Cooking Ginseng

Wang Ming did just as he had planned. He rinsed and washed one ginseng, then crushed it up before boiling it in water. While boiling it, he put a lid on the pot tightly so it wouldn't release too steam, as the steam could also contain nutrients. He only let a bit of steam out whenever he had to, to ensure most nutrients stay in the pot.

After 30 minutes most of the water had evaporated, leaving only a mushy ginseng and murky water. Though looking at the water made Wang Ming realize something, he didn't know if the process had done its job. How could he know if the nutrients in the water are more than what he would get from cooking the ginseng normally? What if the steam had evaporated most of the nutrients?