 As the chestnuts ripen, the starch is slowly converted into sugars, and moisture content decreases.Upon pressing the chestnut, a slight 'give' can be felt; the hull is not so tense, and space occurs between it and the flesh of the fruit.They are the only "nuts" that contain vitamin C, with about 40 mg per 100 g of raw product, about 65% of the US recommended daily intake.