Volatile profiles, lipid oxidation and sensory characteristics of irradiated meat from different animal species

Irradiated meats produced more volatiles and higher 2-thiobarbituric acid reactive substances (TBARS) than nonirradiated regardless of animal species. Irradiation not only produced many new volatiles not found in nonirradiated meats but also increased the amounts of some volatiles found in nonirradiated meats. The amounts of volatiles in aerobically packaged irradiated meats decreased with storage while those of nonirradiated meats increased. TBARS values were the highest in beef loin, followed by turkey breast and pork loin regardless of irradiation, packaging, and storage time. TBARS of meats showed positive correlation with total volatiles, but preference scores between irradiated and nonirradiated were similar.     

Effects of aging time and natural antioxidants on the color, lipid oxidation and volatiles of irradiated ground beef

Beef rounds aged for one, two, or three weeks after slaughtering were ground added with 0.05% ascorbic acid+0.01% α-tocopherol or 0.05% ascorbic acid+0.01% α-tocopherol+0.01% sesamol, placed on Styrofoam trays and wrapped with oxygen-permeable plastic film, and treated with electron beam irradiation at 0 or 2.5kGy. The meat samples were displayed under fluorescent light for 7d at 4°C. Color, lipid oxidation, volatile analysis, oxidation-reduction potential (ORP) and carbon monoxide (CO) production were determined at 0, 3, and 7d of storage. Irradiation increased lipid oxidation of ground beef regardless of their aging time and storage period. As aging time increased lipid oxidation increased. Adding sesamol increased the effectiveness of ascorbate and tocopherol combination in reducing lipid oxidation especially as aging and storage time increased. The redness of beef were decreased by irradiation and adding ascorbic acid and α-tocopherol before irradiation was effective in maintaining the redness of irradiated ground beef over the storage period. The combination of ascorbic acid+α-tocopherol to ground beef was more effective in reducing ORP than adding sesamol. Irradiation increased CO production from all ground beef regardless of aging time or additives treatments. Volatile sulfur compounds produced by irradiation at Day 0 disappeared over the storage period. Alcohol greatly increased in all nonirradiated beef, but volatiles aldehydes only in irradiated control beef. Antioxidant treatments were effective in reducing aldehydes in ground beef during storage.     

Fat Content Influences the Color, Lipid Oxidation, and Volatiles of Irradiated Ground Beef

ABSTRACT:  Ground beef with 10%, 15%, or 20% fat were added with none, 0.05% ascorbic acid + 0.01%α-tocopherol, or 0.05% ascorbic acid + 0.01%α-tocopherol + 0.01% sesamol, and irradiated at 0 or 2.5 kGy. The meat samples were displayed under fluorescent light for 14 d at 4 °C. Color, lipid oxidation, volatiles, oxidation-reduction potential (ORP), and carbon monoxide (CO) production were determined during storage. Irradiation increased lipid oxidation and total volatiles of ground beef regardless of fat contents. Ascorbic acid +α-tocopherol + sesamol treatment was the most effective in reducing lipid oxidation during storage. The production of ethanol in nonirradiated ground beef increased dramatically after 7 d of storage due to microbial growth. Total aldehydes and hexanal increased drastically in irradiated control over the storage period, but hexanal increased the most by irradiation.  L *-values was decreased by irradiation, but increased in all meat regardless of fat contents as storage period increased. Irradiation reduced the redness, but fat contents had no effect on the  a *-value of ground beef. Sesamol lowered, but ascorbic acid +α-tocopherol maintained the redness of irradiated beef up to 2 wk of storage. The yellowness of meat was significantly decreased by irradiation. The reducing power of ascorbic acid +α-tocopherol lasted for 3 d, after which ORP values increased. Irradiation increased CO production regardless of fat content in ground beef. In conclusion, up to 20% fat had no effect on the quality change of irradiated ground beef if ascorbic acid +α-tocopherol was added.     

Carbon monoxide-heme pigment is responsible for the pink color in irradiated raw turkey breast meat

Turkey breast muscles were aerobically or vacuum packaged, irradiated at 0, 2.5, or 5.0 kGy using a Linear Accelerator (electron beam), and stored at 4°C. The CIE color values, reflectance scan, oxidation-reduction potential (ORP), production of gaseous compounds, and lipid oxidation of samples were determined at 0, 1, and 2 weeks of storage. Absorption spectra of sample drips were determined at 1 week of storage. Irradiation increased the a-value of both aerobically and vacuum-packaged turkey breast, but vacuum-packaged meat had stronger intensity than the aerobically packaged. The increased redness in vacuum-packaged meat was stable during the 2 weeks of storage. The production of CO in meat, which can bind to myoglobin as a sixth ligand, was proportional to irradiation dose. The ORP was decreased by irradiation, but was increased during storage. The ORP and lipid oxidation values were lower in vacuum-packaged than those in aerobically packaged turkey breast. Therefore, increased a-values in irradiated turkey breast should be caused by the decreased ORP and heme pigment-CO ligand formation. The absorption spectra of meat drip also showed that the peak wavelengths of irradiated turkey breast were similar to that of the CO-myoglobin.     

Effect of Antioxidant Application Methods on the Color, Lipid Oxidation, and Volatiles of Irradiated Ground Beef

ABSTRACT:  Four antioxidant treatments (none, 0.05% ascorbic acid, 0.01%α-tocopherol + 0.01% sesamol, and 0.05% ascorbic acid + 0.01%α-tocopherol + 0.01% sesamol) were applied to ground beef using either mixing or spraying method. The meat samples were placed on Styrofoam trays, irradiated at 0 or 2.5 kGy, and then stored for 7 d at 4 °C. Color, lipid oxidation, volatiles, oxidation-reduction potential (ORP), and carbon monoxide (CO) production were determined at 0, 3, and 7 d of storage. Irradiation increased lipid oxidation of ground beef with control and ascorbic acid treatments after 3 d of storage. α-Tocopherol + sesamol and ascorbic acid +α-tocopherol + sesamol treatments were effective in slowing down lipid oxidation in ground beef during storage regardless of application methods, but mixing was better than the spraying method. Irradiation lowered L *-value and a *-value of ground beef. Storage had no effect on lightness but redness decreased with storage. Ascorbic acid was the most effective in maintaining redness of ground beef followed by ascorbic acid +α-tocopherol + sesamol. Irradiation and storage reduced the b *-value of ground beef. Irradiation lowered ORP of ground beef regardless of antioxidants application methods, but ORP was lower in beef with mixing than spraying method. Beef sprayed with antioxidants produced more hydrocarbons and alcohols than the mixing application, but ascorbic acid +α-tocopherol + sesamol treatment was effective in reducing the amount of volatiles produced by irradiation. Therefore, mixing was better than the spraying method in preventing lipid oxidation and maintaining color of irradiated ground beef.     

Temperature abuse affects the quality of irradiated pork loins

The influence of temperature abuse on the quality of irradiated pork loins was investigated. Pork loins were obtained directly from a local packing plant, sliced and vacuum-packaged. Pork loins were randomly separated into 3 groups, sliced, and assigned to receive 0, 1.5, or 2.5 kGy electron-beam irradiation. Then, each chop was further cut into three equal pieces and assigned to three temperature treatments: Trt I was placed in a refrigerator directly after irradiation; Trt II was left at room temperature for 3 h before refrigeration; and Trt III was exposed at room temperature for 1 h three consecutive days with intermittent storage at 4 °C between exposures. Before irradiation, each loin pieces were vacuum-packaged. Color, 2-thiobarbituric acid reactive substances (TBARS), and volatiles were measured after 0, 14, 28 and 42 days of storage, and water-holding capacity and sensory characteristics of the loins were measured after 0, 14 and 28 days of storage. Temperature abuse had no significant effect on color, oxidation, and volatiles of irradiated pork loins. However, temperature abuse improved water-holding capacity of meat, which could be caused by the accelerated hydrolysis of muscle proteins at higher temperature. Irradiation increased redness, sulfur contents in volatiles and off-odor of pork loin. Off-odor and redness induced by irradiation sustained during storage. Among sulfur compounds, the content of dimethyl disulfide decreased gradually while the level of thiourea remained relatively constant. Irradiation also increased water loss, which might be related to the structural damage in membrane during irradiation. This study shows that temperature abuse has little effect on the quality of irradiated pork.     

Decolouration and lipid oxidation changes of vacuum-packed Iberian dry-cured loin treated with E-beam irradiation (5 kGy and 10 kGy) during refrigerated storage

The effect of irradiation (0, 5 and 10 kGy) on the oxidative and colour stability of vacuum-packed Iberian dry-cured loin slices from pigs fed on concentrate feed (CON) or free-range reared (FRG) stored under refrigerated storage was studied. Irradiation treatment increased lipid oxidation, measured as TBA-RS values and hexanal content of dry-cured loins. It also increased redness (CIE a) and lightness (CIE L) of dry-cured loins. Refrigerated storage reduced the differences due to irradiation treatment of instrumental colour values like lightness. However, the decrease of redness during storage was more marked in irradiated than in non-irradiated dry-cured loin. Storage increased differences in TBA-RS values between irradiated and non-irradiated FRG dry-cured loin, while the opposite trend was found for CON dry-cured loins. In addition, no differences in the hexanal content were found after 30 days of refrigerated storage. Therefore, the storage of Iberian dry-cured loin in absence of oxygen by using a vacuum packaging could be an adequate method to reduce changes associated to irradiation treatment in Iberian dry-cured loin.

Industrial relevance

Iberian dry-cured loin is a high sensory quality meat product with increasing projection in external markets Irradiation has shown to be an effective method to control pathogen and spoilage microorganisms in meat and meat products. However, e-beam irradiation can promote colour and oxidation changes that could modify their sensory characteristics. The study aimed the evaluation of e-beam irradiation at two levels (5 and 10 kGy) — higher doses than those that could be necessary to control pathogen microorganisms in this kind of product — on colour changes and lipid oxidation at vacuum-packed slices of Iberian dry-cured loin during subsequent extended chilled storage. E-beam treatment induced changes in colour and lipid oxidation in sliced Iberian dry-cured loin immediately after treatment and subsequent refrigerated storage.     

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.     

Mechanisms of Pink Color Formation in Irradiated Precooked Turkey Breast Meat

ABSTRACT: Precooked turkey breast meat was aerobically packaged or vacuum-packaged and irradiated at 0, 2.5, or 5.0 kGy. CIE color, reflectance, oxidation-reduction potential (ORP), gas production, and lipid oxidation were determined at 0, 7, and 14 d. Irradiation increased redness of vacuum-packaged meat, and the redness was distinct and stable under vacuum. Irradiation decreased ORP and produced carbon monoxide (CO). This indicated that the pink color was caused by the heme pigment-CO complex formation. The reflectance of meat and the absorption spectra of myoglobin solution supported the assumption that denatured CO-myoglobin is the pigment in irradiated precooked turkey breast.     

Combination of aerobic and vacuum packaging to control lipid oxidation and off-odor volatiles of irradiated raw turkey breast

Effects of the combination of aerobic and anaerobic packaging on color, lipid oxidation, and volatile production were determined to establish a modified packaging method to control quality changes in irradiated raw turkey meat. Lipid oxidation was the major problem with aerobically packaged irradiated turkey breast, while retaining characteristic irradiation off-odor volatiles such as dimethyl sulfide, dimethyl disulfide, and dimethyl trisulfide was the concern for vacuum-packaged breast during the 10-day refrigerated storage. Vacuum packaging of aerobically packaged irradiated turkey breast meat at 1 or 3 days of storage lowered the amounts of S-volatiles and lipid oxidation products compared with vacuum- and aerobically packaged meats, respectively. Irradiation increased the a-value of raw turkey breast, but exposing the irradiated meat to aerobic conditions alleviated the intensity of redness.     

Raw-meat packaging and storage affect the color and odor of irradiated broiler breast fillets after cooking

Raw breast fillets were divided into two groups and either vacuum or aerobically packaged. The fillets in each group were subdivided equally into two groups and then irradiated at 0 or 3 kGy using a Linear Accelerator. After 0, 3 and 7 days of storage at 4?°C, fillets were cooked in an 85?°C water bath (cook-in-bag) to an internal temperature of 74?°C. Oxidation-reduction potential (ORP) of raw fillets was measured before cooking, and color and sensory characteristics were analyzed after cooking. Irradiation decreased the ORP of meat, but the potential in aerobically packaged fillets increased during storage. After cooking, color a*-value of irradiated fillets was higher than that of the non-irradiated. Irradiation of raw meat also changed color L* and b* values after cooking. Aerobic storage reduced the redness of cooked meat induced by irradiation. Irradiated raw broiler fillets stored for 0 day and 3 day under aerobic conditions before cooking produced a oxidized chicken-like odor. The odor, however, disappeared after 7 days of storage under aerobic conditions before cooking. For raw broiler samples stored under vacuum conditions, significant differences in color and odor between irradiated and non-irradiated fillets remained throughout the 7-day storage period after cooking. Irradiation had only a minor influence on lipid oxidation of raw breast fillets as indicated by low TBARS values. This study indicates that the effect of irradiation on color and odor of broiler breast fillets after cooking can be reduced significantly through shelf-display of raw fillets under aerobic conditions. Storage under vacuum conditions before cooking is not effective in reducing irradiation-induced changes in the color and odor of breast fillet after cooking.     

Effect of electron-beam irradiation before and after cooking on the chemical properties of beef, pork, and chicken

Ground beef, pork, and chicken thigh meats were irradiated at 0 or 5.0kGy before and after cooking and then stored at -40°C in oxygen permeable bags. The pH, lipid oxidation, volatiles, and carbon monoxide production of the meat were determined at 0 and 6months of storage. The pH values of raw meats from different animal species were different (5.36-6.25) and were significantly increased by cooking, irradiation, and storage (p<0.05). Irradiation had no effect on the TBARS values of ground beef and pork, but significantly increased the TBARS of chicken thigh meat. Cooking, whether it was done before or after irradiation, caused significant increase in TBARS and was most significant in chicken and pork. The numbers of volatiles analyzed by GC/MS were higher in irradiated meats than the non-irradiated ones regardless of meat source. Sulfur-containing compounds were newly produced or increased by irradiation, but dimethyl disulfide and dimethyl trisulfide were not detected in the non-irradiated meats regardless of cooking treatment. Irradiation time, whether done before or after cooking, had little effect on the TBARS, volatiles, and carbon monoxide production in the meat.     

Effect of dietary vitamin E and irradiation on lipid oxidation, color, and volatiles of fresh and previously frozen turkey breast patties

Turkey breast meat patties, prepared from the turkeys fed diets containing 0, 50, 100, or 200 IU of dl-α-tocopheryl acetate (TA) per kg diet from 84 to 112 days of age, were aerobically packaged and irradiated at 0, 1.5, or 2.5 kGy. When dietary TA was increased from 0 to 200 IU/kg diet, plasma and muscle vitamin E levels increased by 5- and 4-fold, respectively. Dietary TA at 100 IU/kg diet significantly improved the storage stability of turkey breast, and it was more distinct in irradiated than nonirradiated meats. Both irradiation and dietary TA increased a*-values of turkey breast meat, but irradiation had a stronger impact. The redness of meat decreased during the 7-day storage, but irradiated meat maintained redder color than nonirradiated. Irradiated meat produced more sulfur volatiles and aldehydes than nonirradiated meats, and dietary TA effectively reduced these compounds during storage. The effects of dietary TA on the reduction of off-odor volatiles were more distinct in previously frozen-stored meats than in fresh meats.     

Colour and lipid oxidation changes in dry-cured loins from free-range reared and intensively reared pigs as affected by ionizing radiation dose level

The effect of irradiation (0, 5 and 10 kGy) of vacuum-packaged Iberian dry-cured loin slices from pigs fed on concentrate (CON) or free-range reared (FRG) was studied in relation to colour changes, TBA-RS and hexanal content. Both, ionizing radiation and type of loin had a significant effect on the instrumental colour parameters of the samples. Irradiation resulted in significantly higher a*-values in both sets of loins, indicating a redder colour. Numerically calculated total colour difference (ΔE) changes were significantly less intense in CON vacuum-packaged dry-cured loin slices than in FRG samples and changed significantly at 10 kGy dose levels in both types of samples. TBA-RS numbers were significantly affected by irradiation dose and type of loin and increased linearly with dose in both types of slices. Increments in TBA-RS numbers in FRG loin slices was dose-dependent and was closely related to the type of dry-cured loin. Irradiation of dry-cured loin slices significantly increased hexanal contents in both groups of loins and the increases were dose-dependent and greater in FRG samples than in CON samples. Differences in the characteristics of the raw material and initial lipid oxidation level could play an important role in the irradiation-induced changes in vacuum-packaged dry-cured loin slices.     

Protein quality and microbiological changes in aerobically- or vacuum-packaged, irradiated fresh pork loins

The effect of gamma-irradiation on the physicochemical, organoleptic and microbiological properties of pork was studied, during 43 days of storage at 4±1°C. Irradiation treatments were carried out under air or vacuum packaging on fresh pork loins at a dose of 6 kGy, at two different dose rates: 2 kGy/h and 20 kGy/h. The loins were evaluated for protein sulphydryl content and emulsifying capacity, surface hydrophobicity of proteins and sensorial evaluation. Regardless of the type of packaging and dose rate of irradiation, all irradiated pork samples were effectively prevented from bacterial spoilage for at least 43 days. Meat redness and texture of irradiated loins were relatively well preserved during the storage period, especially when samples were stored under vacuum. Overall, the physicochemical and organoleptic changes in pork loins appeared to be relatively little affected by the 6 kGy dose. No marked changes in emulsifying capacity and protein sulphydryl content of proteins were noted throughout the storage period. However, the hydrophobicity was reduced (P?0.05) by the faster dose rate of irradiation and by longer storage.     

Effect of Low Dose Irradiation of Pork Loins on the Microflora, Sensory Characteristics and Fat Stability

The effects of low dose (100 krad) irradiation on microflora, sensory characteristics, and development of oxidative rancidity of vacuum packaged pork loins was investigated after irradiation and during low temperature (4°C) storage up to 21 days. Irradiation reduced numbers of mesophiles, psychrotrophs, anaerobic bacteria (P<0.01), and staphylococci (P<0.05), with the effect on mesophiles and psychrotrophic spoilage organisms the greatest. Effect of irradiation on sensory characteristics of pork loin was minimal with no detectable differences between irradiated and nonirradiated pork after 14 days of storage. Irradiation of pork did not affect cooking loss or thiobarbituric acid values.     

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.     

Effects of Ascorbic Acid and Antioxidants on the Color of Irradiated Ground Beef

Irradiation significantly decreased the redness of ground beef (P < 0.05), and the visible color of beef changed from a bright red to a green/brown, depending on the age of meat. Addition of ascorbic acid (0.1%, wt/ wt) in ground beef prior to irradiation prevented color changes in irradiated beef, and the effect of ascorbic acid became greater as the age of meat or storage time after irradiation increased. Ground beef with added ascorbic acid had significantly lower oxidation‐reduction potential than the control (P < 0.05), and the low oxidation‐reduction potential of meat helped maintain the heme pigments in reduced form. Sesamol +α‐tocopherol had no effect in stabilizing color of irradiated beef.     

Effect of vitamin E, low dose irradiation, and display time on the quality of pork

A 4×2×3 factorial experiment was designed to investigate the effect of supplemental vitamin E (0, 100, 200, and 300 mg/kg feed), irradiation and days in display on quality characteristics of aerobically packaged ground pork and vacuum packaged loin chops. Color, thiobarbituric acid reactive substances (TBARS), olfactory and sensory characteristics were evaluated. Samples held in display for 3 d were used for sensory evaluation. In the ground pork, irradiation (1.9 kGy) increased "wetdog" flavor, increased a(*) (redness) and decreased L(*) (lightness) and b(*) (yellowness) values but had no effect on TBARS. However, as display time (0, 4, and 8 days) increased; the differences in a(*) values diminished and putrefying and fishy odors were higher in non-irradiated samples than irradiated. Supplemented vitamin E had no effect on TBARS, odor, and color measures; but increased the juiciness of ground pork regardless of irradiation. Similarly, in the loin chops, irradiation (1.5 kGy) increased a(*) value and "wetdog" flavor; but decreased b(*) value regardless of vitamin E supplementation. Also, irradiation reduced putrefying, and fishy odors during longer display times. TBARS increased with increased display time but was not affected by vitamin E supplementation. These results indicate that in aerobically packaged ground pork and vacuum packaged loin chops, radiolytic odors and color changes cannot be mediated with vitamin E supplementation. Display time and irradiation are significant in determining color and odor changes.     

Lipid Oxidation, Volatiles, and Color Changes in Irradiated Raw Turkey Breast During Frozen Storage

ABSTRACT: Raw turkey breasts were aerobically or vacuum-packaged, irradiated with a linear accelerator, and frozen for 0, 1.5, or 3 mo. Lipid oxidation, volatiles, color values, gas production, and oxidation-reduction potential of the samples were determined. Irradiation produced off-odor volatiles associated with lipid oxidation and sulfur-volatiles; the off-odor was much higher in aerobic packaging. Volatiles increased with irradiation dose, aerobic packaging, and storage time. Irradiation increased stable pink color with both aerobic and vacuum-packaging. Irradiation increased the production of carbon monoxide (CO) and reducing property, indicating that CO-myoglobin could be responsible for the pink color. Lipid oxidation and color changes were not related in irradiated frozen turkey.