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Keywords:

  • natural colours;
  • UHT;
  • red radish;
  • black carrot;
  • colour stability

Abstract

BACKGROUND

The aim of this experiment was to select a pool of potential red/pink natural colour candidates and evaluate their stability during ultrahigh-temperature (UHT) processing and subsequent storage and to compare their behaviour against the artificial colour erythrosine. It was hypothesised that heat processing and post-treatment storage conditions would have a negative effect on the stability of the natural colourants.

RESULTS

All colourants except fermented red rice showed significant colour loss post-UHT processing (α = 0.05). Analysis of the colour parameters L*, a* and b* determined that lycopene was the least stable of the colourants and red radish the most stable under all conditions. Fermented red rice was observed to be heat-stable after exposure to UHT processing and also remained relatively stable during storage, as was black carrot. The variation across trials and the spoilage of some samples were attributed to the fluctuations in temperature (±5 °C) observed during processing.

CONCLUSION

Heat processing and post-treatment storage conditions had a negative effect on the stability of the natural colourants. © 2012 Society of Chemical Industry