Some Factors Affecting Meat Yield from Young Ducks1 W. J. STADELMAN and C. F. MEINERT Department of Animal Sciences, Purdue University, West Lafayette, Indiana 47907, and Maple Leaf Farms, Rt. 1, Milford, Indiana 46542 (Received for publication October 21, 1976) ABSTRACT White Pekin ducks were grown using standard management procedures. Ten ducklings were processed and frozen at each of the following ages: 28, 35, 41, 46, 48, 50, 53, 55, 57, 63 and 68 days. Necks and giblets were discarded. The percentage dressed duck, without neck and giblets, in breast meat, leg meat, total wing, and skin and fat was determined on all ducks. The percentage of breast meat increased from 4.79% to 15.93% for ducks 28 and 63 days of age, respectively. Leg meat decreased from 17.97% to 12.28% for the same ages of ducks. The percentage of skin and fat reached a minimum with 53 day old ducks. A second experiment was conducted with six age groups, six ducks each, from 28 to 51 days of age. Percentages of breast meat were almost identical in the two studies. Studies were also conducted to determine the effect of injecting a tripolyphosphate solution as 3% of body weight on yield of cooked duck meat. Injected birds yielded a higher percentage of meat and a lower percentage of skin. The skin of injected birds was crisper than skin of roasted controls. Poultry Science 56:1145-1147, 1977 INTRODUCTION T h e desirability of a roasted d u c k is greatly influenced b y the distribution of muscling over t h e carcass and also by t h e crispness of t h e skin on t h e roasted p r o d u c t . T h e r e is relatively little information in t h e literature concerning yields of edible tissues in d u c k s . Orr ( 1 9 6 9 ) indicated, w i t h o u t d a t a t o verify each p o i n t being s h o w n , t h a t dressing percentages and m e a t yield of d u c k s and geese will vary with breed, age, sex, weight and grade. Snyder a n d Orr ( 1 9 5 3 ) reported a relationship b e t w e e n age and percentage carcass m e a t of geese. T h e percentage of b o n e decreased rapidly from 5 to 12 weeks with only a slight increase in percentage of skin and fat so percentage of m e a t increased. F r o m 12 t o 19 w e e k s of age, t h e skin and fat percentage increased more rapidly t h a n t h e percentage of b o n e decreased, t h u s t h e percentage of m e a t also decreased. Orr ( 1 9 6 9 ) reported a c o o k e d m e a t yield of 4 0 t o 4 3 p e r c e n t of ready-to-cook carcass weight for 7 t o 8 w e e k s old ducks. C l e m e n t s and Wint e r ( 1 9 5 6 ) r e p o r t e d a 4 1 percent yield. Deskins and Winter ( 1 9 5 6 ) also r e p o r t e d an increase in percentage of breast and a decrease in percentage of leg and thigh with increasing age of geese. Factors affecting p o u l t r y m e a t yields
'Journal Paper No. 6492, Agricultural Experiment Station, Purdue University, West Lafayette, Indiana 47907.
are reviewed b y Swanson et al. ( 1 9 6 4 ) and Carlson et al. ( 1 9 7 5 ) . T h e p u r p o s e of these studies was t o determine t h e effects of age and of p h o s p h a t e salts injection on m e a t distribution on the carcass of ducklings a n d of yield of t o t a l edible product. MATERIALS AND METHODS A series of studies were c o n d u c t e d t o determine t h e effect of age o n meat d i s t r i b u t i o n on t h e ducklings carcass. In t h e first t e s t six c o m mercially g r o w n White Pekin t y p e ducklings were processed in a commercial processing p l a n t using a d o u b l e wax dip following rough picking at each of t h e following days of age: 2 8 , 3 5 , 4 0 , 4 3 , 4 7 and 4 9 . Carcass weights witho u t n e c k a n d giblets were t a k e n . Weights of wings, leg a n d thigh m e a t , breast m e a t , skin a n d fat, a n d remaining carcass were r e c o r d e d . A s e c o n d s t u d y with t h e same observations being m a d e was c o n d u c t e d with ten ducklings a t each age being processed in t h e University p o u l t r y processing facilities. N o wax was used. Ducklings were scalded at 6 0 C. for 9 0 seconds a n d picked in a Barker cyclomatic picker for 55 seconds. Ages at processing w e r e : 2 8 , 3 5 , 4 1 , 4 6 , 4 8 , 50, 5 3 , 5 5 , 5 7 , 6 3 a n d 6 8 days. All ducks in b o t h e x p e r i m e n t s were v a c u u m packaged and frozen. Ducks were t h a w e d at r o o m t e m p e r a t u r e for 8 t o 12 h o u r s p r i o r t o d e b o n ing.
STADELMAN AND MEINERT
TABLE I.-Effect of age on tissue distribution of ducks (Experiment 1) Percentage of (days)
Leg& thigh meat
28 35 40 43 47 49
24.5a' 24.9 a 24.8 a 24.7 a 25.9 a 27.6 b
4.8 a 6.6b 7.7 C 9.2 d 11.5 e 12.6 f
37.2 35.4 35.2 36.7 36.1 33.3
19.5 b 18.3 b 17.0 a b 15.5 a 14.4 a 15.1 a
temperature of 85° C as measured deep in the breast muscle. Percentage yields were calculated based on frozen carcass weight with neck and giblets. A second study replicated the earlier work using 26 ducks in each the injected and control groups. All data collected were subjected to statistical analysis of variance to aid in interpretation of the data. RESULTS AND DISCUSSION
* Values within a column followed by the same letter not significantly different from each other.
In an attempt to minimize cooking losses from roasted duck injection with aqueous solutions of various salts have been used (Klinger and Stadelman, 1975). An attempt was made to determine what effect such injection had on cooked meat yield. In the first study of the effect of injection, 18 ducks were injected with 3% by weight of a mixture of water, salt (10%), sodium tripolyphosphate (6%), and flavorings. A comparable, randomly selected 18 non-injected ducks were used as controls. All ducks were Cryovac packaged and frozen in sodium chloride brine spray at —18°C. Weights were recorded for frozen carcass weight with neck and giblets, thawed carcass weight, drained cooked weight, drippings, bones, edible meat, and skin and separable fat. All ducks were roasted without stuffing by placing on wire racks over a drip collection pan in electrically heated still air ovens at 163°C. and cooked to an internal
The yields of uncooked duck product as affected by age at processing are summarized in Tables 1 and 2. Total meat yield increased as age increased at a rather slow rate to a maximum at 9 weeks of age. Breast meat as a percentage of body weight without neck and giblets increased linearly to 9 weeks of age. The percentage of leg and thigh meat decreased generally from the start of the experiment at four weeks of age to the maximum age studied, 68 days of age. The increase in percentage of breast meat was faster than the decrease in leg and thigh meat so the percentage of total meat increased. The changes in percentage of breast meat from the 46th to 57th day of age were of particular importance. This change from 10.2% to 14.6% of the total carcass weight results in changing from a rather small serving to a very generous serving. Only a few years ago many duck processors were routinely growing ducks to 57 days of age before processing. Recently the normal processing age has been reduced to 49 days with some ducks being marketed at 46 or 47 days of age. The wide change
TABLE 2.—Effect of age on tissue distribution of ducks (Experiment 2) Percentage of (days)
Leg& thigh meat
28 35 41 46 48 50 53 55 57 63 68
22.8 a * 23.7 a 23.la 25.0 a b 25.8ab 26.3bc 27.7 C 27.9 C 28.2C 28.2 C 27.4C
4.8 a 7.0 b 8.4C 10.2 d 11.8« 12.3 e 14.0 f 14.1 f 14.6% 15.9 h 15.4gh
18.0 e 16.7 d 14.7 C 14.8 C 14.0 C 14.0 C 13.7 b c 13.5bc 13.4 b c 12.3ab 12.0 a
41.6 b 41.0 b 40.4 a b 38.4 a b 37.5 a b 38.7 a b 36.3 a 37.9 a b 39.7 a b 37.5 a b 36.4 a
25.6 b 24.0 b 24.6 b 24.6 b 23.8 b 23.0 a b 23.2ab 21.8 a 21.3 a 23.5ab 24.1b
9.3 a ll.lt> 11.0 b 11.4 b 11.4 b 11.5 b 11.8 b 11.8 b ll.lb 11.8 b 12.1 b
•See Table 1.
MEAT YIELD OF YOUNG DUCKS
TABLE 3.—Effect of aqueous salts solution injection on yield of roasted duck Percent thaw loss
Percent cooked yield
Exp. 3 Injected Non-injected
14.5 a 14.9
27.5 b * 25.2^
Exp. 4 Injected Non-injected
14.6 a 16.4b
56.9 a 59.4b
Includes weight of neck and giblets removed after thawing in experiment 3. •See Table 1.
in meat distribution on the carcass during this relatively short life span suggests that the industry may have moved too far towards maximizing growth rates and feed efficiency while trying to maintain the same weight of duckling in the market. The percentage of the carcass separated as skin and fat changed slightly from 28 days of age to 68 days of age. Because of the much higher surface area to total weight on the 28 days old duckr'the percentage of skin and adhering fat actually decreased as the ducks aged to about 57 days of age. Based on results of these studies it would appear that moving the processing age back towards 8 weeks of age from the current 7 week age could be advantageous. The percentage of carcass in the breast rrieat would be increased and percentage of skin and fat would be decreased to give a product with likely greater consumer acceptability. The data in Table 3 summarizes observations made on ducks injected with an aqueous salt solution as compared with non-injected ducks. The percentage of the raw carcass weight recovered as cooked meat was increased by injection in both experiments with differences in experiment 3 being statistically significant (P=0.002) and non-significant in experiment 4 (P=0.217). It was interesting to observe the reduction in percentage of skin and fat resulting from injection. The difference was not significant (P=0.173) in experiment 3 but was significant (P<0.001) in experiment 4. No data are available to explain this observation but it is theorized that with the injected salts in the meat heat transfer was improved so higher sur-
face temperatures might have been reached. Injection of ducks resulted in a greater cooked meat yield but either a non-significant increase in total yield (experiment 3) or a significant (P=0.002) decrease (experiment 4) in total yield. These results were due largely to a drier, less greasy skin. The difference between the two experiments was likely the result of cooking to an end point temperature of 85° C in experiment 3 and for a fixed time to assure a cooked product in experiment 4. The time was established by determining the maximum time it took for the particular ovens used to achieve an end point temperature of 85° C. (Klinger and Stadelman, 1975). Using the fixed time resulted in a drier skin on the injected birds as indicated by a statistically significant difference.
REFERENCES Carlson, C. W., W. W. Marion, B. F. Miller and T. L. Goodwin, 1975. Factors affecting poultry meat yields. South Dakota State University Agric. Expt. Sta. Bull. No. 630. Clements, P., and A. R. Winter, 1956. Duck shrinkage from farm to table and cooked edible meat of parts. Amer. Egg Poultry Review, 18(9):44-48. Deskins, B. and A. R. Winter, 1956. Cooked, edible meat in parts of poultry. II Geese. J. Amer. Dietetic Assn. 32:211-213. Klinger, S. D., and W. J. Stadelman, 1975. Flavor of reheated roast duck. Poultry Sci. 54:1278-1282. Orr, H. S., 1969. Duck and goose raising. Ontario Dept. of Agric. Bull. No. 532:52pp. Snyder, E. S., and H. L. Orr, 1953. Market possibilities and yields of goslings dressed at various age. Poultry Sci. 32:181-182. Swanson, M. H., C. W. Carlson and J. L. Fry, 1964. Factors affecting poultry meat yields. University of Minnesota. Agric. Expt. Sta. Bull. No. 476.