RESEARCH PROFILE: Electrochemical impedance spectroscopy says 'cheese!'

摘要

Cheese is a gastronomic icon in many countries such as Switzerland, Italy, and of course, France, where Charles de Gaulle once quipped, "How can you govern a country in which there are 246 kinds of cheese?" The production of many cheeses relies on rennet, a natural enzymatic mixture that coagulates milk. But monitoring rennet activity can be difficult. In a recent Analytical Chemistry paper (DOI 10.1021/ac1017925), Mamantos Prodromidis and colleagues at the University of Ioannina (Greece) describe a sensor based on electrochemical impedance spectroscopy (EIS) that uses a different approach to analyze rennet. Milk is a colloidal suspension. The colloids, called micelles, are festooned on the surface with a kappa-casein protein layer, the top of which looks like wild, curly hair. the micelles are negatively charged, and repulsive forces keep them in suspension. Rennet contains the protease chymosin, which chews off kappa-casein, decreasing the repulsion between the micelles. The micelles can then aggregate to form curds.