ABSTRACT: Vitamin C (ascorbic acid) is one of the most important and popular vitamins, and is contained in most fruits and vegetables; the problem with vitamin C is its easy degradation during pre-treatment and storage. In this study, kinetics modeling of degradation of ascorbic acid (Vitamin C) in lettuce, cabbage and carrot common vegetables under fridge temperature ranges of (6.5 9.5)0C were investigated and samples after storing at various fridge temperatures and timing were prepared for analysis and High Pressure liquid chromatographic (HPLC) was used for determination of the AA of the common vegetable samples which consisted of an isocratic elution procedure with UV-Visible detection at 245nm.The rate constants and half-lives were calculated using the integrated law method. Activation energy and forecast were determined using Arrhenius equation and time series analysis. Degradation of ascorbic acid in the commonly consumed vegetables under the same pretreatment procedure followed the first-order kinetic model, as the average coefficient of determination (R2-value) was greater than 0.91. The rate constant of ascorbic acid degradation for Lettuce, Cabbage and carrot under the same fridge temperature condition of 6.50C were 0.5165, 0.3214, 0.2273 day-1 respectively. Their half-lives were 1.3420, 2.1566 and 3.0494 day-1, activation energies; 19.4052, 23.3180, 25.7018 Kcal/mol respectively. The ln(C) forecast at 20 days stored at 6.5 0C, lettuce, cabbage and carrot exhibited -3.3537, 0.5080, 1.8486 mg/100g respectively. The proposed models at 6.50C were ln(C) = ln( C0) - 0.5165, ln(C) = ln( C0) - 0.3214, ln(C) = ln( C0) - 0.2273.The most appropriate vegetable under the same fridge temperature and storage is the carrot because its rate constant depicted from the model equations was lower, half life longer, activation energy higher, forecast longer.
Key words: HPLC, Lettuce, Cabbage, Fridge Temperature, Ascorbic Acid, Rate Constant, Activation Energy, Forecast
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