Structuring role of yolk and albumen in fresh egg pasta

Commercial formulations of fresh egg pasta widely vary in terms of egg content, ranging from 17 to 30%. Besides, some products are manufactured with whole egg products enriched in yolk. The aim of the work was to evaluate the influence of total egg content and albumen to yolk ratio on fresh egg pasta structural characteristics. To study the effect of the two factors considered (egg amount and albumen to yolk ratio) simultaneously, a Central Composite Design was developed. Pasta samples were produced as sheets for lasagna, using 1:1 wheat flour to semolina and keeping moisture to a constant level. Whole egg ranged from 14.7 to 30.3% and albumen to yolk ratio between 0.18 and 5.82. The analysis of effects showed a significant influence of experimental factors on pasta composition (proteins and lipids) and structure. In particular, the egg amount had a positive effect on break load of cooked pasta (p<0.01), while albumen to yolk ratio positively affected break load of both raw (p<0.05) and cooked (p<0.01) pasta, as well as Young modulus of cooked pasta (p<0.05). These results demonstrate the structuring capacity of whole egg in fresh egg pasta, thus suggesting the possibility to modulate pasta texture by modifying egg content and/or albumen to yolk ratio. In particular, the kind of egg proteins in the dough plays an important role since pasta structural improvement seems related to ovalbumin content. Actually, this protein bears four free thiol groups, able to interact between themselves and with the other SH groups of flour proteins to form a tighter network during mixing and cooking. The relevant role of ovalbumin was assessed by SDS-PAGE analysis of pasta proteins solubilised in different media. On the contrary, yolk content especially affected pasta cooking behaviour; being directly correlated (p<0.05) with pasta weight increase during cooking. This effect can be related with the development of weaker gluten network, probably due to yolk proteins and lipids.