A novel malachite green staining approach for evaluating the internal freshness of egg by detecting the quality of egg cuticle

Abstract

The cuticle is the outermost protective film of eggs, whose quality will affect internal freshness. At present, the undamaged detection of eggs freshness relies on hyperspectral imaging technology, which is relatively complicated. In this study, a novel simple approach for evaluating internal freshness of eggs was further explored by detecting the quality of egg cuticle. Malachite green selected as the alternative dye for quality evaluation of adhesive film, the correlation analysis was carried out by collecting the physical and chemical indexes of eggs with different degrees of freshness. It is found that there was a strong positive correlation between the quality of all parts of the cuticle and internal freshness (p < 0.01), and the Pearson correlation coefficient was over 0.85. The Haugh unit and pH of albumen were most strongly correlated with cuticle quality at the top, with the correlation coefficient of 0.919 and −0.906, respectively. The cuticle quality of eggs with contents got worse than that of eggs without contents, and the holes increased when they were stored for 28 days. In this way, malachite green staining method can be used to identify the freshness of egg cuticle, and the quality of egg cuticle can be used to distinguish eggs with different freshness. This study provided a new direction for the study of egg freshness and assisted to distinguish the quality and safety of eggs nondestructively.