The effect of the addition of different concentrations of chitosan (0–2.0% w/w) on the gelling properties of surimi gels made from African catfish (Clarias gariepinus) was tested. Lipid oxidation, total volatile basic nitrogen (TVB-N), and aerobic plate count (APC) changes during 20 days of storage at 4oC also were evaluated. Surimi gels with 1.5% (w/w) chitosan added exhibited the highest improvement in gel strength (58.92%), whiteness (13.18%), and water holding capacity (36.8%). Incorporation of 2.0% (w/w) chitosan in gels resulted in the lowest TVB-N value (36.63 mg N/100 g) at the end of the 20 days storage period. Both the peroxide values and the 2-thiobarbituric acid values increased more slowly in the chitosan-treated gels than in the control gel during the storage period. Chitosan at concentrations of 1.75% and 2.0% (w/w) conferred the best antioxidant effect on catfish surimi gels and resulted in a significant reduction in APC. Based on the microbiological acceptability limit (106 cfu/g), the shelf life
of surimi gels with 1.75% and 2.0% (w/w) chitosan was extended to 12 days in refrigerated storage at 4oC, whereas the other samples lasted only 8 days. Hence, the addition of 1.5–2.0% (w/w) chitosan is a promising approach for the preparation of catfish surimi gels, as it improves texture, prevents lipid oxidation, and inhibits microbial growth.
This study aims to determine the combined effects of hydrolysis time, temperature, pH and ratio of enzyme to substrate on the degree of hydrolysis (DH) of silver catfish frame using Response Surface Methodology. The proximate compositions of silver catfish frame and silver catfish hydrolysate powder were determined as well. The effects of independent factors were described using a three-level factors Face Centered Central Composite design. The suggested hydrolysis conditions for obtaining the optimum DH using Alcalase® were – temperature of 55oC, hydrolysis time of 163 min, pH of substrate at 9.45 and an enzyme concentration of 2.0%. The generated model showed a quadratic fit with experimental data. Proximate analyses revealed that silver catfish frame contained 25.02% protein, 68.21% fat and 7.08% ash. While silver catfish frame hydrolysate powder contained 65.05% protein, 32.92% fat and 0.86% ash. The protein recovery in silver catfish frame hydrolysate was as high as 71.6%.
The physicochemical properties of silver catfish frame hydrolysate powder at three different degree of hydrolysis, DH43%, DH 55% and DH 68% were studied. The hydrolysates powder were obtained by hydrolysis using Alcalase®, centrifugation and spray drying of the supernatant. The study found that preparation of these hydrolysates affected the protein, ash and fat content as well as amino acid composition. As for essential amino acids, their values were generally considered as adequate as compared to the suggested essential amino acids profile of FAO/WHO. The results showed that SFHs were rich in lysine and glutamate. Hydrolysate at DH 68% exhibited better peptide solubility and water holding capacity. As degree of hydrolysis increased, emulsifying capacity and foaming capacity of the hydrolysate decreased. It was also found that the lightness in hydrolysate powder decreased with increase in degree of hydrolysis. This study shows that silver catfish frame hydrolysate has good solubility, good foaming properties and light colour profile, thus having high potential as food ingredient.
The effect of degree of hydrolysis (DH) on the physicochemical properties of cobia frame hydrolysate was determined. Three levels of degree of hydrolysis of cobia frame hydrolysate were studied, which were 53%, 71% and 96%. After enzymatic hydrolysis using Alcalase®, the samples were spray-dried. Cobia hydrolysate powder samples were analyzed for their proximate analysis and physicochemical properties. The proximate analysis showed significant differences in fat and ash content only. DH96 hydrolysate showed desirable essential amino acid profile for human requirement except for methionine and isoleucine. The study found that cobia frame hydrolysate had good colour, emulsifying capacity and excellent foaming properties. However, there were no significant differences in water-holding capacity, oil-holding capacity and peptide solubility among the hydrolysate samples. This study suggested that cobia frame hydrolysate is a potential ingredient and foaming agent for food industry.
This study aimed to determine the best parameters (types of buffer, hydrolysis time and enzyme concentration) used to produce good quality of liquid protein hydrolysate from Yellowstripe scad in terms of high yield, protein content and concentration. The choice of buffer (sodium or potassium buffer), hydrolysis time (1 h, 2 h, 3 h or 4 h) and enzymes concentrations (0.5%, 1.0%, 1.5% and 2.0%) were investigated. The results obtained from two way ANOVA showed that these parameters had significant difference (p
The aim of this study is to determine the optimization of enzymatic protein hydrolysis conditions on the angiotensin-converting enzyme inhibitory (ACEI) activity of blood cockle meat. Preliminary study was carried out to evaluate the effect of different commercial proteinases (Alcalase®, Protamex™, Neutrase®, pepsin, papain, trypsin and α-chymotrypsin) and hydrolysis time on the ACEI activity of cockle’s meat. The proteinase with the highest ACEI activity will be used in the optimization study using Response Surface Methodology. A face-centered central composite design was employed to investigate the effect of hydrolysis conditions parameters (i.e hydrolysis time, pH, hydrolysis temperature and enzyme to substrate (E/S) ratio) towards ACEI activity of cockle’s meat. Preliminary study found that the highest ACEI activity was given by Protamex™ at 6 hrs. Therefore, optimization study was carried out using Protamex™ at 4-8 hrs hydrolysis times with temperature of 35-60oC, pH of 5.5- 7.5 and E/S of 0.5-1.5%. All variables were successfully fitted with the quadratic model (p < 0.0001) with a non-significant lack-of-fit (p = 0.3665), and also possess good coefficient of determination (p = 0.8666) and adjusted R-square (p = 0.8158). The optimum hydrolysis conditions were found to be at temperature of 59.8o C, time of 4.69 hrs, pH of 5.59 and E/S ratio of 0.9%. ACEI activity of the experimental value (97.8%) agreed with the predicted value (99.2%) within 95% confidence interval.
This study reported the extraction optimization and characterization of cobia (Rachycentron canadum) skin gelatin. Optimization study was carried out to determine the effect of CH3COOH concentration, skin to water ratio, extraction temperature and extraction time on gelatin yield (GY) and gel strength (GS) using Response Surface Methodology (RSM). The optimum conditions were 0.15mol/L for CH3COOH concentration, 82.4oC of extraction temperature, 6 h of extraction time and 1:6 of skin to water ratio, which produced cobia gelatin with GY of 20.10% and GS of 205.6 g. Characteristics of cobia skin gelatin (CG) were then compared to that of commercial bovine gelatin (BG). It was found that the most dominant amino acid in CG was glycine, proline and alanine. There was no difference in foaming and emulsifying properties of CG and BG at 1% concentration, but at 2% and 3% concentration, BG performed better. CG was found to have higher fat binding capacity but lower water holding capacity than BG. Least gelling concentration for CG was recorded at 2% while for BG at 1%. CG and BG had a pI at pH 6.05 and 4.82, respectively. This study shows that cobia skin gelatin has potential as halal alternative to bovine gelatin in food industry.