<P> The two main categories of yeast used in tequila are commercial brewers yeast and yeast that comes from precultivated existing yeast that has been preserved . The use of either type of yeast can result in different end products of tequila . </P> <P> Tequila is a distilled beverage that is made from the fermentation of the sugars found from the blue agave plant once it has been cooked, the main sugar being fructose . Through the fermentation process, many factors influence the higher alcohol content of tequila, which are molecules such as isobutyl alcohol and isoamyl alcohol, and ethanol . These parameters include the type of yeast strain, the age of the agave plant itself, temperature, and the carbon / nitrogen ratio . However, the type of yeast strain used and the carbon / nitrogen factors have the biggest influence on the production of higher alcohols, this is not surprising as higher alcohol and ethanol production is an intrinsic property of the metabolism of each strain . The type of yeast most commonly found in tequila is Saccharomyces cerevisiae, which contains many strains . For example, CF1 agaves, a type of yeast, produces much more ethanol than a strain of CF2, as the yeast's metabolism mechanisms differ from one another . This factor may be influenced from different agricultural practices that occur to cultivate the different yeasts strains . It was found that the higher the carbon / nitrogen ratio, the higher the production of higher alcohols such as isobutyl alcohol and isoamyl alcohol . A high ratio imparts that there is less nitrogen in the fermentation process, which results in deamination reactions of amino acids, leading to the synthesis of higher alcohols . The Ehrlich pathway is the name for this process, where a-ceto acids are decarboxylated and transformed to aldehydes and to higher alcohols . The temperature of the fermentation process also greatly effects the alcohol content of the resulting product . For example, a study conducted by Pinal et al. found that cultivating two strains at a temperature of 35 degrees as compared to a temperature of 30 degrees produced more isoamyl alcohol . The higher temperature suggests that this is a much more optimal condition for the yeast to ferment the distilled beverage . Lastly the age of the agave plant itself, the older the plant the greater the alcohol production . It was shown in a study that the concentration of amyl alcohol increased as the plant aged by a factor 30% . However, it is also found that there is a higher concentration of methanol found when using younger plants . This may be due to differences in agricultural practices that occur when taking care of plants of different ages . </P> <P> Tequila comes in an abundant array of colors that ranges from a simple clear distilled beverage to a dark amber brown . The color of the tequila varies greatly on the aging process and the type of wood used for storage . The white version of tequila, known as silver tequila or blanco, is the product obtained without or very little additional aging process . As well, the spirit must contain between 38 - 55% alcohol content, which is fermented from a wort, which contains no less than 51% sugars from the agave plant . Consuming silver tequila provides for the purest form as little aging has occurred . What is known as gold, joven or oro tequila is usually silver tequila with the addition of grain alcohols and caramel color, however, some higher end gold tequilas may be a blend of silver and reposado . Rested (reposado) or aged tequila (añejo) are aged in wooden containers . The aging process can last between two months and three years and can create or enhance flavors and aromas . The aging process generally imparts a golden color . </P> <P> There are more than 300 known compounds in tequila, many of which are produced during the fermentation process, the raw material used, and to a lesser degree, during the maturation . The components that make up tequila do not act individually to give tequila its distinctive flavor and aroma, but rather, depends on the interaction and quantity of each volatile compound . The volatile compounds responsible for the flavor and aroma profiles of the tequila are put into a category called organoleptic compounds and are known to increase in concentration with a slower fermentation process . The organoleptic compounds produced during fermentation include higher order alcohols, methanol, esters, carbonyls, terpenes, and furans . </P>

What's the difference between blanco and reposado
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