Low-temperature storage is a fundamental practice for extending the shelf life of sweet cherries.
Fruits that are notoriously delicate and characterized by high postharvest metabolic activity.
However, alongside the well-known benefits of cold storage in slowing down respiratory and senescence processes, there are also less evident but potentially critical side effects for commercial quality, including flesh lignification.
A recent study investigated this phenomenon in the sweet cherry cultivar ‘Meizao’, showing how low-temperature storage induces structural, biochemical, and molecular modifications that lead to increased fruit firmness during storage.
The results show that storage at 2 °C causes a progressive increase in fruit firmness, in clear contrast to what is observed at room temperature, where firmness rapidly declines.
This increase in firmness is accompanied by a significant accumulation of lignin in the flesh, confirmed both by spectrophotometric analyses and by specific histological staining.
Which highlight a progressive deposition of lignin in the cell walls as cold storage proceeds.
Observations by electron microscopy further support these findings, revealing a marked thickening of cell walls in fruit stored at low temperature, consistent with a process of secondary lignification.
From a biochemical perspective, cold storage selectively stimulates the activity of key enzymes involved in lignin biosynthesis, particularly CAD, POD, and LAC.
Which are responsible for the final steps of monolignol synthesis and polymerization.
This suggests that the increased firmness is not merely the result of reduced cell wall degradation, but rather derives from an active structural reorganization induced by cold stress.
Indeed, transcriptomic analyses enabled the identification of 27 candidate genes involved in this process, many of which show a strong positive correlation with increased lignin content and fruit firmness.
Together with altered expression under low-temperature storage conditions.
Overall, the results indicate that low temperature acts as a true stress factor capable of activating a structural defense mechanism in the fruit, with direct effects on texture.
From an applied perspective, this study provides valuable information for the postharvest management of sweet cherries, particularly for the cultivar ‘Meizao’.
While cold storage remains an essential tool for preserving freshness, nutritional components, and aromatic profile, prolonged storage may induce firmness increases associated with lignification.
Potentially leading to negative effects on consumer acceptability.
Knowledge and understanding of the physiological and molecular mechanisms underlying this process provide a foundation for the development of more targeted storage strategies.
Such as optimizing storage temperatures and duration or applying complementary treatments capable of limiting the activation of lignification.
In conclusion, the management of storage temperatures, and cold conditions in general, in the postharvest handling of sweet cherries cannot be considered solely in terms of metabolic slowdown.
But must also take into account the structural modifications induced in the fruit, with the aim of improving quality control along the supply chain.
Source: Jiao, Y., Zhu, X., Tian, C., Shi, X., Gong, H., Sun, S., Li, J., & Zhang, A. (2026). Low temperature induces lignification in sweet cherry by modulating lignin synthesis-related genes. Postharvest Biology and Technology, 231, 113944. https://doi.org/10.1016/j.postharvbio.2025.113944
Image source: Stefano Lugli
Andrea Giovannini
PhD in Agricultural, Environmental and Food Science and Technology - Arboriculture and Fruitculture, University of Bologna, IT
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