Improved color and anthocyanin retention in strawberry puree by oxygen exclusion
BACKGROUND: Strawberry puree color is unstable during processing and storage due to oxidative reactions.
OBJECTIVE: To determine if strawberry puree prepared under nitrogen or carbon dioxide would result in greater retention of color and anthocyanins than samples prepared under air.
METHODS: Purees prepared under carbon dioxide, nitrogen or air were pasteurized and stored at 25°C. Samples were evaluated one day, and at two week interval for eight weeks after processing for color (L*, chroma and hue), anthocyanin content and percent polymeric color.
RESULTS: Purees prepared under carbon dioxide or nitrogen retained more anthocyanins (75% and 82%, respectively) following pasteurization than samples prepared under air (60% and 72%), respectively. The protective effect of oxygen exclusion on anthocyanin stability persisted throughout eight weeks of storage at 25°C with purees prepared under carbon dioxide or nitrogen each showing 23% retention, while purees prepared under air showed only 7% and 10% retention. Purees prepared under carbon dioxide or nitrogen also had greater color stability evident by lower L*, hue and percent polymeric color and greater chroma values than puree processed under air over storage.
CONCLUSIONS: Strict oxygen exclusion during strawberry processing appears to be a viable technology to improve anthocyanin and color stability, but additional technologies are needed to prevent anthocyanin losses that occur under anaerobic conditions during storage.