Control of milk acidity by photoluminescence

Abstract

SummaryFor a quality assessment of milk and dairy products, the optical methods are used. In this paper, the use possibility is investigated of the optical method of photoluminescence for the milk acidity value finding out. The spectral measurements were carried out on a diffraction spectrofluorimeter in the range of 200–500 nm. The milk acidity measurement accuracy was controlled by the titrimetric method. It is established that as far as milk sours, the excitation spectra in the range of 200–500 nm decrease; but there are qualitative changes in the range of 350–500 nm. With acidity growth, the photoluminescence flux decreases if it is excited by the radiation value λe = 262 nm, grows at λe = 385 nm and decreases at λe = 442 nm. It is advisable to control the milk acidity in terms of the photoluminescence fluxes ratio Φ385/Φ442. The linear approximation of the function Φ385/Φ442(K) is statistically reliable (the determination factor R2 = 0.99).