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Utilization of pork collagen for functionality improvement of boneless cured ham manufactured from pale, soft, and exudative pork
Meat Science 65 (2003) 547–553 www.elsevier.com/locate/meatsci
Utilization of pork collagen for functionality improvement of boneless cured ham manufactured from pale, soft, and exudative pork M.W. Schillinga,*, L.E. Minkb, P.S. Gochenourc, N.G. Marriotta, C.Z. Alvaradoa a
Department of Food Science and Technology, Virginia Polytechnic Institute and State University, Blacksburg, VA 24061-0418, USA b Department of Animal Science, University of Nebraska, Lincoln, NE 68588, USA c Department of Poultry Science, Auburn University, Auburn, AL 36849, USA Received 13 May 2002; received in revised form 3 September 2002; accepted 3 September 2002
Abstract This study was designed to determine the effect of raw material and the inclusion of pork collagen on the protein functionality of boneless cured pork manufactured from 100% pale, soft, and exudative (PSE), 50% PSE, and 0% PSE with either 3 or 0% collagen. A Randomized Complete Block Design with six replications was utilized as the experimental design. Inclusion of collagen decreased (P< 0.05) expressible moisture and increased (P< 0.05) CIE b* value. Differences (P <0.05) revealed that collagen inclusion caused the 0% PSE treatments to have a lower cooking loss for 100% PSE treatments with and without collagen and a higher protein–protein bind value for 100% PSE treatments without collagen. Utilization of pork collagen in boneless cured pork that incorporates PSE meat increases water holding capacity and has the potential to improve protein functionality characteristics of the product. # 2003 Elsevier Science Ltd. All rights reserved. Keywords: PSE; Pork collagen; Ham; Functionality
1. Introduction Consumer desire for leaner meats has necessitated the production of pork with less fat. The intensive selection for leaner pigs in combination with stressful preslaughter and slaughter conditions has resulted in lower quality pork (Lee & Choi, 1998). This selection process has been responsible for the identification of genetic material that yields porcine muscle with a low pH, lighter color, and very soft and watery tissue. Genetic selection and pre-slaughter stress cause rapid postmortem glycolysis, which results in increased lactic acid production and decreased pH. Decreased pH combined with high muscle temperature (Camou & Sebranek, 1990) causes protein denaturation that exceeds that observed in normal muscle (Briskey & Wismer-Pedersen, 1961; Charpentier, 1969; Goutefongea, 1971; * Corresponding author. Tel.: +1-540-231-8679; fax: +1-540-2319293. E-mail address: [email protected] (M.W. Schilling).
Bowker, Wynveen, Grant, & Gerrard, 2000) leading to the production of pale, soft, and exudative (PSE) pork. Because of this protein denaturation, there is an increase in water loss that is detrimental to product quality (Offer, 1991). Young (1996) stated that customers will not buy a gray, wet product, and that appearance of pork is the most important attribute to the consumer. Since consumers will not accept fatter pork (Kauffman, Cassens, Scherer, & Meeker, 1992), this industry is challenged with the task of reducing the incidence of paleness without reducing leanness. A possible approach is to investigate the possibility of PSE pork utilization in the production of chunked and formed products. To increase the viability of this technique, color, waterholding capacity, bind, texture, and sensory attributes need to be improved from the raw material to the finished product. Two variables need to be examined to determine the optimal utilization of PSE pork in restructured products. First, the addition of non-meat adjuncts that can
0309-1740/03/$ - see front matter # 2003 Elsevier Science Ltd. All rights reserved. doi:10.1016/S0309-1740(02)00247-4
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M.W. Schilling et al. / Meat Science 65 (2003) 547–553
improve the functional characteristics of PSE pork should be explored (Schilling, Marriott, and Acton, 2001). Secondly, it will not be possible to manufacture an acceptable product from 100% PSE pork (Pearson and Gillett, 1996). To formulate an acceptable restructured product, the concentration of red, firm, and nonexudative (RFN) pork that should be added to PSE pork and non-meat adjuncts must be determined. Effects of combinations of PSE and RFN pork on protein functionality with beneficial adjuncts incorporated have been explored previously by Motzer Carpenter, Reynolds, and Lyon (1998). Their results revealed that the combination of normal and PSE pork and the addition of binders enhanced water holding capacity and bind of restructured ham slices when compared to that made from only PSE meat. Pork collagen is an inexpensive adjunct that increases cooking yield and tensile strength in restructured beef (Kenney, Castner, & Kropf, 1992). Pork collagen has been refined so that it can be utilized in processed products to improve protein functionality through the immobilization of free water, increasing the stability of the finished structure (Prabhu, Doerscher, Hull, & Schoenberg, 2000). The pork collagen utilized in this study was a high protein powdered product with mild pork flavor, has reversible-gelling characteristics, excellent water-binding properties, and was designed for incorporation into processed meats (Proliant, 2002). Three percent collagen was added to the formulation because it is the maximum inclusion value allowed by the USDA, theoretically determining its peak potential in improving the protein functionality of chunked and formed, boneless cured ham rolls. Levels of PSE were chosen to determine if pork collagen could increase the usefulness of PSE pork, and to determine if pork collagen increases functionality similarly in PSE and RFN pork. This research was designed to determine both the usability of this specific pork collagen in chunked and formed, cured pork and the potential to add value to PSE meat through improved functionality.
2. Materials and methods 2.1. Meat product Fresh porcine semimembranosus and adductor muscles were obtained from a pork processing plant in 3-week intervals during the timeframe of August to December. Muscles were transported in coolers by car (50 km) from the meat plant to the laboratory. Upon arrival, raw material was vacuum packaged, and then stored (4 C) for less than 2 weeks until all treatment combinations within a replication were performed. All samples were taken from National Pork Development
(NPD) pork carcasses produced from market age pigs that weighed 110–125 kg. Both RFN pork and PSE pork were selected based on visual color such that the following treatment combinations were processed: 100% PSE, 50% PSE+50% RFN, and 100% RFN. pH and CIE L*, a*, b* values were measured in triplicate at similar anatomical locations for each semimembranosus/ adductor muscle upon arrival to verify that the raw material selected was either PSE or RFN. RFN samples were identified as having a CIE L* < 50 and PSE samples were identified as having a CIE L* > 54. If the sample did not meet these color requirements, they were not utilized in the experiment. The chroma meter (Model CR-200, Minolta Camera Co., Ltd., Osaka Japan) was calibrated using a standard Minolta calibration plate (white plate, No. 20933026; CIE L* 97.91, a* 0.70, b* +2.44) each time prior to testing. pH was determined by removing three 2-g samples from three similar anatomical locations on each of the muscles and homogenizing (Virtishear Model.225318, The Virtis Company, Inc., Gardener, NY) for 1 min in 20 ml of distilled deionized water. pH was measured for the individual samples to with a calibrated pH meter (Model AR25, Fisher Scientific, Pittsburgh, PA) and a pH electrode (Model 13-620-298, Fisher Scientific, Pittsburgh, PA). Samples were not used as RFN raw material if their pH was below 5.6 and were not used as PSE raw material if their pH was above 5.6 (Kauffman et al., 1992) 2.2. Sample processing Porcine semimembranosus and adductor muscles were cut into 2.5 by 2.5 cm cubes and 0.908 kg of these muscles were incorporated in the formulation of each treatment. Ten percent of the meat was ground (0.6 cm) once with a food processor (Model HC3000, Black & Decker, Shelton, CT) to increase bind. The brine solution was formulated consisting of added water [27.5% Meat Weight Basis (MWB)], sodium chloride (2% MWB), sodium tripolyphosphate (0.5% MWB), dextrose (1% MWB), sodium nitrite (156 ppm), and sodium erythorbate (0.042% MWB). Pork Collagen (PC, P5601 Myogel Plus, Proliant Inc., Ames, IA) were added to the brine in appropriate treatments. Treatment combinations consisted of 0 or 3% pork collagen incorporated through the brine solution into a product formulated with 0, 50 or 100% PSE pork. Each treatment was placed in a vacuum tumbler (Model Inject Star MC 20/40/60/80226, Inject Star of the Americas, Brookfield, CT), and the brine for each treatment was poured onto the meat samples. The samples and brine were then tumbled under vacuum for 1.5 h at 4 C, stopping every 15 min for a period of 10 min to enhance brine absorption. Each ham treatment was stuffed into moisture permeable casings (Model Reg Fib
M.W. Schilling et al. / Meat Science 65 (2003) 547–553
CSG 5*25 Light PS, Viskase, Chicago, IL) manually, and a Tipper Tie (Model PRA65L, Tipper Tie, Apex, NC) was used to seal the casing. The samples were set in a meat lug for approximately 16 h (4 C). The next day, the product was processed in a smokehouse (Model 1000, Alkar, Lodi, Wisconsin) to an internal temperature of 69 C. The smokehouse schedule was 1 h for dry bulb 54 C and no wet bulb, 2 h for dry bulb 66 C and wet bulb 47 C, 1 h for dry bulb 71 C and wet bulb 57 C, and approximately 1 h 15 min for dry bulb 88 C and wet bulb 74 C. The boneless hams were immediately cold showered for 15 min and then stored in plastic lugs at 4 C for 16 h prior to cooking yield determinations. Ham rolls were sliced into 12.7 mm thick slices, packaged aerobically, and stored (4 C) for instrumental analysis that was performed within 48 h. 2.3. Cooking loss Cooking loss was reported as (raw weight-cooked weight/raw weight)100 and was reported as a percentage. The product was cooked in a smokehouse (Model 1000, Alkar, Lodi, Wisconsin) to an internal temperature of 69 C. 2.4. Expressible moisture The Instron Universal Testing machine (Model 1011, Instron Corp., Canton, MA) was used to determine expressible moisture on two randomly selected ham slices from each treatment. Four cores (19 mm diameter) were taken from each 12.7 mm slice. The cores were individually weighed and then placed on top and beneath two 12.5 cm Whatman #1 filter papers to absorb excess moisture. Cores were axially compressed to a height of 3.2 mm (75% compression) and were held for 15 s once the deformation point was reached. After removing the force, the core was reweighed. The Instron was programmed with a 500-kg compression load cell and a crosshead speed of 100 mm/min. Expressible moisture was reported as a percentage: [(initial wt. final wt.)/initial wt.)]100. 2.5. Bind Bind strength was evaluated using a procedure modified from Field, Williams, Prasad, Cross, and Secrist (1984) incorporating the Instron Universal Testing machine (Model 1011, Instron Corp., Canton, MA). Three 12.7-mm slices were randomly selected from each treatment to make determinations. A 25.0 mm diameter steel ball (chrome alloy grade 25) was attached to a rod and then attached to the instron using a chuck. This device was attached to the Instron crosshead. Nails were placed manually through each sample into the 1.6-mm holes drilled on the top of a plexiglass stand used to secure
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ham slices in place during testing. Nail holes were drilled 0.5 mm apart in 1 mm deep holes around a circle with a nail diameter of 4.5 mm and an inside diameter of 4.0 mm. The plexiglass stand was placed on the flat, circular surface of the Instron. The slice was aligned so that the steel ball would penetrate the middle of the meat slice. The steel ball was positioned directly above the meat slice, and bind was reported as the peak force (kg) necessary for the steel ball to burst through a slice of restructured ham roll. The Instron was set at a speed of 100 mm/min. 2.6. Cooked color Two randomly selected ham slices from each treatment were used to evaluate cooked color. Three measurements were taken for each slice, and CIE L*a*b* values were determined using a chroma meter (Model CR-200, Minolta Camera Co., Ltd., Osaka Japan). The chroma meter was calibrated using a standard Minolta calibration plate (white plate, No. 20933026; CIE L* 97.91, a* 0.70, b* +2.44) each time prior to testing. 2.7. Statistical analysis A Randomized Complete Block Design with six replications was utilized to test the treatment effects of raw material and pork collagen (Version 8.2, SAS, 1999 Cary NC). Blocking reduced variation among replications caused by seasonal variation. When significant differences occurred for a response (P < 0.05), Duncan’s Multiple Range Test was performed to separate treatment means.
3. Results and discussion 3.1. Cooking loss Differences (P < 0.05) were observed in cooking loss among treatments. The 0% PSE treatment with collagen had lower (P < 0.05) cooking loss values than the 100% PSE treatments with and without collagen (Fig. 2). The 0% PSE treatment without collagen had a significantly lower (P < 0.05) cooking loss than the 100% PSE treatment with collagen. A trend was evident indicating that the addition of pork collagen tended to decrease cooking loss at a practical level in 0% PSE treatments but not in 50% PSE and 100% PSE treatments. This trend infers that collagen works synergistically with the myofibrillar structure in meat proteins to bind water. These results are similar to those of Sadowska, Sikorski, and Dobosz (1980) who reported that collagen could improve water binding through collagen-myofibrillar interactions. This synergistic relationship would not occur between PSE pork and collagen due to the high occurrence of myofibrillar protein
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denaturation in PSE meat (Offer, 1991). Our results are similar to those of Kenney et al. (1992) and Prabhu et al. (2000). In the former study, it was reported that addition of collagen improves cooking yields in restructured beef. In the latter study, it was demonstrated that utilization of pork collagen improves cooking yield in coarse ground and finely comminuted sausage products and provides cost savings in product formulation. Results from our experiment suggest that pork collagen has the potential to improve cooking yields in boneless cured pork formulated from high quality pork.
The lack of improvements in cooking yield found in low quality pork treatments infers that utilization of pork collagen in product formulation cannot mask the effects of PSE meat on product quality. 3.2. Expressible moisture There were differences (P < 0.05) in expressible moisture among boneless cured pork formulated with and without pork collagen from both PSE and RFN pork (Fig. 1). Treatments formulated with pork collagen had
Fig. 1. Effects of 0 or 3% pork collagen on expressible moisture (%) of boneless cured pork formulated with 0, 50, or 100% PSE raw material. Bar means among treatments with unlike letters are different (P<0.05). Standard error bars are included for each treatment.
Fig. 2. Effects of 0 or 3% pork collagen on cooking loss of boneless cured pork formulated with 0, 50, or 100% PSE raw material. Bar means among treatments with unlike letters are different (P <0.05). Standard error bars are included for each treatment.
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Table 1 Effects of 0 or 3% pork collagen on CIE L*, CIE a*, and protein bind of boneless cured pork formulated with 0, 50, or 100% PSE raw material Treatment
100% PSE, 0% Collagen 100% PSE, 3% Collagen 50% PSE, 0% Collagen 50% PSE, 3% Collagen 0% PSE, 0% Collagen 0% PSE, 3% Collagen S.E.
CIE L*
CIE a*
Protein bind Total energy (kg)
Maximum peak force (kg)
64.42ab 65.93a 65.39ab 63.25b 62.96b 63.40b
15.72a 13.46b 15.14a 15.11a 16.1a 15.79a
12.59b 19.42ab 19.91ab 19.41ab 23.44a 26.61a
0.73b 1.13ab 1.14ab 1.13ab 1.43a 1.45a
0.31
0.22
1.26
0.079
Means within a column with same letter are not different (P >0.05).
consistently lower (P < 0.05) expressible moisture values than treatments without pork collagen. This observation suggests that loosely bound water is entrapped by pork collagen during heat processing, demonstrating its effectiveness as a water binder. These results agree with those of Webster, Ledward, and Lawrie (1982) who reported that collagen is able to increase water holding capacity in processed products. Collagen demonstrates similar abilities to starch in decreasing expressible moisture. Motzer et al. (1998) and Schilling et al. (2001) demonstrated modified food starches’ ability to decrease expressible moisture in boneless cured ham formulated with PSE and RFN pork. These similarities suggest pork collagen’s potential as a substitute for starch in boneless hams. For treatments not formulated with pork collagen, the 100% PSE treatment had a higher expressible moisture value than the 0% PSE treatment. This result suggests that the lower water holding capacity in PSE meat caused by myosin denaturation (Offer, 1991) leads to higher moisture losses. These results imply that adding pork collagen to restructured hams may decrease chill and purge loss due to its ability to decrease expressible moisture.
Addition of collagen may add functional protein to the product which could improve protein–protein binding in PSE pork that is needed due to lack of functionality caused by protein denaturation (Offer, 1991). The lack of bind improvement (P < 0.05) in treatments not including PSE raw material suggests that there is enough functional protein to create desirable protein– protein binding. Thus, addition of 3% collagen would not increase bind since sufficient binding had already occurred. There is also a trend for bind strength to be improved when PSE levels in product formulation were decreased. Motzer et al. (1998) had similar results when incorporating PSE meat into restructured products. This may be due to poor functionality in PSE meat causing it to be insufficient in binding together restructured products. Based on trends observed, collagen may increase the bind strength of products made with 100% PSE pork but not 0 or 50% PSE treatments. These results demonstrate that though collagen shows promise in improving cooking yields and decreasing expressible moisture in 0% PSE treatments, it does not demonstrate potential for improving protein–protein bind. 3.4. Cooked color
3.3. Bind Bind strength (maximum peak force) differences (P > 0.05) were not observed among treatments with 100 or 50% PSE pork incorporated in the product (Table 1). Furthermore, products with 50% PSE were not different (P > 0.05) from those made with 0% PSE. However, differences (P < 0.05) were apparent between the 100% PSE treatment without pork collagen and 0% PSE treatments with and without collagen. A trend was evident for bind strength improvement when collagen was added to the 100% PSE treatment. A similar trend is seen in Kenney et al. (1992) where connective tissue was shown to improve tensile strength in restructured beef due to the properties of collagen. Their study differed from ours in that they used 10% preheated connective tissue obtained from a commercial supplier.
Hams formulated with 100% PSE, and 3% collagen had higher (P < 0.05) CIE L* values than those formulated with 0% PSE with or without collagen and 50% PSE with collagen (Table 1). Increased CIE L* values may be due to the addition of light colored collagen to an already pale product. No statistical (P > 0.05) or practical differences in CIE L* values were observed for other treatments. The lack of practical differences was that the treatments did not appear different in lightness indicating that consumers would not likely be able to visualize any differences. Incorporation of 100% PSE pork and 3% pork collagen decreased (P < 0.05) the CIE a* values of boneless cured pork (Table 1). This difference can be attributable to lower CIE a* values for PSE meat when compared to RFN raw material (Zhu & Brewer, 1998) and lack of
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Fig. 3. Effects of 0 or 3% pork collagen on CIE b* Value of hams made with 0, 50, or 100% PSE. Bar means among treatments with unlike letters are different (P <0.05). Standard errors bars are included for each treatment.
redness in pork collagen. Results also demonstrated that CIE a* values for 0 and 50% PSE treatments with added collagen were not different (P > 0.05) than treatments without collagen. These results differ slightly from research performed by Kenney et al. (1992), who reported that products containing higher levels of collagen tended to be less red when utilized in beef. These differences could be due to either species differences or amount of collagen added to the product. Higher CIE b* values (P < 0.05) were observed in treatments formulated with collagen at the same level of PSE pork addition (Fig. 3). Increased CIE b* values also occurred in 100% PSE treatments when compared to 0 and 50% PSE treatments at the same level of collagen (Fig. 3). Addition of collagen to hams made with 50 or 0% PSE are not different (P > 0.05) than products made with 100% PSE and no collagen. These results suggest that PSE pork does not play as large a role in the product yellowness as the inclusion of collagen. Increases in CIE b* values in treatments can be attributed to utilization of PSE pork as raw material in the formulation which has a naturally higher CIE b* value than RFN raw material (Zhu & Brewer, 1998) and the incorporation of collagen that is light tan in color. Results of cooked color demonstrate that utilization of pork collagen does slightly affect the yellowness and redness of products that would be applicable to industry, but these differences may not be practical and could be potentially eliminated through lower usage values of collagen.
4. Conclusions Pork collagen has the potential to decrease cooking loss in non-PSE and expressible moisture in non-PSE
and PSE restructured boneless cured pork. Protein functionality characteristics in 50% PSE treatments suggested the possibility of utilizing a percentage of PSE meat in a product between 0 and 50%. The appropriate acceptable level would require further investigation, be product dependent, and depend on the severity of the PSE defect in the raw material. Utilization of pork collagen can increase functionality in both PSE and RFN meat, but different usage levels should be explored to determine optimum quality improvements. References Bowker, B. C., Wynveen, E. J., Grant, A. L., & Gerrard, D. E. (2000). Effects of electrical stimulation on early postmortem pH and temperature declines in pigs from different genetic lines and halothane genotypes. Meat Science, 53(2), 125–133. Briskey, E. J., & Wismer-Pederson, J. (1961). Biochemistry of pork muscle structure. Rate of anaerobic glycolysis and temperature change versus the apparent structure of muscle tissue. Journal of Food Science, 26(3), 297–305. Camou, J. P., & Sebranek, J. G. (1991). Gelation characteristics of muscle proteins from pale, soft, exudative (PSE) pork. Meat Science, 30(3), 207–220. Charpentier, J. (1969). Effect of temperature and pH on physicochemical properties of sarcoplasmic proteins of pork muscle: practical consequences. Ann. Biol. Anim. Biochem. Biophys., 9(2), 101– 110. Field, R. A., Williams, J. C., Prasad, V. S., Cross, H. R., & Secrist, J. L. (1984). An objective measurement for evaluation of bind in restructured lamb roasts. Journal of Texture Studies, 15, 173–178. Goutefongea, R. (1971). Influence of pH and temperature on solubility of muscle protein in pigs. Ann. Biol. Anim. Biochem. Biophys., 11(2), 233–244. Kauffman, R. G., Cassens, R. G., Scherer, A., & Meeker, D. L. (1961). Variations in pork quality: history, definition, extent, and resolution. Des Moines, IA: National Pork Producers Council. Kenney, P. B., Kastner, C. L., & Kropf, D. H. (1992). Raw and preheated epimysium and gelatin affect properties of low-salt, low-fat, restructured beef. Journal of Food Science, 57(3), 551–554.
M.W. Schilling et al. / Meat Science 65 (2003) 547–553 Lee, Y. B., & Choi, Y. I. (1998). PSE pork: The causes and solutions. Asian-Australian Journal of Animal Science, 12(2), 244–252. Motzer, E. A., Carpenter, J. A., Reynolds, A. E., & Lyon, C. E. (1998). Quality of restructured hams manufactured with PSE pork as affected by water binders. Journal of Food Science, 63(6), 1007– 1011. Offer, G. (1991). Modeling of the formation of pale, soft, and exudative meat: effects of chilling regime and rate and extent of glycolysis. Meat Sci., 30(2), 157–184. Pearson, A. M., & Gillett, T. A. (1996). Raw Materials. Chapter 6 in Processed meats (3rd ed.). New York, NY: Chapman and Hall. Prabhu, G., Doerscher, D., Hull, D., & Schoenberg, E. (2000). Pork collagen–product characteristics and applications in meat products. IFT Proc. Abstract, 64, 2. Proliant Inc. (2002). www.proliantinc/ingredients.comSpecially-dried functional meat proteins made from pork and beef. Proliant Inc. Ames, IA.
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Sadowska, M., Sikorski, A. E., & Dobosz, M. (1980). Influence of collagen on the rheological properties of meat homogenates. Lebensm.- Wiss. U.- Technol, 13(5), 232–236. SAS Institute Inc.. (1999). Version 8.2. Cary, NC: SAS Institute Inc. Schilling, M.W, Marriott, N.G., Acton J.C. (2001) Effects of modified food starch on the functional properties of restructured boneless pork produced from PSE and RFN pork. In Proceedings 47th international congress of meat science and technology (pp. 156–157), 28 August–2 September 2001, Warsaw, Poland. Webster, J. D., Ledward, D. A., & Lawrie, R. A. (1982). Protein hydrosylates from meat industry by-products. Meat Sci., 7(2), 147–157. Young, D. (1996). A retailers response on the quality of pork. In Proceedings of 49th reciprocal meats conference (pp. 50–52), 9–12 June 1996, Provo, Utah. Zhu, L. G., & Brewer, M. S. (1998). Discoloration of fresh pork as related to muscle and display conditions. Journal of Food Science, 63(5), 763–767.
Utilization of pork collagen for functionality improvement of boneless cured ham manufactured from pale, soft, and exudative pork M.W. Schillinga,*, L.E. Minkb, P.S. Gochenourc, N.G. Marriotta, C.Z. Alvaradoa a
Department of Food Science and Technology, Virginia Polytechnic Institute and State University, Blacksburg, VA 24061-0418, USA b Department of Animal Science, University of Nebraska, Lincoln, NE 68588, USA c Department of Poultry Science, Auburn University, Auburn, AL 36849, USA Received 13 May 2002; received in revised form 3 September 2002; accepted 3 September 2002
Abstract This study was designed to determine the effect of raw material and the inclusion of pork collagen on the protein functionality of boneless cured pork manufactured from 100% pale, soft, and exudative (PSE), 50% PSE, and 0% PSE with either 3 or 0% collagen. A Randomized Complete Block Design with six replications was utilized as the experimental design. Inclusion of collagen decreased (P< 0.05) expressible moisture and increased (P< 0.05) CIE b* value. Differences (P <0.05) revealed that collagen inclusion caused the 0% PSE treatments to have a lower cooking loss for 100% PSE treatments with and without collagen and a higher protein–protein bind value for 100% PSE treatments without collagen. Utilization of pork collagen in boneless cured pork that incorporates PSE meat increases water holding capacity and has the potential to improve protein functionality characteristics of the product. # 2003 Elsevier Science Ltd. All rights reserved. Keywords: PSE; Pork collagen; Ham; Functionality
1. Introduction Consumer desire for leaner meats has necessitated the production of pork with less fat. The intensive selection for leaner pigs in combination with stressful preslaughter and slaughter conditions has resulted in lower quality pork (Lee & Choi, 1998). This selection process has been responsible for the identification of genetic material that yields porcine muscle with a low pH, lighter color, and very soft and watery tissue. Genetic selection and pre-slaughter stress cause rapid postmortem glycolysis, which results in increased lactic acid production and decreased pH. Decreased pH combined with high muscle temperature (Camou & Sebranek, 1990) causes protein denaturation that exceeds that observed in normal muscle (Briskey & Wismer-Pedersen, 1961; Charpentier, 1969; Goutefongea, 1971; * Corresponding author. Tel.: +1-540-231-8679; fax: +1-540-2319293. E-mail address: [email protected] (M.W. Schilling).
Bowker, Wynveen, Grant, & Gerrard, 2000) leading to the production of pale, soft, and exudative (PSE) pork. Because of this protein denaturation, there is an increase in water loss that is detrimental to product quality (Offer, 1991). Young (1996) stated that customers will not buy a gray, wet product, and that appearance of pork is the most important attribute to the consumer. Since consumers will not accept fatter pork (Kauffman, Cassens, Scherer, & Meeker, 1992), this industry is challenged with the task of reducing the incidence of paleness without reducing leanness. A possible approach is to investigate the possibility of PSE pork utilization in the production of chunked and formed products. To increase the viability of this technique, color, waterholding capacity, bind, texture, and sensory attributes need to be improved from the raw material to the finished product. Two variables need to be examined to determine the optimal utilization of PSE pork in restructured products. First, the addition of non-meat adjuncts that can
0309-1740/03/$ - see front matter # 2003 Elsevier Science Ltd. All rights reserved. doi:10.1016/S0309-1740(02)00247-4
548
M.W. Schilling et al. / Meat Science 65 (2003) 547–553
improve the functional characteristics of PSE pork should be explored (Schilling, Marriott, and Acton, 2001). Secondly, it will not be possible to manufacture an acceptable product from 100% PSE pork (Pearson and Gillett, 1996). To formulate an acceptable restructured product, the concentration of red, firm, and nonexudative (RFN) pork that should be added to PSE pork and non-meat adjuncts must be determined. Effects of combinations of PSE and RFN pork on protein functionality with beneficial adjuncts incorporated have been explored previously by Motzer Carpenter, Reynolds, and Lyon (1998). Their results revealed that the combination of normal and PSE pork and the addition of binders enhanced water holding capacity and bind of restructured ham slices when compared to that made from only PSE meat. Pork collagen is an inexpensive adjunct that increases cooking yield and tensile strength in restructured beef (Kenney, Castner, & Kropf, 1992). Pork collagen has been refined so that it can be utilized in processed products to improve protein functionality through the immobilization of free water, increasing the stability of the finished structure (Prabhu, Doerscher, Hull, & Schoenberg, 2000). The pork collagen utilized in this study was a high protein powdered product with mild pork flavor, has reversible-gelling characteristics, excellent water-binding properties, and was designed for incorporation into processed meats (Proliant, 2002). Three percent collagen was added to the formulation because it is the maximum inclusion value allowed by the USDA, theoretically determining its peak potential in improving the protein functionality of chunked and formed, boneless cured ham rolls. Levels of PSE were chosen to determine if pork collagen could increase the usefulness of PSE pork, and to determine if pork collagen increases functionality similarly in PSE and RFN pork. This research was designed to determine both the usability of this specific pork collagen in chunked and formed, cured pork and the potential to add value to PSE meat through improved functionality.
2. Materials and methods 2.1. Meat product Fresh porcine semimembranosus and adductor muscles were obtained from a pork processing plant in 3-week intervals during the timeframe of August to December. Muscles were transported in coolers by car (50 km) from the meat plant to the laboratory. Upon arrival, raw material was vacuum packaged, and then stored (4 C) for less than 2 weeks until all treatment combinations within a replication were performed. All samples were taken from National Pork Development
(NPD) pork carcasses produced from market age pigs that weighed 110–125 kg. Both RFN pork and PSE pork were selected based on visual color such that the following treatment combinations were processed: 100% PSE, 50% PSE+50% RFN, and 100% RFN. pH and CIE L*, a*, b* values were measured in triplicate at similar anatomical locations for each semimembranosus/ adductor muscle upon arrival to verify that the raw material selected was either PSE or RFN. RFN samples were identified as having a CIE L* < 50 and PSE samples were identified as having a CIE L* > 54. If the sample did not meet these color requirements, they were not utilized in the experiment. The chroma meter (Model CR-200, Minolta Camera Co., Ltd., Osaka Japan) was calibrated using a standard Minolta calibration plate (white plate, No. 20933026; CIE L* 97.91, a* 0.70, b* +2.44) each time prior to testing. pH was determined by removing three 2-g samples from three similar anatomical locations on each of the muscles and homogenizing (Virtishear Model.225318, The Virtis Company, Inc., Gardener, NY) for 1 min in 20 ml of distilled deionized water. pH was measured for the individual samples to with a calibrated pH meter (Model AR25, Fisher Scientific, Pittsburgh, PA) and a pH electrode (Model 13-620-298, Fisher Scientific, Pittsburgh, PA). Samples were not used as RFN raw material if their pH was below 5.6 and were not used as PSE raw material if their pH was above 5.6 (Kauffman et al., 1992) 2.2. Sample processing Porcine semimembranosus and adductor muscles were cut into 2.5 by 2.5 cm cubes and 0.908 kg of these muscles were incorporated in the formulation of each treatment. Ten percent of the meat was ground (0.6 cm) once with a food processor (Model HC3000, Black & Decker, Shelton, CT) to increase bind. The brine solution was formulated consisting of added water [27.5% Meat Weight Basis (MWB)], sodium chloride (2% MWB), sodium tripolyphosphate (0.5% MWB), dextrose (1% MWB), sodium nitrite (156 ppm), and sodium erythorbate (0.042% MWB). Pork Collagen (PC, P5601 Myogel Plus, Proliant Inc., Ames, IA) were added to the brine in appropriate treatments. Treatment combinations consisted of 0 or 3% pork collagen incorporated through the brine solution into a product formulated with 0, 50 or 100% PSE pork. Each treatment was placed in a vacuum tumbler (Model Inject Star MC 20/40/60/80226, Inject Star of the Americas, Brookfield, CT), and the brine for each treatment was poured onto the meat samples. The samples and brine were then tumbled under vacuum for 1.5 h at 4 C, stopping every 15 min for a period of 10 min to enhance brine absorption. Each ham treatment was stuffed into moisture permeable casings (Model Reg Fib
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CSG 5*25 Light PS, Viskase, Chicago, IL) manually, and a Tipper Tie (Model PRA65L, Tipper Tie, Apex, NC) was used to seal the casing. The samples were set in a meat lug for approximately 16 h (4 C). The next day, the product was processed in a smokehouse (Model 1000, Alkar, Lodi, Wisconsin) to an internal temperature of 69 C. The smokehouse schedule was 1 h for dry bulb 54 C and no wet bulb, 2 h for dry bulb 66 C and wet bulb 47 C, 1 h for dry bulb 71 C and wet bulb 57 C, and approximately 1 h 15 min for dry bulb 88 C and wet bulb 74 C. The boneless hams were immediately cold showered for 15 min and then stored in plastic lugs at 4 C for 16 h prior to cooking yield determinations. Ham rolls were sliced into 12.7 mm thick slices, packaged aerobically, and stored (4 C) for instrumental analysis that was performed within 48 h. 2.3. Cooking loss Cooking loss was reported as (raw weight-cooked weight/raw weight)100 and was reported as a percentage. The product was cooked in a smokehouse (Model 1000, Alkar, Lodi, Wisconsin) to an internal temperature of 69 C. 2.4. Expressible moisture The Instron Universal Testing machine (Model 1011, Instron Corp., Canton, MA) was used to determine expressible moisture on two randomly selected ham slices from each treatment. Four cores (19 mm diameter) were taken from each 12.7 mm slice. The cores were individually weighed and then placed on top and beneath two 12.5 cm Whatman #1 filter papers to absorb excess moisture. Cores were axially compressed to a height of 3.2 mm (75% compression) and were held for 15 s once the deformation point was reached. After removing the force, the core was reweighed. The Instron was programmed with a 500-kg compression load cell and a crosshead speed of 100 mm/min. Expressible moisture was reported as a percentage: [(initial wt. final wt.)/initial wt.)]100. 2.5. Bind Bind strength was evaluated using a procedure modified from Field, Williams, Prasad, Cross, and Secrist (1984) incorporating the Instron Universal Testing machine (Model 1011, Instron Corp., Canton, MA). Three 12.7-mm slices were randomly selected from each treatment to make determinations. A 25.0 mm diameter steel ball (chrome alloy grade 25) was attached to a rod and then attached to the instron using a chuck. This device was attached to the Instron crosshead. Nails were placed manually through each sample into the 1.6-mm holes drilled on the top of a plexiglass stand used to secure
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ham slices in place during testing. Nail holes were drilled 0.5 mm apart in 1 mm deep holes around a circle with a nail diameter of 4.5 mm and an inside diameter of 4.0 mm. The plexiglass stand was placed on the flat, circular surface of the Instron. The slice was aligned so that the steel ball would penetrate the middle of the meat slice. The steel ball was positioned directly above the meat slice, and bind was reported as the peak force (kg) necessary for the steel ball to burst through a slice of restructured ham roll. The Instron was set at a speed of 100 mm/min. 2.6. Cooked color Two randomly selected ham slices from each treatment were used to evaluate cooked color. Three measurements were taken for each slice, and CIE L*a*b* values were determined using a chroma meter (Model CR-200, Minolta Camera Co., Ltd., Osaka Japan). The chroma meter was calibrated using a standard Minolta calibration plate (white plate, No. 20933026; CIE L* 97.91, a* 0.70, b* +2.44) each time prior to testing. 2.7. Statistical analysis A Randomized Complete Block Design with six replications was utilized to test the treatment effects of raw material and pork collagen (Version 8.2, SAS, 1999 Cary NC). Blocking reduced variation among replications caused by seasonal variation. When significant differences occurred for a response (P < 0.05), Duncan’s Multiple Range Test was performed to separate treatment means.
3. Results and discussion 3.1. Cooking loss Differences (P < 0.05) were observed in cooking loss among treatments. The 0% PSE treatment with collagen had lower (P < 0.05) cooking loss values than the 100% PSE treatments with and without collagen (Fig. 2). The 0% PSE treatment without collagen had a significantly lower (P < 0.05) cooking loss than the 100% PSE treatment with collagen. A trend was evident indicating that the addition of pork collagen tended to decrease cooking loss at a practical level in 0% PSE treatments but not in 50% PSE and 100% PSE treatments. This trend infers that collagen works synergistically with the myofibrillar structure in meat proteins to bind water. These results are similar to those of Sadowska, Sikorski, and Dobosz (1980) who reported that collagen could improve water binding through collagen-myofibrillar interactions. This synergistic relationship would not occur between PSE pork and collagen due to the high occurrence of myofibrillar protein
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denaturation in PSE meat (Offer, 1991). Our results are similar to those of Kenney et al. (1992) and Prabhu et al. (2000). In the former study, it was reported that addition of collagen improves cooking yields in restructured beef. In the latter study, it was demonstrated that utilization of pork collagen improves cooking yield in coarse ground and finely comminuted sausage products and provides cost savings in product formulation. Results from our experiment suggest that pork collagen has the potential to improve cooking yields in boneless cured pork formulated from high quality pork.
The lack of improvements in cooking yield found in low quality pork treatments infers that utilization of pork collagen in product formulation cannot mask the effects of PSE meat on product quality. 3.2. Expressible moisture There were differences (P < 0.05) in expressible moisture among boneless cured pork formulated with and without pork collagen from both PSE and RFN pork (Fig. 1). Treatments formulated with pork collagen had
Fig. 1. Effects of 0 or 3% pork collagen on expressible moisture (%) of boneless cured pork formulated with 0, 50, or 100% PSE raw material. Bar means among treatments with unlike letters are different (P<0.05). Standard error bars are included for each treatment.
Fig. 2. Effects of 0 or 3% pork collagen on cooking loss of boneless cured pork formulated with 0, 50, or 100% PSE raw material. Bar means among treatments with unlike letters are different (P <0.05). Standard error bars are included for each treatment.
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Table 1 Effects of 0 or 3% pork collagen on CIE L*, CIE a*, and protein bind of boneless cured pork formulated with 0, 50, or 100% PSE raw material Treatment
100% PSE, 0% Collagen 100% PSE, 3% Collagen 50% PSE, 0% Collagen 50% PSE, 3% Collagen 0% PSE, 0% Collagen 0% PSE, 3% Collagen S.E.
CIE L*
CIE a*
Protein bind Total energy (kg)
Maximum peak force (kg)
64.42ab 65.93a 65.39ab 63.25b 62.96b 63.40b
15.72a 13.46b 15.14a 15.11a 16.1a 15.79a
12.59b 19.42ab 19.91ab 19.41ab 23.44a 26.61a
0.73b 1.13ab 1.14ab 1.13ab 1.43a 1.45a
0.31
0.22
1.26
0.079
Means within a column with same letter are not different (P >0.05).
consistently lower (P < 0.05) expressible moisture values than treatments without pork collagen. This observation suggests that loosely bound water is entrapped by pork collagen during heat processing, demonstrating its effectiveness as a water binder. These results agree with those of Webster, Ledward, and Lawrie (1982) who reported that collagen is able to increase water holding capacity in processed products. Collagen demonstrates similar abilities to starch in decreasing expressible moisture. Motzer et al. (1998) and Schilling et al. (2001) demonstrated modified food starches’ ability to decrease expressible moisture in boneless cured ham formulated with PSE and RFN pork. These similarities suggest pork collagen’s potential as a substitute for starch in boneless hams. For treatments not formulated with pork collagen, the 100% PSE treatment had a higher expressible moisture value than the 0% PSE treatment. This result suggests that the lower water holding capacity in PSE meat caused by myosin denaturation (Offer, 1991) leads to higher moisture losses. These results imply that adding pork collagen to restructured hams may decrease chill and purge loss due to its ability to decrease expressible moisture.
Addition of collagen may add functional protein to the product which could improve protein–protein binding in PSE pork that is needed due to lack of functionality caused by protein denaturation (Offer, 1991). The lack of bind improvement (P < 0.05) in treatments not including PSE raw material suggests that there is enough functional protein to create desirable protein– protein binding. Thus, addition of 3% collagen would not increase bind since sufficient binding had already occurred. There is also a trend for bind strength to be improved when PSE levels in product formulation were decreased. Motzer et al. (1998) had similar results when incorporating PSE meat into restructured products. This may be due to poor functionality in PSE meat causing it to be insufficient in binding together restructured products. Based on trends observed, collagen may increase the bind strength of products made with 100% PSE pork but not 0 or 50% PSE treatments. These results demonstrate that though collagen shows promise in improving cooking yields and decreasing expressible moisture in 0% PSE treatments, it does not demonstrate potential for improving protein–protein bind. 3.4. Cooked color
3.3. Bind Bind strength (maximum peak force) differences (P > 0.05) were not observed among treatments with 100 or 50% PSE pork incorporated in the product (Table 1). Furthermore, products with 50% PSE were not different (P > 0.05) from those made with 0% PSE. However, differences (P < 0.05) were apparent between the 100% PSE treatment without pork collagen and 0% PSE treatments with and without collagen. A trend was evident for bind strength improvement when collagen was added to the 100% PSE treatment. A similar trend is seen in Kenney et al. (1992) where connective tissue was shown to improve tensile strength in restructured beef due to the properties of collagen. Their study differed from ours in that they used 10% preheated connective tissue obtained from a commercial supplier.
Hams formulated with 100% PSE, and 3% collagen had higher (P < 0.05) CIE L* values than those formulated with 0% PSE with or without collagen and 50% PSE with collagen (Table 1). Increased CIE L* values may be due to the addition of light colored collagen to an already pale product. No statistical (P > 0.05) or practical differences in CIE L* values were observed for other treatments. The lack of practical differences was that the treatments did not appear different in lightness indicating that consumers would not likely be able to visualize any differences. Incorporation of 100% PSE pork and 3% pork collagen decreased (P < 0.05) the CIE a* values of boneless cured pork (Table 1). This difference can be attributable to lower CIE a* values for PSE meat when compared to RFN raw material (Zhu & Brewer, 1998) and lack of
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Fig. 3. Effects of 0 or 3% pork collagen on CIE b* Value of hams made with 0, 50, or 100% PSE. Bar means among treatments with unlike letters are different (P <0.05). Standard errors bars are included for each treatment.
redness in pork collagen. Results also demonstrated that CIE a* values for 0 and 50% PSE treatments with added collagen were not different (P > 0.05) than treatments without collagen. These results differ slightly from research performed by Kenney et al. (1992), who reported that products containing higher levels of collagen tended to be less red when utilized in beef. These differences could be due to either species differences or amount of collagen added to the product. Higher CIE b* values (P < 0.05) were observed in treatments formulated with collagen at the same level of PSE pork addition (Fig. 3). Increased CIE b* values also occurred in 100% PSE treatments when compared to 0 and 50% PSE treatments at the same level of collagen (Fig. 3). Addition of collagen to hams made with 50 or 0% PSE are not different (P > 0.05) than products made with 100% PSE and no collagen. These results suggest that PSE pork does not play as large a role in the product yellowness as the inclusion of collagen. Increases in CIE b* values in treatments can be attributed to utilization of PSE pork as raw material in the formulation which has a naturally higher CIE b* value than RFN raw material (Zhu & Brewer, 1998) and the incorporation of collagen that is light tan in color. Results of cooked color demonstrate that utilization of pork collagen does slightly affect the yellowness and redness of products that would be applicable to industry, but these differences may not be practical and could be potentially eliminated through lower usage values of collagen.
4. Conclusions Pork collagen has the potential to decrease cooking loss in non-PSE and expressible moisture in non-PSE
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