Kristen E. Matak

Chemical properties of surimi seafood nutrified with ω-3 rich oils

Surimi-based seafood products are widely accepted and enjoyed worldwide. The US consumption increased in 1980s; however, it leveled thereafter. Food products nutrified with ω-3 polyunsaturated fatty acids (PUFAs) are in increasing demand due to demonstrated health benefits. Currently, surimi seafood is not nutrified with ω-3 PUFAs. In the present study, surimi seafood was nutritionally-enhanced with ω-3 PUFAs-rich oils (flaxseed, algae, menhaden, krill, and blend). The objectives were (1) chemical characterization of FA composition and oxidation, and (2) determination of physicochemical properties (colour and texture) of the nutritionally-enhanced surimi seafood. Oil addition resulted in increased (P<0.05) concentration of total ω-3 FAs in surimi seafood; however, the concentration of α-linolenic (ALA, 18:3ω-3), eicosapentaenoic (EPA, 20:5ω-3) and docosahexaenoic (DHA, 22:6ω-3) acids depended on which oil was added. Although the ω-3 PUFAs nutrification resulted in increased (P<0.05) susceptibility of surimi seafood to lipid oxidation, it was within ranges acceptable to consumers. Texture analysis (texture profile analysis, Kramer shear and torsion test) showed that ω-3 PUFAs nutrification did not affect texture. Colour properties of ω-3 PUFAs nutrified surimi seafood were generally improved except when krill oil or blend was added. This study demonstrates that nutritional value of surimi seafood can be enhanced with concurrent improvement of colour and without affecting texture.

Isoelectric Solubilization/Precipitation as a Means To Recover Protein Isolate from Striped Bass (Morone saxatilis) and Its Physicochemical Properties in a Nutraceutical Seafood Product

Excessive dietary intake of Na (i.e., NaCl) contributes to hypertension, which is a major risk factor for cardiovascular disease. Normally, NaOH and HCl are used to dissolve and precipitate, respectively, fish muscle proteins in isoelectric solubilization/precipitation (ISP), therefore contributing to increased Na content in the recovered fish protein isolates (FPI). Substitution of NaOH with KOH may decrease the Na content in FPI and, thus, allow development of reduced-Na seafood products. In this study, FPI was recovered with ISP using NaOH or KOH. In order to develop a nutraceutical seafood product, the FPI was extracted with NaCl or KCl-based salt substitute and subjected to cold- or heat-gelation. In addition, standard nutraceutical additives (ω-3 fatty acids-rich oil and dietary fiber) along with titanium dioxide (TiO2) were added to FPI. Color, texture, dynamic rheology, Na and K content, and lipid oxidation of the FPI gels were compared to commercial Alaska pollock surimi gels. FPI gels had greater (p < 0.05) whiteness, good color properties (L*a*b*), and generally better textural properties when compared to surimi gels. Although the ISP-recovered FPI and surimi developed similar final gel elasticity, the proteins in FPI and surimi had different gelation pattern. A reduction (p < 0.05) of Na content and simultaneous increase (p < 0.05) in K content of FPI gels was achieved by the substitution of NaOH with KOH during ISP and NaCl with the KCl-based salt substitute during formulation of the FPI paste. Although cooking and addition of NaCl during formulation of the FPI paste increased (p < 0.05) lipid oxidation in FPI gels, TBARS values were much below rancidity levels. These results indicate that KOH can replace NaOH to recover FPI from whole gutted fish for subsequent development of nutraceutical seafood products tailored for reduction of diet-driven cardiovascular disease.

Survival of Listeria innocua after isoelectric solubilization and precipitation of fish protein.

Protein wasted by the disposal of fish processing by-products may be recovered using isoelectric solubilization and precipitation. Extreme pH shifts are used to solubilize the protein and then it is recovered by precipitation and centrifugation. Microbial survival after this process is unknown; therefore, the purpose was to see if Listeria innocua would survive extreme pH shifts during the protein recovery process. Fresh rainbow trout fillets were inoculated with L. innocua, homogenized, and brought to the target pH of 2, 3, 11.5, or 12.5 by the addition of concentrated hydrochloric acid or sodium hydroxide. The proteins were allowed to solubilize at 4 degrees C for 10 min, centrifuged, and the lipid and insoluble components (bones, skin, insoluble protein, and so on) were removed. A 2nd pH shift (pH 5.5) and centrifugation was used to separate the precipitating protein and water fractions. Each constituent (lipid, protein, water, insoluble components) was analyzed for bacterial content using growth and selective media. The sums of the surviving L. innocua in these constituents were compared to the initial inoculum. There were no significant differences in recovery on growth or selective media (P > 0.05). The greatest loss occurred when the pH was shifted to 2, with a 3.1-log reduction in the combined fractions of the trout fillets and a 3.8-log reduction in the protein fraction. There were no significant losses when the pH was adjusted to 11.5 (P > 0.05). Future studies will continue to look at the effects of using organic acid, rather than inorganic, for protein solubilization.

Physicochemical properties of surimi gels fortified with dietary fiber

Although dietary fiber provides health benefits, most Western populations have insufficient intake. Surimi seafood is not currently fortified with dietary fiber, nor have the effects of fiber fortification on physicochemical properties of surimi been thoroughly studied. In the present study, Alaska pollock surimi was fortified with 0-8 g/100 g of long-chain powdered cellulose as a source of dietary fiber. The protein/water concentrations in surimi were kept constant by adding an inert filler, silicon dioxide in inverse concentrations to the fiber fortification. Fiber-fortified surimi gels were set at 90 °C. The objectives were to determine (1) textural and colour properties; (2) heat-induced gelation (dynamic rheology); and (3) protein endothermic transitions (differential scanning calorimetry) of surimi formulated with constant protein/water, but variable fiber content. Fiber fortification up to 6 g/100 g improved (P<0.05) texture and colour although some decline occurred with 8 g/100g of fiber. Dynamic rheology correlated with texture and showed large increase in gel elasticity, indicating enhanced thermal gelation of surimi. Differential scanning calorimetry showed that fiber fortification did not interfere with thermal transitions of surimi myosin and actin. Long-chain fiber probably traps water physically, which is stabilized by chemical bonding with protein within surimi gel matrix. Based on the present study, it is suggested that the fiber-protein interaction is mediated by water and is physicochemical in nature.

The effect of a flaxseed oil-enhanced diet on the product quality of farmed brook trout (Salvelinus fontinalis) fillets.

The effects of dietary modification with flaxseed oil-enhanced (Flax) feed on the product quality of brook trout fillets were examined. Trout were fed a commercial feed supplemented with fish oil (CD) or flaxseed oil (Flax) for 165 d before harvesting. Proximate composition and fatty acid profile were determined on fillets. Quality parameters of the raw fillets were examined over the storage period by measuring color (L*, a*, b*), muscle pH, and thiobarbituric acid reactive substances test. Evaluations on the cooked fillets included sensory evaluation with triangle tests and a paired preference test. There were no differences in proximate composition between the groups; however, the total omega-3 fatty acids were greater in Flax fillets (P<0.05). Diet and day were shown to interact in their effect on whiteness, pH, and lipid oxidation (P<0.05); however, linear regression did not determine that malondialdehyde concentration was associated with time in either diet type implying that lipid oxidation in the vacuum-packed fish was controlled at storage temperatures (4°C). Sensory panelists were able to choose the odd sample in a replicated triangle test analyzed using the β-binomial model, and there was preference for Flax fillets (P<0.05). Results indicate that a Flax-enhanced diet would have favorable effects on product quality of farmed brook trout.

Chemical properties of ω-3 fortified gels made of protein isolate recovered with isoelectric solubilisation/precipitation from whole fish

Protein isolate was recovered from whole gutted fish using isoelectric solubilisation/precipitation (ISP). The objective was to determine chemical properties of heat-set gels made of the ISP protein isolate fortified with ω-3 polyunsaturated fatty acids (PUFAs)-rich oils (flaxseed, fish, algae, krill, and blend). The extent of the PUFAs increase, ω-6/ω-3 FAs and unsaturated/saturated FAs ratios, and the indices of thrombogenicity and atherogenicity depended on specific ω-3 PUFAs-rich oil used to fortify protein isolate gels. Lipid oxidation in ω-3 PUFAs fortified gels was minimal, although greater (P<0.05) than control gels (without ω-3 PUFAs fortification). However, all gels were in the slightly rancid, but acceptable range. The commonly used thiobarbituric-acid-reactive-substances (TBARS) assay to determine lipid oxidation in seafood may be inaccurate for samples containing krill oil due to its red pigment, astaxanthin. Protein degradation (total-volatile-basic-nitrogen) was greater (P<0.05) in ω-3 PUFAs fortified gels than control gels. However, all gels were considerably below the acceptability threshold for protein degradation. The shear stress of ω-3 PUFAs fortified gels was generally greater than the control gels and the shear strain was generally unchanged. This study demonstrates that ω-3 PUFAs fortification of protein isolates recovered with ISP from fish processing by-products or whole fish has potential application in the development of functional foods.

Recovery of Salmonella enterica Serovars Typhimurium and Tennessee in Peanut Butter after Electron Beam Exposure

UNLABELLED The effect of electron beam (e-beam) radiation on the recovery of Salmonella serotypes Tennessee (ATCC 10722) and Typhimurium (ATCC 14028) in creamy peanut butter over a 14-d storage period at 22 °C was studied. Each Salmonella type was independently inoculated into peanut butter and subjected to e-beam doses that ranged from 0 to 3.1 kGy, confirmed by film dosimetry. After 2-, 4-, 6-, 8-, and 14-d of storage, microbial analyses were conducted. Survivors were recovered on growth and selective media using standard spread-plating methods. Microbial counts (CFU/g) were log-converted and differences were determined by ANOVA and Tukeys Honestly Significant Differences test. When samples were not e-beam-treated, there were no significant changes (P > 0.05) in microbial numbers over time. In e-beamed samples, microbial numbers decreased over time; however, reductions were not always significant. Initial recovery rates (R-rates) 2 d after e-beam treatment were significantly different for the 2 strains of Salmonella and between recovery media (P < 0.05); however, these differences did not persist for the remainder of the storage period (P > 0.05) indicating that injured cells were not able to survive in the high-fat, low-water activity peanut butter environment. R-rates for both strains of Salmonella were maintained until day 14 when there were significant reductions in Salmonella Typhimurium (P < 0.05). These results indicate that Salmonella Tennessee and Salmonella Typhimurium will survive in peanut butter when exposed to nonlethal doses of e-beam irradiation. PRACTICAL APPLICATION Electron beam (e-beam) irradiation is an alternative to thermal processing; this technique inactivates microorganisms and insects that might be present in a food by generating radiation by accelerated electrons that inactivate organisms directly because of interaction with cell components and indirectly by producing free radicals that disrupt integrity of the cell membrane. E-beam radiation will reduce the number of probable microbiological hazards that could be present while the food remains generally unaffected in texture, taste, and nutritional value. A recent study showed e-beam irradiation to be effective at reducing both Salmonella Tennessee and Typhimurium in peanut butter by one log after exposure to less than 1 kGy, highlighting the need to explore this process further.

Compositional Characteristics of Materials Recovered from Headed Gutted Silver Carp (Hypophthalmichthys molitrix) by Isoelectric Solubilization and Precipitation Using Organic Acids

UNLABELLED Protein was recovered from headed gutted silver carp by isoelectric solubilization at pH 2.5, 3.0, 11.5, or 12.0 and precipitation (ISP) at pH 5.5 using acetic (AA) or a 30% formic and lactic acid combination (F&L) and 10 N sodium hydroxide. Total protein and fat recovery yields, proximate composition and mineral analyses of fractions were determined. Protein and lipid recovery yields when solubilized under basic conditions were comparable to yields reported from other studies using hydrochloric acid; however, the recovered fractions were less pure. Processing at basic pH using AA was more effective than F&L at removing impurities (P < 0.05) from the recovered protein fraction and impurities were effectively removed from recovered lipids regardless of processing pH or acid type (P > 0.05). For the most part, sodium was greater (P < 0.05) and there was less calcium, phosphorus, magnesium, and iron (P < 0.05) in the recovered protein regardless of acid used when compared to the initial paste. This research shows that organic acids have the potential to recover protein and lipid by ISP processing. PRACTICAL APPLICATION This research presents a reliable method for extracting nutritionally valuable fish protein and oils from otherwise hard to process fish and its byproducts. Replacing the traditionally used strong acids with organic acids might further accomplish bacterial load reduction while resulting in similar to or improved protein recovery yields. Therefore, this technology may increase the commercial viability of hard to process fish.

pH shift protein recovery with organic acids on texture and color of cooked gels

BACKGROUND Isoelectric solubilization and precipitation (ISP) processing uses pH shifts to separate protein from fish frames, which may increase commercial interest for silver carp. Texture and color properties of gels made from silver carp protein recovered at different pH strategies and organic acid types were compared. ISP was applied to headed gutted silver carp using 10 mol L(-1) sodium hydroxide (NaOH) and either glacial acetic acid (AA) or a (1:1) formic and lactic acid combination (F&L). Protein gels were made with recovered protein and standard functional additives. RESULTS Texture profile analysis and the Kramer shear test showed that protein gels made from protein solubilized at basic pH values were firmer, harder, more cohesive, gummier and chewier (P < 0.05) than proteins solubilized under acidic conditions. Acidic solubilization led to whiter (P < 0.05) gels, and using F&L during ISP yielded whiter gels under all treatments (P < 0.05). CONCLUSION Gels made from ISP-recovered silver carp protein using organic acids show potential for use as a functional ingredient in restructured foods.

Effect of electron beam on chemical changes of nutrients in infant formula

Infant milk formula has recently been implicated as a transmission vehicle for an emerging foodborne pathogen, Enterobacter sakazakii, resulting in high mortality rates. Electron beam (e-beam) efficiently and non-thermally inactivates foodborne pathogens, including E. sakazakii, in infant milk formula. However, the effects of e-beam on chemical changes of nutrients in infant formula have not been determined. Therefore, the objective of this study was to fulfill this gap. Dehydrated infant milk formula was processed with e-beam at 0 (control) to 25 kGy. Amino acid, fatty acid, and mineral profiles (AAP, FAP, and MP, respectively), as well as protein degradation and lipid oxidation, were determined. There were no differences (P>0.05) in FAP, AAP, and MP. SDS-PAGE electrophoresis qualitatively detected three major protein bands in all samples up to 25 kGy. Densitometry analysis of SDS-PAGE gels confirmed no size degradation (P>0.05) as a function of increased e-beam dose. Totol-volatile-basic-nitrogen (TVBN) excluded (P>0.05) protein degradation due to microbial activity. There was no increase (P>0.05) in lipid oxidation, as assessed with thiobarbituric-reactive-substances (TBARS), except in samples processed at 25 kGy. Dehydrated formula has low water activity, which likely protected nutrients from e-beam-induced chemical changes. This study demonstrates that proteins, lipids, and minerals in infant milk formula are stable when processed with e-beam up to 25 kGy at low temperature and under anaerobic conditions.