MAKASSAR, Indonesia May 31 2026 /Postharvest Metabo-Engineering/–Apples are among the most popular fruits in the world because of their sweet taste, refreshing texture, and nutritional value. However, not all apples remain perfectly healthy during ripening and storage. One common physiological disorder found in apples is called watercore, a condition where the flesh becomes translucent and water-soaked. Although some consumers associate watercore with extra sweetness, scientists have discovered that this condition involves complex biochemical changes inside the fruit.
According to the scientific article “Alteration of the Phenylpropanoid Pathway by Watercore Disorder in Apple (Malus × domestica)” published in the journal Scientia Horticulturae by Elsevier on 31 July 2021, watercore significantly alters the phenylpropanoid pathway in apples. The study explained that watercore affects the accumulation of important phenolic compounds, antioxidant activity, stress-response genes, and sugar metabolism within apple tissues. These findings help researchers better understand how apples respond to physiological stress and how fruit quality changes during storage and ripening.
Watercore usually appears when apples accumulate excessive sorbitol, a natural sugar alcohol found in apples. As sorbitol builds up inside the fruit, air spaces between cells become filled with liquid, causing the flesh to appear glassy or transparent. Researchers found that this condition not only changes the fruit’s appearance but also influences important metabolic pathways linked to antioxidants and plant defense systems.
One of the most interesting findings from the study was the alteration of phenolic compounds in apples affected by watercore. Phenolic compounds are natural antioxidants that help protect plant cells from oxidative stress. The researchers discovered that compounds such as hydroxycinnamic acids, flavonols, and dihydrochalcones changed significantly in watercore tissues. In some parts of the fruit, antioxidant compounds increased as part of the apple’s defense response against stress.
The study also showed that healthy tissues surrounding watercore-affected areas had higher expression of genes related to flavonoid production. This suggests that apples actively try to protect themselves from cellular damage. Scientists believe this defense mechanism is triggered by oxidative stress caused by the disorder. Interestingly, some compounds like phloridzin and chlorogenic acid accumulated differently depending on whether the tissue was healthy or affected by watercore.
Another important discovery involved polyphenol oxidase (PPO), an enzyme associated with browning reactions in fruits. Apples with watercore showed higher PPO activity, which may explain why damaged fruit tissues are more vulnerable to browning during storage. Increased oxidative stress can damage cell membranes, allowing phenolic compounds to interact with oxidative enzymes and produce undesirable color changes.
Understanding watercore is important not only for fruit scientists but also for farmers and the food industry. Apples with severe watercore may have shorter storage life and reduced market quality. By studying the molecular and biochemical mechanisms behind this disorder, researchers can help develop better storage methods, improve apple grading systems, and support breeding programs for more resistant apple varieties.
This research is strongly connected to SDG 12: Responsible Consumption and Production because understanding fruit disorders can reduce postharvest losses and improve food quality management. Better storage technology and early detection systems may help reduce food waste in the apple supply chain while ensuring consumers receive higher-quality fruit products.
In the future, combining plant physiology, molecular biology, and food science may allow scientists to predict watercore development before visible symptoms appear. Such innovations could help farmers produce healthier apples, reduce economic losses, and create more sustainable fruit production systems worldwide.
Reference:
DOI: https://doi.org/10.1016/j.scienta.2021.110438
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