Cold-batter mincing of hot-boned and crust-frozen air-chilled turkey breast allows for reduced sodium content in protein gels H. C. Lee,* M. Medellin-Lopez,f P. Singh,f T. Sansawat,f K. B. Chin,:]: and I. K ang*!1 *Department of Animal Science, and f Department of Food Science and Human Nutrition, College of Agriculture and Natural Resources, Michigan State University, East Lansing 48824; and f Department of Animal Science, and Functional Foods Research Institute, Chonnam National University, Gwangju, 500-757, South Korea ABSTRACT The purpose of this research was to evalu
ate sodium reduction in the protein gels that were pre pared with turkey breasts after hot boning (HB), quar ter (id) sectioning, crust-frozen air-chilling (CFAC), and cold temperature mincing. For each of 4 replica tions, 36 turkeys were slaughtered and eviscerated. Onehalf of the carcasses were randomly assigned to water immersion chilling for chill boning (CB), whereas the remaining carcasses were immediately HB and quartersectioned/crust-frozen air-chilled (HB-ldCFAC) in a freezing room (-12°C, 1.0 m/s). After deboning, CB fil lets were conventionally minced, whereas HB-Id CFAC fillets were cold minced up to 27 min with 1 or 2% salt. From the beginning of mincing, the batter tem peratures of HB-y4CFAC were lower (P < 0.05) than those of CB batters up to 12 and 21 min for 2 and 1% salts, respectively. Upon mincing, the batter pH of the HB-14CFAC (P < 0.05) rapidly decreased and
was not different (P > 0.05) from the pH of CB bat ters, except for the 1% salt HB-Id CFAC batter after 15 min of mincing. The pattern of pH was not changed when the batters were stored overnight. The protein of 2% salt HB-Id CFAC fillets was more extractable (P < 0.05) than that of CB fillets at 9, 12, 18, and 24 min. Similarly, the protein of 1% salt HB-Id CFAC fillets was more extractable (P < 0.05) than that of CB fillets from 12 min. Stress values of 2% salt HB-Id CFAC gels were higher (P < 0.05) than those of 1 and 2% salt CB gels, with intermediate values for 1% salt HB-UiCFAC gels. In the scanning electron microscope image, prerig or batter appears to have more open space, less protein aggregation, and more protein-coated fat particles than those of postrigor batters. Based on these results, the combination of HB-Id CFAC and cold-batter-mincing technologies appear to improve protein functionality and sodium reduction capacity.
K ey words: sodium reduction, hot boning, crust freezing, cold mincing, protein functionality 2014 Poultry Science 93:2327-2336 http://dx.doi.org/10.3382/ps.2014-03915
INTRODUCTION Over the past 25 yr in the United States, the aver age salt intake has increased approximately 56%, partly because people are eating more processed and prepack aged products than ever before. The largest portion (77%) of salt in the American diet comes from pro cessed products and restaurant foods (Mattes and Don nelly, 1991). As a result, most Americans are consuming excessive amounts of salt, which can lead to negative health effects. To solve this issue, meat processors are challenged on how sodium levels can be reduced in their products while maintaining product characteristics and quality. In processed meats, salt (NaCl) not only con tributes flavor and shelf-life extension, but also plays a
©2014 Poultry Science Association Inc. Received January 17, 2014. Accepted May 10, 2014. Corresponding author: [email protected]
major role in enhancing protein functionality, thereby developing a desirable texture. As a result, salt reduc tion without food quality loss is a significant technical challenge. Alternative methods of meat processing need to be evaluated for their ability to enhance or maintain product quality with reduced salt levels. Hot boning (HB) or prerigor processing has been known to generate superior quality to chill boning (CB) for raw and processed meat products (Kastner, 1977; Cuthbertson, 1980). Froning and Neelakantan (1971) reported that the meat batter made with prerigor mus cle exhibited higher emulsifying capacity and emulsion stability than that of postrigor muscle. A higher cook ing yield was observed from hot cuts than chill cuts in broiler meat (Wyche and Goodwin, 1974). Due to the rapid muscle retrieval from carcasses after slaughter, the HB processing has been known for many advan tages such as energy saving, high processing yield, high throughput, reduced chilling time, and chilling space (Lyon and Hamm, 1986; McPhail, 1995).
2327
LEE ET AL.
2328
In poultry, however, HB processing has to be com pleted in 2°C, and 3) the amount of protein extracted from prerigor meat for 15 min was greater than the amount from postrigor muscle for 15 h. When prerigor meats were salted and ground with carbon dioxide, patties from the prerigor meat had higher pH, lower cooking loss, and firmer texture than those from postrigor control (Sorheim et al., 2006). Previously, our laboratory reported that the coldbatter mixing (7 min only) of turkey fillets that were hot-boned/quarter-sectioned and crust-frozen airchilled (HB-ViCFAC) generated higher stress and higher strain values in cooked gels than those of chill boned control or hot-boned/no-chilled muscles (Medellin-Lopez et al., 2014). Therefore, the purpose of this research was to evaluate the potential for protein func tionality improvement and sodium reduction capability by extending cold-batter mixing time for HB-UiCFAC fillets up to 24 min.
MATERIALS AND METHODS
Turkey Slaughter and Carcass Chilling In each of 4 visits, 36 Nicholas tom turkeys (ap proximately 16 wk old, ~18 kg turkey in live weight) were obtained locally and processed at the Michigan State University Meat Laboratory in 4 different days. The birds were electrically stunned for 3 s (80 mA, 60 Hz, 110 V) and bled for 90 s by severing both ca rotid artery and jugular vein on one side of the neck. The turkeys were then scalded (59°C, 120 s), mechani cally defeathered (25 s), and manually eviscerated. At approximately 15 min PM, all carcasses were weighed and core temperatures were recorded from the center of breast using a digital thermometer/logger (model 800024, Sper Scientific Ltd., Scottsdale, AZ). Following the temperature check, one-half of the carcasses were randomly subjected to an ice/water slurry tank (0.5°C) for water immersion chilling (W IC ) with mechanical agitation (0400-025GV1S portable agitator, Grovhac
Inc., Brookfield, WI) until the internal breast tempera ture reaches 4°C, which took about 5.5 h. The remain ing carcasses were subjected to HB-PiCFAC in an air freezing room (—12°C) as described by Medellin-Lopez et al. (2014). Briefly, breast fillets were hot-boned at 15 min PM, cut into quarter portions, and hung by hooks on a stainless steel rack. The resulting fillets were exposed to a continuous air flow (1.0 m/s) until the internal temperature reached 4°C, which took about 1 h. Immediately after chilling, the crust-frozen breasts were chopped for a cold-batter mincing (using ice for all batch water), whereas the chill-boned breasts from WIC were chopped in a traditional method (using 20% ice/80% water for batch water) the following day.
pH and R-value For pH and R-values, breast samples (5 x 50 x 80 mm) were obtained at the cranial end of the left fillet before chilling at 15 min PM, after HB-ViCFAC at 75 min PM, or 345 min PM in WIC fillets. The pH value of breast muscle was measured with a pH electrode (mod el 13-620-631, Fisher Scientific Inc., Houston, TX) at tached to a pH meter (Accumet AR15, Fisher Scientific Inc., Pittsburgh, PA) after homogenizing 2.5 g of raw meat in 25 mL of distilled, deionized water (Sams and Janky, 1986). The R-value (ratio of inosine:adenosine) was measured as an indicator of adenosine triphosphate depletion in the muscle using the method of Thompson et al. (1987).
Breast Mincing and Gel Preparation Immediately after chilling, the HB-IACFAC fillets (78% batch weight) were minced with 20% ice/2% salt or 21% ice/1% salt using a bowl chopper (model K64Va, Maschinenfabrik Seydelmann KG, Aalen, Germa ny) at a blade speed of 4,000 rpm, whereas the WIC carcasses were chill-boned and stored at 4°C overnight. Following the day, the chill-boned fillets (78% batch weight) were minced traditionally with 16% water/4% ice/2% salt or 17% water/4% ice/1% salt. During minc ing, the meat batter temperature was recorded and batter samples were saved at every 3 min from 6 to 27 min mincing. The minced batters were turned into cooked gels using the method of Jeong et al. (2011). Briefly, batters were stuffed into preweighed stainless steel cylindrical tubes, reweighed, and put into a wa ter bath (model 25, Precision Scientific Co., Chicago, IL) at 80°C for 20 min. After cooking, the tubes were immediately chilled, sealed in plastic bags, and stored overnight in a refrigerated room (3°C).
Torsion Test The gels in refrigerator were placed at room tem perature for 2 h and cut perpendicularly to a length of 3.0 cm, to which styrene disks were glued. The samples were then milled into a dumbbell shape (10 mm in di-
SODIUM REDUCTION IN PROCESSED MEATS
ameter at the midsection) by using a shaping machine (KCI-24A2, Bodine Electric Co., Raleigh, NC). Each specimen was placed on the sample holding apparatus in a viscometer (DV-III Ultra, Brookfield Engineering Laboratories Inc., Middleboro, MA) and twisted at 2.5 rpm. At the breaking point, both shear stress and shear strain were calculated with the recorded torque and elapsed time using the equations of Hamann (1983). Ten specimens were evaluated for each treatment for 3 separate replications.
Protein Solubility Determination For protein solubility determination, duplicate 10-g batter samples were added to a 4 vol extraction buffer (0.1 M NaCl, 0.05 M sodium phosphate, pH 6.0, 5 mM EDTA, and 1 mM NaN3) and stomached for 60 s. Du plicate aliquots (1 mL) were removed and centrifuged at 12,000 x g for 5 min at 4°C. Protein concentration from the resulting supernatants and batter samples were determined using a Bradford protein assay (Brad ford, 1976) and a nitrogen analyzer (model FP 2000, Leco Corp., St. Joseph, MI), respectively.
Scanning Electron Microscopy For scanning electron microscopy evaluation, both meat batters and cooked gels (3 mm x 3 mm x 3 mm cube) were fixed at 4°C for 2 h in 4% glutaraldehyde buffered with 0.1 M sodium phosphate at pH 7.4. Following a brief rinse in the buffer, samples were postfixed in 1% osmium tetroxide buffered with 0 . 1 1 sodium phosphate for a minimum of 4 h. Samples were then briefly rinsed in 0.1 M phosphate buffer and de hydrated by exchanging with graded ethanol series (25, 50, 75, and 95%) for 1 h at each gradation with addi tional three 1-h changes in 100% ethanol. The resulting samples were then mounted on aluminum stubs using carbon suspension cement (SPI Supplies, West Ches ter, PA) and coated with osmium (—10 nm thickness) in an NEOC-AT osmium coater (Meiwafosis Co. Ltd., Osaka, Japan). Samples on the aluminum stubs were examined in a JEOL JSM-7500F (cold field emission electron emitter) scanning electron microscope (JEOL Ltd., Tokyo, Japan).
Statistical Analysis All experiments were replicated 4 times. Data were evaluated by one-way ANOVA, using the PASW 18 sta tistic program and a completely randomized design. A post-hoc analysis was performed using Duncan’s multi ple range test to evaluate differences among treatments at P < 0.05 (SPSS, 2011). RESULTS AND DISCUSSION The initial temperature (41.3°C) of eviscerated tur key carcasses continuously decreased to 4°C, with the
2329
T able 1.pH and R-value (iS E M )1 of turkey breasts before and after being chill-boned (CB) or hot-boned/quarter-sectioned/ crust-frozen air-chilled (HB-ViCFAC) Parameter/chilling pH before chill2 pH after chill3 R-value before chill2 R-value after chill3
6.04 5.73 1.01 1.32
CB
HB-VrCFAC
± ± ± ±
6.14 5.94 0.98 1.19
0.18a 0.09b 0.09a 0.05a
± ± ± ±
0.21a 0.10a 0.08a 0.13b
a’bMeans within a row with unlike superscripts are different (P < 0.05). 1The number of observations in each chilling for each part, n = 16. 2Measured at 15 min postmortem. 3Measured at 345 min postmortem for CB fillets and 75 min postmor tem for HB-ViCFAC fillets.
average chilling times of 5.5 and 1 h for the carcasses of WIC and IIB-ViCFAC, respectively (data not in cluded). These results were similarly noticed by Medellin-Lopez et al. (2014) who evaluated chilling efficacy of turkey carcasses in WIC and hot-boned/crust-frozen fillets with/without 14-sectioning in an air-freezing room (—12°C, 1 m/s). Before chilling, no significant differences were found for pH (6.04-6.14) and R-values (0.98-1.01) in the carcass fillets assigned for HB and CB (Table 1). After hot or chill boning, HB-ViCFAC fillets had higher pH (5.94) and lower R-value (1.19; P < 0.05) than those (pH 5.73, R-value 1.32) of CB fillets (Table 1), indicating that less glucose and adenosine triphosphate have been hydrolyzed in the HB-ViCFAC fillets, primarily due to a shorter PM time (15 min) than that (345 min) of CB fillets. Alvarado and Sams (2000) reported that turkey breasts at 15 min PM had higher pH (6.33) and lower R-value (0.94) than those (pH 5.91, R-value 1.3) of 24 h PM fillets. After chilling, breast fillets were minced with 1 or 2% salt for batter preparation. For cold-batter minc ing, HB-1/4CFAC fillets (surface temperature at —1.5 to —3.5°C) were minced with 2% salt/20% ice or 1% salt/21% ice, whereas CB fillets (surface temperature at —0.5°C) were traditionally minced with 2% salt/4% ice/16% water or 1% salt/4% ice/17% water. During mincing, the temperatures of traditionally minced bat ter sharply increased to 17 to 18°C at 6 min, whereas those of cold-mincing batter remained at < —1°C (Fig ure 1). After 6 min, the temperature of cold-minced batter started to increase and resulted in no significant difference (P > 0.05) from the traditionally minced batters at 15 min for 2% salt and 24 min for 1% salt (Figure 1). Regarding the chopping time and batter temperature in traditional mincing, Deng et al. (1981) reported that the batter temperature increased to 16 and to 33°C at 5 and 20 to 25 min of mincing, respec tively, which supports our results of traditional batters. At 6 min of mincing, the pH (5.97) of 2% salt HBlACFAC batter was higher (P < 0.05) than that (pH 5.82) of 1% salt CB batter, with intermediate values (pH 5.83-5.90) seen for the 2% CB and 1% salt HBViCFAC batters. After 6 min, the pH of 1 and 2% salt HB-14CFAC batters continuously decreased and
2330
LEE ET AL.
6
9
12
15
18
21
24
27
Mixing time (min) Figure 1. Temperature change of meat batters during 27 min of mincing of turkey fillets that were chill-boned (CB) or hot-boned/quartersectioned/crust-frozen air-chilled (HB-VICFAC). Means (n = 8) with no common letters (a-c) within the same mixing time differ (P < 0.05).
showed no difference (P > 0.05) from the CB batters, regardless of salt content, whereas the lowest pH (5.685.52) was seen for the 1% salt HB-1ACFAC batter from 15 min to the rest of mincing (Figure 2). Unlike the HB-V^CFAC, the pH of CB batters re mained constant in the range of 5.8 ± 0.2 throughout the mixing period, regardless of salt content. As a re sult, the CB batter pH was the same as the 2% salt
HB-ViCFAC batter and significantly higher (P < 0.05) than the 1% salt IIB-ViCFAC batter after 15 min of mincing. It has been known that the pH of prerigor meat rapidly drops when the meat is ground or turned into batter. Newbold and Scopes (1971) reported that the pH of minced prerigor beef decreased from 6.7 to 5.4-5.5 during 400 min of storage, whereas the intake muscle remained the pH in 6.3 to 6.4. Bernthal et al.
Figure 2. pH change of meat batters during 27 min of mincing of turkey fillets that were chill-boned (CB) or hot-boned/quarter-sectioned/ crust-frozen air-chilled (HB-!4CFAC). Means (n = 8) with no common letters (a,b) within the same mixing time differ (P < 0.05).
SODIUM REDUCTION IN PROCESSED MEATS (1989) also observed th at beef muscle pH was signifi cantly reduced when prerigor muscles were ground and stored, whereas a high pH was seen at a high NaCl concentration. Hamm (1977) reported th at grinding of prerigor beef muscle with 2 to 4% sodium chloride in hibited glycolysis after several hours PM due to the denaturation of glycolytic enzymes in low pH (
ate sodium reduction in the protein gels that were pre pared with turkey breasts after hot boning (HB), quar ter (id) sectioning, crust-frozen air-chilling (CFAC), and cold temperature mincing. For each of 4 replica tions, 36 turkeys were slaughtered and eviscerated. Onehalf of the carcasses were randomly assigned to water immersion chilling for chill boning (CB), whereas the remaining carcasses were immediately HB and quartersectioned/crust-frozen air-chilled (HB-ldCFAC) in a freezing room (-12°C, 1.0 m/s). After deboning, CB fil lets were conventionally minced, whereas HB-Id CFAC fillets were cold minced up to 27 min with 1 or 2% salt. From the beginning of mincing, the batter tem peratures of HB-y4CFAC were lower (P < 0.05) than those of CB batters up to 12 and 21 min for 2 and 1% salts, respectively. Upon mincing, the batter pH of the HB-14CFAC (P < 0.05) rapidly decreased and
was not different (P > 0.05) from the pH of CB bat ters, except for the 1% salt HB-Id CFAC batter after 15 min of mincing. The pattern of pH was not changed when the batters were stored overnight. The protein of 2% salt HB-Id CFAC fillets was more extractable (P < 0.05) than that of CB fillets at 9, 12, 18, and 24 min. Similarly, the protein of 1% salt HB-Id CFAC fillets was more extractable (P < 0.05) than that of CB fillets from 12 min. Stress values of 2% salt HB-Id CFAC gels were higher (P < 0.05) than those of 1 and 2% salt CB gels, with intermediate values for 1% salt HB-UiCFAC gels. In the scanning electron microscope image, prerig or batter appears to have more open space, less protein aggregation, and more protein-coated fat particles than those of postrigor batters. Based on these results, the combination of HB-Id CFAC and cold-batter-mincing technologies appear to improve protein functionality and sodium reduction capacity.
K ey words: sodium reduction, hot boning, crust freezing, cold mincing, protein functionality 2014 Poultry Science 93:2327-2336 http://dx.doi.org/10.3382/ps.2014-03915
INTRODUCTION Over the past 25 yr in the United States, the aver age salt intake has increased approximately 56%, partly because people are eating more processed and prepack aged products than ever before. The largest portion (77%) of salt in the American diet comes from pro cessed products and restaurant foods (Mattes and Don nelly, 1991). As a result, most Americans are consuming excessive amounts of salt, which can lead to negative health effects. To solve this issue, meat processors are challenged on how sodium levels can be reduced in their products while maintaining product characteristics and quality. In processed meats, salt (NaCl) not only con tributes flavor and shelf-life extension, but also plays a
©2014 Poultry Science Association Inc. Received January 17, 2014. Accepted May 10, 2014. Corresponding author: [email protected]
major role in enhancing protein functionality, thereby developing a desirable texture. As a result, salt reduc tion without food quality loss is a significant technical challenge. Alternative methods of meat processing need to be evaluated for their ability to enhance or maintain product quality with reduced salt levels. Hot boning (HB) or prerigor processing has been known to generate superior quality to chill boning (CB) for raw and processed meat products (Kastner, 1977; Cuthbertson, 1980). Froning and Neelakantan (1971) reported that the meat batter made with prerigor mus cle exhibited higher emulsifying capacity and emulsion stability than that of postrigor muscle. A higher cook ing yield was observed from hot cuts than chill cuts in broiler meat (Wyche and Goodwin, 1974). Due to the rapid muscle retrieval from carcasses after slaughter, the HB processing has been known for many advan tages such as energy saving, high processing yield, high throughput, reduced chilling time, and chilling space (Lyon and Hamm, 1986; McPhail, 1995).
2327
LEE ET AL.
2328
In poultry, however, HB processing has to be com pleted in 2°C, and 3) the amount of protein extracted from prerigor meat for 15 min was greater than the amount from postrigor muscle for 15 h. When prerigor meats were salted and ground with carbon dioxide, patties from the prerigor meat had higher pH, lower cooking loss, and firmer texture than those from postrigor control (Sorheim et al., 2006). Previously, our laboratory reported that the coldbatter mixing (7 min only) of turkey fillets that were hot-boned/quarter-sectioned and crust-frozen airchilled (HB-ViCFAC) generated higher stress and higher strain values in cooked gels than those of chill boned control or hot-boned/no-chilled muscles (Medellin-Lopez et al., 2014). Therefore, the purpose of this research was to evaluate the potential for protein func tionality improvement and sodium reduction capability by extending cold-batter mixing time for HB-UiCFAC fillets up to 24 min.
MATERIALS AND METHODS
Turkey Slaughter and Carcass Chilling In each of 4 visits, 36 Nicholas tom turkeys (ap proximately 16 wk old, ~18 kg turkey in live weight) were obtained locally and processed at the Michigan State University Meat Laboratory in 4 different days. The birds were electrically stunned for 3 s (80 mA, 60 Hz, 110 V) and bled for 90 s by severing both ca rotid artery and jugular vein on one side of the neck. The turkeys were then scalded (59°C, 120 s), mechani cally defeathered (25 s), and manually eviscerated. At approximately 15 min PM, all carcasses were weighed and core temperatures were recorded from the center of breast using a digital thermometer/logger (model 800024, Sper Scientific Ltd., Scottsdale, AZ). Following the temperature check, one-half of the carcasses were randomly subjected to an ice/water slurry tank (0.5°C) for water immersion chilling (W IC ) with mechanical agitation (0400-025GV1S portable agitator, Grovhac
Inc., Brookfield, WI) until the internal breast tempera ture reaches 4°C, which took about 5.5 h. The remain ing carcasses were subjected to HB-PiCFAC in an air freezing room (—12°C) as described by Medellin-Lopez et al. (2014). Briefly, breast fillets were hot-boned at 15 min PM, cut into quarter portions, and hung by hooks on a stainless steel rack. The resulting fillets were exposed to a continuous air flow (1.0 m/s) until the internal temperature reached 4°C, which took about 1 h. Immediately after chilling, the crust-frozen breasts were chopped for a cold-batter mincing (using ice for all batch water), whereas the chill-boned breasts from WIC were chopped in a traditional method (using 20% ice/80% water for batch water) the following day.
pH and R-value For pH and R-values, breast samples (5 x 50 x 80 mm) were obtained at the cranial end of the left fillet before chilling at 15 min PM, after HB-ViCFAC at 75 min PM, or 345 min PM in WIC fillets. The pH value of breast muscle was measured with a pH electrode (mod el 13-620-631, Fisher Scientific Inc., Houston, TX) at tached to a pH meter (Accumet AR15, Fisher Scientific Inc., Pittsburgh, PA) after homogenizing 2.5 g of raw meat in 25 mL of distilled, deionized water (Sams and Janky, 1986). The R-value (ratio of inosine:adenosine) was measured as an indicator of adenosine triphosphate depletion in the muscle using the method of Thompson et al. (1987).
Breast Mincing and Gel Preparation Immediately after chilling, the HB-IACFAC fillets (78% batch weight) were minced with 20% ice/2% salt or 21% ice/1% salt using a bowl chopper (model K64Va, Maschinenfabrik Seydelmann KG, Aalen, Germa ny) at a blade speed of 4,000 rpm, whereas the WIC carcasses were chill-boned and stored at 4°C overnight. Following the day, the chill-boned fillets (78% batch weight) were minced traditionally with 16% water/4% ice/2% salt or 17% water/4% ice/1% salt. During minc ing, the meat batter temperature was recorded and batter samples were saved at every 3 min from 6 to 27 min mincing. The minced batters were turned into cooked gels using the method of Jeong et al. (2011). Briefly, batters were stuffed into preweighed stainless steel cylindrical tubes, reweighed, and put into a wa ter bath (model 25, Precision Scientific Co., Chicago, IL) at 80°C for 20 min. After cooking, the tubes were immediately chilled, sealed in plastic bags, and stored overnight in a refrigerated room (3°C).
Torsion Test The gels in refrigerator were placed at room tem perature for 2 h and cut perpendicularly to a length of 3.0 cm, to which styrene disks were glued. The samples were then milled into a dumbbell shape (10 mm in di-
SODIUM REDUCTION IN PROCESSED MEATS
ameter at the midsection) by using a shaping machine (KCI-24A2, Bodine Electric Co., Raleigh, NC). Each specimen was placed on the sample holding apparatus in a viscometer (DV-III Ultra, Brookfield Engineering Laboratories Inc., Middleboro, MA) and twisted at 2.5 rpm. At the breaking point, both shear stress and shear strain were calculated with the recorded torque and elapsed time using the equations of Hamann (1983). Ten specimens were evaluated for each treatment for 3 separate replications.
Protein Solubility Determination For protein solubility determination, duplicate 10-g batter samples were added to a 4 vol extraction buffer (0.1 M NaCl, 0.05 M sodium phosphate, pH 6.0, 5 mM EDTA, and 1 mM NaN3) and stomached for 60 s. Du plicate aliquots (1 mL) were removed and centrifuged at 12,000 x g for 5 min at 4°C. Protein concentration from the resulting supernatants and batter samples were determined using a Bradford protein assay (Brad ford, 1976) and a nitrogen analyzer (model FP 2000, Leco Corp., St. Joseph, MI), respectively.
Scanning Electron Microscopy For scanning electron microscopy evaluation, both meat batters and cooked gels (3 mm x 3 mm x 3 mm cube) were fixed at 4°C for 2 h in 4% glutaraldehyde buffered with 0.1 M sodium phosphate at pH 7.4. Following a brief rinse in the buffer, samples were postfixed in 1% osmium tetroxide buffered with 0 . 1 1 sodium phosphate for a minimum of 4 h. Samples were then briefly rinsed in 0.1 M phosphate buffer and de hydrated by exchanging with graded ethanol series (25, 50, 75, and 95%) for 1 h at each gradation with addi tional three 1-h changes in 100% ethanol. The resulting samples were then mounted on aluminum stubs using carbon suspension cement (SPI Supplies, West Ches ter, PA) and coated with osmium (—10 nm thickness) in an NEOC-AT osmium coater (Meiwafosis Co. Ltd., Osaka, Japan). Samples on the aluminum stubs were examined in a JEOL JSM-7500F (cold field emission electron emitter) scanning electron microscope (JEOL Ltd., Tokyo, Japan).
Statistical Analysis All experiments were replicated 4 times. Data were evaluated by one-way ANOVA, using the PASW 18 sta tistic program and a completely randomized design. A post-hoc analysis was performed using Duncan’s multi ple range test to evaluate differences among treatments at P < 0.05 (SPSS, 2011). RESULTS AND DISCUSSION The initial temperature (41.3°C) of eviscerated tur key carcasses continuously decreased to 4°C, with the
2329
T able 1.pH and R-value (iS E M )1 of turkey breasts before and after being chill-boned (CB) or hot-boned/quarter-sectioned/ crust-frozen air-chilled (HB-ViCFAC) Parameter/chilling pH before chill2 pH after chill3 R-value before chill2 R-value after chill3
6.04 5.73 1.01 1.32
CB
HB-VrCFAC
± ± ± ±
6.14 5.94 0.98 1.19
0.18a 0.09b 0.09a 0.05a
± ± ± ±
0.21a 0.10a 0.08a 0.13b
a’bMeans within a row with unlike superscripts are different (P < 0.05). 1The number of observations in each chilling for each part, n = 16. 2Measured at 15 min postmortem. 3Measured at 345 min postmortem for CB fillets and 75 min postmor tem for HB-ViCFAC fillets.
average chilling times of 5.5 and 1 h for the carcasses of WIC and IIB-ViCFAC, respectively (data not in cluded). These results were similarly noticed by Medellin-Lopez et al. (2014) who evaluated chilling efficacy of turkey carcasses in WIC and hot-boned/crust-frozen fillets with/without 14-sectioning in an air-freezing room (—12°C, 1 m/s). Before chilling, no significant differences were found for pH (6.04-6.14) and R-values (0.98-1.01) in the carcass fillets assigned for HB and CB (Table 1). After hot or chill boning, HB-ViCFAC fillets had higher pH (5.94) and lower R-value (1.19; P < 0.05) than those (pH 5.73, R-value 1.32) of CB fillets (Table 1), indicating that less glucose and adenosine triphosphate have been hydrolyzed in the HB-ViCFAC fillets, primarily due to a shorter PM time (15 min) than that (345 min) of CB fillets. Alvarado and Sams (2000) reported that turkey breasts at 15 min PM had higher pH (6.33) and lower R-value (0.94) than those (pH 5.91, R-value 1.3) of 24 h PM fillets. After chilling, breast fillets were minced with 1 or 2% salt for batter preparation. For cold-batter minc ing, HB-1/4CFAC fillets (surface temperature at —1.5 to —3.5°C) were minced with 2% salt/20% ice or 1% salt/21% ice, whereas CB fillets (surface temperature at —0.5°C) were traditionally minced with 2% salt/4% ice/16% water or 1% salt/4% ice/17% water. During mincing, the temperatures of traditionally minced bat ter sharply increased to 17 to 18°C at 6 min, whereas those of cold-mincing batter remained at < —1°C (Fig ure 1). After 6 min, the temperature of cold-minced batter started to increase and resulted in no significant difference (P > 0.05) from the traditionally minced batters at 15 min for 2% salt and 24 min for 1% salt (Figure 1). Regarding the chopping time and batter temperature in traditional mincing, Deng et al. (1981) reported that the batter temperature increased to 16 and to 33°C at 5 and 20 to 25 min of mincing, respec tively, which supports our results of traditional batters. At 6 min of mincing, the pH (5.97) of 2% salt HBlACFAC batter was higher (P < 0.05) than that (pH 5.82) of 1% salt CB batter, with intermediate values (pH 5.83-5.90) seen for the 2% CB and 1% salt HBViCFAC batters. After 6 min, the pH of 1 and 2% salt HB-14CFAC batters continuously decreased and
2330
LEE ET AL.
6
9
12
15
18
21
24
27
Mixing time (min) Figure 1. Temperature change of meat batters during 27 min of mincing of turkey fillets that were chill-boned (CB) or hot-boned/quartersectioned/crust-frozen air-chilled (HB-VICFAC). Means (n = 8) with no common letters (a-c) within the same mixing time differ (P < 0.05).
showed no difference (P > 0.05) from the CB batters, regardless of salt content, whereas the lowest pH (5.685.52) was seen for the 1% salt HB-1ACFAC batter from 15 min to the rest of mincing (Figure 2). Unlike the HB-V^CFAC, the pH of CB batters re mained constant in the range of 5.8 ± 0.2 throughout the mixing period, regardless of salt content. As a re sult, the CB batter pH was the same as the 2% salt
HB-ViCFAC batter and significantly higher (P < 0.05) than the 1% salt IIB-ViCFAC batter after 15 min of mincing. It has been known that the pH of prerigor meat rapidly drops when the meat is ground or turned into batter. Newbold and Scopes (1971) reported that the pH of minced prerigor beef decreased from 6.7 to 5.4-5.5 during 400 min of storage, whereas the intake muscle remained the pH in 6.3 to 6.4. Bernthal et al.
Figure 2. pH change of meat batters during 27 min of mincing of turkey fillets that were chill-boned (CB) or hot-boned/quarter-sectioned/ crust-frozen air-chilled (HB-!4CFAC). Means (n = 8) with no common letters (a,b) within the same mixing time differ (P < 0.05).
SODIUM REDUCTION IN PROCESSED MEATS (1989) also observed th at beef muscle pH was signifi cantly reduced when prerigor muscles were ground and stored, whereas a high pH was seen at a high NaCl concentration. Hamm (1977) reported th at grinding of prerigor beef muscle with 2 to 4% sodium chloride in hibited glycolysis after several hours PM due to the denaturation of glycolytic enzymes in low pH (
