Studies on the stability of chicken IgY in different sugars, complex carbohydrates and food materials

The effect of non-reducing sugars (sucrose, lactose and trehalose), complex carbohydrates (cyclodextrin and dextran), infant formula or egg yolk on the stability of purified chicken IgY was evaluated under different conditions. Regardless of the protectant that was used, about 20% of the activity of IgY was lost during freeze-drying except in the presence of infant formula where the loss of IgY activity was approximately 75%. The lowest loss of activity (10%) was observed when no protectant was used. Trehalose was the best protectant followed by cyclodextrin and infant formula when IgY was stored for 6 or 14 weeks at different temperatures. Sucrose, lactose and dextran were not effective as protectants under these conditions. IgY activity was completely lost after pepsin treatment in the presence of sugars or complex carbohydrates while 34 and 40% of its activity was recovered when treated in the presence of infant formula and egg yolk, respectively. IgY was fairly stable after trypsin treatment with the recovery of residual activity being between 75-100% depending on the protectant. Finally, the effect of heat treatment on the stability of aqueous solutions of IgY was evaluated. IgY was stable at 50, 60 or 70 degreesC while complete loss of IgY activity was observed at 80 and 90 degreesC in the presence of all protectants except infant formula and egg yolk were about 5% residual activity was observed. These results demonstrate that the addition of different compounds to IgY during freeze-drying or storage at different temperatures or subjecting them to enzyme treatments provided varying and in most cases considerable protection against loss of biological activity.