首页 | 本学科首页   官方微博 | 高级检索  
相似文献
 共查询到20条相似文献，搜索用时 15 毫秒
1.
Beef hemoglobin (Hb) had lower levels of deoxyHb and autoxidized much slower as compared to trout Hb at pH 6.3. Chicken Hb autoxidized at a rate intermediate between beef and trout Hb. In the presence of hydrogen peroxide, metHb formed rapidly from trout Hb whereas beef Hb was essentially nonreactive with hydrogen peroxide. The autoxidation rate of perch Hb was more rapid than trout Hb despite the low deoxyHb content of perch Hb. Perch Hb was a better catalyst of lipid oxidation than trout Hb when added to washed cod muscle based on formation of lipid hydroperoxides and thiobarbituric acid reactive substances. These studies indicate that autoxidation rate does not always increase with increasing deoxyHb content. The role of heme crevice volume in heme protein autoxidation is discussed. Among other factors, these studies suggest that rates of lipid oxidation in various muscle foods may depend on the relative ability of hemoglobins from different animal species to promote lipid oxidation.  相似文献   

2.
Deoxyhemoglobin-mediated lipid oxidation in washed fish muscle   总被引：1，自引：0，他引：1  
Deoxyhemoglobin-mediated lipid oxidation was studied by comparing the pro-oxidative activity of anodic and cathodic hemoglobins from trout in a washed cod muscle model system. At pH 6.3, cathodic hemoglobins were nearly fully oxygenated while anodic hemoglobins were poorly oxygenated. Anodic hemoglobins initiated lipid oxidation in washed cod muscle much more rapidly than cathodic hemoglobins, as measured by thiobarbituric acid reactive substances (TBARS) formation. Moreover, anodic hemoglobins appeared to oxidize more rapidly as compared to cathodic hemoglobins in the washed cod muscle model system, as measured by a decrease in redness (a value). A more pronounced pro-oxidative activity of deoxyhemoglobin as compared to oxyhemoglobin was confirmed by accelerated lipid hydroperoxide and TBARS formation in the washed cod muscle model system upon combined addition of anodic hemoglobins and adenosine triphosphate, which is known to lower the oxygenation of anodic hemoglobins at pH 7.2, as compared to only addition of anodic hemoglobins to the washed cod muscle. These studies suggest that deoxyhemoglobin is more pro-oxidative than its oxygenated counterpart at pH values found in postmortem fish muscle.  相似文献   

3.
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.  相似文献   

4.
The molecular mass of trout myoglobin was 16017 Da based on electrospray ionization mass spectrometry. A Root effect (low oxygen affinity at pH 6.3) was determined in trout hemoglobin but not myoglobin. At pH 6.3, myoglobin autoxidized more rapidly (3.5-fold) as compared to anodic hemoglobin. Anodic hemoglobin was a better catalyst of lipid oxidation in washed cod muscle as compared to myoglobin at pH 6.3. This suggested that some process other than met heme protein formation was the rate-limiting step in lipid oxidation processes. Heme loss rates were determined using the apomyoglobin mutant H64Y prepared from sperm whale. Anodic hemoglobin released its heme group much more rapidly than myoglobin. In comparisons of anodic and cathodic hemoglobins, heme loss rate better predicted the onset of lipid oxidation than autoxidation rate. These studies collectively suggest that heme dissociation has a primary role in the ability of different heme proteins to promote lipid oxidation processes.  相似文献   

5.
The hemoglobin variant rHb 0.1, which possesses a decreased ability to form subunits, stimulated lipid oxidation in washed fish muscle less effectively as compared to wild-type hemoglobin (rHb 0.0). This could be due to the lower hemin affinity and more rapid autoxidation rate of subunits as compared to tetramers. To differentiate between hemin affinity and autoxidation effects, ferrous V68T Mb was compared to ferrous wild-type myoglobin (WT Mb). WT Mb has a more rapid hemin loss rate (25-fold) than does V68T, while V68T autoxidized more rapidly than did WT Mb (60-fold). Ferrous WT Mb promoted TBARS and lipid peroxide formation more rapidly than did ferrous V68T (p < 0.01). This indicated hemin loss rate was more critical in determining onset of lipid oxidation as compared to autoxidation rate. Hemin alone was capable of stimulating lipid oxidation. Albumin enhanced the ability of hemin to promote lipid oxidation. MetMb promoted lipid oxidation more effectively than did ferrous Mb, which could be due to the lower hemin affinity of metMb as compared to that of ferrous Mb. EDTA, an iron chelator, had no effect on the rate or extent of lipid oxidation mediated by Mb in the cooked system. Variants with a 975-fold range of hemin affinities promoted lipid oxidation with equivalent efficacy in cooked washed cod contrary to results in uncooked washed cod. The cooking temperatures apparently denature the globin and release hemin reactant to such an extent that the impact of hemin affinity on lipid oxidation observed in the raw state is negated in the cooked state. These studies collectively suggest released hemin is of primary importance in promoting lipid oxidation in raw and cooked washed fish muscle.  相似文献   

6.
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.  相似文献   

7.
There was a wide variation in the amounts of hemoglobin extracted from the muscle tissue of bled and unbled fish. Averaged values suggested that the residual blood level in the muscle of bled fish was substantial. Myoglobin content was minimal as compared to hemoglobin content in mackerel light muscle and trout whole muscle. Hemoglobin made up 65 and 56% of the total heme protein by weight in dark muscle from unbled and bled mackerel, respectively. Bleeding significantly reduced rancidity in minced trout whole muscle, minced mackerel light muscle, and intact mackerel dark muscle but not minced mackerel dark muscle stored at 2 degrees C. The reduction was in the number of fish that had a longer shelf life; muscle from certain bled fish had rancidity that was comparable to the rancidity in unbled controls. The soluble contents of erythrocytes accounted for all of the lipid oxidation capacity of whole blood added to washed cod muscle. Limiting lysis of erythrocytes delayed lipid oxidation, which was likely due to keeping hemoglobin inside the erythrocyte. Apparent breakdown of lipid hydroperoxides occurred only when a critical level of hemoglobin was present. Blood plasma was slightly inhibitory to oxidation of washed cod lipids. These studies suggest that blood-mediated lipid oxidation in fish muscle depends on various factors that include hemoglobin concentration, types of hemoglobin, plasma volume, and erythrocyte integrity.  相似文献   

8.
The effect of pH and hemoglobin on oxidation of the microsomal lipids of cod was determined in isolated microsomes and in washed cod muscle. An increase of hemoglobin concentration from 0.5 to 15 microM accelerated lipid oxidation in both systems. In cod microsomes the rate of lipid oxidation increased in the order pH 6.8 > pH 7.6 > pH 8.4 > pH 6.0 > pH 3.5. However, in washed cod muscle a decrease of pH from 7.8 to 6.8 greatly increased the lag phase and decreased the rate of lipid oxidation. A further decrease in pH to 3.5 decreased the lag phase and increased the rate of lipid oxidation further. A decrease of pH from 7.6 to 6.4 greatly reduced the affinity of hemoglobin for oxygen. Formation of methemoglobin due to autoxidation occurred more rapidly at pH 6.0 than at pH 7.5. Structural changes of the isolated microsomal membranes could be the reason for the unexpected slow lipid oxidation in microsomes at pH 6.0 and below.  相似文献   

9.
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.  相似文献   

10.
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.  相似文献   

11.
The influence of galloyl residues on the antioxidant mechanism of polyphenols to prevent hemoglobin-promoted lipid oxidation was investigated by using polyphenolic fractions with different degrees of galloylation: nongalloylated structures from pine bark (IVP), medium-galloylated from grape pomace (IVG), and high-galloylated from witch hazel bark (IVH). Hemoglobin (Hb) from the pelagic fish horse mackerel (Trachurus trachurus) was employed as a Hb standard. In vitro experiments showed an important increase in the deoxygenation and autoxidation of horse mackerel Hb at acidic pH values. All polyphenolic fractions significantly reduced the redox stability of Hb in buffer solutions, showing a greater deoxygenation and methemoglobin (metHb) formation in the presence of IVH, followed in decreasing order by IVG and IVP. However, galloylated polyphenols (IVH and IVG) were efficient to inhibit the oxidation of the oxygenated Hb (OxyHb) and the formation of lipid oxidation products in chilled washed fish muscle. This antioxidant activity of galloylated proanthocyanidins showed a positive relationship with the phenolic concentration. Polyphenols devoid of galloyl groups (IVP) were less active to prevent either Hb oxidation or lipid oxidation in fish muscle. The results draw attention to the potential role of galloyl residues to lessen Hb-catalyzed lipid oxidation in muscle and to maintain Hb in reduced and oxygenated states, which exhibit lower pro-oxidant activity as compared to the metHb and deoxyHb species.  相似文献   

12.
Unheated press juice (PJ) obtained from chicken breast muscle was a potent inhibitor of hemoglobin-mediated lipid oxidation in washed cod muscle. The <1 kDa fraction had a negligible effect on the rate of lipid oxidation. The high-molecular-weight (HMW) fraction was mildly inhibitory when added alone and highly inhibitory in the presence of <1 kDa components. Proteins of the HMW fraction were further fractionated by ammonium sulfate precipitation. Proteins in the 80% fraction were most inhibitory compared with other precipitated fractions on an equal protein basis. Inhibition by PJ was substantially decreased due to treatment with ascorbate oxidase. Adding ascorbate to the HMW fraction did not increase its inhibition, which suggested the presence of a complex ascorbate-reducing system in PJ consisting of HMW and low-molecular-weight (LMW) components. The ability of added ceruloplasmin to inhibit lipid oxidation was remarkably enhanced by addition of ascorbate or the <1 kDa fraction. Heated and centrifuged PJ had 8 times more LMW iron compared to unheated PJ. Adding heated PJ to washed cod containing hemoglobin slightly increased the rate and extent of lipid oxidation.  相似文献   

13.
Hemoglobin plays an important role in the color and oxidative stability of seafoods. A recent practice in the seafood industry is to stabilize muscle color by the application of gases containing carbon monoxide. The goal of this study was to examine and compare the properties of tilapia hemoglobin complexed to either O(2) (Oxy-Hb) or CO (CO-Hb) at pH 6.5, which reflects the tilapia muscle postmortem pH. CO-Hb was significantly (p < 0.01) more stable against autoxidation compared to Oxy-Hb when kept at 4 and -30 degrees C for 23 days. Almost no loss of CO was detected for both temperatures according to the UV-vis spectra of Hb. This stabilization was also believed to play a role in increased protein structure stabilization (p < 0.001) since less protein aggregation was seen for CO-Hb. The higher protein stabilization for Hb was linked to the heme group, which was maintained in its reduced state longer for CO-Hb vs Oxy-Hb and was likely less exposed to solvent. CO-Hb had significantly (p < 0.01) less peroxidase activity than Oxy-Hb and thus reactivity with H(2)O(2). The pro-oxidative activity of CO-Hb was significantly (p < 0.01) reduced in a linoleic acid micelle system compared to that of Oxy-Hb, while smaller differences in activity were seen in a washed cod and tilapia muscle model system.  相似文献   

14.
Variants of sperm whale myoglobin (Mb) were used to assess the mechanism of heme protein-mediated lipid oxidation in washed cod muscle. A myoglobin variant with high hemin affinity (V68T) was an exceptionally poor promoter of lipid oxidation, while a Mb variant with low hemin affinity (H97A) was a potent promoter of lipid oxidation. V68T releases hemin slowly due to the ability of threonine to hydrogen bond with coordinated water and the distal histidine within the heme crevice. H97A rapidly releases hemin because the relatively small alanine residue creates a channel for water to easily enter the heme crevice which weakens the covalent linkage of hemin to the proximal histidine. A variant sensitive to heme degradation (L29F/H64Q) was a weaker promoter of lipid oxidation compared to wild-type Mb. This suggests that degrading the heme ring and releasing iron decreased the ability of Mb to promote lipid oxidation. Free radicals resulting from hemin-mediated decomposition of lipid hydroperoxides have the capacity to propagate lipid oxidation and degrade hemin catalyst. This may explain why heme proteins behave as reactants rather than "catalysts" of lipid oxidation in washed cod. Collectively these studies strongly suggest that released hemin is the critical entity that drives heme protein-mediated lipid oxidation in washed fish muscle.  相似文献   

15.
Hemoglobin-mediated lipid oxidation in washed, minced cod muscle was related to the triacylglycerol to membrane lipid ratio. The same rapid development of thiobarbituric acid reactive substances (TBARS) and painty odor occurred with and without the presence of up to 15% menhaden oil. Without hemoglobin, development of TBARS and painty odor was slow, despite a high amount of hydroperoxides in samples with oil added (1135 micromol/kg muscle). This suggested that hemoglobin reacted by cleaving preformed hydroperoxides into secondary oxidation products. Nearly doubling the hemoglobin concentration approximately doubled the extent of lipid oxidation with and without added oil. This indicated that hemoglobin was limiting for the oxidation reaction. The noneffect of added oil suggests that membrane lipids and/or preformed membrane lipid hydroperoxides provided sufficient substrate in hemoglobin-catalyzed oxidation of washed minced cod muscle. Fe(2+-)ADP did not induce any oxidation of washed minced cod with/without added oil. Results suggest that lipid oxidation in fatty fish may be more related to the quantity and type of the aqueous pro-oxidant and the membrane lipids than to variations in total fat contents.  相似文献   

16.
During the extraction of muscle to produce protein isolates by acid or alkali solubilization, membranes are exposed to abnormally low or high pH. Low but not high pH treatment induces rapid oxidation of membrane phospholipids in the presence of hemoglobin. The goal of this research work was to study the oxidative stability of microsomes under the conditions met during acid solubilization. Isolated microsomes from cod muscle were used as a model system. At pH 5.3 or lower, 99% of isolated cod membranes sedimented at low centrifugation speeds. Isolated membranes that were exposed to pH 3.0 were less susceptible to hemoglobin-mediated lipid oxidation. Cod hemoglobin exposed to pH 3 was rendered less pro-oxidative than the untreated cod hemoglobin. However, when microsomes and hemoglobin were together exposed to low pH, oxidation was promoted. Citric acid and calcium chloride, as well as press juice isolated from cod muscle, were able to inhibit lipid oxidation of microsomal suspensions.  相似文献   

17.
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.  相似文献   

18.
Hemoglobin-mediated lipid oxidation was studied by adding hemolysate to washed cod muscle. Three pH values were examined (pH 7.6, 7.2, and 6.0). The lag time prior to rancidity and thiobarbituric acid reactive substance development decreased greatly as the pH was reduced (p < 0.01). Formation of methemoglobin due to autoxidation of the heme pigment was found to occur more rapidly at reduced pH. Also, the level of deoxyhemoglobin was found to sharply increase with pH reduction in the range of pH 7.6-6.0. This suggested a potential role for deoxyhemoglobin as a catalyst. ATP lowered hemoglobin oxygenation at pH 7.2. Peroxidation of linoleic acid by oxy/deoxyhemoglobin and methemoglobin was investigated at two levels of preformed lipid hydroperoxides. At a reduced level of preformed lipid hydroperoxides, oxy/deoxyhemoglobin stimulated peroxidation of linoleic acid, whereas methemoglobin did not. At the higher level of preformed lipid hydroperoxides, both oxy/deoxyhemoglobin and methemoglobin were active. This investigation suggests that reduced hemoglobins played an important role in lipid oxidation processes.  相似文献   

19.
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.  相似文献   

20.
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.  相似文献   

设为首页 | 免责声明 | 关于勤云 | 加入收藏

Copyright©北京勤云科技发展有限公司  京ICP备09084417号