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Effect of Adding Salt to the Preservative Solution on the Sensory and Physical Properties of Hard-Cooked Eggs
MARKETING AND PRODUCTS Effect of Adding Salt to the Preservative Solution on the Sensory and Physical Properties of Hard-Cooked Eggs J. R. FISCHER and D. L. FLETCHER 1 Department of Poultry Science, University of Georgia, Athens, Georgia 30602 (Received for publication February 1, 1984)
1985 Poultry Science 64:891-895 INTRODUCTION
Salt (NaCl) has been added to flavor and to preserve eggs in many areas of the world. In Thailand, eggs have been flavored and preserved by immersing the egg in a saturated salt solution for different periods of time. Salted eggs, however, are not generally available in the US because they have not been acceptable to American consumers (Trongpanich and Dawson, 1974). According to Trongpanich and Dawson (1974), Thai panelists preferred the flavor of salted eggs more than the American panelists. Pickled eggs have been an acceptable product in the US, and different procedures for pickling eggs have been described by Acton and Johnson (1973), Appi Reddy et al. (1978), Ball and Saffores (1973), Maurer (1975), and Trongpanich and Dawson (1974). Generally, the eggs are placed in a pickling solution (vinegar) of various concentrations with or without added pickling spice, sugar, and other condiments that may have been added to impart specific flavor characteristics to the eggs. The purposes of salting and pickling eggs are to extend shelf life, to impart desirable flavor characteristics, and to preserve the eggs. Arroyo et al. (1973) reported that chicken eggs cured with high concentrations of salt (i.e., >50%) may be kept at room temperature up to 3 months. According to Acton and Johnson (1973), eggs pickled in a 3% acetic acid vinegar
1
solution were shown to be bacteriologically safe. Trongpanich and Dawson (1974) reported that eggs treated in brine after cooking showed slightly higher bacteria counts than untreated eggs with no Salmonella being found on the egg or in the solution. Angalet et al. (1976) reported the major contaminant of the preservative solutions was from the peeled hard-cooked eggs, but within a short time the highly acidic pickling solution destroyed most of the viable microorganisms. In recent years, a new industry has developed around the commercial production of hard-cooked eggs for use in products such as egg salads, on salad bars, and in institutional operations. These eggs are hard-cooked; the shell is removed and the peeled egg is placed in a citric acid based solution to aid in shelf life. A major complaint, often voiced concerning this product, is the lack of a characteristic egg flavor (the eggs are often described as being bland). The objectives of these studies were to examine the applicability of adding various salt levels to the preservative solutions and to evaluate the influence of salt addition on the sensory and physical quality attributes of the eggs.
To whom correspondence should be addressed.
891
MATERIALS AND METHODS
Eggs, 24 to 48 hours old, were hard-cooked for 27 min at 97 C, cooled in an ice water bath for 10 min, and peeled by hand. Only eggs that had a sound, undamaged albumen were used for subsequent analysis.
Downloaded from http://ps.oxfordjournals.org/ at National Institute of Education Library, Serials Unit on June 13, 2015
ABSTRACT Three experiments were conducted to test the effect of added salt (NaCl) on physical, chemical and sensory properties of hard-cooked eggs. Salt was added to a citric acid/sodium benzoate solution at 0, 2.5, 5, 7.5, 10, or 20% (w/v). Sensory and physical analyses were conducted after 40 and 55 days of storage. Results of the sensory evaluations indicated that salt added at 5% resulted in the most desirable product. As salt concentration increased, moisture decreased and shear force increased. No differences were noted for appearance and aroma. Apparently low levels of salt may enhance acceptability of commercially hard-cooked eggs. {Key words: hard-cooked eggs, salt, pickling)
892
FISCHER AND FLETCHER
Experiment 2. Preservative solutions were prepared identical to Experiment 1 except that a ratio of 1:2 (solution.-egg, w/w) was used. Storage and microbial analyses were the same as in Experiment 1 except that eggs were held for a total of 55 days. The pH, moisture, and shear force analyses were performed identical to Experiment 1. In addition, percent yield was determined, because it was noted that in Experiment 1, the eggs appeared to have shrunk in size. The eggs were weighed at Day 0 and again at 30 days. In Experiment 1, the preservative solutions became turbid, which was possibly due to the extraction and precipitation of proteins into the solutions. A total nitrogen (Kjeltec System, Tecator, Inc.) determination was performed on the solutions to determine if the turbidity noted was indeed protein (N X 6.25). Experiment 3. Preservative solutions and eggs were prepared the same as in Experiment 1, except the concentration of salt was 0, 2.5, 5, and 7.5% (w/v), and the solution to egg ratio was 1:2 (w/v). Six eggs were placed in onequart jars and stored at 4 C. At 30 days, the jars were sampled for total plate counts as in Experiment 1. At 40 days, moisture, shear force, yield, and sensory analyses were performed as in Experiment 1. In addition, percent salt in both the egg and solution were determined using Quantab chloride titrators (Ames Co., Ames, IA). At 55 days, moisture and shear force were again evaluated. Data were analyzed using the analysis of variance and Duncan's multiple-range test as described by the Statistical Analysis System (SAS, 1979). RESULTS AND DISCUSSION
The sensory evaluations from Experiment 1 indicate that there were no significant differ-
TABLE 1. Sensory evaluatio n of eggs held for 40 days1 Salt concentration
Appearance
Aroma
Flavor
Texture
Overall acceptance
0 5 10 20
2.00* 2.00* 2.20* 2.00*
2.70* 2.60* 2.80* 2.80*
3.40* 2.00 b 3.20* 4.20*
3.10* 2.90* b 2.70 a b 2.10 b
3.30 a b 2.40 b 3.10* b 4.20*
' Means in each column with different superscripts ' n = 15.
significantly different (P<.05).
Downloaded from http://ps.oxfordjournals.org/ at National Institute of Education Library, Serials Unit on June 13, 2015
The preservative solution, based upon the type commonly used in industry, contained 1.0% citric acid and .2% sodium benzoate in deionized water (w/v). The sodium benzoate was added as a mold and fungal inhibitor. Experiment 1. Salt was added to the previously described preservative solution at 0, 5, 10, or 20% (w/v). The hard-cooked and peeled eggs were placed in 1-gal jars (average of 12 to 15 eggs per jar) and covered with fresh solution at the ratio of 2:1 (solution:egg, w/w) and stored at 4 C for 40 days. At 30 days of storage, each jar was sampled for total plate count. A 10-ml aliquot of solution was subjected to serial dilutions, and pour plates were prepared using Difco total plate count agar. The plates were incubated at 37 C for 48 hr and total colony forming units were counted. After 40 days of storage, the solution acidity (pH) was determined and eggs removed for physical and sensory evaluations. The eggs were sliced horizontally and only the center cuts used. Total moisture was determined by placing egg slices in a vacuum oven at 110 C and at 380 mm Hg. Shear force was determined on an Instron Universal Testing Machine utilizing the Allo-Kramer shear cell. The crosshead speed was 50 mm/min with a 10-kg full scale load. Shear force values were reported as kilograms force per gram of sample. Sensory evaluations were performed by a semi-trained sensory panel consisting of faculty, staff, and students of the University of Georgia. Panelists were instructed to evaluate the eggs for appearance, aroma, flavor, texture, and overall acceptance. Because comparisons of treatment effects of preserved eggs were desired, fresh hard-cooked eggs were not used in the evaluation. The eggs were rated on a five-point hedonic scale with 1 being the most acceptable for flavor, appearance, aroma, overall acceptance, or toughest, and 5 being the least acceptable or least tough.
SALTED AND PRESERVED HARD-COOKED EGGS
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Downloaded from http://ps.oxfordjournals.org/ at National Institute of Education Library, Serials Unit on June 13, 2015
Protein
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ences in the appearance and the aroma of the eggs due to the different salt levels (Table 1). Eggs in a 5% salt solution received significantly more favorable responses for flavor, which would indicate that the panelists preferred the salt flavor at this level. Eggs held at 20% salt had the least desirable flavor but were not significantly different from the 0 and 10% salt treatments. Salt added at the 20% level resulted in significantly increased toughness over the 0% salt treatment, but there were no significant differences among the eggs that were stored at 5 and 10% salt. Overall, the 5% salt eggs were significantly the most acceptable of the treatments and the 20% salt eggs were the least acceptable to the panelists. In Experiments 1 and 2, higher salt (10 and 20%) resulted in a decreased egg moisture content (Table 2). The greater negative response of the egg moisture to the higher salt levels in Experiment 1 is probably due to the greater solution to egg ratio used in Experiment 1 as compared to Experiment 2. The results of the shear force analysis in Experiment 1 indicates as salt level increased, so did shear force (Table 2). The data for Experiment 2, however, does not agree. This difference could be due to the difference of solution to egg ratios, as previously noted, difference in storage time (40 vs. 55 days), moisture content, or an interaction of these factors. No differences in final solution pH were noted for Experiments 1 and 2 at any level within each experiment. The pH values for the first experiment were at least one whole pH unit lower than those from the second experiment. This difference again could be due to the difference in solution to egg ratio. Thus, the total acid in Experiment 1 was greater per unit of egg than in Experiment 2 and therefore less affected by the buffering effect of the eggs within the corresponding solution. As salt increased, the amount of protein in the solution increased as well (Table 2). Thus, the turbidity often noticed in egg preservative solutions may be due to extracted and precipitated proteins and not necessarily the result of bacterial growth (Ball and Saffores, 1973). In Experiment 2, there was approximately an 8 to 11% yield loss in total weight from the eggs between 0 and 30 days of storage in each of the treatments. This loss in weight was probably due to the loss of mositure (osmotic loss from the egg to the higher solute concen-
893
894
FISCHER AND FLETCHER TABLE 3. Sensory evaluations of eggs1
Salt concentration
Appearance
Aroma
Flavor
Texture
Overall acceptance
0 2.5 5 7.5
1.9a 1.8 a 1.9a 2.0 a
2.9 a 2.6 a 2.6 a 2.6 a
3.8 a 3.1ab 2.6b 2.9 b
2.3ab 1.8 b 2.4 a l.oab
3.7 a 3.1ab 2.5 b 2.5 b
tration of the solution) and, to a lesser extent, to the protein loss into the preservative solution. The sensory evaluation from Experiment 3 indicated there were no significant differences in the appearance and aroma of the eggs at the different salt levels (Table 3). The most acceptable flavor scores were from the 5 and 7.5% salt treatments, but the 2.5% treatment was not significantly different. These results paralleled those of the first experiment where the panelists preferred the eggs from 5% level salt treatments. Texture analysis results indicated there was a significant difference between the 2.5% and 5% egg; the 2.5% egg was the toughest and the 5% egg was the most tender. This could be due to the tenderizing effect of the salt on the egg. Overall acceptability placed the 5 and 7.5% eggs as the most acceptable. In Experiment 3, for both the 40- and 55-day analyses, there were no significant differences in percent moisture as the levels of salt increased (Table 4). Apparently at the lower salt (i.e., 2.5 to 7.5%), there is less
pronounced loss of moisture than resulted from Experiments 1 and 2 with the greater spread of salt concentrations (i.e., 5 to 20%). Shear force analysis in Experiment 3 did not result in a significant trend as noted in Experiment 1 (Table 4). Apparently lower salt level differences do not result in the marked toughening effect previously noted. Even though the values are not significantly different, apparently increasing the salt levels up to about 2.5% may actually increase the egg tenderness (salting-in). However, when salt approaches and exceeds 5%, the egg becomes tougher (salting-out). Similar reactions between salt and proteins are recognized in other systems such as meat. This would also explain the slight (but not significant) increase in the 7.5% salt treatment moisture level at 55 days storage. Yield values after 40 days resulted in no significant (P<.05) differences between any of the salt levels (Table 4). The loss in weight ranged from 6 to 7% for all levels. This loss is probably due to the loss in moisture and, in
TABLE 4. Physical and chemical properties of eggs'
Salt cone.
Moisture, days 40 55
0 2.5 5 7.5
72.78 a 72.04 a 71.42 a 71.35 a
Shear force, days 40 55
Yield 1 , 40 days
Salt in eggs, 40 days
93.0 a 93.1 a 94.2 a 94.1 a
.075 1.1 2.1 3.2
(kg/g) 72.92 a 74.29 a 71.15 a 71.83 a
ab
.69 .59 b .69 a b .78 a
.79 a .75 a .82 a .87 a
Salt solution, 40 days
(">) <.01 2.2 3.5 4.9
a,b Means in each individual column with different superscripts are significantly different (P<.05).
Downloaded from http://ps.oxfordjournals.org/ at National Institute of Education Library, Serials Unit on June 13, 2015
a,b Means in each column with different superscripts are significantly different (P<.05). n = 15.
SALTED AND PRESERVED HARD-COOKED EGGS
comments often associated with the lack of flavor of these eggs. ACKNOWLEDGMENTS This study was supported in part by state and Hatch funds allocated to the Georgia Agricultural Experiment Stations. REFERENCES Acton, J. C, and M. G. Johnson, 1973. Pickled eggs. 1. pH, rate of acid penetration into egg components and bacterial analyses. Poultry Sci. 52: 107-111. Angalet, S. A., H. R. Wilson, and J. L. Fry, 1976. Acceptability of pickled quail eggs. J. Food Sci. 41:449-450. Appi Reddy, B., B. Panda, and M. P. Mall, 1978. Effect of different methods of package and storage conditions on keeping quality of pickled quail eggs. Indian Poult. Gaz. 62:154—162. Arroyo, P. T., J. S. Karganiila, and O. T. Diongco, 1973. Egg studies: I. Salt curing of chicken and duck eggs. Philipp. J. Sci. 102:101-113. Ball, H. R., Jr., and M. W. Saffores, 1973. Eggs pickled in various acid strength solutions. Poultry Sci. 52:916-920. Maurer, A. J., 1975. Hard-cooking and pickling eggs as teaching aids. Poultry Sci. 54:1019-1024. SAS Institute. 1979. SAS Users Guide. 9th ed. Raleigh, NC. Trongpanich, K., and L. E. Dawson, 1974. Quality and acceptability of brined pickled duck eggs. Poultry Sci. 53:1129-1133.
Downloaded from http://ps.oxfordjournals.org/ at National Institute of Education Library, Serials Unit on June 13, 2015
some part, the protein that precipitated out of the eggs into solution. Percent salt in the eggs ranged from less than . 1 % in the 0% eggs and up to 3.2% in the 7.5% eggs. This increase in egg salt from the 2.5% to the 7.5% eggs was approximately half of the total salt added to the solutions. From previous experiments (unpublished), it was found a minimum of 21 days is required to allow for total salt penetration into the yolk. These results would indicate that the salt transfers from the solution to the egg, and this transfer is a function of concentration and solution to egg ratio. Bacterial analyses from the three experiments indicated there were less than 10 cfu found in any of the solutions tested. Therefore, it is difficult to assess whether the addition of lower levels of salt would have any bacteriostatic effect. It appears that when low levels (2.5 to 5.0%) of salt are added to the normal citric acid, sodium benzoate-based preservative solution can contribute to the overall acceptance of commercially prepared hard-cooked eggs. The use of salt, and possibly other flavoring agents, may be of benefit in decreasing the negative
895
1985 Poultry Science 64:891-895 INTRODUCTION
Salt (NaCl) has been added to flavor and to preserve eggs in many areas of the world. In Thailand, eggs have been flavored and preserved by immersing the egg in a saturated salt solution for different periods of time. Salted eggs, however, are not generally available in the US because they have not been acceptable to American consumers (Trongpanich and Dawson, 1974). According to Trongpanich and Dawson (1974), Thai panelists preferred the flavor of salted eggs more than the American panelists. Pickled eggs have been an acceptable product in the US, and different procedures for pickling eggs have been described by Acton and Johnson (1973), Appi Reddy et al. (1978), Ball and Saffores (1973), Maurer (1975), and Trongpanich and Dawson (1974). Generally, the eggs are placed in a pickling solution (vinegar) of various concentrations with or without added pickling spice, sugar, and other condiments that may have been added to impart specific flavor characteristics to the eggs. The purposes of salting and pickling eggs are to extend shelf life, to impart desirable flavor characteristics, and to preserve the eggs. Arroyo et al. (1973) reported that chicken eggs cured with high concentrations of salt (i.e., >50%) may be kept at room temperature up to 3 months. According to Acton and Johnson (1973), eggs pickled in a 3% acetic acid vinegar
1
solution were shown to be bacteriologically safe. Trongpanich and Dawson (1974) reported that eggs treated in brine after cooking showed slightly higher bacteria counts than untreated eggs with no Salmonella being found on the egg or in the solution. Angalet et al. (1976) reported the major contaminant of the preservative solutions was from the peeled hard-cooked eggs, but within a short time the highly acidic pickling solution destroyed most of the viable microorganisms. In recent years, a new industry has developed around the commercial production of hard-cooked eggs for use in products such as egg salads, on salad bars, and in institutional operations. These eggs are hard-cooked; the shell is removed and the peeled egg is placed in a citric acid based solution to aid in shelf life. A major complaint, often voiced concerning this product, is the lack of a characteristic egg flavor (the eggs are often described as being bland). The objectives of these studies were to examine the applicability of adding various salt levels to the preservative solutions and to evaluate the influence of salt addition on the sensory and physical quality attributes of the eggs.
To whom correspondence should be addressed.
891
MATERIALS AND METHODS
Eggs, 24 to 48 hours old, were hard-cooked for 27 min at 97 C, cooled in an ice water bath for 10 min, and peeled by hand. Only eggs that had a sound, undamaged albumen were used for subsequent analysis.
Downloaded from http://ps.oxfordjournals.org/ at National Institute of Education Library, Serials Unit on June 13, 2015
ABSTRACT Three experiments were conducted to test the effect of added salt (NaCl) on physical, chemical and sensory properties of hard-cooked eggs. Salt was added to a citric acid/sodium benzoate solution at 0, 2.5, 5, 7.5, 10, or 20% (w/v). Sensory and physical analyses were conducted after 40 and 55 days of storage. Results of the sensory evaluations indicated that salt added at 5% resulted in the most desirable product. As salt concentration increased, moisture decreased and shear force increased. No differences were noted for appearance and aroma. Apparently low levels of salt may enhance acceptability of commercially hard-cooked eggs. {Key words: hard-cooked eggs, salt, pickling)
892
FISCHER AND FLETCHER
Experiment 2. Preservative solutions were prepared identical to Experiment 1 except that a ratio of 1:2 (solution.-egg, w/w) was used. Storage and microbial analyses were the same as in Experiment 1 except that eggs were held for a total of 55 days. The pH, moisture, and shear force analyses were performed identical to Experiment 1. In addition, percent yield was determined, because it was noted that in Experiment 1, the eggs appeared to have shrunk in size. The eggs were weighed at Day 0 and again at 30 days. In Experiment 1, the preservative solutions became turbid, which was possibly due to the extraction and precipitation of proteins into the solutions. A total nitrogen (Kjeltec System, Tecator, Inc.) determination was performed on the solutions to determine if the turbidity noted was indeed protein (N X 6.25). Experiment 3. Preservative solutions and eggs were prepared the same as in Experiment 1, except the concentration of salt was 0, 2.5, 5, and 7.5% (w/v), and the solution to egg ratio was 1:2 (w/v). Six eggs were placed in onequart jars and stored at 4 C. At 30 days, the jars were sampled for total plate counts as in Experiment 1. At 40 days, moisture, shear force, yield, and sensory analyses were performed as in Experiment 1. In addition, percent salt in both the egg and solution were determined using Quantab chloride titrators (Ames Co., Ames, IA). At 55 days, moisture and shear force were again evaluated. Data were analyzed using the analysis of variance and Duncan's multiple-range test as described by the Statistical Analysis System (SAS, 1979). RESULTS AND DISCUSSION
The sensory evaluations from Experiment 1 indicate that there were no significant differ-
TABLE 1. Sensory evaluatio n of eggs held for 40 days1 Salt concentration
Appearance
Aroma
Flavor
Texture
Overall acceptance
0 5 10 20
2.00* 2.00* 2.20* 2.00*
2.70* 2.60* 2.80* 2.80*
3.40* 2.00 b 3.20* 4.20*
3.10* 2.90* b 2.70 a b 2.10 b
3.30 a b 2.40 b 3.10* b 4.20*
' Means in each column with different superscripts ' n = 15.
significantly different (P<.05).
Downloaded from http://ps.oxfordjournals.org/ at National Institute of Education Library, Serials Unit on June 13, 2015
The preservative solution, based upon the type commonly used in industry, contained 1.0% citric acid and .2% sodium benzoate in deionized water (w/v). The sodium benzoate was added as a mold and fungal inhibitor. Experiment 1. Salt was added to the previously described preservative solution at 0, 5, 10, or 20% (w/v). The hard-cooked and peeled eggs were placed in 1-gal jars (average of 12 to 15 eggs per jar) and covered with fresh solution at the ratio of 2:1 (solution:egg, w/w) and stored at 4 C for 40 days. At 30 days of storage, each jar was sampled for total plate count. A 10-ml aliquot of solution was subjected to serial dilutions, and pour plates were prepared using Difco total plate count agar. The plates were incubated at 37 C for 48 hr and total colony forming units were counted. After 40 days of storage, the solution acidity (pH) was determined and eggs removed for physical and sensory evaluations. The eggs were sliced horizontally and only the center cuts used. Total moisture was determined by placing egg slices in a vacuum oven at 110 C and at 380 mm Hg. Shear force was determined on an Instron Universal Testing Machine utilizing the Allo-Kramer shear cell. The crosshead speed was 50 mm/min with a 10-kg full scale load. Shear force values were reported as kilograms force per gram of sample. Sensory evaluations were performed by a semi-trained sensory panel consisting of faculty, staff, and students of the University of Georgia. Panelists were instructed to evaluate the eggs for appearance, aroma, flavor, texture, and overall acceptance. Because comparisons of treatment effects of preserved eggs were desired, fresh hard-cooked eggs were not used in the evaluation. The eggs were rated on a five-point hedonic scale with 1 being the most acceptable for flavor, appearance, aroma, overall acceptance, or toughest, and 5 being the least acceptable or least tough.
SALTED AND PRESERVED HARD-COOKED EGGS
2
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Exp. 1
Moisture
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Downloaded from http://ps.oxfordjournals.org/ at National Institute of Education Library, Serials Unit on June 13, 2015
Protein
•c
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ences in the appearance and the aroma of the eggs due to the different salt levels (Table 1). Eggs in a 5% salt solution received significantly more favorable responses for flavor, which would indicate that the panelists preferred the salt flavor at this level. Eggs held at 20% salt had the least desirable flavor but were not significantly different from the 0 and 10% salt treatments. Salt added at the 20% level resulted in significantly increased toughness over the 0% salt treatment, but there were no significant differences among the eggs that were stored at 5 and 10% salt. Overall, the 5% salt eggs were significantly the most acceptable of the treatments and the 20% salt eggs were the least acceptable to the panelists. In Experiments 1 and 2, higher salt (10 and 20%) resulted in a decreased egg moisture content (Table 2). The greater negative response of the egg moisture to the higher salt levels in Experiment 1 is probably due to the greater solution to egg ratio used in Experiment 1 as compared to Experiment 2. The results of the shear force analysis in Experiment 1 indicates as salt level increased, so did shear force (Table 2). The data for Experiment 2, however, does not agree. This difference could be due to the difference of solution to egg ratios, as previously noted, difference in storage time (40 vs. 55 days), moisture content, or an interaction of these factors. No differences in final solution pH were noted for Experiments 1 and 2 at any level within each experiment. The pH values for the first experiment were at least one whole pH unit lower than those from the second experiment. This difference again could be due to the difference in solution to egg ratio. Thus, the total acid in Experiment 1 was greater per unit of egg than in Experiment 2 and therefore less affected by the buffering effect of the eggs within the corresponding solution. As salt increased, the amount of protein in the solution increased as well (Table 2). Thus, the turbidity often noticed in egg preservative solutions may be due to extracted and precipitated proteins and not necessarily the result of bacterial growth (Ball and Saffores, 1973). In Experiment 2, there was approximately an 8 to 11% yield loss in total weight from the eggs between 0 and 30 days of storage in each of the treatments. This loss in weight was probably due to the loss of mositure (osmotic loss from the egg to the higher solute concen-
893
894
FISCHER AND FLETCHER TABLE 3. Sensory evaluations of eggs1
Salt concentration
Appearance
Aroma
Flavor
Texture
Overall acceptance
0 2.5 5 7.5
1.9a 1.8 a 1.9a 2.0 a
2.9 a 2.6 a 2.6 a 2.6 a
3.8 a 3.1ab 2.6b 2.9 b
2.3ab 1.8 b 2.4 a l.oab
3.7 a 3.1ab 2.5 b 2.5 b
tration of the solution) and, to a lesser extent, to the protein loss into the preservative solution. The sensory evaluation from Experiment 3 indicated there were no significant differences in the appearance and aroma of the eggs at the different salt levels (Table 3). The most acceptable flavor scores were from the 5 and 7.5% salt treatments, but the 2.5% treatment was not significantly different. These results paralleled those of the first experiment where the panelists preferred the eggs from 5% level salt treatments. Texture analysis results indicated there was a significant difference between the 2.5% and 5% egg; the 2.5% egg was the toughest and the 5% egg was the most tender. This could be due to the tenderizing effect of the salt on the egg. Overall acceptability placed the 5 and 7.5% eggs as the most acceptable. In Experiment 3, for both the 40- and 55-day analyses, there were no significant differences in percent moisture as the levels of salt increased (Table 4). Apparently at the lower salt (i.e., 2.5 to 7.5%), there is less
pronounced loss of moisture than resulted from Experiments 1 and 2 with the greater spread of salt concentrations (i.e., 5 to 20%). Shear force analysis in Experiment 3 did not result in a significant trend as noted in Experiment 1 (Table 4). Apparently lower salt level differences do not result in the marked toughening effect previously noted. Even though the values are not significantly different, apparently increasing the salt levels up to about 2.5% may actually increase the egg tenderness (salting-in). However, when salt approaches and exceeds 5%, the egg becomes tougher (salting-out). Similar reactions between salt and proteins are recognized in other systems such as meat. This would also explain the slight (but not significant) increase in the 7.5% salt treatment moisture level at 55 days storage. Yield values after 40 days resulted in no significant (P<.05) differences between any of the salt levels (Table 4). The loss in weight ranged from 6 to 7% for all levels. This loss is probably due to the loss in moisture and, in
TABLE 4. Physical and chemical properties of eggs'
Salt cone.
Moisture, days 40 55
0 2.5 5 7.5
72.78 a 72.04 a 71.42 a 71.35 a
Shear force, days 40 55
Yield 1 , 40 days
Salt in eggs, 40 days
93.0 a 93.1 a 94.2 a 94.1 a
.075 1.1 2.1 3.2
(kg/g) 72.92 a 74.29 a 71.15 a 71.83 a
ab
.69 .59 b .69 a b .78 a
.79 a .75 a .82 a .87 a
Salt solution, 40 days
(">) <.01 2.2 3.5 4.9
a,b Means in each individual column with different superscripts are significantly different (P<.05).
Downloaded from http://ps.oxfordjournals.org/ at National Institute of Education Library, Serials Unit on June 13, 2015
a,b Means in each column with different superscripts are significantly different (P<.05). n = 15.
SALTED AND PRESERVED HARD-COOKED EGGS
comments often associated with the lack of flavor of these eggs. ACKNOWLEDGMENTS This study was supported in part by state and Hatch funds allocated to the Georgia Agricultural Experiment Stations. REFERENCES Acton, J. C, and M. G. Johnson, 1973. Pickled eggs. 1. pH, rate of acid penetration into egg components and bacterial analyses. Poultry Sci. 52: 107-111. Angalet, S. A., H. R. Wilson, and J. L. Fry, 1976. Acceptability of pickled quail eggs. J. Food Sci. 41:449-450. Appi Reddy, B., B. Panda, and M. P. Mall, 1978. Effect of different methods of package and storage conditions on keeping quality of pickled quail eggs. Indian Poult. Gaz. 62:154—162. Arroyo, P. T., J. S. Karganiila, and O. T. Diongco, 1973. Egg studies: I. Salt curing of chicken and duck eggs. Philipp. J. Sci. 102:101-113. Ball, H. R., Jr., and M. W. Saffores, 1973. Eggs pickled in various acid strength solutions. Poultry Sci. 52:916-920. Maurer, A. J., 1975. Hard-cooking and pickling eggs as teaching aids. Poultry Sci. 54:1019-1024. SAS Institute. 1979. SAS Users Guide. 9th ed. Raleigh, NC. Trongpanich, K., and L. E. Dawson, 1974. Quality and acceptability of brined pickled duck eggs. Poultry Sci. 53:1129-1133.
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some part, the protein that precipitated out of the eggs into solution. Percent salt in the eggs ranged from less than . 1 % in the 0% eggs and up to 3.2% in the 7.5% eggs. This increase in egg salt from the 2.5% to the 7.5% eggs was approximately half of the total salt added to the solutions. From previous experiments (unpublished), it was found a minimum of 21 days is required to allow for total salt penetration into the yolk. These results would indicate that the salt transfers from the solution to the egg, and this transfer is a function of concentration and solution to egg ratio. Bacterial analyses from the three experiments indicated there were less than 10 cfu found in any of the solutions tested. Therefore, it is difficult to assess whether the addition of lower levels of salt would have any bacteriostatic effect. It appears that when low levels (2.5 to 5.0%) of salt are added to the normal citric acid, sodium benzoate-based preservative solution can contribute to the overall acceptance of commercially prepared hard-cooked eggs. The use of salt, and possibly other flavoring agents, may be of benefit in decreasing the negative
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