- Email: [email protected]
Effect of Freezing, Evaporation and Freeze-Drying on Emulsifying Capacity of Salt-Soluble Protein1
Effect of Freezing, Evaporation and Freeze-Drying on Emulsifying Capacity of Salt-Soluble Protein1 M. R. PARKES AND K. N. MAY Departments of Food Science and Poultry Science, University oj Georgia, Athens, Georgia 30601 (Received for publication December 18, 1967)
protein has been reSALT-SOLUBLE ported to be the emulsifying agent in
(1) To determine the effect of various preservation techniques on emulsifying capacity of salt-soluble protein from various tissues of broilers. (2) To determine if protein extracted from commercial bone residue could be preserved and used as a binding agent in emulsion meats. 1 University of Georgia College of Agriculture Experiment Stations, Journal Series Paper Number 209, College Station, Athens, Georgia 30601.
Commercial broiler carcasses and bulk packs of gizzards and hearts were obtained from a local processor at a post-mortem age of not more than eight hours. The carcasses were skinned, deboned and the dark and light tissues separated. Light muscle, dark muscle, gizzards and hearts were ground twice using a grinder plate with holes approximately 3.2 mm. in diameter, packed in polyethylene bags and stored at — 34°C. until used. Combined neck and back tissue and bone residue from these parts, as expelled from a commercial Paoli boning machine, were obtained in frozen 18.1 kg. blocks which were stored at — 34°C. until used. Percentage of total protein in tissue samples was determined by Kjeldahl analysis (A.O.A.C, 1960). Salt-soluble protein was extracted using 3 percent NaCl following methods of Saffle and Galbreath (1964) as modified by Hudspeth and May (1967). Protein content of the salt-soluble extract was determined by Kjeldahl analysis and expressed as a percentage of the total protein. Emulsifying capacity of the salt-soluble extract was determined by use of a model system as described by Carpenter and Saffle (1964), where the extract acts as an emulsifying agent with corn oil being used as the discontinuous phase of the emulsion. Hudspeth and May (1967) successfully used this system on various poultry tissues. Salt-soluble protein extracted from the various tissues was preserved by freeze-
1236
Downloaded from http://ps.oxfordjournals.org/ at Simon Fraser University on May 29, 2015
emulsions made from various poultry tissues by May and Hudspeth (1966), Maurer and Baker (1966) and Hudspeth and May (1967). The same authors reported varying amounts, as well as varying emulsifying capacities, of salt-soluble protein in different tissues of a carcass. Similar reports have been made on red meat products (Carpenter and Saffle, 1964; Saffle and Galbreath, 1964; and Swift et al., 1961). Proteins are generally expensive, yet some potential sources of high quality protein in poultry and red meat processing are considered as by-products and are diverted exclusively to non-food uses such as fertilizer and animal feed ingredients. One such product is the residue from boning machines which is used as a by-product despite its relatively high protein content. The purpose of this research was twofold:
MATERIALS AND METHODS
PRESERVATION OF SOLUBLE PROTEIN
conjunction with freezing, a 1.4 kg. batch of frankfurters was formulated using the formula below, so that the emulsion would break during heating of the frankfurters: 7266 1180 407 9.57 0.7 0.7 40.0
gm. extra lean beef (20.89% protein) gm. pork fat gm. ice gm. seasoning gm. sodium nitrite gm. ascorbic acid gm. NaCl
Salt-soluble protein was extracted from bone residue by making a slurry with three percent NaCl (1.4 w./w.) and adjusting the pH to 6.0 with 0.1N HC1. After 24 hours at 4°C, the mixture was filtered twice through four-ply sections of cheese cloth to remove the insoluble bone and tissue and divided into four groups. Groups one through three were concentrated on the high-vacuum-low-temperature evaporator to 59, 77, and 83 percent of their original weights, respectively. The fourth group was not evaporated. All four groups were then evaluated for binding capacity using the model system, then placed in covered stainless steel beakers and frozen at — 34°C. Four 1.4 kg. batches of frankfurters were then made with the identical ingredients and formulation given above which previously had shown fat separation, except that a 407 gm. section was sawed from the center of each of the four frozen samples and added to the formulation in the place of ice. RESULTS AND DISCUSSION Total protein in fresh tissues was highest in light muscle, intermediate in bone residue, gizzard and dark muscle and lowest in heart and neck and back tissue (Table 1). Salt-soluble protein was highest in light muscle and neck and back tissue and lowest in heart muscle. Total and salt-soluble protein values obtained compare well with values reported for light and dark muscle
Downloaded from http://ps.oxfordjournals.org/ at Simon Fraser University on May 29, 2015
dehydration, evaporation and freezing techniques as outlined below. Freeze-dehydration. Five 100 ml. aliquots of protein extract from each of the six tissues studied were freeze-dried on a Virtis 40-port freeze-drier for 20 to 24 hours at 0.005 mm. Hg until the original weight of the extract was reduced by approximately 95 percent. The flasks containing the dried extract were sealed after weighing and stored at — 34°C. The samples were reconstituted to 100, 85, 70, 55, and 40 percent of their original weight and emulsifying capacity was determined. These figures were then compared to those for the fresh protein extract and the percent of the original emulsifying capacity was calculated as a ratio of the efficiencies of the treated and non-treated samples. Freezing. Three groups of three 50 ml. aliquots of salt-soluble protein extract from commercially deboned neck and back meat were put in 250 ml. glass jars with ground glass tops and placed in —8°C, —15°C. and — 34°C. freezers. The samples were examined at five-day intervals and compared with the fresh extract control samples for retention of emulsifying characteristics. Evaporation. Preliminary tests conducted to determine heat-stability of proteins in the extract demonstrated that emulsifying capacity was not changed by exposure to 37°C. for as long as three hours. With this in mind, the salt-soluble extract from commercially deboned neck and back meat was subjected to evaporation in a Majonnier low-temperature-highvacuum # L T F L evaporator. The temperature of the extract never exceeded 16°C. at 29 inches of vacuum. The process times were five and ten minutes to remove 38 and 62 percent of the original moisture, respectively. The emulsifying capacity was determined on the fresh and on the evaporated samples. For an applied test of evaporation in
1237
1238
M. R. PARKES AND K. N. MAY TABLE 1.—Mean total and salt-soluble protein in various fresh hroiler tissues and their calculated binding constants and binding coefficients
Tissue
Total protein
% Light muscle Dark muscle Gizzard Heart Neck and back Bone residue
24.2 18.9 18.3 15.3 13.2 17.2
1 2
Constant bind value2
Binding coefficients3
42.1 34.4 28.1 25.7 42.7 22.0
16.1 22.3 26.6 29.4 27.5 36.1
6.76 7.67 7.47 7.56 11.74 7.94
1.64 1.45 1.37 1.15 1.17 1.37
Expressed as a percentage of total protein. % salt-soluble proteinXml. oil emulsified/100 mg. soluble protein. Constant bind valueX% total protein.
by Hudspeth and May (1967), while values for other tissues agree well with those of Hudspeth (1968). Oil emulsified by 100 mg. of protein tended to vary inversely with salt-soluble protein content of tissues, being highest for tissues with low-soluble protein content (bone residue) and lowest for tissue with high soluble protein content (light muscle) (Table 1). This has previously been noted by Hudspeth and May (1967) and Maurer and Baker (1967). Constant bind values were calculated using methods outlined by I.B.M. (1966) for red meat products. Values obtained were on the low side of those reported for red meat products which ranged from 7.9 to 16.3 (I.B.M., 1966). However, conditions used in extraction of salt-soluble protein and estimation of fat emulsified by 100 mg. of soluble protein in the present study differed slightly from those used on the red meat products (Saffle, 1967), accounting for at least some of the differences observed. Binding coefficients were calculated by multiplying constant bind value by total protein percentage for each tissue (I.B.M., 1966). Although these values vary with total protein content of a tissue, they do reflect relative usefulness of the various tissues in emulsion meat products. Thus, if percentage of total protein remained about
the same as those reported for each tissue then light muscle would be the most desirable tissue for emulsification followed in order by dark muscle, gizzard or bone residue, and heart or neck and back tissue. Effect of freeze-dehydration and subsequent rehydration of salt-soluble protein on ability of the protein to emulsify fat in the model system is shown in Figure 1. Saltsoluble extracts from dark muscle and from bone residue lost about one percent of their ability to bind fat after drying and rehydration. Extracts from other tissues were actually one to two percent higher in emulsifying ability following 100 percent rehydration. Decreasing the amount of water added back to the dried protein extracts increased fat emulsifying capacity as a percentage of non-dried extracts in a linear fashion. This would be expected since protein concentration increases with decreases in rehydration water. However, concentration of the protein to over twice the original content per ml. of extract increased oil emulsified by only 120 to 140 percent (Figure 1). All tissues except heart changed at about the same rate with decreased water of rehydration. At present the reason for greater emulsification by heart extract is not known. These data would indicate that freeze-dehydration and subsequent rehydration does not signifi-
Downloaded from http://ps.oxfordjournals.org/ at Simon Fraser University on May 29, 2015
3
%
Ml. oil emulsified 100 mg. sol. pro.
Salt soluble protein 1
1239
PRESERVATION OF SOLUBLE PROTEIN
/ 140
/ 135
130
/
125
/ 120
/ 115
/
s
/
//ft /
y
' /v---' /?y/-' /
<'^r
IDS
100
/
'' A /,v / /J.
no
100
/
/
'
y
/
/
— — LIGHT MEAT — • - DARK MEAT - . _ . - 6IZZARD HEART NECKS AND BACKS BONE RESIDUE
/ 85
70 PERCENT
55 REHYDRATION
FIG. 1. Effect of percent of rehydration of freeze-dehydrated salt-soluble protein extracts on amount of oil emulsified per ml., expressed as a percentage of fresh extracts.
TABLE 2. Effect of freezing and storage on the ml of oil emulsified per 100 mg. of salt-soluble protein from chicken neck and back tissue Temperature
Days of storage
storage
0
5
10
15
-8°C. - 1 5 ° C. - 3 4 ° C.
32.0 25.6 25.6
33.7 26.7 26.5
33.3 26.7 26.9
33.1 26.9 26.5
tein extract could be preserved by freezing without loss of emulsifying ability. When salt-soluble protein from neck and back tissue was concentrated by evaporation the amount of oil emulsified per ml. of the concentrated extract increased. Removal of 38 percent of the moisture increased ml. of oil bound per ml. of extract to US percent of the original while removal of 62 percent of the moisture increased the amount to 135 percent of the original. Thus, evaporation could be used to increase the emulsifying capacity of extracted salt-soluble protein with increased capacity being controlled by the amount of moisture removed. When frankfurters were made using the formula given in the procedure using ice the emulsion "broke" or separated during the heating of the frankfurter in the smoke house. When the concentrated, frozen saltsoluble protein from bone residue was added to the mix replacing ice, none of the frankfurter emulsions "broke" during heat processing. These results would indicate that salt-soluble protein from bone residue, which is currently a waste product, might have value as an emulsifying agent if reclaimed by extraction, concentration by evaporation and preservation by freezing. Obviously, methods for economically obtaining the protein would have to be developed and further work would also be needed concerning chemical characteristics and microbiological quality of the protein extract.
Downloaded from http://ps.oxfordjournals.org/ at Simon Fraser University on May 29, 2015
cantly alter emulsification properties of salt-soluble protein extracts from various chicken tissues. It also appears that variation in amounts of water of rehydration could be used to control emulsifying ability of the rehydrated protein extracts over a wide range. Freezing and storage of salt-soluble protein extracted from neck and back tissue at — 8, —IS, or —34°C. did not change the amount of oil emulsified by the protein in the model system (Table 2). The reason for the higher amounts of oil emulsified by extract at the — 8°C. temperature is not known but is probably due to a difference in the composition of meat used for this test since it was a different batch from that used for the other two temperatures. These data, although limited as to length of storage, would indicate that salt-soluble pro-
1240
M. R. PARKES AND K. N. MAY ACKITOWLED GMENTS
Salt-soluble protein was extracted from broiler light muscle, dark muscle, gizzard, heart, neck and back tissue, and bone residue (from a commercial boning machine). Extracts were freeze-dehydrated and subsequently rehydrated at 100, 85, 70, 55 and 40 percent of their original moisture content. Fresh and rehydrated extracts were compared as to their ability to emulsify corn oil in a model system. Extracts of salt-soluble protein from commercial neck and back tissue were frozen and stored at — 8, —15, and —34°C. and tested against fresh extract in the model system. Other extracts of neck and back tissue were concentrated by evaporation and tested in a like manner. Freeze-dehydration and rehydration did not significantly alter the emulsifying ability of the protein extracts. Decreasing water of rehydration (thus increasing protein concentration) increased emulsifying capacity in a linear fashion making it possible to control emulsifying capacity of the extracts. Freezing of extracted protein and storage up to 15 days at temperatures used did not significantly alter emulsifying properties of the extract. Concentration of extracts by evaporation increased emulsifying capacity. Results indicate that salt-soluble protein could be extracted from bone residue and that such protein could be used to prevent emulsion breakdown in frankfurters. Further work is needed to develop economical and sanitary procedures for extraction.
Appreciation is expressed for the technical advice of Dr. R. L. Saffle, Food Science Department, University of Georgia and for samples of meat and bone residue supplied by Jack Prince, Inc., Gainesville, Georgia. REFERENCES Association of Official Agricultural Chemists, 1960. Official Methods of Analysis. 9th Ed. Assoc, of Official Agr. Chemists, Washington, D.C. Carpenter, J. A., and R. L. Saffle, 1964. A simple method of estimating the emulsifying capacity of various meats. J. Food Sci. 29: 774-781. Hudspeth, J. P., 1968. A study of the emulsifying capacity of the salt-soluble proteins of poultry meat. Ph.D. thesis, University of Georgia. Hudspeth, J. P., and K. N. May, 1967. A study of the emulsifying capacity of soluble proteins. 1. Light and dark meat tissues of turkeys, hens and broilers, and dark meat tissues of ducks. FoodTechnol. 2 1 : 1141-1142. International Business Machines, 1966. Linear Programming—Meat Blending. Publication No. E 20-0161-0, International Business Machines Corp., White Plains, N. Y. Maurer, A. J., and R. C. Baker, 1966. The relationship between collagen content and emulsifying capacity of poultry meat. Poultry Sci. 45: 1317-1321. May, K. N., and J. P. Hudspeth, 1966. A study of emulsifying capacity of soluble protein from various poultry meats. 13th World's Poultry Congress Proceedings, Keiv, U.S.S.R., p. 61. Saffle, R. L., 1967. Personal Communication. Saffle, R. L., and J. W. Galbreath, 1964. Quantitative determination of salt-soluble protein in various types of meat. Food Technol. 18(12): 119-120. Swift, C. E., C. Lockett and A. J. Fryar, 1961. Comminuted meat emulsions—the capacity of meats for emulsifying fat. Food Technol. 15(11): 468-473.
NEWS AND NOTES (Continued from page 1208) practice of zinc supplementation in practical rations. More recent studies on the role of zinc and copper in chick embryonic development, specific enzyme systems, and amino acid-mineral interactions are further evidence of the interest and ability
as a recognized nutritionist and biochemist. "With his industrial experience as a nutritionist for the Farm Bureau Feed Mills, Fayetteville, Arkansas, prior to joining the College of Agriculture faculty, Dr. Savage has brought to the atten-
(Continued on page 1244)
Downloaded from http://ps.oxfordjournals.org/ at Simon Fraser University on May 29, 2015
SUMMARY
protein has been reSALT-SOLUBLE ported to be the emulsifying agent in
(1) To determine the effect of various preservation techniques on emulsifying capacity of salt-soluble protein from various tissues of broilers. (2) To determine if protein extracted from commercial bone residue could be preserved and used as a binding agent in emulsion meats. 1 University of Georgia College of Agriculture Experiment Stations, Journal Series Paper Number 209, College Station, Athens, Georgia 30601.
Commercial broiler carcasses and bulk packs of gizzards and hearts were obtained from a local processor at a post-mortem age of not more than eight hours. The carcasses were skinned, deboned and the dark and light tissues separated. Light muscle, dark muscle, gizzards and hearts were ground twice using a grinder plate with holes approximately 3.2 mm. in diameter, packed in polyethylene bags and stored at — 34°C. until used. Combined neck and back tissue and bone residue from these parts, as expelled from a commercial Paoli boning machine, were obtained in frozen 18.1 kg. blocks which were stored at — 34°C. until used. Percentage of total protein in tissue samples was determined by Kjeldahl analysis (A.O.A.C, 1960). Salt-soluble protein was extracted using 3 percent NaCl following methods of Saffle and Galbreath (1964) as modified by Hudspeth and May (1967). Protein content of the salt-soluble extract was determined by Kjeldahl analysis and expressed as a percentage of the total protein. Emulsifying capacity of the salt-soluble extract was determined by use of a model system as described by Carpenter and Saffle (1964), where the extract acts as an emulsifying agent with corn oil being used as the discontinuous phase of the emulsion. Hudspeth and May (1967) successfully used this system on various poultry tissues. Salt-soluble protein extracted from the various tissues was preserved by freeze-
1236
Downloaded from http://ps.oxfordjournals.org/ at Simon Fraser University on May 29, 2015
emulsions made from various poultry tissues by May and Hudspeth (1966), Maurer and Baker (1966) and Hudspeth and May (1967). The same authors reported varying amounts, as well as varying emulsifying capacities, of salt-soluble protein in different tissues of a carcass. Similar reports have been made on red meat products (Carpenter and Saffle, 1964; Saffle and Galbreath, 1964; and Swift et al., 1961). Proteins are generally expensive, yet some potential sources of high quality protein in poultry and red meat processing are considered as by-products and are diverted exclusively to non-food uses such as fertilizer and animal feed ingredients. One such product is the residue from boning machines which is used as a by-product despite its relatively high protein content. The purpose of this research was twofold:
MATERIALS AND METHODS
PRESERVATION OF SOLUBLE PROTEIN
conjunction with freezing, a 1.4 kg. batch of frankfurters was formulated using the formula below, so that the emulsion would break during heating of the frankfurters: 7266 1180 407 9.57 0.7 0.7 40.0
gm. extra lean beef (20.89% protein) gm. pork fat gm. ice gm. seasoning gm. sodium nitrite gm. ascorbic acid gm. NaCl
Salt-soluble protein was extracted from bone residue by making a slurry with three percent NaCl (1.4 w./w.) and adjusting the pH to 6.0 with 0.1N HC1. After 24 hours at 4°C, the mixture was filtered twice through four-ply sections of cheese cloth to remove the insoluble bone and tissue and divided into four groups. Groups one through three were concentrated on the high-vacuum-low-temperature evaporator to 59, 77, and 83 percent of their original weights, respectively. The fourth group was not evaporated. All four groups were then evaluated for binding capacity using the model system, then placed in covered stainless steel beakers and frozen at — 34°C. Four 1.4 kg. batches of frankfurters were then made with the identical ingredients and formulation given above which previously had shown fat separation, except that a 407 gm. section was sawed from the center of each of the four frozen samples and added to the formulation in the place of ice. RESULTS AND DISCUSSION Total protein in fresh tissues was highest in light muscle, intermediate in bone residue, gizzard and dark muscle and lowest in heart and neck and back tissue (Table 1). Salt-soluble protein was highest in light muscle and neck and back tissue and lowest in heart muscle. Total and salt-soluble protein values obtained compare well with values reported for light and dark muscle
Downloaded from http://ps.oxfordjournals.org/ at Simon Fraser University on May 29, 2015
dehydration, evaporation and freezing techniques as outlined below. Freeze-dehydration. Five 100 ml. aliquots of protein extract from each of the six tissues studied were freeze-dried on a Virtis 40-port freeze-drier for 20 to 24 hours at 0.005 mm. Hg until the original weight of the extract was reduced by approximately 95 percent. The flasks containing the dried extract were sealed after weighing and stored at — 34°C. The samples were reconstituted to 100, 85, 70, 55, and 40 percent of their original weight and emulsifying capacity was determined. These figures were then compared to those for the fresh protein extract and the percent of the original emulsifying capacity was calculated as a ratio of the efficiencies of the treated and non-treated samples. Freezing. Three groups of three 50 ml. aliquots of salt-soluble protein extract from commercially deboned neck and back meat were put in 250 ml. glass jars with ground glass tops and placed in —8°C, —15°C. and — 34°C. freezers. The samples were examined at five-day intervals and compared with the fresh extract control samples for retention of emulsifying characteristics. Evaporation. Preliminary tests conducted to determine heat-stability of proteins in the extract demonstrated that emulsifying capacity was not changed by exposure to 37°C. for as long as three hours. With this in mind, the salt-soluble extract from commercially deboned neck and back meat was subjected to evaporation in a Majonnier low-temperature-highvacuum # L T F L evaporator. The temperature of the extract never exceeded 16°C. at 29 inches of vacuum. The process times were five and ten minutes to remove 38 and 62 percent of the original moisture, respectively. The emulsifying capacity was determined on the fresh and on the evaporated samples. For an applied test of evaporation in
1237
1238
M. R. PARKES AND K. N. MAY TABLE 1.—Mean total and salt-soluble protein in various fresh hroiler tissues and their calculated binding constants and binding coefficients
Tissue
Total protein
% Light muscle Dark muscle Gizzard Heart Neck and back Bone residue
24.2 18.9 18.3 15.3 13.2 17.2
1 2
Constant bind value2
Binding coefficients3
42.1 34.4 28.1 25.7 42.7 22.0
16.1 22.3 26.6 29.4 27.5 36.1
6.76 7.67 7.47 7.56 11.74 7.94
1.64 1.45 1.37 1.15 1.17 1.37
Expressed as a percentage of total protein. % salt-soluble proteinXml. oil emulsified/100 mg. soluble protein. Constant bind valueX% total protein.
by Hudspeth and May (1967), while values for other tissues agree well with those of Hudspeth (1968). Oil emulsified by 100 mg. of protein tended to vary inversely with salt-soluble protein content of tissues, being highest for tissues with low-soluble protein content (bone residue) and lowest for tissue with high soluble protein content (light muscle) (Table 1). This has previously been noted by Hudspeth and May (1967) and Maurer and Baker (1967). Constant bind values were calculated using methods outlined by I.B.M. (1966) for red meat products. Values obtained were on the low side of those reported for red meat products which ranged from 7.9 to 16.3 (I.B.M., 1966). However, conditions used in extraction of salt-soluble protein and estimation of fat emulsified by 100 mg. of soluble protein in the present study differed slightly from those used on the red meat products (Saffle, 1967), accounting for at least some of the differences observed. Binding coefficients were calculated by multiplying constant bind value by total protein percentage for each tissue (I.B.M., 1966). Although these values vary with total protein content of a tissue, they do reflect relative usefulness of the various tissues in emulsion meat products. Thus, if percentage of total protein remained about
the same as those reported for each tissue then light muscle would be the most desirable tissue for emulsification followed in order by dark muscle, gizzard or bone residue, and heart or neck and back tissue. Effect of freeze-dehydration and subsequent rehydration of salt-soluble protein on ability of the protein to emulsify fat in the model system is shown in Figure 1. Saltsoluble extracts from dark muscle and from bone residue lost about one percent of their ability to bind fat after drying and rehydration. Extracts from other tissues were actually one to two percent higher in emulsifying ability following 100 percent rehydration. Decreasing the amount of water added back to the dried protein extracts increased fat emulsifying capacity as a percentage of non-dried extracts in a linear fashion. This would be expected since protein concentration increases with decreases in rehydration water. However, concentration of the protein to over twice the original content per ml. of extract increased oil emulsified by only 120 to 140 percent (Figure 1). All tissues except heart changed at about the same rate with decreased water of rehydration. At present the reason for greater emulsification by heart extract is not known. These data would indicate that freeze-dehydration and subsequent rehydration does not signifi-
Downloaded from http://ps.oxfordjournals.org/ at Simon Fraser University on May 29, 2015
3
%
Ml. oil emulsified 100 mg. sol. pro.
Salt soluble protein 1
1239
PRESERVATION OF SOLUBLE PROTEIN
/ 140
/ 135
130
/
125
/ 120
/ 115
/
s
/
//ft /
y
' /v---' /?y/-' /
<'^r
IDS
100
/
'' A /,v / /J.
no
100
/
/
'
y
/
/
— — LIGHT MEAT — • - DARK MEAT - . _ . - 6IZZARD HEART NECKS AND BACKS BONE RESIDUE
/ 85
70 PERCENT
55 REHYDRATION
FIG. 1. Effect of percent of rehydration of freeze-dehydrated salt-soluble protein extracts on amount of oil emulsified per ml., expressed as a percentage of fresh extracts.
TABLE 2. Effect of freezing and storage on the ml of oil emulsified per 100 mg. of salt-soluble protein from chicken neck and back tissue Temperature
Days of storage
storage
0
5
10
15
-8°C. - 1 5 ° C. - 3 4 ° C.
32.0 25.6 25.6
33.7 26.7 26.5
33.3 26.7 26.9
33.1 26.9 26.5
tein extract could be preserved by freezing without loss of emulsifying ability. When salt-soluble protein from neck and back tissue was concentrated by evaporation the amount of oil emulsified per ml. of the concentrated extract increased. Removal of 38 percent of the moisture increased ml. of oil bound per ml. of extract to US percent of the original while removal of 62 percent of the moisture increased the amount to 135 percent of the original. Thus, evaporation could be used to increase the emulsifying capacity of extracted salt-soluble protein with increased capacity being controlled by the amount of moisture removed. When frankfurters were made using the formula given in the procedure using ice the emulsion "broke" or separated during the heating of the frankfurter in the smoke house. When the concentrated, frozen saltsoluble protein from bone residue was added to the mix replacing ice, none of the frankfurter emulsions "broke" during heat processing. These results would indicate that salt-soluble protein from bone residue, which is currently a waste product, might have value as an emulsifying agent if reclaimed by extraction, concentration by evaporation and preservation by freezing. Obviously, methods for economically obtaining the protein would have to be developed and further work would also be needed concerning chemical characteristics and microbiological quality of the protein extract.
Downloaded from http://ps.oxfordjournals.org/ at Simon Fraser University on May 29, 2015
cantly alter emulsification properties of salt-soluble protein extracts from various chicken tissues. It also appears that variation in amounts of water of rehydration could be used to control emulsifying ability of the rehydrated protein extracts over a wide range. Freezing and storage of salt-soluble protein extracted from neck and back tissue at — 8, —IS, or —34°C. did not change the amount of oil emulsified by the protein in the model system (Table 2). The reason for the higher amounts of oil emulsified by extract at the — 8°C. temperature is not known but is probably due to a difference in the composition of meat used for this test since it was a different batch from that used for the other two temperatures. These data, although limited as to length of storage, would indicate that salt-soluble pro-
1240
M. R. PARKES AND K. N. MAY ACKITOWLED GMENTS
Salt-soluble protein was extracted from broiler light muscle, dark muscle, gizzard, heart, neck and back tissue, and bone residue (from a commercial boning machine). Extracts were freeze-dehydrated and subsequently rehydrated at 100, 85, 70, 55 and 40 percent of their original moisture content. Fresh and rehydrated extracts were compared as to their ability to emulsify corn oil in a model system. Extracts of salt-soluble protein from commercial neck and back tissue were frozen and stored at — 8, —15, and —34°C. and tested against fresh extract in the model system. Other extracts of neck and back tissue were concentrated by evaporation and tested in a like manner. Freeze-dehydration and rehydration did not significantly alter the emulsifying ability of the protein extracts. Decreasing water of rehydration (thus increasing protein concentration) increased emulsifying capacity in a linear fashion making it possible to control emulsifying capacity of the extracts. Freezing of extracted protein and storage up to 15 days at temperatures used did not significantly alter emulsifying properties of the extract. Concentration of extracts by evaporation increased emulsifying capacity. Results indicate that salt-soluble protein could be extracted from bone residue and that such protein could be used to prevent emulsion breakdown in frankfurters. Further work is needed to develop economical and sanitary procedures for extraction.
Appreciation is expressed for the technical advice of Dr. R. L. Saffle, Food Science Department, University of Georgia and for samples of meat and bone residue supplied by Jack Prince, Inc., Gainesville, Georgia. REFERENCES Association of Official Agricultural Chemists, 1960. Official Methods of Analysis. 9th Ed. Assoc, of Official Agr. Chemists, Washington, D.C. Carpenter, J. A., and R. L. Saffle, 1964. A simple method of estimating the emulsifying capacity of various meats. J. Food Sci. 29: 774-781. Hudspeth, J. P., 1968. A study of the emulsifying capacity of the salt-soluble proteins of poultry meat. Ph.D. thesis, University of Georgia. Hudspeth, J. P., and K. N. May, 1967. A study of the emulsifying capacity of soluble proteins. 1. Light and dark meat tissues of turkeys, hens and broilers, and dark meat tissues of ducks. FoodTechnol. 2 1 : 1141-1142. International Business Machines, 1966. Linear Programming—Meat Blending. Publication No. E 20-0161-0, International Business Machines Corp., White Plains, N. Y. Maurer, A. J., and R. C. Baker, 1966. The relationship between collagen content and emulsifying capacity of poultry meat. Poultry Sci. 45: 1317-1321. May, K. N., and J. P. Hudspeth, 1966. A study of emulsifying capacity of soluble protein from various poultry meats. 13th World's Poultry Congress Proceedings, Keiv, U.S.S.R., p. 61. Saffle, R. L., 1967. Personal Communication. Saffle, R. L., and J. W. Galbreath, 1964. Quantitative determination of salt-soluble protein in various types of meat. Food Technol. 18(12): 119-120. Swift, C. E., C. Lockett and A. J. Fryar, 1961. Comminuted meat emulsions—the capacity of meats for emulsifying fat. Food Technol. 15(11): 468-473.
NEWS AND NOTES (Continued from page 1208) practice of zinc supplementation in practical rations. More recent studies on the role of zinc and copper in chick embryonic development, specific enzyme systems, and amino acid-mineral interactions are further evidence of the interest and ability
as a recognized nutritionist and biochemist. "With his industrial experience as a nutritionist for the Farm Bureau Feed Mills, Fayetteville, Arkansas, prior to joining the College of Agriculture faculty, Dr. Savage has brought to the atten-
(Continued on page 1244)
Downloaded from http://ps.oxfordjournals.org/ at Simon Fraser University on May 29, 2015
SUMMARY