The Effect of Chemical Treatments and Heat on Color Stability of Frozen Machine-harvested Strawberries for Jam1

A study was conducted on 2 cultivars of mechanically harvested strawberries (Fragaria × ananassa Duch.) to determine the effects of chemical treatments and heat on stability of color in frozen fruit for jam. Treatment with NaHSO3, citric acid or SnCl2 improved color of the jam when compared to the control, as demonstrated by Color Difference Meter (CDM) values and sensory ratings. The CDM color functions were higher on jam made from frozen puree than from frozen whole fruit, yet panel scores were significantly higher on jam from whole fruit. The jam made from frozen puree browned more during storage than that made from whole fruit. There were significant differences in color between cultivars and storage temperatures, but differences among treatments were larger. Treatment with NaHSO3, citric acid or SnCl2 offer possibilities for stabilizing color in jam.