Comparison of monomeric anthocyanins and colour stability of fresh, concentrate and freeze-dried encapsulated cherry juice stored at 38 degrees C

BACKGROUND: Anthocyanins are natural colorants and bioactive compounds widely distributed among vegetables and fruits. Unfortunately, in fruit juices stored at room temperature monomeric anthocyanins easily convert to colourless compounds and subsequently to insoluble brown pigments. OBJECTIVE: The object of present study is to compare the stability of monomeric anthocyanins and colour changes during storage temperature at 38 degrees C of pasteurized cherry juice, concentrate and freeze-dried juice. METHODS: Colour changes of, pasteurized cherry juice (18.7 degrees Brix), concentrate (61 degrees Brix) and juice freeze-dried with addition of maltodextrin and arabic gum as encapsulating agents, were evaluated by CIELab parameters, a*, b* and, L*. Anthocyanins content was measured by pH-differential method and total phenolics were determined by Folin-Ciocalteu method. The glass transition temperature (T-g) of the freeze-dried matrix was determined. RESULTS: It was found the stability of monomeric anthocyanins and colour retention during storage at 38 degrees C was significantly superior in the freeze-dried encapsulated juice powder than in liquid cherry juices. CONCLUSIONS: This is attributed to the protective encapsulation of the anthocyanins in the amorphous matrix of maltodextrin/arabic gum of reduced water activity.