A20: Single fold is the concentration level set by the United States Food & Drug Administration (USFDA) for Pure Vanilla. A single fold vanilla contains the extractive matter of 13.35 oz. (379 gm.) of vanilla beans (about 100 beans each 6 7 long) containing less than 25% moisture, in one US gallon (3.79 liters) of 35% aqueous ethyl alcohol (simply put 100gms. of vanilla beans per 1 liter of 35% ethyl alcohol). This quantity must thus be adjusted pro-rata if the alcohol base used has a higher or lower percentage than 35% volume of alcohol. Two fold extract uses twice as many beans or 26.7 oz. (758gm) in the same quantity of aqueous ethyl alcohol making it twice as strong. Three and four fold is three and four times the concentration of one fold extract.