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The anthocyanins in mulberries appear to degrade during storage at increasing temperatures.
Like other deeply pigmented berries, mulberries are rich in anthocyanins. Despite the health benefits associated with anthocyanin intake, these coloring compounds are unfortunately regarded as being highly unstable. Supporting research, however, is not based on mulberries but on other fruits. Is the case of anthocyanin stability the same for the anthocyanins in mulberries?
It appears so. Researchers in Kazakhstan and Turkey recently performed tests on black mulberry juice and concentrate in hopes of observing potential changes that occur when these products are stored long-term and under increasing temperatures. After eight months of storage at 5°, 20°, 30°, 40°C, they say chemical changes were quite evident.
As temperature increased, anthocyanin content decreased as much as 75% in juice and 98% in concentrate. Anthocyanins do have antioxidant potential, so antioxidant activity (measured by ORAC values) understandably decreased, as well. ORAC values dropped as much as 16% in juice and 34% in concentrate. A final marker used by the researchers was hydroxymethylfurfural (HMC). It’s formation is associated with flavor and color degradation in some food products, and it saw significant increases at all temperatures except for 5°C.
“As increased temperature and storage time has an important affect on the degradation of black mulberry anthocyanin content, mulberry concentrates and fruit juices should be kept lower than 5°C,” said the researchers. Knowing that value should be useful for manufacturers of drinks, marmalades, and other products that can be made from black mulberries.
Nutritional Outlook magazine