The effects of storage time on vitelline membrane protein banding patterns and interior egg quality of eggs from non-molted and molted hens

Vitelline membrane strength plays a role in preventing contamination of albumen by yolk during separation and is important to food safety. Two experiments were conducted to determine if a relationship exists between vitelline membrane protein banding patterns, interior egg quality, and vitelline membrane rupture strength. Eggs were gathered from commercial egg producers from pre-molt (26 wk or 72 wk) and post-molted (74 wk or 82 wk) hens. In each of two trials twenty-one eggs were gathered and stored (4?C) per experiment. Three eggs were evaluated on days 0, 7, 14, 21, 28, 35, and 42 for eggs from pre-molted hens; and 1, 7, 14, 21, 28, 35, and 42 for eggs from molted hens for changes in SDS-PAGE protein banding patterns. The yolk from each egg was isolated and rolled on a wet paper towel to remove adhering albumen. The yolk was emptied and washed. The whole membrane was placed into double deionized water and divided into two sections. The first section was the whole membrane sample and the other was separated by forceps into inner and outer membrane samples. The three sections were dissolved separately in 1% SDS/70 mM Tris/HCl, pH 6.8. Protein concentration was determined using the Lowry method and proteins separated on 4-20% gradient gel by SDS-PAGE. Protein banding patterns were analyzed using the Bio-Rad Multi-Analyst Densitometer. Reductions of VMO I and GP II occurred along with reductions in the protein bands between 60 to 100 kDa. In each of two trials, an additional one hundred forty eggs were gathered at the same time from the same flock and stored at 4?C. Twenty eggs were evaluated for quality on days 0, 7, 14, 21, 28, 35, and 42 for eggs from pre-molted hens; and 1, 7, 14, 21, 28, 35, and 42 for eggs from molted hens. Yolk index, albumen height, albumen pH, and yolk pH were determined. Vitelline membrane strength was determined using a compression anvil. Two different treatments were used on the yolk when evaluating rupture strength: 10 egg yolks with inner thin albumen layer, and 10 egg yolks rolled on wet paper towel to remove inner thin albumen layer. Interior egg quality and vitelline membrane strength declined during storage.