Effect of pre-treatment on pressing efficiency and properties of rhubarb (Rheum rhaponticum L.) juice

This study reports the influence of freezing and thawing techniques, as a pre-treatment, on the efficiency and quality of rhubarb (Rheum rhaponticum L., Lider and Malinowy varieties) juice yielded by pressing. Pre-treatment of rhubarb fragments by freezing and thawing caused a significant increase (up to 30%) in the efficiency of the pressing process. Juices obtained with this method showed higher extract content and slightly higher acidity, but had similar dynamic viscosity. All the juices obtained showed the features of Newtonian fluid. Interestingly, the juices obtained with various technologies had significantly different chemical composition. Higher level of oxalates was recorded when preliminary freezing and thawing treatment was used. Both double pressing and the pre-treatment of freezing and thawing resulted in an increase of sample transparency and juice color intensity. The originality of this development involves the use of freezing and thawing of the pulp as a new form of pre-treatment in juice pressing from raw materials of plant origin. The method can be used in the production of high-quality organic juices.