Chilling temperatures and controlled atmospheres alter key volatile compounds implicated in basil aroma and flavor

Abstract

Use of basil in its fresh form is increasingly popular due to its unique aromatic and sensory properties. However, fresh basil has a short shelf life and high chilling sensitivity resulting in leaf browning and loss of characteristic aroma. Moderate CO2 atmospheres have shown potential in alleviating symptoms of chilling injury in basil during short-term storage but its effect on the flavor volatiles is unclear. Moreover, studies on basil volatile profile as impacted by chilling temperatures are limited. We investigated the response of two basil genotypes to low temperatures and atmosphere modification, with emphasis on the volatile organic compounds responsible for basil aroma and flavor. Leaves were stored for 6 days at 5, 10, or 15°C combined with three different CO2 atmospheres (0.04%, 5% or 10%). Basil volatile profile was assessed using headspace solid phase microextraction (HS-SPME) coupled with gas chromatography-mass spectrometry (GC-MS). Leaves suffered severe chilling injury and greater loss of aroma volatiles at 5°C compared to 10°C and 15°C. More than 70 volatiles were identified for each genotype, while supervised multivariate analysis revealed 26 and 10 differentially-accumulated volatiles for ‘Genovese’ and ‘Lemon’ basil, respectively, stored at different temperatures. Storage in 5% CO2 ameliorated the symptoms of chilling injury for up to 3 days in ‘Genovese’, but not in ‘Lemon’ basil. Both chilling temperatures and controlled atmospheres altered key volatile compounds implicated in basil aroma and flavor, but temperature had a bigger influence on the observed changes in volatile profile.

Preharvest and postharvest techniques that optimize the shelf life of fresh basil (Ocimum basilicum L.): a review

“…Although 0% CO 2 is ideal for basil storage in N 2 , slightly raising CO 2 levels may benefit storage under ambient air. Storage in 5% CO 2 at 5°C minimized the symptoms of chilling injury for up to 3 days in Genovese sweet basil, though not in lemon basil when compared to 0.04% CO 2 (Rodeo and Mitcham, 2023). Although the conclusions of this study cannot be certain as they did not standardize O 2 levels, the results are consistent with a prior study that found adding 2.5 kPa CO 2 to air effectively inhibited leaf abscission, decay and browning in storage at 12°C for 7 days, especially when combined with a single pre-treatment of 0.7 mmol•L -1 1-methylcyclopropene (1-MCP), which is a synthetic growth regulator used to maintain freshness (Kenigsbuch et al, 2015).…”

“…Sudden declines in basil volatile compounds have been observed even earlier after only 3 days at 5°C (Rodeo and Mitcham, 2023). While some secondary metabolites such as carotenoids and a Minimize chilling injury (Lange and Cameron, 1994;Lange and Cameron, 1997;Meir et al, 1997;Rodeo and Mitcham, 2023), microbial growth (da Silva et al, 2005;Delbeke et al, 2015) and loss of volatile aroma compounds, polyphenols and antioxidants (Sharma et al, 2005;Loṕez-Blancas et al, 2014;Cozzolino et al, 2016;Ghasemzadeh et al, 2016;Fratianni et al, 2017;Rodeo and Mitcham, 2023) Artificial handful of volatile compounds were better conserved at 4-5°C compared to 12-20°C, relatively higher storage temperatures are favorable for the major volatiles responsible for aroma in basil (Loṕez-Blancas et al, 2014;Cozzolino et al, 2016;Rodeo and Mitcham, 2023). Contrary to preserving leaf freshness and aroma, storing basil at cooler temperatures of <15°C is favorable for inhibiting fungi and bacteria (da Silva et al, 2005;Delbeke et al, 2015).…”

“…However, severe chilling injury occurs in basil at storage temperatures of 5°C and below. Basil leaves blacken from necrosis in as little as 1 day at 0°C or 3 days at 5°C (Lange and Cameron, 1994;Lange and Cameron, 1997;Meir et al, 1997;Brindisi et al, 2021;Rodeo and Mitcham, 2023). Moderate chilling injury occurs at 7.5-10°C and ceases at temperatures of 12°C and greater (Lange and Cameron, 1994;Meir et al, 1997;Loṕez-Blancas et al, 2014).…”