The oxidative stability and lipid modifications of Doogh prepared with Lactobacillus plantarum LS5 and control Doogh were compared during storage for 22 days. In vitro scavenging activity against 2,2-diphenyl-1-picrylhydrazyl (DPPH) free radicals showed that L. plantarum LS5 had radical scavenging activities (49.6%). Peroxide value, conjugated diene value and anisidine value measurements in Doogh lipid samples in combination with Fourier transform infrared spectroscopy demonstrated that Doogh prepared with L. plantarum LS5 was more stable than the control against formation of primary and secondary oxidation products. Furthermore, higher concentrations of short-chain fatty acids (butyric and caproic) and unsaturated fatty acids were found in Doogh treated with L. plantarum LS5. Changes in the thermograms of all samples were also observed. Results of differential scanning calorimetry indicated that melting points of lipids from treated Doogh were lower than for the control. It was concluded that L. plantarum LS5 could be used as a natural preservative in functional dairy products and could beneficially affect the consumer by providing dietary sources of antioxidants.

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