A mechanistic, state diagram approach to understanding microwave vacuum drying and expansion of natural cheese

Abstract

This work builds a mechanistic understanding of the changes that take place during microwave vacuum drying (MVD) of cheese, using low-moisture part-skim mozzarella and mild cheddar cheese. The composition, moisture desorption isotherm, mechanical properties at different temperatures, and glass transition temperature ($T_g$) of the cheese samples were determined and correlated with the changes that occurred during MVD. Slight differences in the moisture desorption properties between mozzarella and cheddar were observed and attributed to differences in composition and processing. Young's modulus decreased exponentially with increasing temperature, while the fracture strain increased with temperature up to 35 °C, at which point it decreased drastically. Microwave power had the greatest effect on drying kinetics, while vacuum level only impacted drying kinetics for cheddar. Vacuum level affected the moment when samples transitioned from rubbery to glassy state during MVD, which impacted sample expansion or collapse. A state diagram was created to illustrate the different states of cheese during MVD and to predict puffing vs collapse behavior. This state diagram approach can aid practitioners by reducing the need for experimentation and by facilitating the production of dried cheese snacks with desired structure and texture.