The primary source of emissions at a bakery is the oven, which produces Volatile Organic Compounds (VOCs) and carbon dioxide from the release of compounds formed in the yeast fermentation process.
Bread refers to yeast-leavened pan bread, rolls, buns, pretzels, sweet yeast goods such as doughnuts and Danish pastry, or similar yeast-leavened products. The basic ingredients in yeast-leavened bread are flour, water, yeast and salt. During fermentation of the dough, large starch molecules break down into simple sugars. The yeast metabolizes the simple sugars in anaerobic fermentation producing carbon dioxide, ethanol (ethyl alcohol), small amounts of other alcohols, esters and aldehydes.
The VOC that is produced during fermentation (mostly ethanol) is bound in the dough and is generally liquid at temperatures below 77° C (170° F). It is not emitted in appreciable amounts until the end of the baking process when the dough is exposed to high temperatures around 240° C (464° F)
The amount of VOC generated in yeast-leavened dough is a function of the amount of yeast added to the formula and the amount of time the yeast is allowed to ferment before the bread is baked.
Ethanol and other VOCs combine in the atmosphere to form smog and are regulated as ozone precursors under EPA’s criteria pollutant program.