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Effect of Surface Treatment in the Preservation of Frozen Poultry*
Research Notes EFFECT OF SURFACE TREATMENT IN THE PRESERVATION OF FROZEN POULTRY* C. J. ECHTERLING Poultry Department, Purdue University, Lafayette, Indiana (Received for publication August 20, 1949)
* Journal Paper No. 414 of Purdue Agricultural Experiment Station.
state it must be well protected with a moisture-vapor-proof wrapper or coating. Tressler (1935) states that desiccation of frozen poultry is particularly difficult to prevent, because of the difficulty encountered in wrapping a bird in such a way as to obtain a close contact with a wrapper highly impervious to moisture vapor. He suggested that freezerburn might be prevented by improving packaging, by coating the poultry with a substance impervious to moisture-vapor, (such as mineral oil or vegetable oil), or by coating with a hygroscopic substance which would hold moisture, such as sugar solutions, gum solutions, or salt brine. An aqueous solution of polyvinyl alcohol (Elvanol), a thermoplastic resin, was tested in this study. Its properties are governed by the degree of polymerization and hydrolysis. Films prepared from the aqueous solution by evaporation of water are colorless, odorless, tasteless, transparent, exceedingly tough, unaffected by all oils, greases, fats, hydrocarbons, and most of the organic solvents, e.g., alcohols, esters, ethers, halogenated hydrocarbons. Several preliminary trials were made on the mechanics of applying Elvanol solution to the surface of dressed, eviscerated poultry. In these trials, concentration of the Elvanol solution, carcass temperature at the time of dipping and during the drying period, and conditions for dipping of the birds and drying of the solution were tested to determine their effects on the handling and drying qualities of the solu-
929
Downloaded from http://ps.oxfordjournals.org/ at UNIVERSITY OF PITTSBURGH on June 20, 2015
Although many adverse conditions in the storage of dressed poultry have been corrected or eliminated, conditions for complete arrest of surface drying (freezerburn) has not been attained. The extent to which freezerburn develops during frozen storage will depend upon rate of dehydration; temperature, humidity, and rate of movement of the atmosphere surrounding the product. Edmunds (1939) reports that regardless of the method used to freeze, eviscerated poultry, the principal factor involved in' preserving quality is that of extremely low temperatures (—15° to — 50 degrees F.). Cook (1939) relates that information gained from the drying of other materials, (meats, fish, etc.) shows that the rate of drying decreases with the temperature at constant relative humidity, and decreases as the humidity increases at constant temperature. His work confirms these facts for the storage of frozen poultry. Apart from the control of such conditions as temperature and humidity, Cook reports that freezerburn can be prevented by proper packaging. Since ice crystals in the product have a vapor pressure equivalent to 100% relative humidity, little or no evaporation from poultry can occur if the package is moisture proof. Tressler and Evers (1946) report that since poultry is especially susceptible to desiccation during storage in the frozen
930
RESEARCH NOTES
coatings was evidenced by the changes in appearance and thickness of the coating throughout the storage period; and by the fact that there was a greater loss of weight, in all cases, in the treated birds than in the untreated or controls. In all cases, more dehydration occurred in the untreated birds than those treated with the polyvinyl alcohol solution. After 60 days of storage, more dehydration had occurred in the broilers than in the fryers; however, by the time the birds were in storage for 180 days, there was little difference in the dehydration occurring in the two classes of dressed poultry. It was noted at the end of 60 days of storage that there was very little change, if any in the condition of the polyvinyl alcohol coating. After 60 days of storage, EXPERIMENTAL it was noted that as the storage period inTreated and untreated birds of the same creased the coatings prepared from both breeding and rearing were stored in a grades of Elvanol became drier, less durcommercial locker plant ( — 2°+ 5° F.) for able, and less elastic. After 180 days of 60, 120, and 180 day periods. Two trials storage, a considerable number of the were conducted for each of the storage coatings were flaky and very uneven in periods—one with broilers, and one with thickness. dryers. Several of the birds from each of the storage trials were cooked under similar Two grades of Elvanol (50-42 and 50conditions, and subjected to a taste panel. 90) were used to prepare the polyvinyl alcohol solutions used in preparing the In no case was any taste or odor detected treated birds. Each solution used con- that could be attributed to the polyvinyl tained 1\ percent Elvanol (one grade per alcohol coating. The author is indebted solution), 40 percent ethyl alcohol (190 to Miss Ruth Jordan of the Home Economics Staff for the performance of these proof), and 5 2 | percent. All of the birds in this study were held tests. REFERENCES in storage in ordinary lockers in a commercial locker plant. At the end of the pre- Cook, W. H. 1939. Precooling, freezing, and storage of dressed poultry. Proceedings, Seventh World's scribed storage periods the birds were Poultry Congress 1939; 512-516. removed from storage, weighed, and exEdmunds, C. E. 1939. Federal inspection of dressed amined and scored for freezerburn. poultry for condition and wholesomeness. ProResults showed little or no differences in ceedings, Seventh World's Poultry Congress, 1939; 403-406. weight losses in the treated birds. No comparative or statistical analysis could be Tressler, D. K. 1935. Freezer burn on refrigerated poultry. U. S. Egg and Poultry Magazine, made on the weight losses because the loss 1935. Vol. 41, No. 9; 33-52; No. 10; 38-41. in weight, due to change in weight of the Tressler, D. K. and C. F. Evers. 1946. The freezing coating during storage, was not measured. preservation of Foods. AVI Publishing Company, That there was a loss of weight in the Inc., N. Y., 1946: 231.
Downloaded from http://ps.oxfordjournals.org/ at UNIVERSITY OF PITTSBURGH on June 20, 2015
tion and the thickness of film deposited. The results of these trials indicated the following: 1. The temperature of the carcass at the time the coating is applied should be the same as the temperature at which the bird is to be held in storage. 2. The dipping operation can be performed at room temperature (70°+ 2° F.) but the bird must be placed immediately back into the storage. 3. Approximately 40 percent (by weight) of the total Elvanol solution should be ethyl alcohol or a similar antifreeze (acceptable under Pure Food and Drug regulations) to lower the freezing point of the solution below storage temperature to allow the coating to dry.
* Journal Paper No. 414 of Purdue Agricultural Experiment Station.
state it must be well protected with a moisture-vapor-proof wrapper or coating. Tressler (1935) states that desiccation of frozen poultry is particularly difficult to prevent, because of the difficulty encountered in wrapping a bird in such a way as to obtain a close contact with a wrapper highly impervious to moisture vapor. He suggested that freezerburn might be prevented by improving packaging, by coating the poultry with a substance impervious to moisture-vapor, (such as mineral oil or vegetable oil), or by coating with a hygroscopic substance which would hold moisture, such as sugar solutions, gum solutions, or salt brine. An aqueous solution of polyvinyl alcohol (Elvanol), a thermoplastic resin, was tested in this study. Its properties are governed by the degree of polymerization and hydrolysis. Films prepared from the aqueous solution by evaporation of water are colorless, odorless, tasteless, transparent, exceedingly tough, unaffected by all oils, greases, fats, hydrocarbons, and most of the organic solvents, e.g., alcohols, esters, ethers, halogenated hydrocarbons. Several preliminary trials were made on the mechanics of applying Elvanol solution to the surface of dressed, eviscerated poultry. In these trials, concentration of the Elvanol solution, carcass temperature at the time of dipping and during the drying period, and conditions for dipping of the birds and drying of the solution were tested to determine their effects on the handling and drying qualities of the solu-
929
Downloaded from http://ps.oxfordjournals.org/ at UNIVERSITY OF PITTSBURGH on June 20, 2015
Although many adverse conditions in the storage of dressed poultry have been corrected or eliminated, conditions for complete arrest of surface drying (freezerburn) has not been attained. The extent to which freezerburn develops during frozen storage will depend upon rate of dehydration; temperature, humidity, and rate of movement of the atmosphere surrounding the product. Edmunds (1939) reports that regardless of the method used to freeze, eviscerated poultry, the principal factor involved in' preserving quality is that of extremely low temperatures (—15° to — 50 degrees F.). Cook (1939) relates that information gained from the drying of other materials, (meats, fish, etc.) shows that the rate of drying decreases with the temperature at constant relative humidity, and decreases as the humidity increases at constant temperature. His work confirms these facts for the storage of frozen poultry. Apart from the control of such conditions as temperature and humidity, Cook reports that freezerburn can be prevented by proper packaging. Since ice crystals in the product have a vapor pressure equivalent to 100% relative humidity, little or no evaporation from poultry can occur if the package is moisture proof. Tressler and Evers (1946) report that since poultry is especially susceptible to desiccation during storage in the frozen
930
RESEARCH NOTES
coatings was evidenced by the changes in appearance and thickness of the coating throughout the storage period; and by the fact that there was a greater loss of weight, in all cases, in the treated birds than in the untreated or controls. In all cases, more dehydration occurred in the untreated birds than those treated with the polyvinyl alcohol solution. After 60 days of storage, more dehydration had occurred in the broilers than in the fryers; however, by the time the birds were in storage for 180 days, there was little difference in the dehydration occurring in the two classes of dressed poultry. It was noted at the end of 60 days of storage that there was very little change, if any in the condition of the polyvinyl alcohol coating. After 60 days of storage, EXPERIMENTAL it was noted that as the storage period inTreated and untreated birds of the same creased the coatings prepared from both breeding and rearing were stored in a grades of Elvanol became drier, less durcommercial locker plant ( — 2°+ 5° F.) for able, and less elastic. After 180 days of 60, 120, and 180 day periods. Two trials storage, a considerable number of the were conducted for each of the storage coatings were flaky and very uneven in periods—one with broilers, and one with thickness. dryers. Several of the birds from each of the storage trials were cooked under similar Two grades of Elvanol (50-42 and 50conditions, and subjected to a taste panel. 90) were used to prepare the polyvinyl alcohol solutions used in preparing the In no case was any taste or odor detected treated birds. Each solution used con- that could be attributed to the polyvinyl tained 1\ percent Elvanol (one grade per alcohol coating. The author is indebted solution), 40 percent ethyl alcohol (190 to Miss Ruth Jordan of the Home Economics Staff for the performance of these proof), and 5 2 | percent. All of the birds in this study were held tests. REFERENCES in storage in ordinary lockers in a commercial locker plant. At the end of the pre- Cook, W. H. 1939. Precooling, freezing, and storage of dressed poultry. Proceedings, Seventh World's scribed storage periods the birds were Poultry Congress 1939; 512-516. removed from storage, weighed, and exEdmunds, C. E. 1939. Federal inspection of dressed amined and scored for freezerburn. poultry for condition and wholesomeness. ProResults showed little or no differences in ceedings, Seventh World's Poultry Congress, 1939; 403-406. weight losses in the treated birds. No comparative or statistical analysis could be Tressler, D. K. 1935. Freezer burn on refrigerated poultry. U. S. Egg and Poultry Magazine, made on the weight losses because the loss 1935. Vol. 41, No. 9; 33-52; No. 10; 38-41. in weight, due to change in weight of the Tressler, D. K. and C. F. Evers. 1946. The freezing coating during storage, was not measured. preservation of Foods. AVI Publishing Company, That there was a loss of weight in the Inc., N. Y., 1946: 231.
Downloaded from http://ps.oxfordjournals.org/ at UNIVERSITY OF PITTSBURGH on June 20, 2015
tion and the thickness of film deposited. The results of these trials indicated the following: 1. The temperature of the carcass at the time the coating is applied should be the same as the temperature at which the bird is to be held in storage. 2. The dipping operation can be performed at room temperature (70°+ 2° F.) but the bird must be placed immediately back into the storage. 3. Approximately 40 percent (by weight) of the total Elvanol solution should be ethyl alcohol or a similar antifreeze (acceptable under Pure Food and Drug regulations) to lower the freezing point of the solution below storage temperature to allow the coating to dry.