European food research and technology vol:226 issue:5 pages:1119-1126
The objective of this preliminary study was to evaluate the usefulness of front face fluorescence spectroscopy to predict some chemical parameters [pH, fat, dry matter (DM), fat in DM, total nitrogen (TN) and water soluble nitrogen (WSN)] and cheese meltability of semi-hard and hard cheeses. Dynamic testing rheology was used to determine the melting point of cheeses corresponding to the temperature at which loss tangent (tan delta) = 1. Tryptophan and vitamin A fluorescence spectra were, also, recorded on cheese samples at 20 degrees C. The partial least squares (PLS) regression with the leave one-out cross-validation technique was used to build up calibration models. Excellent predictions were obtained from the tryptophan and vitamin A models for fat (R-2 = 0.99 and 0.97, respectively), DM (R-2 = 0.94 and 0.96, respectively), fat in DM (R-2 = 0.92 and 0.99, respectively), TN (R-2 = 0.91 and 0.91, respectively). Excellent predictions were also obtained for WSN (R-2 = 0.96) and melting point (R-2 = 0.97) from vitamin A spectra, while only good predictions for these two parameters (R-2 = 0.90 and R-2 = 0.87, respectively) were obtained from tryptophan spectra. The results for pH were good (R-2 = 0.82) and approximate (R-2 = 0.76) with tryptophan and vitamin A, respectively.