Evaluation of Physicochemical Changes in Hard-Boiled Eggs Stored at Different Temperatures

Eggs that have been hard-boiled are frequently used as ready-to-eat food. Refrigerated and frozen storage of hard-boiled eggs causes issues, such as customer rejection owing to textural changes. The objective of this research is to ascertain how storage temperature affects hard-boiled eggs’ alteration in texture over time. Mediumsized brown shell eggs were acquired from a local market, boiled at 100℃ for 15 min, and then stored at room temperature (25℃), refrigeration (4℃), and freezing (–18℃) conditions for 0, 12, 24, and 48 h. Fourier transform infrared spectroscopy (FTIR), texture profile, visual observation using a gemological microscope, free amino acid content, and color were measured. Freezing had a substantial impact on the eggs’ hardness, gumminess, chewiness, and cohesiveness (p<0.05). The FTIR spectrums confirmed the textural changes in bonds of amide A (3,271 cm–1), amide I (1,626.2 cm–1), amide II (1,539.0 cm–1), C=O stretch of COO- (1,397 cm–1), asymmetric PO2- stretch (1,240 cm–1). Microscopic images confirmed structural changes in eggs stored at –18℃. The free amino acid content was lower in fresh and frozen eggs than in the rest (p<0.05). However, there was no discernible variation in the egg white’s color when eggs were kept at 4℃ (p>0.05). Salmonella spp. was found exclusively in eggs kept at room temperature. In conclusion, hard-boiled eggs did not exhibit structural or chemical changes when stored at 4℃ for up to 48 h compared to freezing and room temperature conditions.