title: Study of antioxidant activity of sheep visceral protein hydrolysate: Optimization using response surface methodology.
abstract: BACKGROUND
  The main objective of this experiment was optimal use of none edible protein source to increase nutritional value of production with high biological function, including antioxidant activity.
  
  
  METHODS
  Sheep visceral (stomach and intestine) was used as substrate. Response surface methodology (RSM) was used to optimize hydrolysis conditions for preparing protein hydrolysate from the sheep visceral, using alcalase 2.4 l enzyme. The investigated factors were temperature (43-52 °C), time (90-180 min), and enzyme/substrate ratio [60-90 Anson-unit (AU)/kg protein] to achieve maximum antioxidant activity. Experiments were designed according to the central composite design.
  
  
  RESULTS
  Each of the studied variables had a significant effect on responses (P < 0.05). Optimal conditions to achieve antioxidant activity were, temperature (48.27 °C), time (158.78), min and enzyme/substrate ratio (83.35) Anson-unit/kg protein. Under these conditions, antioxidant activity was 68.21%, R2 for model was 0.983. The values indicated the high accuracy of the model to predict the reaction conditions considering different variables. The chemical analysis of protein hydrolysate showed high protein content (83.78%) and low fat content (0.34%).
  
  
  CONCLUSIONS
  Our results showed that protein hydrolysate of sheep visceral, can be used as a natural antioxidant with high nutritional value.
authors.affiliation: Department of Food Science, School of Agriculture, Gorgan University of Agricultural Sciences and Natural Resources, Gorgan, Iran.
authors.forename: Nasim
authors.initials: N
authors.lastname: Meshginfar
authors.affiliation: Associate Professor, Department of Food Science, School of Agriculture, Gorgan University of Agricultural Sciences and Natural Resources, Gorgan, Iran.
authors.forename: Alireza
authors.initials: A
authors.lastname: Sadeghi-Mahoonak
authors.affiliation: Assistant Professor, Department of Food Science, School of Agriculture, Gorgan University of Agricultural Sciences and Natural Resources, Gorgan, Iran.
authors.forename: Aman Mohammad
authors.initials: AM
authors.lastname: Ziaiifar
authors.affiliation: Associate Professor, Department of Food Science, School of Agriculture, Gorgan University of Agricultural Sciences and Natural Resources, Gorgan, Iran.
authors.forename: Mohammad
authors.initials: M
authors.lastname: Ghorbani
authors.affiliation: Associate Professor, Department of Food Science, School of Agriculture, Gorgan University of Agricultural Sciences and Natural Resources, Gorgan, Iran.
authors.forename: Mahdi
authors.initials: M
authors.lastname: Kashaninejad
keywords: Antioxidant Peptides; Enzyme Hydrolysis; Optimization; Protein Hydrolysate