Using technology to measure meat quality

Scientists at Sechenov University, Moscow, alongside their colleagues from Australia, have proposed a quicker and cheaper way to assess meat quality, based on exposing a small sample to UV light and measuring the spectrum of emission. Traditionally, the quality of beef is evaluated by specialists analysing its colour, pattern of fibres (marbling) and carcass weight. However, this method is time-consuming and relies on a subjective opinion of experts. The findings from the study are published in the Journal of Biophotonics.

Fluorescence spectroscopy is the proposed alternative, as it can detect and measure the concentration of various compounds that can emit light of a specific frequency range. These substances include many organic molecules which are found in meat. The scientists behind fluorescence spectroscopy linked the spectrum of the fluorescence of meat with its quality defined by three categories: MSA3, MSA4 and MSA5. Further histological (cell and tissue) analysis measured the concentrations of water and fat in samples, and validated the results.

“This work shows the new opportunities to evaluate the quality of meat objectively by LED illumination and registration of the tissue optical response. It’s interesting to note that this technology, having been developed for the meat industry, can be further translated into medicine and biomedical research,” said Dr Anna Guller, co-author of the paper and senior research fellow of Sechenov University.

Scientists used five pieces of meat for each of the three categories: MSA5 marks slices of the highest quality, with NSA3 the lowest among the qualified meat types. Six samples, each 8 mm in diameter, were cut from different sites of the meat steaks, where the relative content of fat and muscle tissues varied. The samples were exposed to light with the wavelength of 250–350 nm (near and middle ultraviolet) and measured the spectrum of fluorescence in a range of 285–635 nm (middle ultraviolet to the border between visible light and infrared). The intensity of the emission was set on the matrix ‘frequency of excitation – frequency of emission’.

Matrices showing the intensity of fluorescence with various frequencies of excitation and emission. On the last one areas congruent to spectra of intramuscular fat (IMF) and amino acid tryptophan (TRP) are highlighted. Image credit: Islam K et al. Autofluorescence excitation-emission matrices as a quantitative tool for the assessment of meat quality. J. Biophotonics. 2019.

“The principle on which this study was based, ie, the detection of specific autofluorescence of various tissue components, allows evaluation of the structure and functional state of tissues without taking tissue fragments for biochemical or histological analysis,” Dr Guller said.

The results revealed that the spectra of fluorescence of the samples with various ratios of muscle and adipose tissues are discernible. On the matrices of samples with adipose tissue, scientists distinguished spots that match the spectrum of fluorescence of fat-soluble vitamins (A, D, K1, K2 and K3), vitamin B and its components. The spectrum of the samples with muscle tissue coincided with the spectrum of amino acid tryptophan it contains. Scientists selected features that enabled them to define the category of any piece of meat, with research revealing that the highest quality meat (MSA5) had the most intensive fluorescence, and can be distinguished from the lower quantity samples by the difference in brightness of various ranges. The data also revealed that the presence of connective and adipose tissue makes meat more tender, while fat is responsible for its marbling.

Image credit: ©stock.adobe.com/au/Africa Studio