Inhibition of oxidative rancidity in frozen cooked fish flakes by tert‐butylhydroquinone and rosemary extract

The antioxidant properties of tert ‐butylhydroquinone (0·5 g kg −1 + 20 g kg −1 ascorbic acid—TBHQ‐AS) and an extract of rosemary (2·5 g kg −1 ) alone and in combination were determined by their addition as solutions to cooked fish flakes stored at ‐ 20°C. Oxidation was measured by following changes in free fatty acids, thiobarbituric acid number, fatty acid composition and sensory evaluation. The order of effectiveness in inhibiting oxidation was TBHQ‐AS > combination > rosemary > untreated control −70°C > untreated control ‐20°C. Sensory evaluation indicated that green aroma and flavor notes were associated with the rosemary extract, while fish oil notes were associated with untreated samples.