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Fortification of queso blanco (QB) with flaxseed oil (FO) containing omega-3 polyunsaturated fatty acids may provide a functional food with health benefits such as improved cell, brain, and retina functionality, and protection against cardiovascular and immune-inflammatory diseases. However, QB experiences a short shelf life because of the early development of yeasts and molds and addition of FO may increase susceptibility to lipid oxidation. Oregano essential oil (OEO) is known for its antimicrobial and antioxidant properties, but due to its intense flavor compounds it may not be suitable for direct incorporation into QB. Thus, incorporation of OEO into an edible film prepared with whey protein isolate (WPI) may improve the shelf life of QB. Scanning electron microscopy (SEM) micrographs revealed that FO was successfully retained by the cheese after homogenization. The thiobarbituric-acid-reactive-substances (TBARS) and yeast and mold counts (YMC) of the wrapped cheeses were analyzed during 60 d of refrigerated storage. The oxidation rate increased significantly for nonwrapped QB containing FO (QBFO) during storage, however wrapping with WPI edible films containing OEO (WOF) significantly limited lipid oxidation and prevented growth of yeasts and molds. This study demonstrated the antioxidant and antimicrobial properties of WOF for preservation of QBFO during refrigerated storage.

The quality of biodiesel from crude pollock oil and the effect of a purification process on the physicochemical properties of pollock oil biodiesel were evaluated. Unpurified pollock oil (PO) was transesterified to biodiesel from pollock oil (BPO) using methyl alcohol (1:6 molar ratio) and NaOH (1 % w/w of the oil weight); and the resulting fatty acids methyl esters (FAME) were purified with 10 % (w/w) activated earth to yield purified biodiesel from pollock oil (PBPO). The samples were evaluated for yield, FAME composition, free fatty acids (FFA), peroxides value (PV), moisture, bulk density, cloud point, flash point, free and total glycerin, color, rheological properties, and minerals. BPO and PBPO were evaluated for the kinetics of lipid oxidation. The transesterification and purification processes had no effect on the FAME composition of PO. The yield of PBPO was significantly (P < 0.05) reduced after the transesterification and purification processes. Moreover, the transesterification process significantly (P < 0.05) reduced the FFA, moisture, bulk density, flash point, total glycerides, redness, viscosity, arsenic and silicon content in PO. Meanwhile, the purification process significantly (P < 0.05) reduced the PV, redness, and sulfur content of BPO. The flash point of BPO was significantly (P < 0.05) increased by the purification process from 79 to 84 °C. PO, BPO, and PBPO behaved as non-Newtonian and Newtonian fluids at 0 and 25 °C, respectively. BPO showed a lower oxidation rate and activation energy compared to those of PBPO. BPO and PBPO met the ASTM biodiesel standard D6751 for moisture, bulk density, cloud point, free and total glycerin, Na, P, and S. The study demonstrated that high viscosity crude pollock oil could be converted into low viscosity purified pollock oil biodiesel.

Unpurified red salmon oil (UPSO) was processed to obtain purified salmon oil (PSO) by chitosan adsorption. Both unpurified and purified oils were evaluated for peroxide value (PV), free fatty acids (FFA), fatty acid methyl esters (FAME), moisture, and color. An emulsion system containing PSO (EPSO) was prepared; the system was analyzed for color, rheological properties and microstructure before spray drying to produce microencapsulated PSO (MPSO). MPSO was analyzed for moisture, water activity, bulk density, color and FAME composition. PSO or MPSO was added to a commercial baby-food product (CB) and all baby-food samples were compared for PV, FFAs, FAME, and color. Experiments were completed in triplicate and data statistically analyzed (α = 0.05). PSO had higher percentages of total omega-3, total monounsaturated DHA, and EPA than MPSO. EPSO exhibited viscoelastic characteristic and the droplet size of EPSO was 1–9 μm. Total omega-3 and total monounsaturated contents of the MPSO were lower than PSO. All baby-food samples with added fish oils had similar color. DHA and EPA contents of baby food were increased over three fold by the addition of PSO and/or MPSO. MPSO can be added to CB resulting in increasing total percent omega-3 fatty acids while maintaining desirable attributes of the CB.

The following four methods were used to extract salmon oil from red salmon heads: RS1 involved a mixture of ground red salmon heads and water, no heat treatment, and centrifugation; RS2 involved ground red salmon heads (no water added), heat treatment, and cen- trifugation; RS3 involved a mixture of ground red salmon heads and water, heat treatment, and centrifugation; and RS4 involved ground red salmon heads, enzymatic hydrolysis, enzyme inactivation by heat and centrifugation. The four extracted oil samples were evaluated for chemi- cal, thermal, and rheological physical properties. The RS4 process recovered significantly higher amounts of crude oil from red salmon heads than the other three extraction methods, while containing a higher % of free fatty acids and higher peroxide values than RS1, RS2, and RS3 oils. Oleic acid, eicosenoic acid, EPA, and DHA were the pre- dominant fatty acids accounting for about 60% of all unsaturated fatty acids. The RS1, RS2, RS3, and RS4 extractions contained 9.3, 9.05, 9.35, and 9.45% of EPA and 8.8, 8.55, 9.0, and 9.1% of DHA in the oil, respec- tively. Weight losses of the oils increased with increasing temperatures between 200 and 500 C. The % weight losses at 500 C were 94.50, 94.58, 94.94, and 95.47% for RS2, RS1, RS3, and RS4, respectively. The apparent vis- cosities of all the oil samples decreased with the increases in the temperature. The RS1 extract was more viscous (P \ 0.05) than those of RS2, RS3, and RS4 between 0 and 25 C.

This study demonstrated the feasibility of producing soluble protein (CFSP) and insoluble protein (CFISP) fractions from catfish muscle protein. CFSP and CFISP contained 60.6% and 73.8% protein and 8.6% and 20.3% fat, respectively. Both CFSP and CFISP contained essential amino acids. Differences were observed between physicochemical properties of the 2 protein fractions, including nitrogen solubility, emulsion stability, and fat adsorption capacity. The flow and viscoelastic properties of the emulsions prepared with CFSP and CFISP were investigated using a rheometer. The power law model and the Casson model were used to determine the flow behavior index (n), consistency index (K), and yield stress. Emulsion containing CFSP (ECFSP) had a higher K value than emulsion containing CFISP (ECFISP). Both ECFSP and ECFISP emulsions exhibited pseudoplastic behavior and viscoelastic characteristics. The G′ (an elastic or storage modulus) and G″ (a viscous or loss modulus) values for ECFSP were higher than ECFISP. Catfish muscle tissue can be easily separated into soluble and insoluble protein powders that have desirable functional properties.

Unrefined menhaden oil was evaluated for thermal and rheological properties and its temperature-dependent viscosity and lipid oxidation rate were determined. Peroxide value, free fatty acids, density, specific gravity, water activity, moisture content, and enthalpy of the unrefined menhaden oil were 5.70 meq/kg, 3.80%, 0.93 g/mL, 0.93%, 0.52%, 0.15%, and 20.2 kJ/kg, respectively. The melting point range of unrefined menhaden oil was found to be -69.5 to 27.21 degrees C. The menhaden oil exhibited non-Newtonian fluid behavior at lower temperatures (5 to 25 degrees C), while it behaved like a Newtonian fluid at 30 degrees C. The oil apparent viscosity at 5 degrees C (0.22 Pa.s) was significantly higher (P < 0.05) than that at 30 degrees C (0.033 Pa.s). The average magnitude of activation energy for viscosity of the unrefined menhaden oil was 50.37 kJ/mol. The predicted apparent viscosity agreed (R(2)= 0.9837) satisfactorily with the experimental apparent viscosity. The minimal lipid oxidation rate of the oil was found at 25 and 35 degrees C for 6 h, higher lipid oxidation rates were observed when the oil was heated for 6 h at 45 to 85 degrees C. The rate of lipid oxidation for unrefined menhaden oil was temperature dependent (R(2)= 0.9425). This study showed that the magnitude of the apparent viscosity and oxidation rate of the unrefined menhaden oil was greatly influenced by temperature.

Catfish skin is an abundant and underutilized resource that can be used as a unique protein source to make fish skin protein hydrolysates. The objectives of this study were to isolate soluble and insoluble proteins from hydrolyzed catfish skin, study the rheological and functional properties of the protein hydrolysates, and evaluate the properties of emulsions made from the protein powders. Freeze-dried catfish skin soluble (CSSH) and insoluble hydrolysate (CSISH) powders were analyzed for proximate analysis, emulsion stability, fat absorption, amino acids, color, and rheological properties. CSSH had significantly (P < 0.05) higher protein, ash, and moisture content but lower fat content than that of CSISH. The yield of CSSH (21.5%+/- 2.2%) was higher than that of CSISH (3%+/- 0.3%). CSISH had higher emulsion stability than CSSH. CSSH was light yellow in color and CSISH was darker. The mean flow index values for emulsion containing CSSH (ECSSH) and CSISH (ECSISH) were both less than 1, indicating that they were both pseudoplastic fluid. The G' and G'' values for the ECSISH were higher than that of ECSSH, indicating that the viscoelastic characteristic of the emulsion containing CSISH was greater than that of the emulsion containing CSSH. The study demonstrated the CSSH and CSISH had good functional and rheological properties. They have potential uses as functional food ingredients.

Selected quality characteristics of fresh-cut sweet potatoes (FCSP) coated with chitosan were evaluated during 17-d refrigerated storage. The FCSP cubes were coated with a solution (1%, w/v) of chitosan having 470 or 1110 kDa. Color (L*, a*, b*) values of uncoated and chitosan-coated FCSP during storage were generally affected by storage time as well as coating treatments (P < 0.05). No significant changes in color lightness (L*) of 470 kDa-coated FCSP were observed during the 17-d storage. During days 3 to 17, 470 kDa-coated FCSP had significantly higher redness (a*) and yellowness (b*) values than did uncoated and 1110 kDa-coated FCSP. Texture firmness of uncoated and chitosan-coated FCSP exhibited minimal changes during the 17-d storage. Although actual weight loss values (%) of uncoated and chitosan-coated FCSP were not significantly different at day 17, the weight loss difference (%) between day 3 and day 17 for uncoated FCSP (3.02%) was slightly higher compared to those (2.24% to 2.26%) of chitosan-coated FCSP. The initial total aerobic count was 4.7 log(10) CFU/g which then gradually increased to 8.54 and 9.67 log(10) CFU/g after 17 d of storage for 470 kDa-coated and uncoated FCSP, respectively. After day 6, the total aerobic counts of uncoated FCSP were higher than those of 470 kDa-coated FCSP. The yeast and mold count of chitosan-coated FCSP was about 2.5 log(10) CFU/g at day 17. Overall, consumers could not differentiate between 470 kDa-coated FCSP at day 17 and uncoated FCSP at day 0.

Changes in melting points, enthalpy, and specific heat capacity of catfish visceral oil at each step of the purification process were studied. Melting points of −46.2 to 21.2 °C for crude oil, −45.9 to 11.5 °C for degummed oil, −44.3 to 11.4 °C for neutralized oil, −47.1 to 9.9 °C for bleached oil and −52.3 to 8.0 °C for deodorized oil were observed. Enthalpy (kJ/kg) was 74.1 for crude oil, 74.7 for degummed oil, 75.1 for neutralized oil, 79.3 for bleached oil, and 84.3 for deodorized oil. The specific heat capacities at 20 °C for crude, degummed, neutralized, bleached, and deodorized oils were 1.69, 1.96, 1.97, 1.91, and 1.83 kJ/kg °C, respectively.

There are good markets for mature pollock roe; however, immature pollock roe is underutilized. The physical and nutritional properties of immature pollock roe (IPR) have not been reported, which limits its potential use as a food ingredient. The objective of this study was to evaluate the physical and nutritional properties of immature pollock roe and soluble and insoluble protein powders made from the immature roe. IPR samples were obtained during the spring pollock harvest from a seafood processing plant in Kodiak, Alaska. Soluble (SP) and insoluble protein (IP) fractions were produced by heating IPR, separating by centrifugation and freeze drying. The protein contents of freeze-dried IPR, SP, and IP were 81.7%, 63.2%, and 83.0%, respectively. The amino acid contents of IPR and IP were similar except for isoleucine and valine. However, the amino acid contents of IPR and IP were different from values for SP. Lipid contents of IPR, SP, and IP were 9.2%, 9.3%, and 11.1%, respectively. Palmitic acid (C16:0; 21.2%), DHA (C22:6omega3; 21.2%), and EPA (C20:5omega3; 19.0%) were the 3 most abundant fatty acids in fresh IPR. Fat adsorption capacity value for SP was significantly higher than IPR and IP (P < 0.05). SDS electrophoresis indicated a major protein band with molecular weight of 103 KDa in all samples. Results indicate that IPR can be utilized to make a number of unique food ingredients with good nutritional characteristics and functional properties.

Effects of chitosan extraction processes and solvent types on sorption behavior of unplasticized crawfish chitosan films were investigated. Four different chitosans prepared from crawfish shell were dissolved in 1% v/v acetic, formic, lactic, or malic acids at 1% w/v concentration. Chitosans dissolved in acetic or formic acid formed flexible and transparent films that are desirable for packaging applications. Chitosan acetate films maintained lower moisture contents at any relative humidity level compared with chitosan formate films. The type of chitosan significantly influenced the sorption isotherms of chitosan formate films but not chitosan acetate films. The Guggenheim-Anderson-de Boer, Oswin, and Caurie models (R2= 0.98, 0.95, and 0.95, respectively) could be used to predict sorption behavior of crawfish chitosan acetate and formate films.

The effects of different proteolytic enzymes and different reaction durations (25, 50, 75 min) on functional and nutritional properties of red (sockeye) salmon head hydrolysates were evaluated. Degree of hydrolysis values for the 75-min digestion ranged from 6.4% to 16.7%. Oil yield (4.9% to 10.6 %) from red salmon heads was affected by the enzyme used. Protein hydrolysate powders were yellowish and contained 62.3% to 64.8% protein with high levels of essential amino acids. Increased degree of hydrolysis values were weakly correlated with increased hydrolysate solubility. Maximum emulsion stability and fat adsorption were observed for the dried hydrolysate generated in the 25-min reaction time. Water adsorption of hydrolysate powders ranged from 1.0 mL to 3.3 mL water/g dried hydrolysate.

Summary Soluble protein powders were produced from pollock by-products and evaluated for their functional, nutritional and rheological properties. Soluble protein powders were made from pollock viscera (PVSP), viscera without liver (PVWLSP), heads (PHSP), frames (PFSP), trimmings (PTSP), and liver (PLSP) and had protein contents ranging from 65.0% to 78.9%. Yield of PVWLSP was higher than that of other pollock proteins powder and PTSP had the highest nitrogen solubility value (85.7%). Emulsion capacity and emulsion stability of the pollock protein powders ranged from 29% to 34.5% (mL of oil per 200 mg of protein) and 65.3% to 77.6%, respectively. Highest and lowest fat adsorption values were observed for PFSP (10.6 mL of oil per gram of protein) and PVSP (4.1 mL of oil per gram of protein), respectively. Fish protein powder samples were good sources in K, P, and Mg and amino acids. Emulsions made with pollock soluble protein powders exhibited viscoelastic characteristics.

The effects of chitosan (CH1 = 1% and CH2 = 2% solution), egg albumin (EA), soy protein concentrate (SPC), pink salmon protein powder (PSP), and arrowtooth flounder protein powder (AFP) as edible coatings on quality of skinless pink salmon fillets were evaluated during 3 mo frozen storage. Coating with 2% chitosan (CH2) resulted in significantly higher yield than coating with PSP and AFP. The thaw yield of salmon fillets coated with CH2 was higher than those of the control and fillets coated with AFP. The noncoated, CH1-, and CH2-coated fillets had similar drip loss (0.4% to 1.2%), which was lower than those observed for PSP- and AFP-coated fillets. All fillet samples had similar cook yield (84.2% to 88.8%). The fillet coated with CH1, CH2, SPC, and EA had significantly higher (P 0.05) effects of coating on a*, b*, and whiteness values for cooked fillets after 3 mo frozen storage.

Arrowtooth flounder soluble protein powder (AFSP) and arrowtooth flounder insoluble protein powder (AFISP) were evaluated for their functional, nutritional, and rheological properties. AFSP and AFISP contained 80% and 79% protein and 5.9% and 14.9% fat, respectively. Yield of AFSP (8.6%) was less than AFISP (13.1%). AFSP and AFISP had desirable essential amino acid and mineral contents. Emulsion stability of AFSP was greater than AFISP. Fat and water absorptions (mL/g protein) were 5.2 and 1.8 for AFSP, respectively, and 3.3 and 4.2 for AFISP Mayonnaises made from AFSP had greater emulsion stability than mayonnaise made from AFISP. Mayonnaises from both AFSP and AFISP possessed pseudoplastic and viscoelastic characteristics.

Thermal and flow properties of unrefined oils from the heads of red or pink salmon were evaluated. Major thermal degradation of the salmon oils occurred between 200 and 450°C. Red and pink salmon oils were completely decomposed at 533 and 668°C, respectively. The phase transition of salmon oils occurred over a wide range of temperatures. The melting points of −69.6 to −0.36°C and −64.7 to 20.8°C were observed for red and pink salmon oils, respectively. The enthalpy was 40 j/g for red salmon oil and 39 j/g for pink salmon oil. Specific heat capacity ranges of 0.8 to 1.6 and 1.3 to 2.3 j/g/°C were observed for red and pink salmon oils, respectively. Both salmon oils exhibited Newtonian flow behavior. Red salmon oil required higher magnitudes of energy (kj·mol−1) to flow than pink salmon oil. The viscosity of salmon oils was temperature-dependent and could be predicted by the Arrhenius equation.

The feasibility of using chitosan, activated carbon, and activated earth to remove FFA from crude catfish visceral oil, and the adsorption kinetics of the procedure were evaluated. The effect of adsorbents on water activity and the 18∶3 and 22∶6 content of crude catfish visceral oil was also studied. The initial adsorption kinetic coefficients of FFA (mL g−1 min−1) were 0.1, 0.07, and 0.03 for chitosan, activated carbon, and activated earth, respectively. The external film mass-transfer coefficient (0.001 mL s−1) was similar for the three adsorbents. The adsorption capacity of FFA at saturation (mg g−1) was 71.2 for chitosan, 65.5 for activated carbon, and 57.0 for activated earth. The intraparticular diffusion coefficients (mg mL−1 min−0.05) were 0.14, 0.12, and 0.09 for chitosan, activated carbon, and activated earth, respectively. Water activity of the crude oil decreased with increased contact time of the adsorbents. Results indicated that chitosan was a better adsorbent than activated carbon and activated earth for FFA removal from crude catfish visceral oil.

The thermal degradation (weight loss) of individual FA and of catfish and menhaden oils collected from different refining steps was investigated by thermogravimetric analysis. The heat resistance of FA was partially dependent on chain length and degree of unsaturation. The weight loss of catfish and menhaden oils increased with increased heating temperatures, regardless of the oil refining process. All oil samples (except crude catfish oil) were decomposed after the heating temperature reached 550°C. Based on the thermogravimetric curves, the following thermal stability sequence at different refining steps for both catfish and menhaden oils was proposed: crude > degummed > neutralized > bleached > deodorized oils.

The functional, nutritional, and antioxidative properties of hydrolyzed herring and herring byproducts (head and gonad) were evaluated. All freeze-dried herring fish protein hydrolysate (FPH) powders were light yellow and contained 77% to 87% protein, The degree of hydrolysis was 18.3%, 13%, 13%, and 10.1%, respes. tively, for head, whole fish, body, and gonad after 75 min digestion. All FPH powders had desirable essential amino acid profiles and mineral contents. The emulsilying capacity and stahility of all FPH powders were lower than those of egg alhumin and soy protein; the fat adsorption was comparable to that of egg albumin. The antioxidative acitvity of whole herring FPH was bighest, followed by that of body,. gonad, and head.

Effects of oil refining steps (degumming, neutralizing, bleaching, and deodorizing) on rheological properties of catfish oil were investigated. Four rheological models (Newtonian, Bingham, Herschel-Bulkley, and Casson) were used to fit the experimental data. Refined catfish oil behaves like a Newtonian fluid. Based on the Casson model, the yield stress values of oils gradually decreased after each refining step. The highest shear rate index (0.904) was observed in the deodorized oil. The Casson model was used to predict rheological properties because it works well at both lower and higher shear rates.

Oil was extracted from catfish viscera and purified (degummed, neutralized, bleached, and deodorized). The yield of catfish oil after purification was 65.7%. The major yield loss took place during the degumming process. The FA found in crude catfish visceral oil were 14∶0, 16∶0, 16∶1, 18∶0, 18∶1, 18∶2, 18∶3, 20∶0, 20∶1, 20∶2, 20∶3, 20∶4, and 22∶6, the predominant FA being 18∶1, 16∶0, 18∶2, and 18∶0. The total unsaturated FA in the purified catfish oil amounted to 67.7%. The combined n−3 FA content of the purified catfish oil was 4.6 mg/g of oil. The purified catfish oil contained 1.21 mg/g DHA. FFA, water activity, and some mineral contents decreased during purification. Bleaching removed pigments, thus resulting in oil with greater lightness and less yellowness.

FA profiles of catfish liver oils were analyzed after microwave-assisted (without solvent extraction) and/or conventional (with solvent extraction) preparation methods. Microwave heating of the smaples was performed at 100, 80, 60, or 40% power at 1,000 W and 2,450 MHz, each for 80, 60, 40, or 20 s. Significant differences in the content of recovered FA were observed among the microwave-heated samples, except for C20∶0 and C20∶4. Recovery of C16∶0, C20∶0, and C20∶4 from the samples analyzed by the microwave-assisted method was lower than that of the samples analyzed by the conventional method. Much greater recovery was observed for C18∶1, C18∶2, and C22∶6; however, the recovery was not different from or was only slightly lower than that of the conventional method when microwave heating was set at 40% power for 20 s. This was also observed for the total unsaturated or saturated FA. Compared to other microwave treatments, heating at 100% power for 80 s yielded the greatest recovery of C14∶0, C18∶0, C18∶1, C18∶2, C18∶3, C20∶1, C20∶2, and C22∶6.

The FA composition of crude catfish oil recovered from whole viscera, digestive tract, liver, gallbladder, and visceral storage fat was determined and compared with that of fillet and nugget (abdominal portion). About 34% crude fat (wet basis) could be recovered from the whole catfish viscera. FA found in crude catfish visceral oil were C14∶0, C16∶0, C16∶1, C18∶0, C18∶1, C18∶2, C18∶3, C20∶0, C20∶1, C20∶2, C20∶3, C20∶4, and C22∶6, the predominant FA being C18∶1, C16∶0, C18∶2, and C18∶0. Catfish visceral oil was characterized by a high level of unsaturated FA, which was similarly found in fillet and nugget. Total unsaturated FA in visceral oil amounted to 261.3 mg/g (dry basis) compared to that of fillet (259.3 mg/g) and nugget, (307.6 mg/g). The whole viscera contained 4.2 mg/g DHA compared to that of gallbladder (9.2 mg/g), fillet (9.3 mg/g), and nugget, (10.7 mg/g). The total n−3 FA in the whole and/or portioned visceral ranged from 4.3 to 20.9 mg/g.