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Effects of Fat Source and Final Comminution Temperature on Fat Particle Dispersion, Emulsion Stability, and Textural Characteristics of Turkey Frankfurters1
Effects of Fat Source and Final Comminution Temperature on Fat Particle Dispersion, Emulsion Stability, and Textural Characteristics of Turkey Fnuikfurters1 B. BATER and A. J. MAUSER Department of Poultry Science, University of Wisconsin, Madison, Wisconsin 53706 (Received for publication August 6, 1990)
1991 Poultry Science 70:1424-1429 INTRODUCTION
Frankfurters are processed meats that generally are categorized as meat emulsions or batters. The meat batters are formed by chopping meats, along with salt and other ingredients, to form a coarse dispersion of mainly water, fat, and protein. Thermal processing converts the highly viscous sol into a viscoelastic solid that can be viewed as a protein gel filled with fat particles. Comminution time is one of the critical factors for meat emulsion stability. Research by Hansen (1960)reportedthat chopping time must be sufficient to form a protein matrix enclosing the dispersed fat; myosin and actomyosin appeared to supply these stabilizing membranes around the fat globules. However, excessive chopping time can also cause emulsion instability. According to Wilson (1960), myosin is salt-extracted from meat during chopping to form an interface between liquid protein and fat phases of an emulsion. With continued chopping, semisolid fat is cut into increasingly smaller fat globules, creating a larger total fat surface for the protein to cover. If insufficient myosin is available, fat globules
'Research supported by the College of Agricultural and Life Sciences, University of Wisconsin, Madison, WI 53706.
not fully surrounded will coalesce, causing emulsion breakdown. As comminution time increases, meat emulsion temperature will increase and the frictional heat will cause fat phase transition (Acton et al, 1983). Townsend et al. (1968) and Swift et al. (1968) indicated that the melting characteristics of meat fat could be the basis for differences in the maximum temperatures at which meat formulas should be emulsified. Townsend et al. (1971) reported that beef fat needs a higher final chopping temperature (18 Q than pork fat and cottonseed oil (12 Q to avoid underchopping. Ackerman et al. (1971) reported that pork fat was dispersed more finely than beef fat and cottonseed oil was dispersed more finely than pork fat in frankfurters under the same preparation conditions. Because poultry fat has a lower melting point (31 to 33 Q than pork fat (38 to 47 Q and beef fat (41 to 48 Q (Acton et al., 1983), slightly different handling is required for poultry fat when making meat products. Research by Hargus et al. (1970) reported that turkey meat emulsions were stable at 12.8 C for white meat and unstable for dark meat when chopped in a room temperature environment. Baker et al. (1969) found mat beef fat produced significantly firmer frankfurters than those produced by chicken fat when unheated.
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ABSTRACT Turkey frankfurter pulsions containing turkey t h i ^ fat were choppedtofinalcomminution temperatures of 13,18, or 23 C and heat processed. Data were obtained on fat particle distribution, fat separation, emulsion stability, shear press value, and proximate analysis to determine an optimumfinalcomminution temperature for turkey frankfurters. At the samefinalcomminution temperature, particle size for turkey fat was smallest, pork fat was intermediate, and beef fat was largest The optimum emulsion stability for different types of fat was dependent on final comminution temperature. For turkey fat and pork fat, the optimumfinalcomminution temperature among those compared was 13 C, and the optimum final comminution temperature for beef fat was 18 C. No significantly different shear press values were obtained among the frankfurters. (Key words: emulsion, fat, turkey frankfurter, stability, texture)
FAT SOURCE AND CHOPPING TEMPERATURE
There is no published research comparing the qualities of turkey frankfurters made with turkey fat and red meat fat and prepared at various final comminution temperatures. The purpose of the present research was to investigate the effects of fat source and final comminution temperature on fat particle dispersion, emulsion stability, and textural characteristics of turkey frankfurters. MATERIALS AND METHODS
Hand-deboned turkey thigh meat, abdominal turkey fat, pork back fat, and beef back fat were obtained several different times from local processors and stored in a -30 C freezer until used. When ready for evaluation, appropriate quantities of the meat and fat tissues were removed from the freezer and thawed in a 4 C cooler for 48 h. The meat was trimmed of excessive fat and epimysia tissues and ground once through a 6.35-mm orifice diameter plate.2 The fat tissues were ground once through a 9.52-mm orifice diameter plate. The ground meat and fat tissues were stored in a 4 C cooler until used. Raw meat was analyzed for moisture and fat contents (Association of Official Analytical Chemists, 1980). Protein was calculated by difference (assumed 1% for ash). Results showed that the turkey meat contained 73.3% moisture and 5.8% fat. The turkey, pork, and beef tissue fat had moisture and fat contents of 12.1 and 86.2%, 5.6 and 91.9%, and 2.9 and 94.1%, respectively. Based on these results, formulas were calculated to produce frankfurters containing approximately 18% fat. The weight of the thigh meat and fat tissue in each comminuted batch was 1,500 g. For every 100 g of lean mean and fat, 20 g of ice, 2 g of salt, .05 g of sodium erythorbate, and .015 g of sodium nitrite were added. Processing The emulsions were prepared in a Model 84142 Hobart Food Cutter^ fitted with two knives that were operated at 1,725 rpm with a
%obart, Troy, OH 45374. 3 Model SP 12, Rockvffle, MD 20852.
bowl speed of 20 rpm. A thermometer was used to obtain the emulsion temperature. All ingredients except tissue fats were placed in the cutter, and the mixture was chopped for 4 min. Tissue fats were then added, and the meat emulsions were chopped until they reached the treatment temperatures being compared. Samples weighing approximately 500 g each were removed when the emulsions attained 13, 18, or 23 C. Elapsed time was recorded. The emulsion samples were wrapped with aluminum foil and temporarily stored in a 4 C cooler. After small portions were removed for emulsion stability measurements, the emulsions were stuffed into 23-mm diameter cellulose casings and linked about 14 cm long. The frankfurters were cooked in a smokehouse according to the schedule: 54 C for 30 min, 63 C for 30 min, 71 C for 30 min, and 77 C for 15 min. They were then cooked in water (at 76 C) to an internal temperature of 68 C, cold showered, and stored overnight in a 4 C cooler. After a visual examination of fat separation, the frankfurters were peeled from the casings and vacuum packed in plastic bags; those samples intended for proximate analysis and texture were stored at 4 C, and those for histological examination were stored at -30 C. Evaluation Emulsion stability was determined by the Rongey method (Rongey, 1965). Emulsion samples (25 g) were placed into Wierbicki tubes (Rongey, 1965), cooked in 71 C water for 30 min, and then centrifuged at 1,000 rpm for 5 min. Percentages of separated fat and gel water based on emulsion sample weight were recorded. Two frankfurters from each treatment were ground twice through a 4.8-mm plate. The ground samples were analyzed for moisture, fat, and protein (Association of Official Analytical Chemists, 1980). An evaluation of fat separation was conducted subjectively. The presence of "fat caps" (coalesced fat at either end of the frankfurters) was determined by examining five frankfurters from each treatment Three notations, "0","+", and "++" were used to record no fat, slight fat, and heavy fat separation, respectively. An Allo-Kramer shear press3 with a standard shear cell was used to obtain shear press values of frankfurters. The 2.3-cm diameter peeled frankfurters were cut to 6.5 cm in length,
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Materials and Formulas
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BATER AND MAUKER TABLE 1. Average chopping time, emulsion stability, fat separation, and shear press values of turkey frankfurters
9.1 14.4 23.6 9.4 14.1 23.9 9.3 14.8 24.1
Fat2
Fat separation3
0 + 1.1 0 + 1.0 + 0 +
0 + ++ 0 + + ++ 0 +
-(%)
14.0° 15.0b 20.0" 162" 12.8b 152"
(kg/g) 1.9" 22" 2.1" 2.1" 22" 2.3" 2.0" 2.1" 2.3"
"""Means within the same fat sources for percentage water loss and same column for shear press values with no common superscripts are significantly different (P<05). 'Average chopping time (n = 7) to attain the respective final chopping temperatures. 2 Fat separation between 0 and 1% was scored as "+". 3 "0", "+", and "++" indicate no fat, slight fat, and heavy fat separation (fat caps), respectively.
weighed to the nearest .1 g, inserted perpendicular to the slots of the cell, and sheared at a speed scale of 9 (6 mm/s) at room temperature. Three frankfurters from each treatment were tested and results were expressed as kilograms of force per gram of frankfurter. Histological investigations were carried out to correlate fat particle distribution and emulsion stability of the frankfurters using a method similar to that of Ackerman et al. (1971). Samples (.5-cm cubes) of frankfurters were frozen in isopentane, cooled with liquid nitrogen, and sectioned into 10-um slices with a cryomicrotome. The oil red O staining method (Humason, 1979) was used to permit visualization of fat particles and the protein matrix. Sections were examined microscopically as scon as possible after histochemical processing as fading may occur. A linearly scaled eyepiece micrometer disk was used in measuring particle size, and a squared grid was used for counting numbers. Particles having diameters of 100 |i or larger, between 100 and 50 \i, and 50 |A or less were counted at 40, 100, and 160x magnifications, respectively. Average numbers were obtained from five replications and the results are reported as particles per square millimeter. Photomicrographs of serial sections were made in a Zeiss photomicroscope4 at a magnification
"•Model 63160, Carl Zeiss, Germany.
of 35x on 35-mm negatives, and the negatives were developed on 8.9 x 12.7-cm prints. Statistical Analysis The experiment was conducted as a split-plot design. Fat sources were the main plot treatments; final comminution temperatures were treated as subplots within fat sources. The frankfurters of each treatment were independently evaluated as both raw and cooked samples. The data were analyzed by analysis of variance procedures with SAS® (SAS Institute, 1985). Fat sources were tested with the main plot error, final comminution temperatures and final comminution temperatures by fat sources interaction were tested with the residual error. When significant (P<.05) F values for main effects were found, treatment means were separated using Duncan's new multiple range test with P= .05 (Duncan, 1955). RESULTS AND DISCUSSION
As expected, the finished products contained about 62% moisture, 18% fat, and 16% protein. There were no significant differences in moisture, fat, and protein contents of the frankfurters made with different fat sources. The results (Table 1) of times required to obtain the final comminution temperatures indicate that temperature rise was similar in chopping emulsions containing any of the
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(Q 13 18 23 13 18 23 13 18 23
(min)
Turkey Turkey Turkey Pork Pork Pork Beef Beef Beef
Emulsion stotality H20
273
Average chopping time1
III
Fat source
Final chopping temperature
FAT SOURCE AND CHOPPING TEMPERATURE
At a final chopping temperature of 13 C (Figure 1 g), the beef fat particles were bigger and more irregular, indicating that the chopping failed to produce adequate dispersion. Chopping to 18 C (Figure 1 h) produced a relatively fine, uniform dispersion of beef fat particles in frankfurters from which fat did not separate (Table 1). The poorer dispersion obtained on extended chopping to 23 C (Figure 1 i) illustrates the effects of overchopping, which can produce coalesced fat during lengthy chopping to a relatively high temperature (Ackerman et al., 1971). Table 2 shows the results of fat particle numbers having diameters larger than 100 u., between 100 to SO, and smaller than 50 (i in 1 mm2. The data indicate that in frankfurters from which fat separated during processing, larger numbers of particles with diameters greater than 100 u. were observed. Optimum fat particle size for emulsion stability appeared to be less than 50 u, assuming enough protein is present to form a complete matrix. The results in Table 2 and also the photomicrographs in Figure 1 showed that at the same final comminution temperature, turkey fat particles were smallest, pork fat particles were intermediate, and beef fat particles were largest. As would be expected, the decrease in number of large fat particles coincides with the increase in number of small fat particles shown in Table 2. Townsend et al. (1968) reported that melting characteristics of meat fats can affect the stability of sausage emulsions, and the instability of emulsions comminuted to more than 18.5 C coincided with melting of high portions of fats. Due to different chemical compositions, turkey fat, pork fat, and beef fat show different melting characteristics and other physical properties. Sufficient chopping time and temperature are needed for adequate dispersion of fat in meat emulsions. However, overchopping can cause instability. Small fat droplets fuse together and increase fat separation of the products during cooking (Hermansson, 1986). Results of the present experiment indicate that fat particle size and dispersion were consistently related to meat emulsion stability. A fine, uniform dispersion resulted in a stable emulsion, and irregular dispersion resulted in an unstable emulsion. At the same final comminution temperatures, turkey fat particles were smallest, pork fat was intermediate, and beef fat was largest. Optimum emulsion
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three kinds of tissue fats. Emulsion stability test results indicated that optimum final comminution temperature (among those compared) for emulsions prepared with turkey fat and pork fat was 13 C, and optimum temperature for emulsions prepared with beef fat was 18 C. The stability results agreed with the fat separation examination results. Frankfurters prepared with turkey fat at final comminution temperatures of 18 and 23 C showed fat caps, indicating overchopping. For frankfurters prepared with beef fat at a final comminution temperature of 13 C, visible fat particles indicated underchopping; at 23 C, fat caps indicated overchopping. The results agreed with those reported by Townsend et al. (1971) that beef fat needs a higher final chopping temperature (18 C) than pork fat (12 C). Results of textural analysis (Table 1) show that frankfurters had no significantly different shear press values among the various treatments. The results indicated that neither the fat source nor the final comminution temperatures affected shear resistance values of the frankfurters. The different results between this experiment and that of Baker et al. (1969), who reported that beef fat produced firmer frankfurters than those produced by chicken fat, might be due to a different fat content in the frankfurters. In the present experiment, shear press values were compared with frankfurters containing 18% fat instead of 25% fat. No significant relationships existed between emulsion stability and frankfurter shear press values. Figure 1 shows the microstructure of frankfurters prepared with turkey fat, pork fat, and beef fat at final comminution temperatures of 13, 18, and 23 C. In the photomicrographs, fat particles stained orange-red are dispersed in a bluish-stained protein matrix. A uniform dispersion of turkey fat particles in the protein matrix was observed at the final chopping temperature of 13 C (Figure 1 a). As chopping temperature increased, at final chopping temperatures of 18 C (Figure 1 b) and 23 C (Figure 1 c), the fat particles became larger and irregular, indicating the effects of overchopping, which apparently broke down the emulsion by producing coalesced fat. Ackerman et al. (1971) made a similar observation. The dispersion of pork fat particles (Figure 1 d, e, and f) was similar to the dispersion of turkey fat particles; as chopping temperature increased, the fat particles became larger and irregular as they coalesced.
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BATER AND MAURER
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FIGURE 1. Photomicrographs of turkey frankfurters containing turkey fat comminuted at 13 C (a), 18 C (b), and 23 C (c); pork fat comminuted at 13 C (d), 18 C (e), and 23 C (f); and beef fat comminuted at 13 C (g), 18 C (h), and 23 C (i).
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FAT SOURCE AND CHOPPING TEMPERATURE TABLE 2. Effects of fat source and final comminution temperatures on size and average number of fat particles in 1-mm2 sections of turkey frankfurters1
Fat source Turkey Turkey Turkey Pork Pork Pork
>100 nm
50 to 100 um
<50 urn
(Q 13 18 23 13 18 23 13 18 23
0 02 27 ± 0 15 22 62 8 6 1 10 ± 2 2
10 ± 75 ± 20 ± 3± 50 ± 22 ± 5 ± 7± 51 ±
1,525 425 225 624 125 150 10 220 49
Number of fat particles per square millimeter
2 ll2 22 .7 ll2 32 .62 1 32
± ± ± ± ± ± ± ± ±
45 48 2 13 2 15 14 2 14 2 22 24 12 2
'Each value is the x ± SE for seven replicates. Fat separation occurred in cooking these frankfurters.
2
stability of different types of fats was dependent on final comminution temperatures. For turkey fat and pork fat, optimum final comminution temperature was around 13 C, and for beef fat was around 18 C. The shear press values of frankfurters were not affected by the fat source or the final comminution temperatures. REFERENCES Ackerman, S. A., C. E. Swift, R. J. Carroll, and W. E. Townsend, 1971. Effects of types of fat and of rates and temperatures of comminution on dispersion of lipids in frankfurters. J. Food Sci. 36:266-269. Acton, J. C , G. R Ziegler, and D. L. Burge, Jr., 1983. Functionality of muscle constituents in the processing of comminuted meat products. CRC Crit Rev. Food Sci. Nutr. 18:99-121. Association of Official Analytical Chemists, 1980. Official Methods of Analysis. 13th ed. Association of Official Analytical Chemists, Washington, DC. Baker, R. C, J. Darfler, and D. V. Vadehra, 1969. Type and level of fat and amount of protein and their effect on the quality of chicken frankfurters. Food Technol. 23:808-811. Duncan, D. B., 1955. Multiple range and multiple F tests. Biometrics. 11:1-42. Hansen, L. J., 1960. Emulsion formation in finely comminuted sausage. Food Technol. 14:565-569. Hargus, G. L., G. W. Froning, C. A Menus, S.
Neelakantan, and T. E. Hartung, 1970. Effect of processing variables on stability and protein extractability of turkey meat emulsions. J. Food Sci. 35: 688-692. Hermansson, A-M., 1986. Water- and fatholding. Pages 273-314 in: Functional Properties of Food Macromolecules. J. R. Mitchell and D. A. Ledward, ed. Elsevier Applied Science Publishers, New York, NY. Humason, G. L., 1979. Animal Tissue Techniques. 4th ed. W. H. Freeman and Company, San Francisco, CA. Rongey, E. H., 1965. A simple objective test for sausage emulsion quality. Pages 99-106 in: Proc. Meat Industry Research Conference, American Meat Institute Foundation, Chicago, IL. SAS Institute, 1985. SAS® User's Guide: Statistics, Version 5 Edition. SAS Institute, Inc., Cary, NC. Swift, C. E., W. E. Townsend, and L. P. Witnauer, 1968. Comminuted meat emulsions: Relation of the melting characteristics of fats to emulsion stability. Food Technol. 22:775-778. Townsend, W. E., S. A. Ackerman, L. P. Witnauer, W. E. Palm, and C. E. Swift, 1971. Effects of types and levels of fat and rates and temperatures of comminution on the processing and characteristics of frankfurters. J. Food Sci. 36:261-265. Townsend, W. E., L. P. Witnauer, J. A. Riloff, and C. E. Swift, 1968. Comminuted meat emulsions: Differential thermal analysis of fat transitions. Food Technol. 22:319-338. Wilson, G. D., 1960. Meat Emulsions. Pages 351-352 in: The Science of Meat and Meat Products. W. H. Freeman and Company, San Francisco, CA.
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Beef Beef Beef
Final chopping temperature
1991 Poultry Science 70:1424-1429 INTRODUCTION
Frankfurters are processed meats that generally are categorized as meat emulsions or batters. The meat batters are formed by chopping meats, along with salt and other ingredients, to form a coarse dispersion of mainly water, fat, and protein. Thermal processing converts the highly viscous sol into a viscoelastic solid that can be viewed as a protein gel filled with fat particles. Comminution time is one of the critical factors for meat emulsion stability. Research by Hansen (1960)reportedthat chopping time must be sufficient to form a protein matrix enclosing the dispersed fat; myosin and actomyosin appeared to supply these stabilizing membranes around the fat globules. However, excessive chopping time can also cause emulsion instability. According to Wilson (1960), myosin is salt-extracted from meat during chopping to form an interface between liquid protein and fat phases of an emulsion. With continued chopping, semisolid fat is cut into increasingly smaller fat globules, creating a larger total fat surface for the protein to cover. If insufficient myosin is available, fat globules
'Research supported by the College of Agricultural and Life Sciences, University of Wisconsin, Madison, WI 53706.
not fully surrounded will coalesce, causing emulsion breakdown. As comminution time increases, meat emulsion temperature will increase and the frictional heat will cause fat phase transition (Acton et al, 1983). Townsend et al. (1968) and Swift et al. (1968) indicated that the melting characteristics of meat fat could be the basis for differences in the maximum temperatures at which meat formulas should be emulsified. Townsend et al. (1971) reported that beef fat needs a higher final chopping temperature (18 Q than pork fat and cottonseed oil (12 Q to avoid underchopping. Ackerman et al. (1971) reported that pork fat was dispersed more finely than beef fat and cottonseed oil was dispersed more finely than pork fat in frankfurters under the same preparation conditions. Because poultry fat has a lower melting point (31 to 33 Q than pork fat (38 to 47 Q and beef fat (41 to 48 Q (Acton et al., 1983), slightly different handling is required for poultry fat when making meat products. Research by Hargus et al. (1970) reported that turkey meat emulsions were stable at 12.8 C for white meat and unstable for dark meat when chopped in a room temperature environment. Baker et al. (1969) found mat beef fat produced significantly firmer frankfurters than those produced by chicken fat when unheated.
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ABSTRACT Turkey frankfurter pulsions containing turkey t h i ^ fat were choppedtofinalcomminution temperatures of 13,18, or 23 C and heat processed. Data were obtained on fat particle distribution, fat separation, emulsion stability, shear press value, and proximate analysis to determine an optimumfinalcomminution temperature for turkey frankfurters. At the samefinalcomminution temperature, particle size for turkey fat was smallest, pork fat was intermediate, and beef fat was largest The optimum emulsion stability for different types of fat was dependent on final comminution temperature. For turkey fat and pork fat, the optimumfinalcomminution temperature among those compared was 13 C, and the optimum final comminution temperature for beef fat was 18 C. No significantly different shear press values were obtained among the frankfurters. (Key words: emulsion, fat, turkey frankfurter, stability, texture)
FAT SOURCE AND CHOPPING TEMPERATURE
There is no published research comparing the qualities of turkey frankfurters made with turkey fat and red meat fat and prepared at various final comminution temperatures. The purpose of the present research was to investigate the effects of fat source and final comminution temperature on fat particle dispersion, emulsion stability, and textural characteristics of turkey frankfurters. MATERIALS AND METHODS
Hand-deboned turkey thigh meat, abdominal turkey fat, pork back fat, and beef back fat were obtained several different times from local processors and stored in a -30 C freezer until used. When ready for evaluation, appropriate quantities of the meat and fat tissues were removed from the freezer and thawed in a 4 C cooler for 48 h. The meat was trimmed of excessive fat and epimysia tissues and ground once through a 6.35-mm orifice diameter plate.2 The fat tissues were ground once through a 9.52-mm orifice diameter plate. The ground meat and fat tissues were stored in a 4 C cooler until used. Raw meat was analyzed for moisture and fat contents (Association of Official Analytical Chemists, 1980). Protein was calculated by difference (assumed 1% for ash). Results showed that the turkey meat contained 73.3% moisture and 5.8% fat. The turkey, pork, and beef tissue fat had moisture and fat contents of 12.1 and 86.2%, 5.6 and 91.9%, and 2.9 and 94.1%, respectively. Based on these results, formulas were calculated to produce frankfurters containing approximately 18% fat. The weight of the thigh meat and fat tissue in each comminuted batch was 1,500 g. For every 100 g of lean mean and fat, 20 g of ice, 2 g of salt, .05 g of sodium erythorbate, and .015 g of sodium nitrite were added. Processing The emulsions were prepared in a Model 84142 Hobart Food Cutter^ fitted with two knives that were operated at 1,725 rpm with a
%obart, Troy, OH 45374. 3 Model SP 12, Rockvffle, MD 20852.
bowl speed of 20 rpm. A thermometer was used to obtain the emulsion temperature. All ingredients except tissue fats were placed in the cutter, and the mixture was chopped for 4 min. Tissue fats were then added, and the meat emulsions were chopped until they reached the treatment temperatures being compared. Samples weighing approximately 500 g each were removed when the emulsions attained 13, 18, or 23 C. Elapsed time was recorded. The emulsion samples were wrapped with aluminum foil and temporarily stored in a 4 C cooler. After small portions were removed for emulsion stability measurements, the emulsions were stuffed into 23-mm diameter cellulose casings and linked about 14 cm long. The frankfurters were cooked in a smokehouse according to the schedule: 54 C for 30 min, 63 C for 30 min, 71 C for 30 min, and 77 C for 15 min. They were then cooked in water (at 76 C) to an internal temperature of 68 C, cold showered, and stored overnight in a 4 C cooler. After a visual examination of fat separation, the frankfurters were peeled from the casings and vacuum packed in plastic bags; those samples intended for proximate analysis and texture were stored at 4 C, and those for histological examination were stored at -30 C. Evaluation Emulsion stability was determined by the Rongey method (Rongey, 1965). Emulsion samples (25 g) were placed into Wierbicki tubes (Rongey, 1965), cooked in 71 C water for 30 min, and then centrifuged at 1,000 rpm for 5 min. Percentages of separated fat and gel water based on emulsion sample weight were recorded. Two frankfurters from each treatment were ground twice through a 4.8-mm plate. The ground samples were analyzed for moisture, fat, and protein (Association of Official Analytical Chemists, 1980). An evaluation of fat separation was conducted subjectively. The presence of "fat caps" (coalesced fat at either end of the frankfurters) was determined by examining five frankfurters from each treatment Three notations, "0","+", and "++" were used to record no fat, slight fat, and heavy fat separation, respectively. An Allo-Kramer shear press3 with a standard shear cell was used to obtain shear press values of frankfurters. The 2.3-cm diameter peeled frankfurters were cut to 6.5 cm in length,
Downloaded from http://ps.oxfordjournals.org/ at D H Hill Library - Acquis S on April 30, 2015
Materials and Formulas
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BATER AND MAUKER TABLE 1. Average chopping time, emulsion stability, fat separation, and shear press values of turkey frankfurters
9.1 14.4 23.6 9.4 14.1 23.9 9.3 14.8 24.1
Fat2
Fat separation3
0 + 1.1 0 + 1.0 + 0 +
0 + ++ 0 + + ++ 0 +
-(%)
14.0° 15.0b 20.0" 162" 12.8b 152"
(kg/g) 1.9" 22" 2.1" 2.1" 22" 2.3" 2.0" 2.1" 2.3"
"""Means within the same fat sources for percentage water loss and same column for shear press values with no common superscripts are significantly different (P<05). 'Average chopping time (n = 7) to attain the respective final chopping temperatures. 2 Fat separation between 0 and 1% was scored as "+". 3 "0", "+", and "++" indicate no fat, slight fat, and heavy fat separation (fat caps), respectively.
weighed to the nearest .1 g, inserted perpendicular to the slots of the cell, and sheared at a speed scale of 9 (6 mm/s) at room temperature. Three frankfurters from each treatment were tested and results were expressed as kilograms of force per gram of frankfurter. Histological investigations were carried out to correlate fat particle distribution and emulsion stability of the frankfurters using a method similar to that of Ackerman et al. (1971). Samples (.5-cm cubes) of frankfurters were frozen in isopentane, cooled with liquid nitrogen, and sectioned into 10-um slices with a cryomicrotome. The oil red O staining method (Humason, 1979) was used to permit visualization of fat particles and the protein matrix. Sections were examined microscopically as scon as possible after histochemical processing as fading may occur. A linearly scaled eyepiece micrometer disk was used in measuring particle size, and a squared grid was used for counting numbers. Particles having diameters of 100 |i or larger, between 100 and 50 \i, and 50 |A or less were counted at 40, 100, and 160x magnifications, respectively. Average numbers were obtained from five replications and the results are reported as particles per square millimeter. Photomicrographs of serial sections were made in a Zeiss photomicroscope4 at a magnification
"•Model 63160, Carl Zeiss, Germany.
of 35x on 35-mm negatives, and the negatives were developed on 8.9 x 12.7-cm prints. Statistical Analysis The experiment was conducted as a split-plot design. Fat sources were the main plot treatments; final comminution temperatures were treated as subplots within fat sources. The frankfurters of each treatment were independently evaluated as both raw and cooked samples. The data were analyzed by analysis of variance procedures with SAS® (SAS Institute, 1985). Fat sources were tested with the main plot error, final comminution temperatures and final comminution temperatures by fat sources interaction were tested with the residual error. When significant (P<.05) F values for main effects were found, treatment means were separated using Duncan's new multiple range test with P= .05 (Duncan, 1955). RESULTS AND DISCUSSION
As expected, the finished products contained about 62% moisture, 18% fat, and 16% protein. There were no significant differences in moisture, fat, and protein contents of the frankfurters made with different fat sources. The results (Table 1) of times required to obtain the final comminution temperatures indicate that temperature rise was similar in chopping emulsions containing any of the
Downloaded from http://ps.oxfordjournals.org/ at D H Hill Library - Acquis S on April 30, 2015
(Q 13 18 23 13 18 23 13 18 23
(min)
Turkey Turkey Turkey Pork Pork Pork Beef Beef Beef
Emulsion stotality H20
273
Average chopping time1
III
Fat source
Final chopping temperature
FAT SOURCE AND CHOPPING TEMPERATURE
At a final chopping temperature of 13 C (Figure 1 g), the beef fat particles were bigger and more irregular, indicating that the chopping failed to produce adequate dispersion. Chopping to 18 C (Figure 1 h) produced a relatively fine, uniform dispersion of beef fat particles in frankfurters from which fat did not separate (Table 1). The poorer dispersion obtained on extended chopping to 23 C (Figure 1 i) illustrates the effects of overchopping, which can produce coalesced fat during lengthy chopping to a relatively high temperature (Ackerman et al., 1971). Table 2 shows the results of fat particle numbers having diameters larger than 100 u., between 100 to SO, and smaller than 50 (i in 1 mm2. The data indicate that in frankfurters from which fat separated during processing, larger numbers of particles with diameters greater than 100 u. were observed. Optimum fat particle size for emulsion stability appeared to be less than 50 u, assuming enough protein is present to form a complete matrix. The results in Table 2 and also the photomicrographs in Figure 1 showed that at the same final comminution temperature, turkey fat particles were smallest, pork fat particles were intermediate, and beef fat particles were largest. As would be expected, the decrease in number of large fat particles coincides with the increase in number of small fat particles shown in Table 2. Townsend et al. (1968) reported that melting characteristics of meat fats can affect the stability of sausage emulsions, and the instability of emulsions comminuted to more than 18.5 C coincided with melting of high portions of fats. Due to different chemical compositions, turkey fat, pork fat, and beef fat show different melting characteristics and other physical properties. Sufficient chopping time and temperature are needed for adequate dispersion of fat in meat emulsions. However, overchopping can cause instability. Small fat droplets fuse together and increase fat separation of the products during cooking (Hermansson, 1986). Results of the present experiment indicate that fat particle size and dispersion were consistently related to meat emulsion stability. A fine, uniform dispersion resulted in a stable emulsion, and irregular dispersion resulted in an unstable emulsion. At the same final comminution temperatures, turkey fat particles were smallest, pork fat was intermediate, and beef fat was largest. Optimum emulsion
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three kinds of tissue fats. Emulsion stability test results indicated that optimum final comminution temperature (among those compared) for emulsions prepared with turkey fat and pork fat was 13 C, and optimum temperature for emulsions prepared with beef fat was 18 C. The stability results agreed with the fat separation examination results. Frankfurters prepared with turkey fat at final comminution temperatures of 18 and 23 C showed fat caps, indicating overchopping. For frankfurters prepared with beef fat at a final comminution temperature of 13 C, visible fat particles indicated underchopping; at 23 C, fat caps indicated overchopping. The results agreed with those reported by Townsend et al. (1971) that beef fat needs a higher final chopping temperature (18 C) than pork fat (12 C). Results of textural analysis (Table 1) show that frankfurters had no significantly different shear press values among the various treatments. The results indicated that neither the fat source nor the final comminution temperatures affected shear resistance values of the frankfurters. The different results between this experiment and that of Baker et al. (1969), who reported that beef fat produced firmer frankfurters than those produced by chicken fat, might be due to a different fat content in the frankfurters. In the present experiment, shear press values were compared with frankfurters containing 18% fat instead of 25% fat. No significant relationships existed between emulsion stability and frankfurter shear press values. Figure 1 shows the microstructure of frankfurters prepared with turkey fat, pork fat, and beef fat at final comminution temperatures of 13, 18, and 23 C. In the photomicrographs, fat particles stained orange-red are dispersed in a bluish-stained protein matrix. A uniform dispersion of turkey fat particles in the protein matrix was observed at the final chopping temperature of 13 C (Figure 1 a). As chopping temperature increased, at final chopping temperatures of 18 C (Figure 1 b) and 23 C (Figure 1 c), the fat particles became larger and irregular, indicating the effects of overchopping, which apparently broke down the emulsion by producing coalesced fat. Ackerman et al. (1971) made a similar observation. The dispersion of pork fat particles (Figure 1 d, e, and f) was similar to the dispersion of turkey fat particles; as chopping temperature increased, the fat particles became larger and irregular as they coalesced.
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FIGURE 1. Photomicrographs of turkey frankfurters containing turkey fat comminuted at 13 C (a), 18 C (b), and 23 C (c); pork fat comminuted at 13 C (d), 18 C (e), and 23 C (f); and beef fat comminuted at 13 C (g), 18 C (h), and 23 C (i).
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FAT SOURCE AND CHOPPING TEMPERATURE TABLE 2. Effects of fat source and final comminution temperatures on size and average number of fat particles in 1-mm2 sections of turkey frankfurters1
Fat source Turkey Turkey Turkey Pork Pork Pork
>100 nm
50 to 100 um
<50 urn
(Q 13 18 23 13 18 23 13 18 23
0 02 27 ± 0 15 22 62 8 6 1 10 ± 2 2
10 ± 75 ± 20 ± 3± 50 ± 22 ± 5 ± 7± 51 ±
1,525 425 225 624 125 150 10 220 49
Number of fat particles per square millimeter
2 ll2 22 .7 ll2 32 .62 1 32
± ± ± ± ± ± ± ± ±
45 48 2 13 2 15 14 2 14 2 22 24 12 2
'Each value is the x ± SE for seven replicates. Fat separation occurred in cooking these frankfurters.
2
stability of different types of fats was dependent on final comminution temperatures. For turkey fat and pork fat, optimum final comminution temperature was around 13 C, and for beef fat was around 18 C. The shear press values of frankfurters were not affected by the fat source or the final comminution temperatures. REFERENCES Ackerman, S. A., C. E. Swift, R. J. Carroll, and W. E. Townsend, 1971. Effects of types of fat and of rates and temperatures of comminution on dispersion of lipids in frankfurters. J. Food Sci. 36:266-269. Acton, J. C , G. R Ziegler, and D. L. Burge, Jr., 1983. Functionality of muscle constituents in the processing of comminuted meat products. CRC Crit Rev. Food Sci. Nutr. 18:99-121. Association of Official Analytical Chemists, 1980. Official Methods of Analysis. 13th ed. Association of Official Analytical Chemists, Washington, DC. Baker, R. C, J. Darfler, and D. V. Vadehra, 1969. Type and level of fat and amount of protein and their effect on the quality of chicken frankfurters. Food Technol. 23:808-811. Duncan, D. B., 1955. Multiple range and multiple F tests. Biometrics. 11:1-42. Hansen, L. J., 1960. Emulsion formation in finely comminuted sausage. Food Technol. 14:565-569. Hargus, G. L., G. W. Froning, C. A Menus, S.
Neelakantan, and T. E. Hartung, 1970. Effect of processing variables on stability and protein extractability of turkey meat emulsions. J. Food Sci. 35: 688-692. Hermansson, A-M., 1986. Water- and fatholding. Pages 273-314 in: Functional Properties of Food Macromolecules. J. R. Mitchell and D. A. Ledward, ed. Elsevier Applied Science Publishers, New York, NY. Humason, G. L., 1979. Animal Tissue Techniques. 4th ed. W. H. Freeman and Company, San Francisco, CA. Rongey, E. H., 1965. A simple objective test for sausage emulsion quality. Pages 99-106 in: Proc. Meat Industry Research Conference, American Meat Institute Foundation, Chicago, IL. SAS Institute, 1985. SAS® User's Guide: Statistics, Version 5 Edition. SAS Institute, Inc., Cary, NC. Swift, C. E., W. E. Townsend, and L. P. Witnauer, 1968. Comminuted meat emulsions: Relation of the melting characteristics of fats to emulsion stability. Food Technol. 22:775-778. Townsend, W. E., S. A. Ackerman, L. P. Witnauer, W. E. Palm, and C. E. Swift, 1971. Effects of types and levels of fat and rates and temperatures of comminution on the processing and characteristics of frankfurters. J. Food Sci. 36:261-265. Townsend, W. E., L. P. Witnauer, J. A. Riloff, and C. E. Swift, 1968. Comminuted meat emulsions: Differential thermal analysis of fat transitions. Food Technol. 22:319-338. Wilson, G. D., 1960. Meat Emulsions. Pages 351-352 in: The Science of Meat and Meat Products. W. H. Freeman and Company, San Francisco, CA.
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Beef Beef Beef
Final chopping temperature