Effects of irradiation and storage on the physico‐chemical and sensory properties of hamburgers enriched with lycopene

Summary In order to increase their safety and shelf‐life, raw hamburgers containing 30, 45 and 60 g kg−1 dry tomato peel (DTP) as a source of lycopene were manufactured, vacuum‐packed and irradiated with 2 or 4 kGy. The effects of this treatment on microbial load, lycopene concentration, physico‐chemical and sensory properties were studied during 17 days of refrigerated storage. After irradiation with 4 kGy and 17 days of storage, microbial levels fell, four logarithmic cycles and the lycopene concentration fell to 15% of the initial value. Even with this decrease, hamburgers containing 6% DTP had a final lycopene concentration of 7.14 mg per 100 g of hamburger, an amount very close to the recommended daily intake for a healthy diet. DTP masks the brownish colour characteristic of irradiated meat, and 6% DTP gives to the hamburger similar redness (a* parameter), independently of the dose of radiation applied. Sensory characteristics were influenced by irradiation, but the higher lycopene concentration (6 g kg−1) masked these changes sufficiently to assure an acceptable colour and odour in the final product after the storage period.