Influences of Different Coating Materials on the Quality Changes of Hardboiled Salted Duck Eggs under Ambient Storage

ABSTRACT

Abstract The present study investigated the influences of selected coatings (paraffin wax (PW), chitosan (CH), whey protein isolate (WPI), and soy protein isolate (SPI)) on the quality changes of hardboiled salted duck eggs when kept under ambient temperature (30±2 oC). At 5-day intervals for 15 days, samples were tested for color (L*, C*, and h˚), shell strength, weight loss, microbial analysis, water activity, moisture, pH, salt content, TBARS, and sensory analysis. L*, C* and h˚ gradually decreased in egg white, whereas C* and h˚ gradually increased in egg yolk. Shell strength gradually decreased in all cases, and weight loss similarly increased throughout the storage. PW and WPI coatings gave the best shell strengths and the least weight loss. The aw was not significantly different between the treatments. WPI and PW retained the most moisture. A slight decrease in pH was observed in all the samples (P ≥ 0.05). On the other hand, salt content gradually increased with storage time, and the WPI and SPI treatments gave < 2% salt accumulation. TBARS steadily increased throughout storage, and the WPI samples had the least lipid oxidation. TPC, mold, and yeast at the end of storage were the least with the WPI treatment. Both the storage period and coating material choice significantly influenced the sensory scores that declined throughout the storage. Overall, the WPI coating treatment gave the best results.