Gamma radiation maintains the firmness of refrigerated blueberries

Blueberries (Vaccinium corymbosum, Ericaceae Family) contain abundant nutrients and nutraceuticals, making them highly valued by consumers. However, these fruits have thin skin and are juicy, leading to water loss and easy softening after harvest, making them susceptible to microbial invasion.

Irradiation as a Physical Treatment

The effect of irradiation can achieve sterilization, preservation, and extension of the storage period without affecting nutrition and flavor. Therefore, it has been widely used for many fruits and vegetables.

Previous studies have shown that irradiation doses ranging from 1.0 to 2.5 kGy activate the fruit's defense system, inhibit respiration and reactive oxygen metabolism, effectively stabilize the cell wall structure, and consequently delay the softening of refrigerated blueberries.

Improvement of Firmness through Intracellular Ca2+ Migration to the Cell Wall

Firmness, as a crucial fruit trait, is closely related to the composition and structure of the cell wall. Calcium ion (Ca2+), a necessary mineral element in plants, serves as a signal transduction messenger, regulating physiological and biochemical responses of cells. Additionally, Ca2+ is a significant component of cell walls contributing to maintaining their structure and firmness.

When fruits are exposed to external stimuli such as radiation, the Ca2+ balance in plant cell organelles is disrupted, releasing Ca2+ to form complexes (chelates) with pectin macromolecules through electrostatic interaction. This directly participates in modifying cell walls, thereby enhancing fruit firmness.

In a recent study, blueberry fruits were irradiated with gamma rays at doses of 0.5, 1.0, and 2.5 kGy. It was observed that irradiation at 2.5 kGy promotes the migration of intracellular Ca2+ to the cell wall, exerting a positive effect on the firmness of refrigerated fruits.

*Gray (represented by Gy) is a unit in the International System of Units (SI) representing the amount of ionizing radiation energy absorbed (or dose) per unit mass, i.e., one joule of radiation absorbed per kilogram of matter (J/kg).

Sources

Wang, C.; Tao, Y.; Han, Y.; Zhang, R.; Li, L.; Gao, Y. (2023). Influences of subcellular Ca redistribution induced by γ irradiation on the fruit firmness of refrigerated blueberries. Postharvest Biology and Technology, 195:112146.

Image

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