Turbidity changes of birch tree sap after addition of commonly available chemicals

The problem signalled both by the popularizers of birch tree sap consumption, as well as in many scientific articles and sap collection manuals is short shelf life, hindering the wider use. The loss of shelf life is manifested by the appearance of a characteristic turbidity and simultaneously intensifying unpleasant odor. Most of birch sap shelf life extension methods, that inhibit turbidity, are non-thermal methods, based on the physical techniques, ex. ultraviolet radiation, ultrafiltration, and also combination of this two methods. The aim of this study was to assess the stability of the birch tree sap, depending on the concentration of commonly available chemicals used to extend shelf life of plant origin food products. At room temperature, the sample with addition of ethanol at the concentrations of 10% and 15%, as well as with the addition of citric acid in combination with potassium sorbate were stable during the all turbidity testing period. Additionally, in the refrigerated condition, 27-day stability has been obtained for the sap with the addition of ethanol at the concentration of 5% and 15-day with the addition of citric acid in concentration of 0,5%. This stable solutions obtained, however, are not suitable for direct consumption. They can only be used as a stable base for the preparation of beverages, after the addition ex. herbal extracts, fruit juices and syrups, honey.