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A Modification of a Method to Determine Expressible Moisture in Ground, Dark Poultry Meat
PROCESSING AND PRODUCTS A Modification of a Method to Determine Expressible Moisture in Ground, Dark Poultry Meat L. A. EARL,* A. J. KING, D. P. FITZPATRICK and J. E. COOPER *Department of Avian Sciences, University of California, Davis, California 95616 w r a p p e d in n e t t i n g a n d a n a l y z e d for expressible moisture. The fold wrap method was determined to be more accurate and easier to use, as less expressed meat adhered to the surrounding filter papers. Thus, actual expressed moisture absorbed by filter papers was measured.
(Key words: expressible moisture, turkey, chicken, meat, netting) 1996 Poultry Science 75:1433-1436
INTRODUCTION Functional properties of proteins in food are related to the manner in which protein systems associate with water (Chou and Morr, 1979). Expressible moisture is one measurement of the water-holding capacity of food protein systems (Vadehra et ah, 1973; Chou and Morr, 1979; Regenstein et al, 1979). Jauregui et al. (1981) defined expressible moisture as the amount of liquid squeezed from a protein system by the application of force and measures the amount of loose water released under the measurement conditions. Their method measured the weight gain of filter papers surrounding ground meat after centrifugation to express moisture. This method is simple and allows simultaneous multiple sampling of treatments. Although the method has been widely used by meat scientists, it has been found that ground poultry meat particles can adhere to the papers after centrifugation (Sackett et al, 1986; Maki and Froning, 1987; J. M. Regenstein, 1993, Cornell University, Ithaca, NY 14853, personal communication; J. C. Acton, 1995, Clemson University, Clemson, SC 29634, personal communication). Thus, an accurate measurement of moisture is difficult to obtain.
MATERIALS AND METHODS The method of Jauregui et al. (1981) was used with and without modifications. Their method utilized three pieces of Whatman 1 Number 3 (5.5 cm) filter paper plus
Received for publication January 30, 1996. Accepted for publication July 1, 1996. iFisher Scientific, Santa Clara, CA 95059. 2 Sorvall model RC2-B, Newtown, CT 06470.
one piece of Whatman 1 Number 50 (7.0 cm) filter paper, as the top layer, formed into a thimble by shaping them around the bottom of a 17 x 100 mm test tube. In this work, the paper thimble was weighed and approximately 1.5 g of ground, dark poultry meat (obtained fresh from a local processor), either chicken or turkey thigh, with and without 2.0% NaCl (King and Earl, 1988a) was weighed onto the thimble. The meat and thimble package was inserted into a 50-mL polycarbonate centrifuge tube and centrifuged 2 at 14,000 rpm x 15 min at 4 C. The thimble package was removed with tweezers and the meat was discarded. The paper thimble with moisture was weighed and expressible moisture was reported as the percentage weight lost from the original sample. The method of Juaregui et al. (1981) was modified with the addition of a 15 cm 2 piece of white tulle netting, 0.1 mm mesh, (obtained from a local fabric shop), which was used to hold the meat. This netting served to create a permeable barrier between the meat and the papers. The netting was either wrapped and folded around the variously treated meat (fold wrap), (Figure 1) or folded into four layers and formed into a basket shape (basket wrap). For the fold wrap method, the meat was placed in the center of the netting (Figure la). The ends were brought together to form a rectangle with the meat in the center and bottom of the rectangle (Figure lb). The bottom edges of the netting were folded upward with the meat (Figure lc) in several turns until reaching the top edges (Figure Id). The excess netting at the sides of the meat were folded over and under the meat (Figure le). This technique formed a completely
1433
Downloaded from http://ps.oxfordjournals.org/ at Purdue University Libraries ADMN on July 1, 2015
ABSTRACT Research was conducted to develop a more accurate and less time-consuming method of determining expressible moisture in poultry meat. Two modifications of wrapping meat in netting (fold wrap or basket wrap) were compared to a conventional method that did not include wrapping m e a t Ground, dark poultry meat, with and without 2.0% added NaCl, was
1434
EARL ET
Ah.
Downloaded from http://ps.oxfordjournals.org/ at Purdue University Libraries ADMN on July 1, 2015
FIGURE 1. Stages of Fold Wrap, a) meat placed on center of netting, netting around meat package, f) finished fold wrap package.
formation of rectangle, c to d) folding of netting, e) wrapping ends of
covered package with seven or more layers of netting (Figure If). This package, containing meat plus netting, was placed in the weighed paper thimble and centrifuged as above. For the second method, basket wrap, the netting was folded into four layers and shaped around the bottom of a 17 x 100 mm test tube. This wrap formed a "basket"
shape and the meat sample was placed on the netting but was not completely covered. This meat plus netting package was placed in the weighed paper thimble and centrifuged as above. For all samples, any meat expressed through the netting layers was scraped carefully off the papers using a small metal spatula. It was necessary to remove the
RESEARCH NOTE
1435
TABLE 1. Comparison of various methods of expressible moisture determination of dark meat poultry 1 Expressible moisture Source
Treatment
No netting
Fold wrap
Basket wrap
1°') Turkey Turkey Chicken Chicken
Without NaCl With NaCl Without NaCl With NaCl
29.93 19.13 34.82 32.14
± ± ± +
6.65 3.77 3.74 6.50
30.81 17.86 40.97 24.28
± ± ± ±
5.01 3.08 4.16 4.93
32.11 17.55 38.19 24.33
+ ± ± ±
4.42 3.85 5.16 2.22
iMeans within rows are not significantly different (P < 0.05); n - 16 for ground, dark turkey meat and n = 8 for ground, dark chicken meat.
% Expressible Moisture =
weight of moisture expressed original weight of meat
Time needed to scrape expressed meat from the papers and the amount of meat scraped were measured. Statistical analyses were performed for all expressible moisture data using the MSTAT computer program (Power, 1983). For chicken meat, two runs of the analyses were conducted using four samples in duplicate replication. For turkey meat, two runs of eight samples in duplicate replication were conducted. For each treatment and meat type an analysis of variance was performed on expressible moisture (P < 0.05).
RESULTS AND DISCUSSION Various combinations of wrapping and folding of the netting were compared to maximize the moisture permeating to the filter papers while minimizing any meat expression through the netting. There were no significant differences in expressible moisture within treatment when the wrapping methods were compared to the method of Jauregui et al. (1981) (Table 1). However, if netting was not used, intact meat particles would cling to the papers and these particles were difficult to remove.
When samples were wrapped in netting, little to no meat was expressed through the netting and adhered to the papers (Table 2). Table 2 shows representative results from observations of ground, dark unsalted turkey meat. When no netting was used, all meat was scraped from the filter papers. The amount of meat scraped and the time needed to remove the meat from the papers was different from that of measurements of fold wrap and basket wrap. No meat was expressed through fold wrap netting; however, the papers were carefully examined and this time is noted. The original data showed that the range of total time to examine papers from fold wrap netting was 0 to 20 s and that for basket wrap was 0 to 60 s. As a practical matter, the fold wrap method is recommended because no meat was expressed with this method. Figure 2 shows representative samples of filter papers after centrifugation with either fold wrap or basket wrap netting used with ground chicken meat. When NaCl was added to meat it extracted myofibril proteins, producing an increased binding capacity (King and Earl, 1988b). This property caused expressed meat to have greater adherence to the filter papers. As shown for unsalted meat (Table 2), the use of netting for salted meat with either fold wrap or basket wrap reduced the adherence because less meat was expressed (Earl et al., 1996, unpublished data). Wrapping meat in tulle netting by either fold wrap or basket wrap enhanced the reproduceability of the measurement of expressible moisture. Fold wrap was adopted as the method of choice because no meat was expressed through the netting. Because of this increase in accuracy and the reduction in time needed to remove
TABLE 2. Objective measurements used in optimizing methodology for expressible moisture
Measurement
Meat scraped from filter papers
Time needed to scrape meat
No netting Fold wrap Basket wrap
(S) 0.986 ± 0.15a 0.0b 0.009 + 0.02b
(s) 117.50 + 38.26a 5.53 ± 8.40b 18.16 + 21.26b
a b
- Means within a column with no common superscript differ significantly (P < 0.05). Results for ground, dark, unsalted turkey meat shown; n = 32.
Downloaded from http://ps.oxfordjournals.org/ at Purdue University Libraries ADMN on July 1, 2015
expressed meat from the papers before determining the amount of moisture actually absorbed by the papers. The amount of moisture absorbed by the papers was used to calculate percentage expressible moisture, where:
EARL ET AL.
1436
Filter Papers from Basket Wrap Netting
FIGURE 2. Filter papers used with Fold Wrap and Basket Wrap netting after centrifugation. Expressed meat particles are shown clinging to papers used with Basket Wrap netting.
m e a t from filter p a p e r s it is possible to analyze m o r e s a m p l e s in a given a m o u n t of time. This a d v a n t a g e m a y b e m o r e p r o n o u n c e d w h e n NaCl is a d d e d to g r o u n d , d a r k p o u l t r y m e a t samples.
REFERENCES Chou, D. H., and C. V. Morr, 1979. Protein-water interactions and functional properties. J. Am. Oil Chem. Soc. 56: 53A-62A. Jauregui, C. A., J. M. Regenstein, and R. C. Baker, 1981. A simple centrifugal method for measuring expressible moisture, a water-binding property of muscle foods. J. Food Sci. 46:1271-1273. King, A. J., and L. A. Earl, 1988a. Effect of selected sodium and potassium salts on TBA values of dark meat turkey patties. J. Food Sci. 535:723-726.
King, A. ]., and L. A. Earl, 1988b. Extraction of protein from slurries of unfrozen and frozen/thawed dark, ground turkey meat and skin. J. Food Sci. 53:1290-1293. Power, P., 1983. User's Guide to MSTAT Version 3.0 Michigan State University, East Lansing, MI. Maki, A., and G. W. Froning, 1987. Effect of post-mortem electrical stimulation on quality of turkey meat. Poultry Sci. 66:1155-1157. Regenstein, J. M., T. S. Gorimar, and J. W. Sherbon, 1979. Measuring the water-holding capacity of natural actomyosin from chicken breast muscle in the presence of pyrophosphate and divalent cations. J. Food Biochem. 3: 205-211. Sackett, B.A.M., G. W. Froning, J. A. Deshazer, and F. J. Struwe, 1986. Effect of gaseous preslaughter environment on chicken broiler meat quality. Poultry Sci. 65:511-519. Vadehra, D. V., M. W. Newbold, P. G. Schnell, and R. C. Baker, 1973. Effects of salt on the water holding capacity of poultry meat. Poultry Sci. 52:2359-2361.
Downloaded from http://ps.oxfordjournals.org/ at Purdue University Libraries ADMN on July 1, 2015
Filter Papers from Fold Wrap Netting
(Key words: expressible moisture, turkey, chicken, meat, netting) 1996 Poultry Science 75:1433-1436
INTRODUCTION Functional properties of proteins in food are related to the manner in which protein systems associate with water (Chou and Morr, 1979). Expressible moisture is one measurement of the water-holding capacity of food protein systems (Vadehra et ah, 1973; Chou and Morr, 1979; Regenstein et al, 1979). Jauregui et al. (1981) defined expressible moisture as the amount of liquid squeezed from a protein system by the application of force and measures the amount of loose water released under the measurement conditions. Their method measured the weight gain of filter papers surrounding ground meat after centrifugation to express moisture. This method is simple and allows simultaneous multiple sampling of treatments. Although the method has been widely used by meat scientists, it has been found that ground poultry meat particles can adhere to the papers after centrifugation (Sackett et al, 1986; Maki and Froning, 1987; J. M. Regenstein, 1993, Cornell University, Ithaca, NY 14853, personal communication; J. C. Acton, 1995, Clemson University, Clemson, SC 29634, personal communication). Thus, an accurate measurement of moisture is difficult to obtain.
MATERIALS AND METHODS The method of Jauregui et al. (1981) was used with and without modifications. Their method utilized three pieces of Whatman 1 Number 3 (5.5 cm) filter paper plus
Received for publication January 30, 1996. Accepted for publication July 1, 1996. iFisher Scientific, Santa Clara, CA 95059. 2 Sorvall model RC2-B, Newtown, CT 06470.
one piece of Whatman 1 Number 50 (7.0 cm) filter paper, as the top layer, formed into a thimble by shaping them around the bottom of a 17 x 100 mm test tube. In this work, the paper thimble was weighed and approximately 1.5 g of ground, dark poultry meat (obtained fresh from a local processor), either chicken or turkey thigh, with and without 2.0% NaCl (King and Earl, 1988a) was weighed onto the thimble. The meat and thimble package was inserted into a 50-mL polycarbonate centrifuge tube and centrifuged 2 at 14,000 rpm x 15 min at 4 C. The thimble package was removed with tweezers and the meat was discarded. The paper thimble with moisture was weighed and expressible moisture was reported as the percentage weight lost from the original sample. The method of Juaregui et al. (1981) was modified with the addition of a 15 cm 2 piece of white tulle netting, 0.1 mm mesh, (obtained from a local fabric shop), which was used to hold the meat. This netting served to create a permeable barrier between the meat and the papers. The netting was either wrapped and folded around the variously treated meat (fold wrap), (Figure 1) or folded into four layers and formed into a basket shape (basket wrap). For the fold wrap method, the meat was placed in the center of the netting (Figure la). The ends were brought together to form a rectangle with the meat in the center and bottom of the rectangle (Figure lb). The bottom edges of the netting were folded upward with the meat (Figure lc) in several turns until reaching the top edges (Figure Id). The excess netting at the sides of the meat were folded over and under the meat (Figure le). This technique formed a completely
1433
Downloaded from http://ps.oxfordjournals.org/ at Purdue University Libraries ADMN on July 1, 2015
ABSTRACT Research was conducted to develop a more accurate and less time-consuming method of determining expressible moisture in poultry meat. Two modifications of wrapping meat in netting (fold wrap or basket wrap) were compared to a conventional method that did not include wrapping m e a t Ground, dark poultry meat, with and without 2.0% added NaCl, was
1434
EARL ET
Ah.
Downloaded from http://ps.oxfordjournals.org/ at Purdue University Libraries ADMN on July 1, 2015
FIGURE 1. Stages of Fold Wrap, a) meat placed on center of netting, netting around meat package, f) finished fold wrap package.
formation of rectangle, c to d) folding of netting, e) wrapping ends of
covered package with seven or more layers of netting (Figure If). This package, containing meat plus netting, was placed in the weighed paper thimble and centrifuged as above. For the second method, basket wrap, the netting was folded into four layers and shaped around the bottom of a 17 x 100 mm test tube. This wrap formed a "basket"
shape and the meat sample was placed on the netting but was not completely covered. This meat plus netting package was placed in the weighed paper thimble and centrifuged as above. For all samples, any meat expressed through the netting layers was scraped carefully off the papers using a small metal spatula. It was necessary to remove the
RESEARCH NOTE
1435
TABLE 1. Comparison of various methods of expressible moisture determination of dark meat poultry 1 Expressible moisture Source
Treatment
No netting
Fold wrap
Basket wrap
1°') Turkey Turkey Chicken Chicken
Without NaCl With NaCl Without NaCl With NaCl
29.93 19.13 34.82 32.14
± ± ± +
6.65 3.77 3.74 6.50
30.81 17.86 40.97 24.28
± ± ± ±
5.01 3.08 4.16 4.93
32.11 17.55 38.19 24.33
+ ± ± ±
4.42 3.85 5.16 2.22
iMeans within rows are not significantly different (P < 0.05); n - 16 for ground, dark turkey meat and n = 8 for ground, dark chicken meat.
% Expressible Moisture =
weight of moisture expressed original weight of meat
Time needed to scrape expressed meat from the papers and the amount of meat scraped were measured. Statistical analyses were performed for all expressible moisture data using the MSTAT computer program (Power, 1983). For chicken meat, two runs of the analyses were conducted using four samples in duplicate replication. For turkey meat, two runs of eight samples in duplicate replication were conducted. For each treatment and meat type an analysis of variance was performed on expressible moisture (P < 0.05).
RESULTS AND DISCUSSION Various combinations of wrapping and folding of the netting were compared to maximize the moisture permeating to the filter papers while minimizing any meat expression through the netting. There were no significant differences in expressible moisture within treatment when the wrapping methods were compared to the method of Jauregui et al. (1981) (Table 1). However, if netting was not used, intact meat particles would cling to the papers and these particles were difficult to remove.
When samples were wrapped in netting, little to no meat was expressed through the netting and adhered to the papers (Table 2). Table 2 shows representative results from observations of ground, dark unsalted turkey meat. When no netting was used, all meat was scraped from the filter papers. The amount of meat scraped and the time needed to remove the meat from the papers was different from that of measurements of fold wrap and basket wrap. No meat was expressed through fold wrap netting; however, the papers were carefully examined and this time is noted. The original data showed that the range of total time to examine papers from fold wrap netting was 0 to 20 s and that for basket wrap was 0 to 60 s. As a practical matter, the fold wrap method is recommended because no meat was expressed with this method. Figure 2 shows representative samples of filter papers after centrifugation with either fold wrap or basket wrap netting used with ground chicken meat. When NaCl was added to meat it extracted myofibril proteins, producing an increased binding capacity (King and Earl, 1988b). This property caused expressed meat to have greater adherence to the filter papers. As shown for unsalted meat (Table 2), the use of netting for salted meat with either fold wrap or basket wrap reduced the adherence because less meat was expressed (Earl et al., 1996, unpublished data). Wrapping meat in tulle netting by either fold wrap or basket wrap enhanced the reproduceability of the measurement of expressible moisture. Fold wrap was adopted as the method of choice because no meat was expressed through the netting. Because of this increase in accuracy and the reduction in time needed to remove
TABLE 2. Objective measurements used in optimizing methodology for expressible moisture
Measurement
Meat scraped from filter papers
Time needed to scrape meat
No netting Fold wrap Basket wrap
(S) 0.986 ± 0.15a 0.0b 0.009 + 0.02b
(s) 117.50 + 38.26a 5.53 ± 8.40b 18.16 + 21.26b
a b
- Means within a column with no common superscript differ significantly (P < 0.05). Results for ground, dark, unsalted turkey meat shown; n = 32.
Downloaded from http://ps.oxfordjournals.org/ at Purdue University Libraries ADMN on July 1, 2015
expressed meat from the papers before determining the amount of moisture actually absorbed by the papers. The amount of moisture absorbed by the papers was used to calculate percentage expressible moisture, where:
EARL ET AL.
1436
Filter Papers from Basket Wrap Netting
FIGURE 2. Filter papers used with Fold Wrap and Basket Wrap netting after centrifugation. Expressed meat particles are shown clinging to papers used with Basket Wrap netting.
m e a t from filter p a p e r s it is possible to analyze m o r e s a m p l e s in a given a m o u n t of time. This a d v a n t a g e m a y b e m o r e p r o n o u n c e d w h e n NaCl is a d d e d to g r o u n d , d a r k p o u l t r y m e a t samples.
REFERENCES Chou, D. H., and C. V. Morr, 1979. Protein-water interactions and functional properties. J. Am. Oil Chem. Soc. 56: 53A-62A. Jauregui, C. A., J. M. Regenstein, and R. C. Baker, 1981. A simple centrifugal method for measuring expressible moisture, a water-binding property of muscle foods. J. Food Sci. 46:1271-1273. King, A. J., and L. A. Earl, 1988a. Effect of selected sodium and potassium salts on TBA values of dark meat turkey patties. J. Food Sci. 535:723-726.
King, A. ]., and L. A. Earl, 1988b. Extraction of protein from slurries of unfrozen and frozen/thawed dark, ground turkey meat and skin. J. Food Sci. 53:1290-1293. Power, P., 1983. User's Guide to MSTAT Version 3.0 Michigan State University, East Lansing, MI. Maki, A., and G. W. Froning, 1987. Effect of post-mortem electrical stimulation on quality of turkey meat. Poultry Sci. 66:1155-1157. Regenstein, J. M., T. S. Gorimar, and J. W. Sherbon, 1979. Measuring the water-holding capacity of natural actomyosin from chicken breast muscle in the presence of pyrophosphate and divalent cations. J. Food Biochem. 3: 205-211. Sackett, B.A.M., G. W. Froning, J. A. Deshazer, and F. J. Struwe, 1986. Effect of gaseous preslaughter environment on chicken broiler meat quality. Poultry Sci. 65:511-519. Vadehra, D. V., M. W. Newbold, P. G. Schnell, and R. C. Baker, 1973. Effects of salt on the water holding capacity of poultry meat. Poultry Sci. 52:2359-2361.
Downloaded from http://ps.oxfordjournals.org/ at Purdue University Libraries ADMN on July 1, 2015
Filter Papers from Fold Wrap Netting