Effects of various factotrs on the oxidative stability of ω-3 fatty acid-enriched Doogh (Iranian yoghurt drink)

Milk and dairy products are generally recognized as healthful foodstuffs. Their negligible content of polyunsaturated fatty acids (PUFAs) has prompted investigators to consider fortifying them with long chain PUFAs، but the main challenge is the high susceptibility of PUFAs to oxidation and rancidity. Therefore، in the present study the possibility of using long chain PUFAs to fortify Doogh (a traditional Iranian yoghurt-based beverage)، as a functional dairy product، as well as the effect of different factors on the physical stability and peroxide value of the fortified Doogh during storage، were determined. ω-3-Fatty acid-fortified Doogh was prepared using yogurt، water، salt، the soluble phase of gum tragacanth، and crude rapeseed، soy bean، and fish oil. The fortified Dooghs (a mixture of oil and yoghurt or of Doogh and oil) were homogenised using ultrasound at different amplitudes and durations in order to find the optimum processing conditions (amplitudes and duration). Moreover، effects of several factors (heat treatment، storage temperature، intensity and duration of sonication، and oil content) on the physical stability and peroxide value of the fortified Dooghs during storage (35 days) at 2 temperatures (5 and 22˚C) were determined. The findings showed that the preparation method of fortified Doogh had significant effects on its homogenization extent and physical stability. Furthermore، during storage the peroxide value of the samples increased، particularly at the higher temperatures، while they were quite stable physically. It may be concluded that ultrasound treatment can homogenize and stabilize ω-3-fatty acid-fortified Doogh، with no undesirable effect on peroxide value during storage at refrigeration temperatures.