Determination of the content of l-ascorbic acid in fruit jelly

Abstract

The article presents the results of the development of a method for the determination of L-ascorbic acid (AA) in model fruit jellies containing gelatin. In the determination of AA, a coulometric method with electrically generated iodine as a titrant in a galvanostatic mode with a current of 2−5 mA was used. As a research object, model fruit jelly with 2% and 3% gelatin content was used. In addition to gelatin, the systems contained apple juice concentrated clarified and potassium sorbate (used as a concerto). The peculiarity of the preliminary preparation of the samples was the stage, which envisaged the melting of the samples before the quantitative determination of AA. In order to assess the suitability of the proposed methodology for the quantitative determination of AA in fruit jelly, a validation evaluation was performed on the following parameters: specificity, linearity and the range of an analytical method, limits of detection and determination, accuracy and reproducibility. Specificity has been studied on standard aqueous solutions of AA. It has been shown that under two conditions: 100% of current output and stoichiometricity of the oxidation reaction with iodine AA, the theoretical slope of the amount of the electrice curve from the analyte concentration with accuracy up to 0.2% coincides with the experimental one. The following parameters were determined: the working area of the technique 4.92−127.6 mg/100 g; limits of the determination 1.62 mg/100 g and quantitation 4.92 mg/100 g. The absence of a systematic error for standard and fruit jelly solutions was evaluated using the "introduced-found" method. Error of recovery did not exceed RSD<2.8%. Correctness and reproducibility were evaluated by the method of varying the weights at three levels of concentration using three sets at each level. Fischer and Student's criteria, which were used to compare average values, testified to the validity of the indicators of "correctness" and "reproducibility". Comparing the studied parameters, the best results were obtained for fruit jelly with a 2% gelatin content compared to a jelly with a content of 3%. The obtained results testify to the possibility of application of the developed method of determination of ascorbic acid in real food systems.

Наведено результати розробки методики визначення аскорбінової кислоти в модельних фруктових желе, що містять желатин. Запропонована методика базується на кулонометричному титруванні електрогенерованим йодом у гальваностатичному режимі розплавлених зразків фруктового желе. Досліджено параметри валідаційної оцінки: специфічність, лінійність, робоча область методики, межі виявлення та визначення, правильність та відтворюваність. Отримані результати свідчать про можливість застосування розробленої методики визначення аскорбінової кислоти в реальних харчових системах.