Effects of olive leaf water extracts on physical properties of chicken breast sausage

Abstract

Olive leaf (Olea europaea L.) is an underutilized resource of olive tree but has a high polyphenol content, so it has the potential to be used as a food ingredient. In this study, we investigated the effects of olive leaf water extracts on the physical properties of chicken breast sausage (CBS). Olive leaf water extracts were prepared at 4 (OEx4) and 80°C (OEx80) from dried olive leaf powder and they were applied to CBS preparation within the concentration range 0.05 to 0.5% (w/w minced meat). OEx4 had 32% lower polyphenol content than OEx80. Water content, expressible water, breaking strength, and viscoelastic properties of CBS with OEx4 and OEx80 were measured. The analyses of the sausage physical properties showed that adding 0.1% OEx4 increased the breaking stress (115%), breaking strain (68%), modulus of elasticity (20%), coefficient of viscosity (23%), and water-holding capacity (9%), and the enhancement effects of OEx4 were much greater than those of OEx80. The gel network of OEx4-containing CBSs observed by scanning electron microscopy was finer and denser than that of the control CBS. Chemical analyses of the meat proteins showed that OEx4 induces polymerization of myofibril proteins, especially myosin, via non-disulfide covalent bridges formed between amino and/ or thiol groups. These results indicate that the application of OEx4 improves the sausage gel properties by inducing non-disulfide-type protein polymerization. This study supports the feasibility of OEx4 as a new ingredient to improve the texture of gel products prepared from chicken breast minced meat.