the top-up oil. The content of vitamin A and D will be analyzed by HPLC. Acid, peroxide and p-anisidine values will be also assessed to monitor the oil quality. The oil will also be assessed for its antioxidant capacity. Models will be developed to describe the degradation kinetics of vitamins including different factors. In vivo experiment will be done using Sprague-Dawley rats. Rats will be fed either a control diet, the oil sampled from the fryer or the food samples from the frying process for 8 weeks. At the end of the experimental study, blood samples will be collected from the posterior vena cava, and the animals. Total protein content of liver tissue, serum lipids profile and liver enzymes will be measured. The project is expected to give a clear idea about the stability of vitamins A and D under intermittent deep-fat frying. Models that will be developed will help understanding the relationship between vitamins degradation and frying process parameters such as oil antioxidant capacity, frying temperature and time. This will help determining the proper initial concentrations of vitamins to be added in fortification strategies and the outcome of the strategies. In vivo study will help understanding the effect of the matrix of oil including the added vitamins and the inherited antioxidants on the experimental animals.