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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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Optimization of protein hydrolysate from head and arms of cuttlefish (Sepia pharaonis) was examined. For this purpose, response  surface  methodology  (RSM)  was  employed  to  investigate  the effects  of different  operating  conditions  on  hydrolysis  process  of  cuttlefish protein by the application of alcalase enzyme. A Box-Behnken design with three factors at three levels was used for hydrolysis optimization and to check any individual or interaction effects between the experimental factors. In this method, the effects of three independent variables, including temperature, pH and enzyme to substrate ratio, were investigated on hydrolysis rate as a surface response. The mathematical model showed a good fitness with experimental data. Optimum conditions for temperature, pH and enzyme quantity were determined as 54.33 ˚C, 8.49 and 1.97 %,  respectively, which caused nearly 14.5 % hydrolysis degree. Based on the lack of fitness factor which was not significant, it was deduced that the resulted model was capable of prediction at different studied levels of variables. In this study, in order to confirm the conditions that proposed by mathematical equation, the hydrolyzed protein was produced accordingly at which resulted in a 16.8% hydrolysis degree. This finding was according to the aim of present trial by producing a protein hydrolysate with maximum hydrolysis degree. Then the functional properties of protein hydrolysate powder from optimized conditions were measured. Functional properties of this protein powders indicated a good solubility, but weak levels of emulsifying and foaming capacities.

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Aims: Skipjack tuna has the highest level of catch rate among tuna all over the world. Its head contains about 64% protein. Many Protein Hydrolysates and peptides obtained from various marine sources have a high antioxidant power. The aim of this study was to investigate the antioxidant activity of Protein Hydrolysate in Skipjack tuna head.
Materials & Methods: In this experimental study, 30 Skipjack tunas were investigated. At first, the amount of different compounds (protein, fat, ash, and moisture) was evaluated in the raw material; then, the hydrolysis process was performed by Alcalase enzyme and the hydrolysis degree of the protein hydrolysate was evaluated at different times. The antioxidant activity of the protein hydrolysate mixture was measured by DPPH radical scavenging activity, iron revival power, and ABTS radical inhibitory activity. For data analysis, the analytical tests were used.
Findings: The main part of the fish head was protein and it had high levels of ash. The degree of hydrolysis increased with increasing time and was it significant at 15, 60, and 120 minutes (p<0.05), but not significant at 120 and 240 minutes (p<0.05). DPPH radical scavenging activity increased with increasing hydrolysis time and there was a significant difference in all samples obtained from different times (p<0.05). The iron reduction capacity of the protein hydrolysate samples increased with increasing the hydrolysis time, and the highest amount was at 240 minute. The samples obtained from different times had a significant difference in iron reduction capacity (p<0.05). Increasing the concentration of protein hydrolysate increased inhibitory activity (p<0.05).
Conclusion: Protein hydrolysate in Skipjack tuna head has a high antioxidant activity and can be used in food products to increase oxidation stability.

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Aim: In this study, the antioxidant properties of hydrolyzed protein from longtail tuna dark muscle with commercial enzymes (alcalase, alkaline protease, and evatase) were investigated.
Materials & Methods: Protein hydrolysates from tuna dark muscle were prepared by different enzymes Degree of hydrolysis (DH) was performed by TCA technique. The five aliquots at 60, 180, 240, 300, and 360 min were gathered during hydrolysis. The antioxidant activity of aliquots was monitored by in vitro assays (DPPH inhibition ability and Ferric (Fe3+) reducing power).
Findings: The antioxidant activities of protein hydrolysate from tuna dark muscle (TDM) increase with increasing time and DH. Alcalase hydrolyzed protein (AHP) generally showed higher antioxidative activity than evatase hydrolyzed protein (EHP) and alkaline protease hydrolyzed protein (APHP). Among the samples (concentration 3 mg.ml^-1), AHP at 360 min significantly exhibited the highest ability to scavenge DPPH radical (72.6 %). Furthermore, AHP and APHP significantly showed a minimum IC50 value of 1.1 mg.ml^-1 at 240 and 360 min hydrolysis. APHP significantly exhibited the highest ferric reducing power of 0.83 at 300 min and 0.76 at 240 min. AHP and APHP significantly showed the highest ferric reducing power of 0.74 at 360 min (p < 0.05).
Conclusion: This study confirmed that protein hydrolysate from TDM could be a good source of antioxidant peptides. In addition, the antioxidant activity of hydrolyzed protein relay on protease type and hydrolysis condition.
 

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In the present study Protein hydrolysate was prepared from the sheep visceral (stomach and intestine) using Alcalase 2.4 L. The effect of temperature (40, 45, 50 and 55 °C), time ( in six levels) and enzyme/substrate ratio (30, 60 and 90 Anson unit), on degree of hydrolysis and antioxidant activity were investigated using factorial experiment. The highest degree of hydrolysis was observed at 45 °C, after 180 min and enzyme/substrate ratio of 90 Anson unit/ Kg substrate (p< 0.05). Under these conditions, degree of hydrolysis was 36/92%. To study the antioxidant activity of protein hydrolysate, DPPH radical scavenging activity, ferric reducing power and effect of protein hydrolysate on stability of soybean oil were measured. All antioxidant activity experiments were performed at constant temperature (45°C). The highest DPPH radical scavenging activity and ferric reducing power were achieved after 150 min at enzyme/substrate ratio of 90 Anson unit/ Kg substrate (p< 0.05) and after 180 min at 90 Anson unit/ Kg substrate (p< 0.05), respectively. Results show that protein hydrolysate can be used as a natural antioxidant source instead of synthetic antioxidants.    

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This study aimed to evaluate the effect of squid protein hydrolysate prepared from protamex (P1, P2, P3) and alcalase (A1, A2, A3) enzymes respectively, at 0.5%, 1% and 1.5% concentration and also control sample (0%), on some physicochemical and organoleptic properties of low-fat set style yoghurt such as viscosity, synersis percentage, water holding capacity, acidity, pH, odor, taste, texture and color. Results showed that the lowest viscosity (416/66) was for control sample. Protein hydrolysates of both of enzymes increased viscosity while the highest amount was for P3 and A3. The highest pH and lowest acidity were for the control sample and protein hydrolysate in yogurt formulation decreased pH and increased acidity of samples. Maximum synersis obtained with control sample (4.47); protein hydrolysate decreased synersis while 1% protein hydrolysate with alcalase had the lowest synersis (0.33). Results of organoleptic tests showed that alcalase samples, especially in higher concentrations, modified odor and taste of low-fat yoghurt but these changes were not clear in texture and color. Generally, squid protein hydrolysate with alcalase and protamex in yoghurt formulation improved functional properties of low-fat yoghurt and it was more efficient in alcalase treatments in comparison with protamex.

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Abstract
Bioactive peptides are considered specific protein fragments that are inactive within the sequence of the parent protein. After they are released by enzymatic hydrolysis, they may exert various physiological functions. In the present study, response surface methodology was used to optimize hydrolysis conditions for preparing protein hydrolysate from whey protein, using Alcalase 2.4L enzyme. The investigated factors were temperature, time and enzyme/substrate ratio which were selected in the range 43-52°C, 65-175 min and 45-90 AU/Kg protein, respectively to achieve maximum degree of hydrolysis. Experiments were designed according to the central composite design. Each of the studied variables had significant effect on degree of hydrolysis (p<0/05). The optimum conditions to achieve the highest degree of hydrolysis were temperature 49.02°C , time 174.28 min, and enzyme / substrate ratio 90AU/Kg protein. Under these conditions, hydrolysis degree was 41.57 %. Regression coefficient for, chariot models (Quadratic type) was, 0.95. The values indicated the high accuracy of the model to predict the reaction conditions for different variables.

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Tomato waste can be used as a new protein source for the production of hydrolyzed protein. Free radicals are among the most important factors in the development of cancer and genetic mutations, which have become one of the greatest threats for human health in recent centuries. In this research, hydrolysis condition of tomato seed protein (temperature, time and amount of alcalase enzyme) to achieve maximum antioxidant activity and nitric oxide reducing power were investigated. The values were evaluated using Design Expert software and analyzed by the response surface methodology. Results showed that with the optimimizing hydrolysis conditions using the alcalase enzyme, it is possible to achieve a products with significant DPPH radical scavenging activity and nitric oxide reducing power. The results indicate that optimum conditions for achieving the maximum DPPH free radical inhibition activity and nitric oxide reducing power is temperature of 50 ° C, hydrolysis time 210 min, and the amount of enzyme 1.85%. Under these condition the amount of DPPH free radical inhibition activity and nitric oxide reducing power was 85.53 and 61.17, respectively. The results showed that the hydrolyzed protein produced from tomato seed could be used as a natural additive in the foods formulation and pharmaceutical uses with high antioxidants and nitric oxide reducing activity.

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In the present study, the antioxidant properties of different molecular weight fractions and different concentrations of protein hydrolysate from Common carp (Cyprinus carpio) head were investigated. Fish heads were hydrolyzed by Alcalase enzyme (1% v/w) at 55˚C and pH 8 during 180 min. The supernatant was fractionated to three different molecular weight fractions of <3, between 3 and 10 and >10 KDa by ultrafiltration. The results showed a significant difference between DPPH radical scavenging activity of the different molecular weight fractions, and the highest and the lowest values ​​were observed in the fractions of 3-10 and less than 3 KDa, respectively (p <0.05). The fraction with molecular weight of 3-10 KDa showed the lowest IC₅₀ (1.15±0.015 mg/ml) for DPPH scavenging activity.  As the concentration increased, ferric ion reducing power of all molecular weight fractions were increased, and the highest value was observed in the molecular weight of more than 10 kDa (p <0.05). Significant differences of ABTS radical scavenging activity were observed between the different molecular weight fractions at all concentrations, and the highest and the lowest values ​​were observed in the molecular weight fractions of 3-10 and less than 3 kDa, respectively (p <0.05). The molecular weight fraction of 3-10 kDa, exhibited the lowest IC₅₀ value for ABTS radical scavenging activity (1.1±0.01 mg/ml). In general, according to the positive function of Common carp head protein hydrolysate at different concentrations and different molecular weights on DPPH and ABTS radical scavenging activity and ferric ion reducing power, it can be stated that this protein hydrolysate can be considered as a natural antioxidant for use in the food industry or animal, poultry and aquatic feed.

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The purpose of this study was to investigate the effect of microwave pretreatment on the degree of hydrolysis and antioxidant activity of Beluga (Huso huso) viscera protein hydrolysate. For this purpose, the samples were hydrolyzed after two conditions of pretreatment including no treatment with microwave or after ten minutes treatment with microwave (frequency 2450 Hz and temperature 90 °C), by alkalase enzyme with a concentration of 2%, temperature of 55°C and pH 8, and then the degree of hydrolysis and antioxidant activity of the produced samples were evaluated. According to the results, the degree of hydrolysis after microwave treatment was significantly higher than the sample without microwave treatment (p<0.05). Also, the sample produced after microwave treatment showed higher antioxidant activity (DPPH and ABTS radicals scavenging activity and Fe reduction capacity) compared to the control treatment (p<0.05). The IC₅₀ values ​​of this treatment in inhibiting DPPH and ABTS radicals scavenging activity were obtained as 1.25 mg/ml and 1.63 mg/ml, respectively, which was significantly lower than the control treatment (p<0.05). Also, in both samples, antioxidant activity increased significantly with increasing concentration (p<0.05). In general, it can be stated that 10 minutes of microwave pretreatment at 90 °C has a favorable effect on the properties of Beluga viscera protein hydrolysate which can indicate the applicability of this technology in the production process of fish protein hydrolysate.
 

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Oxidation in living organs causes dangerous diseases, including cancer, and in food, it causes spoilage and heavy economic losses. Synthetic antioxidants have adverse and dangerous effects on human health, therefore identifying natural antioxidant compounds is one of the main needs of the food industry. In fish processing industries, about 50-70% of fish, which are potential sources of valuable nutritional compounds such as essential amino acids, are produced as waste. Therefore, finding a way to optimally use these wastes and produce healthy compounds with high added value such as bioactive peptides has great importance. In this research, the effect of hydrolysis conditions (time: 30-300 min and enzyme concentration 0.5-3 %) and type of protease (alcalase and pancreatin) on the degree of hydrolysis and antioxidant properties (DPPH radical scavenging activity, Fe chelating activity, nitric oxide radical inhibition, total antioxidant capacity and Fe reducing power) of protein hydrolysate from skipjack viscera was investigated using the response surface methodology. The results showed that the optimum conditions for achieving the most antioxidant properties with alcalase and pancreatin were: hydrolysis time of 146.9 and 171.67 minutes and enzyme concentration of 1.94 and 2.17%; in these conditions, the degree of hydrolysis of the produced protein hydrolysates was 25.12% and 20.35%, respectively. Comparing the antioxidant properties of hydrolysates produced by both proteases showed that the alcalase enzyme led to the production of protein hydrolysates with stronger antioxidant properties than pancreatin. Therefore, it can be concluded that the protein hydrolysate of the skipjack fish viscera using alcalase enzyme as a healthy and value-added product can be used in the production of functional products and health supplements.
 

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In this study, the effect of microwave pretreatment at the power of 500 and 900 W on the antioxidant properties (DPPH radical scavenging activity and total antioxidant capacity) of flaxseed protein hydrolysate was investigated in the period of 30-210 minutes. In the next step, the effect of different concentrations (20-100 mg/ml) of the optimum treatment on the antioxidant properties (total antioxidant capacity, Fe reducing power, DPPH radical scavenging activity and Fe chelating activity) was investigated and was compared with the antioxidant capacity of vitamin C as a synthetic antioxidant and unhydrolyzed flaxseed protein. The results showed that microwave pretreatment at a power of 500 W significantly increased the antioxidant properties (DPPH radical scavenging activity and total antioxidant capacity) of flaxseed protein hydrolysate, but higher microwave power (900 W) led to reduction of antioxidant activity in comparison to the sample without pretreatment or the sample with microwave pretreatment with a power of 500 W. The sample with microwave pretreatment with a power of 500 W and hydrolysis time of 180 minutes was selected as the optimum treatment with the highest total antioxidant capacity and DPPH radical scavenging activity. Investigating the effect of concentration on the antioxidant properties of hydrolyzed protein showed that the highest DPPH radical scavenging activity (52.7 %), total antioxidant capacity (1.35 absorbance at 695 nm), Fe reducing power (0.859 absorbance at 700 nm) were achieved at the concentration of 60 (mg/ml) and the highest Fe chelating activity (50.83%) was obtained at the concentration of 80 (mg/ml). As a result, the flaxseed protein hydrolysate with considerable antioxidant capacity, can be used in the production of functional food products, nutritional supplements for athletes and the elderly.
 

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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.
 

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Protein hydrolysate is a valuable source of bioactive peptides. The production of protein hydrolysate through fermentation is an environmentally friendly approach preferred over enzymatic and chemical hydrolysis in most cases. This research employed Bacillus species, including Bacillus pumilus, Bacillus coagulans, Bacillus licheniformis, and Bacillus subtilis, to hydrolyze sesame meal protein. The investigated tests included measuring the concentration of peptides by the OPA method, DPPH radical inhibition, and iron ion reducing power, total antioxidant activity, and iron ion chelating activity. The concentration of peptides was evaluated after 24 h for Bacillus species. The lowest peptide concentration (0.656 mg/mL) was associated with the fermented treatment by B. licheniformis, while the highest value (1.38 mg/mL) was observed for the hydrolyzed treatment with B. subtilis. A significant difference (p<0.05) was observed among all the treatments. Results of DPPH radical inhibition showed the highest inhibition was associated with the samples hydrolyzed by B. coagulans (76.6%), and the lowest value was attributed to the hydrolysate by B. licheniformis (57.36%). The sample fermented with B. pumilus exhibited higher reducing power (0.992 absorbance at 700 nm) with a significant difference (p<0.05) observed between the treatments. The highest chelating activity (85.6%) was observed in the sample fermented with B. subtilis. The total antioxidant activity demonstrated that the protein hydrolysate with fermentation by B. coagulans had the highest absorbance value at 695 nm with a significant difference between the treatments (p<0.05). In conclusion, the fermentation of sesame meal protein by Bacillus species resulted in the production of protein hydrolysate with substantial antioxidant activity, positioning it as a promising source for inclusion in food formulations.