Abstract:

With borax as control, the effects of 16 stabilizers of citrate, polyols and esters, temperature, pH and amount of stabilizer on the stability of three proteases in liquid laundry detergent were investigated, and the effects of surfactants AES, AEO and APG on the activity of protease were also investigated based on the main components of liquid laundry detergent. Results show that the stability of citrate, especially calcium ammonium citrate, is the best, and the stability of APG0810 and APG1214 is close to that of borax. When the amount of protease was 0.5%, the three-week activity retention rates of protease stabilized by calcium ammonium citrate-APG0810-APG1214 ternary complex stabilizer system, Purafect 4000L and Purafect Prime 4000L complex stabilizer at pH=7 and 25 ℃ were 84.3% and 71.5%, respectively; the three-week activity retention rates at pH=8 and 37 ℃ were 47.2% and 30.4%, respectively; and the three-week activity retention rates of protease stabilized by borax at pH=7 and 37 ℃ were 2.87% and 13.5%, respectively. In addition, AES can significantly reduce the enzyme activity, while non-ionic surfactants AEO₇ and AEO₉ did not. However, the mixing of AEO and AES cannot reduce the damage of AES to the enzyme activity. It can be considered to increase the use of APG and AEO in liquid enzyme-enhanced detergents.

Key words: enzyme-enhanced liquid detergent, protease, retention of enzyme activity, stabilizer