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The Influence of Ambient pH on Moisture Content and Yolk Index of the Hen’s Yolk*
374
H . SCHINDLER AND S. HURWITZ
fowl: physiology of the male. Chap. 11 in Reproduction in Domestic Animals, ed. H. H. Cole and P. T. Cupps. Academic Press, New York, 1959; and personal communication. Smyth, J. R., and F. P. Jeffrey, 1960. Poultry. Chap. 11 in The Artificial Insemination of
Farm Animals, Ed. E. J. Perry. Rutgers University Press, New Brunswick. Wilcox, F. H., and C. S. Shaffner, 1957. Effect of differences in salt and hydrogen ion concentration on the fertilizing ability of avian sperm. J. Appl. Physiol. 11: 429-434.
The Influence of Ambient p H on Moisture Content and Yolk Index of the Hen's Yolk* FROMM
Station,
(Received for publication September 21, 1965)
CCORDING to prevailing theory the > physical deterioration of the hen's egg yolk during storage is due to the movement of water by osmotic action from the albumen across the vitelline membrane into the yolk (Romanoff and Romanoff, 1949). However, Feeney et al. (1956) postulated that the degeneration of yolk quality is concomitant with albumen quality in that both appear to deteriorate under similar circumstances. These workers hypothesized that the causative mechanisms responsible for the physicochemical breakdown in the albumen and the vitelline membrane which supports the yolk are basically similar. The purpose of this investigation was to determine the extent to which water movement into the yolk from the albumen of the intact egg was responsible for the deterioration of yolk physical quality.
A
EXPERIMENTAL
Eggs used in this study were obtained from a flock of Single Comb White Leghorns in their initial year of production. * Contribution from the Food Science Department, North Carolina Agricultural Experiment Station, Raleigh, North Carolina. Published with the approval of the Director of Research as Paper No. 2057 of the Journal Series.
All eggs weighed between 59 and 64 gm. Since the pH of albumen, albumen physical quality and yolk physical quality appear to be interrelated (Romanoff and Romanoff, 1949), the eggs used in this study were treated in order to affect albumen pH by shell treatment. Oiling the shells of eggs with light mineral oil lessens permeability of the shell so that C0 2 loss is minimized with a resultant stabilized pH of the albumen (Almquist, 1933). Immediately after the eggs were gathered each of 3 treatment groups were either dipped in light mineral oil, had light mineral oiled applied to onehalf of the shell on the vertical axis, or held in 49°C. water for 3 minutes and thoroughly rubbed with cheese cloth while wet. A control group was carried through the experiment in conjunction with the various treatments. All eggs were held at 24 ± 1.5°C. Ten eggs within each treatment were removed from storage for analysis on the initial day of storage and after 2, 4, 7, 10, 13 and 16 days for control and washed eggs. Half oiled and oiled eggs were analyzed on the initial day of storage and after 2, 4, 7, 10, 13, 16, and 23 days. Eggs were analyzed for shell permeability according to the method of Fromm (1959) except that permeability was determined on a one
Downloaded from http://ps.oxfordjournals.org/ at New York University on April 23, 2015
DANIEL
Department of Food Science, North Carolina Agricultural Experiment Raleigh, North Carolina
375
YOLK CHARACTERISTICS
RESULTS AND DISCUSSION
The influence of age and shell treatment
9.6 -
0
2
4
7
10
AGE IN
13
16
Each observation mean for 30 eggs. 2 L,S.D..„5 0.0046 3 S.E, 0.0013
represents an
6.0 I 0
1 2
1 4
1 7
J 10
1 13
1 16
23
AGE IN DAYS
FIG. 2. The influence of age at 24° C. and shell treatment on yolk pH. 1 , 2 ' 3 1 Each observation mean for 30 eggs. 2 L.S.D..os 0.0013 3 S.E. 0.0035
represents an
arithmetic
on albumen pH, yolk pH, yolk index, moisture content of yolks, and shell permeability are presented in Figures 1 through 5 respectively. Age of the eggs had a significant effect on all factors except the pH of oiled and shell permeability of half oiled treatments. Shell permeability was the only analysis factor found to be different with
23
DAYS
AGE IN DAYS
FIG. 1. The influence of age at 24°C. and shell treatment on albumen pH. 1 ' 2 ' 3 1
6.5
arithmetic
FIG. 3. The influence of age at 24°C. and shell treatment on yolk index.1-2'3 1 Each observation mean for 30 eggs. 2 L.S.D..„5 0.0013 3 S.E. 0.0004
represents an
arithmetic
Downloaded from http://ps.oxfordjournals.org/ at New York University on April 23, 2015
egg basis. Albumen pH and yolk pH were evaluated on an expanded scale pH meter. Yolk index was calculated according to the method of Sharpe (1929). Percent yolk moisture was determined by initially heating the yolk material for 6 hours at 100°C. without vacuum and then for 1 hour at 100°C. with vacuum at 23 inches of mercury. The two-step procedure was necessary to avoid bubbling in vacuo. All analyses were performed on each egg within each treatment. This experiment was replicated twice and the data combined in the statistical analysis.
376
D. FROMM
__——^T^5
^ &
x
x —
"
• •—•
Control o—~o Washed G D 1/2 Oiled X -X Oiled
i i
i
i 10
13
16
AGE IN DAYS
age between control and washed treatments. There were differences found between the other shell treatment groups over age among all analyses except yolk pH. The data in Table 1 show the influence of age on the various analysis factors for respective treatments expressed as correlation coefficients. The relationship between age and the various physicochemical attributes were significant except for albumen
Yolk index is the ratio of yolk height and yolk width. As aging of the egg occurs, the yolk has a tendency to flatten and the vitelline membrane surrounding the yolk becomes weak. Romanoff and Romanoff (1949) stated that the enlargement of the
10
13
16
AGE IN DAYS
FIG. 5. The influence of age at 24° C. and shell treatment on shell permeability as measured by optical density of methyl alcohol shell extractions. 1 ' 2 ' 3 1 Each observation represents an arithmetic mean for 30 eggs. 2 L.S.D..o5 0.0180 S S.E. 0.0052
TABLE 1.—Correlation coefficients illustrating the influence of age on yolk index, albumen pH, moisture content of the yolk and shell permeability {optical density) within different shell treatments1 Shell treatment Control Washed Half oiled Oiled
Yolk index .94*' .94*' .94*' .44*
Albumen pH
Yolk Moisture content
Shell permeability
.70" .71*' .77*' -.17
.94** .90** .90** .91**
.76" .82* .29 .18
*p=<0.05 **p=<0.01 1 Differences in yolk pH with age were not detected between the various shell treatments (Fig. 2).
Downloaded from http://ps.oxfordjournals.org/ at New York University on April 23, 2015
4. The influence of age at 24°C. and shell treatment on percent yolk moisture. 1 ' 2 ' 3 I E a c h observation represents an arithmetic mean for 30 eggs. 2 L.S.D..„5 0.0386 3 S.E. 0.0112 FIG.
pH in the oiled group and shell permeability (O.D.) for half oiled and oiled treatments. Correlation coefficients for the various analysis factors within each shell treatment are presented in Table 2 The relationship between pH and yolk index were not significant except for the half oiled eggs. The lack of correlation between pH and yolk index for control and washed groups may be attributed to the curvilinear relationship which existed from the lower pH to the upper pH levels (Fig. 6). The relationship between pH and yolk moisture content and yolk index and yolk moisture content were significant within all treatments except for oiled eggs (Table 2). These data are presented graphically in Figures 7 and 8, respectively. Shell permeability significantly influenced yolk index and yolk moisture content in control and washed groups, and yolk moisture content in the oiled treatments (Table 2). Since differences in yolk pH according to shell treatment were not detected with age (Fig. 2), it was deemed unnecessary to relate this analysis factor to other analysis factors according to shell treatment.
377
YOLK CHARACTERISTICS
TABLE 2.—Correlation coefficients between various analysis factors within shell treatments Shell treatment Analysis factors Albumen pHXyolk index Albumen pHXyolk moisture Yolk moisture X yolk index Shell permeabilityXalbumen p H Shell permeability X yolk index Shell permeability X yolk moisture
Control
Washed
Half oiled
Oiled
-.57 .87** -.87** .68 -.93** .93**
-.63 .89** — 89** .88** -.90** 99**
-.74* .96** -.85** .53 -.51 .49
-.27 .10 -.63 -.50 -.56 .94**
yolk during aging of the egg is due to an increased content of water. This elevation of yolk moisture content is caused by osmotic migration of water from the albumen into the yolk across the vitelline membrane. The increased volume of water in the yolk contents theoretically should stretch the vitelline membrane with the resultant flattening of the yolk. Fromm and Matrone (1962) reported that a significant relationship existed between yolk index and strength of the vitelline membrane. It appears from the data presented in this report that the moisture content of the yolk is not necessarily a criterion for yolk index (Fig. 8). Even at a high moisture
8.0
85
9.0
9.5
ALBUMEN pH
Downloaded from http://ps.oxfordjournals.org/ at New York University on April 23, 2015
* p=<0.05 'P= ""'
content the yolk index was of good quality for those eggs in which the albumen was maintained at or below pH 8.0 although the movement of moisture into the yolk was somewhat inhibited (Fig. 4). These results would tend to indicate that the pH of the albumen which under normal conditions rises with age from pH 7.6 to 9.S is the predominant factor affecting the rigidity and strength of the vitelline membrane which encompasses the yolk. Moran (1936) postulated that the vitelline membrane becomes more elastic and loses its strength as the egg grows older.
8.0
8.5
9.0
9.5
ALBUMEN pH
FIG. 6. The influence of albumen pH on yolk index.1
FIG. 7. The influence of albumen pH on yolk moisture content.1
1 Each observation represents an arithmetic mean for 30 eggs.
' Each observation represents an arthmetic mean for 30 eggs.
378
D. FROMM
46
48
50
52
PERCENT YOLK MOISTURE FIG. 8. The influence of yolk moisture content on yolk index.1 J Each observation represents an arithmetic mean for 30 eggs.
Fromm and Matrone (1962) demonstrated this phenomenon. Fromm (1964) reported that the vitelline membrane loses weight as the egg ages. He found that a significant relationship exists between yolk index, membrane strength and membrane weight. Fromm (1964) also showed photographic evidence of deterioration in the vitelline membrane with age and hypothesized that the substance that was being lost from the membrane with age was the chalaziferous
SUMMARY The physical structure of the yolk as influenced by water movement from the albumen to the yolk of the egg was evaluated. It was found that the degree of hydration of the yolk material does not in itself significantly affect yolk index. It appears that the pH of the albumen is the predominant factor affecting the structure of the yolk. Hypotheses regarding these phenomena are presented. ACKNOWLEDGMENTS The author wishes to express his appreciation to Edwina Beard and Joy Reekie
Downloaded from http://ps.oxfordjournals.org/ at New York University on April 23, 2015
.30
layer immediately surrounding the vitelline membrane. However, he was not able to demonstrate this by histological methods. The albumen and the chalazae are protein gels which consists of ovomucin fibers to which water is apparently bound (Almquist, 1933; and Moran, 1936). The ability of gels to maintain themselves is controlled by many environmental factors. One important chemical factor is environmental pH. Gels have an optimum pH at which point the fibers will bind the most water. As the pH departs from this optimum, water becomes liberated from the fibers and as a result the gel commences a gradual breakdown. This was observed by Almquist and Lorenz (1932). The previously described gel phenomenon may be what is happening in the albumen and on the surface of the vitelline membrane; for as long as the pH remains at about 8.0 the albumen remains firm (Romanoff and Romanoff, 1949) and the vitelline membrane has considerable substance (Fromm, 1964). However, as the pH becomes more alkaline with age the albumen loses its gellike characteristics and the vitelline membrane becomes more flaccid and weakened (Fromm and Matrone, 1962) with the resultant aged or low grade egg.
YOLK CHARACTERISTICS
for laboratory technical assistance, and to Ralph B. KeUy and R. B. Kelly of Kelly Poultry Farms, Garner, North Carolina for their cooperation during this study. REFERENCES
nation of egg shell permeability. Poultry Sci. 38: 171-173. Fromm, D., and G. Matrone, 1962. A rapid method for evaluating the strength of the vitelline membrane of the hen's egg yolk. Poultry Sci. 4 1 : 1516-1521. Fromm, D., 1964. Strength distribution, weight and some histological aspects of the vitelline membrane of the hen's egg yolk. Poultry Sci. 43 : 1240-1248. Moran, T., 1936. Food investigation. Dept. Sci. Ind. Res. Food Invest. Repts (1935-36) 40-41. Romanoff, A. L., and A. J. Romanoff, 1949. The Avian Egg. John Wiley and Sons, Inc. New York, New York. Sharp, P. F., 1929. What one week may do to an egg. U. S. Egg Poultry Mag. 35: 14-17.
The Relationship of Feed and Water Deprivation to Greenish Gizzard Mucous Membrane and Contents in Chickens B . W . BlERER AND T . H . ELEAZER The South Carolina Agricultural Experiment Station, Clemson University, Clemson, S.C. (Received for publication September 23, 1965)
IXON (1963) observed greenish gizzard mucous membranes and contents in broilers in slaughter houses and believed the incidence was related to feed and water deprivation during shipping. When greenish gizzard mucous membranes and contents were observed by the authors during the course of a feed and water deprivation experiment, these lesions were deemed worthy of a special study.
D
MATERIALS AND METHODS
Of 70 individually caged White Leghorn hens, 40 were given water but no feed, 10 feed but no water, and 20 hens ad libitum feed and water. Of the 40 chickens receivThe South Carolina Agricultural Experiment Station, Clemson University, Clemson, South Carolina. Published with permission of the director as Technical Contribution No. 556.
ing water but no feed, 5 were killed for examination after 6, 7, 8, 9, 10, 11, 24, and 48 hours of treatment. Five hen groups of those receiving feed but no water were examined after 24 and 48 hours, and of those receiving feed and water ad libitum after 6, 10, 24, and 48 hours of treatment. Gizzard contents were collected from the hens killed after 48 hours of treatment to supply separate pooled samples from the 5 hens receiving water but no feed, the 5 hens receiving feed but no water, and from the 5 hens receiving feed and water ad libitum. These 3 pooled samples were each subjected to a modified van den Berg's test (Hawk et al., 1954; Gradwohl, 1956) for bilirubin. RESULTS AND DISCUSSION The results as outlined in Table 1 indicated that greenish gizzard mucous mem-
Downloaded from http://ps.oxfordjournals.org/ at New York University on April 23, 2015
Almquist, H. J., and F. W. Lorenz, 1932. Liquefaction of egg whites. Nulaid News, March. Almquist, H. J., 1933. Relation of the candling appearance of eggs to their quality. Univ. California Agr. Exp. Sta. Bull. 561. Feeney, R. E., J. M. Weaver, J. R. Jones and M. B. Rhodes, 1956. Studies of the kinetics and mechanisms of yolk deterioration in shell eggs. Poultry Sci. 35: 1061-1066. Fromm, D., 1959. A rapid method for the determi-
379
H . SCHINDLER AND S. HURWITZ
fowl: physiology of the male. Chap. 11 in Reproduction in Domestic Animals, ed. H. H. Cole and P. T. Cupps. Academic Press, New York, 1959; and personal communication. Smyth, J. R., and F. P. Jeffrey, 1960. Poultry. Chap. 11 in The Artificial Insemination of
Farm Animals, Ed. E. J. Perry. Rutgers University Press, New Brunswick. Wilcox, F. H., and C. S. Shaffner, 1957. Effect of differences in salt and hydrogen ion concentration on the fertilizing ability of avian sperm. J. Appl. Physiol. 11: 429-434.
The Influence of Ambient p H on Moisture Content and Yolk Index of the Hen's Yolk* FROMM
Station,
(Received for publication September 21, 1965)
CCORDING to prevailing theory the > physical deterioration of the hen's egg yolk during storage is due to the movement of water by osmotic action from the albumen across the vitelline membrane into the yolk (Romanoff and Romanoff, 1949). However, Feeney et al. (1956) postulated that the degeneration of yolk quality is concomitant with albumen quality in that both appear to deteriorate under similar circumstances. These workers hypothesized that the causative mechanisms responsible for the physicochemical breakdown in the albumen and the vitelline membrane which supports the yolk are basically similar. The purpose of this investigation was to determine the extent to which water movement into the yolk from the albumen of the intact egg was responsible for the deterioration of yolk physical quality.
A
EXPERIMENTAL
Eggs used in this study were obtained from a flock of Single Comb White Leghorns in their initial year of production. * Contribution from the Food Science Department, North Carolina Agricultural Experiment Station, Raleigh, North Carolina. Published with the approval of the Director of Research as Paper No. 2057 of the Journal Series.
All eggs weighed between 59 and 64 gm. Since the pH of albumen, albumen physical quality and yolk physical quality appear to be interrelated (Romanoff and Romanoff, 1949), the eggs used in this study were treated in order to affect albumen pH by shell treatment. Oiling the shells of eggs with light mineral oil lessens permeability of the shell so that C0 2 loss is minimized with a resultant stabilized pH of the albumen (Almquist, 1933). Immediately after the eggs were gathered each of 3 treatment groups were either dipped in light mineral oil, had light mineral oiled applied to onehalf of the shell on the vertical axis, or held in 49°C. water for 3 minutes and thoroughly rubbed with cheese cloth while wet. A control group was carried through the experiment in conjunction with the various treatments. All eggs were held at 24 ± 1.5°C. Ten eggs within each treatment were removed from storage for analysis on the initial day of storage and after 2, 4, 7, 10, 13 and 16 days for control and washed eggs. Half oiled and oiled eggs were analyzed on the initial day of storage and after 2, 4, 7, 10, 13, 16, and 23 days. Eggs were analyzed for shell permeability according to the method of Fromm (1959) except that permeability was determined on a one
Downloaded from http://ps.oxfordjournals.org/ at New York University on April 23, 2015
DANIEL
Department of Food Science, North Carolina Agricultural Experiment Raleigh, North Carolina
375
YOLK CHARACTERISTICS
RESULTS AND DISCUSSION
The influence of age and shell treatment
9.6 -
0
2
4
7
10
AGE IN
13
16
Each observation mean for 30 eggs. 2 L,S.D..„5 0.0046 3 S.E, 0.0013
represents an
6.0 I 0
1 2
1 4
1 7
J 10
1 13
1 16
23
AGE IN DAYS
FIG. 2. The influence of age at 24° C. and shell treatment on yolk pH. 1 , 2 ' 3 1 Each observation mean for 30 eggs. 2 L.S.D..os 0.0013 3 S.E. 0.0035
represents an
arithmetic
on albumen pH, yolk pH, yolk index, moisture content of yolks, and shell permeability are presented in Figures 1 through 5 respectively. Age of the eggs had a significant effect on all factors except the pH of oiled and shell permeability of half oiled treatments. Shell permeability was the only analysis factor found to be different with
23
DAYS
AGE IN DAYS
FIG. 1. The influence of age at 24°C. and shell treatment on albumen pH. 1 ' 2 ' 3 1
6.5
arithmetic
FIG. 3. The influence of age at 24°C. and shell treatment on yolk index.1-2'3 1 Each observation mean for 30 eggs. 2 L.S.D..„5 0.0013 3 S.E. 0.0004
represents an
arithmetic
Downloaded from http://ps.oxfordjournals.org/ at New York University on April 23, 2015
egg basis. Albumen pH and yolk pH were evaluated on an expanded scale pH meter. Yolk index was calculated according to the method of Sharpe (1929). Percent yolk moisture was determined by initially heating the yolk material for 6 hours at 100°C. without vacuum and then for 1 hour at 100°C. with vacuum at 23 inches of mercury. The two-step procedure was necessary to avoid bubbling in vacuo. All analyses were performed on each egg within each treatment. This experiment was replicated twice and the data combined in the statistical analysis.
376
D. FROMM
__——^T^5
^ &
x
x —
"
• •—•
Control o—~o Washed G D 1/2 Oiled X -X Oiled
i i
i
i 10
13
16
AGE IN DAYS
age between control and washed treatments. There were differences found between the other shell treatment groups over age among all analyses except yolk pH. The data in Table 1 show the influence of age on the various analysis factors for respective treatments expressed as correlation coefficients. The relationship between age and the various physicochemical attributes were significant except for albumen
Yolk index is the ratio of yolk height and yolk width. As aging of the egg occurs, the yolk has a tendency to flatten and the vitelline membrane surrounding the yolk becomes weak. Romanoff and Romanoff (1949) stated that the enlargement of the
10
13
16
AGE IN DAYS
FIG. 5. The influence of age at 24° C. and shell treatment on shell permeability as measured by optical density of methyl alcohol shell extractions. 1 ' 2 ' 3 1 Each observation represents an arithmetic mean for 30 eggs. 2 L.S.D..o5 0.0180 S S.E. 0.0052
TABLE 1.—Correlation coefficients illustrating the influence of age on yolk index, albumen pH, moisture content of the yolk and shell permeability {optical density) within different shell treatments1 Shell treatment Control Washed Half oiled Oiled
Yolk index .94*' .94*' .94*' .44*
Albumen pH
Yolk Moisture content
Shell permeability
.70" .71*' .77*' -.17
.94** .90** .90** .91**
.76" .82* .29 .18
*p=<0.05 **p=<0.01 1 Differences in yolk pH with age were not detected between the various shell treatments (Fig. 2).
Downloaded from http://ps.oxfordjournals.org/ at New York University on April 23, 2015
4. The influence of age at 24°C. and shell treatment on percent yolk moisture. 1 ' 2 ' 3 I E a c h observation represents an arithmetic mean for 30 eggs. 2 L.S.D..„5 0.0386 3 S.E. 0.0112 FIG.
pH in the oiled group and shell permeability (O.D.) for half oiled and oiled treatments. Correlation coefficients for the various analysis factors within each shell treatment are presented in Table 2 The relationship between pH and yolk index were not significant except for the half oiled eggs. The lack of correlation between pH and yolk index for control and washed groups may be attributed to the curvilinear relationship which existed from the lower pH to the upper pH levels (Fig. 6). The relationship between pH and yolk moisture content and yolk index and yolk moisture content were significant within all treatments except for oiled eggs (Table 2). These data are presented graphically in Figures 7 and 8, respectively. Shell permeability significantly influenced yolk index and yolk moisture content in control and washed groups, and yolk moisture content in the oiled treatments (Table 2). Since differences in yolk pH according to shell treatment were not detected with age (Fig. 2), it was deemed unnecessary to relate this analysis factor to other analysis factors according to shell treatment.
377
YOLK CHARACTERISTICS
TABLE 2.—Correlation coefficients between various analysis factors within shell treatments Shell treatment Analysis factors Albumen pHXyolk index Albumen pHXyolk moisture Yolk moisture X yolk index Shell permeabilityXalbumen p H Shell permeability X yolk index Shell permeability X yolk moisture
Control
Washed
Half oiled
Oiled
-.57 .87** -.87** .68 -.93** .93**
-.63 .89** — 89** .88** -.90** 99**
-.74* .96** -.85** .53 -.51 .49
-.27 .10 -.63 -.50 -.56 .94**
yolk during aging of the egg is due to an increased content of water. This elevation of yolk moisture content is caused by osmotic migration of water from the albumen into the yolk across the vitelline membrane. The increased volume of water in the yolk contents theoretically should stretch the vitelline membrane with the resultant flattening of the yolk. Fromm and Matrone (1962) reported that a significant relationship existed between yolk index and strength of the vitelline membrane. It appears from the data presented in this report that the moisture content of the yolk is not necessarily a criterion for yolk index (Fig. 8). Even at a high moisture
8.0
85
9.0
9.5
ALBUMEN pH
Downloaded from http://ps.oxfordjournals.org/ at New York University on April 23, 2015
* p=<0.05 'P= ""'
content the yolk index was of good quality for those eggs in which the albumen was maintained at or below pH 8.0 although the movement of moisture into the yolk was somewhat inhibited (Fig. 4). These results would tend to indicate that the pH of the albumen which under normal conditions rises with age from pH 7.6 to 9.S is the predominant factor affecting the rigidity and strength of the vitelline membrane which encompasses the yolk. Moran (1936) postulated that the vitelline membrane becomes more elastic and loses its strength as the egg grows older.
8.0
8.5
9.0
9.5
ALBUMEN pH
FIG. 6. The influence of albumen pH on yolk index.1
FIG. 7. The influence of albumen pH on yolk moisture content.1
1 Each observation represents an arithmetic mean for 30 eggs.
' Each observation represents an arthmetic mean for 30 eggs.
378
D. FROMM
46
48
50
52
PERCENT YOLK MOISTURE FIG. 8. The influence of yolk moisture content on yolk index.1 J Each observation represents an arithmetic mean for 30 eggs.
Fromm and Matrone (1962) demonstrated this phenomenon. Fromm (1964) reported that the vitelline membrane loses weight as the egg ages. He found that a significant relationship exists between yolk index, membrane strength and membrane weight. Fromm (1964) also showed photographic evidence of deterioration in the vitelline membrane with age and hypothesized that the substance that was being lost from the membrane with age was the chalaziferous
SUMMARY The physical structure of the yolk as influenced by water movement from the albumen to the yolk of the egg was evaluated. It was found that the degree of hydration of the yolk material does not in itself significantly affect yolk index. It appears that the pH of the albumen is the predominant factor affecting the structure of the yolk. Hypotheses regarding these phenomena are presented. ACKNOWLEDGMENTS The author wishes to express his appreciation to Edwina Beard and Joy Reekie
Downloaded from http://ps.oxfordjournals.org/ at New York University on April 23, 2015
.30
layer immediately surrounding the vitelline membrane. However, he was not able to demonstrate this by histological methods. The albumen and the chalazae are protein gels which consists of ovomucin fibers to which water is apparently bound (Almquist, 1933; and Moran, 1936). The ability of gels to maintain themselves is controlled by many environmental factors. One important chemical factor is environmental pH. Gels have an optimum pH at which point the fibers will bind the most water. As the pH departs from this optimum, water becomes liberated from the fibers and as a result the gel commences a gradual breakdown. This was observed by Almquist and Lorenz (1932). The previously described gel phenomenon may be what is happening in the albumen and on the surface of the vitelline membrane; for as long as the pH remains at about 8.0 the albumen remains firm (Romanoff and Romanoff, 1949) and the vitelline membrane has considerable substance (Fromm, 1964). However, as the pH becomes more alkaline with age the albumen loses its gellike characteristics and the vitelline membrane becomes more flaccid and weakened (Fromm and Matrone, 1962) with the resultant aged or low grade egg.
YOLK CHARACTERISTICS
for laboratory technical assistance, and to Ralph B. KeUy and R. B. Kelly of Kelly Poultry Farms, Garner, North Carolina for their cooperation during this study. REFERENCES
nation of egg shell permeability. Poultry Sci. 38: 171-173. Fromm, D., and G. Matrone, 1962. A rapid method for evaluating the strength of the vitelline membrane of the hen's egg yolk. Poultry Sci. 4 1 : 1516-1521. Fromm, D., 1964. Strength distribution, weight and some histological aspects of the vitelline membrane of the hen's egg yolk. Poultry Sci. 43 : 1240-1248. Moran, T., 1936. Food investigation. Dept. Sci. Ind. Res. Food Invest. Repts (1935-36) 40-41. Romanoff, A. L., and A. J. Romanoff, 1949. The Avian Egg. John Wiley and Sons, Inc. New York, New York. Sharp, P. F., 1929. What one week may do to an egg. U. S. Egg Poultry Mag. 35: 14-17.
The Relationship of Feed and Water Deprivation to Greenish Gizzard Mucous Membrane and Contents in Chickens B . W . BlERER AND T . H . ELEAZER The South Carolina Agricultural Experiment Station, Clemson University, Clemson, S.C. (Received for publication September 23, 1965)
IXON (1963) observed greenish gizzard mucous membranes and contents in broilers in slaughter houses and believed the incidence was related to feed and water deprivation during shipping. When greenish gizzard mucous membranes and contents were observed by the authors during the course of a feed and water deprivation experiment, these lesions were deemed worthy of a special study.
D
MATERIALS AND METHODS
Of 70 individually caged White Leghorn hens, 40 were given water but no feed, 10 feed but no water, and 20 hens ad libitum feed and water. Of the 40 chickens receivThe South Carolina Agricultural Experiment Station, Clemson University, Clemson, South Carolina. Published with permission of the director as Technical Contribution No. 556.
ing water but no feed, 5 were killed for examination after 6, 7, 8, 9, 10, 11, 24, and 48 hours of treatment. Five hen groups of those receiving feed but no water were examined after 24 and 48 hours, and of those receiving feed and water ad libitum after 6, 10, 24, and 48 hours of treatment. Gizzard contents were collected from the hens killed after 48 hours of treatment to supply separate pooled samples from the 5 hens receiving water but no feed, the 5 hens receiving feed but no water, and from the 5 hens receiving feed and water ad libitum. These 3 pooled samples were each subjected to a modified van den Berg's test (Hawk et al., 1954; Gradwohl, 1956) for bilirubin. RESULTS AND DISCUSSION The results as outlined in Table 1 indicated that greenish gizzard mucous mem-
Downloaded from http://ps.oxfordjournals.org/ at New York University on April 23, 2015
Almquist, H. J., and F. W. Lorenz, 1932. Liquefaction of egg whites. Nulaid News, March. Almquist, H. J., 1933. Relation of the candling appearance of eggs to their quality. Univ. California Agr. Exp. Sta. Bull. 561. Feeney, R. E., J. M. Weaver, J. R. Jones and M. B. Rhodes, 1956. Studies of the kinetics and mechanisms of yolk deterioration in shell eggs. Poultry Sci. 35: 1061-1066. Fromm, D., 1959. A rapid method for the determi-
379