Tannic acid and protein interact to form soluble and insoluble complexes, and the latter are favored by a pH near the isoelectric point of the protein and an excess of tannic acid. As the concentrations decrease, higher ratios of tannin to protein are possible in soluble complexes. The number of sites on a gelatin molecule occupied per tannin molecule decreases as the tannin concentration increases. and this is accompanied by a decrease in the apparent equilibrium constant of binding between the tannic acid and the gelatin. Bonding between gelatin and tannin molecules is strong, particularly when a greater weight of gelatin than tannin is present; hence, there is relatively little unbound tannin in such soluble systems. Tannic acid is heterogeneous with regard to its ability to precipitate gelatin. Under no conditions could all the added tannic acid be precipitated by gelatin.in understanding of the interactions between tannins and proteins is of importance for effective control and *removal of haze in natural beverages. Much of our knowledge of these reactions comes from work in the field of leather research (Gustavson, 1956); however, the conditions

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SUMMARY Snap bean pectin methylesterase had a pH optimum of 8.2. Its activity was enhanced by the presence of salts such as sodium chloride and calcium chloride. Low pH conditions increased the susceptibility of the enzyme to heat inactivation. There were indications that conditions were present in the intact pod which protected the enzyme from heat denaturation. The enzyme had a Q10 of 1.4 over a wide temperature range. It was not regenerated on frozen storage.