Effects of gamma irradiation or high hydrostatic pressure on cholesterol oxidation and sensorial quality in mechanically deboned turkey meat and chicken liver

Pasteurising effect of 2 kGy radiation dose or 200 MPa hydrostatic pressure for 20 min in nonfrozen mechanically deboned turkey meat (MDM) was achieved without increase of cholesterol oxidation products (COPs) and increases of TBARs values (thiobarbituric acid-reactive substances) during 15 days of chilled storage following the treatments, while untreated samples were spoiled. In frozen MDM, 7 kGy was equivalent to 400 MPa for 20 min in respect of improved microbiological safety, however, accelerated oxidation of cholesterol and lipids as well as organoleptic changes were observed. Due to considerable increase in the amount of COPs in untreated samples during frozen storage, the same level of oxysterols in control as well as in treated samples was found after 8 months of frozen storage. Similar changes in TBARs values were observed. In experiments with non-frozen samples, addition of antioxidants, such as thyme-oil or α-tocopherol + ascorbic acid inhibited significantly the oxidative changes of cholesterol and lipids during 3 kGy or 400 MPa treatments. The pasteurising effects of 300 MPa treatments and 2 kGy, and that of oxidative changes were tested on non-frozen chicken liver. Although favourable microbiological effects were achieved, 2 kGy irradiation induced off-odour while the high- hydrostatic pressure (HHP) treatment caused considerable discolouration and a slight off-odour.