Physicochemical property, volatile flavor quality, and microbial community composition of Jinhua fatty ham and lean ham: A comparative study

Abstract

The physicochemical property, volatile flavor compounds, and microbial community structure of Jinhua fatty ham (FH) and lean ham (LH) were investigated and compared by high-throughput sequencing and HS-GC-IMS. Results showed that FH had higher pH and slightly lighter and yellower color than LH. Meanwhile, 33 volatile flavor compounds were identified from FH and LH, among which LH showed higher abundance of total alcohols and acids, but FH had generally richer aldehydes, ketones, esters, heterocyclic, and sulfur-containing compounds. Moreover, FH and LH did not have significant difference in α-diversity of bacterial community, but LH presented a much lower α-diversity of fungal community than FH. Besides, the dominant microorganisms (relative abundance >2%) in FH were Ruminococcaceae UCG-005, Staphylococcus, Ruminococcaceae UCG-014, Meyerozyma, and Aspergillus at the genus level, while in LH were Staphylococcus, Psychrobacter, Halomonas, Propionicicella, Ruminococcaceae UCG-005, Meyerozyma, Yamadazyma, and Aspergillus. Furthermore, the analysis of Pearson's correlation and metabolic network confirmed that the discriminative flavor compounds of FH were mainly β-oxidation and degradation products of fatty acids, while those of LH were mostly derived from the Strecker reaction or microbial metabolism of amino acids. The present study could help understand the potential pathway of characteristic microorganisms affecting flavor formation of fat-deficient dry-cured hams and provide theoretical supports for developing healthier fermented meat products.

Keywords: GC-IMS; Jinhua ham; bacterial community; fatty ham; fungal community; high-throughput sequencing; lean ham; volatile flavor compound.

Figure 1

Comparison of volatile flavor compound intensities of Jinhua FH and LH in different chemical families. Different lowercases above the error bar denote significant differences between Jinhua FH and LH (p < 0.05). FH, fatty ham; LH, lean ham. Log₁₀ P is the logarithmic value of total intensity for compounds of each chemical family in HS-GC-IMS spectra.

Figure 2

Comparison of volatile flavor profiles of Jinhua FH and LH with two-dimension HS-GC-IMS spectra. FH, fatty ham; LH, lean ham.

Figure 3

Gallery plot of characteristic flavor finger-print of Jinhua FH and LH determined by HS-GC-IMS. FH, fatty ham; LH, lean ham.

Figure 4

Bacterial community structure of Jinhua FH and LH at the phylum, genus, and species levels. (A) Relative abundance at the phylum level. (B) Relative abundance at the genus level. (C) Heatmap of HCA for the relative abundance of main species (top 20). The color gradation in panel C represents the Z-scores of corresponding relative abundances. FH, fatty ham; LH, lean ham.

Figure 5

Fungal community structure of Jinhua FH and LH at the phylum, genus, and species levels. (A) Relative abundance at the phylum level. (B) Relative abundance at the genus level. (C) Heatmap of HCA for the relative abundance of main species (top 20). The color gradation in panel C represents the Z-scores of relative abundances. FH, fatty ham; LH, lean ham.

Figure 6

Pearson’s correlations (A) and potential pathways (B) between differential core microorganisms and distinct volatile flavor compounds. The color gradation and circle size in panel A represent the correlation coefficient (r value), while the pattern without a “×” symbol indicates a significant correlation (p < 0.05). The green and red arrows in panel B indicate an up-regulation in FH and LH, respectively. A1, n-nonanal; A2, phenylacetaldehyde; A3, benzaldehyde; A4, pentanal; A5, 2-methylbutanal; A6, 3-methylbutanal; A7, 2-methylpropanal; B1, 3-octanone; B2, 6-methyl-5-hepten-2-one; B3, 2-octanone; B4, 2-heptanone; B5, 3-hydroxy-2-butanone; B6, 2-butanone; B7, acetone; C1, 1-octen-3-ol; C2, 1-pentanol; C3, ethanol; C4, 2-propanol; C5, 1-hexanol; C6, 3-hexen-1-ol; C7, 3-methyl-1-butanol; D1, ethyl acetate; D2, butyl acetate; D3, butyl propanoate; E1, isovaleric acid; E2, 2-methylpropanoic acid; F1, 2-pentylfuran; G1, dimethyl disulfide; M, monomer; D, dimer.