Strawberry juice, acid concentrations 360

Chlorogenic acid enhanced the colors of strawberry and chokeberry juices in concentrations higher than those of the anthocyanins present. However, the effects on purified pigments were lower, indicating the presence of other stabilizing compounds in the juices. ... 

The first step in this investigation was to isolate the pigment from strawberry juice by the method described by Sondheimer and Kertesz (11). This method involved the saturation of the juice with salt and extraction with 1-butanol, then concentration of the butanol extract under vacuum and in a nitrogen atmosphere. The anthocyanin concentrate was then taken up with hydrochloric acid in anhydrous methanol, precipitated with ether, dissolved in 0.01% hydrochloric acid, and saturated with picric acid. The anthocyanin picrate crystallized out of this solution upon storage at 0° C. as lustrous reddish bronze prisms which were further purified by recrystallization. 

The ascorbic acid content of the frozen concentrated juice was very low—less than 1 mg. per 100 grams as determined by potentiometric titration. Normal ascorbic acid content of fresh strawberries is about 50 to 100 mg. per 100 grams (3). Ascorbic acid may have been lost during the freezing and thawing operations involved in the concentration procedure. 

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