A study of the protein impurities in gelatins with ion-exchange resins

Abstract

The behavior of gelatins on columns of Amberlite resin IRC-50, XE-97 and XE-64 grades was studied. The proportion of gelatin eluted depended on column loading, buffer pH and ionic strength, surface area of resin, type of gelatin and gelatin molecular weight. A small proportion (0.36%) of a protein-polysaccharide complex, probably derived from mucoproteins, was isolated from a lime-processed gelatin under certain conditions. When the proportion of the original material eluted was increased by raising the buffer pH, the ionic strength or the column load, the increase arose from gelatin passing through the column in addition to the small amount of other protein. Acid-processed gelatins, which have higher amide contents and pI values than lime-processed gelatins, behaved similarly to them but in a higher pH range. The non-gelatin protein isolated is similar in amino acid composition to that already reported by Maron (1958). The view that lime-processed gelatins contain 10-19% of a second, very different, component is not confirmed.