Comparative Study of Ascorbic Acid Content in Fresh and Packaged Fruit Juices Using Iodometric Titration

Abstract

This research was conducted to estimate and compare the concentration of ascorbic acid (Vitamin C) in a variety of natural and processed fruit juices using the iodine titration method. A total of 14 samples were analyzed, categorized into two groups: seven types of fresh natural fruits (mango, strawberry, guava, pineapple, banana, orange, and lemon) and their corresponding seven types of commercially packaged or canned juices. The chemical principle employed is a classic redox reaction where ascorbic acid acts as a reducing agent that reacts quantitatively with iodine. During the titration, ascorbic acid is oxidized to dehydroascorbic acid, while iodine is reduced to iodide ions, with a starch indicator signaling the endpoint by forming a blue-black complex. The experimental results revealed significant variations in vitamin C content across the different juice types. Among the natural juices, orange juice recorded the highest concentration at 69.7 mg/100 ml, followed by guava at 58.3 mg/100 ml, while banana exhibited the lowest value at 6.33 mg/100 ml. In the processed juice category, orange juice again topped the list with 59.17 mg/100 ml, whereas mango juice showed the lowest concentration at 3.4 mg/100 ml. The study confirmed an inverse relationship between the canning process and vitamin C concentration, as a notable loss was observed in all processed samples compared to their natural counterparts. Strawberries and mangoes were the most affected, with loss percentages exceeding 50%, likely due to thermal pasteurization and oxidation during storage. Conversely, lemon and pineapple juices demonstrated higher chemical stability, attributed to their low pH levels. The findings underscore the importance of consuming fresh juices, particularly citrus and guava, to meet daily nutritional requirements, and highlight the precision of industrial quality control compared to natural biological variability.