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. (C) 1999 Elsevier Science Ltd. All rights reserved.