Catfish By-products Research Articles

Additive biocomponents from catfish by-products enhance the growth of shrimp Litopenaeus vannamei

Additive biocomponents from catfish by-products enhance the growth of shrimp Litopenaeus vannamei

Microbial Transglutaminase Cross-Linking Enhances the Textural and Rheological Properties of the Surimi-like Gels Made from Alkali-Extracted Protein Isolate from Catfish Byproducts and the Role of Disulfide Bonds in Gelling.

The texture of surimi-like gels made from the protein isolate extracted from catfish byproducts has been proven to be brittle and lack elasticity. To address this issue, varying levels of microbial transglutaminase (MTGase) from 0.1 to 0.6 units/g were applied. MTGase had little effect on the color profile of gels. When MTGase at 0.5 units/g was employed, hardness, cohesiveness, springiness, chewiness, resilience, fracturablity, and deformation were increased by 218, 55, 12, 451, 115, 446, and 71%, respectively. A further increase in added MTGase did not lead to any textural improvement. In comparison to the gels made from fillet mince, the gels made from protein isolate were still lower in cohesiveness. Due to the activated endogenous transglutaminase, a setting step enhanced the textural properties of gels made from fillet mince. However, because of the endogenous proteases-induced protein degradation, the setting step led to a texture deterioration of the gels made from protein isolate. Gels made from protein isolate showed 23-55% higher solubility in reducing solution than in non-reducing solution, suggesting the vital role of disulfide bonds in the gelation process. Due to the different protein composition and conformation, fillet mince and protein isolate exhibited distinct rheological properties. Sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE) showed the highly denatured protein isolate was susceptible to proteolysis and prone to disulfide formation during the gelation process. It also revealed that MTGase had an inhibitory effect on the proteolysis induced by endogenous enzymes. In view of the susceptibility of the protein isolate to proteolysis during gelation, future research should consider including other enzyme inhibitory agents in the presence of MTGase to improve the gel texture.

Effect of rosemary (Rosmarinus officinalis) extract on the protection of the fishballs from knife fish (Chitala chitala) and striped catfish by-product (Pangasianodon hypophthalmus) against spoilage during frozen storage

The study aimed to investigate the effect of rosemary (Rosmarinus officinalis) extract on the quality changes of fishballs from knife fish (Chitala chitala) and striped catfish byproduct (Pangasianodon hypophthalmus) during frozen storage. Fishballs were supplemented with rosemary extracts at two concentrations of 13 mg/kg and 156 mg/kg. The control treatment was the sample without extract. The products were steamed, vacuum packed in PA bags and stored at a temperature from -18oC to -20oC. Sampling was done at 0, 30, 60, 90, 120, 150 and 180 days of storage period for analysis of pH, Total volatile base nitrogen (TVB-N), total viable bacteria count (TVC), pathogenic bacteria, sensory properties, peroxide value (PV), Thiobarbituric acid reactive substances (TBARs). Results showed that Escherichia coli and Salmonella spp. were absent in the fishballs, reflecting the safety of products for consumers. Adding rosemary extract at 156 mg/kg in fishballs displayed more effectiveness in inhibiting the formation of lipid oxidation and microbial growth when compared to the control sample during the frozen storage. Based on the results of physicochemical and sensory quality, the supplementation of rosemary extracts showed a significant promise for improving the quality of fishballs. Fishballs from knife fish and striped catfish by-products could be maintained their sensory properties and prolonged their shelf-life up to 180 days of frozen storage.

Color and texture of surimi-like gels made of protein isolate extracted from catfish byproducts are improved by washing and adding soy whey.

Protein extraction from catfish byproducts has been proven economically and technically feasible. However, the gel prepared from protein isolate was dark and lacked elasticity. Byproduct mince washing and application of soy whey were adopted in this study to address the above gel quality issues. Heating soy whey at 75°C for 3min could eliminate over 99.9% lipoxygenase activity and retain more than 50% trypsin inhibitor activity. Washing byproduct mince for 2min with water-to-mince ratio of 2:1 could achieve satisfactory gel color, which was comparable to that of commercial surimi gels. When soy whey was applied, the autolytic enzyme-induced proteolysis was inhibited in a dose-dependent manner by up to 74%. With addition of soy whey, resilience, hardness at maximum force, hardness at 5mm compression, springiness, cohesiveness, chewiness, fracturability, and deformation could be increased by up to 43.10%, 66.92%, 36.72%, 14.59%, 29.17%, 143.25%, 93.82%, and 27.97%, respectively. However, the texture was still inferior to the gel made from fillet mince. SDS-PAGE revealed that myosin was most susceptible to proteolysis and application of soy whey could effectively protect it from degradation. Different from tropomyosin, myosin and actin were greatly involved in disulfide bond formation. PRACTICAL APPLICATION: Catfish byproducts and soy whey, a byproduct from soy protein isolation, are normally treated as waste. The current study proved the possibility to utilize these two byproducts to make value-added surimi-like gel products. Utilization of byproducts would not only increase profitability of catfish and soy processing, but also preserve the precious fish proteins and other health-promoting components.

Isolation of Protease-Producing Bacteria from Shrimp Paste and the Characteristics of Fermenting Catfish Paste

ABSTRACT In this study, six protease-producing halophilic bacterias were isolated from traditional shrimp paste. These strains were used as mixed starter culture to ferment minced catfish muscle. The pH and total volatile base nitrogen in the group with mixed starter cultures (ZB) was lower than that of the group without starter (ZA). The total acidity and the content of amino acid nitrogen and free amino acid in ZB was higher. Additionally, the ZB exhibited a strong umami and fermented flavor. The results show that protease-producing bacteria could improve the flavor and nutritive value of fermented Chinese long-snout catfish by-products.

Protein extraction from catfish byproducts and physicochemical properties of the protein isolates.

In order to optimize protein recovery from catfish byproducts by alkaline extraction, the effects of different factors, including particle size, mince-to-water ratio, pH, and extraction time were investigated. It was found that a protein recovery of about 30% could be achieved. Increases in pH (pH 10.5, 11, and 11.5) not only improved protein recovery, but also increased protein denaturation evidenced by decreased solubility, decreased α-helix, increased β-sheet, and increased random coil. The color and texture of gels made from protein isolate were greatly affected by the pH values used for protein extraction. For the gels made from fillet mince, and protein isolates extracted at pH 10.5, 11, and 11.5, the "L" values were 78.96, 60.38, 57.74, and 54.39, the breaking forces were 205, 492, 585, and 458 g, and deformation values were 10.59, 8.07, 6.73, and 5.04 mm, respectively. Electrophoresis revealed protein degradation during alkali-aided extraction with MHC, the most predominant band, showing about 50% decrease in comparison with fillet mince. It also demonstrated that gelation not only caused cross-linking, but also autolysis with 53%, 56%, 59%, and 81% decrease in MHC intensity for fillet mince, protein isolates extracted at pH 10.5, 11, and 11.5, respectively. Fillet mince and protein isolates exhibited different storage modulus patterns during temperature sweep, implying different gelation mechanisms. This study proved the protein extracted from catfish byproducts was potential to be utilized as edible food components especially in gel making. PRACTICAL APPLICATION: Catfish byproducts, which account for 70% of total weight and 50% of total protein of catfish, are normally used as animal feed, fertilizer, or even waste. This study demonstrated the potential of the utilization of catfish wastes to develop edible food components. This could reduce the total processing waste being discarded into the environment and nutrient loss, therefore increasing profitability of catfish industry.

Protein extraction pH and cross-linking affect physicochemical and textural properties of protein gels made from channel catfish by-products.

Channel catfish farming is very important aquaculture industry in the southern states of the USA. However, huge amounts of by-products are generated from catfish fillet-processing. The by-products (mostly heads and bone frames) are excellent sources of proteins. Currently, catfish by-product has little value, and is regarded as a 'waste', which if not utilized properly could cause serious environmental pollution. Therefore, to find a way to utilize those by-products is critical for the economy of aquaculture. Protein isolates were extracted from the mixture of catfish by-products (heads and frames) under different alkaline conditions (pH 7.5-11) and made into protein gels. Secondary structures of extracted protein isolates were studied. Microbial transglutaminase (MTGase, 0-4 U g-1 proteins) was incorporated to improve gel structure. Gelling, physicochemical, textural and thermal properties of protein gels treated with/without MTGase were investigated. Protein pattern changes of MTGase-treated protein gels were studied and the microstructure of the protein gels was analyzed. Alpha-helicity of protein isolates made at pH 11 was 21.5% lower than that extracted at pH 8.5. Storage modulus (G') of protein gel decreased with increasing extraction pH (pH > 9) of the corresponding protein isolate. MTGase treatment exhibited significant effects on denaturation temperature and enthalpy of protein gels. Excessive MTGase (>2 U g-1 ) could weaken the gel structure. Protein isolates can be extracted from catfish by-products and made into protein gels, which are a value-added product. © 2021 Society of Chemical Industry.

Towards Zero-waste Recovery of Bioactive Compounds from Catfish (Pangasius hypophthalmus) By-products Using an Enzymatic Method

Catfish (Pangasius hypophthalmus) is one of the main seafood products of Vietnam with a large amount of over 1.3 million tons in 2018. However, after the processing, large amount of the harvested catfish is considered as by-products. In this study, catfish by-products have been used to produce three bioactive components, including fish protein hydrolysate (FPH), hydroxyapatite (HA) and lipid fraction by an enzymatic method. The fish by-products were hydrolyzed by using an Alcalase-substrate ratio of 0.4% (v/w) at 60 °C and natural pH for 9 h with a water-raw material ratio of 1:1 (mL/g). The results show that the protein hydrolysate has degree of hydrolysis (DH) of over 30%, nitrogen recovery (NR) of over 80% and contained a large amount of essential amino acids. HA particles have a size of 50–70 nm with high porosity and quite uniformity, suggesting its potential applications such as bone scaffold or regenerative materials. The lipid fraction has high vitamin A content with a small amount of fatty acids (ca. 90 mg/g) that can be refined for further food applications. This recovery method is simple, environmentally-friendly and can be scale-up easily. In addition, the cheap fish by-products were processed to give value-added products as well as reduce the undesirable environmental impact.

Comparing the kinetics of the hydrolysis of by-product from channel catfish (Ictalurus punctatus) fillet processing by eight proteases

Channel catfish farming is the most important warm water aquaculture in the United States and is very important to the rural economy. This study's objective was to investigate the kinetics of the enzymatic hydrolysis of catfish by-product. Channel catfish (Ictalurus punctatus) by-products (heads and frames) were collected from local catfish processing plant. Papain, ficin, bromelain, neutrase, alcalase, protamex, novo-proD and thermolysin were used for hydrolysis. Proteolytic activities of those proteases were examined at different hydrolysis temperature, proteases cost for reaching certain degree of hydrolysis was predicted. Degree of hydrolysis (DH) of the hydrolysates and hydrolysis kinetics were studied. Emulsifying and foaming property and stability of selected hydrolysates were evaluated. Results indicated that thermolysin had the highest activity (8.2 × 108 Azocoll U/g and 5.6 × 106 Azocasein U/g) at 70 °C. The highest DH of the hydrolysates were observed in 120 min with the concentration of 80 AzU/g for all enzymes. Ficin (80 AzU/g) was the most efficient in hydrolyzing the by-product (DH reaching 71%) in 120 min at 30 °C. The hydrolysis curves fit the Peleg model well with R2 higher than 0.91. This study provides important engineering information for choosing proteases and processing conditions for optimization of efficiency, yield and economy.

Effects of mixed starter cultures and exogenous L-Lys on the physiochemical and sensory properties of rapid-fermented fish paste using longsnout catfish by-products

Fermentation is a good way to utilize fish by-products. In this study, the effects of mixed starter cultures and exogenous L-Lys on the physiochemical and sensory properties of fermented longsnout catfish minced meat were investigated. Fish pastes were divided into three groups, including a treated group (sample A), a mixed starter culture-treated group (sample B), and a L-Lys and mixed starter culture-treated group (sample C). The pH and total volatile base nitrogen in the sample C were the lowest among the tested samples. At the final stage of fermentation, the total acidity, amino acid nitrogen content, and free amino acid content in the sample C were the highest among the tested samples. No significant differences in the histamine content or antioxidant activities were observed among the three samples (p < 0.05). An electronic nose test showed that the odors of the samples B and C were similar, but different from those of the sample A. The sample C exhibited a strong umami and fermented flavor and had the best flavor. All the results demonstrated that the mixed starter cultures and L-Lys can improve the flavor and nutritive value of the fish pastes made with Chinese longsnout catfish by-products by fermentation.

Investigation of antioxidant capacity of peptide fractions from the Tra catfish by-product-derived proteolysate using Flavourzyme® 500 mg

In this study, the antioxidant potential of peptide fractions isolated from the Tra catfish (Pangasius hypophthalmus) by-product-derived hydrolysate using ultrafiltration centrifugal devices with 3 distinct molecular-weight cutoffs (MWCOs) of 5KDa, 10KDa, and 30KDa was investigated. Firstly, the chemical composition of the Tra catfish byproducts was analyzed. The result showed that the Tra catfish by-products contained 58.5% moisture, 33.9% crude protein, 50.1% crude lipid and 15.8% ash (on dry weight basis). Secondly, the effects of enzyme content, hydrolysis time on the antioxidant activity of the hydrolysate were studied using DPPH• (2,2-diphenyl-1-picrylhydrazyl) radical scavenging method (DPPH• SM), and FRAP (ferric reducing antioxidant potential) method. Flavourzyme® 500 MG was used for hydrolysis. The result revealed that the antioxidant activity of the proteolysate reached the peak when the hydrolysis time was 3h, enzyme/substrate (E/S) ratio was 25 U/g protein, hydrolysis temperature was 500C, pH was 7, and the degree of hydrolysis (DH) of the hydrolysate reached 37.4%. Next, the proteolysate was further fractionated using MWCOs of 5KDa, 10KDa, and 30KDa and the peptide fractions were investigated for their antioxidant activity. The result showed that the &lt;5KDa fraction showed strongest antioxidant activity with the 50% DPPH• inhibition concentration (IC50) of 3079.34±75.29 μg/mL and FRAP value of 611.28±4.5 μM Trolox equivalent. The second strongest fraction was 5-10KDa with the IC50 and FRAPS value of 4709.3 ± 222.22 μg/mL and 323.62±2.54 μM Trolox equivalent, respectively. The 10-30KDa fraction showed weakest antioxidant capacity with the IC50 of 5847.73 ± 128.68 μg/mL and FRAP value of 291.4±2.65 μM Trolox equivalent. The antioxidant peptides derived from Tra catfish by-products proteolysate have the potential to be used as natural antioxidant ingredients in pharmaceutical and food industry.

Enzymatic Hydrolysis of Catfish (Pangasius hypophthalmus) By-Product: Kinetic Analysis of Key Process Parameters and Characteristics of the Hydrolysates Obtained

ABSTRACTIn this study, kinetic evaluation of enzymatic hydrolysis of catfish (Pangasius hypophthalmus) by-product meat was conducted. The effects of key factors such as type of proteases (neutrase, papain, and bromelain), enzyme to substrate ratio (E/S), substrate concentration, and extent of hydrolysis on process efficiency, properties and functionalities of hydrolysates were evaluated. The results demonstrated that, for catfish shredded meat, bromelain and papain had higher affinity than neutrase. Kinetics parameters Vm and Km of neutrase, papain, and bromelain were 4.486, 9.060, and 18.249 μM/min and 35.433, 6.582, and 7.034 g/l, respectively. Optimal E/S ratios of neutrase, papain, and bromelain were estimated to be 0.92, 2.76, and 3.31 mg/g. At optimal E/S, the highest possible substrate concentrations were found to be 108.4 g/l for neutrase, 36.2 g/l for papain, and 135.8 g/l for bromelain. Both kinetics study and sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE) analysis showed that bromelain and papain had higher proteolytic activity toward catfish protein than neutrase. A significant increase in antioxidant activity of hydrolysates was observed with neutrase and papain hydrolysate, but not with bromelain. The results could be helpful for industrial processors to develop an efficient process for catfish by-product valorization.

Chemical and nutritional properties of channel and hybrid catfish byproducts.

The objective of this study was to chemically characterize both channel and hybrid catfish parts including heads, frames, viscera, skin, and fillet trimming mince. Triplicate samples of channel and hybrid catfish byproduct parts were obtained from a large commercial catfish processor and analyzed for percent moisture, lipid, protein, ash, and amino acid and fatty acid profiles were determined. The content of the off‐flavor compounds, 2‐methylisoborneol (MIB) and geosmin were also determined. The lipid content of samples were 13.6% and 10.0% for channel and hybrid skins, 17.7% and 21.4% for channel and hybrid viscera, 20.0% and 19.1% for channel and hybrid frames, and 9.7% and 9.3% for channel and hybrid heads. The protein content of samples ranged from a high of 22.8% for channel catfish skins, to a low of 13.4% for channel frames. Low levels of geosmin, <1 ppb, were detected in the byproduct samples, while no MIB was detected. Palmitic, oleic, and linoleic acid comprised approximately 80% of the fatty acids in the byproduct tissues. The amino acid profiles indicated that the catfish mince had high levels of lysine and methionine and other essential amino acids. Results from this study will be used in the development of new value‐added products from catfish byproducts.

Investigation of antioxidant activity of the hydrolysate derived from Tra catfish byproducts using Alcalase® 2.4 L FG for application as a natural antioxidant ingredient

In this study, the effects of temperature, pH, enzyme content, hydrolysis time on antioxidant activity of the hydrolysate from Tra catfish (Pangasiushypophthalmus) by-products with Alcalase® 2.4 L FG were investigated using DPPH• (2,2-diphenyl-1-picrylhydrazyl) radical scavenging method (DPPH• SM) and FRAP (ferric reducing antioxidant potential) method. The chemical composition of the Tra catfish byproducts included 58.5% moisture, 33.88% crude protein, 50.14% crude lipid and 15.83% ash (on dry weight basis). The result of antioxidant activity of the hydrolysate showed that the 50% DPPH• inhibition concentration (IC50) of the hydrolysate reached about 6775 μg/mL which was 1645-fold higher than that of vitamin C and 17-fold higher than that of BHT (Butylated Hydroxytoluene) with the degree of hydrolysis (DH) of the hydrolysate of 14.6% when hydrolysis time was 5h, enzyme/substrate (E/S) ratio was 30 U/g protein, hydrolysis temperature was 550C, and pH was 7.5. The antioxidant potential of hydrolysate using FRAP method reached about 52.12 μMTrolox equivalent which was 53-fold and 18-fold lower than those of vitamin C and BHT, respectively, when the hydrolysis time was 5h, enzyme/substrate ratio was 30 U/g protein, temperature was 500C, and pH level was 8. The result showed that the antioxidant proteolysate derived from Tra catfish by-products has the potential to be used as a natural antioxidant ingredient in nutraceutical and functional food industry.

Refined oil production from patin catfish (Pangasianodon hypophthalmus) by-products

In this study, oil was extracted from the liver and visceral fat of Patin (Pangasianodon hypophthalmus) and refined. The yield of oil after refining was 49.98%. The major yield loss (34.20%) happened during the degumming procedure. Fatty acids found in the crude and refined oil were C12:0, C14:0, C14:1, C16:0, C16:1, C18:0, C18:1, C18:2, C18:3, C18:4, C20:0, C20:1, C20:4, C20:5, and C22:6. The dominant saturated, monounsaturated and polyunsaturated fatty acids were C16:0, C18:1 n-9, and C18:2 n-6, respectively. The total amounts of monounsaturated fatty acids did not change significantly during refining procedure (p>0.05), whereas the total amount of saturated and polyunsaturated fatty acids changed significantly (p < 0.05). The n-3 to n-6 ratios of crude, degummed, neutralized, bleached, and deodorized oils were 1.11, 1.06, 1.05, 1.02, and 1.01, respectively.

Effects of replacing fish meal with ensiled catfish (&lt;i&gt;Pangasius hypophthalmus&lt;/i&gt;) by-products on the performance and carcass quality of finishing pigs

Effects of replacing fish meal with ensiled catfish (&lt;i&gt;Pangasius hypophthalmus&lt;/i&gt;) by-products on the performance and carcass quality of finishing pigs

Digestibility and Nitrogen Balance of Diets that Include Marine Fish Meal, Catfish (Pangasius hypophthalmus) By-product Meal and Silage, and Processing Waste Water in Growing Pigs

Ileal and total tract digestibility and nitrogen (N) balance of diets with four different protein sources were determined in growing pigs. The diets were based on rice bran, broken rice and maize meal and contained Tra catfish by-product (CBP), processed using three different methods, and marine fish meal (FM). The CBP diets consisted of the by-product in meal form, ensiled with molasses, and CBP waste water (WWBD). The four diets were fed to four growing pigs fitted with post-valve T-cecum (PVTC) cannulas in a 4x4 Latin Square design. All experimental diets included Cr 2 O 3 at 5 g/kg feed as an indigestible marker. The ileal apparent digestibility of organic matter and ether extract was higher on diet WWBD than on the other three diets (p 0.05). No significant effects of diet were found on N-retention and N utilization. In conclusion, the catfish by-product meal, ensiled catfish by-product and processing waste water diets and the fish meal diet had similar ileal and total tract apparent digestibility, and similar N utilization in growing pigs.

Effect of Additive on the Chemical Composition of Tra Catfish (Pangasius hypophthalmus) By-product Silages and Their Nutritive Value for Pigs

Two experiments were conducted to determine i) the fermentation characteristics of catfish by-product (C) ensiled with rice bran (RB) or sugarcane molasses (M) in different ratios, and ii) the digestibility of the silages in growing pigs. In the ensiling experiment, there were three ratios of C, ensiled with RB or M, of 8:2, 7:3 and 6:4 (wet basis for C and air-dry basis for RB and M). The six treatments were CRB8:2, CRB7:3, CRB6:4, CM8:2, CM7:3 and CM6:4, with 3 replications per treatment and seven sampling times. The pH of CRB7:3 and CRB6:4 decreased (p<0.05) from the first week and stayed stable until 8 weeks of ensiling, but the pH did not decrease in CRB8:2. The pH of CM8:2, CM7:3 and CM6:4 decreased rapidly from the first week until week 8. Dry matter (DM) and crude protein (CP) contents were slightly lower when catfish by-product was ensiled with RB than with M. Ammonia content in all treatments increased (p<0.05) during ensiling. Lactic acid content in silages with molasses increased from the first week, with the highest value at week 4. However, the lactic acid content in CRB8:2 did not increase with time and had the lowest value of all treatments. Acetic acid proportions of total volatile fatty acids were low at day 0, with the highest value at day 7, decreasing slowly until 8 weeks. The butyric acid proportion was highest at day 0 and decreased up to week 8. The proportion of propionic acid increased during ensiling. The digestibility experiment had a 4x4 Latin-square design and included 4 castrated crossbreed (Yorkshire×Landrace) male pigs fed four diets. The basal diet (BD) included rice bran, broken rice and maize meal, and the other three diets included fish meal (FMD) or catfish by-product ensiled with rice bran (CRBD) or sugarcane molasses (CMD). The silages chosen were those which gave the best results in the ensiling experiment for each additive. The coefficient of total tract apparent digestibility (CTTAD) of DM and organic matter (OM) was not significantly different among treatments. The CTTAD of CP was not different among the silage diets, but was lower in BD (p<0.01). The CTTAD of ether extract (EE) was higher in the catfish by-product silage diets than in FMD and BD. There was no significant difference in the digestibility of DM, OM, CP and EE between the fish meal and the by-product silages. In conclusion, catfish by-product can be successfully preserved by ensiling. Moreover, the total tract apparent digestibility of OM, CP and EE in ensiled catfish by-product was comparable with that of fish meal.

Characterization of Edible Film Fabricated with Channel Catfish (Ictalurus punctatus) Gelatin Extract Using Selected Pretreatment Methods

Farm-raised catfish are important to the economy of the southeastern states in the United States, and catfish processing produces about 55% of by-products for inexpensive sale. Therefore, the utilization of catfish by-products is of great interest to the catfish industry. The objectives of this research were to determine the optimum pretreatment method to extract catfish gelatin for edible film application, and to characterize physical, mechanical, and barrier properties of edible films fabricated with catfish skin gelatin. Catfish skins obtained from a local plant were treated with 6 selected pretreatment methods. The main extraction was performed with deionized water at 50 degrees C after pretreatment. The gelatin yield was calculated and sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE) was performed to characterize molecular weight (MW) profile. Color, tensile strength (TS), elongation, and water barrier property were determined to characterize the fabricated catfish gelatin films. From the results of gelatin yield, color, SDS-PAGE, as well as mechanical and barrier properties of the film, the pretreatment method with 0.25 M NaOH and 0.09 M acetic acid, followed by extraction at 50 degrees C for 3 h, was determined as the optimum extraction method. The catfish gelatin exhibited higher MW fractions than commercial mammalian gelatin. The catfish gelatin extracts possessed film-forming properties determined by TS, elongation, and water vapor permeability (WVP) comparable to those of commercial mammalian gelatin. The selected formula for catfish gelatin film was determined as 1% gelatin and 20% glycerol, resulting in greatest TS and lowest WVP.

Ozone Applications in Catfish Processing

TVA, EPRI, Global Energy Partners, LLC, ClearWater Tech, LLC and Superior Catfish Products (Macon, Mississippi) partnered to conduct research and demonstrate beneficial effects of applying gaseous and aqueous ozone in catfish processing. Utilizing an HDO3-III skid mounted ozone unit manufactured by ClearWater Tech, LLC, various processing areas in the Superior Fish Products catfish processing plant were evaluated in August 2005 to determine if aqueous ozone could reduce the microbial load in the processing line and on finished product. In the offal room, gaseous ozone was introduced to determine if odors could be reduced while catfish by-products were being loaded into trucks also located in the offal room. The utilization of aqueous ozone as a final rinse for processing equipment was also tested. All tests were replicated five times and a completely randomized design was used to statistically analyze resulting data. Standard Laboratories, Inc. of Starkville, MS was contracted to conduct all microbial analyses. It was found that aqueous ozone was very effective in significantly reducing microbial loads on live catfish entering the plant. Finished catfish fillets washed in ozonated water showed significant reductions in total plate counts. Ozonation at the fillet machine could be beneficial. Utilizing aqueous ozone as a final wash after using soap and a chlorine sanitizer was of no benefit and actually removed the residual chlorine and led to increased plate counts. Gaseous ozone reduced odors in the offal room rapidly and effectively. Utilization of ozone for odor reductions will require ozone monitoring equipment that ensures employee safety.