Effects of concentration by membrane processes and storage conditions on some physicochemical properties of strawberry juice

In this study, it was investigated the use of membrane systems in the clarification and concentration of strawberry juice, and examined the changes in some physicochemical properties of the strawberry juice samples stored at 4°C and 22°C for 6 months. During the clarification stage, the traditional gelatine-bentonit application and the use of ultrafiltration membrane with a pore size of 50 kDa showed similar results in terms of product characteristics. On the other hand, ultrafiltration membrane with a pore size of 10 kDa revealed different results especially in terms of phenolic compounds, since these compounds have particularly higher retention rates in such membranes. It was determined that the use of membrane distillation, osmotic distillation, and the integrated system applications combining both methods in order to concentrate strawberry juice were more advantageous than the thermal evaporation especially in terms of preventing the HMF formation, limiting the loss of anthocyanin and preserving the color characteristics. There were no significant difference between the concentration methods regarding the properties such as pH, total acidity, and sugar. However, it was determined that the ascorbic acid degradation in strawberry juice samples concentrated by membrane systems was higher than the samples concentrated by thermal evaporation. Either the effects of storage time or the storage temperature on strawberry juice samples stored at refrigerator conditions and at room temperature were found to be important in terms of many parameters investigated. As a matter of fact, there were significant losses in components such as total flavonoid, total monomeric anthocyanins and ascorbic acid during storage. Furthermore, the results of the sensory evaluation showed a decrease in the acceptability for color, taste, and odor. Consequently, the storage temperature should be kept lower in order to preserve the quality properties of the product more efficiently. Keywords: Strawberry juice, clarification, ultrafiltration, concentration, membrane distillation, osmotic distillation