High pressure processing improves the texture quality of fermented minced pepper by maintaining pectin characteristics during storage.

Texture quality affects the sensory and market acceptance of fermentation minced pepper (FMP), but it will deteriorate during storage. Thus, high pressure processing (HPP) and thermal pasteurization (TP) were used to improve the texture quality of FMP during storage. The results showed that variations in texture quality and pectin characteristics under HPP and TP treatments were similar during storage. The hardness, cell wall material (CWM) and sodium carbonate-soluble pectin (SSP) content, water-soluble pectin (WSP) molecular weight (Mw ) decreased, while WSP content and sodium chelate-soluble pectin (CSP) Mw increased after storage. HPP-treated FMP showed higher hardness (66.64-85.95 N) than that in TP-treated one (57.23-62.72 N) during storage. Rhamnose (Rha), arabinose, mannose, and glucose were the crucial compositions in three pectins, and their total molar ratios, respectively, reached 89.19% and 87.97% after HPP and TP treatment. However, the molar ratio of most monosaccharide in three pectins decreased after storage. Atomic force microscope images indicated the short chains and branch structures increased but aggregates decreased in most pectin components during storage. Pearson correlation analysis demonstrated FMP hardness was extremely (p < 0.01) positively correlated with CWM and SSP content, and extremely (p < 0.01) negatively correlated with WSP content. Compared to TP treatment, HPP presented higher hardness, SSP content and Mw , Rha content, CSP Mw , and lower WSP content during storage. Hence, HPP was an effective method to improve the texture quality of FMP by maintaining pectin characteristics during storage. PRACTICAL APPLICATION: Softening is one of the main factors affecting market value and consumer preferences for FMP, and it is closely related to the modification and depolymerization of pectin. Changes of texture quality and pectin properties in HPP- and TP-treated FMP during storage were assessed, including hardness, the content, monosaccharide compositions, Mw distribution, and nanostructure of WSP, SSP, and CSP. Compared to TP treatment, HPP could effectively improve the texture quality of FMP by inhibiting pectin degradation during storage. All the findings presented in this study would help to provide new insights into regulating the texture quality of FMP.

Gas Chromatography-Mass Spectrometry Metabolite Analysis Combined with Transcriptomic and Proteomic Provide New Insights into Revealing Cuticle Formation during Pepper Development.

The cuticle plays an important role for the quality of pepper fruit. However, the molecular mechanism of cuticle formation in pepper fruit remains unclear. Our results showed that the wax was continuously accumulated during pepper development, while the cutin monomer first increased and then decreased. Hexadecanoic acid and 10,16-hydroxyhexadecanoic acid were the main components of wax and cutin, respectively. Combined with transcriptome and proteome, the formation patterns of wax and cutin polyester network for pepper cuticle was proposed. The 18 pairs of consistent expression genes and proteins involved in cuticle formation were revealed. Meanwhile, 12 key genes were screened from fatty acid biosynthesis, biosynthesis of unsaturated fatty acids, fatty acid elongation, cutin, suberine, and wax biosynthesis, glycerolipid metabolism, and transport pathway. This study would provide important candidate genes and theoretical basis for the molecular mechanism of cuticle formation, which is essential for the breeding of peppers.

Characteristic fingerprints and volatile flavor compound variations in Liuyang Douchi during fermentation via HS-GC-IMS and HS-SPME-GC-MS.

The present study investigates volatile organic compound (VOC) compositional changes in Liuyang Douchi during fermentation via a HS-GC-IMS and HS-SPME-GC-MS combination approach. A total of 115 VOCs were identified from Douchi, most of which were accumulated during pile fermentation. Notably, most alcohols and acids decreased with fermentation, while esters, ketones, pyrazines, and phenols accumulated during pile fermentation. Depending on the VOCs identified by GC-IMS/MS, the different fermentation stages of Douchi could be facilely distinguished. Of these, 49 VOCs were regarded as the marker VOCs of Douchi in different fermentation stage: hexanol, hexanal, and propanoic acid was the marker VOCs of the black beans before fermentation and contributing beany and grassy odors; 1-octen-3-ol and 3-octanone supplying a mushroom aroma to the Douchi fermented for 3-9 days; and esters and pyrazine, especially ethyl acetate and 2,6-dimethylpyrazine, contributing the cocoa, fruity, and nutty aromas of matured Douchi.

Illumina MiSeq sequencing reveals microbial community succession in salted peppers with different salinity during preservation.

Chopped pepper is one of the traditional fermented pepper products in China. At present, the industrial production method is mainly to preserve the peppers with high salt about 1 year, and then make the product after desalination and seasoning when it is processed. However, the composition and succession of the bacterial community involved in the long-term preservation of salted pepper was complex. In this study, Illumina Miseq sequencing technology was used to reveal the succession in the bacterial community structure of different salted pepper within 10 months of preservation. The results showed that Firmicutes and Proteobacteria were dominant bacteria in all samples at the Phylum level. At the Genus level, among fresh unsalted capsicum, Fructobacillus (44.66%), Enterobacteriaceae unclassified (26.78%), Leuconostoc (12.04%) and Lactococcus (8.45%) had relatively high abundance. Enterobacteriaceae unclassified, Lactobacillus, Marinospirillum and Halomonas were identified as the main dominant bacteria in the samples with 6%-12% (w/w) salinity, and Enterobacteriaceae unclassified mainly appeared in the early stage of preservation. In 15% and 18%(w/w) salinity samples, with the increase of preservation time, the dominant genus was changed from Enterobacteriaceae unclassified to Chromohalobacterter, Tetragenococcus, Halomonas, Halovibrio, etc., while the relative abundance of Lactobacillus remained at an extremely low level. The bacterial structure of 6% (w/w) salinity samples changed significantly during preservation, while the distribution in PCoA analysis of salinity samples of 9% was similar to that of 12%. In the high-salinity samples (15%-18%), the composition of the community was highly similar in 0-6 months, but the composition changed significantly with the increase of the preservation time and the growth of halophilic bacteria (p < 0.01). Pearson correlation analysis was used to investigate that Lactobacillus exhibited a negative correlation with salinity (p < 0.01). And the salinity had a positive correlation with both the species richness and evenness in the samples, which might be the key factor for the change of the microbial community.