The film-forming solution was prepared by dissolving a mixture
of starch and gelatin (2.5 g) with 30 wt% of glycerol in 50 ml
of distilled water. Potato starch was dissolved in 50 ml of distilled
water at 90 ◦C for 10 min in concentration ϕ varied from 0 to 50 wt%
with an increment of 10 wt% from gelatin/starch blend. Cheng et al.
(2010) have showed that ultrasonic treatment strongly affects the
dissolution of starch, thus reducing size of its aggregates. That is
why, the solution was sonicated in an ultrasonic bath 7/100-TH
(Reltek, Russia) at 60 ◦C for 25 min, and afterwards glycerol was
added to the solution. When starch and glycerol formed a homogeneous
solution, gelatin was added followed by sonication at 60 ◦C
for 50 min. Next, prepared solution was poured outinto Petri dishes
and kept at 36 ◦C for 15 h in a drying oven UT-4620 (Ulab, Russia)
with air convection.