Luminescent laboratory stand for rapid diagnosis of milk quality: optimal time parameters

The quality control of milk and dairy products using innovative diagnostic methods is considered. The relevance of using methods and means of non-destructive/contactless rapid diagnostics for quality control of milk and dairy products, for example, based on the photoluminescence effect, is shown. The optimal operating modes of the luminescent laboratory bench developed earlier by the authors of this article for rapid determination of optical properties of milk have been selected. The stand allows measuring the photoluminescence of milk in the spectral ranges of protein, fat, and vitamin radiation when they are excited by LEDs with a central wavelength of 320, 362, and 445 nm, respectively. Luminescence is detected using photodiodes in the visible spectral range of 420–675 nm, 440–620 nm, and 480–660 nm, respectively. The optimal value of the pulse durations of LEDs, which is approximately 19 microseconds, has been experimentally determined, at which the highest photovoltaic luminescence is obtained. The photodiode switching delay value of about 1 microsecond was also obtained. When averaging the signal over 7000 excitation and registration cycles, the measurement time was about 15 seconds, with a relative error of no more than 3 %.

The results obtained can be used in the study of integral photoluminescence fluxes of milk, the construction of dependencies of integral photoluminescence fluxes on the content of protein, fat and other parameters in milk, for example, when conducting studies of the pH level or contamination in milk. The results obtained can provide the basis for the development of devices for non-destructive photoluminescent control of milk, which can be used on farms or in laboratories. 

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