Ripening and Storage Time Effects on the Aromatic Profile of New Table Grape Cultivars in Chile

Aromatic Profiling of New Table Grape Varieties Using Gas Chromatography/Mass Spectrometry and Olfactometry

The aim of this study is the aromatic characterization of new table grape varieties, namely Guzun (V. vinifera), Melona (V. vinifera), Cotton Candy (V. vinifera), IVC SA3 (V. labrusca), and IVC SB1 (V. labrusca). The qualitative and quantitative analysis of odorant molecules present in the berries allows for the definition of the aroma profile of the grape. This analysis benefits from the progress of analytical techniques and sensory methodologies. Gas chromatography/mass detection enable the efficient detection of the substances present and their concentrations. Through the coupling of gas chromatography with sensory detection (gas chromatography-olfactometry), it is possible to correlate the compounds detected by gas chromatography with olfactory stimuli, exploiting the human olfactory system. Aroma, a significant flavor component, is an important attribute of table grape that contributes to defining their quality. This characteristic is highly valued by consumers, and consequently, the market asks for table grapes with a particular or new aroma. Aromatic characterization is a crucial step in the study of the table grape varieties to evaluate their potential at the commercial level or, for instance, in breeding programs focusing on organoleptic properties.

Metabolomic and transcriptomic integrated analysis revealed the decrease of monoterpenes accumulation in table grapes during long time low temperature storage

Low temperature is the commonly used technique for maintaining the quality of table grapes during postharvest storage. However, this technique could strongly affect the aromatic flavor of fruit. Monoterpenes are the key compounds contributing to the Muscat aromas of grapes. The detailed information and molecular mechanisms underlying the changes in monoterpenes during postharvest low temperature storage have not been thoroughly characterized. In this study, the effects of low temperature storage on the free and bound monoterpene profiles in four cultivars of table grape were determined at both the transcriptomic and metabolomic levels. A total of 27 compounds in both free and bound forms were identified in the four cultivars and showed quantitative differences between the cultivars. Hierarchical cluster and principal component analysis indicated that the free and bound monoterpene profiles were remarkably affected by the low temperature storage. The monoterpenes in the same biosynthesis pathway were clustered together and showed similar evolution trends during low temperature storage. And the content of most of free monoterpenes underwent a rapid decline during low-temperature storage at a certain stage, but the time was different in 4 grape cultivars. Transcriptomic analysis revealed that the expression of DXS, HDR, GPPS and TPS genes involved in the monoterpene synthesis pathway were consistent with the changes in the accumulation of monoterpene compounds. While the expression of HMGS, HMGR genes in MVA pathway and branch genes GGPPS and FPPS were negatively correlated with the accumulation of monoterpenes. The findings provide new insights into the underlying mechanisms of the berry aroma flavor change during low temperature storage.

Phenolic, Polysaccharides Composition, and Texture Properties during Ripening and Storage Time of New Table Grape Cultivars in Chile

The aim of this study is to determine the phenolic and polysaccharidic composition, texture properties, and gene expression of new seedless table grape cultivars Timco™ and Krissy™ and compare them to the traditional table grape variety Crimson Seedless (Vitis vinifera L.), during ripening and in commercial postharvest conditions. According to the results, phenolic compounds were present in very different proportions. The total anthocyanins responsible for skin color increased during maturation and the majority anthocyanin in the three cultivars was peonidin-3-glucoside, followed by malvidin-3-glucoside. The phenolic compounds presented a different behavior (decreasing or increasing) during postharvest. The total skin soluble polysaccharides decreased during ripening and postharvest in Crimson Seedless and Krissy™ and remained constant from technological maturity to postharvest storage in Timco™. In all cultivars, the majority soluble polysaccharide fraction was that with a molecular mass between 500 and 35 KDa. The skin mechanical properties of table grapes were good parameters for differentiating varieties, with better results for the new cultivars, compared to the traditional Crimson Seedless, especially in postharvest. Genes involved in the flavonoid pathway and cell wall metabolism in skins exhibited an increase in expression from veraison to remaining constant at the end of the berry ripening.

Study of Volatile Organic Compounds of Two Table Grapes (cv. Italia and Bronx Seedless) along Ripening in Vines Established in the Aegean Region (Turkey)

(1) Background: Italia is a seeded grape variety widely cultivated in the Aegean Region in Turkey, whereas Bronx Seedless is a seedless grape variety, preferred by consumers due to its pink berries and interesting flavor. The goal was to study the volatile compounds of these table grapes throughout berry ripeness. (2) Methods: The volatile compounds were analyzed by GC-MS in six different phenological stages (3) Results: Bronx Seedless grapes presented a higher content of seven terpenes, three aldehydes, one fatty acid, three alcohols, one C6 compound, total aldehydes and total alcohols, and a lower content of eleven terpenes, one fatty acid, four esters, one alcohol, four C6 compounds and its total content than Italia table grapes. The concentration of most of the volatile compounds analyzed increased from “begin of berry touch” to “berries ripe for harvest” stages. Terpenes content in both varieties at harvest was lower than 1.0 mg L−1. β-ionone presented the highest odor activity value (OAV) in both varieties. Bronx Seedless grapes presented higher OAV for (Z)-3-hexenal and cedrol, and lower hexanal to (E)-2-hexenal ratio than Italia grapes. (4) Conclusions: Both varieties could be classified as neutral aromatical varieties and it is probable that to achieve a better aromatic quality, Bronx Seedless should be harvested later than Italia.