Lipid peroxidation-derived cytotoxic aldehyde, 4-hydroxy-2-nonenal in smoked pork

The contents of 4-Hydroxy-2-nonenal (HNE), cytotoxic aldehyde, in smoked meat products (ham, bacon and sausage) were analyzed. All the samples analyzed contained HNE, although large differences in the contents between the different samples were observed. In one lot of ham (H1) and wiener sausage (WS1) a high level in HNE was observed. The changes of HNE contents of pork meats containing 0, 0.1, 0.5 and 1% Sugi wood vinegar (SWV) stored at 0?°C were also analyzed for 7 days. As an index of lipid peroxidation level, malonaldehyde (MA) contents were also analyzed in these samples. After 7 days of storage, HNE was detected only in pork meats containing 1% SWV and the level was similar to those of H1 and WS1. Judging from MA contents, SWV may act as a pro-oxidant in pork meats and HNE may accumulate in pork in which lipid peroxidation is in progress.     

Effect of irradiation and packaging conditions after cooking on the formation of cholesterol and lipid oxidation products in meats during storage

The effect of irradiation and packaging conditions on the content of cholesterol oxidation products (COPs) and lipid oxidation in cooked turkey, beef, and pork during storage was studied. Ground turkey leg, beef, and pork were cooked, packaged either in oxygen-permeable or oxygen-impermeable bags, and irradiated at 0 or 4.5 kGy. Lipid oxidation and COPs were determined after 0 and 7 days of storage at 4°C. Packaging of cooked meat was more important than irradiation in developing COPs and lipid oxidation in cooked meats during storage. 7-Hydroxycholesterol, 7β-hydroxycholesterol, β-epoxide, and 7-ketocholesterol were among the major COPs formed in cooked turkey, beef, and pork after storage, and their amounts increased dramatically during the 7-day storage in aerobic conditions. Irradiation had no significant effect on the amounts of any of the COPs found in cooked turkey and beef, but increased (P<0.05) the amounts of - plus 7β-hydroxycholesterol, β-epoxide, 7-ketocholesterol, and total COPs in aerobically packaged cooked pork. The amounts of COPs and lipid oxidation products (TBARS) closely related to the proportion of polyunsaturated fatty acids in meat. The results indicated that the composition of fats in meat is important on the oxidation rates of lipids and cholesterol, and packaging is far more important than irradiation in the formation of COPs and lipid oxidation in cooked meat.     

Relationship between lipid peroxidation and fat content in Japanese Black beef Longissimus muscle during storage

We examined the relationship of crude fat content to lipid peroxidation of beef during storage. Longissimus muscle samples (fat content; 6.5–39.4%) from 27 Japanese Black beef steers were stored for 1, 4, 7 and 10 days, and thiobarbituric acid reactive substances (TBARS) and lipid hydroperoxides (LOOH) were determined. TBARS values increased significantly (P<0.05), but LOOH did not change during the 10- day storage period. TBARS values were negatively correlated (P<0.05) with fat content in samples stored for 1, 4, 7 and 10 days. LOOH values, however, were not significantly correlated with fat content except on day 1. Phospholipid contents were correlated (P< 0.01) with LOOH values on each measurement day, but not significantly correlated with TBARS values except on day 1. These findings indicated that: (1) high-fat beef had high preservative properties, and that; (2) TBARS formation was correlated with LOOH derived from phospholipid oxidation in the initial period of storage, and was correlated directly with fat content in a later period.     

Lipid oxidation, color changes and volatiles production in irradiated pork sausage with different fat content and packaging during storage

Effects of irradiation on lipid oxidation, color and volatiles production in pork sausages with different fat content and packaging were determined. Sausages (with 4.7, 10.5 and 15.8% fat content) were sliced and vacuum-packaged either in oxygen-permeable or impermeable bags, irradiated (0 or 4.5 kGy) and stored at 4°C for 7 days. Lipid oxidation, color and volatiles productions were analyzed at 0, 3 and 7 days of storage. TBARS (2-thiobarbituric acid reactive substances) values of cooked pork sausages increased with the increase of fat content regardless of storage, irradiation or packaging types. Irradiated samples had higher TBARS than nonirradiated at 0 day but the difference disappeared during storage in both packaging types. Lightness of sausages (Hunter L-value) increased with the increase of fat content and storage time but was not affected by irradiation. In aerobic packaging, irradiation reduced Hunter a-values of pork sausages at 0 day but irradiation effect on a-value disappeared during storage. In vacuum packaging, however, irradiated samples had higher Hunter a-values than nonirradiated samples. Irradiation increased 1-heptene and total volatiles, but the amount of 1-heptene was not associated well with TBARS values of pork sausages. In both irradiated and nonirradiated pork sausages, aerobic packaging produced more volatiles than vacuum packaging during storage. It was concluded that irradiation and fat content had significant effects on lipid oxidation, color and volatiles production of cooked pork sausages during storage but that oxygen availability had a stronger effect than irradiation and fat content.     

Cholesterol oxidation products in irradiated raw meat with different packaging and storage time

The effect of irradiation and packaging conditions on the formation of cholesterol oxidation products (COPs) as well as lipid oxidation products was determined in raw turkey leg, beef, and pork loin meat during 7 days of storage. Ground turkey leg, beef, and pork loin muscles were prepared as patties. The patties were individually packaged either in oxygen-permeable or impermeable bags, irradiated at 0 or 4.5 kGy using a Linear Accelerator, and stored at 4°C. The COPs such as 7-hydroxycholesterol, 7β-hydroxycholesterol, and 7-ketocholesterol were detected in fresh raw meats at 0 day at the level of 10.9 to 49.2 μg/g lipid. After 7 days of storage, other COPs such as epoxides, 20-hyroxycholesterol, and choletanetriol were formed in mainly aerobically packaged and irradiated raw meats. Packaging effect was more crucial on the cholesterol and lipid oxidation than irradiation. In aerobically packaged and irradiated meats, turkey leg muscles had higher COPs value than beef or pork did. COPs and thiobarbituric acid reactive substances (TBARS) values had a strongly positive correlation in turkey leg and pork. But, cholesterol oxidation in beef proceeded in irradiated and aerobically stored samples despite of its low level of TBARS value.     

Malonaldehyde content in some breads and its change during storage

Malonaldehyde (MA) content in plain bread, French bread, and croissants was analyzed. MA was detected in all the analyzed samples. The MA and lipid contents in croissants were higher than those in other breads. Changes in MA content in plain bread, French bread, and croissants stored at 4 degrees C were examined after 0, 2, and 4 days of storage. The MA content in all the bread samples increased during the storage period. The highest increase of MA content was observed in French bread.     

PRODUCTION AND BINDING OF MALONALDEHYDE DURING STORAGE OF COOKED PORK

Cooked pork samples were stored at 3°C and analyzed for malonaldehyde (MA). MA increased to a maximum and remained there, typical behavior for a food but contrasting with pure lipid oxidation in which MA increases and then decreases as volatile MA is lost. The failure to lose MA in food products may be attributed to MA binding. Water extracts of cooked pork samples (representing approximately l /3 of the total MA) were fractionated on G-10 Sephadex and analyzed for MA. With increasing storage time, a definite change in elution pattern from free MA to bound MA took place; the binding was not to protein or amino acids.     

LIPID OXIDATION IN RETAIL BEEF, PORK AND CHICKEN MUSCLES AS AFFECTED BY CONCENTRATIONS OF HEME PIGMENTS AND NONHEME IRON AND MICROSOMAL ENZYMIC LIPID PEROXIDATION ACTIVITY

Muscles of beef, pork and chicken purchased in two seasons were analyzed for lipid oxidation potential, concentrations of total pigments, myoglobin and nonheme iron, and microsomal enzymic lipid peroxidation activity. To determine lipid oxidation potential, thiobarbituric acid (TBA) assays with antioxidant protection were conducted on raw and cooked comminuted muscles stored at 4°C. TBA values of raw chicken muscles (white and dark) and pork muscles were low and changed little during 2–6 days of storage, whereas the values of raw beef muscles were higher and increased progressively. However, TBA values of cooked muscles of all three species increased during 2–4 days of storage with no marked differences among the species. Total pigment and mycglobin concentrations best explained the differences in TBA values of stored, raw muscles among the three species.     

Survival and growth of Escherichia coli O157:H7, Yersinia enterocolitica and Salmonella enteritidis on decontaminated and untreated meat

Decontamination of meat or carcasses may have an effect in reducing the number of pathogens. Recontamination with other pathogens during cutting or packaging may, however, result in higher growth on decontaminated than on untreated meat due to the lack of competing non-pathogenic microorganisms. In this study we compared the growth of pathogens during storage at 10°C (worst case condition) on untreated meat and meat that had been decontaminated by steam vacuuming combined with spraying with 0.2 M lactic acid. Salmonella enteritidis inoculated on chicken multiplied quickly and reached log 7 cfu per cm(2) after 4 days of aerobic storage at 10°C, but growth was not significantly higher on decontaminated than on untreated chicken. The number of Yersinia enterocolitica inoculated on decontaminated pork skin reached log 9 cfu per cm(2) after 5 days of aerobic storage at 10°C. Overall, growth on vacuum-packed decontaminated and untreated pork under the same conditions was not significantly different, although there tended to be less growth on the untreated samples. The number of Escherichia coli O157:H7 on decontaminated beef increased by nearly 3 log cycles after 5 days of aerobic storage at 10°C compared to only a 1 log cycle increase on untreated beef. For the vacuum-packed beef, growth of E. coli O157:H7 on the fresh meat was very slow, while there was about a 3 log increase on the decontaminated beef. A higher average growth on the decontaminated beef was also found in an experiment with a very low inoculum (27 cfu per cm(2)). During storage of vacuum-packed samples there was multiplication of E. coli O157:H7 on the decontaminated beef, but virtually none on the untreated beef. This study shows that multiplication of S. enteritidis on chicken and Y. enterocolitica on pork skin was not significantly higher on decontaminated compared to untreated meat. The increased multiplication of E. coli O157:H7 on decontaminated beef, especially when vacuum-packed, gives cause for concern. Preventive measures might be a strict HACCP approach to the handling of the decontaminated meat before packaging or use of a protective culture of lactic acid bacteria.     

Pro-oxidative effects of NaCl in microbial growth-controlled and uncontrolled beef and chicken

Ground beef or chicken breast muscle samples?- either pretreated (PT) with 60 ppm chlortetracycline/0.2% potassium sorbate (to control microbial growth) or not pretreated (NPT)?- were mixed with 0-5% NaCl and aerobically refrigerated for 0-6 days. NaCl increased 2-thiobarbituric acid-reactive substances (TBARS) values of stored beef and chicken, regardless of pretreatment, with its concentration having a quadratic effect on TBARS. After 3 or 6 days, beef samples were much higher in TBARS content than chicken samples. At each NaCl level, TBARS content increased or tended to increase with storage time for beef (NPT and PT) and PT chicken, but not in NPT chicken. Nonheme iron content in stored NPT and PT beef and PT chicken tended to increase with NaCl concentration.     

Effect of Fe2+, Salt, Cooking and Shredded CoffiR on Thiobarbituric Acid (TBA) Numbers in Ground Beef

Presence of ferrous iron (Fe²⁺) and/or salt (NaCl) in ground beef followed by cooking and storage resulted in marked increases in lipid oxidation as measured by TBA values. Addition of an edible collagen film (Coffi^R) to minced fresh beef did not influence TBA values. Cooking fresh ground beef resulted in lowering of TBA values (when compared to raw beef), but TBA values increased more rapidly and to a greater extent in cooked beef than in raw samples during 7 days refrigerated storage.     

Metmyoglobin and inorganic metals as pro-oxidants in raw and cooked muscle systems

The pro-oxidant activities of metmyoglobin (Mb) and metal ions on the induction of lipid oxidation in raw and heated water-washed muscle systems from fish, turkey, chicken, pork, beef and lamb and during storage of these systems at 4°C, were investigated. Lipid oxidation was invariably faster in heated than in raw systems. In raw Mb-catalyzed systems, oxidation was slow over a 5-day period, except in fish, where significant (P < 0·05) increases in TBA values occurred; in contrast, significant (P < 0·05) increases in TBA values occurred in cooked fish, turkey, chicken and pork after 3 days of storage. Cooked beef and lamb, however, showed significant lipid oxidation only after 5 days of storage. Fe(2+) was found to be highly catalytic in cooked muscle. Cu(2+) and Co(2+) were less effective catalysts than Fe(2+); the overall pro-oxidant activity was in the order Fe(2+) > Cu(2+) > Co(2+) > Mb, and the susceptibility to lipid oxidation of the muscle systems was in the order: fish > turkey > chicken > pork > beef > lamb, probably reflecting the degree of unsaturation of the constituent triglyceride fractions.     

Culinary herbs inhibit lipid oxidation in raw and cooked minced meat patties during storage

The effect of dried spices and the ethanol extract of those spices was studied on the stability of fresh chicken minced meat, and fresh and cooked pork patties pretreated with NaCl during refrigerated and frozen storage. The antioxidant activities of the spices were measured by thiobarbituric acid reactive substances (TBARS) and peroxide value (POV) in meat samples. The lipid oxidation was effectively inhibited in the chicken meat treated with several dry spices diminishing the TBARS to a range of 32% and 83% of those found in the control samples in frozen stored meat for 6 months. Marjoram, wild marjoram and caraway were the most effective dry spices. Ethanolic extracts of the same spices were more potent as antioxidants by lowering the concentration of the TBARS to a range of 20–27% of those found in the control samples. Addition of sodium salt to the minced pork resulted very high concentrations of the oxidation products originated from the polyunsaturated fatty acids. The treatment with ethanolic extract of spices (sage, basil, thyme and ginger) significantly inhibited the lipid peroxidation in refrigerated and chilled pork patties pretreated with NaCl by reducing both POV and TBARS. Heat treatment with microwaves produced significantly elevated levels of both lipid peroxides and TBARS, but the amount of these oxidation products was less than 10% in spice‐treated salted meat samples compared to that in untreated ones. Lipid peroxidation also grew continuously during the storage period at −18°C in raw and cooked samples. Ethanolic extracts of spices had a very strong antioxidative effect inhibiting lipid peroxidation in heat‐treated meat products during frozen storage. The highest antioxidant activity was observed in the case of ginger. High correlation coefficients were found between TBARS and POV both in raw and cooked pork patties (0.86, 0.91, respectively) during frozen storage. It is supposed that these compounds originated from the polyunsaturated fatty acids during oxidation processes but at different stages. Utilization of spices, spice mixtures or spice extracts in semi‐prepared meat products intended to be frozen for up to 6 months or more before consumption is proved to be advantageous in regard of shelf life of the food, as well as of human health, because of the beneficial effect of spices in inhibition of lipid peroxidation during heat treatment and chilling storage. © 1999 Society of Chemical Industry     

Evaluation of cholesterol and lipid oxidation in raw and cooked minced beef stored under oxygen-enriched atmosphere

Oxygen-enriched modified atmosphere packaging (MAP) represents an important means to stabilize meat colour but may lead to an increase in lipid oxidation, influencing the acceptability and safety of the product. In this work, the effect on cholesterol and lipid susceptibility to oxidation was investigated in commercial minced beef held under MAP (80% O(2)/20% CO(2)). Cholesterol oxidation products (COPs), peroxide value (PV) and thiobarbituric acid reactive substances (TBARS) were determined, before and after pan frying, at 1, 8 and 15 days since packaging under refrigerated storage (3-4°C). 7α-Hydroxycholesterol, 7β-hydroxycholesterol and 7-ketocholesterol were the more abundant COPs identified. COPs significantly increased in raw beef during storage: after 1, 8 and 15 days since packaging COPs were at the levels of 10.4, 30.7 and 60.5μg/g of fat, respectively. Cooking did not affect cholesterol oxidation in freshly packaged minced beef but led to a rise in COPs amount with respect to raw muscle after 8 and 15 days of storage. The trend in cholesterol oxidation reflected the progressive increase in lipid peroxidation rate brought by MAP conditions.     

Chloride salt type/ionic strength, muscle site and refrigeration effects on antioxidant enzymes and lipid oxidation in pork

The effects of NaCl and KCl at varying ionic strengths on catalase and glutathione peroxidase (GSH-Px) activities and lipid oxidation in refrigerated ground pork muscles from different anatomical locations were studied. Catalase and GSH-Px activities were higher in boston butt (BB) than in longissimus dorsi (LD), whereas lipid oxidation measured by 2-thiobarbituric acid substances (TBARS) content was higher in LD. Catalase activity was stable in both BB and LD during 4-day storage; GSH-Px activity decreased in LD. GSH-Px activity decreased more with NaCl than KCl, whereas salt type had no consistent effect on catalase activity. TBARS content, however, increased more with NaCl than with KCl. NaCl at the highest ionic strength decreased GSH-Px activity by 19.2 and 18% in LD and BB, respectively, and increased TBARS content by 8- and 3.6-fold. Results indicated that pork samples with higher catalase and GSH-Px activities would undergo less lipid oxidation, and the accelerated lipid oxidation in salted pork may be partly related to a decrease in GSH-Px activity.     

The physicochemical and microbiological characteristics of pork jerky in comparison to beef jerky

This study was carried out to compare the physicochemical and microbiological characteristics of beef and pork jerky, prepared from whole muscle of beef semimembranosus (BSM), pork semimembranosus (PSM), pork longissimus dorsi (PLD), and pork psoas major (PPM). The BSM and PSM jerky had higher moisture content, and PPM jerky had lower water activity than other jerky samples during 30 days of storage at 25 °C (P < 0.05). Pork jerky samples had higher lightness value than beef jerky, while PSM jerky had higher pH value than other jerky samples (P < 0.05). The shear force and TBARS values of PPM jerky were higher than those of other jerky samples (P < 0.05). Saturated fatty acid (SFA, %) was significantly higher in the BSM jerky than others, while unsaturated fatty acid (UFA, %) was significantly higher in the PSM and PLD than BSM and PPM jerky samples (P < 0.05). The PPM jerky showed a significant increase in UFA (%) during storage, and a significantly decrease in microbial count after storage of 30 days (P < 0.05).     

Influence of sodium chloride on antioxidant enzyme activity and lipid oxidation in frozen ground pork

Ground pork containing 0–2.0% NaCl was stored at −15 °C for 10 weeks. During storage both thiobarbituric acid reactive substances (TBARS) and lipid peroxides increased with increasing NaCl concentrations. The activity of catalase (CAT), glutathione peroxidase (GSH-Px) and Superoxide dismutase (SOD) decreased 8, 32 and 27%, respectively, after 10 weeks of storage. CAT and SOD activity decreased primarily during the first week while GSH-Px activity decreased for up to 4 weeks. To determine if NaCl influenced enzyme inactivation rates, the activity of the antioxidant enzymes from stored, salted (0.5–2.0%) ground pork were determined at equal ionic strengths. Under these conditions, NaCl was not observed to accelerate CAT, SOD and GSH-Px inactivation in ground muscle during storage. However, altering ionic strength (0.5–2.0% NaCl) in the enzymes assays decreased the activity of muscle-extracted CAT, SOD and GSH-Px suggesting that NaCl could alter the activity of these enzymes in salted pork. The ability of NaCl to reduce the activity of the antioxidant enzymes could be partially responsible for the lower oxidative stability of salted muscle foods.     

Antimicrobial packaging of raw beef,pork and turkey using silver‐zeolite incorporated into the material

This study determined the efficacy of silver‐zeolite impregnated into wrapping paper to reduce the bacterial growth on raw beef, pork and turkey cuts. This was compared with that of regular butcher paper. The samples were inoculated with Pseudomonas putida (psychrotrophic spoilage bacterium) and stored on 4% silver‐zeolite and regular butcher paper for up to 4 days at 4 °C and 10 °C. Results showed that P. putida on the beef, pork and turkey samples did not increase in numbers after exposure to all paper packaging at 4 °C during the 4 days of storage. At 10 °C storage temperature, logarithmic growth patterns for the organisms were seen on all paper packaging. However, the growth rate was slower for the organisms on the silver‐zeolite paper. Storage on the silver‐zeolite paper accounted for one log cfu/sample mean reduction in viable cell count for the beef, pork and turkey samples when compared with the samples stored on the butcher paper at 3 days.     

A comparison of modified atmosphere and vacuum skin packing for the storage of red meats

The performances of two commercially available packaging systems for prolonging the shelf-life of fresh meat were compared at 1°C and during simulated retail display. Beef and pork loin steaks in modified atmosphere packs (MAP), containing 75% O2 and 25% CO2, developed an initial bright red (beef) or pink (pork) colour, which gradually changed to brownish-red or -pink after 12 days; similar samples in vacuum skin packs (VSP) remained purple-red throughout the storage period. Off-odours developed more rapidly in MAP (8–12 days), possibly due to more extensive growth of Brochothrix thermosphacta and the effects of aerobic conditions on the metabolites of lactic acid bacteria, which predominated in both types of packs. Evidence of rancidity, using thiobarbituric acid assay, was demonstrated in MAP beef after approximately 8 days, but not in VSP. Drip losses in MAP increased after 6 days' storage, but remained generally low in VSP. Physical texture (shear force values of cooked samples) of beef was unaffected by packaging method, but pork in VSP was significantly more tender ( P < 0.001) than in MAP.     

Comparison of indicators of microbial quality of meat during aerobic cold storage

This study was undertaken to evaluate various indicators for the prediction of the microbial quality of pork and beef loins during cold storage at 0 and 4 degrees C under aerobic conditions. Fresh loins of beef and pork were packaged aerobically and stored at 0 +/- 1 degrees C for 22 days and at 4 +/- 1 degrees C for 12 days or until the total plate counts (TPCs) for these loins exceeded 10(8) CFU/ml. During storage, samples were taken periodically for the measurement of TPCs, psychrotrophic bacterial counts, amine contents, volatile basic nitrogen (VBN) values, thiobarbituric acid values, D-glucose contents, L-lactate contents, pH, and electrical conductivity. Correlation coefficients were ca. 0.90 for all indicators except pH and conductivity. However, VBN and D-glucose contents showed the best correlation with bacterial counts at both temperatures for both beef and pork. Therefore, VBN and D-glucose could potentially be used as indicators in predicting the microbial quality of beef and pork during chilled storage under aerobic conditions.