PROCESSING AND PRODUCTS

Transcription

1 PROCESSING AND PRODUCTS Effect of Dietary Vitamin E on the Oxidative Stability, Flavor, Color, and Volatile Profiles of Refrigerated and Frozen Turkey Breast Meat 1 B. W. SHELDON,*,,2 P. A. CURTIS,* P. L. DAWSON, and P. R. FERKET *Departments of Food Science and Poultry Science, North Carolina State University, Raleigh, North Carolina , and Department of Food Science, Clemson University, Clemson, South Carolina ABSTRACT In this study, the effect of varying dietary vitamin E levels on the oxidative stability, flavor, color, and volatile profiles of refrigerated and frozen turkey breast meat was examined. Nicholas turkey toms were reared on diets containing vitamin E levels as dl-atocopheryl acetate equivalent to the NRC recommendations (12 and 10 IU/kg from 0 to 8 and 9 to 18 wk, respectively) and 5, 10, and 25 the NRC diet. Two other diets were evaluated and included feeding the NRC diet until 15 and 16 wk followed by a diet containing 20 the NRC vitamin E level. All turkeys were processed in a commercial turkey processing plant and breast meat scored for color. Breast meat was excised from four carcasses per treatment and evaluated after refrigeration (1 and 7 d) or frozen storage (30, 90, 150 d) for oxidative stability and sensory quality by TBA analysis, descriptive flavor profiling, and headspace gas Received for publication July 22, Accepted for publication November 6, Paper number FSR96-16 of the Journal Series of the Department of Food Science, North Carolina State University, Raleigh, North Carolina The use of trade names in this publication does not imply endorsement by the North Carolina Agricultural Research Service or criticism of similar ones not mentioned. 2To whom correspondence should be addressed. chromatography. The TBA values were inversely related to the dietary vitamin E levels. Refrigerated samples had TBA values 78 to 88% lower for the 10 and 25 vitamin E treatments, respectively, than for the NRC control treatment. No differences in TBA values (refrigerated samples) were detected for the 10, 25, and 20 (3 wk feeding duration) or across all treatments for samples frozen for 5 mo. The 10 and 25 NRC diets produced the most typical and acceptable turkey meat flavors with the fewest oxidized off-flavor notes for both fresh and frozen samples as opposed to the more oxidized flavor notes detected in the control samples. Mean color scores increased, indicative of less pale meat, as the level and duration of feeding dietary vitamin E increased. These findings showed that varying dietary vitamin E levels significantly influenced the oxidative stability and functionality of turkey breast meat. (Key words: vitamin E, oxidation, turkey breast meat, sensory characteristics, stability) INTRODUCTION The control of lipid oxidation in fresh and further processed meat products continues to be a goal of food scientists and food processors. These efforts are driven by the fact that lipid oxidation in fresh, processed, and cooked muscle food systems is often associated with product quality deterioration in the form of generating off-odors and flavors that are often described as stale, rancid, or warmed-over in the case of precooked and reheated meat products (Einerson and Reineccius, 1977; Bailey et al., 1980). Previous studies have shown that poultry diets supplemented with vitamin E produce birds that have greater carcass lipid stability and better quality characteristics (Webb et al., 1972; Marusich et al., 1975; Bartov 1997 Poultry Science 76: and Bornstein, 1977). Variations in vitamin E deposition in fatty tissues have been found between different poultry species (Mecchi et al., 1953). For example, Marusich et al. (1975) found that concentrations of tocopherol in turkey liver and breast muscle were only one-fifth to one-third, respectively, those of broilers fed similar dietary levels. In a more recent study in which female turkey poults were fed elevated dl-a-tocopheryl acetate levels over the last 3 wk prior to slaughter, tocopherol levels were 100 to 600% higher in thigh meat than in breast or skin and subcutaneous fat (Sheldon, 1984). When expressed on a per unit of fat basis, breast tissues had higher concentrations of tocopherol than thigh tissues, yet both tissue types had similar oxidative stabilities. These variations in oxidative stability and vitamin E levels among tissues were thought to be related to differences in the vascular network among tissues, lipid concentration and fatty acid profile, and degree of physical activity exerted by the different muscle groups (Sheldon, 1984). Poultry diets are often supplemented with rendered poultry fat that contains highly unsaturated fatty acids. An increase in the degree of unsaturation of carcass fat of broilers and turkeys due to dietary unsaturated fat 634

2 VITAMIN E EFFECTS ON TURKEY BREAST MEAT QUALITY 635 supplements decreases the carcass lipid stability. Under such conditions, vitamin E supplementation, even at elevated levels, is not always effective in stabilizing these tissues from oxidation reactions (Bartov and Bornstein, 1981). One of the rising concerns of the industry regarding turkey breast meat functionality is a condition similar to pale, soft, exudative (PSE) pork meat. This condition causes problems with the texture, cohesiveness, color, and juiciness of processed turkey breast meat. This PSElike condition, which has been observed to affect as much as 40% of a market tom flock, is thought to be related to anaerobic muscle metabolism and growth alterations in the musculoskeletal system (i.e., focal myopathy) (Sosnicki et al., 1988a,b; 1989, 1991a,b; Sosnicki and Wilson, 1991, 1992; Cherel et al., 1992). Histopathological observations by M. D. Ficken (1996, College of Veterinary Medicine, North Carolina State University, Box 8401, Raleigh, NC , personal communication) indicate that PSE-like breast meat has muscle fibrils rupturing out of the muscle fiber bundles, which is unlike PSE in pork meat. In turkeys, PSE seems to be related to poor cell membrane or collagen connective tissue integrity. Like pork PSE, this PSE-like problem in turkey breast meat is likely from stresssusceptible turkeys. Poor membrane integrity (PSE-like meat) in stresssusceptible turkeys could be ameliorated by a surfeit of dietary vitamin E. Schanus et al. (1981) observed a deficiency of the antioxidant enzyme, glutathione (GSH)-peroxidase in stress-susceptible pigs. He postulated that PSE was consistent with an antioxidant disorder leading to oxidative damage of cell membranes. Both stress-susceptible pigs and vitamin E-deficient animals have elevated activities of pyruvate kinase and creatine kinase in plasma and increased erythrocyte lysis due to free radical mediated damage to cell membranes (Duthrie et al., 1987). With this in mind, the intent of this study was to determine whether dietary vitamin E supplementation had an effect on the incidence and severity of PSE-like breast meat in turkeys. The objective of this present study was to evaluate the effects of feeding supplemental vitamin E at concentrations significantly above the NRC requirements on the oxidative stability, quality, and color (PSE-like condition) of turkey breast tissues. The findings presented in this manuscript represent part of a more comprehensive study (Ferket, unpublished data) that sought to determine the effect of increased dietary levels of vitamin E on the performance, immune function, and carcass yield of commercial market turkey toms. Breast meat was chosen for analysis due to its higher economic value relative to dark meat tissues, lower overall vitamin E deposition rates than dark meat, and its greater susceptibility to oxidation than dark meat tissues, which is attributed to its higher ratio of unsaturated phospholipids. TABLE 1. Experimental vitamin E dietary treatments and design 1 Treatment 0 to 8 wk 9 to 18 wk (IU vitamin E/kg feed) 1 NRC NRC NRC NRC Age period Vitamin E level 520 NRC 16 to 18 wk NRC 15 to 18 wk 200 1Turkey strain: Nicholas males, completely randomized block design with 2 blocks, 6 replicate pens per treatment, and starting with 18 poults per pen. MATERIALS AND METHODS Nicholas turkey toms were reared on a commercial feeding program in which the diets contained vitamin E levels as dl-a-tocopheryl acetate that corresponded to NRC (1984) recommendations, and 5, 10, and 25 the NRC vitamin E recommendations (Table 1). Two other treatment groups were raised on diets containing the NRC recommended level of vitamin E until 15 and 16 wk of age, respectively, and then fed supplemental vitamin E at a level of 20 the NRC through 18 wk of age. This feeding of elevated vitamin E concentrations (200 IU/kg) during the last 2 and 3 wk before processing was done to evaluate the effect of feeding excess vitamin E concentrations for shorter durations on breast meat quality and changes in flavor characteristics during storage. The feeding program and basal diet formulations used were formulated by P. R. Ferket. All toms were raised according to standard commercial practices in a 48-pen curtain-sided facility. Each pen contained a tube feeder and Placon water fount to provide feed and water for ad libitum consumption. Each treatment was assigned to six replicate pens containing 18 birds with a stocking density of m2 per bird. At 1 d of age, the birds were placed in the pens containing used litter without new shavings placed on top. The used litter was from a previous flock that was challenged with Eimeria adenoides, Eimeria gallapovonis, and Eimeria meleagramitis. Therefore, the poults received a natural challenge of coccidia and other microbes upon placement. A coccidiostat was not included in the prestarter feed to accentuate the coccidia challenge. All turkeys were slaughtered in a commercial turkey processing plant using standard processing procedures. Refrigerated Turkey Meat Study Breast meat (Pectoralis major and Pectoralis minor muscles) was excised from four carcasses per dietary treatment, vacuum-sealed in commercial bags, and evaluated after 1 or 7 d of refrigeration (4 C) (one carcass per replicate per treatment was randomly selected from among the six treatment replicates). Half of the breast tissue from each carcass was used for sensory evaluation

3 636 and the other half for 2-thiobarbituric acid (TBA) analysis and headspace gas chromatography. The tissues were analyzed in duplicate for oxidative stability by the TBA distillation assay as outlined by Yu and Sinnhuber (1967) and headspace volatiles by gas chromatography (Sheldon, 1984; Wu and Sheldon, 1988). Duplicate 2-g samples of ground turkey breast meat were weighed into a 5-mL Perkin Elmer3 headspace vial and sealed using a teflon-lined silicon septum. The vial was heated at 90 C for an equilibration time of 30 min. A 30- and 15-s vial pressurization and injection time, respectively, were employed. The volatiles were injected and separated on a Perkin Elmer Model HS-6 Headspace Sampler3 interfaced to a Varian Model 3700 dual-flame gas chromatograph.4 A 30-M mm i.d. bonded phase fused silica capillary column coated with DB-55 to a film thickness of 1-m was used for separation. The column inlet pressure was 138 kpa helium with an injection split ratio of 10:1 and a flow rate of 9.1 ml/min at 20 C. The column was temperature-programmed from 20 to 250 C at 10 C/min with a final 5-min hold time. Injector and detector temperatures were 250 and 300 C, respectively. Detector signals were integrated with a Waters6 820 chromatography data station. Volatile peak areas were normalized to a dry meat weight basis. Sensory evaluation of turkey breast meat (four carcasses per treatment per sampling time) was accomplished using a descriptive analytical flavor profiling method described by Cairncross and Sjostrom (1950). An eight-member professional flavor profile panel evaluated the flavor (aroma and taste) of cooked ground turkey meat for all treatments. The panelists are able to detect, describe, define, and quantify aroma and taste descriptors relative to a reference standard (cooked, fresh turkey breast meat) that was available at all times in addition to universal reference standards. The panelists underwent two orientation training sessions to familiarize themselves with the product and develop a ballot of cooked aroma and taste descriptors (typical fresh turkey meat aroma and taste, oxidized aroma and taste, and cooked and oxidized aftertaste flavors. Sensory characteristics were individually scored with 14-point scales (1, not detectable to 14, strongly detectable) that measured the intensity of each character note. Turkey samples were ground on the afternoon prior to the day of evaluation using a Model FG-A Kitchen Aid processor7 with grinder attachment and stored in vacuum-sealed Whirlpak bags8 at 4 C. On the following day, 30-g samples per panelist were placed in individual glass baby food jars and covered with foil. The reference 3Perkin-Elmer, Norwalk, CT Varian Corp., Sunnyvale, CA J and W Scientific, Folson, CA Millipore, Waters Chromatography Division, Milford, MA Kitchen Aid, Troy, OH NASCO, Fort Atkinson, WI G. S. Blodgett Co., Inc., Burlington, VT SHELDON ET AL. (fresh, unfrozen and unbasted turkey breast meat was purchased within 1 d of processing from a retail store) and six randomly selected samples (one per treatment) per panelist were cooked in a preheated convection oven9 at 175 C for 12 min. Covered jars were then placed in preheated pans of sand (to retain heat) and taken to the evaluation room. Samples were allowed to cool to 65 C before beginning evaluation. Once panelists had completed the first set of samples, the remaining three sets of samples were each cooked separately and evaluated. Frozen Turkey Meat Study Frozen turkey breast samples (four carcasses per treatment per sampling time) were thawed after 30, 90, and 150 d of frozen storage and analyzed for lipid oxidation using the sensory evaluation, TBA, and headspace volatile procedures as described previously. Breast Muscle Color Scores The incidence and severity of PSE-like breast meat from turkeys fed all the vitamin E treatments were evaluated by comparing the turkey meat to a color score scale developed to qualitatively evaluate PSE in pork. The scores used ranged from 1 (very pale: like PSE-like meat) to 4 (dark: like dark, firm, and dry meat). Color scores of 1 or 4 were associated with poorer meat processing functionality as previously established by Quality Control plant personnel than color scores of 2 and 3. A threemember panel of plant quality control and laboratory technician personnel and one of the authors evaluated and scored the color of freshly excised breast tissues (n = 12 to 35 carcasses per treatment) using a sodium vapor lighting background. Statistical Analysis Where applicable, significant differences between treatments, days, and treatment by day interactions were determined by analysis of variance (P 0.05) and the treatment means separated for each pair using the Student s t test at P 0.05 (SAS Institute, 1990). Data were pooled across days when nonsignificant treatment by day interactions were observed. The residual mean square was used for testing main effects and the treatment by day interaction. RESULTS AND DISCUSSION The TBA values obtained from previously refrigerated and frozen breast meat samples were significantly influenced by the concentration of tocopherol in the diet (Table 2). The TBA values for refrigerated samples were not influenced by days of refrigeration (P > 0.05), and thus were pooled across days. An inverse relationship was observed between TBA values and dietary tocopherol concentrations. Birds fed the 25 NRC diet (Treatment 4) had significantly lower breast (refrigerated) tissue TBA values and thus greater oxidative

4 VITAMIN E EFFECTS ON TURKEY BREAST MEAT QUALITY 637 TABLE 2. Effect of dietary vitamin E on the mean thiobarbituric acid (TBA) values for refrigerated and frozen turkey breast meat 1 Treatments Days (mg TBA/kg meat) Refrigerated ± 0.6 a 0.94 ± 0.6 ab 0.33 ± 0.1 bc 0.18 ± 0.1 c 0.89 ± 0.4 ab 0.64 ± 0.5 bc Frozen 30 d 1.22 ± 0.0 a 1.16 ± 0.3 ab 0.88 ± 0.4 abc 0.77 ± 0.4 abc 0.99 ± 0.4 abc 0.94 ± 0.2 abc 90 d 0.72 ± 0.1 abc 0.71 ± 0.2 abc 0.68 ± 0.4 abc 0.40 ± 0.1 c 0.48 ± 0.0 bc 0.81 ± 0.3 abc 150 d 0.90 ± 0.0 abc 1.02 ± 0.4 abc 0.66 ± 0.4 abc 0.99 ± 0.6 abc 1.10 ± 0.7 abc 1.04 ± 0.0 abc a cmeans ± SD within refrigeration and frozen storage categories with no common superscript differ significantly (P 0.05). 1Treatment 1: NRC dietary vitamin E recommendations; Treatment 2: 5 NRC recommendation; Treatment 3: 10 NRC recommendation; 2Day 1 and Day 7 refrigerated sample means were pooled; n = 4. stability than samples taken from birds fed the NRC and 5 NRC diets (Treatments 1 and 2, respectively). No difference in TBA values were observed between Treatments 3 (10 NRC) and 4 (25 NRC). These TBA values were 78 to 88% lower than the NRC treatment TBA values. Furthermore, birds fed the 20 NRC diet over the last 2 wk prior to slaughter (Treatment 5) had TBA values similar to Treatments 1, 2, 3, and 6. However, birds fed the 20 NRC diet for 3 wk prior to processing had TBA values similar to Treatments 2, 3, 4, and 5. These findings demonstrate a greater oxidative stability in carcass breast tissues sampled from turkeys that received Treatments 3, 4, and 6. The longer the duration for feeding elevated vitamin E levels to turkeys, the greater the protection against lipid oxidation. Following 30, 90, and 150 d of frozen storage, no significant difference in TBA values were found between the six treatments (Table 2). Although not statistically different at the P < 0.05 level, a similar treatment pattern, as observed for refrigerated samples, was also evident in the frozen samples analyzed at 30 d. As previously observed in past studies (Sheldon, 1984), TBA numbers decreased across most treatments after 90 and 150 d of storage in comparison to the 30-d samples. This observation points to the problem of using the TBA assay on samples that have been frozen for long periods of time. It is interesting to note that a similar reduction as detected in TBA numbers was also observed in the concentration of eight volatile aldehydes following 30 d of frozen storage. This result is not unexpected as many compounds that are generated during lipid oxidation, such as aldehydes, undergo further reactions that produce other secondary end products which may not be detectable with the TBA assay. The mean flavor profile panel scores for refrigerated and frozen breast samples are summarized in Tables 3 TABLE 3. Mean sensory scores for turkey breast meat refrigerated for 1 or 8 d Sensory term 2 Treatments 1 ATM AOX FTM FOX TTM TOX 1 Day ± 0.5 c 4.1 ± 1.1 a 3.9 ± 0.9 f 4.5 ± 1.7 a 3.3 ± 0.9 g 3.3 ± 1.1 a Day ± 1.0 abc 3.4 ± 1.2 abcd 4.6 ± 0.6 cdef 4.0 ± 1.0 ab 3.4 ± 0.5 g 3.0 ± 1.4 abc 2 Day ± 1.0 cd 3.6 ± 2.1 abc 4.2 ± 1.2 ef 3.6 ± 1.6 abc 3.6 ± 0.7 efg 3.0 ± 1.2 abc Day ± 0.9 abc 3.9 ± 1.2 ab 4.9 ± 1.0 bcde 4.4 ± 1.1 ab 4.1 ± 0.8 bcde 3.1 ± 1.2 ab 3 Day ± 1.1 cd 3.4 ± 1.5 abcd 4.5 ± 1.2 def 3.7 ± 1.5 abc 3.9 ± 1.0 defg 2.8 ± 1.3 abcd Day ± 1.2 ab 2.8 ± 1.3 cd 5.1 ± 1.1 bcd 2.4 ± 1.4 c 4.7 ± 0.8 ab 1.9 ± 1.1 def 4 Day ± 0.8 ab 1.6 ± 0.8 c 5.9 ± 0.5 a 1.7 ± 1.1 c 4.9 ± 0.8 a 1.4 ± 0.7 f Day ± 1.1 a 1.6 ± 0.7 c 5.6 ± 0.9 ab 1.9 ± 1.1 c 4.6 ± 0.8 abc 1.6 ± 0.5 ef 5 Day ± 0.8 de 3.7 ± 1.2 abc 4.3 ± 0.8 ef 4.1 ± 1.2 ab 3.5 ± 0.8 fg 3.0 ± 1.2 abc Day ± 0.9 abc 2.6 ± 1.2 d 4.9 ± 1.2 bcde 2.7 ± 1.8 cde 4.2 ± 1.0 bcde 2.4 ± 1.6 bcde 6 Day ± 1.3 abc 2.9 ± 1.2 bcd 5.3 ± 1.3 abc 2.5 ± 1.0 de 4.4 ± 1.2 abcd 2.2 ± 1.0 cdef Day ±.9 bcd 3.4 ± 1.3 abcd 4.9 ± 0.7 bcde 3.4 ± 1.7 bcd 4.1 ± 0.8 cdef 2.6 ± 1.4 abcd a gmeans within a flavor category with no common superscript differ significantly (P 0.05). 1Treatment 1: NRC dietary vitamin E recommendations; Treatment 2: 5 NRC recommendation; Treatment 3: 10 NRC recommendation; 2Mean ± SD; ATM, turkey meat aroma; AOX, oxidized meat aroma; FTM, turkey meat flavor; FOX, oxidized meat flavor; TTM, turkey meat aftertaste; TOX, oxidized meat aftertaste; 14-point sensory scale where 1 = not detectable and 14 = strongly detectable; n = 4.

5 638 SHELDON ET AL. TABLE 4. Mean sensory scores for turkey breast meat frozen for 30, 90, or 150 d Sensory term 2 Treatments 1 ATM AOX FTM FOX TTM TOX 1 Day ± 0.8 def 3.4 ± 1.5 ab 4.6 ± 1.1 bcde 3.2 ± 1.47 ab 3.6 ± 1.0 cde 2.6 ± 1.3 abc Day ± 1.0 cd 2.3 ± 0.9 def 4.6 ± 1.2 bcd 2.6 ± 1.2 bcd 3.9 ± 0.8 bcd 2.3 ± 1.0 abcd Day ± 0.8 cdef 2.5 ± 0.6 cde 4.4 ± 0.8 cde 2.1 ± 0.7 cde 3.8 ± 0.4 cd 2.0 ± 0.7 bcdef 2 Day ± 1.1 cdef 2.8 ± 1.3 abcd 4.7 ± 1.1 bcd 2.8 ± 1.2 abc 4.1 ± 0.8 bc 2.1 ± 0.8 abcdef Day ± 0.8 ab 2.2 ± 0.9 defg 4.7 ± 1.1 bc 2.8 ± 0.7 abc 3.8 ± 0.8 cd 2.3 ± 1.0 abcd Day ± 0.6 f 2.5 ± 0.8 cde 4.2 ± 0.7 def 2.3 ± 1.1 cde 3.4 ± 0.8 de 1.8 ± 0.9 def 3 Day ± 1.0 cde 2.4 ± 1.3 cdef 4.9 ± 1.0 abc 2.1 ± 1.3 cde 4.0 ± 0.9 bcd 1.9 ± 0.8 cdef Day ± 0.9 a 1.8 ± 0.7 fg 4.8 ± 1.3 bc 1.9 ± 1.0 de 4.1 ± 1.1 bc 1.7 ± 0.9 def Day ± 0.5 cdef 2.6 ± 1.2 bcde 4.0 ± 0.8 def 2.6 ± 1.0 bcd 3.8 ± 0.8 cde 2.1 ± 0.9 abcdef 4 Day ± 1.1 abc 1.9 ± 1.1 efg 5.6 ± 1.2 a 1.7 ± 1.0 c 4.9 ± 1.0 a 1.6 ± 0.8 ef Day ± 1.1 abc 1.6 ± 0.8 g 5.3 ± 1.2 ab 1.8 ± 0.9 c 4.5 ± 1.1 ab 1.5 ± 0.8 f Day ± 0.9 cde 2.2 ± 0.9 defg 4.6 ± 0.5 bcd 2.4 ± 0.8 cde 3.8 ± 0.5 cd 2.1 ± 0.9 bcdef 5 Day ± 0.7 bcd 2.8 ± 0.9 abcd 4.6 ± 0.7 bcd 2.8 ± 1.0 abc 3.8 ± 0.4 cde 2.3 ± 0.8 abcd Day ± 1.0 abcd 2.2 ± 1.0 defg 4.7 ± 1.1 bc 2.7 ± 1.2 bc 4.0 ± 0.9 bc 2.2 ± 1.2 abcde Day ± 1.0 ef 3.5 ± 0.8 a 3.6 ± 0.8 f 3.5 ± 1.1 a 3.2 ± 0.8 c 2.8 ± 0.8 a 6 Day ± 0.9 cde 3.1 ± 1.1 abc 4.5 ± 1.2 cde 2.8 ± 1.2 abc 4.1 ± 0.9 bc 2.6 ± 1.1 ab Day ± 1.0 a 1.8 ± 0.7 fg 4.7 ± 1.2 bcd 2.8 ± 0.8 abc 4.1 ± 1.1 bc 2.3 ± 0.8 abcd Day ± 0.5 f 2.8 ± 0.9 abcd 3.9 ± 0.5 ef 2.8 ± 1.0 abc 3.4 ± 0.6 de 2.1 ± 0.9 abcdef a gmeans within a flavor category with no common superscript differ significantly (P 0.05). 1Treatment 1: NRC dietary vitamin E recommendations; Treatment 2: 5 NRC recommendation; Treatment 3: 10 NRC recommendation; 2Mean ± SD, n = 4. and 4, respectively. The higher the score, the more intense the aromatic or taste note. In agreement with the TBA values, the panelists perceived more typical and acceptable roasted turkey aromatic notes in samples from Treatments 4 and 6, which were significantly higher than Treatments 2, 3, 5, and 1. The NRC samples had the lowest acceptable turkey meat aromas; these were not different from aromas of Treatment 5. After 8 d of refrigerated storage, Treatments 4 and 6 were significantly different, although no aroma differences were perceived between Treatments 1 through 5 and Treatments 1, 2, 3, 5, and 6. Panelists were able to detect some oxidized aromatic notes after 1 d of refrigerated storage, with no differences detected between Treatments 1, 2, 3, and 5. Treatment 4 consistently produced the most stable refrigerated product in terms of perceived oxidation aromas. No significant day differences (Day 1 vs 8) in oxidized aroma notes were perceived in samples from Treatment 4. A similar treatment pattern, as sensed in the aroma and aftertaste sensory categories, was perceived by the panelists for the typical turkey meat flavor and oxidized flavor categories. Treatments 4 and 6 again produced the most acceptable and typical turkey meat tastes with the fewest oxidized off-notes. This effect was especially evident on Day 1. The NRC diet produced the least acceptable turkey meat flavors and more intense oxidized flavors, which were not different than the oxidized sensory scores for Treatments 2, 3, and 5 on Day 1 and Treatments 2 and 6 on Day 8. After 30 d of frozen storage, samples from turkeys receiving the highest tocopherol levels had significantly more typical turkey meat aromas and less oxidized aromatics than the NRC Treatment (Table 4). Treatments 3 and 4 had the least detectable oxidized aromas in comparison to the other four treatments. To some degree, oxidized aromas were detected in all samples. This same general pattern was also observed in the flavor and aftertaste sensory categories. These findings agree with past studies in that increases in dietary vitamin E levels help to prolong the flavor shelf life of turkey meat products by reducing the degree of lipid oxidation (Sheldon, 1984). The higher the dietary vitamin E concentration and longer the duration of feeding this vitamin, the greater the oxidative lipid stability. The results of varying dietary vitamin E concentrations on individual and total volatile aldehyde concentrations are summarized for refrigerated and frozen breast meat samples in Tables 5 and 6, respectively. Of the eight aldehydes detected, hexanal was present in the highest concentration followed by pentanal. No treatment differences were detected in the individual or total volatile aldehyde concentrations after 1 d of refrigeration. As an indicator of lipid oxidation, 7-d refrigerated samples from Treatments 1 and 2 had significantly higher total aldehyde concentrations in comparison to samples refrigerated for 1 d. Furthermore, 7-d refrigerated samples representing Treatments 3, 4, 5, and 6 had significantly lower total aldehyde concentrations in comparison to samples from Treatments 1 and 2. These findings agree in part with the TBA results and oxidized aroma, flavor, and aftertaste sensory panel scores such that higher aldehyde concentrations directly correlated

6 VITAMIN E EFFECTS ON TURKEY BREAST MEAT QUALITY 639 TABLE 5. Effect of varying dietary vitamin E on the concentration of individual and total aldehydes in turkey breast meat (refrigerated samples) Aldehyde peak area Treatments 1 Pentanal Hexanal 2-Hexenal Heptanal 2-Heptenal Octanal 2-Octenal Nonanal Total 1 Day 1 6,040 b 33,158 abc 344 cde 2,020 ab 498 b 1,850 bc 768 abcd 2,513 abc 47,190 bc Day 7 13,842 a 62,147 a 977 a 3,874 a 4,920 a 3,946 a 1,396 a 3,732 a 94,836 a 2 Day 1 3,563 b 17,190 c 0 g 1,017 b 416 b 920 c 300 cd 1,294 bc 24,699 bc Day 7 13,960 a 59,966 ab 630 b 3,894 a 2,346 ab 3,333 ab 958 ab 3,194 ab 88,281 a 3 Day 1 2,724 b 13,187 c 0 g 920 b 360 b 742 c 165 d 1,048 c 19,145 c Day 7 7,480 ab 32,522 abc 234 ef 2,404 ab 1,470 b 2,360 abc 694 bcd 2,736 abc 49,899 bc 4 Day 1 3,671 b 14,601 c 94 fg 1,021 b 322 b 875 c 220 d 1,116 c 21,919 bc Day 7 5,606 b 22,133 c 518 bc 1,751 ab 1,128 b 1,629 bc 855 abc 2,143 abc 35,764 bc 5 Day 1 6,066 b 28,678 bc 276 def 2,103 ab 737 b 1,884 bc 486 bcd 2,270 abc 42,500 bc Day 7 8,632 ab 34,337 abc 479 bcd 2,259 ab 1,257 b 1,996 bc 960 ab 1,938 abc 51,858 b 6 Day 1 3,414 b 16,262 c 104 fg 1,090 b 365 b 1,015 c 244 cd 1,428 bc 23,922 bc Day 7 6,137 b 23,980 c 375 cde 1,897 ab 1,296 b 1,702 bc 778 abcd 1,782 abc 37,949 bc a gmeans within columns with no common superscript differ significantly (P 0.05); n = 4. 1Treatment 1: NRC dietary vitamin E recommendations; Treatment 2: 5 NRC recommendation: Treatment 3: 10 NRC recommendation; with higher TBA numbers and more perceivable oxidized off-flavors and aromas. Although oxidized flavors among treatments were detected by the panelists after only 1 d of refrigeration, these treatment differences were not reflected in the individual or total aldehyde concentrations. This finding is not unexpected because it has been firmly established that meat aromas and flavors are not composed of just aldehydes but complex mixtures of many different classes of volatile and nonvolatile compounds (Ramaswamy and Richards, 1982). Few treatment differences were observed within and across sampling days for individual or total aldehydes detected in frozen breast meat samples. The effect of level of dietary vitamin E supplementation in breast meat color score and score distribution is summarized in Table 7. Mean color score significantly increased as the level of dietary vitamin E increased. Moreover, a greater proportion of meat with a low color score was observed from birds fed the NRC (Treatment 1) and 5 NRC (Treatment 2) levels of vitamin E than TABLE 6. Effect of varying dietary vitamin E on the concentration of individual and total aldehydes in turkey breast meat (frozen samples) Aldehyde peak area Treatments 1 Pentanal Hexanal 2-Hexenal Heptanal 2-Heptenal Octanal 2-Octenal Nonanal Total 1 Day 30 3,892 abcd 19,600 abcd 158 1,281 abc 376 abc 2,110 a 197 ab 1,577 abcd 29,190 ab Day 90 2,800 abcd 14,980 abcd 0 1,128 abc 336 abc 796 bcd 0 b 1,126 abcd 21,166 ab Day 150 3,171 abcd 16,056 abcd 118 1,123 abc 383 abc 1,042 abcd 130 ab 1,268 abcd 23,290 ab 2 Day 30 4,811 abcd 22,402 abc 0 1,505 abc 477 abc 1,508 abcd 359 ab 1,709 abc 32,772 ab Day 90 3,170 abcd 16,156 abcd abc 314 abc 824 bcd 0 b 1,074 bcd 22,394 ab Day 150 4,926 abc 20,252 abcd 127 1,506 abc 497 abc 1,430 abcd 364 ab 1,688 abc 30,792 ab 3 Day 30 3,012 abcd 14,358 abcd abc 329 abc 936 abcd 118 ab 1,500 abcd 21,160 ab Day 90 2,115 cd 11,012 bcd bc 172 c 743 bcd 0 b 1,025 bcd 15,802 ab Day 150 3,998 abcd 18,615 abcd 0 1,260 abc 430 abc 1,163 abcd 114 ab 1,502 abcd 27,083 ab 4 Day 30 1,694 cd 8,654 cd c 197 bc 529 cd 0 b 732 cd 12,319 ab Day d 4,940 d c 0 c 353 d 0 b 564 d 6,982 b Day 150 3,452 abcd 15,010 abcd abc 276 abc 866 bcd 158 ab 1,026 bcd 21,844 ab 5 Day 30 3,975 abcd 19,222 abcd 0 1,266 abc 469 abc 1,313 abcd 221 ab 1,659 abc 28,125 ab Day 90 2,199 bcd 11,610 abcd c 298 abc 646 bcd 0 b 882 cd 16,284 ab Day 150 6,608 a 27,470 a 73 2,041 a 738 a 1,844 ab 347 ab 1,996 ab 41,116 a 6 Day 30 2,734 abcd 13,102 abcd bc 336 abc 903 abcd 130 ab 1,402 abcd 19,404 ab Day 90 1,736 cd 8,409 cd c 216 bc 590 cd 0 b 788 cd 12,336 ab Day 150 6,261 ab 26,198 ab 110 1,857 ab 692 ab 1,728 abc 400 a 2,194 a 39,442 a a dmeans within columns with no common superscript differ significantly (P 0.05); n = 4. 1Treatment 1: NRC dietary vitamin E recommendations; Treatment 2: 5 NRC recommendation: Treatment 3: 10 NRC recommendation;

7 640 SHELDON ET AL. TABLE 7. Effect of dietary vitamin E supplementation on breast muscle color score of 18-wk-old turkey toms Color score distribution 1 Dietary vitamin E level Mean color score ± SE n NRC 2.12 ± 0.11 c NRC 2.36 ± 0.20 bc NRC 2.33 ± 0.19 bc NRC 2.78 ± 0.12 a NRC, 16 to 18 wk 2.67 ± 0.19 ab NRC, 15 to 18 wk 2.54 ± 0.11 ab a cmean color score values with no common superscript differ significantly (P < 0.05). 1Color score distribution is expressed as a percentage of the number of sampled birds (n). Subjective scores: 1 = very pale; 2 = pale; 3 = dark; 4 = very dark. Color scores of 1 or 4 are associated with poor meat processing functionality. (%) from birds fed higher levels of vitamin E. The incidence of pale meat decreased even when 200 IU vitamin E/kg was fed during the last 2 to 3 wk before slaughter (Treatments 5 and 6); the longer high dietary vitamin E was fed, the lower the incidence of very pale meat. These results suggest that a surfeit of dietary vitamin E may reduce the incidence of PSE-like breast meat in turkeys, even if high vitamin E (200 IU/kg) was fed 3 wk before slaughter. Further study is warranted in relating vitamin E supplementation level and PSE-like breast meat in turkeys. The findings from these analyses demonstrate that varying dietary vitamin E concentrations can influence the oxidative stability and muscle functionality of turkey breast tissues. It is apparent that the NRC recommended dietary vitamin E levels produce turkey breast meat tissues that are more prone to oxidation than breast meat tissues taken from turkeys that received elevated dietary tocopherol levels. However, it must further be noted that the economics of implementing one or more of these experimental diets into the nutritional program of turkey producers must be considered in light of any potential benefits. It is hypothesized that feeding high level vitamin E supplements throughout the production cycle is not cost-effective (about $2.00/ton). The costbenefit relationship of feeding high vitamin E (200 to 300 IU/kg) for the last three weeks before slaughter requires more evaluation before it can be recommended for practice. However, the associated benefits in meat processing functionality (reduced PSE-like incidence) and improved flavor stability may make this alternative cost-effective. REFERENCES Bailey, M. E., H. P. Dupuy, and M. G. Legendre, Undesirable meat flavor and its control. Page 31 in: The Analysis and Control of Less Desirable Flavors in Foods and Beverages. G. Charalambous, ed. Academic Press, Inc., New York, NY. Bartov, I., and S. Bornstein, Stability of abdominal fat and meat of broilers: The interrelationship between the effects of dietary fat and vitamin E supplements. Br. Poult. Sci. 56: Bartov, I., and S. Bornstein, Stability of abdominal fat and meat of broilers: Combined effect of dietary vitamin E and synthetic antioxidants. Poultry Sci. 60: Cairncross, S. E., and L. B. Sjostrom, Flavor profiles a new approach to flavor problems. Food Technol. 4(8): Cherel, Y., M. Wyers, and M. Dupas, Histopathological alterations of turkey muscles at the slaughterhouse. Pages in: Proceedings of the 19th World s Poultry Congress. Vol. 3. Amsterdam, The Netherlands. Duthrie, G. G., J. R. Arthur, C. F. Mills, P. C. Morrice, and F. Nicol, Anomalous tissue vitamin E distribution in stress susceptible pigs after dietary vitamin E supplementation and effects on pyruvate kinase and creatine kinase activities. Livestock Prod. Sci. 17:169. Einerson, M. A., and G. A. Reineccius, Inhibition of warmed-over flavor in retorted turkey by antioxidants formed during processing. J. Food Proc. Pres. 1: Marusich, W. L., E. DeRitter, E. F. Ogrinz, J. Keating, M. Mitrovic, and R. H. Bunnell, Effect of supplemental vitamin E in control of rancidity in poultry meat. Poultry Sci. 54: Mecchi, E. P., M. F. Pool, and A. A. Klose, The role of tocopherol content in the stability of chicken and turkey fats. Poultry Sci. 32:915. (Abstr.) National Research Council, Nutrient Requirements of Poultry. 8th rev. ed. National Academy Press, Washington, DC. Ramaswamy, H. S., and J. F. Richards, Flavor of poultry meat a review. Can. Inst. Food Sci. Technol. J. 15:7 20. SAS Institute, SAS/STAT User s Guide: Statistics. Release SAS Institute Inc., Cary, NC. Schanus, E. G., F. Schendel, R. E. Lovriln, W. E. Rempel, and C. McGrath, The Red Cell: Fifth Ann Arbor Conference. Alan R. Liss, Inc., New York, NY. Sheldon, B. W., Effect of dietary tocopherol on the oxidative stability of turkey meat. Poultry Sci. 63: Sosnicki, A. A., and B. W. Wilson, Pathology of turkey skeletal muscle: implications of the poultry industry. Food Structure 10: Sosnicki, A. A., and B. W. Wilson, Relationship of focal myopathy of turkey skeletal muscle to meat quality. Pages in: Proceedings of the 19th World s Poultry Congress. Vol. 3. Amsterdam, The Netherlands. Sosnicki, A. A., R. G. Cassens, D. R. McIntyre, and J. J. Vimini, 1988a. Structural alterations in edematous and apparently normal skeletal muscle of domestic turkey. Avian Pathol. 17:

8 VITAMIN E EFFECTS ON TURKEY BREAST MEAT QUALITY 641 Sosnicki, A. A., R. G. Cassens, D. R. McIntyre, J. J. Vimini, and M. L. Greaser, 1988b. Characterization of hypercontracted fibers in skeletal muscle of domestic turkey (Meleagris gallopavo). Food Microstructure 7: Sosnicki, A. A., R. G. Cassens, D. R. McIntyre, J. J. Vimini, and M. L. Greaser, Incidence of microscopically detectable degenerative characteristics in skeletal muscle of turkey. Br. Poult. Sci. 30: Sosnicki, A. A., R. G. Cassens, J. J. Vimini, and M. L. Greaser, 1991a. Histopathological and ultrastructural alterations of turkey skeletal muscle. Poultry Sci. 70: Sosnicki, A. A., R. G. Cassens, J. J. Vimini, and M. L. Greaser, 1991b. Distribution of capillaries in normal and ischemic turkey skeletal muscle. Poultry Sci. 70: Webb, R. W., W. W. Marion, and P. L. Hayse, Effect of tocopherol supplementation on the quality of precooked and mechanically deboned turkey meat. J. Food Sci. 37: Wu, T. C., and B. W. Sheldon, Flavor components and factors associated with the development of off-flavors in cooked turkey rolls. J. Food Sci. 53: Yu, T. C., and R. O. Sinnhuber, An improved 2-thiobarbituric acid (TBA) procedure for the measurement of autooxidation in fish oils. J. Am. Oil Chem. Soc. 44: