Determination of Vitamin C Content in Foods

aspiration of Vitamin C Content in nutrientsZheng XiaoIntroductionVitamin C, likewise known as L-ascorbic sharp, is an essential component of our diets. It is a good antioxidant, a key component that helps to prevent damage to proteins and deoxyribonucleic panellings. In the food industry, vitamin C is added to development the nutritional field of study of food products and also for preservative purposes. As the human body is unable to synthesise vitamin C, it would have to be consumed as incision of our diet. heady fruits and vegetables for instance are common sources of vitamin C.Vitamin C is a labile compound and is easily degraded by enzymes and atmospheric oxygen. Its oxidation can be quicken by excessive heat, light, and heavy metal cations (Pisoschi, Danet, Kalinowski, 2008). During the manufacturing process, some vitamin C would be lost. Thus, in fruit juice products, vitamin C level is commonly used as a gauge for quality. This prompts manufacturers to fortify the ir products with high levels of vitamin C to ensure that sufficient vitamin C is present in the product throughout the storage process. Due to the encompassing use of ascorbic dot in both food products and in the pharmaceutical industry, many analytical methods exist for the determination of ascorbic corrosive, including titrimetric, spectrophotometric and chromatographic methods, each with their advantages and disadvantages.An example of a titrant used is 2,6-dichlorophenolindophenol (DCIP), which will oxidise the ascorbic acid that is present in the sample. While titrimetric methods are simple to use, they are also known to overestimate the amount of ascorbic acid present due to the presence of oxidisable species other than ascorbic acid (Hernndez, Lobo, Gonzlez, 2006). In addition, many interferences often occur with coloured samples (Arya, Mahajan, Jain, 2000). An example would be the masking of colour veer at the end point of titration by highly coloured extracts from fru its and vegetables (Eitenmiller, Landen, Ye, 2007).Spectrophotometric methods work by determining the absorbance of vitamin C which is compared against standard dousings. However, such methods are susceptible to practical interference due to absorbance exhibited by other components that is present in the sample matrix.Lastly, chromatographic methods are commonly used because of their simplicity, short compendium time and sensitiveness (de Quirs, Fernndez-Arias, Lpez-Hernndez, 2009). The sample is separated into its components based on their relative affinity with the mobile and stationary phase. Reversed-phase high performance liquid chromatography (RP-HPLC) for instance is a very(prenominal) efficient method that is used in ascorbic acid analysis of fruits, vegetables and beverages. Ascorbic acid is relatively hydrophilic due to the presence of several hydroxyl groups. Thus, it has a higher(prenominal) affinity to the polar mobile phase than the non-polar stationary phase, a llowing it to be separated from the other components in a sample. The retention time gives a qualitative analysis of the sample while the area under the inflorescence allows for the quantitative determination of ascorbic acid content present. However, a major disadvantage of this method is its high personify compared to other conventional methods.The objective of this experiment is to determine the ascorbic acid content in commercial guava bush juice by RP-HPLC.Materials and MethodsThe product analysed was commercial guava juice.The experimental procedure was as stated in the laboratory manual, with the slight amendments as follows. The filtrate (2mL) from the centrifuged sample was diluted (1 part sample 4 part acetic acid) with 2% acetic acid. Five sets of standard ascorbic acid solutions were prepared (40ppm, 80ppm, 120ppm, 160ppm and 200ppm for each set) using a stock solution (1000ppm ascorbic acid) and 2% acetic acid for dilution. The standard solutions were filtered using the 0.45 micron cellulose acetate syringe filter, beginning with the lowest concentration. The column used was a Phenomenex Ultrasphere 5u C18 column (1504.6mm) and the wavelength used was 254nm.Results and DiscussionA standardisation graph was plotted (Figure 1) using average out peak area (Table A1 in appendix) for standard solutions versus their respective concentrations.For each standard solution, four duplicates were prepared. This was done to increase the true statement of the calibration curve. The r2 harbor obtained (0.9984) was close to the ideal value 1, indicating a good linear correlation between the area under peak of interest and ascorbic acid concentration. This allows good estimates of ascorbic acid content to be made given the area under peak of interest for each sample.Table 1. Ascorbic acid concentration in samples prepared by Groups 10 to 18Sample calculation for Group 11Ascorbic acid concentration in diluted sample = = 116ppmAscorbic acid concentration in o riginal sample = 116ppm 5 = 581ppm = 58.1 mg / 100mL of juiceAverage ascorbic acid concentration in original sample= =58.0 mg / 100mL of juiceThe average retention time of the samples prepared by different groups was 2.557min (Table A3 in Appendix), which is highly similar to that of the ascorbic acid standard solutions was 2.559min (Table A2 in Appendix). This verifies that ascorbic acid was the component analysed.The average ascorbic acid concentration in the guava juice product determined experimentally was 58.0mg/100mL of juice. This was approximately 3.9 times higher than the amount indicated on the packaging (15mg/100mL). As mentioned earlier, As the expiration date is approached, ascorbic acid would be lost to different extents depending on the storage conditions (Kabasakalis, Siopidou, Moshatou, 2000). Manufacturers are known to add ascorbic acid to their products to improve their nutritional value and also to account for the ascorbic acid lost during the manufacturing and storage process (Ottaway, 2008). Since the experiment was conducted before the expiration date of the product (March 14, 2014), a higher ascorbic acid content would be expected.The original ascorbic acid concentration for group 14 was excluded from the calculation as it was almost double of other results and thus likely to be an outlier. A possible reason might be an error in dilution during the preparation of the sample. The other results were found to be precise with a low standard passing (1.4) and a low coefficient of variation (2.5%).ConclusionThe ascorbic acid content of commercial guava juice determined using RP-HPLC was 58.0mg/100mL of juice.ReferencesArya, S. P., Mahajan, M., Jain, P. (2000). Non-spectrophotometric methods for the determination of Vitamin C. Analytica Chimica Acta, 417(1), 1-14. doi http//dx.doi.org/10.1016/S0003-2670(00)00909-0de Quirs, A. R.-B., Fernndez-Arias, M., Lpez-Hernndez, J. (2009). A screening method for the determination of ascorbic acid in fruit juices and soft drinks. Food Chemistry, 116(2), 509-512. doi http//dx.doi.org/10.1016/j.foodchem.2009.03.013Eitenmiller, R. R., Landen, W. O., Ye, L. (2007). Vitamin Analysis for the Health and Food Sciences, Second Edition Taylor Francis.Hernndez, Y., Lobo, M. G., Gonzlez, M. (2006). Determination of vitamin C in tropical fruits A comparative evaluation of methods. Food Chemistry, 96(4), 654-664. doi http//dx.doi.org/10.1016/j.foodchem.2005.04.012Kabasakalis, V., Siopidou, D., Moshatou, E. (2000). Ascorbic acid content of commercial fruit juices and its rate of loss upon storage. Food Chemistry, 70(3), 325-328. doi http//dx.doi.org/10.1016/S0308-8146(00)00093-5Ottaway, P. B. (2008). Food Fortification and Supplementation Technological, Safety and Regulatory Aspects Elsevier Science.Pisoschi, A. M., Danet, A. F., Kalinowski, S. (2008). Ascorbic Acid Determination in Commercial Fruit Juice Samples by Cyclic Voltammetry. journal of Automated Methods and Management in Chemis try, 2008. doi 10.1155/2008/937651AppendixTable A1. Area under peak of interest for standard solutionsAverage area under peak for 40ppm= = 2197282Table A2. Retention Times for standard solutionsTable A3. Retention Times for samples prepared by Groups 10 to 18