Effect of thermal and high pressure processing on antioxidant activity and instrumental colour of tomato and carrot purees

Total antioxidant activity, levels of bio-active compound groups and instrumental colour of tomato and carrot puree subjected to high pressure treatment (400-600 MPa/15 min/20 degrees C) and thermal treatments (70 degrees C/2 min) were measured. Antioxidant activity in tomato and carrot puree was significantly higher (p<0.05) than in untreated or thermally processed samples. High pressure treatments at 600 MPa retained more than 90% of ascorbic acid as compared to thermal processing in tomato purees. Heat treatments caused a rapid decrease in ascorbic acid (p<0.05). Phenolic contents were in general un-affected by thermal or high pressure treatments. Colour parameters were significantly affected (p<0.05) by thermal and high pressure processing. Principal component analysis (PCA) revealed that the first two components represented 97% and 92% of the total variability in instrumental colour parameters with respect to processing for tomatoes and carrots respectively. Industrial relevance: This research paper provides scientific evidence of the potential benefits of high pressure processing in comparison to thermal treatments in retaining important bioactive compounds. Antioxidant activity (ARP), ascorbic acid, and carotenoids after exposure to high pressure treatments (400-600 MPa) were well retained. Our results also show that redness and colour intensity of purees were better preserved by high pressure processing than conventional thermal treatment. It would appear from a nutritional prospective, high pressure processing is an excellent food processing technology which has the potential to retain compounds with health properties in foods. Therefore high pressure processed foods could be sold at a premium over their thermally processed counterparts as they will have retained their fresh-like properties. (C) 2008 Elsevier Ltd. All rights reserved.