PHYSICO-CHEMICAL PARAMETERS OF FRUIT JUICES -EVOLUTION DURING STORAGE

Ana Leahu, Cristina Damian, M. Oroian, Sorina Ropciuc

Abstract
The purpose of this study is to analyze the changes for the main physico-chemical characteristics: pH values, vitamin C, acidity, density, water activity of fruit juices during storage. The citrus juices, orange juice is the most appreciated and used because of its flavor and high content of vitamin C. Evaluation of the quality and determination of life (shelf life) it is based mainly on the progress of vitamin C during storage. Fruit juices were prepared using a robot type fruit squeezer. Were prepared orange juice, kiwi, apple, the flesh and clear and mixed fruit in different proportions. Physico-chemical characteristics were determined from fresh juice as well as from juice kept in refrigerator, at certain time intervals (one day, two days, five and seven days). The storage of these juices under refrigeration conditions has determined percentage reductions of vitamin C content of these ones. Among the analyzed juices the product with higher content of vitamin C is kiwi fresh juice and juice mixture Kiwi: 70:30 orange has the highest content of vitamin C, 83.6 mg or 96.8mg per 100g of product. Decreasing the amount of ascorbic acid per 100 g of product is evident in orange juice and mixture juice, compared to 100 g product.

Key words: clear juice, vitamin C, kiwi fruit, orange, apples