Effect of freeze-dried green tea added in hamburgers as source of antioxidant during freezing storage

Practical applications The objective of this study was to investigate the antioxidant potential of freeze-dried green tea (GT) in hamburgers (lipid oxidation) and its influence on quality characteristics (composition, colour, texture, pH, microorganisms and sensory acceptance). The total polyphenol (TPC), flavonoid content (FC) and antioxidant activity of GT were also evaluated. Five treatments were used: control-without antioxidant; butylhydroxytoluene (BHT)-with 0.01% of BHT; and with different levels of GT (0.01%, 0.02% and 0.04%). The TPC in GT was 44.31 mg gallic acid equivalent (GAE)/g, FC was 4.43 mg quercetin equivalent (QE)/g and also presented a higher antioxidant activity. The GT addition did not influence (p > 0.05) on moisture, protein, lipid, ashes, calories, microorganism counts and shear force of hamburger. Only the b* value (colour) was affected (p < 0.047). GT was more efficient in retarding the hamburger oxidation than BHT (p < 0.05). No influence was also observed on sensory acceptability of hamburger, being the GT a potential substitute for synthetic antioxidant. Currently, the use of antioxidants by the industry is done on a large scale, mainly aimed at inhibiting or retarding lipid oxidation, which modify colour, flavour, texture and decrease nutritional quality of food, reducing the acceptability by consumers leading them to reject the product. However, most of these antioxidants are synthetic and many of them are harmful to human health. Thus, this work demonstrates the potential use of a natural antioxidant (green tea) as a substitute for synthetic antioxidant by the food industries.