The commercial growing of mung beans is done in large vats.In order to speed up the growing process they pump in a gas that ripens them quickly.Thats why they look like they are turned inside out.I grow mung beans and have found that they are best when 2-3 days when they have a small tail.I have grown them for 7 days and they get huge and are very tough and chewy with a very blah taste.I must admit when I first grew mung beans and tasted them there was a moment of ah crap these dont taste anything like the ones from the store.But the control factor of how they are grown and how much cheaper they are to grow yourself makes it worthwhile.You might want to check out sproutpeople.com for more info. on the art of sprouting.I have some pics. of my sprouting in the Image Gallery in the photos section under grassmans sprouts.Happy sprouting.Jeff.