Effect of MAP on physico-chemical characteristics of shell hen eggs

MAP has become a widely used food preservation technique, which minimally affects fresh product characteristics, receiving better consumer perception as a natural and additive free techniques. To our knowledge, little data is available in literature regarding the influence of MAP on the shelf-life of packed whole eggs. The aim of this study was to compare some physico-chemical and technological properties of not packed eggs (control) with eggs packed in high barrier plastic pouches with three different atmospheres (air, 100% N2, 100% CO2) during 28 days of storage at 25°C. One day after laying just before packaging and after 1, 2, 4, 8, 15, 21 and 28 days of storage the following determinations were carried out: weight loss and water content, pH, aw, Haugh index (HI), albumen foam stability and texture profile analysis of cylinders of coagulated albumen. MAP was effecting in the reduction of water loss of albumen and of water gain of yolk, while it did not affect aw. As expected, the albumen of control sample showed a constant increase of pH (from about 9 to 10 at the end of storage) because of the loss of CO2 due to its diffusion through the shell pores. Samples packed in air and in 100% N2 did not exhibit this pH increase for all the storage period while the albumen of 100% CO2 eggs showed a rapid reduction of pH reaching values of about 7 after 8 height day of storage. This phenomenon was responsible of the better maintenance of the HI value of sample packed in 100% CO2 compared with samples packed in air and in 100% N2 and with the control one, that showed the most rapid decrease of this parameter. In addition, the foam obtained using the egg white of CO2 sample was about 10 times more stable than the others. Surprisingly thermal coagulation of the albumen of this sample promotes the formation of a very alveolar and soft coagulated structure. From an industrial point of view, the application of this technology (e.g. with controlled atmosphere storage) could permit the substitution of more artificial, complicated, and expensive process commonly applied to change the albumen pH in order to improve the quality characteristics of albumen based products. In the optic of fresh shell eggs commercialization, modified atmosphere packed eggs could represent a tailored innovative food product, with specific characteristics bound to its destination (e.g. fresh shell eggs special for whipping ).