Anthocyanin and colour degradation in ozone treated blackberry juice

Response surface methodology (RSM) was used to investigate the effects of ozone concentration (%w/w) and treatment time (min) on the anthocyanin content and colour of fresh blackberry juice. RSM methodology based on a two factor five level central composite design was employed with control variables of ozone concentration (0 to 7.8%w/w) and treatment time (0 to 10 min) at a constant gas flow rate. Predicted models were found to be significant (p<0.001) with regression coefficients (R-2) of 0.89, 0.82. 0.95, 0.86 and 0.97 for L, a, b, TCD and anthocyanin content respectively. Ozone concentration and treatment time were found to be critical factors influencing both anthocyanin and colour degradation. This study demonstrated that response surface methodology can be employed to model colour and anthocyanin degradation of ozonated blackberry juice while minimising the number of experiments required. Industrial relevance: In the United States (US) legislation requires fruit juice processors to achieve a 5-log reduction in the numbers of the most resistant pathogens in their finished products. Consequently a number of commercial fruit juice processors in the US started to employ ozone for fruit juice pasteurisation. Ozonation was approved by the FDA in 2001 as a direct additive to food. The FDA issued industry guidelines for fruit juice processing with ozone [FDA, (2004). FDA Guidance to Industry, 2004: Recommendations to Processors of Apple juice or Cider on the Use of Ozone for Pathogen Reduction Purposes. Available online http://www.cfsan.fda.gov/-dms/juicgu13.html.], however this report concludes that these guidelines are based upon limited scientific data. This paper investigates the effect of ozone processing on the anthocyanin content and colour of blackberry juice. The results presented demonstrate that the effect of ozonation on the nutritional properties of blackberry juice or juice products containing blackberry should be considered by processors prior to its adoption as a preservation technique. (C) 2008 Elsevier Ltd. All rights reserved.