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Rheological Method for Evaluating Endoproteolytic Enzyme Activity

¹Katholieke Universiteit Leuven, Laboratorium voor Levensmiddelenchemie, Kardinaal Mercierlaan 92, B-3001 Heverlee, Belgium. ²Novo Nordisk, Biltseveste 12, NL-3432 AD Nieuwegein, the Netherlands. ³Corresponding author. E-mail: Jan.Delcour@agr.kuleuven.ac.be.

A rheological method for evaluating endoproteolytic enzyme activity was developed. The decrease in viscosity as a function of time of dispersion of commercially available modified wheat gluten protein in water (15%, w/w) was measured with a rapid visco analyzer (RVA). Measurement of the RVA viscosity signal at a chosen temperature was continuous and reproducible. As described, the method also can be used to determine the temperature optima of endoproteolytic enzymes at pH values exceeding 5.5 and for partial pH-activity profiles at different temperatures. The method is simple, reproducible, and sensitive and has obvious advantages over more labor-intensive methods in which changes in the rheological properties (elongational viscosity, stretch ratio) of a gluten-starch dough are evaluated as a function of time.