Effect of dietary olive leaves and rosemary on microbial growth and lipid oxidation of turkey breast during refrigerated storage
Forty turkeys were allocated to five groups of eight birds each. One (control) was fed a basal diet while the others were fed diets supplemented with either olive leaves at 10 g/kg, rosemary at 10 g/kg, alpha-tocopheryl acetate at 150 or at 300 mg/kg feed. Following slaughter, fillets from the breasts of the birds were stored at 4 degrees C in the dark for 12 days and their lipid oxidation and microbial growth rate were monitored. Results showed that dietary olive leaves were more effective in inhibiting lipid oxidation of the breast fillets compared to rosemary, but inferior to the dietary supplementation of 300 mg alpha-tocopheryl acetate/kg. In turn, lipid oxidation was more effectively inhibited when the birds received alpha-tocopheryl acetate supplementation at 150 mg/kg compared to when the birds received no suppelementation, but inferior to rosemary supplementation. Total viable counts, lactic acid bacteria, Enterobacteriaceae and psychrotrophic bacterial counts were all increased in breast fillets of all groups throughout refrigerated storage. Diet supplementation with a basal level of alpha-tocopheryl acetate had no effect on the bacterial counts recorded in the control group, but diet supplementation with olive leaves or rosemary resulted in a decrease in all bacterial counts from day 2 of storage and thereafter. During this period olive leaves were more effective in inhibiting bacterial growth than rosemary.