Grape Berry Flavonoid Responses to High Bunch Temperatures Post Véraison: Effect of Intensity and Duration of Exposure

Climate models predict an increase in the frequency and duration of heatwaves with an increase in intensity already strongly evident worldwide. The aim of this work was to evaluate the effect of two heatwave-related parameters (intensity and duration) during berry ripening and identify a threshold for berry survival and flavonoid accumulation. A Doehlert experimental design was used to test three temperature intensities (maxima of 35, 46, and 54 °C) and five durations (3 to 39 h), with treatments applied at the bunch level shortly after véraison. Berry skin and seeds were analysed by liquid chromatography-triple quadrupole-mass spectrometry (LC-QqQ-MS) for flavonoids (flavonols, anthocyanins, free flavan-3-ols, and tannins). Berries exposed to 46 °C showed little difference compared to 35 °C. However, berries reaching temperatures around 54 °C were completely desiccated, and all flavonoids were significantly decreased except for skin flavonols on a per berry basis and seed tannins in most cases. Some compounds, such as dihydroxylated flavonoids and galloylated flavan-3-ols (free and polymerised), were in higher proportion in damaged berries suggesting they were less degraded or more synthesised upon heating. Overall, irreversible berry damages and substantial compositional changes were observed and the berry survival threshold was estimated at around 50–53 °C for mid-ripe Shiraz berries, regardless of the duration of exposure.

Analysis of the Volatile Components of Pouteria sapota (Sapote Mamey) Fruit by HS-SPME-GC-MS

The comparison of SPME fiber coatings, and optimization of temperature and time of extraction for headspace solid phase microextraction (HS-SPME) of volatile organic compounds (VOCs) present in Pouteria sapota (sapote mamey) fruits is presented. The PDMS/DVB coating afforded the highest extraction efficiency. The extraction conditions were optimized by using Doehlert experimental design. By using the optimized HS-SPME method, 21 VOCs were identified, which include mainly terpenoids and esters, followed by aromatic hydrocarbons, aldehydes, alcohols and ketones. The most abundant compounds in Pouteria sapota pulp were cedrol (25.0%), azulene (7.3%), β-ionone (5.7%) naphthalene (5.6%), α-pinene (5.0%), and benzaldehyde (4.3%). Seventeen VOCs were identified for the first time in the fruit.