ABSTRACT
The effect of added menadione (vit. K3) to stored rapeseed and soybean oil on the dissolution and dimerization of natural tocopherols and autoxidation of triacylglycerols was studied. Commercial rapeseed and soybean oils with added menadione and pure oil were stored at +20 degrees C in brown and transparent glass bottles. During storage their peroxide value, changes of the content of fatty acids and dissolution of tocopherols were measured. Destruction of individual tocopherols in tested oils with added menadione stored in both dark and transparent glass bottles were greater than in the oil samples without menadione. However, the degradation of individual tocopherols was different in each oil. Addition of menadione to the rapeseed and soybean oils resulted in the accelerated process of autoxidation of these oils. The oxidative state of the oils was lower in the oils stored in transparent bottles than in the oils stored in brown bottles. The prooxidant activity of menadione was additionally activated by light. Menadione added to the vegetable oils influenced the dissolution of natural tocopherols as well as their dimerization. It is conduced that addition of menadione to vegetable oils decreases their nutritive value.
Subject(s)
Food Handling , Plant Oils/metabolism , Triglycerides/metabolism , Vitamin E/metabolism , Vitamin K/administration & dosage , Antioxidants/administration & dosage , Antioxidants/pharmacokinetics , Chemical Phenomena , Chemistry, Physical , Dimerization , Fatty Acids/analysis , Fatty Acids, Monounsaturated , Food Preservation/standards , Light , Nutritive Value , Oxidation-Reduction , Rapeseed Oil , Soybean Oil/metabolism , Temperature , Time Factors , Vitamin K/pharmacokineticsABSTRACT
Changes occurring in margarine stored at 4 and 20 degrees C were studied during the guarantee period declared by the producer (136 days). Fatty acid composition of triacylglycerols, homologous tocopherols, energetic value, peroxide value and water content were determined. It was stated that the composition of fatty acids and percentage of essential fatty acids (EFA) did not change significantly by time until the peroxide value reached the standard (4 mmol O2/kg). With peroxide values up to 5.5 considerable decomposition of tocopherols took place: alpha-tocopherol 50%, gamma-tocopherol 47% and delta-tocopherol 37%. The vitamin E content (34 i.u.), the EFA content (23%) and their physiological advantageous mutual relationship (Harris coefficient 1.44), which undergo slight changes during storage at 4 degrees C for the guarantee period, allowed to consider the studied margarine as a nutritionally valuable foodstuff. However, during storage at 20 degrees C, when the oxidation is accelerated, the margarine quickly loses its nutritive value. The energetic value of the margarine was lower than that of the products defined as margarine (more than 80% of fat, about 3200 kJ), and it amounted to 3029 kJ. It slightly decreased during storage of the margarine.
