Why do some blueberries sink and some float

The fluctuation of blueberries in water is mainly related to fruit maturity, internal structure, and sugar content. Mature blueberries are prone to sinking due to increased sugar accumulation density, while immature fruits are prone to floating due to more air gaps.

The cell wall of mature blueberries gradually softens, and the flesh tissue becomes tight. If the concentration of sugar and glucose increases, the overall density will exceed that of water. These types of fruits usually appear dark blue in color, with intact wax layers on the skin, and quickly sink when placed in water. At the same time, during the ripening process, antioxidant components such as anthocyanins increase, further increasing the substantial weight of the fruit. There are many air gaps inside unripe blueberries, and the flesh structure is loose with a density lower than water. This type of fruit has a reddish or light purple color, strong skin reflection, and high buoyancy. After harvesting, some fruits with high immaturity may continue to consume sugar due to respiration, resulting in a decrease in density. This phenomenon is more pronounced in blueberries transported in the cold chain.

When selecting blueberries, the phenomenon of sinking and floating can be combined to assist in judgment, but attention should be paid to variety differences. Some high sugar varieties may sink even if they are not fully mature. It is recommended to refrigerate and avoid squeezing. Before consumption, gently rinse with running water. People with diarrhea should control their single intake to no more than 20 pills. The buoyancy test can be used as one of the reference indicators for freshness, and the actual quality also needs to be comprehensively observed in terms of color, aroma, and stem condition.