Effect of red pepper (Zanthoxylum bungeanum Maxim.) leaf extract on volatile flavor compounds of salted silver carp

Comprehensive lipidomics and flavoromics reveals the accelerated oxidation mechanism of fish oil from silver carp (Hypophthalmichthys molitrix) viscera during heating

This study employed gas chromatography-mass spectrometry (GC-MS) and lipidomic approaches to analyze volatile organic compounds (VOCs) and lipid dynamics in silver carp visceral fish oil during accelerated oxidation at 60 °C. The lipidomic profiling revealed 1362 distinct lipid molecules, encompassing 92 fatty acids. Triglycerides (TGs) underwent degradation in the early oxidation phase (0-6 days), whereas glycerophospholipid breakdown dominated the later stages (9-20 days). Among 44 detected VOCs, six compounds including nonanal, (E,E)-2,4-heptadienal, (E)-2-nonenal, (E)-2-decenal, 1-octen-3-ol, and eugenol were identified as critical flavor contributors based on odor activity values (OAV) exceeding 1.0. Notably, 1-octen-3-ol and (E)-2-decenal were hypothesized to derive from phosphatidylethanolamine (PE), TG, and ceramide (Cer) degradation. Key lipid classes linked to flavor deterioration included PE with odd-chain and unsaturated fatty acids (UFAs), TG rich in polyunsaturated fatty acids (PUFAs), and Cer containing monounsaturated fatty acids (MUFAs). These insights enhance mechanistic understanding of oxidative flavor changes in fish oils.

Deodorization mechanism of the main aroma compounds on the fishy odor in boiled fish during heating

A boiled fish simulation system was constructed to explore the deodorization effect of main aroma compounds (MAC) on myofibrillar protein (MP) with main fishy compounds (MFC) during heating. The results showed that the MFC content of boiled fish was reduced by 63.10-78.10 % when boiled by heat-stable emulsions loading MAC. Specifically, adding linalool, anethole, and myrcene significantly elevated the free percentage of hexanal, heptanal, and 1-octen-3-ol after heating, while the free percentage of octanal and nonanal markedly increased by adding anethole and limonene. Molecular docking exhibited that MAC and MFC possessed co-binding sites with myosin. Linalool and anethole were competitively bound to MP through hydrophobic and hydrogen bonding sites, while myrcene and limonene were via hydrophobic interaction sites. Moreover, MAC-MP formed a relatively stable structure, exhibiting increased α-helix content and decreased surface hydrophobicity, which reduced the available sites for MFC binding, ultimately desorbed MFC (65.46 %-95.89 %).

An Evaluation of the Effects of Pepper (Zanthoxylum bungeanum Maxim.) Leaf Extract on the Physiochemical Properties and Water Distribution of Chinese Cured Meat (Larou) During Storage

In this study, pepper (Zanthoxylum bungeanum Maxim.) leaf (ZL) extract was added to larou to investigate the improvement in the quality of physicochemical properties, texture, water distribution, and microorganism growth during storage for 20 days. Based on the results, the addition of ZL extract significantly retarded the increase in cooking loss, TBARS value, hardness, and microorganism growth. Moreover, the addition of ZL extract decreased the pH value, lightness, and microorganism counts, and increased the moisture content, total soluble protein content, a* value, b* value, and chewiness. The LF-NMR results showed that the addition of ZL extract shortened the T2 relaxation time and boosted the proportion of immobilized water, facilitating the validation of the improvement in water retention of larou during storage. The FT-IR results indicated that the addition of ZL extract influenced the protein secondary structure by inducing the conversion of α-helices to β-sheet structures. Accordingly, ZL extract has the potential to serve as a natural antioxidant, effectively helping to ameliorate the quality properties of cured meat products during storage.

Ionic strength-mediated protein and flavor studies on thermally processed hairtail pieces

This study aimed to investigate the impact of different ionic strengths on the texture, protein, and flavor of thermally processed hairtail pieces. Incorporating salt ions into the heat treatment process had a positive impact on the quality of the cooked hairtail pieces. The pieces treated with 2 M NaCl showed superior texture and sensory scores. The ionic strength had a significant positive correlation with the chewiness and cohesion of cooked hairtail (p < 0.01). Furthermore, the myofibrillar protein content and total sulfhydryl content increased significantly. Circular dichroism spectra analysis revealed a transition in the protein structure from a β-sheet structure to an α-helical structure as the ionic strength decreased. The ionic strength had a significant impact on the interaction between protein and flavor compounds. Specifically, it impacted the expression of certain volatile components (p < 0.05). Our study suggests that selecting the appropriate cooking method is crucial for both healthiness and sensory quality of processed hairtail products, and ionic strength mediation is superior in both aspects.

Transcriptomics integrated with metabolomics to characterize key pigment compounds and genes related to anthocyanin biosynthesis in Zanthoxylum bungeanum peel

Zanthoxylum bungeanum is an important condiment with high economic value and its peel color is one of the main quality indexes. However, the key pigment compounds and related genes are still unclear affecting the quality control of the plants. In this study, the contents of four types of pigments were measured in Z. bungeanum and flavonoids were identified as the most important pigments. Based on the targeted flavonoid metabolomics of Z. bungeanum peels, 14 key pigment compounds were screened out from 152 flavonoids, among which cyanidin-3-O-rutinoside and cyanidin-3-O-glucoside were the most critical compounds for peel color. They were further verified to be present in nine varieties of Z. bungeanum by HPLC fingerprints. The 14 compounds were all associated with flavonoid and anthocyanin biosynthesis pathways and the 39 differentially expressed genes related to these pathways were annotated and screened based on transcriptomics. The genes ZbDFR, ZbANS, and ZbUFGT were identified as three key genes for anthocyanin synthesis in Z. bungeanum peels. Further qRT-PCR results confirmed the reliability of transcriptomics and the accuracy of gene screening. Subsequent protein induced expression demonstrated that ZbANS and ZbUFGT were expressed after 12 h induced by IPTG while ZbDFR was expressed after 15 h. Further transient and stable transformation analysis confirmed that both anthocyanin content and the expression of ZbDFR were significantly increased in overexpression Z. bungeanum leaves and Nicotiana benthamiana. The functional effect of stable transformation of ZbDFR was more significant than that of transient transformation with a 7.67-fold/1.49-fold difference in total anthocyanin content and a 42.37-fold/12.32-fold difference in the expression of ZbDFR. This study provides new insights into the chemical composition and the molecular mechanisms of Z. bungeanum peel color and lays an effective foundation for the color quality control, multi-purpose utilization of Z. bungeanum and the creation of new germplasm.

Formation of Lipid-Derived Flavors in Dry-Cured Mackerel (Scomberomorus niphonius) via Simulation of Autoxidation and Lipoxygenase-Induced Fatty Acid Oxidation

In this study, lipoxygenase (LOX) extracted from dry-cured mackerel was purified, resulting in a 4.1-fold purification factor with a specific activity of 493.60 U/min·g. LOX enzymatic properties were assessed, referring to its optimal storage time (1-2 days), temperature (30 °C), and pH value (7.0). The autoxidation and LOX-induced oxidation of palmitic acid (C16:0), stearic acid (C18:0), oleic acid (C18:2n9c), linoleic acid (C18:2n6c), arachidonic acid (C20:4), EPA (C20:5), and DHA (C22:6n3) were simulated to explore the main metabolic pathways of key flavors in dry-cured mackerel. The results showed that the highest LOX activity was observed when arachidonic acid was used as a substrate. Aldehydes obtained from LOX-treated C18:1n9c and C18:2n6c oxidation, which are important precursors of flavors, were the most abundant. The key flavors in dry-cured mackerel were found in the oxidative products of C16:0, C18:0, C18:1n9c, C18:2n6c, and C20:4. Heptanaldehyde could be produced from autoxidation or LOX-induced oxidation of C18:0 and C18:1n9c, while nonal could be produced from C18:1n9c and C18:2n6c oxidation. Metabolic pathway analysis revealed that C18:1n9c, C18:2n6c, EPA, and DHA made great contributions to the overall flavor of dry-cured mackerel. This study may provide a relevant theoretical basis for the scientific control of the overall taste and flavor of dry-cured mackerel and further standardize its production.

Chemotaxonomic variation in volatile component contents and their correlation between climate factors in Chinese prickly ash peels (Zanthoxylum bungeanum Maxim.)

In this study, we analyzed the characteristics of volatile compounds of Chinese prickly ash peels with different climate conditions and their correlation. The data revealed that the contents of limonene and linalool in peels from southwest and northwest regions were higher, and the aroma was stronger, while the contents of β-myrcene and (E)-ocimene in them from north, east and central China were higher, and the spicy flavor was heavier. Hierarchical cluster analysis demonstrated that the classification had geographical continuity. Through the correlation analysis and path analysis, it was found that the contents of volatile compounds were closely related to the climatic factors. The influence of wind speed and annual average temperature on volatile substances was greater than that of annual average precipitation and annual sunshine duration. This enriched the effect of climatic factors on the accumulation of volatile substances, and promoted the agriculture practices in area having similar climate conditions.

The Effect of Prickly Ash (Zanthoxylum bungeanum Maxim) on the Taste Perception of Stewed Sheep Tail Fat by LC-QTOF-MS/MS and a Chemometrics Analysis

This work aims to explore the contribution of prickly ash (Zanthoxylum bungeanum Maxim) on the taste perception of stewed sheep tail fat. Liquid chromatography-tandem quadrupole time of flight mass spectrometry (LC-QTOF-MS) was applied to analyze the taste-related compounds. A total of 99 compounds in different sheep tail fat samples were identified. The semi-quantitative results showed that there were differences between the samples. The partial least squares discriminant analysis (PLS-DA) model without overfitting was used to investigate the effect of prickly ash. Eleven marker compounds were predicted with a variable importance for projection > 1, fold change > 2 and p < 0.05. An additional experiment showed that guanosine 5'-monophosphate, malic acid, inosine and adenosine 5'-monophosphate could improve the umami and saltiness taste of stewed sheep tail fat.

Effect of locust bean gum-sodium alginate coatings incorporated with daphnetin emulsions on the quality of Scophthalmus maximus at refrigerated condition

In this study, the microbiological, physicochemical, and flavor changes of turbot (Scophthalmus maximus) coated with a composite active coating of locust bean gum (LBG) and sodium alginate (SA) supplemented with daphnetin emulsions (0.16, 0.32, 0.64 mg·mL^-1) were determined during 18 days of refrigerated storage (4 ± 1 °C). Results showed that LBG-SA coatings containing 0.32 mg·mL^-1 daphnetin emulsions could significantly lower the total viable count (TVC), psychrophiles, Pseudomonas spp. and H₂S-producing bacteria counts, and inhibit the productions of off-flavor compounds including the total volatile basic nitrogen (TVB-N), trimethylamine (TMA) and ATP-related compounds. 32 volatile compounds were identified by solid phase microextraction combined with gas chromatography-mass spectrometer method (SPME-GC/MS) during refrigerated storage and the treated turbot samples significantly lowered the relative content of fishy flavor compounds. Further, the LBG-SA coatings containing daphnetin could also delay the myofibril degradation of the turbot samples. These results indicated that the LBG-SA coatings with 0.32 mg·mL^-1 daphnetin were a potential alternative way to improve the quality of turbot during refrigerated storage.

Distinguishing between long-term-stored and fresh chili pepper powder through fingerprinting of volatiles by headspace capillary-gas chromatography-ion mobility spectrometry

Long-term storage of chili pepper powder results in physicochemical and microbiological changes that decrease its commercial value; these changes occur owing to fungal growth and production of off-flavor compounds. Herein, long-term-stored chili pepper powder (LSCPP) and fresh chili pepper powder (FCPP) were analyzed using internal transcribed spacer sequencing and volatile organic compound fingerprinting by headspace capillary-gas chromatography-ion mobility spectrometry. Fungal analysis detected only Xeromyces bisporus with high accuracy in all the analyzed LSCPP samples. However, the proliferation of X. bisporus on nonspecific spots complicated the distinguishing process between the two groups based solely on fungal analysis. Therefore, nine compounds (three ketones, one alcohol, two aldehydes, one ester, one furan, and one sulfur compound) obtained by autoxidation and fungal metabolism were selected as potential markers for distinguishing LSCPP and FCPP. These above-mentioned substances, which were confirmed as off-flavor species owing to "stale" odor, emitted lipid fragrance and were used to successfully distinguish LSCPP from FCPP using principal component analysis and linear discriminant analysis. PRACTICAL APPLICATION: According to the research results, it was possible to discriminate between long-term stored and fresh chili pepper powders using nine VOC markers for quality control in industry. In addition, the fungus generated from long-term storage of chili pepper powder was Xeromyces bisporus, which was confirmed to be safe for intake because it does not form secondary toxic metabolites.