Blueberries are a popular fruit not just because of their taste but also as a source of vitamins, minerals, organic acids, and bioactive compounds including polyphenols, flavonoids, ascorbic acid, and anthocyanins.
Unfortunately, the combination of juicy flesh and thin skin makes blueberries vulnerable to a swift decline especially when stored at ambient conditions. This deterioration includes physical damage, microbial contamination and senescence, all of which means blueberry storage is limited to six to eight days, providing a short shelf life and window for transportation.
While cold storage can slow down decline, it can bring new problems. These include chilling stress, resulting in the overproduction of reactive oxygen species and modifying their inherent metabolic responses, which disturbs the structure of membrane tissues, causing chilling injury (CI) which can manifest as surface depressions, alterations in color, wet patches, and uneven maturation, affecting the aesthetic appeal of the fruit.
But a recent study, published in SCI’s Journal of the Science of Food and Agriculture, explores how preharvest hexanal spraying can reduce CI symptoms by minimizing oxidative damage to cell membranes by enhancing the enzymatic and nonenzymatic antioxidant defense system, potentially lengthening their shelf life as a result.
The researchers noted chilling injury “increases the susceptibility of produce to postharvest degradation through the formation of water-soaked lesions, which act as entry points and favourable environments for pathogen proliferation on the product”.
Previous studies provide positive evidence of using hexanal, a chemical with ‘general recognition as safe’ by the US Food and Drug Administration, on multiple other soft fruits, such as mangoes figs and guavas. It was shown to have a positive impact on the conservation of quality in the fruits and the improvement of chilling tolerance during cold storage.
This study investigated the effectiveness of a preharvest spray containing 0.02% hexanal in reducing CI and improving the postharvest storage quality of ‘Star’ and ‘Biloxi’ blueberries.
The authors noted that “fruit treated with preharvest hexanal showed lower levels of microbial counts and incidence of decay than the control, indicating that hexanal's antimicrobial effects may indirectly protect cell structure, leading to better quality and longer storage for blueberries”.
This highlights the ability of preharvest hexanal application to blueberries to reduce the chilling injury caused by interfering with enzymatic activity and various metabolic pathways, delaying deterioration and maintaining both their aesthetic and nutritional value for longer periods of time. Much of this was in relation to the increased enzyme activity within the antioxidant defence system and preserving cell membranes by reducing oxidative damage. The treated blueberries also exhibited raised phenol, flavonoid and vitamin C levels in contrast to the control, all of which possess antioxidant properties.
The researchers said the application of preharvest hexanal resulted in a “significant reduction” in blueberry fruit's CI symptoms by minimizing oxidative damage to cell membranes by enhancing the enzymatic and nonenzymatic antioxidant defense system.
It also inhibited activities, for example, hydrolase enzyme activity and the buildup of MDA, H2O2 electrolytes, preserving membrane stability and the firmness of the fruit, all of which can help protect the fruit in storage while stalling the loss of quality.
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