How fermentation makes flavor
Fermentation is microbes eating sugar and leaving products behind. Yeast make alcohol and carbon dioxide. Lactic acid bacteria make lactic acid. Acetic acid bacteria turn alcohol into acetic acid. Tangy, boozy and fruity flavors all start as microbe leftovers.
Esters smell fruity
Alcohols and acids can combine into esters, which often smell fruity. Isoamyl acetate smells like banana and shows up in some beers brewed with certain yeasts. No banana is involved. The yeast make the compound.
Test yourself
Questions from the interactive lesson, with the answer and the why.
True or false: Vinegar forms when yeast turn sugar straight into acetic acid.
False. Yeast make alcohol first. Acetic acid bacteria then turn it into acetic acid when oxygen is present.
Why does sourdough smell and taste tangy?
Starter bacteria make lactic and acetic acids. Those acids give sourdough its tang, while the yeast make it rise.
What went wrong? You pack shredded cabbage with salt but leave some above the liquid. Fuzz grows on the exposed bits.
Cabbage above the brine met air. Keeping it submerged favors lactic acid bacteria, which don't need air.
Fill the blank: Banana-like and pear-like aromas in beer and wine often come from fruity ___ made by yeast.
Banana-like and pear-like aromas in beer and wine often come from fruity esters made by yeast. Esters form from acids and alcohols and smell fruity.
True or false: The funky smell of some aged cheeses comes from real compounds that microbes produce.
True. Microbes produce volatile acids and sulfur compounds that give aged cheeses a sharp, funky smell.
