Low-frequency ultrasound as a tool for quality control of soft-bodied raw ewe's milk cheeses

Abstract The relationship between the quality attributes and the ultrasound parameters of Protected Designation of Origin (PDO) soft-bodied cheeses from “Torta del Casar” and “Queso de la Serena” was studied. Cheese samples were taken from six different dairy industries (three for each PDO) in two different seasons. Ultrasound parameters related to velocity, attenuation and frequency were calculated and correlated with the physico-chemical, microbiological, rheological and sensorial properties of the cheeses. Several ultrasonic parameters showed a high correlation with changes in the physico-chemical, textural and sensorial properties of this product, which were partially associated with microbial activity. Among these, stand out the negative correlation of the sensorial descriptor “firmness” with bulk modulus (κ). The predictive models achieved by the multivariate linear regression method (MLR) showed the highest correlation coefficients for firmness by texture compression analysis (TCA) and the sensory descriptor “intensity”, including as the explanatory variables for both models, fast Fourier transform (FFT) frequencies and attenuation parameters. This work highlights the on-line capability of ultrasound for non-destructive quality assessment of this traditional and heterogeneous soft cheese based on the predictive potential of several secondary ultrasonic parameters.