9 month old...behavior while eating solids?

My 9 month old baby has recently started something new while eating solids. It looks as if she's holding her breath and trying to p gas. It makes her face beat red and she looks extremely uncomfortable. At first, I thought she was hooking her foot under the tray of the high chair and pushing, but I've been watching her and that's not it as she fits very comfortably in the high chair. She's doing this with every meal and I can't figure out why...we haven't changed any of her foods or juice. I've tried taking her out of the high chair and burping her when she does this, but I get nothing. Could she be eating too fast or taking too much at a time? We haven't changed the pace of her feedings or the amount so I don't know why she'd have an issue with those now. She's definitely hungry and 'panting' for more but just seems uncomfortbale. Her face gets beat red and it's kinda scary! Any ideas?