Influence of 1-Methylcyclopropene (1-MCP) on Postharvest Storage Quality in Green Bell Pepper Fruit

Recent advances on postharvest technologies of bell pepper: A review

The bell pepper (Capsicum annuum L.) is a commercially important horticultural crop grown in tropical and sub-tropical areas across the world. Despite this importance, it is a perishable vegetable with a limited shelf life and high disease susceptibility. Bell pepper output has expanded significantly in recent years. However, this crop is still experiencing close to 40% postharvest losses annually. Chemical fumigation for postharvest disease control of bell pepper has been shown to be efficient against fungal infections, but environmental impact and consumption hazards limit its full use. Recently, non-chemical techniques including biological and botanical methods, non-destructive technologies and Artificial intelligence have been demonstrated to be effective as postharvest management of bell pepper. The paper provides exciting information on recent and emerging techniques for curtailing these losses in bell pepper, alongside their mechanism and existing benefits. The current limitations of these techniques as well as recommendations for potential applications are also addressed.

Effects of 1-Methylcyclopropene Combined with Modified Atmosphere on Quality of Fig (Ficus carica L.) during Postharvest Storage

Fig (Ficus carica L.) is a highly nutritious fruit, which is rich in sugar, protein, amino acids, vitamins, and mineral elements. However, figs are perishable climacteric fruits, causing difficulty in postharvest storage and preservation. 1-Methylcyclopropene (1-MCP) and modified atmosphere (MA) are preservation methods with many applications, but the effects of their combination on quality of fig during postharvest storage have rarely been studied. The objective of this study was to investigate the effects of MA and MA+1-MCP treatments on postharvest quality of fig fruit stored at −1 ± 0.5°C for 30 days. The results showed that the MA+1-MCP treatment significantly improved the fruit texture, reduced the weight loss rate and malonaldehyde (MDA) accumulation, and inhibited the ethylene production and respiration rate compared with that in the control and MA groups. In summary, the MA+1-MCP treatment will be a good preservation method to maintain fruit quality of figs during postharvest storage.

1-MCP treatment affects peach fruit aroma metabolism as revealed by transcriptomics and metabolite analyses

1-methylcyclopropene (1-MCP) negatively affects peach aroma but the underlying molecular basis remains elusive. In this study, transcriptomics and metabolite analyses were carried out to investigate the regulatory mechanisms of 1-MCP on peach aroma from different standpoints: fatty acid (FA) metabolism, ethylene signal transduction and lipoxygenase/β-oxidation pathway during 20 °C storage. Results indicate that 1-MCP significantly postponed the ethylene climacteric peak appearance and reduced ethylene production through down-regulation of related biosynthesis and signal transduction genes including PpaSAMS1/2, PpaACS1/2, PpaACO1 together with PpaETR1/2, PpaERS1, PpaEIN4 and PpaCTR1. Decrease in the levels of FAs and PpaFADs was observed in treated fruit, except oleic acid and PpaFAD4/5, before day 5 of storage. In addition, 1-MCP-treated fruit also possessed higher levels of C6 aldehydes and alcohols and delayed the formation of volatile compounds characteristic of peach-like aroma by upregulation of PpaLOX1/2/3 and PpaHPL1 expression and down-regulation of PpaLOX5 expression. Our findings suggest that inhibition of peach-like volatiles and promotion of green-note volatiles by 1-MCP were associated with ethylene production and modulation of FA levels through transcriptional regulation.

Proteomic analysis during capsicum ripening reveals differential expression of ACC oxidase isoform 4 and other candidates

Capsicum (Capsicum annuum L.) is categorised as a non-climacteric fruit that exhibits limited ethylene production during ripening and the molecular mechanisms associated with this process are poorly understood. A proteomic approach was used to identify the differentially expressed proteins during various ripening stages (Green (G), Breaker Red 1 (BR1) and Light Red (LR)) and the genes associated with their synthesis. From 2D gel electrophoresis (2DGE), seven protein spots were identified as selectively present either in G or BR1 and are involved in carbon metabolism, colour and fruit development, protein synthesis and chaperones or biosynthesis of amino acids and polyamines. One candidate of interest, 1-aminocyclopropane-1-carboxylic acid (ACC) oxidase (ACO) is known to be involved in ethylene biosynthesis and was only present in BR1 and is related to the tomato ACO isoform 4 (LeACO4) and hence named CaACO4. CaACO4 RNA expression as well as total ACO protein expression in multiple stages of ripening (G, Breaker (B), BR1, Breaker Red 2 (BR2), LR and Deep Red (DR)) corresponded to the 2DGE protein spot abundance in breaker stages. Our findings highlight the involvement of the ethylene pathway in non-climacteric fruit ripening.

Physicochemical and microbial quality of stored green slender pepper treated with different washing solutions and packaging films

The effects of different washing solutions and packaging films on textural, biochemical and microbial quality of green slender peppers (Capsicum annuum L.) were evaluated. Fresh pepper samples were packaged either in 35 µm polypropylene or polyethylene bag without washing or after washing in tap water (TW), 100-ppm chlorine solution, 0.5% calcinated calcium solution followed by 25% ethanol rinsing (CC+E) and 1% citric acid solution followed by 50% ethanol spray (CA+E) and then stored at 10  for 4 weeks. Significant differences were found in gas composition between the two packaging films. Changes in skin puncture force, hue angle, soluble solid content, titratable acidity and pH were statistically insignificant. Chlorophyll a, chlorophyll b and total chlorophyll content declined significantly (P < 0.05) in all treatments during storage. Significant reduction (P < 0.05) in aerobic plate count was found in all washing treatments compared to unwashed sample except in TW. Yeast and mold count of chlorine and CC+E-treated samples were lower than other treatments. Samples of these two treatments also received marketable limit of visual quality scores until 4 weeks of storage in polypropylene film. Results suggest that CC+E could be a potential sanitizer and alternative to chlorine washing and polypropylene film would provide a little better advantage than polyethylene for green slender pepper.

Effects of 1-methylcyclopropene and modified atmosphere packaging on the antioxidant capacity in pepper "Kulai" during low-temperature storage

The objective of the present study was to simultaneously evaluate the effect of a postharvest treatment on the pepper's antioxidant content and its ability to retain its economical value during the postharvest period. The fruits were pretreated by modified atmosphere packaging (MAP) with or without treatment with 1-methylcyclopropene (1-MCP) before cold storage at 10°C. Changes in the levels of non-enzymatic antioxidants, including the total phenolic, ascorbic acid levels and the total glutathione level, as well as enzymatic antioxidants, including ascorbate peroxidase (APX), glutathione reductase (GR), and catalase (CAT), were determined. Both treatments successfully extended the shelf life of the fruit for up to 25 days, and a high level of antioxidant capacity was maintained throughout the storage period. However, 1-MCP treatment maintained the high antioxidant capacity for a longer period of time. The 1-MCP-treated peppers maintained high levels of phenolic content, a high reduced glutathione (GSH)/oxidised glutathione (GSSG) ratio, decreased levels of ascorbic acid and CAT activity, and increased levels of APX and GR compared with the peppers that were not treated with 1-MCP. The overall results suggested that a combination of 1-MCP and MAP was the most effective treatment for extending shelf life while retaining the nutritional benefits.