Protection of dehydrated chicken meat by natural antioxidants as evaluated by electron spin resonance spectrometry

Dehydrated chicken meat (a(w) = 0.20-0.35) made from mechanically deboned chicken necks can be protected against oxidative deterioration during storage by rosemary extract (at a sensory acceptable level of 1000 ppm, incorporated prior to drying). The efficiency of the rosemary extract was similar to that obtained by synthetic antioxidants in a reference product (70 ppm butylated hydroxyanisole and 70 ppm octyl gallate). Tea extract and coffee extract were less efficient than rosemary and synthetic antioxidants. Among the natural antioxidants tested, grape skin extract provided the least protection against oxidative changes in dehydrated chicken meat. Radicals in the product, quantified by direct measurement by electron spin resonance (ESR) spectrometry, developed similarly to headspace ethane, pentane, and hexanal, and to oxygen depletion both in unprotected and protected products. The ESR signal intensity and headspace hexanal both correlated with the sensory descriptor "rancidity" as evaluated by a trained sensory panel. Hexanal, as a secondary lipid oxidation product, showed an exponential dependence on the level of radicals in the product in agreement with a chain reaction mechanism for autoxidation, and direct ESR measurement may be used in quality control of dehydrated food products.