, Volume 224, Issue 6, pp 667-679

Colour stability of canned strawberries using black carrot and elderberry juice concentrates as natural colourants

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Abstract

Besides texture degradation and aroma loss colour fading and browning of processed fruits, in particular strawberries, displaying comparatively low amounts of non-acylated anthocyanins, still pose a serious problem. Therefore, in the present study the colour of texture-improved canned strawberries was stabilised using commercial concentrates from black carrots and elderberries as natural colourants. CIE L * a * b * values of the fruit surface and of the brine solutions were monitored over a period of 24 weeks under light exposure. Furthermore, the contents of individual anthocyanins were analysed by HPLC-DAD. The colour of the processed control fruits (without added colourant) was unacceptable even at the beginning of the storage. Their anthocyanin contents were reduced by more than 85% at the end of the storage period. In contrast, the colour of canned strawberries containing black carrot and elderberry anthocyanins was significantly improved. Colour difference values ΔE * of black carrot-coloured strawberries were found to be smaller than those of the samples containing elderberry concentrate as a colourant. This could be ascribed to the presence of acylated anthocyanins in the first exhibiting exceptional storage stability, while all non-acylated pigments were degraded. The chill brining process for fruit firming markedly affected pigment stability, which can be attributed to enzymes that are still active at cold storage conditions.