Effects of industrial tomato paste processing on ascorbic acid, flavonoids and carotenoids and their stability over one-year storage

BACKGROUND: The effects of industrial tomato paste processing and long-term (12 months) ambient storage on the content and stability of quercetin, kaempferol, ascorbic acid (AA), dehydroascorbic acid (DHAA), beta-carotene and lycopene were evaluated in a commercially produced tomato paste. RESULTS: The initial thermal treatment (hot break; 93. C for 5min) resulted in significant reductions in quercetin (54%), kaempferol (61%), AA (63%) and beta-carotene (30%), whereas subsequent processing steps (e. g. evaporation and sterilization) did not result in marked changes in these compounds. Lycopene was stable during hot break but decreased by 20% through evaporation and sterilization. The ratio of DHAA: vitamin C increased during hot break to 23%, whereas the ratio of DHAA: vitamin C remained relatively low in subsequent processing steps, indicating that AA was not oxidized. AA decreased with prolonged storage, with only 13% remaining at 12 months. The carotenoids and quercetin remained stable through 12 months of ambient storage. CONCLUSIONS: Tomato pomace contained significant amounts of carotenoids and flavonoids, indicating that it may be an underutilized processing byproduct. (C) 2011 Society of Chemical Industry