Microbial changes and aroma profile of nitrate reduced dry sausages during vacuum storage.

Slow fermented sausages with reduced ingoing amounts of sodium nitrate (control, 15% and 25% reduction) were stored under vacuum up to three months. Changes in microbiology, chemical parameters and volatile compounds were studied. Residual nitrate was not affected by vacuum storage and its reduction resulted in a reduction of sausage redness. General microbial counts decreased during vacuum storage, though nitrate reduction increased the growth of total mesophilic bacteria and Gram positive cocci. Long storage time and 25% nitrate reduction affected microbial activity and sausage aroma profile. Short vacuum storage times and moderate nitrate reduction (15%) were related to compounds producing pleasant odours (3-hydroxy-2-butanone, ethyl octanoate, ethyl-3-methylbutanoate and 2,3-pentanedione) and cheesy/buttery odour (2,3-butanedione and ethyl-2-hydroxypropanoate). In contrast, 25% nitrate reduction increased compounds like heptanal (green, unpleasant odour) and those related to unpleasant odours, methanethiol (rotten odour) and methional (cooked potato).