Effect of radiation and other processing methods on protein quality of sunflower meal

The effects of gamma irradiation from a Co-60 source (10 and 20kGy), dry heating (121 degrees C for 10, 20 and 30min), autoclaving (121 degrees C at 103.5kPa for 10, 20 and 30min) and their combination on chlorogenic acid, soluble protein, available lysine and in-vitro protein digestibility of sunflower meal were studied. The moisture content of the raw sample was 78gkg(-1) as is and on a dry matter basis. The meal contained 26.7 gkg(-1) chlorogenic acid, 330 gkg(-1) crude protein, 78.5% soluble protein and 2.63 g 16 g N-1 available lysine. Digestibility of raw meal was 81.5%. Chlorogenic acid, soluble protein and available lysine of raw meal decreased during dry heating, autoclaving and radiation processing. The digestibility was significantly affected by processing method (P < 0.05), as well as by the time of dry heating and autoclaving. The influence of combination methods revealed that irradiation alone had a little effect on chlorogenic acid and in-vitro protein digestibility. Autoclaving plus irradiation up to 20kGy markedly improved the digestibility (90%). Therefore, the results suggested that the combination of autoclaving for 10 min plus irradiation up to 20kGy has a beneficial effect on the protein quality of sunflower meal with little effect on its content of soluble protein, available lysine and markedly reduced chlorogenic acid by 87%, more than other processing methods. (C) 1999 Society of Chemical Industry.