Assessment of Sensory Properties of Cheese by Near-infrared Spectroscopy

Thirty-two batches of semi-hard cheese containing ca. 46% fat in dry matter were produced in a pilot plant in an experimental design with pH, moisture and microbiological contamination with Clostridium tyrobutyricum and propionibacteria as controlled variables. The cheeses were measured ungrated after 5, 7, 9 and 11 weeks of ripening by near infrared (NIR) spectroscopy in transmittance mode (850–1050 nm) and in reflectance mode (1110–2490 nm). Sensory properties were evaluated by a panel of 10 assessors. Calibration equations were developed by partial least-squares (PLS) regression on consistency and flavour attributes. Generally, the accuracy of near-infrared reflectance spectroscopy was better than that of transmittance spectroscopy. The squared correlation coefficients ( R 2) obtained by NIR reflectance spectroscopy were 0.74–0.88 for consistency attributes and 0.27–0.59 for flavour attributes. Depending on the attribute, the standard error of prediction corresponded to the standard error of reproducibility of the average score from 2 to 6 assessors.