Influence of Fruit Ripening on Color, Organic Acid Contents, Capsaicinoids, Aroma Compounds, and Antioxidant Capacity of Shimatogarashi (Capsicum frutescens)

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.

Genetic Regulation, Environmental Cues, and Extraction Methods for Higher Yield of Secondary Metabolites in Capsicum

Capsicum (chili pepper) is a widely popular and highly consumed fruit crop with beneficial secondary metabolites such as capsaicinoids, carotenoids, flavonoids, and polyphenols, among others. Interestingly, the secondary metabolite profile is a dynamic function of biosynthetic enzymes, regulatory transcription factors, developmental stage, abiotic and biotic environment, and extraction methods. We propose active manipulable genetic, environmental, and extraction controls for the modulation of quality and quantity of desired secondary metabolites in Capsicum species. Specific biosynthetic genes such as Pun (AT3) and AMT in the capsaicinoids pathway and PSY, LCY, and CCS in the carotenoid pathway can be genetically engineered for enhanced production of capsaicinoids and carotenoids, respectively. Generally, secondary metabolites increase with the ripening of the fruit; however, transcriptional regulators such as MYB, bHLH, and ERF control the extent of accumulation in specific tissues. The precise tuning of biotic and abiotic factors such as light, temperature, and chemical elicitors can maximize the accumulation and retention of secondary metabolites in pre- and postharvest settings. Finally, optimized extraction methods such as ultrasonication and supercritical fluid method can lead to a higher yield of secondary metabolites. Together, the integrated understanding of the genetic regulation of biosynthesis, elicitation treatments, and optimization of extraction methods can maximize the industrial production of secondary metabolites in Capsicum.

Odor changes in breast milk during different storage temperatures and times using GC × GC-O-MS

Breastfeeding is generally the preferred way that most mothers will choose. It is common to store expressed breast milk in the refrigerator in many families. However, there is a phenomenon that infants may refuse to consume stored breast milk, presumably due to changes in odor. Thus, the odor changes in breast milk stored at 4 °C for 72 h and at -20 °C for 60 d were studied. Compared with fresh breast milk, 7 and 16 odor compounds were newly detected by SPME and GC × GC-O-MS when breast milk was stored at 4 and -20 °C, respectively. The concentration of (E)-2-decenal, octanal, hexanal, 1-octen-3-ol, 2-pentylfuran, lauric acid, decanoic acid and hexanoic acid significantly increased after storage at 4 °C for 36 h and -20 °C for 30 d. In addition, the proportion of acids increased, whereas that of aldehydes decreased during storage. Chemometric analysis with OPLS-DA suggested that breast milk should be stored at 4 °C for less than 36 h and at -20 °C for less than 30 d for maximum preservation of the original odors.

Physicochemical properties and antioxidant activity of colored peppers (Capsicum annuum L.)

Peppers are spices consumed all around the world. This study evaluated the physicochemical properties and antioxidant activities of red, orange, yellow, green, and purple peppers. Total capsaicinoids showed the highest concentration in the green pepper (2416.50 µg/g). Vitamin C showed similar concentrations in all peppers (28.90-30.95 mg/g), except for the purple pepper (25.59 mg/g). Chlorophyll was abundant in the green and the purple peppers (280.36 and 102.13 mg/100 g). Total carotenoid was abundant in the red and the orange peppers (237.04 and 276.94 mg/100 g). Total anthocyanin was detected only in the purple pepper (67.13 mg/100 g). Total flavonoid showed a high concentration in the green and the purple peppers (24.27 and 22.27 CAE mg/g). The yellow pepper showed the highest antioxidant activity according to total polyphenol, DPPH radical scavenging activity, ABTS radical scavenging activity and reducing power assays. Therefore, peppers showed potential for the development of functional food materials.

Storage Stability of Nutritional Qualities, Enzyme Activities, and Volatile Compounds of "Hangjiao No. 2" Chili Pepper Treated With Different Concentrations of 1-Methyl Cyclopropene

This study aimed to determine the effects of different concentrations of 1-methyl cyclopropene (1-MCP) on the nutritional quality, antioxidant enzyme activities, and volatile compounds of "Hangjiao No.2" chili pepper during 12 days of storage at ambient temperature. The chili fruit were randomly selected and divided into four groups corresponding to the four treatments, thus, 0.5, 1.0, and 1.5 μl L^-1 1-MCP and a control. The analysis of the nutritional value, enzyme activities, and volatile compounds were determined at 3 days interval. The results showed that the malondialdehyde (MDA) content was lower in the fruit treated with 1-MCP compared to the control. The treatment with 1.5 μl L^-1 and the control showed the lowest superoxide dismutase (SOD) activity compared to the other treatments. Peroxidase (POD) and Catalase (CAT) were highest in the fruit treated with 0.5 μl L^-1 compared to the control and treatment with 1.0 μl L^-1. The 1.5 μl L^-1 treatment delayed the decline in vitamin C and protein content compared to the control. Nitrate levels increased 1.34-fold at 0.5 μl L^-1 and 2.01-fold in the control. Chlorophyll content degradation was delayed at 1.0 μl L^-1 compared to the control. A total of 88 volatile compounds, including terpenes, aldehydes, alkanes, esters, alcohols, acids, phenolic derivatives, ketones, and other aromatic compounds, were detected in "Hangjiao No.2" pepper during the 12-day storage period and treatment concentrations. The production of volatile terpenes was higher in the control than in the 1-MCP treatments, while the 0.5 μl L^-1 1-MCP treatment generally suppressed the production of volatile compounds during storage. Overall, the production of volatile compounds after treatment was higher in the "Hangjiao No.2" chili fruit treated with 1.0 μl L^-1 1-MCP than in the other treatments throughout the storage period. The results indicate that 1-MCP treatment was more effective in maintaining fruit quality, enhancing the activities of SOD, POD, and CAT, retarding the accumulation of MDA and restoring volatile aromas, with 1.0 μl L^-1 having the best preservative effect on "Hangjiao No.2" chili fruit during storage, which could be useful for future marketing and processing.

Influence of the Phenological Stage and Harvest Date on the Bioactive Compounds Content of Green Pepper Fruit

Green pepper fruit is often consumed before it is completely ripe. However, the influence of the phenological stage in which the green pepper is consumed as a potential influencing factor in its bioactive compounds content and antioxidant capacity remains unknown. In addition, no literature is available concerning the bioactive compounds changes in 'Lamuyo' green peppers along its developmental and growth cycle. For this, two different approaches have been carried out, one using twelve different phenological stages (S1 to S12), and in the other, seven different harvest dates (from 27 February to 20 April). Moreover, bioactive compounds changes during 21 days of postharvest storage at 8 °C were investigated. In this study, bioactive compounds (ascorbic acid, dehydroascorbic acid, and total phenolic content) and the total hydrophilic and lipophilic (TAA-H and TAA-L) antioxidant activity were analysed. In addition, total soluble solids, total acidity, individual sugars, and organic acids were determined. Vitamin C levels increased along the phenological stages and harvest dates due to significant increases in ascorbic and dehydroascorbic acid levels. Our results show that the total phenol content decreases as vegetables develop and subsequently increases both as ripening begins and by the last harvest date. Furthermore, TAA-H was also greater by the phenological stage S12 and the 20 April harvest date. In conclusion, the phenological stage and harvest date are key factors that significantly influence the bioactive compounds of green peppers, and those that appear by S12 and 20 April could be more beneficial to health.

Influence of intra and inter species variation in chilies (Capsicum spp.) on metabolite composition of three fruit segments

Twenty-one different cultivars from four different species were examined. The highest dry weight was present in seeds (between 35 and 50%) and the average water content was 60%. Placenta and pericarp contained on average 86% water. Total sugars variation between species was 60%. The most concentrated in the various cultivar pericarps were ascorbic acid ranging from 368.1 to 2105.6 mg/100 g DW and citric acid ranging from 1464.3 to 9479.9 mg/100 g DW. Total phenolic content ranged from 2599.1 mg/100 DW in 'Chilli AS- Rot' to 7766.7 mg/100 g DW in 'Carolina Reaper'. The placenta had 23.5 times higher phenolic content than seeds. C. chinense and C. chinense × C. frutescens had 3.5 to 5 times higher capsaicinoid content compared to C. annuum and C. baccatum, with 'Carolina Reaper' having the highest content at 7334.3 mg/100 g DW and 'Chilli AS- Rot' the lowest (318.7 mg/100 g DW).

Experimental races of Capsicum annuum cv. jalapeño: Chemical characterization and classification by 1H NMR/machine learning

This work reports on the metabolic fingerprinting of ten new races of Capsicum annuum cv. jalapeño using ¹H NMR based metabolomics coupled to machine learning projections. Ten races were classified and evaluated according to their differential metabolites, variables of commercial interest and by multivariate data analysis/machine learning algorithm. According to our results, experimental races of jalapeño peppers exhibited differences in carbohydrate, amino acid, nucleotide and organic acid contents. Forty-eight metabolites were identified by 1D and 2D NMR and the differential metabolites were quantified by qNMR. Principal component analysis (PCA) and orthogonal partial least squares discriminant analysis (OPLS-DA) separated the studied races into two groups. The group A included the races Colosus, Emperador, Fundador and Rayo whereas the group B included the races Don Benito, SMJ 1416, SMJ 1417, SMJ 1423, SMJ 145 and STAM J0904. OPLS-DA revealed that levels of citric acid in group A were higher than in group B, while the levels of asparagine, fumaric acid, GABA, glucose, malic acid, pyruvic, quinic acid, sucrose and tryptophan were higher in the group B. Remarkably, ascorbic acid was exclusively found in the race Colosus. Random forest model revealed the diversity of the experimental races and the similarity rate with the well-established races. The most relevant variables used to generate a model were length, weight, yield, width, xylose content and organic acids content.

A high-throughput platform for interpretation of metabolite profile data from pepper (Capsicum) fruits of 13 phenotypes associated with different fruit maturity states

Nowadays, novel tools have been developed for efficient analysis and visualization of large-scale metabolite profile data associated with metabolic pathways. A high-throughput platform using PathVisio 3 combined with multivariate analysis is proposed for the first time. Additionally, this is the first analysis of the relationships among terpenoids monoterpene, sesquiterpene, triterpene, and tetraterpene during pepper fruit ripening, and their changes. This platform was successfully applied to interpret large-scale data related to 131 metabolites from mature and immature fruits of 13 pepper phenotypes. The carotenoid-derived volatiles, such as dihydroactinidiolide and β-ionone were closely correlated with carotenoids, indicating that the synthesis and degradation of carotenoids occurred in pepper fruit mature stage. Using PathVisio 3, the metabolic changes in pathway could be presented quickly, revealing the accumulation of stress-related metabolites, such as proline, capsaicin, and phenylalanine, in the mature stage. This approach could provide useful information about comprehensive biochemical regulation of fruit ripening.

Analysis of Volatile Compounds from Chili Peppers and Characterization of Habanero (Capsicum chinense) Volatiles

The Habanero pepper is characterized by its strong pungency and fruity aroma. The aim of the present study was to extract the volatile compounds of Habanero peppers, using solvent extraction and solvent-assisted flavor evaporation (SAFE) methods, and to analyze them using gas chromatography-mass spectrometry (GC-MS). The analysis detected 66 volatile compounds, including 6-methyl-(E)-4-heptenyl 3-methylbutanoate 1, which was reported previously, and 6-methyl-(E)-4-heptenyl 2-methylpropanoate 2, the corresponding butanoate 3, 2-methylbutanoate 4, and 6-methyl-(E)-4-heptenol 5, which were found in both Habanero and other peppers. 6-Methyl-(E)-4-heptenyl 3-methylbutanoate 1 and related compounds were synthesized. Furthermore, principal component analysis (PCA) and hierarchical cluster analysis (HCA) of the volatile profiles generally grouped the pepper samples by species and indicated that Habanero peppers are characterized by the presence of 6-methyl-(E)-4-heptenyl esters.

Metabolomic analysis of the effects of a commercial complex biostimulant on pepper crops

Research on plant biostimulants is of interest in their potential benefits for agriculture production and environmental sustainability. These naturally occurring products induce beneficial consequences in plant metabolism and productivity. In most cases their modes of action, and consequences for the whole plant as well as parts, such as the fruit, are well characterized, but the precise mechanisms of action require further attention. This study examined the effects of the commercial biostimulant, Actium®, on Capsicum annuum L. cv Palermo leaves and fruits. The influence of time (characterized by ripening), after 14 and 28 days of treatment, treatment regimen, and their combined impact on the metabolome were studied using HPLC-ESI-QTOF-MS analysis of polar and apolar compounds. The results showed that flavonoids and capsianosides decreased with ripening in leaves, but organic acids, monosaccharides, and carotenoids increased in fruits. The treatment of Capsicum fruits with Actium® increased phenylalanine and total monosaccharides (glucose and fructose) compared to controls, suggesting a further stage in ripening. An increase in carotenoids concomitant with an increase of some digalactosyl diacylglycerols, which are part of the chromoplasts lipid machinery of enzymes involved in the synthesis of carotenoids, was also observed. Our findings suggest that this biostimulant may increase some metabolites related to pepper fruit maturity and coloration in pepper crops.

Capsaicinoids, Polyphenols and Antioxidant Activities of Capsicum annuum: Comparative Study of the Effect of Ripening Stage and Cooking Methods

Peppers (Capsicum annuum L.) are an important crop usually consumed as food or spices. Peppers contain a wide range of phytochemicals, such as capsaicinoids, phenolics, ascorbic acid, and carotenoids. Capsaicinoids impart the characteristic pungent taste. The study analyzed capsaicinoids and other bioactive compounds in different pepper cultivars at both the mature green and red stages. The effect of roasting on their nutritional content was also investigated. In the cultivars tested, the levels of capsaicin ranged from 0 to 3636 µg/g in the mature green stage and from 0 to 4820 µg/g in the red/yellow stage. The concentration of dihydrocapsaicin ranged from 0 to 2148 µg/g in the mature green stage and from 0 to 2162 µg/g in the red/yellow stage. The levels of capsaicinoid compounds in mature green and red /yellow stages were either reduced or increased after roasting depending on the cultivar. The ranges of total phenolic and total flavonoids compounds were 2096 to 7689, and 204 to 962 µg/g, respectively, in the green and red/yellow mature stage pods. Ascorbic acid levels in the peppers ranged from 223 to 1025 mg/ 100 g Dry Weight (DW). Both raw and roasted peppers possessed strong antioxidant activity as determined by 2,2-diphenyl-1-picrylhydrazyl) reagent (DPPH, 61–87%) and 2,2′-azino-bis (3-ethylbenzthiazoline-6-sulphonic acid) (ABTS, 73–159 µg/g) assays. Ascorbic acid and antioxidant activity decreased after roasting in the mature green and red stages, whereas total phenolics and flavonoids increased except in the mature green stage of Sweet Delilah and yellow stage of Canrio.

Comparative Quantitative Study on Phytochemical Contents and Antioxidant Activities of Capsicum annuum L. and Capsicum frutescens L

The variabilities in the phytochemical contents and antioxidant activities of four varieties of two closely related cultivated Capsicum species, C. annuum and C. frutescens, were examined as an additional tool for establishing their phylogenetic relatedness and for breeding purposes. The methodology involved the use of ethanolic and aqueous extractions for the determination of the phytochemical and antioxidant properties. The phytochemical contents including total flavonoid, total phenol, and proanthocyanidins were evaluated spectrophotometrically while the antioxidant activities were determined by 2,2-diphenyl-1-picrylhydrazyl (DPPH), 2,2'-azino-bis(3-ethylbenzothiazoline)-6-sulfonic acid (ABTS), nitric oxide (NO), and phosphomolybdenum assays. To point out the relationship among the varieties, a dendrogram based on the antioxidative phytochemical contents was constructed using the unweighted pair group method with arithmetic mean (UPMGA) cluster analysis. In all, aqueous extracts gave higher yield while ethanolic extracts showed higher phytochemical content across the varieties. Significant variations were observed among the varieties in relation to their phytochemical constituents and antioxidant activities. Dendrogram obtained from multivariate analysis distinguished the two Capsicum species. The first cluster contained only C. frutescens var. baccatum while the second cluster contained the three varieties of C. annuum species in subclusters, signifying the close genetic affinity among the three varieties. It also revealed that the four varieties are of a common progenitor. Information from this study gives additional evidence of chemotaxonomic significance and baseline data for effective selection of suitable parental genotypes in breeding for nutritional and pharmacological purposes.