Influence of low-temperature storage on the cell wall polysaccharides of plum fruit Prunus domestica

The interest to plant foods rich in dietary fibers increases due to their physiological and metabolic effects: creating favorable environment for intestinal microbiota, prevention and control of obesity, atherosclerosis, coronary heart diseases, and co- lorectal cancer. Fruits are of particular interest because of their high content of soluble dietary fibers. The determination of the composition of polysaccharides (pectin, cellulose and hemicellulose) is important for understanding of their physio- logical functions. Plum is one of the most common stone fruits in many countries. Among stone fruit crops, it takes the second place in the collection of fruits all over the world, with second only to peach. Нowever, plums are perishable stone fruits. This leads to a short shelf-life of these fruits, thus imposing serious restric- tions for their processing and transportation. Rapid post-harvest softening and subsequent microbial infestation leads to losses in the marketing chain. Low tem- perature storage of plums is recommended to preserve nutrients in fresh fruits and maintain quality. However, little is known about the changes in the polysaccharide and monosaccharide composition of polysaccharides during low-temperature storage of fruits and vegetables. The textural changes (softening) occurring during fruit ripening are caused by enzyme-mediated changes in the composition and structure of cell wall polysaccharides, such as pectin polysaccharides and cellulose. This leads to partial solubilization of cell wall polysaccharides. Therefore, we evaluated the mechanical properties of plum fruits using a puncture test, as a test for determin- ing the starting point of the fruit aging period (overripening). The polysaccharide and monosaccharide composition of polysaccharides from skin and pulp of plums were determined before and after low-temperature storage. As the storage duration of fruits increased, their mechanical properties (hardness, firmness and elasticity) gradually decreased. The sharpest changes in the values of the apparent modulus of elasticity were qualified as the point of the beginning of the period of fruit aging (overripening). Thus, in the course of the research it was found that the change in texture properties of plum fruits Prunus domestica during low-temperature storage is accompanied by the destruction of intermolecular bonds between the cell wall polysaccharides and their subsequent partial degradation.