Search Results (17)

This research investigated the effects of salt concentration on the fermentation of watermelon soybean paste. Three experimental groups were constructed with gradient salt concentrations, and multi-dimensional analyses were performed on physicochemical properties, volatile aroma profiles, and microbial community succession throughout the fermentation process. Group X (lowest salt) exhibited the highest total acid (34.49 g/kg) and lowest pH (p < 0.05) after 60 d. Using headspace gas chromatography time-of-flight mass spectrometry (HS-GC-TOF-MS), a total of 97 volatile compounds were identified, of which 18 were defined as key flavor compounds (relative odor activity value (ROAV) > 0.1 and variable importance in projection (VIP) > 1). High-throughput sequencing demonstrated that Proteobacteria and Firmicutes represented the core bacterial communities while Ascomycota emerged as the dominant fungal phylum. The Shannon diversity index for bacteria ranged from 4.28 to 5.47 across groups. Aspergillus relative abundance in Group X decreased from 75.30% (30 d) to 43.17% (60 d). Group X was distinctly separated from Y and Z in PLS-DA and PCoA analyses. Aspergillus exhibited significant positive correlations with eugenol and 2,2,4-trimethyl-1,3-pentanediol diisobutyrate (p < 0.05). These findings provide an integrated understanding of the associations between volatile compound evolution and microbial succession during natural fermentation, providing a basis for further investigation and process optimization. Full article

The aim of this study was to investigate the dynamic changes in physicochemical properties, microbial community, metabolite profiles, and volatile compounds in watermelon soybean paste (WSP) during natural fermentation. Results showed that total acids, amino nitrogen, reducing sugar content, and umami-taste amino acids were significantly increased in WSP samples during the fermentation process. Various bacterial communities, including Enterobacter, Bacillus, Staphylococcus, Enterococcus, Weissella, and Lactobacillus, were detected as dominant genera. A total of 804 metabolites, mainly including lipids (18.78%) and amino acids and their derivatives (13.56%), were detected across the different fermentation stages. The correlation analysis between volatile compounds and bacterial community at the genus level revealed that 2-methylisoborneol, 1-octen-3-ol, benzene acetaldehyde, tetramethylpyrazine, and phenylethyl alcohol strongly correlated with Enterococcus, Bacillus, Weissella, and Pseudomonas. This study revealed the dynamics of the bacterial community and volatile compounds in the fermentation process and demonstrated their inter-relationship during WSP fermentation. Full article

Watermelon juice is a nutritious yet highly perishable beverage. Conventional thermal pasteurization ensures safety but degrades heat-sensitive nutrients, color, and flavor. Induced electric field (IEF) is an emerging technology that inactivates microorganisms while better preserving quality. However, its effects on the comprehensive quality retention of watermelon juice during storage remain underexplored. This study investigated the efficacy of IEF treatment on the microbial inactivation and quality preservation of watermelon juice during 25 days of storage at 4 °C. Freshly extracted watermelon juice was subjected to low-temperature IEF at 65 °C (IEF1) for 101 s and 60 °C (IEF2) for 88 s, with conventional pasteurization (65 °C, 30 min) as a control. The results showed that no colonies were detected in the IEF2 group throughout the 25-day storage period. Both IEF treatment and pasteurization effectively inhibited juice acidification. Soluble solids content and electrical conductivity remained stable under refrigeration, and the IEF group showed slower and more controllable acidity on day 25. Notably, the IEF1 group retained the highest lycopene content at the end of storage, while the IEF2 group maintained the highest total phenolic content (TPC). Furthermore, IEF treatment effectively mitigated color deterioration and preserved carbohydrate stability during refrigeration. Flavor analysis revealed that the taste profile of the IEF2 group at the initial storage stage closely resembled that of fresh watermelon juice. Over the 25-day period, the relative content of key volatile compounds characteristic of fresh watermelon decreased by only 3.64% in the IEF2 group. Full article

Electronic cigarettes (ECs) are promoted as a safer alternative to traditional cigarettes, yet their impact on immune cells remains incompletely understood. This study investigates the activation of human primary adherent and non-adherent monocytes exposed ex vivo to aerosols from four flavored ECs (classic tobacco, menthol, watermelon, and strawberry) compared to cigarette smoke (CS) and nicotine alone. EC aerosols (ECEs) induced modest cytotoxicity, oxidative stress, and superoxide dismutase activity compared to CS, with high cell response heterogeneity indicating subpopulation-specific effects. Adherent monocytes showed elevated integrin expression (CD11a, CD11b), ICAM-1 (CD54), TNFα, and oxidative stress versus non-adherent cells, amplified by ECE. Dual fluorescence flow cytometry (green DCF for ROS and red for anti-TNFα Ab) revealed shifts toward pro-inflammatory/oxidative quadrants, particularly upper-right high-intensity relatively small subsets with macrophage M1-like CD68 expression in adherent cells. ECEs reduced phagocytosis in adherent monocytes, mimicking CS effects, probably driven by non-nicotine components. Strawberry flavor (ECE 4) elicited the strongest TNFα induction. These findings demonstrate EC-induced subclinical inflammation via selective monocyte activation, potentially contributing to chronic cardiopulmonary risks despite significantly lower overall toxicity than CS. Full article

Second-grade watermelons are a lycopene-rich by-product currently discarded despite their potential for valorization. This study aimed to develop a consumer-accepted alcoholic liqueur by alcoholic maceration of watermelon pulp, optimizing the formulation for lycopene retention, antioxidant activity, and sensory quality. Three pulp ratios (15, 20, and 25% v/v) were macerated in 39% v/v cane alcohol for 5 days at 20 °C. The 20% pulp formulation (T2) achieved the best balance of lycopene (8.6 mg L⁻¹), DPPH antioxidant activity (580 µmol TE L⁻¹), redness (CIE a* = 14.1), and overall acceptability (7.6/9). Under nitrogen-flushed amber glass, T2 retained ≥82% lycopene and ≤10% antioxidant loss after 90 days at 20 °C, following first-order degradation kinetics (Ea = 43 kJ mol⁻¹). A minimum shelf-life of three months is projected under these experimental conditions. Life-cycle screening indicates 0.84 kg CO₂-eq L⁻¹, with a 1.9-year payback and 1.7 t CO₂-eq savings per ton of rescued fruit compared to landfill. These findings demonstrate the feasibility of producing a shelf-stable, naturally colored craft spirit with watermelon flavor, aligning with consumer preferences and circular economy principles in the alcoholic beverage sector. Full article

Watermelon soy sauce (WSS) is a liquid condiment usually prepared using watermelon juice, soybeans, and wheat flour through the process of making koji and natural fermentation. It is widely used in Chinese culinary art, despite the lack of knowledge about its aromatic compound content. Here, we characterized the physicochemical properties, free amino acid composition, and volatile compounds of WSS using SPME-GC/MS and E-nose. We noticed that WSS had the highest total acid content but the lowest amino nitrogen and reducing sugar contents compared with commercial soy sauce. Moreover, the highest amounts of Glu and Pro were observed in WSS. A total of 173 volatile compounds were identified in WSS, including alcohols, hydrocarbons, esters, ketones and aldehydes. The E-nose analysis showed a good capacity of differentiating braised samples mainly through W5S, W1S, W1W, W2W, and W3S sensors. The analysis of relationships between flavor components and free amino acids in soy sauce samples showed that Ser, Gly, Val, Ile, Leu, Ph,e and Lys had a strong positive correlation with alcohol and acidic compounds. Moreover, Pro was found to be correlated with aldehyde, ketone, heterocyclic compounds, sulfur compounds, and benzene, while Glu was correlated with hydrocarbons, aldehyde, and benzene. This study could provide important information regarding WSS quality control, characterization, and aroma improvement. Full article

Biostimulants, particularly single amino acids, can increase plant growth and crop quality, gaining significant attention. This study investigates the effects of 10 amino acids via root/foliar application on the growth, quality, taste, and volatile flavor of mini-watermelons and compares the differences between the application methods. Here, we employed electronic noses, electronic tongues, and gas chromatography–ion mobility spectrometry to investigate these effects. Root application excels in fruit growth and pectin accumulation, while foliar application boosts soluble protein and specific nutrients. Specifically, root application (except for Val) significantly increases fruit weight, with Gly being most effective for longitudinal diameter, while most amino acids (except Val/Lys) promote transverse diameter. Pectin content shows bidirectional regulation: root application of Glu/Gly/Lys/Pro/Trp/Val enhances pectin, whereas foliar application inhibits it. For taste indices, most treatments improve soluble solids (except Glu root/Arg-Leu foliar), and Ala/Asp/Glu/Gly reduce titratable acids, optimizing the sugar–acid ratio. Foliar application is more efficient for soluble protein accumulation (Ala/Glu/Gly/Pro/Leu). For nutritional quality, except for Lys, all treatments increase vitamin C and widely promote total phenolics and lycopene, with only minor exceptions, and only Arg foliar application enhances ORAC. Additionally, the results revealed that root-applied lysine and valine greatly raised the levels of hexanal and 2-nonenal, whereas foliar-applied valine significantly increased n-nonanal and (Z)-6-nonenal. Overall, we found that amino acids can considerably improve mini-watermelon production, quality, taste, and antioxidant capacity, providing theoretical and practical references for their widespread use in agriculture. Full article

Odor-induced sweetness enhancement (OISE) is an effective approach to lower sugar intake. In this study, static and dynamic sensory evaluations, combined with molecular docking, were used to explore the mechanism underlying sweetness enhancement in fructose solutions induced by watermelon juice odor compounds. Sensory evaluation results showed that the seven volatile odor compounds (VOCs) (ethyl acetate, ethyl propionate, octanal, (E,E)-2,4-hexadienal, (E)-2-octenal, methyl heptenone, and geranyl acetone) from watermelon juice could significantly increase the sweetness intensity of a 2.5% fructose solution, and the potency of OISE was significantly enhanced within 10 s. (E,E)-2,4-hexadienal, ethyl propionate, and methylheptenone showed the most significant OISE effects, which aligned with the sensory preference results. Further, molecular docking was used to explore the interactions between VOCs, fructose, and sweet receptors. The results showed that T1R2 was the main receptor for binding fructose and VOCs, and the interaction forces were primarily hydrogen bonds and hydrophobic interactions. In the presence of VOCs, the amino acid residues that formed hydrogen bonds with fructose were highly repetitive, with the main difference being the bond length, indicating the important role of flavor–sweetener receptor interactions in lowering fructose content and enhancing sweetness perception. Thus, this study provides a scientific basis for developing sugar-reduction technology based on aroma, in addition to enhancing sweetness. Full article

The sugar content in watermelon significantly influences its flavor. To understand the sugar accumulation pattern in small-fruited watermelon and identify candidate genes involved in sugar synthesis and conversion, we measured the sugar content (sucrose, fructose, and glucose) at five developmental stages: 10d, 16d, 22d, 28d, and 34d post-pollination. Two watermelon varieties with the largest sugar content difference at 28d post-pollination (high-sugar G38-28 and low-sugar 482276-28) were selected for transcriptome sequencing. Differentially expressed genes (DEGs) were validated using RT-qPCR. Additionally, the sugar contents of three commercial varieties (‘Su Meng NO.5’, ‘Su Meng NO.6’, ‘Su Meng NO.7’) and their parents were compared at five stages. Results showed glucose and fructose levels peaked between 22d and 28d, followed by a decrease, while sucrose content continuously increased. F1 hybrids exhibited glucose and sucrose trends similar to their paternal parent and fructose trends similar to their maternal parent. Transcriptome sequencing identified 9337 DEGs (5072 upregulated and 4265 downregulated). Gene Ontology analysis highlighted overrepresentation in categories such as pectinase and oxidoreductase activity. KEGG analysis identified 12 DEGs involved in sugar synthesis and conversion pathways, including phenylpropanoid biosynthesis and pentose and glucuronate interconversions. RT-qPCR validation corroborated the transcriptome data. These findings explain the distinct sugar accumulation patterns in G38-28 and 482276-28 at the transcriptional level, offering insights for genetic breeding and regulation of key sugar-related genes in watermelon. Full article

To deal with climate emergency and reduce environmental impact, agro-industrial wastes are gradually gaining interest and are being used for new products and applications. The large production of watermelons represents an opportunity because of the many byproducts that can be transformed into innovative and valuable foodstuffs. In this study, we examined the lycopene-rich whole dietary fiber (WDF) obtained from the watermelon pomace of a peculiar cultivar, Gavina^® (Oristano, Italy) a seedless fruit from Sardinia (Italy). The volatile chemical composition of the WDF was investigated using Solid-Phase Microextraction-Gas Chromatography/Mass Spectrometry (SPME-GC/MS). The aim was to follow the evolution of the Volatile Organic Compounds (VOCs) fraction during storage and verify its stability over time. Since watermelon is an excellent source of carotenoids, their byproducts were the most abundant VOCs of the freshly prepared samples, but their overall abundance decreased significantly during storage. The opposite trend was observed for acids and aldehydes, whose increase over time is related to amino acid degradation. Freshly prepared WDF can be used in the food industry as an antioxidant-rich dietary fiber that imparts a characteristic and pleasant aroma. Over time, its aroma profile and carotenoid content change considerably, reducing its health properties and limiting its potential application as a natural flavor. Full article

In this study, the physicochemical properties, antioxidant capacity, and volatile compounds of the juices of different guava cultivars before and after pectinase treatment were evaluated. The results showed that the guava juice of the small fragrant (SF) cultivar exhibited the highest ascorbic acid concentration (1761.09 mg/L), and the highest contents of total phenolics (329.52 mg GAE/L) and total flavonoids (411.13 mg RE/L) were both found in the juice of the watermelon red (WR) cultivar. After pectinase treatment, the juice yield and the titratable acid, sugar components, total phenolics and total flavonoids, and antioxidant capacity levels of the guava juices were all higher than those of the non-pectinase group. However, lower sensory evaluation scores were obtained in the pectinase-treated guava juices. Aldehydes and terpenoids were the main flavor components in the guava juices, which were responsible for the aroma of the juice, while their relative contents were different in the four cultivar guava juices. Furthermore, pectinase treatment could change the amounts and relative contents of volatile compounds in the guava juice. During the pectinase treatment process, the relative contents of the main aroma constituents in the guava juices were significantly decreased. The findings of this research provide valuable information for the processing of guava juice. Full article

Watermelon rind is treated as agricultural waste, causing biomass loss and environmental issues. This study aimed to identify free amino acids and volatiles in watermelon rind, flesh, and rind-flesh juice blends with ratios of 10%, 20%, and 30%. Among the 16 free amino acids quantified, watermelon rind alone contained higher total amino acids (165 mg/100 g fresh weight) compared to flesh alone (146 mg/100 g). The rind had significantly higher (1.5×) and dominant amounts of citrulline and arginine (61.4 and 53.8 mg/100 g, respectively) than flesh. The rind, however, contained significantly lower amounts of essential amino acids. Volatile analysis showed that watermelon rind total volatiles (peak area) comprised only 15% of the flesh volatiles. Of the 126 volatiles identified, the rind alone contained 77 compounds; 56 of these presented in all five samples. Aldehydes and alcohols were most prevalent, accounting for >80% of the total volatiles in all samples. Nine-carbon aldehyde and alcohol compounds dominated both the flesh and rind, though the rind lacked the diversity of other aldehydes, alcohols, ketones, terpenes, terpenoids, esters and lactones that were more abundant in the watermelon flesh. Watermelon rind was characterized by the major aroma compounds above their thresholds, including 17 aldehydes and six unsaturated nine-carbon alcohols. This study demonstrated the potential for rind as a food or beverage supplement due to its key features such as concentrated citrulline and arginine, relatively low odor intensity, and valuable volatiles associated with fresh, green, cucumber-like aromas. Full article

Watermelon rind is treated as agricultural waste and commonly discarded, causing environmental issues and biomass loss. This study aimed to identify volatile profiles of watermelon rind and flesh and their cultivar difference. Volatiles were analyzed using solid-phase microextraction–gas chromatography–mass spectrometry (SPME-GC-MS). A total of 132 volatiles were identified, including aldehydes, alcohols, ketones, terpenes/terpenoids, esters, lactones, acids, and sulfides. In both rind and flesh, the most dominant compounds in numbers and abundance (peak area) were aldehydes and alcohols, which accounted 94–96% of the total volatile abundance in the rind and 85–87% in the flesh. Total volatile in watermelon rind was only 28–58% of the corresponding flesh samples. Both rind and flesh shared nine-carbon aldehydes and alcohols, though the rind lacked additional diversity. Volatile difference between rind and flesh was greater than the difference among cultivars, although volatiles in the rind could be two times difference between Fascination and other three watermelons (Captivation, Exclamation, and Excursion). This study provides the first-hand knowledge regarding watermelon rind volatile profiles and cultivar difference and shows the potential use of rind in food or beverages due to its naturally contained nine-carbon compounds. Full article

The consumption of plant-based dairy alternatives has increased rapidly around the world as a result of numerous positive health effects. Little information is available about the potential use of watermelon seed milk in the manufacture of yoghurt. The present study was undertaken to investigate the remedial action of yoghurt enriched with watermelon seed milk in renal injured hyperuricemic rats. A new yoghurt, substituting cow’s milk with different proportions of watermelon seed milk was prepared, followed by evaluation of its acceptability and functionality. Four different types of yoghurt were prepared from cow’s milk containing 3% fat, with different proportions of blended watermelon seed milk (0.0, 25, 50 and 75%). Sensorial traits, i.e., appearance, flavor, body and texture, and overall acceptability demonstrated that the blended treatment (50% cow’s milk and 50% watermelon seed milk.) was the most acceptable. This blend was then tested as an anti-hyperuricemia agent in rats. In this respect, twenty-four male albino rats were assigned into four groups (n = 6). The first group was solely administered a standard diet, and served as the negative control. The other rats (n = 18) received a basal diet including 20 g/kg dietary potassium oxonate in order to induce hyperuricemia. The hyperuricemic rats were then divided into three groups; the first group did not receive any treatment and served as the positive control, while the second and third groups were administered 10% cow’s milk yoghurt and 10% watermelon seed milk yoghurt, respectively. Interestingly, the results showed that the hyperuricemic group receiving a diet supplemented with 10% watermelon seed milk yoghurt was not significantly different from the negative control in the measured biological parameters, and saw a significant improvement in renal function compared to the positive control. The biologically favorable action of watermelon seed milk yoghurt could be attributed to its potential promotion of antioxidant status via enhancement of the activities of superoxide dismutase, catalase, and glutathione transferase. Collectively, this study concluded that watermelon seed milk can be used in yoghurt manufacturing in proportions of up to 50%, and may improve kidney function as an anti-hyperuricemic agent. Full article

Disposable electronic cigarettes (e-cigarettes) became popular among youth after the Food and Drug Administration (FDA) implemented an enforcement policy to restrict the sale of cartridge-based flavored e-cigarettes starting from February 2020 in the United States (US). We aimed to examine the flavors and topics related to disposable e-cigarettes on Twitter. The Twitter dataset, which includes 1489 tweets, was collected by the Tweepy streamapplication programming interface (API) using a keyword query from March to September 2020. The disposable e-cigarette flavors were curated from both online stores and collected tweets. Topics related to disposable e-cigarettes on Twitter were manually coded. Distributions of topics were compared between tweets from the US and tweets from non-US countries. The temporal analysis results showed a slight increase in the number of discussions over the study period. Strawberry, mango, watermelon, and mint were the most popular flavors of disposable e-cigarettes mentioned on Twitter. Almost all the tweets (97.11%) were commercial tweets, which were dominated by topics related to the product and flavor promotions. The US tweets focused more on product and flavor promotions and less on price promotions compared to non-US tweets. Our results suggest that companies exploited the limitations of legislation to promote flavors on Twitter, which could undermine public health and young people’s finances if they get hooked on addictive products. Full article