Abstract: To test the feasibility of inoculated fermentation with lactic acid bacteria for improving the quality of fermented beef-soybean paste, samples prepared by natural and inoculated fermentations with Lactobacillus plantrum (Lp), Pediococcus pentosaceus (Pp) or their mixture (Lp:Pp = 1:1) were comparatively evaluated for their physicochemical properties, free amino acid composition and volatile flavor composition. The results showed that compared with natural fermentation, inoculated fermentation with lactic acid bacteria decreased the pH, amino nitrogen and total free amino acid contents, and increased the total acid and reducing sugar contents as well as the number and amount of volatile flavor substances in the paste. The Lp-Pp fermented paste contained the largest number (16) of ester compounds. By calculation of relative odor activity value (ROAV) as well as using orthogonal partial least squares-discriminant analysis (OPLS-DA), it was found that inoculated fermentation with lactic acid bacteria changed the composition of key volatile flavor compounds in the paste, with Lp-Pp inoculation promoting the generation of ethyl octanoate, isovaleraldehyde, benzaldehyde and phenylacetaldehyde, thereby contributing to the good flavor of the paste. Collectively, this study provides a theoretical basis for the production of quality fermented beef-soybean paste inoculated with lactic acid bacteria.

Key words: composite fermented soybean paste; lactic acid bacteria; inoculation; quality; key flavor substances