Effects of Fruit Bagging Treatment with Different Types of Bags on the Contents of Phenolics and Monoterpenes in Muscat-Flavored Table Grapes

The effects of fruit bagging treatments with seven different types of bags on the physicochemical characteristics of three table grape cultivars: RuiduZaohong (RDZH), RuiduHongyu (RDHY), and RuiduHongmei (RDHM) were investigated. Headspace-solid-phase micro-extraction combined with gas chromatography mass spectrometry (HS-SPME-GC-MS) was used to determine the compositions of monoterpenes in the fruit. The results showed that the total soluble solids in RDZH and RDHY fruits treated with the transparent, mesh, yellow, white, and blue bags were significantly higher than the control. The sugar–acid ratio of RDZH was optimized under the transparent bag and yellow bag treatments, and both significantly increased the sugar-acid ratio of RDHY and RDHM. Additionally, mesh bag, transparent bag, and white bag improved the contents of phenolics to a certain extent. The most abundant volatiles were linalool, geraniol, β-myrcene, β-cis-ocimene, and β-trans-ocimene, of which linalool was the main aroma component. The least squares discriminant analysis results showed that linalool, 4-terpineol, and terpinolen could be used to distinguish the main contribution of different bagging treatments for RDZH. Trans-isogeraniol, α-terpineol, and terpinolen could be used for RDHY. Trans-isogeraniol, β-myrcene, and terpinolen could be used for RDHM. In conclusion, transparent and white bags promoted the accumulation of phenolics and monoterpenes while pink and blue bags showed inhibitory effects.