Measurement of brown eggs freshness using non-destructive UV/VIS spectroscopy and viscosity of egg white

Abstract

The present research aimed to determine the freshness of brown eggs using non-destructive ultraviolet-visible (UV/VIS) transmission spectroscopy (λ = 350-1020 nm) and viscosity measurement during storage for 7 days. As per human visual perception, the eggshell color varied from light yellow-brown to dark red-brown, distributed near the edge of the spectral locus of orange to a red region in the CIE 1931 chromaticity diagram. Quantitatively characterized luminance (CIE Y) values of the eggshell brightness were 7.77 (darkest) and 49.1 cd/cm2 (brightest). The L* value (brownness) of the eggshell increased while the a* value (redness) decreased. The correlation between luminance and transmittance values was evaluated using a linear regression model which showed a correlation coefficient of 0.92. The transmittance spectra collected daily showed a gradual increase from 36.0% (day 1) to 38.8% (day 3). The slope of this increment became steeper after day 3 and reached 50.8% (day 7). The freshness of the eggs calculated based on the transmittance value of 100% (day 1) showed an inverse relation with the storage time and was reduced by 59% (day 7). Egg white exhibited non-Newtonian shear thinning behavior and showed a reduction in viscosity by 13.7% reduction on day 7 as compared to that on day 1. Our results clearly demonstrated that the freshness of the eggs declined with an increase in storage time. This analytical method of measuring egg freshness has potential applications in designing an automatic egg selection machine, to identify stale eggs from the fresh ones on-site in small and medium egg farms by simply measuring the transmittance of eggshells of varying darkness.