At least my first post will be interesting and possibly useful...
I've read a lot of weightlifting & bodybuilding books, including a lot of old ones. I do remember someone suggesting that you make chewing motions with your protein shake in order to get some saliva going and start the digestion process. Unfortunately, I can't remember exactly where I read that right now (usually I can remember things like that). I think my grandmother used to say that too.
Here's some reference from an article here on T-Nation that covers the topic:
Bodybuilder, Heal Thyself
An Interview with Dr. Ken Kinakin
by Chris Shugart
The part about saliva & digestion says:
KK: ...What we're finding is that a lot of the proteins people eat aren't being digested.
T: Oh really? How can we fix that? Probiotics?
KK: Probiotics come later on in the chain, but the number one reason for undigested protein is that people don't chew their food.
T: As simple as that, huh?
KK: As simple of that. About 30% of digestion happens in your mouth. If you just inhale your food, it's really hard for the body to break it down. The analogy I've learned is it's a lot like buttoning your shirt. If you start one button down so it's not lined up, then it's out of whack all the way down the chain. To fix it, you have to straighten it out starting from the top.
So chew your food, and even chew your protein shakes. A lot of people just gulp this stuff down and it creates a huge glycemic rush and it's also not digested well. The digestive process is started by chewing, so chew the liquid.
T: Wait a minute, you mean to actually make chewing motions with a mouthful of protein shake?
KK: Yes, that chewing motion creates salivation within the mouth and is able to "tag" the different enzymes within the actual protein, therefore you?ll be able to break it down better. If you're a person that has gas after ingesting a protein shake, then just chew the liquid and you'll probably solve that problem. Chew it about five or six times, just enough to get the stimulation going.
T: So you're not really grinding up the protein any smaller; it's more of a Pavlovian response.
KK: Totally. It's basically a neurological response. It's no different that visualization really. You know, you think about biting into a lemon and you start to salivate. Also, most people swallow their protein powders way too fast and it's way to concentrated. The body can't always utilize it and you get bloating. People assume they got their hands on some bad protein, and maybe they did, but a lot of times they just have poor chewing habits! In fact, in Germany there's a clinic where they basically try to cure cancer by teaching people how to chew their food. They suggest chewing your food until it turns into almost a fluid; chew about 30 or 40 times.
T: Very fascinating stuff! Now what's this about people making their shakes too thick?
KK: It's like with fruit juice. You should just eat fruit so you can get the pulp, and avoid juices because of the glycemic effect on the body. But if you do have fruit juice, dilute it down 50/50. Most people have way too much protein powder for fluid. You increase the fluid amount, chew it a little bit, and it'll be a lot easier on your system and you'll get better results in the long term.