Abstract: Changes in the quality and protein conformation of semi-dried beef jerky during fermentation with Lactobacillus sakei were investigated. The moisture content, moisture distribution, pH, water activity, shear force and sensory quality of the samples were determined. Besides, in order to examine the quality differences, principal component analysis was conducted on the data from 10 electronic nose sensors. The effect of fermentation time on the protein conformation of semi-dried fermented beef jerky was studied by Raman spectroscopy. The results showed that the pH and water activity decreased with the increase in fermentation time and reached the minimum at 60 h. The shear force decreased first and then increased during the fermentation process, and reached its minimum at 24 h. The moisture content decreased first and then gradually remained stable. After fermentation, the content of immobilized water decreased whereas the content of bound water increased. The sensory scores for color, flavor, chewiness and overall quality of semi-dried beef jerky fermented for 36 h were significantly higher than those at other fermentation times. Electronic nose analysis showed that esters, alcohols and other volatile compounds were produced during fermentation, imparting a unique flavor to the product. By analyzing the Raman spectra, it was found that the relative contents of α-helix and t-g-t conformation were the lowest at 48 h of fermentation, and the protein stability of the product decreased after fermentation. Comprehensive analysis reveals that L. sakei can be used as a starter culture for semi-dried fermented beef jerky, and the fermentation time should be controlled within the range of 24–48 h.

Key words: Lactobacillus sakei; semi-dried fermented beef jerky; quality; electronic nose; Raman spectroscopy