That white powder on grapes, called bloom, is a natural wax produced by the fruit itself. Bloom helps grapes retain moisture, protects them from environmental factors like UV rays and high temperatures, and influences their flavor and quality as they develop.
Bloom appears on many fruits like plums, apples, and grapes. It primarily contains oleanolic acid, a triterpenoid compound with antibacterial, anti-inflammatory, and antioxidant properties. This powdery coating also creates a physical barrier, limiting the intrusion of harmful microorganisms and the natural oxidation process.
Research published in the journal ScienceDirect suggests that oleanolic acid supports cell protection and cardiovascular health, while also helping to combat certain pathogens. Therefore, the white powder on grapes is both safe and beneficial for health.
Many consumers worry that the white powder is a sign of mold. To distinguish between the two, bloom typically covers the entire grape evenly, appearing white or slightly bluish, powdery or waxy. In contrast, mold appears in patches, with a brown or fuzzy appearance, and the affected grapes are often shriveled or wrinkled.
Research from the University of Michigan (USA) suggests that grapes should be stored in the refrigerator at a temperature between 0-4°C, in a perforated plastic bag or a container with a breathable lid to maintain humidity and prevent bacterial growth.
You shouldn't wash grapes immediately after purchase or before storage, as the moisture can damage the natural bloom, creating conditions for mold growth and causing the grapes to spoil faster.
Instead, wash grapes just before eating by gently soaking them in cool water for about 30 seconds, then drying them completely. This removes dirt, insects, or environmental impurities without significantly affecting the protective wax.
Before storing, carefully inspect the grapes and remove any damaged or bruised ones to prevent the spread of bacteria. Store grapes in a cool, dry place and avoid stacking them to prevent damage to the bloom.
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