---

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.

---

The response surface methodology was employed to optimize the effects of pH, temperature (˚C), time (min) and the ratio of enzyme to substrate (% of substrate) on the hydrolysis process of cuttlefish muscle by alcalase. Central composite rotatable design with 5 levels and 4 factors and α=2 was used for the optimization of the process to gain the highest degree of hydrolysis. pH, temperature, time, enzyme concentration, interaction of temperature-enzyme concentration, square of pH, temperature, time and enzyme concentration had significant effects on the process. The R2 = 0.95, lack of fit < 0.05 and adeq-Precision of 14.16 for the model showed that the model could explain the variability within the range of values. The optimum condition for 42.0117 % of degree of hydrolysis was determined by Design Expert as pH 8.19, temperature 50.23, time 129.62 and enzyme2.15%.

---

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.

---

In this study Response Surface Methodology (RSM) was employed to investigate the effects of different operating conditions on the hydrolysation process of poultry by-products protein by the alcalase. Central Composite Design (CCD) by 5-level and 3-factor was used for the optimization of the hydrolysate production and to evaluate the effects and interactions of process variables: time (minute), temperature (C^◦) and enzyme to substrate ratio on the response. The response was included degree of hydrolysation (%). The mathematical model showed good fit with the experimental data, since the R² of 0.96 indicated that 96% of the variability within the range of values studied could be explained by the model. Furthermore lake of fit of the model was not significant (p<0.05). The optimum conditions for production of poultry by-products protein hydrolysate by 15.24% degree of hydrolysis were established as an enzyme activity to substrate ratio 0.07 AU/g protein; time 127.69 minute, and temperature 52.51°C. According to amino acid analysis and chemical score, methionine and histidine was the limiting amino acids in the hydrolysate. The poultry by-products protein hydrolysate tends to be a potential source in balanced fish diets and functional additive in food industries.

---

Diabetes mellitus is a major health problem in the worldwide. Inhibition of DPP-IV is one of the methods to control diabetes type 2. Inhibition of this enzyme may improve glycemic control in diabetics by preventing the rapid breakdown and there by prolonging the physiological action of incretin hormones. Furthermore, improving the antioxidant system in diabetic patients can prevent the occurrence of secondary disease caused by oxidative stress. Therefore, the head of skipjack tuna was hydrolyzed with alcalase enzyme (1/5% of raw material weight) for 4 hours, in order to produce a product with antidiabetic and antioxidant activities. The DPP-IV inhibition activity, DPPH radical scavenging activity and reducing power of hydrolysate were measured. The results showed that the skipjack tuna head protein hydrolysate possess bioactive properties in a concentration dependent manner and increasing the protein concentration leads to a significant increase in bioactive properties of hydrolyzed product (p≤0.05). The IC50 of protein hydrolysate in DPP-IV inhibition and DPPH radical scavenging activities were obtained 1.016±0.02 mg/ml and 0.297±0.015 mg/ml, respectively. Also the reducing power of hydrolysate was 0.176±0.002 in 2.5 mg/ml protein concentration. Overall, according to the obtained results, it can be concluded that protein hydrolysate of skipjack tuna head possess high antioxidant and antidiabetic activities in vitro, and can be used as a food additive to enhance health level if additional research be conducted.

---

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.

---

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.

---

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.