Effect of different genotypes on the fruit volatile profiles, flavonoid composition and antioxidant activities of chilli peppers

Volatile flavor behavior characterization of Hericium erinaceus during postharvest storage using E-nose, HS-GC-IMS, and HS-SPME-GC-MS after treated with electron-beam generated X-ray irradiation

Flavor alteration is a crucial factor affecting the quality of mushrooms during preservation. The dynamic variations of volatile profiles of fresh Hericium erinaceus with electron-beam generated X-ray irradiation were investigated by combining E-nose, headspace-gas chromatography-ion mobility spectrometry (HS-GC-IMS), and headspace solid-phase microextraction gas chromatography-mass spectrometry (HS-SPME-GC-MS). E-nose analysis achieved rapid discrimination in all treatments over storage time. 65 and 73 volatile organic compounds (VOCs) were identified by HS-GC-IMS and HS-SPME-GC-MS, respectively. Thereinto, 1-octen-3-ol, 1-octen-3-one, and 2-octanone were screened out as the characteristic VOCs, which contents declined during storage. While the contents of (E)-2-octenal, (E)-2-nonenal, and 1-octanol increased. The flavor profile changes from distinct mushroom and floral odor to an intense alcohol and fatty odor. Notably, one-kGy irradiation remained more volatiles and denser mushroom odor after storage. Multivariate analysis further confirmed that 1.0 kGy irradiation contributed to the overall aroma retention during postharvest storage of H. erinaceus.

Dissection of Metabolome and Transcriptome-Insights into Capsaicin and Flavonoid Accumulation in Two Typical Yunnan Xiaomila Fruits

Pepper is an economically important vegetable worldwide, containing various specialized metabolites crucial for its development and flavor. Capsaicinoids, especially, are genus-specialized metabolites that confer a spicy flavor to Capsicum fruits. In this work, two pepper cultivars, YB (Capsicum frutescens L.) and JC (Capsicum baccatum L.) pepper, showed distinct differences in the accumulation of capsaicin and flavonoid. However, the molecular mechanism underlying them was still unclear. Metabolome analysis showed that the JC pepper induced a more abundant accumulation of metabolites associated with alkaloids, flavonoids, and capsaicinoids in the red ripening stages, leading to a spicier flavor in the JC pepper. Transcriptome analysis confirmed that the increased expression of transcripts associated with phenylpropanoid and flavonoid metabolic pathways occurred in the JC pepper. Integrative analysis of metabolome and transcriptome suggested that four structural genes, 4CL7, 4CL6, CHS, and COMT, were responsible for the higher accumulation of metabolites relevant to capsaicin and flavonoids. Through weighted gene co-expression network analyses, modules related to flavonoid biosynthesis and potential regulators for candidate genes were identified. The promoter analysis of four candidate genes showed they contained several cis-elements that were bonded to MYB, bZIP, and WRKY transcription factors. Further RT-qPCR examination verified three transcription factors, MYB, bZIP53, and WRKY25, that exhibited increased expression in the red ripening stage of the JC pepper compared to YB, which potentially regulated their expression. Altogether, our findings provide comprehensive understanding and valuable information for pepper breeding programs in the future.

Comparative analysis of lipid and flavonoid biosynthesis between Pongamia and soybean seeds: genomic, transcriptional, and metabolic perspectives

BACKGROUND

Soybean (Glycine max) is a vital oil-producing crop. Augmenting oleic acid (OA) levels in soybean oil enhances its oxidative stability and health benefits, representing a key objective in soybean breeding. Pongamia (Pongamia pinnata), known for its abundant oil, OA, and flavonoid in the seeds, holds promise as a biofuel and medicinal plant. A comparative analysis of the lipid and flavonoid biosynthesis pathways in Pongamia and soybean seeds would facilitate the assessment of the potential value of Pongamia seeds and advance the genetic improvements of seed traits in both species.

RESULTS

The study employed multi-omics analysis to systematically compare differences in metabolite accumulation and associated biosynthetic genes between Pongamia seeds and soybean seeds at the transcriptional, metabolic, and genomic levels. The results revealed that OA is the predominant free fatty acid in Pongamia seeds, being 8.3 times more abundant than in soybean seeds. Lipidomics unveiled a notably higher accumulation of triacylglycerols (TAGs) in Pongamia seeds compared to soybean seeds, with 23 TAG species containing OA. Subsequently, we identified orthologous groups (OGs) involved in lipid biosynthesis across 25 gene families in the genomes of Pongamia and soybean, and compared the expression levels of these OGs in the seeds of the two species. Among the OGs with expression levels in Pongamia seeds more than twice as high as in soybean seeds, we identified one fatty acyl-ACP thioesterase A (FATA) and two stearoyl-ACP desaturases (SADs), responsible for OA biosynthesis, along with two phospholipid:diacylglycerol acyltransferases (PDATs) and three acyl-CoA:diacylglycerol acyltransferases (DGATs), responsible for TAG biosynthesis. Furthermore, we observed a significantly higher content of the flavonoid formononetin in Pongamia seeds compared to soybean seeds, by over 2000-fold. This difference may be attributed to the tandem duplication expansions of 2,7,4'-trihydroxyisoflavanone 4'-O-methyltransferases (HI4'OMTs) in the Pongamia genome, which are responsible for the final step of formononetin biosynthesis, combined with their high expression levels in Pongamia seeds.

CONCLUSIONS

This study extends beyond observations made in single-species research by offering novel insights into the molecular basis of differences in lipid and flavonoid biosynthetic pathways between Pongamia and soybean, from a cross-species comparative perspective.

Piquin chili, a wild spice: natural variation in nutraceutical contents

The piquin chili is a wild spice widely consumed from the South United States to Central America and stands out as a source of flavonoids, essential metabolites with antioxidant properties. The concentrations of flavonoids, carotenoids, and capsaicinoids vary according to regions, maturity stages, and ripening processes. These compounds, which are known for their health benefits and industrial applications, highlight the importance of identifying ideal environmental conditions for collecting fruits with the highest contents. Comprehensive studies of the piquin chili are essential for understanding its properties for the benefit of consumers. This approach fortifies trade, contributes to resource conservation, and advances cultivated chili production.

Discrimination and characterization of volatile organic compounds and nutritional values of three varieties of chopped pepper seeds

Fermented-chopped pepper is a widely consumed condiment in China due to its attractive flavor. Chopped pepper seed (CPS) is the byproduct generated during the production of chopped pepper and is generally discarded as waste. In this study, the volatile organic compounds (VOCs) and nutritional value of three varieties of CPS were investigated. Results indicated that the nutritional compositions of the three CPS varieties exhibited significant differences. All CPS samples contained 17 amino acids and were rich in fatty acids, with unsaturated fatty acids being predominant and accounting for 79 % of the total fatty acids. A total of 53 VOCs were identified by gas chromatography-ion mobility spectrometry, which could be classified into 9 groups, with aldehydes, esters, and alcohols comprising the three largest groups. The three varieties of CPS had remarkably varied aromas whereas there are five key VOCs (i.e., 2-pentylfuran, methional, ethyl 3-methylbutanoate, dimethyl disulfide, and nonanal) in all CPS samples. Network correlation analysis revealed that VOCs are closely correlated with amino and fatty acids. Thus, this study provides a useful basis for understanding the nutritional values and flavor characteristics of different CPS varieties, which could be used as an ingredient and might have great potential in the food industry.

Comparative metabolomics reveals complex metabolic shifts associated with nitrogen-induced color development in mature pepper fruit

Pigments derived from red pepper fruits are widely used in food and cosmetics as natural colorants. Nitrogen (N) is a key nutrient affecting plant growth and metabolism; however, its regulation of color-related metabolites in pepper fruit has not been fully elucidated. This study analyzed the effects of N supply (0, 250, and 400 kg N ha-1) on the growth, fruit skin color, and targeted and non-target secondary metabolites of field-grown pepper fruits at the mature red stage. Overall, 16 carotenoids were detected, of which capsanthin, zeaxanthin, and capsorubin were the dominant ones. N application at 250 kg ha-1 dramatically increased contents of red pigment capsanthin, yellow-orange zeaxanthin and β-carotene, with optimum fruit yield. A total of 290 secondary metabolites were detected and identified. The relative content of most flavonoids and phenolic acids was decreased with increasing N supply. Correlation analysis showed that color parameters were highly correlated with N application rates, carotenoids, flavonoids, phenolic acids, lignans, and coumarins. Collectively, N promoted carotenoid biosynthesis but downregulated phenylpropanoid and flavonoid biosynthesis, which together determined the spectrum of red color expression in pepper fruit. Our results provide a better understanding of the impact of N nutrition on pepper fruit color formation and related physiology, and identification of target metabolites for enhancement of nutritional quality and consumer appeal.

Natural antioxidants as strategy to minimize the presence of lipid oxidation products in canned fish: Research progress, current trends and future perspectives

Canned fish is one of the most popular forms of fish consumption due to its high nutritional value, availability, and practicality. However, canning may induce lipid oxidation. Thus, this study provides in-depth information on the impact of high temperatures applied during canning on fish lipids. The thermo-oxidation is evidenced, for example, by the high levels of both primary and secondary oxidation products determined in fish after canning, as well as the presence of harmful compounds such as cholesterol oxides. Given the role of lipid oxidation in canned fish, this study also presents a comprehensive review on using natural antioxidants to control it. The antioxidant properties of common liquid mediums (vegetable oils and sauces) are highlighted. Moreover, adding algae extracts, spices, and condiments to the liquid medium to enhance its antioxidant potential has been considered, while the exploitation of by-products and wastes from the food industry also emerges as a suitable strategy. Besides the promising results, these practices may promote positive impacts on other quality parameters (e.g. water and oil holding capacities, texture, microbiological growth). However, further studies are needed, including research on aspects related to safety, effective concentrations and application methods, without ignoring consumers' sensory acceptance.

Transcriptome and metabolite analyses indicated the underlying molecular responses of Asian ginseng (Panax ginseng) toward Colletotrichum panacicola infection

Panax ginseng Meyer is one of the most valuable plants and is widely used in China, while ginseng anthracnose is one of the most destructive diseases. Colletotrichum panacicola could infect ginseng leaves and stems and causes serious anthracnose disease, but its mechanism is still unknown. Here, transcriptome and metabolism analyses of the host leaves were conducted to investigate the ginseng defense response affected by C. panacicola. Upon C. panacicola infection, ginseng transcripts altered from 14 to 24 h, and the expression of many defense-related genes switched from induction to repression. Consequently, ginseng metabolites in the flavonoid pathway were changed. Particularly, C. panacicola repressed plant biosynthesis of the epicatechin and naringin while inducing plant biosynthesis of glycitin, vitexin/isovitexin, and luteolin-7-O-glucoside. This work indicates C. panacicola successful infection of P. ginseng by intervening in the transcripts of defense-related genes and manipulating the biosynthesis of secondary metabolites, which might have antifungal activities.

Antioxidant potential and factors influencing the content of antioxidant compounds of pepper: A review with current knowledge

The use of natural food items as antioxidants has gained increasing popularity and attention in recent times supported by scientific studies validating the antioxidant properties of natural food items. Peppers (Capsicum spp.) are also important sources of antioxidants and several studies published during the last few decades identified and quantified various groups of phytochemicals with antioxidant capacities as well as indicated the influence of several pre- and postharvest factors on the antioxidant capacity of pepper. Therefore, this review summarizes the research findings on the antioxidant activity of pepper published to date and discusses their potential health benefits as well as the factors influencing the antioxidant activity in pepper. The major antioxidant compounds in pepper include capsaicinoids, capsinoids, vitamins, carotenoids, phenols, and flavonoids, and these antioxidants potentially modulate oxidative stress related to aging and diseases by targeting reactive oxygen and nitrogen species, lipid peroxidation products, as well as genes for transcription factors that regulate antioxidant response elements genes. The review also provides a systematic understanding of the factors that maintain or improve the antioxidant capacity of peppers and the application of these strategies offers options to pepper growers and spices industries for maximizing the antioxidant activity of peppers and their health benefits to consumers. In addition, the efficacy of pepper antioxidants, safety aspects, and formulations of novel products with pepper antioxidants have also been covered with future perspectives on potential innovative uses of pepper antioxidants in the future.

Comparison of microbial communities and volatile profiles of wines made from mulberry and grape

In this study, three kinds of wines separately made from mulberry (MW), grape (GW), or mulberry/grape (MGW) were developed and their enological parameters, sensory scores, volatile components, and microbiota were investigated and compared. Contrary to the order of residual sugar and acidity of the three kinds of wines, the order of alcohol content from high to low is GW, MW, and MGW. A total of 60 volatile components (VCs), including esters (17), alcohols (12), acids (6), aldehydes (7), ketones (3), alkenes (3), amines (3), alkanes (4), pyrazines (2), benzene (1), sulfide (1), and thiazole (1), were identified by gas chromatography-ion mobility spectrometer (GC-IMS). The fingerprint of VCs and principal component analysis revealed that the volatile profiles of MGW and GW were more similar in comparison to that of MW and were significantly correlated with the mass ratio of mulberry to grape. Lactobacillus, Weissella, Pantoea, Leuconostoc, Lactococcus, Paenibacillus, Pediococcus, and Saccharomyces were identified as the main microflora at the genus level shared by the MW, MGW, and GW, suggesting that the heterolactic bacteria may contribute more to the high content of volatile acids in MW and MGW. The heatmap of core microbiota and main VCs of MW, MGW, and GW suggested the complicated and significant correlation between them. The above data implied that the volatile profiles were more closely related to the raw materials of winemaking and markedly affected by the fermentation microorganisms. This study provides references for evaluation and characterization of MGW and MW and improvement of MGW and MW winemaking process. KEY POINTS: • Fruit wine enological parameters, volatile profile, and microbiota were compared. • Sixty volatile compounds were identified by GC-IMS in three types of fruit wines. • Winemaking materials and microbiota affect volatile profiles of the fruit wines.

Determination of multiple mycotoxins in chili powder using cold-induced liquid-liquid extraction and Fe3O4@MWCNTs-NH2 coupled with UPLC-Q-TOF/MS

Food matrix interference is still a big challenge in analyzing multiclass mycotoxins. Herein, a novel cold-induced liquid-liquid extraction-magnetic solid phase extraction (CI-LLE-MSPE) coupled with ultra-high performance liquid chromatography-quadrupole time of flight mass spectrometry (UPLC-Q-TOF/MS) method was explored for the simultaneous determination of multiple mycotoxins in chili powders. Fe₃O₄@MWCNTs-NH₂ nanomaterials were prepared and characterized, and the factors affecting the MSPE process were investigated. Based on this, the CI-LLE-MSPE-UPLC-Q-TOF/MS method was established for determining ten mycotoxins in chili powders. The proffered technique eliminated the matrix interference effectively and demonstrated strong linearity (0.5-500 µg/kg, R² ≥ 0.999), high sensitivity (limit of quantification was 0.5-1.5 µg/kg), and the recovery was 70.6%-111.7%. The extraction process is simpler than conventional methods, as the adsorbent can be separated using magnets, and reusable adsorbents are beneficial in reducing costs. In addition, the method can provide a valuable reference for pretreatment procedures for other complex matrices.

Cold shock precooling improves the firmness of chili pepper during postharvest storage and the molecular mechanisms related to pectin

This research was conducted to explore the influence of cold shock on the firmness, a quality marker in chili pepper during 0-21 d storage and determine mechanism by cold shock impacted pectin. Chili peppers were exposed to cold shock precooling (0 ± 2 °C water/ice mixture) for 0-, 30-, 90- and 150-min, respectively. Results showed that cold shock alleviated loss of firmness throughout storage. Firmness was positively associated with sodium carbonate-soluble pectin content (r = 0.44), methylation degree of CDTA-soluble pectin (r = 0.82) and water-soluble pectin (WSP, r = 0.87), but negatively associated with WSP content (r = -0.76), and the activities of β-galactosidase (r = -0.72) and pectinlyase (r = -0.74). Cold shock for 90 min was determined to be optimal. This study confirms the applicability of cold shock precooling to maintain firmness and thereby to extend the shelf life of chili pepper.

Copper inhibits postacidification of yogurt and affects its flavor: A study based on the Cop operon

Yogurt and its related products are popular worldwide. During transportation and storage, Lactobacillus delbrueckii ssp. bulgaricus in yogurt continues to metabolize to form lactic acid, the postacidification phenomenon of yogurt. Postacidification of yogurt is a widespread phenomenon in the dairy industry. Many scholars have done research on controlling the postacidification process, but few report on the molecular mechanisms involved. In this study, we used a molecular-assisted approach to screen food additives that can inhibit postacidification and analyzed its effects on yogurt quality as well as its regulatory mechanism from multi-omics perspectives in combination. The copper ion was found to upregulate the expression of the LDB_RS05285 gene, and the copper transporter-related genes were regulated by copper. Based on the metabolic-level analysis, copper was found to promote lactose hydrolysis, accumulate a large amount of glucose and galactose, inhibit the conversion of glucose to lactic acid, and reduce the production of lactic acid. The significantly greater abundance of l-isoleucine and l-phenylalanine increased the abundance of 3-methylbutyraldehyde (∼1.2 times) and benzaldehyde (∼7.9 times) to different degrees, which contributed to the formation of the overall flavor of yogurt. Copper not only stabilizes the acidity of yogurt, but also it improves the flavor of yogurt. Through this established method involving quantitative and correlation analyses at the transcriptional and metabolic levels, this study provides guidance for the research and development of food additives that inhibit postacidification of yogurt and provide a reference for studying the changes of metabolites during storage of yogurt.

Water extract of Ferula lehmanni Boiss. prevents high-fat diet-induced overweight and liver injury by modulating the intestinal microbiota in mice

Obesity, often accompanied by hepatic steatosis, has been associated with an increased risk of health complications such as fatty liver disease and certain cancers. Ferula lehmannii Boiss., a food and medicine homologue, has been used for centuries as a seasoning showing anti-bacterial and anti-oxidant effects on digestive discomfort. In the present study, we sought to investigate whether a short-term oral administration of water extract of Ferula lehmanni Boiss. (WEFL) could prevent high-fat diet (HFD)-induced abnormal weight gain and hepatic steatosis in mice and its underlying mechanisms. WEFL reduced HFD-increased body weight, liver injury markers and inflammatory cytokines (i.e. IL-6 and IL-1β), and inhibited the elevation of AMPKα, SREBP-1c and FAS in HFD. Moreover, WEFL reconstructed the gut microbiota composition by increasing the relative abundances of beneficial bacteria, e.g. Akkermansia spp., while decreasing Desulfovibrio spp. and so on, thereby reversing the detrimental effects of HFD in mice. Removal of the gut microbiota with antibiotics partially eliminated the hepatoprotective effects of WEFL. Notably, WEFL substantially promoted the levels of short-chain fatty acids, especially butyric acid. To clarify the functional components at play in WEFL, we used UPLC-MS/MS to comprehensively detect its substance composition and found it to be a collection of polyphenol-rich compounds. Together, our findings demonstrate that WEFL prevented HFD-induced obesity and liver injury through the hepatic-microbiota axis, and such health-promoting value might be explained by the enriched abundant polyphenols.