Influence of prolonged ambient storage condition on the physicochemical properties of uncooked and cooked salted duck egg yolk

Abstract

Salted duck egg yolk (SDEY) is rich in numerous beneficial nutrients, particularly proteins and fatty acids, and can be used in various edible condiments. However, uncooked SDEY can readily deteriorate when stored under ambient condition. Thus, the present study examined the changes in the shelf life of SDEY in uncooked and cooked forms stored under ambient condition (28 ± 5 °C) for 15 days. The SDEY was tested every 3 days for various physicochemical properties. The color attributes of SDEY, such as lightness (L*), redness (a*), and yellowness (b*), experienced a notable increase when cooked. This enhancement in color parameters was further amplified with ongoing storage. Additionally, the total color change (ΔE) exhibited a similar upward trend, with cooked SDEY displaying significantly higher values compared to the uncooked samples. The moisture content of SDEY was higher in uncooked samples than the cooked SDEY. On the other hand, water activity was not significantly different between the two samples. Additionally, the uncooked SDEY displayed a significantly higher pH level than the cooked SDEY. Notably, the pH values remained unaffected by the extended storage period. The total salt content was similar in both uncooked and cooked SDEY samples, yet both demonstrated a consistent decrease over extended storage periods. Similarly, all samples experienced a continuous decline in textural characteristics during the storage period. Notably, the cooked samples exhibited increased hardness, cohesiveness, springiness, and chewiness, in contrast to the uncooked SDEY, which showed a higher prevalence of adhesiveness. The total plate count and yeast and mold growth of SDEY continuously increased with storage, but cooked SDEY demonstrated better control against microbial growth. Overall, this study found that cooked SDEY is a better and more economical option for storage under ambient condition compared to the uncooked samples.