Insights into key aroma of vine tea (Ampelopsis grossedentata) for grade evaluation integrating relative odor activity value,gas chromatography-olfactometry and chemometrics approaches

It is an urgent requirement to explore the key aroma of vine tea to provide the guidance for tea quality evaluation. In this study, three levels of vine tea of bud tip, tender leaf, and aged leaf were characterized by headspace-solid phase microextraction-gas chromatography-mass spectrometry (HS-SPME/GC-MS). The relative odor activity value (rOAV) calculation coupled with gas chromatography-olfactometry (GC-O) technology were implemented to seek the aroma-active compounds. Afterwards, the chemometrics methods were employed to explore the critical volatile compounds on the basis of S-line, variable importance for projection (VIP), jack-knifing confidence interval, p values (<0.05), and fold change (FC). As a result, five aroma compounds of ethyl acetate, (E,E)-2,4-heptadienal, geraniol, hexanal, and geranyl acetone were considered as key markers by taking an overall consideration of rOAV, GC-O and chemometrics methods. Finally, the mathematical equation of the vine tea grade with respect to the key aroma was established. The ethyl acetate and geraniol were positively related with the vine tea level evaluation, whereas the hexanal, geranyl acetone, and (E,E)-2,4-heptadienal were negatively correlated with the tea grade, among which the hexanal played a significant role on tea level assessment. This study provides compelling evidence for the vine tea quality evaluation in the perspective of key aroma compounds.     

Impact of pectin edible coating extracted from cacao shell powder on postharvest quality attributes of tomato (Lycopersicon esculentum Mill.) fruit during storage

This study aimed to optimize pectin extraction from crude cacao shell (CS) powder using chemical method (pH 4 and 10, temperatures 60–80 °C), ultrasound-assisted extraction (UAE) method (sonication time 20–40 min), and enzymatic method (pectinase 0.5–1.0% v/v, temperature 40–60 °C, and time 120–240 min). The optimal extraction condition with highest CS pectin yield was enzymatic followed by chemical and UAE methods. The pectin extracted from cocoa shell from all extraction methods had the degree of esterification (DE%) greater than 50% which was categorized as high methoxyl (HM) pectin. The prebiotic activity and viscosity of pectin from the optimal extraction conditions with highest pectin yield for each extraction method were studied. Pectin extracted via UAE method with highest prebiotic activity (p≤0.05), was selected for edible coating of tomato and quality changes were evaluated during 30 days of storage at 4 °C. The results showed that tomato coated with pectin-based edible coating (TWP) retained physicochemical properties (e.g., color, total soluble solid, pH, firmness, weight loss), and bioactivity (e.g., lycopene, total phenolic compound and antioxidant activity), compared with control (CON) and tomato coated with no pectin (TNP). In addition, the total viable count and yeast and mold count of TWP was the lowest among other treatments. Therefore, pectin-based edible coating was able to delay the quality changes and extend the shelf life of TWP sample up to 27 days at 4 °C.