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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 study, the effect of enzyme type (alcalase and pepsin) and process time (50-300 minutes) on the degree of hydrolysis and antioxidant indices including free radical scavenging of DPPH, ABTS, hydroxyl, reducing power, and chelating activity of Iron and copper ions were evaluated for navy bean protein (Phaseolus vulgari L.). Also, the composition of amino acids (hydrophobic and antioxidants types) and structural properties (FTIR) of primary protein and hydrolysates were investigated. The results showed that enzymatic hydrolysis improves antioxidant properties. Also, the composition of amino acids has a significant effect on antioxidant activities. On the other hand, the type of enzyme and the time of the hydrolysis process affected the degree of hydrolysis and the antioxidant activity of the hydrolysates. Thus, the highest percentage of free radicals scavenging of DPPH (82.4%), ABTS (58.3%), reducing power (0.97), hydroxyl radical scavenging (57.5%), and chelation of Fe (53.7%) and Cu ions (12.1%) were affected by the type of enzyme and process time. Among different treatments, the highest value of these indices (except copper ion chelating) was related to hydrolysates with alcalase. Structural properties of white bean protein were evaluated and enzymatic hydrolysis caused changes in the amide regions (I and II) as well as exposure to some hydrophobic-buried groups. The results of this study indicated the positive effect of enzymatic hydrolysis on the production of antioxidant hydrolysates that can be used in the food industry.

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The present work aimed to study the effect of enzymatic hydrolysis of sarcoplastic and myofibrillar proteins from pangasius sutchi fish on the chemical compositions, the solubility, degree of hydrolysis (DH), peptide content and amino acid compositions was evaluated and their molecular weight recorded. The fish sarcoplasmic protein hydrolysates (SPHs) and myofibrillar protein hydrolysates (MPHs) were produced using three types of proteases: papain, alcalase and flavourzyme. Physicochemical properties of proteins and molecular weight were investigated. Results indicated that type of protease affected the degree of hydrolysis (DH), where all of the enzymes showed high rate of hydrolysis during the first hour, and then gradually decreased. The type of enzyme and the extent of the DH greatly influenced the amino acid residue composition and the molecular weight of the protein hydrolysates. Different amino acid composition of proteins and their hydrolysates was observed. The soluble protein and peptide content of hydrolysates significantly increased by the increase in time of incubation. The high amount of hydrophobic and aromatic amino acids in the SPH and MPH can enhance the biological activities of the peptides. Results suggest that the protein hydrolysates derived from patin may be used in functional food and supplements.
 

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 In view of the increasing sulphur deficiency in Poland’s soils, in 2007-2010, a field experiment was performed with white mustard (Sinapis alba L.) in Haplic Luvisol with low sulphur content (mean – 9.4 mg kg^-1). The aim of the research was to evaluate the effect of varied sulphur application methods (foliar and pre-sowing soil application), forms (elemental and ionic), and rates (0, 20, 40, 60 kg S ha^-1) on the content of protein in mustard seeds, as well as on its amino acid and fraction composition. The research showed that of all the studied factors, the sulphur application rate affected the protein content the most. As compared with the control, sulphur application increased the overall sums of essential and dispensable amino acids in the mustard seeds as well as their quantitative ratio. The biological protein value indices (Chemical Score and Essential Amino Acid Index) point to a clearly positive effect of sulphur on the amino acid composition of the protein, including sulphur-containing methionine, an amino acid limiting protein biosynthesis. The sulphur rate significantly affected the content of all the protein fractions assayed, except for glutelins.