Proteinaceous Surfactants Produced from Gelatin by Enzymatic Modification: Evaluation for Their Functionality

Abstract

ABSTRACT Proteinaceous surfactants were prepared by applying the “one‐step process” which permitted covalent incorporation of amino acid esters directly into proteins during treatment with papain. Gelatin was used as a hydrophile and n ‐alkyl esters of L‐leucine as lipophiles. Each of the hydrophile‐lipophile mixtures was incubated with papain under the following conditions: medium, 1M carbonate (pH 9) or a 20:80 mixture of acetone‐1M carbonate (pH 9) containing 2 mM 2‐mercaptoethanol; concentration of gelatin in the medium, 33% (w/w); L‐leucine ester vs gelatin ratio, 0.1 mole/100g; papain vs gelatin, 1% (w/w); incubation period, 15 min; and temperature, 37°C. The enzymatic reaction was stopped by adding 1N HCl and the product purified by dialysis followed by washing with hot acetone or dichloromethane to remove low‐molecular species. Each product was found to be a mixture of peptides having a wide range of molecular weight, with an average at approximately 7,500 daltons. The amounts of the alkyl moieties covalently incorporated were in a range 1.1–1.2 moles per 7,500g of the products. Their surfactancy varied depending particularly on the carbon number of the alkyl moiety; the products resulting from the incorporation of C 4 –C 6 alkyl esters of leucine showed greater whippability, whereas the incorporation of the C 10 –C 12 alkyl esters gave products having a higher ability to stabilize an o/w type emulsions.