Free versus droplet-bound aroma compounds in sparkling beverages

The initial experience of a beverage's flavor after opening the bottle is created by a combination of the gas phase and droplet-bound odorants. However, most studies do not consider this combination, and focus on the odor-active components in the liquid or gas phase, separately. To cover this aspect, a filter from pyrolyzed polyacrylonitrile fiber was packed inside thermal desorption unit liner and used for trapping droplet-bound odorants. Additionally, polydimethylsiloxane coated thin-film was applied for extraction of gas-phase aroma. Following trapping/extraction, the devices were desorbed and compounds were separated using GC-MS. The odorants in commercial sparkling beverages were quantified immediately after opening the bottle to mimic real-life conditions of the consumer's experience of the flavor. The reported results provide a more comprehensive understanding of flavor perception in effervescent drinks by considering both gas and droplet phase.

Soil nutrient deficiency decreases the postharvest quality-related metabolite contents of tea (Camellia sinensis (L.) Kuntze) leaves

The long-term cultivation of tea plants without fertilization can severely decrease yield, but it remains unclear whether this soil nutrient deficiency affects tea quality. In this study, tea plants (Camellia sinensis (L.) Kuntze) cultivated in unfertilized soil for 11 years were analyzed. The soil nutrient deficiency down-regulated protochlorophyllide oxidoreductase-encoding gene expression, which adversely affected chlorophyll biosynthesis, ultimately leading to leaf etiolation. Because of decreased synthesis and increased degradation in response to nutrient deficiency, l-theanine content decreased to 11.4% of the control level, which increased the phenol-ammonia ratio and decreased taste quality. Soil nutrient deficiency also decreased the abundance of many aroma compounds (e.g., green leaf volatile, linalool and its oxides, and methyl salicylate). Thus, nutrient deficiency adversely influences tea color, taste, and aroma. This study provides researchers and tea growers with important information regarding the effects of soil nutrient deficiency on tea quality and the rational fertilization of tea gardens.

Characterization of key aroma compounds and relationship between aroma compounds and sensory attributes in different aroma types of Fu brick tea

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Aroma characteristics of Fu brick tea were classified into three types.

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Key aroma compounds in three aroma types of Fu brick tea were identified.

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Relationship between aroma compounds and aroma attributes was illuminated.

Aroma is one of the most important sensory properties of tea. Floral-fungal aroma type, ripe-fungal aroma type and fresh-fungal aroma type were the main aroma types of Fu brick tea by QDA. A total of 112 volatile compounds were identified and quantified in tea samples by HS-SPME/GC–MS analysis. Ten voaltiles in floral-fungal aroma type, eleven voaltiles in ripe-fungal aroma type, and eighteen voaltiles in fresh-fungal aroma type were identified as key aroma compounds for the aroma characteristics formation in three aroma types of Fu brick tea. In addition, PLS analysis revealed that 3,4-dehydro-β-ionone, dihydro-β-ionone, (+)-carotol and linalool oxide Ⅱ were the key contributors to the ‘floral and fruity’ attribute, α-terpineol contributed to ‘woody’ and ‘stale’ attributes, and thirteen aroma compounds related to ‘green’ attribute. Taken together, these findings will provide new insights into the formation mechanism of different aroma characteristics in Fu brick tea.