- Email: [email protected]
Sodium lactate affects sensory and objective characteristics of tray-packed broiler chicken breast meat
Sodium Lactate Affects Sensory and Objective Characteristics of Tray-Packed Broiler Chicken Breast Meat1 S. K. WILLIAMS2 and K. PHILLIPS Animal Science Department, University of Florida, Gainesville, Florida 32611-0910
(Key words: shelf life, chicken breast meat, microbiology, sodium lactate) 1998 Poultry Science 77:765–769
unseasoned, Ictalurus nebulosus, marmoratus catfish fillets was extended after treatment w ith 3% sodium lactate, the fillets were unacceptable for consumption because of an objectionable sodium metallic aftertaste (Williams et al., 1995). The sodium aftertaste was due largely to the 12 to 12.5% sodium content of sodium lactate. It was determined that treating catfish fillets with 2% sodium lactate solutions, adjusted to pH 5.50, resulted in an acceptable product with extended shelf life of an additional 3 d (Williams et al., 1995). Adjusting the pH of sodium lactate also has the advantages of limiting the concentration of sodium added to the breast meat or other poultry products and reducing the usage level of sodium lactate. Williams (1993) determined that treating fresh catfish fillets with 2% sodium lactate (based on total batch weight) adjusted to pH 5.50 was more effective in reducing aerobic plate counts than 3% sodium lactate (based on total batch weight). The objective of this study was to determine the effects of 2% sodium lactate treatments, adjusted to various pH values, on sensory characteristics, instrumental texture, and microbial populations of tray-packed chicken broiler breast meat.
INTRODUCTION Sodium lactate has been used extensively in various food systems primarily for its antimicrobial properties (Papadopoulos et al., 1991; Zeitoun and Debevere, 1991; Williams et al., 1995). Researchers have reported antibotulinal properties of sodium lactate in poultry and seafood systems, when employed at concentrations of 1 to 7% (Anders, et al. 1987; Maas et al, 1989). In general, the effectiveness of sodium lactate increases with increased concentrations. However, there are sensory problems associated with increasing concentrations of sodium lactate above 2.0%. Papadopoulos et al. (1991) reported that cooked vacuum-packed beef rounds containing 3 and 4% sodium lactate resulted in higher cooking yields, enhanced color, and increased shelf life. However, panelists reported mild throat irritations and sodium aftertastes in the roasts treated with 4% sodium lactate. The aftertaste was even more pronounced in fresh catfish fillets. Although the shelf life of fresh
Received for publication June 16, 1997. Accepted for publication November 11, 1997. 1Florida Agricultural Experiment Station Journal Series R-05305. 2To whom correspondence should be addressed: [email protected]
Abbreviation Key: APC = aerobic plate count; NaL = sodium lactate.
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at 2 ± 1 C for 12 d. Approximately 15% of the panelists reported acidic aftertastes in samples treated with pH 5.00 sodium lactate solutions, and 10% of the panelists reported slight sodium or metallic off-flavor in all samples treated with sodium lactate. Instrumental texture measurements were similar (P > 0.05) for all treatments. Sodium lactate (pH 7.30 and 5.50) enhanced (P < 0.05) cooking yields and retarded the growth of spoilage bacteria (pH 5.50 and 5.00). Due to the development of severe discoloration and intense acidic off-odors and -flavors, testing was not conducted on samples treated with pH 4.50 and 4.00 sodium lactate solutions.
ABSTRACT The objective of this study was to determine the antimicrobial properties of sodium lactate solutions adjusted to various pH values. The effectiveness of sodium lactate increases with increased concentrations; however, there are off-flavor development problems associated with increasing concentrations of sodium lactate above 2.0%. This study evaluated the effects of 2% sodium lactate treatments, adjusted to various pH values, on sensory characteristics, instrumental texture, and microbial populations of traypacked broiler breast meat. Breast meat was treated with either tap water (pH 7.85) or 2% sodium lactate solutions (pH 7.30, 5.50, 5.00, 4.50, and 4.00) and stored
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MATERIALS AND METHODS
Sample Preparation
Sensory Evaluation and Cooking Yield The sensory evaluation was approved by the University of Florida’s Review Board for Human Research. Cooking and dissecting of the cooked muscles were conducted as described by Lyon and Lyon (1991). Six boneless and skinless whole chicken breasts were rinsed under running tap water to remove any bone, or other minute residuals, drained for approximately 1 min, and weighed. Copper-constantan thermocouples7 were inserted into the thickest part of the muscles prior to cooking. The breasts were wrapped in aluminum foil, placed in roasting pans (six breast halves per pan per treatment), and cooked at 176.7 C, in a conventional preheated gas oven, to 80 C internal muscle temperature. The cooked chicken was allowed to cool at room temperature for 10 min, weighed, and separated into Pectoralis major and Pectoralis minor. A 1.9-cm-wide strip of muscle, originating at the humeral insertion and terminating at the anterior end of the keel, so that muscle fibers were parallel, was cut from the medial area of each P. major muscle and reserved for instrumental texture
3PURAC America Inc., Arlington, IL 60069. 418-kg capacity tumbler, Lyco Inc., Janesville, WI 5Cryovac, Inc., Duncan, SC 29334. 6Borden, Inc., Illiopolis, IL 62539. 7Omega Engineering, Inc., Stanford, CT 06907. 8Instron Corp., Atlanta, GA 30340.
53545.
Instrumental Texture Measurements Texture measurements were conducted as described by Lyon and Lyon (1991). Two 1.9-cm-wide strips were each oriented in the Warner-Bratzler Shear attachment (type D.D., catalog no. 2830-002)8 to the Model 1011 Instron.8 Cross head speed was 200 mm/min with a 50-kg load cell, and full scale range of 10 kg. Shearing force was perpendicular to the direction of the fibers, and force to shear the sample was recorded in kilograms. Three breasts (total of six 1.9-cm-wide strips) were evaluated for texture per treatment per replication.
Microbiological Analysis Each 25-g sample was placed into a Nasco Whirl-Pak stomacher bag along with 225 mL of sterile 0.1% peptone
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Fresh boneless and skinless chicken breasts were purchased from a local supermarket approximately 72 h after processing. The breasts were split into halves, divided into four groups, and treated with either tap water (control, pH 7.85), or 2% sodium lactate solutions with pH values of 7.30 (original pH of sodium lactate, NaL-7.30), 5.50 (NaL-5.50), 5.00 (NaL-5.00), 4.50 (NaL4.50), and 4.00 (NaL-4.00). No spices, flavorings, or flavor potentiators were used in this study. The pH of the treatment solutions was adjusted using 88% lactic acid solutions.3 The sodium lactate solution (60% sodium lactate solution)3 in each treatment represented 2% of the total product weight. The chicken breasts were combined with the appropriate sodium lactate treatment solution, vacuum tumbled4 (15 min at approximately 172.32 kPa), placed into styrofoam trays,5 over-wrapped with polyvinyl chloride film (64 gauge film, oxygen transmission rate: 1,400 cc/m2 per 24 h at 22.8 C, water vapor transmission rate: 32 g/24 h at 37.8 C, Catalog No. RMF 61HY),6 heat-sealed, and stored at 2 ± 1 C for 12 d. Samples were analyzed in triplicate after 0, 3, 7, and 10 d for sensory characteristics, cooking yield, instrumental texture, and pH. Analyses for aerobic plate count (APC) and presence of Salmonella spp. were conducted through 12 d to determine the progression of microbial growth.
analyses. The remaining P. major muscles from each treatment were cubed (approximately 1.25 cm × 1.2 cm × thickness of cooked cut) and served (two cubes per treatment) along with room temperature water and unsalted crackers (two crackers per panelist) to an 11-member trained panel. Samples were served approximately 10 min after cooled to room temperature. A total of four sessions (i.e., Days 0, 3, 7, and 10) were conducted per replication. Each treatment was assigned a one-digit numerical code, and order of presentation to the panelists was randomized. Four samples (i.e., one sample from each treatment) were presented to each panelist. Panelists were instructed to eat crackers, drink water between each sample to clear their palate, and pause for 20 s between samples. Empty cups were provided for expectoration of the samples. Panelists included faculty, staff, and students at University of Florida. Prior to testing, panelists received approximately 24 h of training over a 5-d period. During the training sessions, panelists were presented samples exhibiting desired and undesired chicken flavor, overall tenderness, and off-flavor characteristics. Panelists were served chicken samples containing each of the off-flavors of concern, which included rancid, soapy, sour, bitter, metallic, sodium, and acid. They were also asked to document any objectionable texture and off-odor characteristics detected. Sensory evaluations were performed in a 12-booth partitioned sensory room, equipped with exhaust fans, and illuminated by a combination of red and white lighting. Each of the 12 booths was equipped with a ceiling lighting system to provide red, white, blue, or yellow lighting as needed. Eight-point hedonic scoring scales were employed for chicken flavor intensity, and overall tenderness (8 = extremely intense/tender, 7 = very intense/tender, 6 = moderately intense/tender, 5 = slightly intense/tender, 4 = slightly bland/tough, 3 = moderately bland/tough, 2 = very bland/tough, and 1 = extremely bland/tough). A six-point scale was employed for off-flavor (6 = none detected, 5 = threshold, barely detected, 4 = slight off flavor, 3 = moderate off-flavor, 2 = strong off-flavor, 1 = extreme off-flavor).
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SODIUM LACTATE IN CHICKEN BREAST MEAT TABLE 1. Sensory evaluation of chicken breast meat treated with sodium lactate (NaL) at different pH values and stored at 2 ± 1 C for 10 d Storage time Parameter1
Treatment
0 d
3 d
7 d
10 d
Chicken flavor intensity
Control NaL-7.30 NaL-5.50 NaL-5.00
5.23a 5.07ab 5.07ab 4.50b 0.13 6.83 6.71 6.45 6.23 0.12 5.70a 4.55b 4.45b 4.47b 0.13
5.24 5.24 5.03 5.38 0.13 6.94 7.03 6.53 6.47 0.12 5.50a 4.03b 4.27b 4.44b 0.13
4.82 5.15 5.15 5.11 0.13 6.11 6.89 6.30 6.52 0.12 4.85 4.15 4.19 4.74 0.13
5.10 4.95 5.00 4.80 0.13 6.95 6.70 6.45 6.20 0.12 3.80 4.40 4.40 4.20 0.13
SEM Overall tenderness
SEM Off-flavor
SEM
Control NaL-7.30 NaL-5.50 NaL-5.00 Control NaL-7.30 NaL-5.50 NaL-5.00
diluent and agitated9 for 1 min. Serial dilutions were prepared by transferring 11 mL of the sample homogenate into 99 mL of sterile 0.1% peptone diluent and agitating 25 times in a 29.58 cm arc, in approximately 7 s. Aliquots (1 mL) of the appropriate dilutions were transferred to duplicate sterile aerobic plate count Petrifilm (catalog no. 6400).10 Petrifilm was incubated at 20 C for 5 d. All colonies were counted, and reported as log10 colonyforming units per gram. The primary spoilage organisms for poultry are psychrotrophs (Jay, 1990), and represent the predominant microflora at 20 C. Three samples were analyzed per treatment per replication.
pH Each 11-g sample was combined with 99 mL of deionized water, and blended in a Waring blender for 1 min. The sample homogenate was measured for pH.11 Triplicate samples were measured per treatment per replication.
Data Analysis All experiments were replicated three times. The experimental design was a randomized complete block design with four treatments. Data of the three replications were pooled and analyzed using analysis of variance of
9Stomacher, Model 400, Tekmar Co., Cincinnati, OH 45242. 103M Microbiology Products, St. Paul, MN 55144. 11Orion pH meter, model no. SA520, Fisher Scientific, Pittsburgh, PA
15219.
the General Linear Models procedure of SAS software, and the LSMEANS procedure for generating standard errors of the mean (SAS Institute, 1990; Littell et al., 1991). Interaction between treatments, storage, and replications was tested for significance (P < 0.05). Significant differences among treatments and storage means were determined using Duncan’s multiple range test (SAS Institute, 1990).
RESULTS AND DISCUSSION
Sensory Evaluation and Cooking Yields Due to the development of severe discoloration and intense acidic off-odors and -flavors, testing was not conducted on samples treated with NaL-4.50 and NaL4.00. Except for Day 0, panelists scored all treatments similarly (P > 0.05) for chicken flavor intensity, and overall tenderness through 10 d (Table 1). The degree of off-flavor detected in all sodium lactate treated breast meat was significantly (P < 0.05) more intense than that of the control through 3 d. After 7 and 10 d, all treatments had developed a slight off-flavor. Approximately 15% of the panelists reported acidic aftertastes in samples treated with NaL-5.00 solutions; and approximately 10% reported a slight sodium or metallic off-flavor in all samples treated with sodium lactate. The slight acidic aftertaste reported for the NaL-5.00 treated breast meat may account for its significant decline in chicken flavor intensity on Day 0. All sensory analyses were discontinued after 10 d because of the development of an objectionable off-odor and offflavor in the control breast meat.
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a,bMeans within a column and parameter with no common superscript differ significantly (P < 0.05); n = 33 values per mean. 1Scoring scale: chicken flavor intensity (6 = moderately intense, 5 = slightly intense, 4 = slightly bland, 3 = moderately bland, 2 = very bland, and 1 = extremely bland); overall tenderness (7 = very tender, 6 = moderately tender, 5 = slightly tender, 4 = slightly tough, 3 = moderately tough, 2 = very tough, and 1 = extremely tough); offflavor (6 = none detected, 5 = threshold, 4 = slight off-flavor, 3 = moderate off-flavor, 2 = strong off-flavor, and 1 = extreme off-flavor).
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WILLIAMS AND PHILLIPS TABLE 2. Cooking yield percentages and Warner-Bratzler shears for chicken breast meat treated with sodium lactate (NaL) at different pH values and stored at 2 ± 1 C for 10 d Storage time Parameter
Treatment
0 d
3 d
7 d
10 d
Cooking yield, %
Control NaL-7.30 NaL-5.50 NaL-5.00
81.45 86.06 81.66 84.16 1.03 2.40 2.57 1.73 2.83 0.26
75.62b 84.64a 84.64a 76.65b 1.03 1.96 1.91 2.44 2.49 0.26
76.43c 82.45ab 85.45a 79.98bc 1.03 2.08 1.86 2.37 2.33 0.26
76.97 74.43 77.52 71.94 1.03 2.19 1.85 2.62 2.84 0.26
SEM Warner-Bratzler shear force, kg
Control NaL-7.30 NaL-5.50 NaL-5.00
SEM
a–cMeans within the same column and parameter with no common superscript differ significantly (P < 0.05); n = 9 values per mean.
Instrumental Texture The control and all sodium lactate treated samples were similar (P > 0.05) in texture through 10 d storage (Table 2). All Warner-Bratzler shear values were in the range of 1.73 to 2.84 kg, which was indicative of very tender breast meat (Lyon and Lyon, 1991). The corresponding panelist scores were 6.11 to 7.03, which were indicative of moderately
tender to very tender breast meat. A comparison of the panelists responses for tenderness (Table 1) and WarnerBratzler shear values (Table 2) revealed that the sodium lactate treatments had no adverse effects on texture of the breast meat.
Microbiological Evaluation The APC increased as storage time increased, but remained lower for all sodium lactate treated breast meat through 10 d (Table 3). Sodium lactate treated breast meat resulted in significantly lower (P < 0.05) APC after 7 and 12 d, when compared to the control treatment. The NaL5.50, and NaL-5.00 were the most effective treatments for retarding microbial growth on the breast meat. The intense off-odor and moderate off-flavor detected in the control breast meat samples after 10 d storage might be largely attributed to the growth and proliferation of microorganisms. Poultry is usually considered to be spoiled when the microflora reaches log10 7 to log10 8 cfu/ g (Ayres, 1960). The APC was log10 8.93 cfu/g for the control breast meat samples after 10 d storage. Although the pH values of the control and NaL-7.30 samples were similar (P > 0.05) on all storage days except
TABLE 3. pH and aerobic plate count (APC) for chicken breast meat treated with sodium lactate (NaL) at various pH values and stored at 2 ± 1 C for 12 d Storage time Parameter
Treatment
0 d
3 d
7 d
10 d
12 d
pH
Control NaL-7.30 NaL-5.50 NaL-5.00
5.82ab 5.93a 5.41bc 5.02c 0.06 4.99 4.12 4.30 3.84 0.28
5.82a 5.84a 5.50ab 5.24b 0.06 5.25 3.51 3.49 3.11 0.28
5.90a 5.99a 5.70a 5.40b 0.06 7.24a 5.87b 5.09bc 3.90c 0.28
5.97a 5.75ab 5.53ab 5.41b 0.06 8.93a 7.69a 6.53ab 5.16b 0.28
6.38a 5.97b 5.80bc 5.53c 0.06 9.55a 7.76b 8.08b 7.10b 0.28
SEM APC, log10 cfu/g
SEM
Control NaL-7.30 NaL-5.50 NaL-5.00
a–cMeans within a column and parameter with no common superscript differ significantly (P < 0.05); n = 9 values per mean.
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Cooking yields decreased as storage time increased (Table 2). Treating breast meat with NaL-7.30 and NaL5.50 resulted in significantly higher (P < 0.05) cooking yields after 3 and 7 d storage, when compared to the control breast meat. The lower cooking yields reported for NaL-5.00 might be largely attributed to a slight to moderate denaturation of surface proteins that were in immediate contact with the sodium lactate during treatment application. This denaturation would result in decreased water-holding capacity in the proteins, and subsequent decreased cooking yields. The water holding capacity of meat and poultry proteins decreases at or near pH 5.00, which is their isoelectric point. The pH of the NaL-5.00 treated breast meat ranged from 5.02 on Day 0 to 5.41 on Day 10 (Table 3).
SODIUM LACTATE IN CHICKEN BREAST MEAT
REFERENCES Anders, J., A. L. Milkowski, and J. G. Cerveny, 1987. A foodstuff containing a lactate salt. U.S. Patent 808319 (851212), Oscar Mayer, Madison, WI. Ayres, J. C., 1960. The relationship of the organisms of the genus Pseudomonas to the spoilage of meat, poultry and eggs. J. Appl. Bacteriol. 23:471–486. Grau, F. H., 1980. Inhibition of the anaerobic growth of Brochothrix thermosphacta by lactic acid. Appl. Environ. Microbiol. 40:433–436. Jay, J., 1990. Spoilage of poultry. Pages 220–221 in: Modern Food Microbiology. 4 ed. Van Nostrand Reinhold, New York, NY. Littell, R. C., R. J. Freund, and P. C. Spector, 1991. Analysis of variance for balanced data. Pages 86–95 in: SAS Systems for Linear Models. SAS Institute Inc., Cary, NC. Lyon, B. G., and C. E. Lyon, 1991. Shear value ranges by Instron Warner-Bratzler and single-blade Allo-Kramer devices that correspond to sensory tenderness. Poultry Sci. 70:188–191. Maas, M. R., K. A. Glass, and M. P. Doyle, 1989. Sodium lactate delays toxin production by Clostridium botulinum in cook-in bag turkey products. Appl. Environ. Microbiol. 55: 2226–2229. Papadopoulos, L. S., R. K. Miller, G. R. Acuff, C. Vanderzant, and H. R. Cross, 1991. Effect of sodium lactate on microbial and chemical composition of cooked beef during storage. J. Food Sci. 56:341–347. SAS Institute, 1990. Statistical Analysis System. 6.04 ed. SAS Institute Inc., Cary, NC. Segel, I. H., 1976. Acid-base chemistry. Pages 32–33 in: Biochemical Calculations. 2 ed. John Wiley and Sons, New York, NY. Williams, S. K., 1993. The effects of sodium lactate on the shelf life and consumer acceptance of commercially processed catfish. Ph.D. dissertation, University of Florida, Gainesville, FL. Williams, S. K., G. E. Rodrick, and R. L. West, 1995. Sodium lactate affects shelf life and consumer acceptance of fresh cat fish (Ictalurus nebulosus, marmoratus) fillets stored under simulated retail conditions. J. Food Sci. 60:636–639. Zeitoun, A.A.M., and J. M. Debevere, 1991. Inhibition, survival and growth of Listeria monocytogenes on poultry as influenced by buffered lactic acid treatment and modified atmosphere packaging. Int. J. Food Microbiol. 14:161–164.
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Day 12, the APC were significantly lower (P < 0.05) for samples treated with NaL-7.30. The antimicrobial effect of sodium lactate treatments was enhanced as the pH of the solutions decreased, indicating that pH influenced the reduction in microbial growth. In addition, the fact that antimicrobial activity was also observed in the NaL-7.30 treatment in which no pH was adjusted, suggested that the sodium lactate treatment also exerted antimicrobial effects on the microflora of the breast meat. Grau (1980) determined that sodium lactate solutions at pH 5.70 or lower inhibited the anaerobic growth of Brochothrix thermosphacta in beef muscle extract samples stored at 25 and 5 C. Williams et al. (1995) determined that the effectiveness of sodium lactate in extending the shelf life of fresh catfish fillets increased as the pH of the treatment solutions approached the pKa (the pH at which the concentration of dissociated and undissociated acid is equal for a weak acid) value of 3.86 for lactic acid. However, at pH values of 4.00 to 5.00, the acceptability of the fillets decreased due to denaturation of proteins and development of acidic flavor. As the pH of the sodium lactate solutions decreased, the concentration of undissociated lactic acid and antimicrobial properties increased. However, increasing lactic acid concentration (i.e., pH 4.00, 4.50, and 5.00) resulted in discoloration and denaturation of the fish proteins. The final calculated concentrations, using the Henderson-Hasselbach equation (Segel, 1976), of sodium lactate and lactic acid in the treatment solutions for the breast meat were 1.08 and 0.03 M, respectively, for pH 5.50; and 1.24 and 0.09 M, respectively, for pH 5.00. This study revealed that sodium lactate treatment solutions with pH adjusted to 5.50 and 5.00 were most effective in retarding growth of the spoilage microflora on the breast meat. The slight sodium, metallic, or acidic offflavors detected when these treatments were applied will probably be minimized or eliminated in poultry product systems in which seasonings such as salt or spices are employed. Panelists detected no off-flavor (i.e., sodium, metallic, or acidic) in a cooked vacuum packaged roast beef product containing 0.5% sodium chloride, and 3% sodium lactate (Papadopoulos et al., 1991).
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(Key words: shelf life, chicken breast meat, microbiology, sodium lactate) 1998 Poultry Science 77:765–769
unseasoned, Ictalurus nebulosus, marmoratus catfish fillets was extended after treatment w ith 3% sodium lactate, the fillets were unacceptable for consumption because of an objectionable sodium metallic aftertaste (Williams et al., 1995). The sodium aftertaste was due largely to the 12 to 12.5% sodium content of sodium lactate. It was determined that treating catfish fillets with 2% sodium lactate solutions, adjusted to pH 5.50, resulted in an acceptable product with extended shelf life of an additional 3 d (Williams et al., 1995). Adjusting the pH of sodium lactate also has the advantages of limiting the concentration of sodium added to the breast meat or other poultry products and reducing the usage level of sodium lactate. Williams (1993) determined that treating fresh catfish fillets with 2% sodium lactate (based on total batch weight) adjusted to pH 5.50 was more effective in reducing aerobic plate counts than 3% sodium lactate (based on total batch weight). The objective of this study was to determine the effects of 2% sodium lactate treatments, adjusted to various pH values, on sensory characteristics, instrumental texture, and microbial populations of tray-packed chicken broiler breast meat.
INTRODUCTION Sodium lactate has been used extensively in various food systems primarily for its antimicrobial properties (Papadopoulos et al., 1991; Zeitoun and Debevere, 1991; Williams et al., 1995). Researchers have reported antibotulinal properties of sodium lactate in poultry and seafood systems, when employed at concentrations of 1 to 7% (Anders, et al. 1987; Maas et al, 1989). In general, the effectiveness of sodium lactate increases with increased concentrations. However, there are sensory problems associated with increasing concentrations of sodium lactate above 2.0%. Papadopoulos et al. (1991) reported that cooked vacuum-packed beef rounds containing 3 and 4% sodium lactate resulted in higher cooking yields, enhanced color, and increased shelf life. However, panelists reported mild throat irritations and sodium aftertastes in the roasts treated with 4% sodium lactate. The aftertaste was even more pronounced in fresh catfish fillets. Although the shelf life of fresh
Received for publication June 16, 1997. Accepted for publication November 11, 1997. 1Florida Agricultural Experiment Station Journal Series R-05305. 2To whom correspondence should be addressed: [email protected]
Abbreviation Key: APC = aerobic plate count; NaL = sodium lactate.
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at 2 ± 1 C for 12 d. Approximately 15% of the panelists reported acidic aftertastes in samples treated with pH 5.00 sodium lactate solutions, and 10% of the panelists reported slight sodium or metallic off-flavor in all samples treated with sodium lactate. Instrumental texture measurements were similar (P > 0.05) for all treatments. Sodium lactate (pH 7.30 and 5.50) enhanced (P < 0.05) cooking yields and retarded the growth of spoilage bacteria (pH 5.50 and 5.00). Due to the development of severe discoloration and intense acidic off-odors and -flavors, testing was not conducted on samples treated with pH 4.50 and 4.00 sodium lactate solutions.
ABSTRACT The objective of this study was to determine the antimicrobial properties of sodium lactate solutions adjusted to various pH values. The effectiveness of sodium lactate increases with increased concentrations; however, there are off-flavor development problems associated with increasing concentrations of sodium lactate above 2.0%. This study evaluated the effects of 2% sodium lactate treatments, adjusted to various pH values, on sensory characteristics, instrumental texture, and microbial populations of traypacked broiler breast meat. Breast meat was treated with either tap water (pH 7.85) or 2% sodium lactate solutions (pH 7.30, 5.50, 5.00, 4.50, and 4.00) and stored
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WILLIAMS AND PHILLIPS
MATERIALS AND METHODS
Sample Preparation
Sensory Evaluation and Cooking Yield The sensory evaluation was approved by the University of Florida’s Review Board for Human Research. Cooking and dissecting of the cooked muscles were conducted as described by Lyon and Lyon (1991). Six boneless and skinless whole chicken breasts were rinsed under running tap water to remove any bone, or other minute residuals, drained for approximately 1 min, and weighed. Copper-constantan thermocouples7 were inserted into the thickest part of the muscles prior to cooking. The breasts were wrapped in aluminum foil, placed in roasting pans (six breast halves per pan per treatment), and cooked at 176.7 C, in a conventional preheated gas oven, to 80 C internal muscle temperature. The cooked chicken was allowed to cool at room temperature for 10 min, weighed, and separated into Pectoralis major and Pectoralis minor. A 1.9-cm-wide strip of muscle, originating at the humeral insertion and terminating at the anterior end of the keel, so that muscle fibers were parallel, was cut from the medial area of each P. major muscle and reserved for instrumental texture
3PURAC America Inc., Arlington, IL 60069. 418-kg capacity tumbler, Lyco Inc., Janesville, WI 5Cryovac, Inc., Duncan, SC 29334. 6Borden, Inc., Illiopolis, IL 62539. 7Omega Engineering, Inc., Stanford, CT 06907. 8Instron Corp., Atlanta, GA 30340.
53545.
Instrumental Texture Measurements Texture measurements were conducted as described by Lyon and Lyon (1991). Two 1.9-cm-wide strips were each oriented in the Warner-Bratzler Shear attachment (type D.D., catalog no. 2830-002)8 to the Model 1011 Instron.8 Cross head speed was 200 mm/min with a 50-kg load cell, and full scale range of 10 kg. Shearing force was perpendicular to the direction of the fibers, and force to shear the sample was recorded in kilograms. Three breasts (total of six 1.9-cm-wide strips) were evaluated for texture per treatment per replication.
Microbiological Analysis Each 25-g sample was placed into a Nasco Whirl-Pak stomacher bag along with 225 mL of sterile 0.1% peptone
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Fresh boneless and skinless chicken breasts were purchased from a local supermarket approximately 72 h after processing. The breasts were split into halves, divided into four groups, and treated with either tap water (control, pH 7.85), or 2% sodium lactate solutions with pH values of 7.30 (original pH of sodium lactate, NaL-7.30), 5.50 (NaL-5.50), 5.00 (NaL-5.00), 4.50 (NaL4.50), and 4.00 (NaL-4.00). No spices, flavorings, or flavor potentiators were used in this study. The pH of the treatment solutions was adjusted using 88% lactic acid solutions.3 The sodium lactate solution (60% sodium lactate solution)3 in each treatment represented 2% of the total product weight. The chicken breasts were combined with the appropriate sodium lactate treatment solution, vacuum tumbled4 (15 min at approximately 172.32 kPa), placed into styrofoam trays,5 over-wrapped with polyvinyl chloride film (64 gauge film, oxygen transmission rate: 1,400 cc/m2 per 24 h at 22.8 C, water vapor transmission rate: 32 g/24 h at 37.8 C, Catalog No. RMF 61HY),6 heat-sealed, and stored at 2 ± 1 C for 12 d. Samples were analyzed in triplicate after 0, 3, 7, and 10 d for sensory characteristics, cooking yield, instrumental texture, and pH. Analyses for aerobic plate count (APC) and presence of Salmonella spp. were conducted through 12 d to determine the progression of microbial growth.
analyses. The remaining P. major muscles from each treatment were cubed (approximately 1.25 cm × 1.2 cm × thickness of cooked cut) and served (two cubes per treatment) along with room temperature water and unsalted crackers (two crackers per panelist) to an 11-member trained panel. Samples were served approximately 10 min after cooled to room temperature. A total of four sessions (i.e., Days 0, 3, 7, and 10) were conducted per replication. Each treatment was assigned a one-digit numerical code, and order of presentation to the panelists was randomized. Four samples (i.e., one sample from each treatment) were presented to each panelist. Panelists were instructed to eat crackers, drink water between each sample to clear their palate, and pause for 20 s between samples. Empty cups were provided for expectoration of the samples. Panelists included faculty, staff, and students at University of Florida. Prior to testing, panelists received approximately 24 h of training over a 5-d period. During the training sessions, panelists were presented samples exhibiting desired and undesired chicken flavor, overall tenderness, and off-flavor characteristics. Panelists were served chicken samples containing each of the off-flavors of concern, which included rancid, soapy, sour, bitter, metallic, sodium, and acid. They were also asked to document any objectionable texture and off-odor characteristics detected. Sensory evaluations were performed in a 12-booth partitioned sensory room, equipped with exhaust fans, and illuminated by a combination of red and white lighting. Each of the 12 booths was equipped with a ceiling lighting system to provide red, white, blue, or yellow lighting as needed. Eight-point hedonic scoring scales were employed for chicken flavor intensity, and overall tenderness (8 = extremely intense/tender, 7 = very intense/tender, 6 = moderately intense/tender, 5 = slightly intense/tender, 4 = slightly bland/tough, 3 = moderately bland/tough, 2 = very bland/tough, and 1 = extremely bland/tough). A six-point scale was employed for off-flavor (6 = none detected, 5 = threshold, barely detected, 4 = slight off flavor, 3 = moderate off-flavor, 2 = strong off-flavor, 1 = extreme off-flavor).
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SODIUM LACTATE IN CHICKEN BREAST MEAT TABLE 1. Sensory evaluation of chicken breast meat treated with sodium lactate (NaL) at different pH values and stored at 2 ± 1 C for 10 d Storage time Parameter1
Treatment
0 d
3 d
7 d
10 d
Chicken flavor intensity
Control NaL-7.30 NaL-5.50 NaL-5.00
5.23a 5.07ab 5.07ab 4.50b 0.13 6.83 6.71 6.45 6.23 0.12 5.70a 4.55b 4.45b 4.47b 0.13
5.24 5.24 5.03 5.38 0.13 6.94 7.03 6.53 6.47 0.12 5.50a 4.03b 4.27b 4.44b 0.13
4.82 5.15 5.15 5.11 0.13 6.11 6.89 6.30 6.52 0.12 4.85 4.15 4.19 4.74 0.13
5.10 4.95 5.00 4.80 0.13 6.95 6.70 6.45 6.20 0.12 3.80 4.40 4.40 4.20 0.13
SEM Overall tenderness
SEM Off-flavor
SEM
Control NaL-7.30 NaL-5.50 NaL-5.00 Control NaL-7.30 NaL-5.50 NaL-5.00
diluent and agitated9 for 1 min. Serial dilutions were prepared by transferring 11 mL of the sample homogenate into 99 mL of sterile 0.1% peptone diluent and agitating 25 times in a 29.58 cm arc, in approximately 7 s. Aliquots (1 mL) of the appropriate dilutions were transferred to duplicate sterile aerobic plate count Petrifilm (catalog no. 6400).10 Petrifilm was incubated at 20 C for 5 d. All colonies were counted, and reported as log10 colonyforming units per gram. The primary spoilage organisms for poultry are psychrotrophs (Jay, 1990), and represent the predominant microflora at 20 C. Three samples were analyzed per treatment per replication.
pH Each 11-g sample was combined with 99 mL of deionized water, and blended in a Waring blender for 1 min. The sample homogenate was measured for pH.11 Triplicate samples were measured per treatment per replication.
Data Analysis All experiments were replicated three times. The experimental design was a randomized complete block design with four treatments. Data of the three replications were pooled and analyzed using analysis of variance of
9Stomacher, Model 400, Tekmar Co., Cincinnati, OH 45242. 103M Microbiology Products, St. Paul, MN 55144. 11Orion pH meter, model no. SA520, Fisher Scientific, Pittsburgh, PA
15219.
the General Linear Models procedure of SAS software, and the LSMEANS procedure for generating standard errors of the mean (SAS Institute, 1990; Littell et al., 1991). Interaction between treatments, storage, and replications was tested for significance (P < 0.05). Significant differences among treatments and storage means were determined using Duncan’s multiple range test (SAS Institute, 1990).
RESULTS AND DISCUSSION
Sensory Evaluation and Cooking Yields Due to the development of severe discoloration and intense acidic off-odors and -flavors, testing was not conducted on samples treated with NaL-4.50 and NaL4.00. Except for Day 0, panelists scored all treatments similarly (P > 0.05) for chicken flavor intensity, and overall tenderness through 10 d (Table 1). The degree of off-flavor detected in all sodium lactate treated breast meat was significantly (P < 0.05) more intense than that of the control through 3 d. After 7 and 10 d, all treatments had developed a slight off-flavor. Approximately 15% of the panelists reported acidic aftertastes in samples treated with NaL-5.00 solutions; and approximately 10% reported a slight sodium or metallic off-flavor in all samples treated with sodium lactate. The slight acidic aftertaste reported for the NaL-5.00 treated breast meat may account for its significant decline in chicken flavor intensity on Day 0. All sensory analyses were discontinued after 10 d because of the development of an objectionable off-odor and offflavor in the control breast meat.
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a,bMeans within a column and parameter with no common superscript differ significantly (P < 0.05); n = 33 values per mean. 1Scoring scale: chicken flavor intensity (6 = moderately intense, 5 = slightly intense, 4 = slightly bland, 3 = moderately bland, 2 = very bland, and 1 = extremely bland); overall tenderness (7 = very tender, 6 = moderately tender, 5 = slightly tender, 4 = slightly tough, 3 = moderately tough, 2 = very tough, and 1 = extremely tough); offflavor (6 = none detected, 5 = threshold, 4 = slight off-flavor, 3 = moderate off-flavor, 2 = strong off-flavor, and 1 = extreme off-flavor).
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WILLIAMS AND PHILLIPS TABLE 2. Cooking yield percentages and Warner-Bratzler shears for chicken breast meat treated with sodium lactate (NaL) at different pH values and stored at 2 ± 1 C for 10 d Storage time Parameter
Treatment
0 d
3 d
7 d
10 d
Cooking yield, %
Control NaL-7.30 NaL-5.50 NaL-5.00
81.45 86.06 81.66 84.16 1.03 2.40 2.57 1.73 2.83 0.26
75.62b 84.64a 84.64a 76.65b 1.03 1.96 1.91 2.44 2.49 0.26
76.43c 82.45ab 85.45a 79.98bc 1.03 2.08 1.86 2.37 2.33 0.26
76.97 74.43 77.52 71.94 1.03 2.19 1.85 2.62 2.84 0.26
SEM Warner-Bratzler shear force, kg
Control NaL-7.30 NaL-5.50 NaL-5.00
SEM
a–cMeans within the same column and parameter with no common superscript differ significantly (P < 0.05); n = 9 values per mean.
Instrumental Texture The control and all sodium lactate treated samples were similar (P > 0.05) in texture through 10 d storage (Table 2). All Warner-Bratzler shear values were in the range of 1.73 to 2.84 kg, which was indicative of very tender breast meat (Lyon and Lyon, 1991). The corresponding panelist scores were 6.11 to 7.03, which were indicative of moderately
tender to very tender breast meat. A comparison of the panelists responses for tenderness (Table 1) and WarnerBratzler shear values (Table 2) revealed that the sodium lactate treatments had no adverse effects on texture of the breast meat.
Microbiological Evaluation The APC increased as storage time increased, but remained lower for all sodium lactate treated breast meat through 10 d (Table 3). Sodium lactate treated breast meat resulted in significantly lower (P < 0.05) APC after 7 and 12 d, when compared to the control treatment. The NaL5.50, and NaL-5.00 were the most effective treatments for retarding microbial growth on the breast meat. The intense off-odor and moderate off-flavor detected in the control breast meat samples after 10 d storage might be largely attributed to the growth and proliferation of microorganisms. Poultry is usually considered to be spoiled when the microflora reaches log10 7 to log10 8 cfu/ g (Ayres, 1960). The APC was log10 8.93 cfu/g for the control breast meat samples after 10 d storage. Although the pH values of the control and NaL-7.30 samples were similar (P > 0.05) on all storage days except
TABLE 3. pH and aerobic plate count (APC) for chicken breast meat treated with sodium lactate (NaL) at various pH values and stored at 2 ± 1 C for 12 d Storage time Parameter
Treatment
0 d
3 d
7 d
10 d
12 d
pH
Control NaL-7.30 NaL-5.50 NaL-5.00
5.82ab 5.93a 5.41bc 5.02c 0.06 4.99 4.12 4.30 3.84 0.28
5.82a 5.84a 5.50ab 5.24b 0.06 5.25 3.51 3.49 3.11 0.28
5.90a 5.99a 5.70a 5.40b 0.06 7.24a 5.87b 5.09bc 3.90c 0.28
5.97a 5.75ab 5.53ab 5.41b 0.06 8.93a 7.69a 6.53ab 5.16b 0.28
6.38a 5.97b 5.80bc 5.53c 0.06 9.55a 7.76b 8.08b 7.10b 0.28
SEM APC, log10 cfu/g
SEM
Control NaL-7.30 NaL-5.50 NaL-5.00
a–cMeans within a column and parameter with no common superscript differ significantly (P < 0.05); n = 9 values per mean.
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Cooking yields decreased as storage time increased (Table 2). Treating breast meat with NaL-7.30 and NaL5.50 resulted in significantly higher (P < 0.05) cooking yields after 3 and 7 d storage, when compared to the control breast meat. The lower cooking yields reported for NaL-5.00 might be largely attributed to a slight to moderate denaturation of surface proteins that were in immediate contact with the sodium lactate during treatment application. This denaturation would result in decreased water-holding capacity in the proteins, and subsequent decreased cooking yields. The water holding capacity of meat and poultry proteins decreases at or near pH 5.00, which is their isoelectric point. The pH of the NaL-5.00 treated breast meat ranged from 5.02 on Day 0 to 5.41 on Day 10 (Table 3).
SODIUM LACTATE IN CHICKEN BREAST MEAT
REFERENCES Anders, J., A. L. Milkowski, and J. G. Cerveny, 1987. A foodstuff containing a lactate salt. U.S. Patent 808319 (851212), Oscar Mayer, Madison, WI. Ayres, J. C., 1960. The relationship of the organisms of the genus Pseudomonas to the spoilage of meat, poultry and eggs. J. Appl. Bacteriol. 23:471–486. Grau, F. H., 1980. Inhibition of the anaerobic growth of Brochothrix thermosphacta by lactic acid. Appl. Environ. Microbiol. 40:433–436. Jay, J., 1990. Spoilage of poultry. Pages 220–221 in: Modern Food Microbiology. 4 ed. Van Nostrand Reinhold, New York, NY. Littell, R. C., R. J. Freund, and P. C. Spector, 1991. Analysis of variance for balanced data. Pages 86–95 in: SAS Systems for Linear Models. SAS Institute Inc., Cary, NC. Lyon, B. G., and C. E. Lyon, 1991. Shear value ranges by Instron Warner-Bratzler and single-blade Allo-Kramer devices that correspond to sensory tenderness. Poultry Sci. 70:188–191. Maas, M. R., K. A. Glass, and M. P. Doyle, 1989. Sodium lactate delays toxin production by Clostridium botulinum in cook-in bag turkey products. Appl. Environ. Microbiol. 55: 2226–2229. Papadopoulos, L. S., R. K. Miller, G. R. Acuff, C. Vanderzant, and H. R. Cross, 1991. Effect of sodium lactate on microbial and chemical composition of cooked beef during storage. J. Food Sci. 56:341–347. SAS Institute, 1990. Statistical Analysis System. 6.04 ed. SAS Institute Inc., Cary, NC. Segel, I. H., 1976. Acid-base chemistry. Pages 32–33 in: Biochemical Calculations. 2 ed. John Wiley and Sons, New York, NY. Williams, S. K., 1993. The effects of sodium lactate on the shelf life and consumer acceptance of commercially processed catfish. Ph.D. dissertation, University of Florida, Gainesville, FL. Williams, S. K., G. E. Rodrick, and R. L. West, 1995. Sodium lactate affects shelf life and consumer acceptance of fresh cat fish (Ictalurus nebulosus, marmoratus) fillets stored under simulated retail conditions. J. Food Sci. 60:636–639. Zeitoun, A.A.M., and J. M. Debevere, 1991. Inhibition, survival and growth of Listeria monocytogenes on poultry as influenced by buffered lactic acid treatment and modified atmosphere packaging. Int. J. Food Microbiol. 14:161–164.
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Day 12, the APC were significantly lower (P < 0.05) for samples treated with NaL-7.30. The antimicrobial effect of sodium lactate treatments was enhanced as the pH of the solutions decreased, indicating that pH influenced the reduction in microbial growth. In addition, the fact that antimicrobial activity was also observed in the NaL-7.30 treatment in which no pH was adjusted, suggested that the sodium lactate treatment also exerted antimicrobial effects on the microflora of the breast meat. Grau (1980) determined that sodium lactate solutions at pH 5.70 or lower inhibited the anaerobic growth of Brochothrix thermosphacta in beef muscle extract samples stored at 25 and 5 C. Williams et al. (1995) determined that the effectiveness of sodium lactate in extending the shelf life of fresh catfish fillets increased as the pH of the treatment solutions approached the pKa (the pH at which the concentration of dissociated and undissociated acid is equal for a weak acid) value of 3.86 for lactic acid. However, at pH values of 4.00 to 5.00, the acceptability of the fillets decreased due to denaturation of proteins and development of acidic flavor. As the pH of the sodium lactate solutions decreased, the concentration of undissociated lactic acid and antimicrobial properties increased. However, increasing lactic acid concentration (i.e., pH 4.00, 4.50, and 5.00) resulted in discoloration and denaturation of the fish proteins. The final calculated concentrations, using the Henderson-Hasselbach equation (Segel, 1976), of sodium lactate and lactic acid in the treatment solutions for the breast meat were 1.08 and 0.03 M, respectively, for pH 5.50; and 1.24 and 0.09 M, respectively, for pH 5.00. This study revealed that sodium lactate treatment solutions with pH adjusted to 5.50 and 5.00 were most effective in retarding growth of the spoilage microflora on the breast meat. The slight sodium, metallic, or acidic offflavors detected when these treatments were applied will probably be minimized or eliminated in poultry product systems in which seasonings such as salt or spices are employed. Panelists detected no off-flavor (i.e., sodium, metallic, or acidic) in a cooked vacuum packaged roast beef product containing 0.5% sodium chloride, and 3% sodium lactate (Papadopoulos et al., 1991).
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