Volatile Compounds and Sensory Properties in Various Melons, Which were Chosen from Different Species and Different Locations, Grown in Turkey

Thorough Characterization of ETHQB3.5, a QTL Involved in Melon Fruit Climacteric Behavior and Aroma Volatile Composition

The effect of the QTL involved in climacteric ripening ETHQB3.5 on the fruit VOC composition was studied using a set of Near-Isogenic Lines (NILs) containing overlapping introgressions from the Korean accession PI 16375 on the chromosome 3 in the climacteric 'Piel de Sapo' (PS) genetic background. ETHQB3.5 was mapped in an interval of 1.24 Mb that contained a NAC transcription factor. NIL fruits also showed differences in VOC composition belonging to acetate esters, non-acetate esters, and sulfur-derived families. Cosegregation of VOC composition (23 out of 48 total QTLs were mapped) and climacteric ripening was observed, suggesting a pleiotropic effect of ETHQB3.5. On the other hand, other VOCs (mainly alkanes, aldehydes, and ketones) showed a pattern of variation independent of ETHQB3.5 effects, indicating the presence of other genes controlling non-climacteric ripening VOCs. Network correlation analysis and hierarchical clustering found groups of highly correlated compounds and confirmed the involvement of the climacteric differences in compound classes and VOC differences. The modification of melon VOCs may be achieved with or without interfering with its physiological behavior, but it is likely that high relative concentrations of some type of ethylene-dependent esters could be achieved in climacteric cultivars.

Study on the differences in aroma components and formation mechanisms of "Nasmi" melon from different production areas

Aroma is an important factor that guides consumers in purchasing and is thus very important in melon research. To our knowledge, the number of studies with a focus on the aroma differences of the same melon variety in different production areas is largely limited. In this study, the differences in aroma components of "Nasmi" melons from two different production regions were analyzed using gas-phase ion migration spectroscopy. Transcriptome sequencing was performed for analyzing fragrance-related genes. Results showed that there were significant differences in the aroma components between products from the two regions. The total amount of aroma compounds from the Turpan region (TT) was 1.7 times higher than that from the Altay region (AT). Through the analysis of transcriptome data, the key genes encoding melon aroma components in different regions were identified as ethanol dehydrogenase, 3-hydroxyl-coenzyme A (CoA) dehydrogenase, acyl-CoA oxidase, long-chain acyl-CoA synthetase, acetaldehyde dehydrogenase, and acetyl-CoA acyltransferase. Real-time quantitative polymerase chain reaction (RT-qPCR) showed that the verified genes were similar to the transcriptome. In this study, the main aroma components of the same variety of melon that differed in different production areas and the key genes causing these differences were identified. In addition, the aroma metabolic pathway of melon in different regions was preliminarily elucidated. These results could provide a theoretical basis for further study of the formation mechanism of melon aroma and breeding.

Bioactive compounds from Cucumis melo L. fruits as potential nutraceutical food ingredients and juice processing using membrane technology

The present study was designed to evaluate the nutritional composition of melon pulp Maazoun variety, in order to explore its potential attitude as a natural source of nutrients and bioactive molecules. The chemical characterization showed that the pulp was rich in moisture, carbohydrate, dietary fibers, and minerals, as well as carotenoids and phenolic compounds. The chromatographic analysis indicated that amentoflavone (16.14 mg/100 g) and gallic acid (13.56 mg/100 g) were the most abundant phenolic compounds. Melon flesh has an interesting volatile profile in which, mostly esters and alcohols are considered as the key odorants of this appreciated fruit. Melon juice was filtered through crossflow microfiltration that provides more translucent juice and accentuation of yellow color. During clarification process, the permeate flux was reduced by 50% in approximately 40 min. Results proved that the richness of melons in nutrients and bioactive phytochemicals makes them useful as a potential source of antioxidants and suitable as nutraceutical supplements.

Comparative Analysis of VOCs from Winter Melon Pomace Fibers before and after Bleaching Treatment with H2O2

In this study, the trend of Volatile Organic Compounds (VOCs) in dietary fiber samples from the winter melon (Cucumis Melo var. Inodorus, Yellow Canary type) were investigated. This foodstuff, obtained as a by-product of agri-food production, has gained increasing attention and is characterized by many bioactive components and a high dietary-fiber content. As regards fiber, it is poorly colored, but it may be whitened by applying a bleaching treatment with H₂O₂. The result is a fibrous material for specific applications in food manufacturing, for example, as a corrector for some functional and technological properties. This treatment is healthy and safe for consumers and widely applied in industrial food processes. In this study, a method based on headspace solid-phase microextraction (HS-SPME) coupled with gas chromatography–mass spectrometry (GC-MS) was applied for the characterization of the aromatic profile of the dried raw materials. Furthermore, VOC variation was investigated as function of the bleaching treatment with H₂O₂. The bleached samples were also analyzed after a long storage period (24 months), to assess their stability over time. As a result, the VOC fraction of the fresh raw fiber showed nine classes of analytes; these were restricted to seven for the bleached fiber at t₀ time, and further reduced to four classes at the age of 24 months. Alcohols were the main group detected in the fresh raw sample (33.8 % of the total chromatogram area), with 2,3-butanediol isomers as the main compounds. These analytes decreased with time. An opposite trend was observed for the acids (9.7% at t₀), which increased with time and became the most important class in the 24-month aged and bleached sample (57.3%).

Effect of high oxygen and high carbon dioxide atmosphere packaging on the microbial spoilage and shelf-life of fresh-cut honeydew melon

This study evaluated the potential of modified atmospheres (MAs) combining high oxygen (O₂) and high carbon dioxide (CO₂) levels to extend the shelf-life of fresh-cut honeydew melon. Firstly, the effect of MA on the growth and volatile organic metabolite production of Candida sake, Leuconostoc mesenteroides and Leuconostoc gelidum, which had all been previously isolated from spoiled commercial fresh-cut honeydew melon, was evaluated separately on honeydew melon agar at 7 °C. Additionally, the effect of selected MAs on the microbial, physico-chemical and sensory quality of commercial fresh-cut honeydew melon cubes was evaluated at 7 °C. The results showed that MAs with high O₂ and high CO₂ levels greatly retarded the growth, CO₂ and volatile metabolite production (i.e. ethanol, 2-methyl-1-butanol, ethyl acetate, phenylacetic acid, nonanal) of C. sake on honeydew melon agar; especially MAs consisting of 50% O₂+50% CO₂ and 70% O₂+30% CO₂. In contrast, the MAs evaluated only had a minor effect on the growth and volatile metabolite production of L. mesenteroides and L. gelidum. Overall, the effect of MAs on colour, juice leakage, juiciness, and firmness of fresh-cut honeydew melon was small during storage. Sensory preference was generally for fresh-cut honeydew melon cubes packaged in MA of 50% O₂+50% CO₂. These were still acceptable on day five of storage and had appreciably lower populations of yeasts and lactic acid bacteria, lower quantities of volatile organic compounds, but slightly stronger colour oxidation compared to honeydew melon that was packaged in air. Additionally, most of the samples packed in air had blown by day five due to the large quantity of CO₂ production during storage. Therefore, 50% O₂+50% CO₂ is a potential MA solution for extending the shelf-life of fresh-cut honeydew melon.