Study On Stability Of Vitamin D In Infant Formulas

Vitamin D is an important kind of fat-vitamin,which plays a vital role on the development of the human skeleton, the absorption of nutritive elements and the prevention of rickets.The concentration limits of vitamin D in infants formula milk powder are established by laws, the dertermination of vitamin D is also required as one of the routine testing projects for infants formula milk powder. However,during the production, processing and storage procedures at different temperatures, humidities,as well as after interactions with metal ions,there will be some degree of vitamin D degradation in infants formula milk powder,leading to a negative impact on the product quality.The vitamin D in infant formula milk powder was chosen as the research subject in this paper.Firstly,the determining method of vitamin D in infant formula milk powderwas optimizated while the saponification step in the national standard methods was simplified.The infant formula milk powder samples were analysed by the ultra high-performance liquid chromatography after the low temperature saponification together with lipase and extraction.This method can be used for the determination of vitamin D in infant formula milk powder of all sections and the results proved the method to be simple,fast and accurate.The stability of vitamin D in infant forula milk powder of different raw material formula, different storage and different production processes were studied in this paper, while the degradation kinetics model of vitamin D in infant formula milk powder during the storage was established at the same time.This research summarized the fluctuations of vitamin D concentrations in infant formula milk powder and analysised the light, temperature, moisture, pH, metal ions and other factors on the stability changes of vitamin D.The study reached the conclusions on the following aspects:(1) This paper optimized the determination method of vitamin D in infant formula milk powder. Infant formula milk powder was extracted by petroleum ether after saponification together with lipase、ascorbic acid-ethanol solution and KOH solution at a low temperature. The residue was dissolved in methanol and finally injected into the UPLC system after the extraction solution was evaporated to dry under a rotary evaporator.The linear range of this method were between0.2-10mg/L,while the detection limit of cholecalciferol was0.2μg/100g and the average spike recoveries range were93.4%-96.5%. This method demonstrated to be simple with high recovery and precision.(2) This paper studied the stability of vitamin D by changing the light、temperature、 metal ions、pH and other factors.The results showed that the pH and temperature conditions had a relatively lower influence on the stability of vitamin D than the light and metal ions did.The corresponding loss rates were76.4%(light),83.8%(temperature),75%(pH),the loss rates for antioxidants and metal ions were less than5%.The degradation of vitamin D obeyed the first order kinetics and the activity energy were80.54kJ·mol-1(3) The stability changes of vitamin D during the in infant formula milk powder prodution process were summarized in this paper.The homogeneous、sterilization and spray drying process were simulated while the concentrations of vitamin D were determined at the same time.The spray drying process made the most obvious negative impacts on the vitamin D stability and the loss increased to69.0%。The sterilization process had a relatively lower damage effect(15%of loss rates) but were strongly influenced by the temperature(60s for20.5%loss rates).(4) Further more,the vitamin D concentration losses in different storage conditions were studied. According to the vitamin D concentration dates of different temperatures、 packaging materials、air and lights,light was the main factor which caused the vitaminD degradation(loss rate71%),while air and the temperature were relatively less important factors(40.3%).Different packaging materials showed different degrees of influence.For the unpacked infant formula milk powder products,the storage conditions should be at low temperatures、dry air conditions with little light.The products should also be comsumpted in time.