Evaluation of shelf life of egg treated with edible coating by means of NIR spectroscopy and laser induced diffuse reflectance imaging

Abstract

A coating solution was developed by blending cassava starch at different levels (2%, 3% and 4% w/v) with gelatin and plasticizers to maintain the quality of eggs during 4 weeks of storage (25 ± 1 °C, 60–65% RH). This study suggests the rapid techniques of near-infrared (NIR) spectroscopy and laser-induced diffuse reflectance imaging for determining the internal quality of eggs. The scanning electron microscopy (SEM) micrographs showed that the coatings were effective in protecting eggshells. During storage, coated eggs had lower weight loss and albumen pH, higher Haugh unit and yolk index than control eggs (p < 0.05). These factors are the most common parameters in assessing egg quality. Among the coating formulas, the 4% starch coating had significantly higher effectiveness from the 3rd week of storage. The results indicated that the coating solution containing 4% starch could maintain the egg quality up to 28 days. Furthermore, the NIR spectra were used to develop prediction models for the investigated quality attributes using partial least squares regression (PLSR). Models were created using 3 preprocessing methods of standard normal variate (SNV), first derivative (lD) and second derivative (2D). The PLSR-SNV model achieved the best prediction for weight loss (R2 = 0.883, RPD = 2.920), Haugh unit (R2 = 0.756, RPD = 2.025), and yolk index (R2 = 0.807, RPD = 2.276). Laser scattering was successfully used to detect the egg quality change during storage by linear discriminant analysis (LDA) at wavelengths of 532 nm and 780 nm. The descriptive attributes extracted from intensity profiles showed significant effects of storage time, treatment and their interaction. This research highlighted the promising application of NIR and laser-induced diffuse reflectance imaging for inline control of egg quality at room temperature.