Optimization Of Determination Method Of Carotene In Foods And The Effect On Dietary Intake Assessment

Objective Vitamin A (VA) deficiency is an universal problem in our country, and carotene is the main dietary source in China and other developing countries. Given the limitations of current analysis and calculation methods, most of data are in form of total carotenoids that not separating the various components and geometric isomers of carotenoids. What’s more, there is another problem of extraction for the carotene from the plant foods. These above problems would bring influence to the evaluation of dietary intakes. So this study aims to:1.In order to distinguish a-carotene and β-carotene effectively, optimizating the chromatographic conditions and extraction method to establish the determination method with high efficiency and accuracy; 2.Determinating the common plant foods of high consumption using the new method, and analyzing the content of carotene in foods; 3.Based on the above new data of carotene content in foods, calculating the carotene intakes of Beijing residents, and comparing with intake data based on food composition databases(FCD) in 2002, to explore the influence of method improvement to dietary intakes.Methods 1.Establishment of determination method:Optimizing high performance liquid chromatographic analysis condition by groping the ratio of mobile phase and establishing the methods of qualitative and quantitative for isomers. Selecting the best the extraction method with respecting to three extraction conditions such as leach liquor, temperature and time with the sample of carrots and spinach.2. Randomly selecting the supermarkets and markets of huge flow in Beijing, and collecting common plant foods of high consumption, such as vegetables、fruits and so on, and at the same time collecting the same vegetables from the different regions,then using the established method to determinate the carotene and make the evaluations.3.Comparing the new data with the FCD of 2002 with the method of paired test. Adjusting (replaceing or adding) the data of FCD with the new measurement data, and based on the dietary consumption data of Beijing residents in China health and nutrition survey (CHNS) in 2011, calculating the carotene intakes and RE from the plant foods with the data before and after adjustment, and making the comparision.Results According to the establishment of analysis method> the carotene determination of common plant foods, as well as to the human intakes based on the above data,drawing the following results:1. Establishment of determination methodThe method throughout the experiment exhibited a significant benefit for the separation of carotene and isomers. Multifactor analysis of variance showed that heating by the anhydrous ethyl alcohol before the saponification was more suitable for extracting the carotene from plant foods. Under the optimal condition, the linear range of α-carotene was 0.495-9.90μg/ml, and all-trans-β-carotene was 0.552-10.4μg/mL, with the linear correlation coefficient were above 0.999. The relative standard deviation for the alpha and beta carotene were less than 9%.The average spike recoveries for a-and β-carotene were 80.7%-98.5%. The detection and quantification limits were 0.5μg/100g and 1.5μg/100g, respectively, when taking 5g samples.2. The description and analysis of carotene content in plant foods2.1 General descriptionThis study involved 136 kinds of plant foods, in which 58 kinds of vegetables、44 of fruits、3 of potato foods、8 of thallogen、5 dry beans,10 grains, and 8 kinds of nuts and seeds. At the same time, the vegetables from different regions were tested.On the overall, there were obvious differences between different types. Carrots、 green leafy vegetables、fruits, and somet of the thallogen were the main food sources of natural carotene. In vegetables, carotene in carrots and leaf vegetables were relatively abundant, and mango、cantaloupe were the fruits of high content.2.2 The analysis ofa-carotene content in foodsThe a-carotene content in the plant foods were low, and carrots were its main source. And it also showed that the RE would be overestimated if the α-carotene wasn’t distinguished.2.3 The factors of carotene content in plant foodsCarotene content in plant foods of different varieties:In this study, the carotene content of mango, pepper, kiwi and muskmelon of different varieties had significant statistical difference (P<0.001). But amaranth (red/green), fresh beans, apples, grapes (purple/green), grapefruit (red/yellow), watermelon didn’t show significant statistical difference between the varieties (P>0.05).The differences of carotene content between regions:The carotene content in carrots、pak choi、chinese cabbage、pumpkin, cucumber, chinese chive and kidney bean collected in this study showed the regional differences (P<0.05), which were various in different vegetables. And the carotene content in spinach, cabbage, eggplant, chilli and tomato had no regional differences (P>0.05). On the whole, vegetables growed in the northwest regions had higher carotene content.2.4 The carotene content of foods in different colors:It showed that there had the obvious difference between the foods in different colors (P<0.001). And the foods with high content mainly involved green and yellow foods, the nori was also abundant in black foods.3. The influence of method improvement to food composition data and dietary intakeComparing with food composition data of 2002, it showed the downward trend. To the dietary intake, it could led the carotene intakes and retinol equivalent level to decrease about 10%, and the influence of determinating alpha carotene to dietary intakes was about 0.9%.Conclusion1. According to exploring the effective separation technique、quantitative analysis and efficient extraction technology for the determination of carotene and isomers, the new method was of higher accuracy and reliability.2. Natural carotene mainly exist in the carrots、the leafy vegetables and fruits, which were rich in β-carotene, but the content of α-carotene was very low whose main resource was carrot. It could provide scientific and accurate basis that determinating the α-carotene and expressing into RE with corresponding conversion coefficients.3. The improvement of determination method could bring the change of food composition data, which could affect the assessment of dietary intake. When using the existing carotene data to take evaluations, it should make reasonable correction, and still could meet the current needs.