Spoilage-related activity of Carnobacterium maltaromaticum strains in air-stored and vacuum-packed meat

Abstract

One hundred three isolates of Carnobacterium spp. from raw meat were analyzed by random amplification of polymorphic DNA (RAPD) and PCR and were identified by 16S rRNA gene sequencing. Forty-five strains of Carnobacterium maltaromaticum were characterized for their growth capabilities at different temperatures, NaCl concentrations, and pH values and for in vitro lipolytic and proteolytic activities. Moreover, their spoilage potential in meat was investigated by analyzing the release of volatile organic compounds (VOCs) in meat stored in air or vacuum packs. Almost all the strains were able to grow at 4, 10, and 20°C, at pH values of 6 to 9, and in the presence of 2.5% NaCl. The release of VOCs by each strain in beef stored at 4°C in air and vacuum packs was evaluated by headspace solid-phase microextraction (HS-SPME)-gas chromatography-mass spectrometry (GC-MS) analysis. All the meat samples inoculated and stored in air showed higher numbers of VOCs than the vacuum-packed meat samples. Acetoin, 1-octen-3-ol, and butanoic acid were the compounds most frequently found under both storage conditions. The contaminated meat samples were evaluated by a sensory panel; the results indicated that for all sensory odors, no effect of strain was significant (P > 0.05). The storage conditions significantly affected (P < 0.05) the perception of dairy, spoiled-meat, and mozzarella cheese odors, which were more intense in meat stored in air than in vacuum packs but were never very intense. In conclusion, different strains of C. maltaromaticum can grow efficiently in meat stored at low temperatures both in air and in vacuum packs, producing volatile molecules with low sensory impacts, with a negligible contribution to meat spoilage overall.

Fig. 1.

Similarity dendrogram generated by RAPD-PCR fingerprints. A combined data matrix of all the fingerprints was defined, and the similarity dendrogram was obtained by using the UPGMA (unweighted-pair group method using arithmetic means) clustering algorithm (43). The strain designations and times of isolation are given on the right (0, beef at time zero; 7, beef after 7 days of storage at 4°C; 20, beef after 20 days of storage at 4°C).

Fig. 2.

Total ion current chromatograms obtained by HS-SPME-GC-MS analysis for meat samples contaminated with C. maltaromaticum D1203 and L171. The contaminated meat samples had initial viable counts of 10⁴ CFU g⁻¹ on CTSI agar, and the load increased to 10⁷ CFU g⁻¹ after 1 week of incubation at 4°C both in air and under a vacuum (Table 1). (A) D1203 after 7 days of storage in air; (B) D1203 after 7 days of storage in a vacuum pack; (C) L171 after 7 days of storage in air; (D) L171 after 7 days of storage in a vacuum pack. The numbers given alongside the spectra correspond to the different compounds detected, as follows: 1, thiophene; 2, acetoin; 3, 3-methyl-1-butanol; 4, butanoic acid; 5, 1-hexanol; 6, 2-heptanone; 7, dimethyl sulfide; 8, benzaldehyde; 9, heptanol; 10, 1-octen-3-ol; 11, 3-octanone; 12, 2-pentylfuran; 13, hexanoic acid; 14, 2-ethyl-1-hexanol; 15, 2-ethylthiophene; 16, 1-octanol; 17, 2-octenal; 18, 2-octen-1-ol; 19, nonanal; 20, phenylethyl alcohol; 21, 3,5-dimethylbenzaldehyde; 22, decanal; 23, 4-methylthiophenol; 24, 3-phenoxy-1-propanol; 25, tridecanol; 26, tetradecanal.

Fig. 3.

Similarity dendrograms based on quantitative data for VOCs detected in meat inoculated with 45 strains of C. maltaromaticum. (A) C. maltaromaticum strains after 7 days of storage in air at 4°C. (B) C. maltaromaticum strains after 7 days of storage in vacuum packs.

Fig. 4.

Mean odor intensities (± standard errors) of samples stored in air and in vacuum packs. Both the means and the standard errors were calculated across all the samples (n = 10).