EFFECT OF DEIONIZATION ON PHYSICAL-PROPERTIES OF GELABLE PROTEIN PRODUCTS RECOVERED FROM SOLID TANNERY WASTE

Extraction of gelatin or gelable protein products from solid tannery b y-products has been demonstrated previously. During the commercial man ufacture of gelatin from limed hides, skins and bones, it is common pr actice to pass the gelatin through a mixed-bed deionizing column in or der to reduce the ash content of the protein. In the gelable protein p roducts that we are isolating from chrome-tanned waste, the ash conten t is relatively high and is a function of both the alkali treatment an d the original composition of the chrome waste. We have shown that dei onizing the protein will reduce the ash. There is, however, a question as to what effect this treatment will have on the Bloom and the visco sity - commonly reported analyses for gel quality. Moreover, we have p reviously shown that the choice of alkali will affect the physical pro perties. In this study, chromium waste was treated with hydroxides and carbonates in combination with magnesium oxide to extract gelable pro tein products, and physical properties were measured before and after deionization. We found that the physical properties were improved in t he deionized samples and this is probably due to the increased protein concentration with a small effect contributed by the removal of the a sh. Protein yields were also calculated and we found that the type and concentration of alkali used to extract the gelable protein will affe ct the yield. We also demonstrated that these processes are reproducib le and that good material balances can be obtained.