Increasing diversity of marketable raspberries
Scientists compared the postharvest quality of red, yellow, purple, and black raspberries. They discovered significant correlations between raspberry decay rate and physiochemical properties. There were no correlations among changes in color, firmness, decay, or juice leakage rates. Yellow raspberries had the worst decay rates but the best leakage rates. Black and purple raspberries, with the highest phenolics and anthocyanins and the lowest ethylene evolution rates, resisted decay the longest but bled soonest.
Raspberries are the third most popular berry in the United States. Their popularity is growing as a specialty crop for the wholesale industry and in smaller, local markets, and U-pick operations. As consumer interest in the health benefits of colorful foods increases, small growers are capitalizing on novelty fruit and vegetable crops such as different-colored raspberries. Authors of a newly published study say that increasing the diversity of raspberry colors in the market will benefit both consumers and producers. “Producers will need to know how fruit of the other color groups compare with red raspberries with regard to the many postharvest qualities,” noted the University of Maryland’s Julia Harshman, corresponding author of the study published in HortScience (March 2014).Raspberries have an extremely short shelf life, which can be worsened by postharvest decay. Postharvest susceptibility to gray mold (Botrytis cinerea) drastically reduces the shelf life of this delicate fruit. “The main goal of our research was to compare the postharvest quality of different-colored raspberries that were harvested from floricanes under direct-market conditions with minimal pesticide inputs,” Harshman said. The researchers said that, although there is abundant information in the literature regarding red raspberry production in regard to gray mold, very little research has been conducted on postharvest physiology of black, yellow, or purple raspberries.The researchers analyzed 17 varieties of raspberries at the USDA’s Agricultural Research Center in Beltsville, Maryland, examining each cultivar for characteristics such as anthocyanins, soluble solids, titratable acids, pH, color, firmness, decay and juice leakage rates, ethylene evolution, and respiration.”In comparing the four commonly grown colors of raspberry, we drew several important conclusions,” they said. “The mechanisms controlling decay and juice leakage are distinct and mediated by both biotic and abiotic factors. The colors that performed well for one area are opposite the ones that did well in the other.” For example, firmness was expected to track closely with either leakage or decay resistance; however, the analyses did not indicate this.Red raspberries, in comparison with the other three colors analyzed during the study, had the highest titratable acids (TA) and the lowest ratio of soluble solids to TA, which, the authors say, accounts for the tart raspberry flavor consumers expect.Yellow raspberries had the lowest levels of anthocyanins and phenolics. …
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