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Protein hydrolysate (PH) from viscera of cultured Siberian sturgeon (Acipenser baerii) was produced. To optimize the production conditions, Response Surface Method (RSM) was employed to examine the effects of three different operating conditions, including time, pH, and enzymatic concentration (Alcalase) on the degree of hydrolysis.The mathematical model showed acceptable fitness of the experimental data as R2 equaled 0.97, which indicated  that   major part of  the  variability  within  the  range  of  values could  be explained  by  the  model. The results showed that the highest degree of hydrolysis (58.21%) was related to the treatment which happened at the enzymatic concentration of 2%, 60 minutes time, and pH=8. Treatment under hydrolysis condition (i.e., E/S = 2%, Time = 45 min, and pH = 8.5) had the highest protein content (42.37g/l), which was used as an alternative to commercial peptone medium (Triptic soy broth) to assess the growth of Salmonella typhi bacteria from 0 to 48 hours. Although there was an upward trend in growth rate of S. typhi both in control and No. 15 (Alcalase) treatments, the log growth of control treatment was found to be better than that of Alcalase treatment. However, there existed no significant difference between the two treatments.

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In this study, gelatin was first extracted by alkaline and acidic treatment including 0.19 N NaOH and 0.12 N acetic acid solution by ratio of skin of rainbow trout (Oncorhynchus mykiss (to solution of 1 to 7 and then heat treatment in 50 °C. Then, hydrolysed by alcalase enzyme for 4 hours with the ratio of enzyme to the substrate 1 to 100 and the degree of hydrolysis were measured after 4 hours. DPPH and ABTS free radical scavenging activity, as well as reducing power assay of gelatin hydrolysate were measured. The results showed that the degree of hydrolysis after 4 hours was 46/7%. Also the highest DPPH and ABTS free radical scavenging and reducing power at concentration of 10 mg/ml were 39/8%, 50/7%, and 0/123, respectively. The skin from fish filleting can be a suitable raw material for extraction of peptides with biological activities. The results showed that peptides derived from rainbow trout fish skin gelatin can be considered as a natural antioxidant.

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Aims: the aim of this study was to extract gelatin from the skin of farmed great sturgeon at different temperatures, hydrolysis using Alcalase enzyme, and to measure molecular weight distribution of peptides, amino acid composition and antioxidant activity of hydrolysates.
 
Materials & Methods: After removing pigments and non-collagenous proteins, defatting, and swelling of triple-helix structure, gelatin was extracted at temperatures of 50, 60, 70 and 80 ºC for 6 h and then hydrolysed using Alcalase (E/S ratio of 1:20 w/w) for 3 h. Molecular weight distribution of peptides, amino acid composition and antioxidant activity of hydrolysates were determined.
 
Findings: Degree of hydrolysis reached its maximum within the first 30 min. Hydolysate from extraction temperature of 80 ºC had the highest DH.  No significant differences were found among hydrolysates with regards to amino acid composition and peptide molecular weight distribution. At of 60 ºC, the content of small peptides (< 1 kDa) and amino acids were slightly higher compared to other samples. This could influence antioxidant activity to some degree. At higher extraction temperature of gelatin, the efficacy of hydrolysates in preventing the loss in total sulfhydryl groups content was decreased (P < 0.05) while TBARS and surface hydrophobicity were not influenced (P < 0.05).
 
Conclusion: Extraction temperature of gelatin did not reveal a considerable effect on properties and antioxidant activities of the resulting hydrolysates and gelatin hydrolysates with antioxidant activity and rich in peptides with molecular weight less than 1 kDa could be produced at 50 ºC.

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In this research, enzymatic hydrolysis of casein was performed using alcalase and pancreatin enzymes under optimal conditions. Then, the effect of type and combination of maltodextrin and gum Arabic carriers on physicochemical properties (moisture content, water activity, bulk density, tapped density, solubility, hygroscopicity), maintaining antioxidant activity (ABTS, DPPH and hydroxyl radical scavenging activities, reducing power, Fe²⁺ and Cu²⁺ chelating activity), morphology and mean particle size of spray-dried casein hydrolysates was evaluated. The results showed that moisture content, water activity, bulk density, tapped density and solubility as equally were affected by type and combination of carrier (P< 0.05). The hygroscopicity value of casein hydrolysates decreased significantly after the microencapsulation process. The antioxidant activity of the hydrolysates varies depending on type of enzyme. For example, ABTS and hydroxyl radical scavenging activities of pancreatin hydrolysates were higher than alcalase types (P< 0.05). The combination of maltodextrin and gum Arabic showed the best effect in maintaining of ABTS radical scavenging activity (92.72-94.93%), DPPH (98.47-98.94%), hydroxyl radical scavenging activity (88.59-94.95%), reducing power (98.94-99.65%), Fe²⁺ chelating activity (98.38-98.61%) and Cu²⁺ chelating activity (82.86-98.12%). The images of the electron microscope showed the presence of particles with different size distribution and wrinkles. In addition, the samples produced with gum Arabic had a larger particle size than maltodextrin. Finally, the results of this study showed the effectiveness of spray-drying process on the production of microencapsulated hydrolysates with desired physical, stability and antioxidant properties. 

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The study was conducted exploit the proteins of the pods of some types of plants, such as Prosopis juliflora pods, that are considered by-products in many countries and considered a good source of protein in the preparation of protein hydrolysers and evaluating their effect on inhibiting brown discoloration of apple slices and compared with anti-browning agents (ascorbic acid, acetic acid, and sodium chloride) when stored in the refrigerator for 0, 5 and 8 days. The chemical composition of the moisture, protein, fat, ash, and carbohydrate of the P. juliflora pods was estimated, then the hydrolysis process was carried out using the enzymes trypsin and papain for 300 minutes. Amino acids and FTIR analysis of protein hydrolysates were determined. Significant changes (p≤0.05) in pH, total soluble solids, and non-significant changes in titration acidity of apple slices treated with protein hydrolysis and anti-browning agents were studied and significantly decreased (p≤0.05) in the activity of polyphenol oxidase until the end of the storage. The brown coloration decreased when treated with protein hydrolysates compared to other treatments, but non-significant changes. As a result, apple slices can be preserved with protein hydrolysers for several days in the refrigerator.