Exogenous Melatonin Reduces Lignification and Retains Quality of Green Asparagus (Asparagus officinalis L.).

Athip Boonsiriwit,Pontree Itkor,Myungho Lee,Youn Suk Lee,Minhwi Kim

doi:10.3390/foods10092111

Athip Boonsiriwit, Pontree Itkor + Show 3 more

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https://doi.org/10.3390/foods10092111

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Abstract

Asparagus (Asparagus officinalis L.) is highly perishable because of its high respiration rate, which continues after harvesting and leads to weight loss, increased hardness, color change, and limited shelf life. Melatonin is an indoleamine that plays an important role in abiotic stress. This study was designed to investigate the effects of melatonin on the quality attributes of green asparagus during cold storage. Green asparagus was soaked in a melatonin solution (50, 100, and 200 μM) for 30 min and then stored at 4 °C under 90% relative humidity for 25 days. The results indicated that melatonin treatment delayed the post-harvest senescence of asparagus and maintained high chlorophyll and vitamin C levels. Melatonin treatment hindered phenylalanine ammonia-lyase and peroxidase activities and reduced lignin content, thereby delaying the increase in firmness. Moreover, melatonin treatment enhanced catalase and superoxide dismutase activities, leading to reduced hydrogen peroxide content. These results indicate that melatonin treatment can be used to maintain the post-harvest quality and prolong the shelf life of green asparagus.

Highlights

The unique taste and texture of asparagus (Asparagus officinalis L.) have made it a popular vegetable, recognized as a rich source of nutrients and bioactive compounds with therapeutic properties, such as weight control, anti-oxidation, anticancer, radioprotection, and blood pressure control [1,2]
All the melatonin-treated asparagus spears presented with significantly decreased weight loss compared with the control from day 15 until the end of the storage period
At the end of the storage period, the control group weight loss amounted to 9.06 ± 0.41% whereas that of 0.5 MLT, 1.0 MLT, and 2.0 MLT amounted to 6.83 ± 0.59, 5.66 ± 0.19, and 6.01 ± 0.49%, respectively

Summary

Introduction

The unique taste and texture of asparagus (Asparagus officinalis L.) have made it a popular vegetable, recognized as a rich source of nutrients and bioactive compounds with therapeutic properties, such as weight control, anti-oxidation, anticancer, radioprotection, and blood pressure control [1,2]. Fresh asparagus has a short shelf life and a high metabolic rate and, a high post-harvest respiratory activity; this leads to weight loss, increased hardness [3,4], rapid nutrient and bioactive compound loss [4], and chlorophyll degradation [5] during storage. Texture is an important freshness indicator of asparagus spears and is related to their freshness. The firmness of asparagus increases being a general behavior of asparagus, followed by wrinkling, toughening, and hardening of the spears due to lignification [6]. Lignification is attributed to secondary cell wall formation following the upregulation of cellulose, hemicellulose, and lignin biosynthesis-related activities of enzymes such as phenylalanine ammonia-lyase (PAL) and peroxidase (POD) [6,7]. Various approaches to improving asparagus quality and extending its shelf life have been investigated, including cultivar development [8–11], agronomic management [10], post-harvest treatment [1,12–14], and improved packaging technology [3,15]

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