Effect of Pectins on Water Crystallization Pattern and Integrity of Cells During Freezing

The ability of various pectin polysaccharides to modify the morphological structure of ice during the phase transitions from water to ice was studied. Pectins were isolated from Sosnowsky's hogweed Heracleum sosnowskyi Manden (heracleuman-N6HS), tansy Tanacetum vulgare L. (tanacetan-N7TVF), and Rauwolfia serpentina Benth callus (rauwolfian-N8RS). Pectins were isolated by multistep extraction. The effect of pectins was assessed using osmometry, thermographic analysis, and cryomicroscopy. A concentrate of leukocytes was used as the sample for the subsequent freezing step. The condition of the leukocyte membrane, and lysosomal and phagocytic activity after a freezing-warming process were assessed. Osmotic concentrations of the pectin polysaccharide solutions were found to be very low. The 0.4 wt % N7TVF solution had the highest osmotic concentration as well as freezing point; however, the duration of its crystallization plateau was lower than that of the 0.4 wt % and 0.2 wt % N6HS solutions. All studied polysaccharide solutions demonstrated a high linear rate of ice crystal growth. There were statistically significant differences between the melting rates for the 0.2% solutions of the pectins, N6HS and N7TVF, N6HS and N8RS, as well as between concentrations for the pectin N7TVF and between concentrations for the pectin N8RS. The data on the integrity of cells that are frozen in a medium containing polysaccharides may indicate a cryoprotective effect of the N7TVF and N8RS pectins, that is, tanacetan from tansy and rauwolfian from rauwolfia. The most effective modifier among the substances, which were studied by us, was the N7TVF pectin polysaccharide (tanacetan from tansy).