Department of Biochemistry, Microbiology and Physics, Faculty of Agriculture, Trakia University, 6000 Stara Zagora, Bulgaria
Abstract. The aim of the study has investigation of the feasibility of Near Infrared Spectroscopy (NIRS) and aquaphotomics as a tool for the monitoring a changes during ripening of Bulgarian yellow cheese from cow milk. The cheeses were made according to Bulgarian national standard for Bulgarian yellow cheese from cow milk. Samples for spectroscopic and chemical analysis were taken after 1, 15, 20, 25, 30, 35, 40 and 45 days of ripening. Total protein, water- soluble protein, dry matter and titratable acidity were determined for all samples. NIRS measurements were performed by NIRQuest 512 spectrometer (Ocean Optics, Inc.) in the region 900-1700 nm using reflection fiber-optics probe. Aquagram coefficients were calculated. Differences in spectral data of cheese samples in the range of first overtone water region from 1300-1550 nm were found. The changes of aquagram patterns of cheese samples were significant. Investigation of aquagrams showed decreasing the free water and the number of hydrogen bonding of water molecules and increasing of solvated water in the process of ripening. Changes in aquagram patterns depend mainly on changes in titratable acidity and protein fraction in cheese during ripening. We can conclude from obtained results that NIR Spectroscopy and aquaphotomics has a potential for monitoring cheese ripening stage.