Biochemical Basis of CO2-Related Internal Browning Disorders in Pears (Pyrus communis L. cv. Rocha) during Long-Term Storage

Antioxidant effects of phenolic extract from sugarcane straw and mannan extract from brewer's spent yeast on fresh-cut apples

BACKGROUND

Fresh-cut fruit are convenient ready-to-eat products increasingly demanded by consumers, but highly susceptible to oxidation. To increase the shelf life of these products, this industry is currently facing the challenge of finding sustainable natural preservatives capable of maintaining fresh-cut fruit quality while meeting consumers' expectations regarding health and environmental concerns.

RESULTS

In this work, fresh-cut apple slices were treated with two antioxidant extracts derived from industrial by-products: a phenolic-rich extract produced from sugarcane straw (PE-SCS) and applied at 15 g L-1 , and a mannan-rich extract obtained from brewer's spent yeast (MN-BSY) applied at two concentrations: 1 and 5 g L-1 . PE-SCS, having a brown color, imparted a brownish hue to the fruit and increased the browning rate during storage, and not even the initial robust antioxidant response (high superoxide dismutase, catalase, ascorbate peroxidase and guaiacol peroxidase activities), prevented oxidation. Fruit treated with MN-BSY extract at 5 g L-1 showed lower color loss rate and higher polyphenol oxidase inhibition, while at 1 g L-1 it showed lower firmness loss rate and lower lipid peroxidation after 6 days of storage.

CONCLUSION

The results showed that PE-SCS triggers a potent antioxidant response in fresh-cut fruit and, despite it imparting a brown color to the fruit at 15 g L-1 , it may have potential for application at lower concentrations. Regarding MN-BSY, it generally decreased oxidative stress, but its effect on quality maintenance was dependent on the concentration and, thus, to confirm its potential as a fruit preservative more concentrations must be tested. © 2023 Society of Chemical Industry.

Effect of Nano-SiOx/Chitosan Complex Coating on the Physicochemical Characteristics and Preservation Performance of Green Tomato

A novel nano-silicon oxides (SiOx)/chitosan complex film was prepared using ultrasonic assistant in the process of dissolving chitosan and silicon oxides (SiOx), and characterized by transmission electron microscopy. Its effect on quality preservation of tomatoes (Solanum lycopersicum L. cv. Zheza 205) was investigated under ambient temperature. The results revealed that the nano-SiOx/chitosan complex (NSCC) film retarded weight loss and softness, delayed the titratable acids and total soluble solids loss, and thus markedly extended shelf life of green tomatoes. The antimicrobial activity of tomatoes coated with NSCC film was also recorded higher compared to chitosan (Ch) films and control. In addition, the NSCC film-coated tomatoes prevent the increase of malondialdehyde content and total polyphenol content. Moreover, the peroxidase activity, phenylalanine ammonia-lyase activity, and polyphenoloxidase activity of tomatoes coated with NSCC film were found lower than that in other treatments. These data indicated that the beneficial effects of nano-SiOx/chitosan complex coating on postharvest quality were possibly associated with the lower rate of O₂/CO₂ transmission coefficient, limiting food-borne pathogenic bacterial growth, higher antioxidant activities, and also higher reactive oxygen species (ROS) scavenging and anti-browning activities of related enzymes in the tomatoes. Further, the results of the study could be used to successfully develop a novel nano-SiOx/chitosan complex film for improving the postharvested quality of tomatoes and thus effectively utilized by the food packaging industry.

Methyl Jasmonate Promotes Phospholipid Remodeling and Jasmonic Acid Signaling To Alleviate Chilling Injury in Peach Fruit

Chilling injury (CI) is a physiological disorder induced by cold, which heavily limit crop production and postharvest preservation worldwide. Methyl jasmonate (MeJA) can alleviate CI in various fruit species, including peach; however, the underlying molecular mechanism is poorly understood. Here, changes in contents of phenolics, lipids, and jasmonic acid (JA) and gene expressions are compared between MeJA and control fruit. Exogenous MeJA inhibited expressions of PpPAL1, PpPPO1, and PpPOD1/2 but did not affect the phenolic content. Furthermore, MeJA fruit showed lower relative electrolyte leakage, indicating less membrane damage. Meanwhile, the enrichment of linoleic acid in the potential lipid biomarkers, especially phosphatidylcholine, phosphatidylethanolamine, and phosphatidylglycerol, coincided with lower expressions of PpFAD8.1 but higher PpLOX3.1 and JA content. In the JA signaling pathway, MeJA significantly upregulated expressions of PpMYC2.2 and PpCBF3 but downregulated PpMYC2.1. In conclusion, adjustments of fatty acids in phospholipids contribute to MeJA-induced alleviation of CI in peach fruit via induction of the JA-mediated C-repeat-binding factor pathway.

Metabolic Alterations in Postharvest Pear Fruit As Influenced by 1-Methylcyclopropene and Controlled Atmosphere Storage

This study assessed the impact of 1-methylcyclopropene (1-MCP) and controlled atmosphere (CA) on the metabolism of targeted amino acids, organic acids, and antioxidants in stored 'AC Harrow Crisp' pears and their relationships to storage disorders. Pears were treated with 0 or 300 nL L^-1 1-MCP and stored at 0 °C under ambient air or CA. Spectrophotometric assays demonstrated that glutathione levels fluctuated with storage and were most preserved by 1-MCP under ambient air. HPLC analysis revealed that ascorbate concentrations declined with storage and were little affected by 1-MCP and CA. Citrate, lactate, and fumarate accumulated with storage but were differentially affected by 1-MCP. Aspartate and glutamate concentrations were greater with 1-MCP; γ-aminobutyrate accumulated in disordered fruit. Principal component analysis demonstrated that alterations in citrate and fumarate were, respectively, correlated with internal breakdown and senescent scald. γ-Aminobutyrate and alanine were associated with internal cavities. All disorders were associated with antioxidant depletion.

De novo sequencing and analysis of the transcriptome during the browning of fresh-cut Luffa cylindrica 'Fusi-3' fruits

Fresh-cut luffa (Luffa cylindrica) fruits commonly undergo browning. However, little is known about the molecular mechanisms regulating this process. We used the RNA-seq technique to analyze the transcriptomic changes occurring during the browning of fresh-cut fruits from luffa cultivar 'Fusi-3'. Over 90 million high-quality reads were assembled into 58,073 Unigenes, and 60.86% of these were annotated based on sequences in four public databases. We detected 35,282 Unigenes with significant hits to sequences in the NCBInr database, and 24,427 Unigenes encoded proteins with sequences that were similar to those of known proteins in the Swiss-Prot database. Additionally, 20,546 and 13,021 Unigenes were similar to existing sequences in the Eukaryotic Orthologous Groups of proteins and Kyoto Encyclopedia of Genes and Genomes databases, respectively. Furthermore, 27,301 Unigenes were differentially expressed during the browning of fresh-cut luffa fruits (i.e., after 1-6 h). Moreover, 11 genes from five gene families (i.e., PPO, PAL, POD, CAT, and SOD) identified as potentially associated with enzymatic browning as well as four WRKY transcription factors were observed to be differentially regulated in fresh-cut luffa fruits. With the assistance of rapid amplification of cDNA ends technology, we obtained the full-length sequences of the 15 Unigenes. We also confirmed these Unigenes were expressed by quantitative real-time polymerase chain reaction analysis. This study provides a comprehensive transcriptome sequence resource, and may facilitate further studies aimed at identifying genes affecting luffa fruit browning for the exploitation of the underlying mechanism.

Biochemical markers to predict internal browning disorders in 'Rocha' pear during storage under high CO2

BACKGROUND

The aim of this study was to identify biochemical markers to predict internal browning disorders (IBD) in 'Rocha' pear. Fruits from five orchards were stored for 45 days under cold air followed by 100 days in browning-inducing controlled atmosphere (CA) conditions (1 kPa O₂ + 10 kPa CO₂ ).

RESULTS

Relationships between concentrations of ethanol (EtOH), acetaldehyde (AcDH) and ascorbic acid (AA), activities of peroxidase (POX) and polyphenoloxidase (PPO) and IBD incidence were established. The partial least square (PLS) model using the most promising markers, EtOH and AcDH, explained 89% of the variance in IBD incidence, whereas the univariate models based on the same markers explained between 89 and 94%. In contrast, the models based on AA levels and AA depletion rate only explained 57 and 82% of the variance in IBD incidence respectively. Model validation confirmed the robustness of EtOH for the prediction (R²  = 0.91, RMSE = 11.1) and allowed proposing a threshold level of 30 µL EtOH L^-1 above which IBD may occur. Using this threshold value, the storage time limit associated with the occurrence of the first IBD symptoms was predicted with an acceptable RMSE of 9 days.

CONCLUSION

This work clearly identifies biochemical IBD markers for 'Rocha' pear and shows that dynamic changes in ethanol concentration during the beginning of storage may be used to predict IBD development. Therefore the results presented herein represent a major step forward in the prediction of IBD in 'Rocha' pear. © 2017 Society of Chemical Industry.