Abstract: In order to study the effect of microbial fermentation on the formation and change of flavor substances in air-dried sausages, commercial mixed-strain starters SHI-59 (Staphylococcus xylose, Pediococcus pentosaceus, and Lactobacillus plantarum), WBL-45 (S. xylose, S. botulinus, and L. sake) and PRO-MIX5 (S. xylose, L. sake, and L. plantarum) were inoculated separately into minced meat and after 12 days of air drying, fermented air-dried sausages were produced and denoted as SHI, WBL and PRO, respectively, and a non-inoculated sample was used as a control. Samples subjected to air drying for 6 and 12 days were analyzed for the content of free amino acids. The flavor changes of air dried sausages during the air drying process were determined by a Heraclesii ultra-fast gas chromatography electronic nose, an electronic tongue and gas chromatography-mass spectrometry (GC-MS). The results showed that as the air drying time increased from six to 12 days, the total amount of free amino acids significantly increased, and the total amounts of free amino acids in SHI, WBL and PRO were 2 409.78, 2 317.74 and 2 655.18 mg/100 g, respectively, significantly higher than that in the control group (2 137.82 mg/100 g) (P < 0.05). The four groups of samples could be clearly distinguished in terms of their smell and taste. The flavor richness of PRO was the strongest, followed by SHI and WBL, which had similar smell and taste, and the control group had the smallest flavor richness. Totally 80, 79, 76 and 83 volatile flavor substances were detected in the control, SHI, WBL and PRO groups, respectively. Esters, aldehydes, alcohols, acids and heterocyclic compounds were the major flavor substances of air-dried sausages. The percentages of esters in SHI (20.6%), WBL (24.13%) and PRO (21.71%) were higher than that in the control (19.13%) group, and the ester content of SHI was the highest (2 271.62 μg/kg). (E,E)-2,4-Nonadienal and 3-methylbutyric acid made the greatest contribution to the flavor of the control and SHI groups. SHI and WBL contained heptanaldehyde with an odor activity value (OAV) greater than 1, responsible for the fruit flavor, while ethyl butyrate (OAV > 1), responsible for the pineapple-like aroma, was unique to PRO. The results showed that the application of PRO-MIX5 was more conducive to improve the flavor and taste of air-dried sausage compared with the other commercial starters.

Key words: microbial starter; air-dried sausage; amino acids; electronic tongue; electronic nose; gas chromatography-mass spectrometry