Here in the US packaged products have labels with that info. 240 ml of milk has 8 grams of protein. I did a search at www.google.com and used the term:
soya beans + protein
and found this site where you can get more info on soya beans at the bottom of the page. http://www.vegsoc.org/info/soya.html
You could do the same search for meat or maybe look at a package of prepared hamburger to see how much protein is in it and do the math.