Application of near infrared spectroscopy to estimate selected free amino acids and soluble nitrogen during cheese ripening

Abstract

This paper deals with the estimation of tyrosine, tryptophan and soluble nitrogen in 288 samples of the Edam cheese using the Near Infrared Spectroscopy. For analyses, the apparatus NIR Nicolet Antaris was used working in the regime of reflectance (i.e. using an integrating sphere) in combination with fibre optics (i.e. using a probe). For calibration, reference data from the UV spectrophotometer was used. Calibration models were developed using a PLS algorithm (least square method) and tested by means of cross-validation. Correlation coefficients: R = 0.911, R = 0.929 and R = 0.959 for soluble nitrogen, tryptophan and tyrosine, respectively, were achieved during measuring in the integrating sphere; R = 0.807, R = 0.945, R = 0.928 were achieved for soluble nitrogen, tryptophan and tyrosine, respectively, during measuring by probe. The results of the study show that NIR technology is suitable for fast and approximate determination of the level of cheese ripening. This can be used for the evaluation of the material for the processed cheese production, or cheese sale in optimal level of ripening.