Influence of Prolonged Salting on the Physicochemical Properties of Duck Egg White

Salted duck eggs are unique among the important authentic foods of Thailand. They are mainly produced in Chaiya district, Surat Thani province, in the southern part of Thailand. The egg whites of salted duck eggs are normally unusable due to heavily salty taste upon prolonged storage. The present study was aimed to examine the foaming characteristics of egg white after being cured for a prolonged period (30 days). At 5-day intervals the egg whites were measured for salt, moisture, water activity, hydrophobicity, pH, zeta potential, particle size, SH groups, surface tension and foaming properties (index of whipping, foam durability, specific density, overrun, air phase and yield stress). The results showed that prolonged curing significantly affected egg white and its foam. Salt content, hydrophobicity, particle size, and exposed SH groups gradually increased with storage period. On the other hand, moisture, water activity, pH, zeta potential, surface tension and total SH groups decreased continuously throughout the storage. In addition, foaming properties slightly declined due to accumulation of salt content with extended storage. Conversely, the yield stress - an important indicator of foam quality - increased from 32.33 to 70.55 during storage. Overall, the egg whites could possibly serve as a key and/or a substitute ingredient in foam-based food products.