Physical-mechanical modifications of the eggs for foodprocessing during storage and post-refrigeration

The attitude of the yolk to remain separated from the albumen is an important aspect for the shelling process. Eggs can be stored for several months and processed some days after pulling out from the refrigerated cell. In the present research, eggs for food-processing of two genetic types of hens are stored for seven months at 0°C. During this time the parameters describing the strength of the vitelline membrane-yolk system were measured together the main egg quality parameters such as height of the thick albumen, Haugh and yolk indices. Measurements were carried out to assess the effects of different post-refrigeration treatments: eggs were analysed immediately after pulling out from the cell, after 5-6 h, when the temperature of 18°C is reached, and after further seven days at 18°C. Multiple regression statistical models were given to evaluate the influence of the different parameters considered in the study. According to these models, about seven months of storage at 0°C cause a decrease in the maximum force absorbed by the membrane-yolk systems of 10-12% while the permanence of the eggs outside the cell for seven days before processing causes a decrease of 14- 17%. The decrease in maximum force for the eggs after 5-6 h outside the cell is 4-5% if compared with the eggs analysed immediately after refrigeration. About seven months of storage at 0°C cause a decrease in the rupture energy of 14-17% and seven days at 18°C after refrigeration involve a decrease of 5-7%. After seven months of storage at 0°C it was observed a decrease in the Haugh index of 6–8 % only. The differences in force and energy of the membrane-yolk system measured after laying for the two genetic types of hen decrease during storage and post-refrigeration time.