The effects of the level of berry thinning (30% and 50% berry removal) on the quality and sensory properties of Shine Muscat grapes were investigated. As berry thinning increased, the total soluble solids content increased and titratable acidity decreased. Berry thinning increased berry size and cluster weight but caused no change in individual berry weight. Phenolic concentrations as measured by total phenolic, proanthocyanidin, and polymeric tannin concentrations tended to increase with an increase in berry thinning. Gas chromatographic analysis indicated that C6-compounds were the significant constituents of volatile alcohols and aldehydes; linalool was the most abundant monoterpene. Odor activity analysis indicated that (E)-2-hexen-1-ol, (E)-2-hexenal, 1-hexanal, (Z)-3-hexenal, (E)-β-damascenone, linalool, and (E)-linalool oxide were active odorants. Berry thinning increased the accumulation of linalool contributing to high sensory flavor scores in thinned berries. Furthermore, its oxidized derivative-linalool oxide-contributed to enhancing the Muscat flavor. In conclusion, berry thinning induced compositional changes in Shine Muscat grape berries by accelerating the ripening rate, contribution to improved sensory properties.

Changes in the biochemistry and flavor of Shine Muscat grapes at different ripening stages (RS) were analyzed to identify factors affecting these characteristics. The yellowness index values were 45.1, 49.4, and 50.2 in the ripening stage 1 (RS1), ripening stage 2 (RS2), and ripening stage 3 (RS3) groups, respectively, representing the different ripening stages. The yellowness of the grape berries tended to increase with ripening due to the gradual breakdown of chlorophylls and the evolution of carotenoids. The total content of monoterpenes, on the other hand, was approximately two-fold higher at RS3 than RS1 and RS2. Moreover, linalool was the most abundant compound contributing to the total content of monoterpenes. The highest correlation was observed between the linalool content and °Brix/acid ratio (r = 0.9981), followed by the monoterpene content and °Brix/acid ratio (r = 0.9933). These findings indicate that changes in the contents of linalool and its oxidized forms may be used as a quality index and an indicator of the timing of harvest for Shine Muscat grapes.

The astringent sensation of wines is attributable to the composition and concentration of phenolic compounds. However, in many cases, experimental results have shown a gap in relation to sensory astringency. The aim of the present study was to evaluate the relationships between the experimental evidence of astringent attributes and perceived astringency. To this end, the concentrations of phenolic compounds, namely, the total phenolic content (TPC), the polymeric tannin content (PTC), the proanthocyanidin content (PAC) and the total anthocyanin content (TAC), in wines made from a variety of grape breeding lines were estimated and their relationships to perceived astringency were evaluated. The TPC and the PTC showed strong positive correlations with perceived astringency. In contrast, the PAC showed a moderate correlation with perceived astringency, which was lower than that shown by the PTC despite their similar phenolic compositions. Unlike the other attributes, the TAC showed a weak correlation with perceived astringency. We concluded that the TPC and the PTC showed good correlations with perceived astringency and could be used as an index for predicting the astringency of wines.

The effects of instrumental quality indices on the sensory properties of Shine Muscat grapes harvested 16, 18, 20, and 22 weeks after full bloom (WAFB) were investigated. The berries harvested at 20 and 22 WAFB gained higher sweetness scores than those harvested at 16 and 18 WAFB, showing similar trends to that of total soluble solids (TSS) content. The sourness, astringency, and firmness scores were not significantly different among the samples. The flavor score showed a trend similar to that of sweetness perception. The higher flavor score in the berries harvested at 20 and 22 WAFB seemed to be derived from the development of floral aroma compounds, including linalool and its derivatives, with ripening. Consumer acceptance was highly correlated with sweetness and flavor perceptions. It was concluded that the TSS content and development of floral aroma compounds are the key quality parameters for Shine Muscat grapes, satisfying consumer acceptability in the market.

Grape (Vitis vinifera L.) is a perennial fruit tree with high heterozygosity, consisting of 38 chromosomes (2n=38), and it takes a long time for grape seedlings to grow into fruit-bearing trees. Therefore, it is difficult to study grape genetics and breeding strategies. However, it has recently become possible to discover many SNPs through whole genome resequencing or genotyping-by-sequencing (GBS) analysis. In this study, we aimed to develop high-resolution melting (HRM) markers from the detected SNPs and construct a genetic linkage map using HRM markers. In a previous study, 2,553 SNPs were identified using GBS analysis. In this study, 1,336 SNPs were used to design primer sets for HRM analysis. The developed HRM markers were used for construction of a genetic linkage map in an F 1 segregating population consisting of 192 individuals from a cross between 'Tano Red' (V. labrusca × V. vinifera) and 'Ruby Seedless' (V. vinifera). A total of 805 polymorphic HRM markers were developed, of which 363 were mapped onto the genetic linkage map of grape, with a total length of 1,453.5 cM consisting of 19 chromosomes. This SNP-based genetic linkage map and HRM markers can be used for QTL identification and marker development for important fruit traits of grape.