Syd G : Got a reply from my friend about protein supplement.
Well, my research back in Japan not so much utilization in the meal replacement beverages, but more of how to modify the cereal proteins enzymatically to increase the functionality by decreasing the isoelectric point (pI) of the proteins. One of the main reason why a protein is not soluble, hence limit its application is because of pI whereby the net charge of the protein = 0. So at pI, all the protein will aggregate.
My current research are actually much more related to the usage of milk protein in sport and functional beverages. However, we do not focus on those solidified beverages that sell by the direct sales company. Instead, we want to improve the heat stability of the whey protein, and increase the concentration can be used in the beverages.
Let me just give you a brief idea on milk protein, the main focus in the nutritional drink market now for increase the usage of it in their products. In milk, only about 3.25% is protein. From this 3.25% protein, 80% of them are caseins (what people generally know more about its acid or rennet coagulated form known as cheese). These caseins when naturally occur in milk, tend to group together to form casein micelles, which is the main reason why milk is "white", because the large casein micelles scattered the light.
Usually during cheese making, after cheese curd is formed, there will be large amount of liquid remained (yellowish green color) know as whey liquid, with rich potion of whey proteins in it. Few decades ago, it has been used as animal feeds or dispose away. However, nowadays, whey proteins is the "gold" in the nutritional beverages. This is because the amino acids of whey proteins have been extensively studied to possess a few good points. Just enter "benefit of whey protein" in yahoo, you will see how many information you can get about the goodie goodie of whey protein. I give you one of the link here.
http://www.wheyoflife.org/benefits.cfmWhey proteins are especially preferred by atheles because it is a "fast burning protein", which if you consume before workout, will help you to burn your body fat efficiently without losing your muscle mass.
So, many beverages companies are trying to use whey protein to produce instant drink target for different market but the problem is whey protein has low heat stability. Once it is being heated above certain temperature in certain concentration, it either aggregate or form gel. Which is my main research work now. But still, this is the main problem in the industry. If you read the nutritional label of a sport beverage, you should be able to see what is the content of the total protein in that serving, and what kind of proteins they use. Other non-milk protein that they use are soy protein concentrate or isolate, hydrolyzed protein (from gelatine, soy, milk including whey and casein) etc. But the percentage of protein still not very high, probably about 4-6% protein.
That is why they still tend to sell them in powder form. Which in your question, when some protein drink if you don't drink, will solidify, I believe it is not because of the protein action, but the side ingredient, namely hydrocolloids that are used, commonly including carrageenan, pectin etc. Some hydrocolloid do not need to be in hot water to thicken. These hydrocolloids when inside water, will interact the water to from very thick paste like texture, not going to give any harm to the body but not nutritionally significant too. But they will fill up your stomach, which is why you feel full after that.
Half the info is what you know already. But interesting to see where the drinks industry is going with whey protein.