The effects of gamma irradiation from a 60 Co source (10 and 20 kGy), dry heating (121 ยฐC for 10, 20 and 30 min), autoclaving (121 ยฐC at 103.5 kPa for 10, 20 and 30 min) and their combination on chlorogenic acid, soluble protein, available lysine and in-vitro protein digestibility of sunยฏower meal were studied.
The moisture content of the raw sample was 78 g kg ร1 as is and on a dry matter basis. The meal contained 26.7 g kg ร1 chlorogenic acid, 330 g kg ร1 crude protein, 78.5% soluble protein and 2.63 g 16 g N ร1 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 signiยฎcantly affected by processing method (P `0.05), as well as by the time of dry heating and autoclaving. The inยฏuence of combination methods revealed that irradiation alone had a little effect on chlorogenic acid and in-vitro protein digestibility. Autoclaving plus irradiation up to 20 kGy markedly improved the digestibility (90%).
Therefore, the results suggested that the combination of autoclaving for 10 min plus irradiation up to 20 kGy has a beneยฎcial effect on the protein quality of sunยฏower meal with little effect on its content of soluble protein, available lysine and markedly reduced chlorogenic acid by 87%, more than other processing methods.