Origin of Aroma Compounds

A great majority of the aroma compounds produced in fermented foods result from the activity of microorganisms. They derive from the conversion of food constituents via a series of biochemical reactions mainly catalyzed by microbial enzymes, although some of the enzymes either present in the raw material or added during food processing also have a role in the transformation. A few non-enzymatic reactions also occur, but they involve some coirpounds of microbial origin. 

LAB of Fermented Foods and their Role in Flavor Formation 

LAB are the most important bacteria used in food fermentations and many LAB species are involved. Their presence results from either a natural, spontaneous contamination derived from the raw materials themselves or the environment, the inoculation by foods from a previous batch (a practice referred to as back slopping), a dehberate addition of cultures (starters), or a combination of these different sources (Table 19.2). Most fermented foods consumed in developing countries are manufactured from spontaneous fermentation, without addition of any starters (Tamang and Delwen 2010). However, food fermentations have evolved towards a systematic use of starters to control fermentation, and nowadays starter cultures are widely used in the manufacture of many fermented products, such as dairy products, sourdough, and fermented dry sausages (Leroy et al. 2006). 

Dairy products in which they are flavor compounds LAB species 

Hexanoic acid (caproic acid) F popcorn, goaty goat cheese 

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