## 3 Results and Discussion
### Photon Emission  
Considering the quality requirements of contemporary food and the degree of awareness of the potential consumer, the identification of the features of the offered product is fundamental. The aim is to eliminate cost-intensive research in favor of technology that allows similar parameterization of the product, but at the same time registers the synergistic effect of various product features that indicate its quality, origin, or production method. Logical relationships between the number of photons emitted by the studied food products and the concentration of biologically active substances and the degree of processing in them were noticed. A higher number of photons emitted is probably associated with pro-health values of food [35]. Attempts have also been made to use ultra-weak luminescence (USL) to assess the quality of Jonagold apples [36]. Research conducted by many authors has confirmed the validity of research connected with fluorescence atrophy recording by the time-correlated single photon counting (TCSPC) method correlated with time [37]. In the current paper, the counting of the photons was done by PMT method (photomultiplier tube method) [38; 39]. In the case of chicken eggs, of which the production takes place in various systems of maintenance and various feeding regimes, parameterizing them in terms of quality is particularly important. The tests analyzed the spontaneous luminescence properties of eggs, which were produced in two rearing systems, i.e., caged and free-range systems. The total number of photons registered during the entire measurement for an experimentally determined cycle, which was 600 s, was on average 366.5 for eggs from cage hens, and 441 for eggs for free-range eggs. Thus, the difference in absolute values was as much as 74.5 units, which confirmed the accuracy of the selection and the suitability of the method for identifying eggs from different farming systems. Taking into account the unitary total photon emission considering the mass of eggs, it was found that it was 7.18 photon/s for eggs from free-range hens, and was 0.871 photon/s higher than the unit emission recorded for eggs from hens from cage housing. [PERSON] et al. [40] found periodic changes in the intensity of ultra-weak luminescence, associated with the spontaneous surface electric potential for the developing soy root (with hypocotyl). There are several papers on the oscillatory processes of ultra-weak spontaneous luminescence of plant organisms. In the analyzed period, changes in photon emission were determined by dividing the time of exposure of the material (total photon emission measurement time--\"x\" axis) into smaller time periods of 100 s, which allowed the time structure of the photon emissions of the examined eggs to be quantified. The applied measurement system generated the result of total photon emission in intervals of 0.25 s. Figure 1 shows the photon emission from fresh eggs in 100 s time intervals (dots marked with assigned values). The dashed line in the drawings describes the emission trend and is not the result of measurements. It was observed that eggs obtained from free-range eggs (blue line) in each of the analyzed compartments were characterized by a higher degree of emission compared to caged eggs (red line). The maximum relative difference of 29.1% was recorded in the case of a time interval of 100 to 200 s, where the number of photons emitted from eggs from free-range housing was 85.5, and eggs from caged housing, 60.5 units. Therefore, this time interval is crucial from the point of view of egg identification on the basis of type of housing. In both of the analyzed cases, photon emission changed in the measured time interval, although it should be noted that the characteristics of changes in the number of emitted photons in the case of eggs from caged hens were more diverse, and photon emissions less stable. The changes relate to the periodic variability of photon emission intensity.