Inhibition of hemoglobin-mediated oxidation of regular and lipid-fortified washed cod mince by a white grape dietary fiber

The effectiveness of a white grape dietary fiber concentrate (WGDF) against hemoglobin-mediated oxidation of washed cod mince, with and without 10% added herring oil, was evaluated during ice storage. WGDF was added at two different levels: 2 and 4% based on final weight. An ethanol extract with the ethanol extractable polyphenols (EPP) and the ethanol-extracted grape dietary fiber residue were also tested as antioxidants in the washed cod mince. The addition of WGDF to the model system completely and significantly (p 相似文献   

Hemoglobin-mediated lipid oxidation and compositional characteristics of washed fish mince model systems made from cod (Gadus morhua), herring (Clupea harengus), and salmon (Salmo salar) muscle

The use of washed cod light muscle minces in mechanistic studies of hemoglobin (Hb)-mediated fish lipid oxidation has largely increased in the past 5 years. Although cod light muscle has a low level of intrinsic lipid oxidation catalysts, a prerequisite for a good oxidation model system, we believe it cannot fully mimic the oxidation kinetics taking place in other fish species being more susceptible to lipid oxidation. The aim of this study was to systematically investigate whether washed mince model systems useful in Hb-mediated oxidation studies could be prepared also from herring (Clupea harengus) and salmon (Salmo salar) light muscles. The kinetics of oxidation in the washed models was measured during ice storage (+/-Hb), and the results were related to compositional differences. Minces from cod, herring, and salmon light muscles were washed 3 times with 3 volumes of water and buffer. A 20 microM portion of Hb and 200 ppm streptomycin was then added, followed by adjustment of pH and moisture to 6.3 and 86%, respectively. Samples with or without Hb were then stored on ice, and oxidation was followed as peroxide value (PV), rancid odor, redness (a*) loss and yellowness (b*). Prior to storage, all minces and models were also analyzed for total lipids, fatty acids, alpha-tocopherol, proteins, Hb, Fe, Cu, and Zn. Hb-mediated lipid oxidation appeared within 2 days on ice in all models. Small differences in the oxidation rates ranked the models as herring > cod > salmon. These differences were ascribed to more preformed peroxides and trace elements in the herring model, and more antioxidants in the salmon model. Controls, without Hb, stayed stable in all cases except herring, where a very slight oxidation appeared, especially if the herring raw material had been prefrozen. In conclusion, fattier fish like dark muscle species and salmonoids are useful for making washed mince model systems and would be a better choice than cod if there is an interest in the oxidation kinetics of such species.     

Effect of milk protein concentrate on lipid oxidation and formation of fishy volatiles in herring mince (Clupea harengus) during frozen storage

The effect of milk protein concentrate (MPC) at 0, 2, 4, and 6% on lipid oxidation and volatile formation in frozen stored herring mince (-18 degrees C) was evaluated by analyzing samples at 0, 2, and 4 months for fatty acid composition, volatiles, and thiobarbituric acid reactive substances (TBARS). Sensory evaluation was also conducted to assess the intensity of fishy odor, and the volatiles were analyzed using static headspace gas chromatography-mass spectrometry (SHGC-MS). The addition of 4 and 6% MPC to herring mince resulted in a 33% and 50% reduction of TBARS, respectively, at month 4 and lessened the intensity of fishy odor throughout storage. However, MPC did not protect fatty acids from enzymatic degradation unless it was added immediately after mincing. Volatile analysis using SHGC-MS showed that 4% MPC was able to reduce headspace volatiles associated with fishy odor. MPC is most effective for reducing 4-heptenal, 3-methyl-1-butanol, 2-hexenal, and 1-penten-3-ol, which are known to be potent odorants associated with lipid oxidation.     

Loss of redness (a*) as a tool to follow hemoglobin-mediated lipid oxidation in washed cod mince

Instrumental measurement of redness loss (decrease in a* value) was evaluated as a tool to follow hemoglobin (Hb)-mediated lipid oxidation in fish muscle. Two washed cod mince model systems were used (prepared at pH 6.5 and 5.5), both fortified with 15 micromol/kg of trout Hb and adjusted to pH 6.5 and 81% moisture. The rate of oxidation was varied through pH alterations (pH 6.1 and 6.9) and addition of an antioxidative cod muscle press juice. During ice storage, TBARS, painty odor, and a* values were followed. In all "oxidizing" samples, a* values correlated well with TBARS and painty odor development; r = -0.95 and -0.77, respectively. In press juice containing samples, the correlation was lower (0.55 for a vs TBARS) because there was a slight a* value decrease even in the absence of measurable lipid oxidation. a* values distinguished between "oxidizing" and stable samples within 1 day, before any lipid oxidation products could be chemically detected. It was confirmed in an aqueous phosphate buffer model system that the redness loss corresponded to a buildup of brownish met-Hb at the expense of oxy- and deoxy-Hb. The a* value data were best used as a lipid oxidation index by calculating the rate of decrease (k value) in the "initial phase" of the redness loss (before accumulation of lipid oxidation products) or in the "differentiation phase" (during the exponential raise in TBARS/painty odor). Calibration to lipid oxidation products must, however, be made for each specific sample type. Washing method, pH, Hb-type, etc., all affected both k values and absolute a* readings. Small yellowness (b*) increases also occurred along with a value losses, possibly the result of polymerized Schiff bases.     

Mercury distribution and lipid oxidation in fish muscle: effects of washing and isoelectric protein precipitation

Nearly all the mercury (Hg) in whole muscle from whitefish (Coregonus clupeaformis) and walleye (Sander vitreus) was present as methyl mercury (MeHg). The Hg content in whole muscle from whitefish and walleye was 0.04-0.09 and 0.14-0.81 ppm, respectively. The myofibril fraction contained approximately three-fourths of the Hg in whitefish and walleye whole muscle. The sarcoplasmic protein fraction (e.g., press juice) was the next most abundant source of Hg. Isolated myosin, triacylglycerols, and cellular membranes contained the least Hg. Protein isolates prepared by pH shifting in the presence of citric acid did not decrease Hg levels. Addition of cysteine during washing decreased the Hg content in washed muscle probably through the interaction of the sulfhydryl group in cysteine with MeHg. Primary and secondary lipid oxidation products were lower during 2 °C storage in isolates prepared by pH shifting compared to those of washed or unwashed mince from whole muscle. This was attributed to removing some of the cellular membranes by pH shifting. Washing the mince accelerated lipid peroxide formation but decreased secondary lipid oxidation products compared to that of the unwashed mince. This suggested that there was a lipid hydroperoxide generating system that was active upon dilution of aqueous antioxidants and pro-oxidants.     

Recovery of functional proteins from herring (Clupea harengus) light muscle by an acid or alkaline solubilization process

Proteins from herring (Clupea harengus) light muscle were extracted using acidic or alkaline solubilization; 92 and 89% of the initial muscle proteins were solubilized at pH 2.7 and 10.8, respectively, of which 96 and 94% were recovered during precipitation at pH 5.5. Consistency of the pH-adjusted muscle homogenates increased with increased raw material age and homogenization intensity; it declined following holding on ice. Some hydrolytic myofibrillar protein degradation occurred during cold storage of the acidified (pH 2.7) homogenates. With alkalized homogenates, hydrolysis was negligible. The total lipid content changed from 0.13 g/g of protein in the muscle to 0.04 g/g of protein in both the acid- and alkali-produced protein isolates. Corresponding values for the phospholipid content were from 0.037 to 0.02 g/g of proteins. Acid- and alkali-produced proteins made gels with equal strain and color. Stress values were equal or lower in acid- versus alkali-produced protein gels. When ice-stored raw material was used, strain and stress values of gels were reduced.     

Evaluation of occasional nonresponse of a washed cod mince model to hemoglobin (Hb)-mediated oxidation

An emerging model to test antioxidants for application in seafoods is washed cod mince fortified with hemoglobin (Hb) as a catalyst. This system has been used to test the antioxidative activity of certain muscle extracts and some pure compounds such as BHA, BHT, TBHQ, and propyl gallate during ice storage. However, the washed cod mince model has occasionally been resistant to Hb-mediated oxidation. This has been in cases when the moisture of the model has been minimized by washes at the protein isoelectric point (pH approximately 5.5) to allow for large additions of potentially antioxidative solutions. In this paper, noncontrollable and controllable factors for this intriguing occasional oxidation resistance were studied. Compositional analyses (lipid content, alpha-tocopherol, and lipid hydroperoxides) and structural analysis of a "normal" oxidizing model and a stable model were done to identify any differences among them. Some controllable factors related to the model preparation that were studied included different washing pH values (5.5-6.6), Hb concentrations (7.2 and 13.5 microM), final model moisture contents (75, 81, and 90%), and light exposure during ice storage (0 h, 3-4 h, or 24 h of light/day). Results revealed a 2-fold higher alpha-tocopherol content in the stable model than in the oxidizing model. Electron microscopy images showed a more and less disrupted myofibrillar structure in the stable and the oxidizing cod model, respectively. This indicated that "cold setting" (i.e., pre-gelation) of the stable model may have occurred and prevented Hb from diffusing freely in the model. Controllable factors that reduced lipid oxidation in the models were less Hb and lower moisture.     

Changes in the antioxidative property of herring (Clupea harengus) press juice during a simulated gastrointestinal digestion

The aqueous fraction (press juice, PJ) from herring muscle was recently shown to inhibit hemoglobin-mediated oxidation of washed fish mince lipids during ice storage. As a first step to evaluate potential in vivo antioxidative effects from herring PJ, the aim of this study was to investigate whether herring PJ retains its antioxidative capacity during a simulated gastrointestinal (GI) digestion. Press juice from whole muscle (WMPJ) and light muscle (LMPJ) was mixed with pepsin solution followed by stepwise pH adjustments and additions of pancreatin and bile solutions. Digestive enzymes were removed from samples by ultrafiltration (10 kDa). Before, during, and after digestion, samples were analyzed for their peptide content and for antioxidative properties with the oxygen radical absorbance capacity (ORAC) and the low-density lipoprotein (LDL) oxidation assays. From 0 to 165 min of digestion, the content of <10 kDa peptides in WMPJ and LMPJ samples increased 12- and 7-fold, respectively. Further, both samples got approximately 12.5 times higher ORAC values and gave rise to approximately 1.3-fold increased lag phase in Cu2+-induced LDL oxidation. The largest changes in peptide content, ORAC values, and LDL oxidation inhibition occurred between 30 and 75 min of digestion, indicating that these parameters might be interrelated. When comparing analytical data obtained after 165 min of digestion with data obtained from analyses of native nondigested PJs, it was found that the data on peptide content, ORAC, and LDL oxidation from digested PJs were 64-69%, 121-161%, and 112-115%, respectively, of those of nondigested PJs. The study thus showed that enzymatic breakdown of PJ proteins under GI-like conditions increases the peroxyl radical scavenging activity and the potential to inhibit LDL oxidation of herring PJs. These data provide a solid basis for further studies of uptake and in vivo activities of herring-derived aqueous antioxidants.     

Incorporation and stabilization of omega-3 fatty acids in surimi made from cod, Gadus morhua

Surimi containing omega-3 fatty acids from algal oil was prepared by the addition of oil-in-water emulsions or bulk oil. Emulsion and bulk oil were added separately to surimi to provide approximately 500 mg of omega-3 fatty acids per serving of surimi (85 g). Addition of the emulsion had no effect on surimi gel strength, whereas bulk oil decreased gel strength an average of 31%. All surimi treatments containing algal oil increased in Hunter b values due to the presence of carotenoids in the oil. Among cryoprotectants, sodium tripolyphosphate was the major surimi additive responsible for retarding the formation of lipid hydroperoxides and thiobarbituric acid reactive substances (TBARS). Lipid hydroperoxide and TBARS formation was lower in surimi containing bulk oil compared to surimi with emulsified oil. Both EDTA and lipid soluble antioxidants were able to decrease lipid oxidation in surimi fortified with omega-3 fatty acids. This suggests that surimi containing nutritionally beneficial omega-3 fatty acids could be developed with good oxidative stability and gel strength.     

Hemoglobin-mediated oxidation of washed minced cod muscle phospholipids: effect of pH and hemoglobin source

Lipid pro-oxidative properties and deoxygenation/autoxidation patterns of hemoglobins from nonmigratory white-fleshed fish (winter flounder and Atlantic pollock) and migratory dark-fleshed fish (Atlantic mackerel and menhaden) were compared during ice storage at pH 7.2 and 6. A washed cod mince model system and a buffer model system were used for studying lipid changes and hemoglobin changes, respectively. TBARS and painty odor were followed as markers for lipid oxidation. At pH 6, all four hemoglobins were highly and equally active as pro-oxidants. At pH 7.2, pro-oxidation by all hemoglobins except that from pollock was slowed down, and activity ranked as pollock > mackerel > menhaden > flounder. The higher catalytic activities of the hemoglobins at pH 6 than at pH 7.2 corresponded with higher formation of deoxyhemoglobin and methemoglobin. Pollock had the most extensive formation of deoxy- and methemoglobin at both pH values, which could explain its high catalytic activity. The pro-oxidative differences among the other hemoglobins at pH 7.2 did not correlate with deoxygenation and autoxidation reactions. This indicates involvement of other structural differences between the hemoglobins such as differences in the heme-crevice volume. It is suggested that a biological reason for the species differences was their adaptations to different depths/water temperatures.     

Effects of released iron, lipid peroxides, and ascorbate in trout hemoglobin-mediated lipid oxidation of washed cod muscle

Approximately 7% of the iron associated with hemoglobin was released from the heme protein during 2 degrees C storage in washed cod muscle. EDTA (2.2 mM) neither accelerated nor inhibited hemoglobin-mediated lipid oxidation based on the formation of lipid peroxides and TBARS. This suggested that low molecular weight iron was a minor contributor to hemoglobin-mediated lipid oxidation in washed cod muscle. Ascorbate (2.2 mM) was a modest to highly effective inhibitor of hemoglobin-mediated lipid oxidation depending on which washed cod preparation was assessed. Experimental evidence suggested that the ability of residual ascorbate to breakdown accumulating lipid hydroperoxides to reactive lipid radicals can explain the shift of ascorbate from an antioxidant to a pro-oxidant. Increasing the lipid peroxide content in washed cod muscle accelerated hemoglobin-mediated lipid oxidation and decreased the ability of ascorbate to inhibit lipid oxidation. Preformed lipid peroxide content in cod muscle was highly variable from fish to fish.     

Consistency and solubility changes in herring (Clupea harengus) light muscle homogenates as a function of pH

Fish muscle proteins can be isolated from a variety of low-value raw materials by solubilization in either acid or base. If the consistency of the resulting solution is sufficiently low, it is possible to recover most of the solubilized proteins and remove most of the lipids by centrifugation. Lipid removal should greatly stabilize the isolated proteins. In a previous investigation into the use of herring for production of these protein isolates, it was observed that this species had particularly high consistency values when the proteins were solubilized. This study was undertaken to determine the consistencies obtained with herring light muscle tissue over the pH range covered by the two processes, from about pH 2.7 to 10.8. Protein solubility was compared to consistency of the resultant solutions. Maximum consistencies of the homogenates, approximately 220 and approximately 175 mPa.s, were obtained at pH values of approximately 3.5 and 10.5, respectively. Consistency began to increase approximately when solubilization began. Storage of homogenates at pH 2.7 decreased the consistency over a 10 min time period. The magnitude of the consistency peaks at both acid and alkaline pH values increased when using ice-stored as well as frozen-stored herring, especially in the acid range. Protein solubility at pH <4 and pH >/=10.8 slightly decreased after post-mortem storage of the herring muscle. It is suggested that the observed changes in consistency result from the expansion and solvation of protein aggregates which eventually dissociate into smaller units, perhaps even monomers.     

Role of lipid oxidation, chelating agents, and antioxidants in metallic flavor development in the oral cavity

This study investigated the production of metallic flavor, which is a combination of taste and retronasal odor. Chemical reactions in the oral cavity and saliva of healthy subjects were investigated after ingesting iron and copper solutions above and near threshold levels. Significant increase in lipid oxidation (p < 0.001) occurred after metal ingestion, detected as TBARS values. Ferrous ion caused the greatest flavor sensation and lipid oxidation, followed by cupric and cuprous ions. Ferric ion did not cause metallic sensation. Occurrence of oxidation was supported by damage to salivary proteins, detected as protein-carbonyls, and by a significant increase of odorous lipid oxidation related aldehydes. Sensory evaluation demonstrated that antioxidants (vitamins E and C) minimally reduced metallic flavor but that chelating agents (EDTA and lactoferrin) removed the metallic flavor. The role of lipid oxidation is essential for the production of a metallic flavor from ingestion of ferrous, cupric, and cuprous ions.     

Aqueous extracts from some muscles inhibit hemoglobin-mediated oxidation of cod muscle membrane lipids

It was evaluated whether trout hemoglobin (Hb)-mediated oxidation of minced washed cod muscle lipids could be prevented by an aqueous isolate from cod and some other muscle sources. Lipid hydroperoxides and painty odor developed approximately 4 days faster in washed than unwashed cod mince. When adding back an aqueous fraction (press juice) isolated from unwashed mince to washed mince at 2-6-fold dilutions, development of hydroperoxides and painty odor was either delayed or completely prevented. The inhibitory substances were heat stable, and their effect was slightly reduced at reduced pH. The <1 kDa fractions of whole and heated press juices were as inhibitory as the unfractionated press juices. Inhibition by the unheated, heated, and ultrafiltered (30 kDa) press juices was lost after dialysis. These findings implied the presence of one or more highly effective aqueous low molecular weight antioxidants in cod muscle press juice. The same antioxidative properties were found in heated haddock, dab, and winter flounder muscle press juices but not in heated herring and chicken muscle press juices. Unheated chicken press juice was however highly inhibitory.     

The effect of acid and alkali unfolding and subsequent refolding on the pro-oxidative activity of trout hemoglobin

The pro-oxidative activity of trout hemoglobin was significantly increased at low pH (2.5-3.5) in a washed fish muscle (WFM) system. It was found that the more unfolded the hemoglobin was the more exposed its heme group was, which increased its pro-oxidative activity. The amount of oxidation products produced (TBARS) were, however, lower at low pH vs neutral pH. At pH 10.5-11, the pro-oxidative activity of hemoglobin was greatly suppressed. The conformation of hemoglobin was significantly more stable at high pH as compared to pH 7 as judged by its visible absorption spectrum. Hemoglobin readjusted from low pH to pH 7 had a higher pro-oxidative activity (i.e., more rapid oxidation) in WFM than native hemoglobin at pH 7, even though TBARS values were lower than in the untreated sample at pH 7. The results suggest that the WFM becomes slightly more susceptible to oxidation after low pH treatment but also produces less TBARS. The increased pro-oxidative activity after pH readjustment correlated well with an incomplete recovery in the native structure on pH readjustment. A longer unfolding time and a lower pH led to a less refolded hemoglobin with increased pro-oxidative activity. Hemoglobin was less pro-oxidative at low pH in the presence of 500 mM NaCl. The presence of salt did, however, increase the pro-oxidative properties of hemoglobin after readjustment to pH 7. The treatment of washed fish muscle at alkaline pH followed by adjustment to pH 7 led to a slight delay in hemoglobin-mediated lipid oxidation in WFM as compared to native hemoglobin at pH 7. The results suggest that WFM becomes less susceptible toward oxidation after pH readjustment from alkaline pH. These results clearly show that for muscle protein extraction/isolation processes requiring highly alkaline or acidic conditions, alkaline conditions are preferred if the lipid oxidation originating from hemoglobin is to be minimized.     

包装形式对辐照冷却猪肉糜脂肪氧化的影响

本文研究了不同包装形式结合抗氧化剂对辐照冷却猪肉糜(猪五花肉)中脂肪氧化的抑制作用。添加抗氧化剂的冷却猪肉糜分别采取真空包装、无氧包装(N2+CO2)和气调有氧包装(O2+CO2+N2),然后经3kGy低剂量辐照,在4℃±1℃贮藏20d。分别在辐照的第0、5、10、15和20d对冷却猪肉糜脂肪氧化指标TBARS值、过氧化值进行测量。结果表明:添加抗氧化剂并结合真空包装能显著降低辐照猪肉糜中的脂肪氧化。因此在降低辐照及贮藏过程中冷却肉的脂肪氧化方面,真空包装要优于有氧包装。     

Ascorbyl palmitate, gamma-tocopherol, and EDTA affect lipid oxidation in fish oil enriched salad dressing differently

The aim of the study was to investigate the ability of gamma-tocopherol, ethylenediaminetetraacetate (EDTA), and ascorbyl palmitate to protect fish oil enriched salad dressing against oxidation during a 6 week storage period at room temperature. The lipid-soluble gamma-tocopherol (220 and 880 microg g-1 of fish oil) reduced lipid oxidation during storage by partly retarding the formation of lipid hydroperoxides (PV) and by decreasing the concentrations of individual volatile oxidation products by 34-39 and 42-66%, respectively. EDTA (10 and 50 microg g-1 of dressing) was the most efficient single antioxidant, and overall peroxide values and volatiles were reduced by approximately 70 and 77-86%, respectively. Conversely, prooxidant effects were observed with a high concentration of ascorbyl palmitate (300 microg g-1 of fish oil), whereas a low concentration was slightly antioxidative (50 microg/g of fish oil). Finally, a combination of all three antioxidants completely inhibited oxidation during storage, indicating that the prooxidant effects of ascorbyl palmitate were reverted or overshadowed by EDTA and gamma-tocopherol.     

Role of proteins in oil-in-water emulsions on the stability of lipid hydroperoxides

The purpose of this research was to better understand the mechanisms by which proteins affect the rates of lipid oxidation in order to develop protein-stabilized emulsion delivery systems with maximal oxidative stability. This study evaluated the affect of pH and emulsifier concentration on the stability of cumene hydroperoxide in hexadecane-in-water emulsions stabilized by beta-lactoglobulin (beta-Lg). Emulsions prepared with 0.2 wt % beta-Lg (at pH 7.0) showed a 26.9% decrease in hydroperoxide concentrations 5 min after 0.25 mM ferrous ion was added to the emulsion. EDTA, but not continuous phase beta-Lg, could inhibit iron-promoted lipid hydroperoxide decomposition. Lipid hydroperoxides were more stable to iron-promoted degradation at pH values below the pI of beta-Lg, where the emulsion droplet would be cationic and thus able to repel iron away from the lipid hydroperoxides. Heating the beta-Lg-stabilized emulsions to produce a cohesive protein layer on the emulsion droplet surface did not alter the ability of iron to decompose lipid hydroperoxides. These results suggest that proteins at the interface of emulsion droplets primarily stabilize lipid hydroperoxides by electrostatically inhibiting iron-hydroperoxide interactions.     

Lipid oxidation in herring fillets (Clupea harengus) during ice storage measured by a commercial hybrid gas-sensor array system

Volatile compounds released from herring fillets (Clupea harengus) during 15 days of storage on ice have been measured with a commercial hybrid gas-sensor array system. Using partial least-squares regression modeling, the sensor responses were correlated with data from chemical analyses (lipid oxidation products and antioxidants) and sensory analyses (odor). Eight of the 16 sensors proved significant in the correlation studies: 6 metal oxide semiconductor field effect transistor (MOSFET) sensors and 2 Taguchi type sensors. Correlation coefficients for chemical and sensory data ranged from 0.9 to 0.98 and from 0.49 to 0.92, respectively, with 0.92 referring to both "sharp/acrid" and "rancid" odors. Prediction errors ranged from 8 to 14% and from 11 to 25% for the chemical and sensory measures, respectively. That the prediction errors for oxidation product formation (5-9%) were close to the analytical errors of the chemical reference methods indicated close to "optimum" performance of the gas-sensor system. The sensor system predicted the storage time of the herring with a 1-day error. Results illustrate high potential of the gas-sensor technology in rapid nondestructive quality determination of ice-stored herring.     

Lipid oxidation in fillets of herring (Clupea harengus) during ice storage

The influence of ice storage on lipid oxidation, odor, antioxidants, water-soluble catalysts, and microorganisms was investigated in fillets of herring (Clupea harengus) during 15 days. Based on linear regression analyses of the data, significant rises (p ascorbic acid > glutathione peroxidase (GSH-px); however, GSH-px correlated best to the development of lipid oxidation products (r(mean) = -0.96). The activity of aqueous pro-oxidants, which were enzymatic in nature to a great extent, had decreased by 75% at day 15. No significant increase in total bacteria was seen until after 7 days. There were major local differences in both composition and stability throughout the fillet. Oxidation proceeded most rapidly in the tissue right under the skin, probably explained by its high initial pro-oxidative activity.