Metabolic profiling and biochemical analysis of stored Hass avocado fruit by GC‐MS and UHPLC‐UV‐VIS revealed oxidative stress as the main driver of ‘blackspot’ physiological disorder

Abstract

Summary The goal of this study was to use GC‐MS and UHPLC‐UV‐VIS‐based metabolomic tools combined with chemometric analysis to discriminate between fruit with blackspot physiological disorder independently of storage condition (regular air or controlled atmosphere) and without blackspot (hereafter referred to as ‘Control’). The study looked at polar metabolites, enzymes, fatty acids and oxidative stress markers. Fruit with high levels of lenticel damage are more likely to develop blackspot, which appears to be exacerbated by H2O2 and peroxidation of lipids. Lower catalase (CAT), peroxidase (POD), polyphenol oxidase (PPO), superoxide dismutase (SOD) and phenylalanine‐ammonia lyase (PAL) activities together with lower levels of polyphenols (syringic acid, epigallocatechin, quercetin and vanillic) and fatty acids (linolenic, linoleic and palmitic acid), as well as ß‐sitosterol, methyl‐3‐hydroxybutyrate, glyceric acid, hydroxyl butanoic acid, L‐threonic acid, hydroxyl glutaric acid and xylose contributed to a higher prevalence of blackspot disorder in stored Hass avocados, which was accompanied by upregulation of soluble proteins. Finally, chemometric analysis revealed a positive relationship between blackspot disorder with gluconic, palmitoleic, galactose oxime, glyceric, hydroxyglutaric, MDA, syringic and oleic acid, as well as a negative relationship with catechin, epigallocatechin, SOD, CAT and tagatose. The study concluded that oxidative stress is the main driver of ‘Blackspot’ physiological disorder.

Postharvest Storage Differentially Modulates the Enzymatic and Non-Enzymatic Antioxidant System of the Exocarp and Mesocarp of Hass Avocado: Implications for Disorders

“…Previous studies have detected black spots in the exocarp of avocado var Hass after 40 days of cold storage at 5 • C [17]. Likewise, the presence of lenticel damage and black spots was detected in early and middle harvest fruit at the exit of storage under CA at 5 • C (4% O 2 and 6% CO 2 ) for 55 days and regular air at 5 • C for 30 days, as it is more present in regular air storage and middle-harvest avocados [27]. The appearance of dark spots on the exocarp has been associated with low dry matter content [17].…”

“…reported that a large incidence of lenticel damage and lower activity of SOD, CAT, P PAL, phenolics and epicatechin levels may contribute to blackspot development in exocarp during cold storage of Hass avocados [12,27].…”

“…On the other hand, the participation of polyphenoloxidase (PPO) is associated with the development of browning, which is very evident at the mesocarp level of avocados during cold storage [26]. It has been reported that a large incidence of lenticel damage and lower activity of SOD, CAT, POD, PAL, phenolics and epicatechin levels may contribute to blackspot development in the exocarp during cold storage of Hass avocados [12,27].…”

Arabic gum/chitosan/Zn–NPs composite film maintains the quality of Hass avocado fruit by delaying ripening and activating enzymatic defense mechanisms

“…Extraction and determination of fruit enzymes were performed in 1.0 g of frozen fresh fruit tissue 42 .…”