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.
Publisher
The Korean Society of Food Preservation