- Email: [email protected]
Effect of Dry-Chilling on the Flavor of Fried Chicken1
Effect of Dry-Chilling on the Flavor of Fried Chicken 1 K. K. HALE, JR., 2 W. J. STADELMAN AND V. D. BRAMBLETT
Departments of Animal Sciences and Home Economics, Agricultural Experiment Station, Purdue University, Lafayette, Indiana 47907 (Received for publication May 1, 1972)
POULTRY SCIENCE 52: 253-262,
INTRODUCTION
C
ONTINUOUS ice-slush has been used over the past two decades as a successful means of rapidly reducing the temperature of freshly eviscerated broiler carcasses while at the same time improving yields by water uptake during the chilling process. The reports of Kotula et al. (1960) and May et al. (1963) have helped to demonstrate that water picked up during ice-slush continuous chilling process is loosely bound and much of it is leached out before the product reaches the consumer. Stevens (1970) noted that using a dry-chill process in lieu of ice-slush helped overcome some of the drip loss and packaged product appearance problems experienced with wetchilling. While conducting some preliminary experiments with dry-chilled poultry, a subtle but consistent flavor difference between wet- and dry-chilled products was noted. These results were consistent with those of Pippen and Klose (19SS) who found that broth prepared from chicken immersed in ice water for as little as three hours had significantly less flavor than broth from unsoaked birds. The primary purpose of "Journal Paper No. 4727 Purdue Agricultural Experiment Station, Lafayette, Indiana 47907. "Present address: Poultry Science Department, University of Georgia, Athens, Georgia 30601.
1973
this experiment was to study the flavor differences of wet- and dry-chilled fried chicken as measured by a flavor panel and the gas chromatograph. MATERIALS AND METHODS Trial 1, Commercial broilers were processed at the Hillcrest Poultry processing plant in Lewiston, Maine, by conventional procedures. Just prior to chilling, each bird selected was halved with right and left halves identified. Half of each bird, selected as right and left halves from alternate birds, was allowed to continue through conventional mechanical chilling equipment. These halves were cut-up and packaged after chilling and identified as group A, wetchilled. The opposite half of each bird was cut into primal cuts—breast, wing, back, thigh and drumstick . . . packaged, placed on wire racks in a — 3S°C. blast freezer for 60-70 minutes, and identified as group B, dry-chilled. All packages were then equilibrated in a — 2°C. room until ready for shipment to Lafayette, Indiana. After packaging in fiber boxes, the experimental materials were shipped via auto and plane to Lafayette, arriving in less than ten hours at an internal temperature of less than 4°C. All chicken was then stored at 1°C. until ready for use. All chicken of this trial was dredged in
253
Downloaded from http://ps.oxfordjournals.org/ at Southern Illinois University on June 6, 2015
ABSTRACT Experiments were conducted to determine the effect of wet- and drychilling on fried chicken flavor as measured by a flavor panel and gas chromatographic analysis of the flavor volatiles. Dry-chilling was shown to help produce a fried chicken product with a subtle but detectable flavor advantage over conventionally wet-chilled poultry. Stepwise discriminant analysis of the gas chromatogram of the volatiles from wetand dry-chilled fried chicken indicated that certain ratios from peak areas of the chromtogram quite readily allowed discrimination between the two groups.
254
K. K. HALE, JR., W. J. STADELMAN AND V. D. BRAMBLETT TABLE 1.—Preference score sheet for fried chicken flavor
sented in Table 1. They were next asked to score each sample for natural flavor and off-flavor as depicted in Table 2. Panel evaluations were started on the fourth day after slaughter and continued for ten days. At this point, bacterial spoilage was imminent, so tasting was stopped.
Sample No. Name . Date . 9—Very strongly prefer A 8—Strongly prefer A 7—Prefer A 6—Prefer A slightly 5—No preference 4—Prefer B slightly 3—Prefer B 2—Strongly prefer B 1—Very strongly prefer B
MATERIALS AND METHODS
A student panel of eight regular members and one alternate was selected for this study. Prior to initiation of sample evaluation they were given two days experience evaluating fried chicken of similar differences of that used in this trial. Nine sessions were conducted with the first and second days being exact duplicates to obtain some estimate of error for statistical analy-
TABLE 2.—Score sheet fried chicken flavor Name
C.nAe.
9 Very Full
8
9 None
8
7 Moderately Full 7 Very
Natural Flavor {Fresh Fried) 6 5 4 Slightly FuU 6 Slight
Off-flavor 5 4 Moderate
Slight Describe in one or two words anv off-flavor: General Acceptability 9 8 7 6 5 4 Very Good Fair Good Comments:
2
3
1 Lacking or Masked
3 Pronounced
2
1 Very Pronounced
2
3 Poor
1 Very Poor
Downloaded from http://ps.oxfordjournals.org/ at Southern Illinois University on June 6, 2015
basically a flour-water batter (solids:moisture ratio of 1:1.41) and then breaded in all purpose flour. The breaded pieces were then cooked in cottonseed oil using a P.H.T. pressure deep-fat fryer at 163°C. for 10.5 minutes at 9 p.s.i. Fresh oil was used the first day and after each day's cooking, the oil was filtered and the equipment cleaned. The oil was used a total of six cooking days for three hours each day over a ten day time period. Untrained flavor panel members were asked to evaluate the samples in two ways. First, they were asked to indicate their preference for either A or B sample (randomly assigned to wetand dry-chilled) using the score sheet pre-
Trial 2. Flavor Panel. The broilers for this study were randomly selected from those described by Hale and Stadelman (1972). Cooking of chicken for this study was initiated less than 60 hours after the birds were processed. Frozen samples were thawed in approximately 12 hours in a 4.5°C. cooler. The procedures of Trial 1 were used for breading and cooking the product. Each day fresh cottonseed oil was used for pressure frying.
DRY CHILLING AND FRIED CHICKEN FLAVOR
255
Oa
sis. Order of tasting effect with this product was known to be a significant factor (Hale and Stadelman, 1969) and thus was systematically assigned. Panel members were asked to indicate their preference and to score the cooked meat for the characteristics of fresh fried flavor, off-flavor and general acceptability. Tables 1 and 2 illustrate the panel score sheets. Distillation of Volatiles and Gas Chromatography. Several methods of distillation of flavor volatiles from fried chicken were attempted. The method selected for use in this experiment was the only one found that yielded volatiles in sufficient quantity for analysis and aroma that resembled the odor of fried chicken when in proper dilution with air. It is felt that the distillation procedures used by Pippen and Nonaka (1963) at best represents only boiled chicken and it is quite possible that their long (four hours or more) distillation by boiling, produced artifacts.
It was observed that the steam released during cooking of chicken in the P.H.T. 3 pressure fryer quite closely resembled the odor of the product being fried. To produce a comparable condition with laboratory quantities a four quart pressure cooker was equipped with a tee fitting to allow for the pressure release valve and a needle valve that could be opened (Figure 1). When this valve was opened during the latter stages of pressure frying chicken, the existing steam volatiles bore a remarkable resemblance to those of freshly fried chicken. Chicken parts were prepared as before by dredging in batter and breading in all purpose flour. The coated parts from one half chicken were cooked in cottonseed oil heated to 185°C. by an electric hot plate. The lid to the pressure cooker was immediately sealed and needle valve closed. Tests showed that the temperature of the hot oil 3
A commercial pressure deep-fat cooker using 9 p.s.i. head pressure manufactured by Henry Penny Corporation, Eaton, Ohio.
Downloaded from http://ps.oxfordjournals.org/ at Southern Illinois University on June 6, 2015
FIG. 1. Apparatus for distillation and trapping of fried chicken volatiles.
256
K. K. HALE, JR., W. J. STADELMAN AND V. D. BRAMBLETT
zation detectors. Hydrogen and air necessary for the flame ionization were supplied from cylinders. Several different liquid coatings with various column lengths and percent liquid coatings were tested for ability to separate the flavor volatiles. In particular, Carbowax 20 M, OV-1, OV-17, OV-101 and DEGS were tried. However, a £" X 10' stainless steel column packed with 12 percent FFAP on Chromasorb W (HMDS treated) 60/80 mesh gave the best results. The following are the operating conditions for the gas chromatograph: Na flow Air flow H2 flow Injector temperature Detector temperature Oven temperature
30 ml./minute 300 ml./minute 25 ml./minute 1S0°C. 200°C. Manually programmed from 60°C. to 160°C. at a programmer setting of 60 (essentially linear at 10°C./min.
Stepwise Discriminant Analysis. Stepwise discriminant analysis of gas chromatographic data as outlined by Powers and Keith (1968) was used to determine differences between the chromatograms of wetchilled and dry-chilled chicken. However, before the BMD-7M program (Dixon, 1965) could be used, another program was written to compute the ratios of the gas chromatographic peaks to each other (Table 6). This ratio program gives a print-out of the ratios computed and punches 10 ratios to a computer card. The program was written in such a way that reciprocal ratios were not computed. The input requirements of the ratios program, as written, require at least two cards for each chromatogram. The first card identifies the chromatogram and gives the number of peaks from which ratios are to be formed. The second and subsequent cards
Downloaded from http://ps.oxfordjournals.org/ at Southern Illinois University on June 6, 2015
immediately dropped to 150°C. During the next ten minutes of cooking, the temperature did rise to approximately 170°C. Intermittently during cooking, the needle valve was fully opened to expell any accumulation of distillates from the valve assembly. Pressure was maintained at 9 p.s.i. during cooking by the release valve. After ten minutes of cooking the heat was shut off and the needle valve opened into two glass vacuum traps in series in an ice water bath. The steam pressure was regulated so that over 95 percent of the steam was condensed by the first cold trap. The second cold trap collected less than five percent of the total volatiles collected. After five minutes of collection of condensate the cold traps were disconnected from the valve assembly and the contents of both traps poured into a rubber stoppered jar. Ten ml. of anhydrous diethyl ether was then mixed with the steam condensate by shaking for 30 seconds. The mixture was poured into a 125 ml. separatory funnel and layers allowed to form. The bottom layer of water was then drawn off and discarded. The remaining ether-water interface and ether layer were then chilled at — 23°C. This froze any water in the mixture/solution and thus the ether plus extract could be poured into a clean dry vial. Gas chromatographic tests of a second ether extraction indicated that one extraction with ether yielded approximately 90 percent of the ether extractable volatiles from the steam condensates. Volatiles of the first extraction were of sufficient concentration for GC analysis and thus subsequent extraction of the steam condensate was not deemed practical. Gas chromatography in this study was performed on an Aerograph 204 (VarianAerograph, Walnut Creek, California) with dual columns and independent flame ioni-
257
DRY CHILLING AND FRIED CHICKEN FLAVOR TABLE 3.—Analysis of variance for preference tests in Trial 1 Source
df
SS
TABLE 4.—Average panel scores for preference tests in Trial 1
MS
Main effects 1 4.2463 4.2463 1.28 Average preference 1 4.2463 4.2463 1.28 Order effects 1 15.4719 15.4719 4.65* Means 2 19.7183 9.8592 2.97 Error 112 372.2817 3.3239 * Significant at the 0.05 level of probability.
RESULTS
Trial 1. The data from 114 individual preference tests were analyzed utilizing the analysis of variance for paired comparisons according to Scheffe (1952). The analysis of variance data (Table 3) indicated that there was no statistical difference between the two chilling methods. However, a significant (P < 0.05) order of testing effect was noted. The means presented in Table 4 lend credence to this order effect. The rigor of the Scheffe test is demonstrated by the significant t-value when dry-chilled birds were evaluated first. When the data from the natural flavor scores were analyzed, the method of chill-
first first
Calculated2 t-value
5.201 4.404
0.803 2.108
1 A preference score below 5.000 indicates a preference for dry-chilled. 2 t(0.05, 11 df) = 1.786, H 0 ; M = 5.0.
ing did prove to be of statistical significance (Table 5). The significant order of tasting by chilling method interaction confirms the order effect noted for the preference data. The mean natural flavor scores indicated that dry-chilling significantly improved the flavor of fried chicken. The analysis of off-flavor scores revealed that neither product produced a detectable, consistent off-flavor. Trial 2. Flavor Panel. When the data from 256 preference tests were analyzed using the paired comparisons procedure of Scheffe (1952), a highly significant (P < 0.01) preference for dry-chilled fried chicken was indicated. A significant order of tasting effect like that found in Trial 1 is evidenced by the preference scores given in TABLE 5.—Analysis of variance and significant means for natural flavor in Trial 1 Analysis of Variance Source df
SS
MS
.0507 .0507 Order of tasting (0) 1 Error " a " 22 25.1905 1.1450 Chilling (C) 1 3.3496 3.3496 OxC 1 3.5317 3.5317 .5750 Error " b " 22 12.6494 Total 47 44.7719
<1 5.825* 6.142*
Significant Means** Chilling Wet-chilled 6.002a Dry-chilled 6.530b Sy=.155 * Significant at the 0.05 level of probability. ** Means with different letters differ statistically, at the 0.05 level of probability.
Downloaded from http://ps.oxfordjournals.org/ at Southern Illinois University on June 6, 2015
give the peak areas, limited by this program to a four digit input field. When n = number of peaks, the number of ratios generated equals n(n — l ) / 2 . Thus, for 13 peaks 13(12)/2 = 78 ratios would be generated and eight data cards would be punched. Any peak ratio of less than 0.001 was given a value of 0.001 because of punch output limitations. Generally, ratios less than 0.001 were generated only when very small values were inserted for missing peaks in the chromatogram. Other statistical analyses were conducted using the BMD-2V program (Dixon, 1965). The Student-Newman-Keuls test as outlined by Steel and Torrie (1960) was used to determine significant differences between treatment means.
Tasted wet-chilled Tasted dry-chilled
Average1 Panel score
258
K. K. HALE, JR., W. J. STADELMAN AND V. D. BRAMBLETT T A B I E 6.—Ratios program for gas
chromatographic data
K = 10 L= l IF(K.GT.M.)K=M PUNCH 202,N$L,(Y(I),I=J,K) 202 FORMAT(212,10F7.0) IF(K.GE.M) GO TO 50 J=J+10 K=K+10 L=L-+-1 GO TO 20 60 STOP END 20
Table 7. As before, when the dry-chilled product was tested first, a rather strong preference for the dry-chilled was indicated. However, when the wet-chilled was tasted first, essentially no difference was indicated. The other characteristics evaluated by the taste panel also indicated that drychilling was preferred (Table 8). The only characteristic showing statistical signifi-
Flavor Volatiles. Figures 2 and 3 illustrate the close resemblance of the chromatograms from dry-chilled and wet-chilled fried chicken volatiles. Table 9, which summarized eight chromatograms each from the two chilling processes, further confirms the almost identical relative peak areas of the two groups. It was noted that in all cases the standard deviation for each peak TABLE 8.—Marginal means of taste panel scores for
natural flavor, of-flavor and general acceptability in Trial Z Means*1 Factor
Analysis of variance Source Main effects Averagepref. Orders effects Means Error *p<0.05 **p<0.01
df
SS
MS
1 1 1 2 254
18.05910 18.05910 10.57190 28.53100 653.36900
18.0591 10.0591 10.5719 14.3155 2.5723
7.020** 7.020** 4.110* 5.565**
Means of Preference Scores Tasted dry-chilled first Tasted wet-chilled first 5.47 5.0625 N.B. A preference score above 5.00 indicated a preference for dry-chilled.
Natural flavor 6.129 6.103
Offflavor 8.170 8.167
General acceptability 214 185
Sex
Male Female
Chilling
Wet Dry
6.026 6.206
8.135 8.202
090 308*
Pseudofactor C
ci
6.192 6.039
8.200 8.137
239 170
Packaging
Whole Cut-up
6.167 6.065
8.180 8.160
289 109
6.048 6.183
8.214 8.124
097 301
6.024 6.208
8.093 8.244
164 235
TABLE 7.—Analysis of variance and means for
preference tests in Trial 2
Level
Pseudofactor E Temperature
Fresh Frozen Sy =
.076
* Means were statistically different at the 0.05 level of probability. ** Refer to Table 2 for elucidation of flavor scores.
Downloaded from http://ps.oxfordjournals.org/ at Southern Illinois University on June 6, 2015
DIMENSION X (100),Y(300),Z(300) 50 READ(5,100)N,NM,(X(I),I = 1,NM) 100 FORMAT(213/(20F4.2)) IF(EOF,5)60,12 12 K = 2 M=0 MN=NM-1 WRITE(6,105)N 105 F0RMAT(1H1,3X*CHROMATOGRAM =*I3//4X, *VAR I / J RATIO*/) DO 10 1 = 1, MK DO 101.J=K.NM M=M-fl Z(M)=X(I)/X(J) Y(M) =Z(M)*1000 IF(Y(M).GT.1.0) GO TO 210 Y(M) = 1.0 210 CONTINUE WRITE(6,110)M,IJ,Z (M) 110 FORMAT(16,15,*/*I2,F11.4) 101 CONTINUE K=K+1 10 CONTINUE PUNCH 200.N 200 FORMAT(3X$*CHROMATOGRAM NO.*I3)
cance (P < 0.05) was general acceptability, however, the average numerical value of dry-chilled scores was higher for both natural flavor and off-flavor. As expected, the factors of sex, packaging or electrolytes did not seem to have any effect on flavor. Although not statistically significant, the average flavor scores for the frozen birds were higher for all three characteristics. This occurrence was logical since the fresh product had begun to deteriorate microbiologically about ten days after processing. Had flavor evaluation been continued for about three more days, the flavor scores for the fresh product (merely unfrozen by that time) would most probably have been statistically lower.
2S9
DRY CHILLING AND FRIED CHICKEN FLAVOR
4 6 8 10 12 FIG. 2. Gas chromatogram of volatiles of dry-chilled fried chicken.
was too large to allow rejection of the null hypothesis of no difference between individual peaks. One can note from Figures 2 and 3 that
PEAK
I
2
3
I TIME
2
^J
4
I
5
I
I
6
7
I
14
there were a few small peaks which were not numbered. These smaller peaks and others which showed up at a higher attenuation setting were not included in the anal-
8
9 10
I
I
II
I
12
I
I
4 6 8 10 12 FIG. 3. Gas chromatogram of volatiles of wet-chilled fried chicken.
13
l
_ 14
Downloaded from http://ps.oxfordjournals.org/ at Southern Illinois University on June 6, 2015
TIME
260
K. K. HALE, JR., W. J. STADELMAN AND V. D. BRAMBLETT
TABLE 9.—Means and standard deviations of percentage peak area from gas chromalograms of wet- and dry-chilled fried chicken
Peak
Dry-Chilled
Wet-Chilled
% of Total Standard area deviation
% of Total Standard area deviation
2.36 2.52 6.12 .78 7.71 14.68 4.65 1.25 .89 3.27 1.20 11.01 37.52
.479 .298 1.370 .153 3.400 3.282 .611 .302 .364 .431 .530 2.070 5.956
2.37 2.09 4.74 .60 7.04 14.13 5.01 1.30 1.16 3.78 1.31 10.24 38.67
.775 .685 .598 .166 1.675 3.274 .719 .318 2.97 .480 .426 1.601 4.435
ysis. In addition, the unresolved peak occurring with peak 7 appeared intermittently in the two chilling groups and was not considered as part of the analysis of the 13 major peaks. Stepwise Discriminant Analysis. Table 10 lists by steps the number of cases in each group correctly classified by the stepwide program. It is noteworthy that only one variable was required to obtain correct classification for all but two of the chromaTABLE 10.—Classification of wet- and dry-chilled broilers by step-wise discriminant analysis Predicted group Dry
Wet
Step 1 Dry Wet
7 1 Step 2
1 7
Dry Wet
7 2 Step 3
1 6
Dry Wet
8 0 Step 4
0 8
Dry Wet
7 0 Step 5
1 8
DISCUSSION The flavor panel results of Trial 1 indicated that the natural fresh fried chicken flavor of dry-chilled poultry was more intense. However, the analysis of the preference tests by the procedures of Scheffe (1952) did not allow rejection of the null hypothesis of no difference between the two chilling treatments. The analysis revealed a significant order of tasting effect. TABLE 11.—Summary of stepwise discriminant analysis of data from wet- and dry-chilled chicken
ratio
F value to enter or remove
U-statistic
3/10 11/13 5/07 9/12 3/05
11.3451 2.6489 9.0064 1.7752 1.1850
.5524 .4589 .2621 .2257 .2018
i7„-:„ui Variable entered
Peaks used
Step 1 2 3 4 5
30 77 44 71 25
t0 form
TABLE 12.—Mean ratios of gas chromatographic peaks from wet- and dry-chilled cooked chicken Step no. Peak ratio
Dry Wet
1 2 3 4 5
3/10 11/13 5/07 9/12 3/05
Dry
Wet
1.88090 .03262 1.63640 .08075 .05850
1.28110 .03475 1.43050 .11737 .69610
Downloaded from http://ps.oxfordjournals.org/ at Southern Illinois University on June 6, 2015
1 2 3 4 5 6 7 8 9 10 11 12 13
tograms. After five steps the cases were correctly classified and addition or deletion of more ratios (steps) did not alter the classification. A summary of the analysis is given in Table 11. It was noted that as the number of steps increased, the "fit" of the classification became more perfect as measured by the U-statistic (Rao, 1952). Table 12 displays the mean ratios of the ratios that did the best job of discriminating. Generally the ratios greater than or approximately equal to unity were highest for the drychilled. The ratios considerably less than one (which would be ratios of small to large peaks) were greater for the wetchilled product.
DRY CHILLING AND FRIED CHICKEN FLAVOR
This difference in flavor between wetand dry-chilled poultry is probably due to a leaching of flavor precursors during the wet-chilling process. Pippen et al. (1954) showed that broth from chicken immersed in ice water for as little as five hours had less flavor than broth from unsoaked halves. Pippen and Klose (195S) indicated that the neutral ash of the substances extracted during ice water soaking of chicken considerably restored lost flavor when reincorporated into broth preparations. The gas chromatographic data of Trial 2 revealed that the two chilling methods yielded volatiles in seemingly equal proportions when analyzed by standard methods. However, when the stepwise descriminate analysis technique outlined by Powers (1968) was used, the two chilling groups could be separated after only five steps by the program. A summary of the mean ratios of the gas chromatographic peaks from the two chilling groups indicated that the peak ratios with greatest discriminating powers were of higher value from the dry-
chilled product when the ratios were greater than or approximately equal to unity (which would normally be the ratio of a large over a small peak). The ratios considerably less than unity (which would be ratios of small to large peaks) were smaller in value for the dry-chilled product. This would generally indicate that the large peaks associated with the most discriminating ratios were largest with the product of greatest natural intensity, drychilled. Significant insight into the chemical reasons behind a more intense fried chicken flavor might be gained from a study of chicken treated with the compounds associated with the most discriminating ratios. REFERENCES Dixon, W. J., 1965. Biomedical computer program. Health Sciences Computing Facility, Dept. of Preventive Medicine and Public Health, School of Medicine, University of California, Los Angeles, California. Hale, K. K., Jr., and W. J. Stadelman, 1972. Effects of electrolyte treatments and dry-chilling on yields and tenderness of broilers. Poultry Sci. 5 1 : 244-252. Hale, K. K., Jr., and W. J. Stadelman, 1969. Flavor differences between wet-chilled and drychilled broilers. Poultry Sci. 48: 1814-1815. May, K. N., R. L. Helmer and R. L. Saffle, 1963. Effect of phosphate treatment on carcass-weight changes and organoleptic quality of cut-up chicken. Poultry Sci. 42: 24-32. Kotula, A. W., J. E. Thomson and J. A. Kenner, 1960. Water absorption by eviscerated broilers during washing and chilling, U. S. Dept. Agr. Mktg. Res. Report No. 438. Pippen, E. L., A. A. Campbell and I. V. Streeter, 1954. Flavor studies: Origin of chicken flavor. J. Agr. Food Chem. 2 : 364-367. Pippen, E. L., and A. A. Klose, 1955. Effects of ice water chilling on flavor of chicken. Poultry Sci. 34: 1139-1146. Pippen, E. L., and M. Nonaka, 1963. Gas chromatography of chicken and turkey volatiles: The effect of temperature, oxygen and type of tissues on composition of the volatile fraction. J. Food Sci. 28:334-341. Powers, J. J., 1968. Toward objective evaluation
Downloaded from http://ps.oxfordjournals.org/ at Southern Illinois University on June 6, 2015
The results in Trial 2 did not indicate a more intense fresh fried flavor but the paired comparisons tests for preference demonstrated that the dry-chilled was preferred by the student panel used in this trial. As in Trial 1 a significant order of tasting effect was noted. It was hypothesized that this order effect is due to the fact that the dry-chilled fried chicken probably contained more of the volatile compounds associated with a "chickeny flavor." When the wet-chilled is tasted first, the flavor of the dry-chilled product probably seemed somewhat foreign to the panel members. When dry-chilled was tasted first, the flavor of the wet-chilled seemed bland in comparison. Thus, the panel members scored dry-chilled higher when it was tasted first. When wet-chilled was tasted first, they were indecisive and average panel scores indicated no difference.
261
262
K. K. HALE, JR., W. J. STADELMAN AND V. D. BRAMBLETT
of food flavor. Food Technol. 22: 383-388. Powers, J. J., and E. S. Keith, 1968. Stepwise discriminant analysis of gas chromatographic data as an aid in classifying the flavor quality of foods. J. Food Sci. 33: 207-213. Rao, C. R., 19S2. Tests of significance in multivariate analysis. In Advanced Statistical Methods in Biometric Research. John Wiley and Sons, Inc., New York.
Scheffe, H., 1952. An analysis of variance for paired comparisons. J. Am. Statistical Assoc. 7: 381-400. Steel, R. G. D., and J. H. Torrie, 1960. Principles and Procedures of Statistics. McGraw-Hill Book Company, Inc., New York. Stevens, A., 1970. Chilling equipment must go, Hillcrest's Stevens insists. Broiler Industry, 33(3): S3.
J. W. DEATON, 1 F. N. REECE, 2 L. F. KUBENA, 1 B. D. LOTT 1 AND J. D. MAY 1 United States Department of Agriculture, A.R.S., State College, Mississippi 39762 (Received for publication May 1, 1972)
ABSTRACT Previous work at this laboratory demonstrated that broiler chicks could compensate by market age from early growth depression when reduced brooding temperature was the deterrent. Lott (1971) demonstrated diets which depressed broiler body weight at 4 weeks of age. The major diet differences were dietary energy levels. In an attempt to determine if the compensatory ability phenomenon could be utilized in broiler diet formulations for possible economic gain, 3 trials utilizing a total of 2,736 commercial broiler chickens were conducted. Results obtained showed that birds fed a diet containing 3141 kcal. of M.E.Ag- had a 4% reduction in body weight at 4 weeks of age, as compared to birds fed a diet containing 3306 kcal. of M.E./kg. By 8 weeks of age the males were able to compensate for the 4% reduction in 4-week body weight when fed a high-energy diet containing 3372 kcal. of M.E.Ag- Females could compensate for the 4% reduction in 4-week weight by 8 weeks of age when fed diets containing either 3207 or 3372 kcal. of M.E./kg. The percentage ether extract of the carcass at market age increased, however, for the groups demonstrating compensatory weight gain ability. Feed required per unit of gain increased as energy content of diet combinations decreased. POULTRY SCIENCE 52:
INTRODUCTION
P
REVIOUS work at this laboratory (Reece and Deaton, 1968) demonstrated that when body weights for broiler chicks brooded with reduced heat were not more than 13% lower at 3 weeks than those conventionally brooded, the bodyweight differences were eliminated by 8 weeks of age. Between 3 and 8 weeks, all birds were reared in one group. Lott 1 Animal Science Research Division, Poultry Research Branch, South Central Poultry Research Laboratory, State College, Mississippi. 2 Agricultural Engineering Research Division, Farm Electrification Research Branch, South Central Poultry Research Laboratory, State College, Mississippi.
262-265,
1973
(1971) demonstrated diets which depressed broiler body weight at 4 weeks of age. The major diet differences were dietary energy levels. In an attempt to determine if the compensatory ability phenomenon could be utilized in broiler diet formulations for possible economic advantage, the following study was conducted. EXPERIMENTAL PROCEDURE
Three trials utilizing a total of 2,736 commercial broiler chickens were conducted. For each trial, 12 1.51- by 3.7-meter pens were used with 38 male and 38 female broiler chicks placed per pen. The
Downloaded from http://ps.oxfordjournals.org/ at Southern Illinois University on June 6, 2015
The Ability of the Broiler Chicken to Compensate for Early Growth Depression
Departments of Animal Sciences and Home Economics, Agricultural Experiment Station, Purdue University, Lafayette, Indiana 47907 (Received for publication May 1, 1972)
POULTRY SCIENCE 52: 253-262,
INTRODUCTION
C
ONTINUOUS ice-slush has been used over the past two decades as a successful means of rapidly reducing the temperature of freshly eviscerated broiler carcasses while at the same time improving yields by water uptake during the chilling process. The reports of Kotula et al. (1960) and May et al. (1963) have helped to demonstrate that water picked up during ice-slush continuous chilling process is loosely bound and much of it is leached out before the product reaches the consumer. Stevens (1970) noted that using a dry-chill process in lieu of ice-slush helped overcome some of the drip loss and packaged product appearance problems experienced with wetchilling. While conducting some preliminary experiments with dry-chilled poultry, a subtle but consistent flavor difference between wet- and dry-chilled products was noted. These results were consistent with those of Pippen and Klose (19SS) who found that broth prepared from chicken immersed in ice water for as little as three hours had significantly less flavor than broth from unsoaked birds. The primary purpose of "Journal Paper No. 4727 Purdue Agricultural Experiment Station, Lafayette, Indiana 47907. "Present address: Poultry Science Department, University of Georgia, Athens, Georgia 30601.
1973
this experiment was to study the flavor differences of wet- and dry-chilled fried chicken as measured by a flavor panel and the gas chromatograph. MATERIALS AND METHODS Trial 1, Commercial broilers were processed at the Hillcrest Poultry processing plant in Lewiston, Maine, by conventional procedures. Just prior to chilling, each bird selected was halved with right and left halves identified. Half of each bird, selected as right and left halves from alternate birds, was allowed to continue through conventional mechanical chilling equipment. These halves were cut-up and packaged after chilling and identified as group A, wetchilled. The opposite half of each bird was cut into primal cuts—breast, wing, back, thigh and drumstick . . . packaged, placed on wire racks in a — 3S°C. blast freezer for 60-70 minutes, and identified as group B, dry-chilled. All packages were then equilibrated in a — 2°C. room until ready for shipment to Lafayette, Indiana. After packaging in fiber boxes, the experimental materials were shipped via auto and plane to Lafayette, arriving in less than ten hours at an internal temperature of less than 4°C. All chicken was then stored at 1°C. until ready for use. All chicken of this trial was dredged in
253
Downloaded from http://ps.oxfordjournals.org/ at Southern Illinois University on June 6, 2015
ABSTRACT Experiments were conducted to determine the effect of wet- and drychilling on fried chicken flavor as measured by a flavor panel and gas chromatographic analysis of the flavor volatiles. Dry-chilling was shown to help produce a fried chicken product with a subtle but detectable flavor advantage over conventionally wet-chilled poultry. Stepwise discriminant analysis of the gas chromatogram of the volatiles from wetand dry-chilled fried chicken indicated that certain ratios from peak areas of the chromtogram quite readily allowed discrimination between the two groups.
254
K. K. HALE, JR., W. J. STADELMAN AND V. D. BRAMBLETT TABLE 1.—Preference score sheet for fried chicken flavor
sented in Table 1. They were next asked to score each sample for natural flavor and off-flavor as depicted in Table 2. Panel evaluations were started on the fourth day after slaughter and continued for ten days. At this point, bacterial spoilage was imminent, so tasting was stopped.
Sample No. Name . Date . 9—Very strongly prefer A 8—Strongly prefer A 7—Prefer A 6—Prefer A slightly 5—No preference 4—Prefer B slightly 3—Prefer B 2—Strongly prefer B 1—Very strongly prefer B
MATERIALS AND METHODS
A student panel of eight regular members and one alternate was selected for this study. Prior to initiation of sample evaluation they were given two days experience evaluating fried chicken of similar differences of that used in this trial. Nine sessions were conducted with the first and second days being exact duplicates to obtain some estimate of error for statistical analy-
TABLE 2.—Score sheet fried chicken flavor Name
C.nAe.
9 Very Full
8
9 None
8
7 Moderately Full 7 Very
Natural Flavor {Fresh Fried) 6 5 4 Slightly FuU 6 Slight
Off-flavor 5 4 Moderate
Slight Describe in one or two words anv off-flavor: General Acceptability 9 8 7 6 5 4 Very Good Fair Good Comments:
2
3
1 Lacking or Masked
3 Pronounced
2
1 Very Pronounced
2
3 Poor
1 Very Poor
Downloaded from http://ps.oxfordjournals.org/ at Southern Illinois University on June 6, 2015
basically a flour-water batter (solids:moisture ratio of 1:1.41) and then breaded in all purpose flour. The breaded pieces were then cooked in cottonseed oil using a P.H.T. pressure deep-fat fryer at 163°C. for 10.5 minutes at 9 p.s.i. Fresh oil was used the first day and after each day's cooking, the oil was filtered and the equipment cleaned. The oil was used a total of six cooking days for three hours each day over a ten day time period. Untrained flavor panel members were asked to evaluate the samples in two ways. First, they were asked to indicate their preference for either A or B sample (randomly assigned to wetand dry-chilled) using the score sheet pre-
Trial 2. Flavor Panel. The broilers for this study were randomly selected from those described by Hale and Stadelman (1972). Cooking of chicken for this study was initiated less than 60 hours after the birds were processed. Frozen samples were thawed in approximately 12 hours in a 4.5°C. cooler. The procedures of Trial 1 were used for breading and cooking the product. Each day fresh cottonseed oil was used for pressure frying.
DRY CHILLING AND FRIED CHICKEN FLAVOR
255
Oa
sis. Order of tasting effect with this product was known to be a significant factor (Hale and Stadelman, 1969) and thus was systematically assigned. Panel members were asked to indicate their preference and to score the cooked meat for the characteristics of fresh fried flavor, off-flavor and general acceptability. Tables 1 and 2 illustrate the panel score sheets. Distillation of Volatiles and Gas Chromatography. Several methods of distillation of flavor volatiles from fried chicken were attempted. The method selected for use in this experiment was the only one found that yielded volatiles in sufficient quantity for analysis and aroma that resembled the odor of fried chicken when in proper dilution with air. It is felt that the distillation procedures used by Pippen and Nonaka (1963) at best represents only boiled chicken and it is quite possible that their long (four hours or more) distillation by boiling, produced artifacts.
It was observed that the steam released during cooking of chicken in the P.H.T. 3 pressure fryer quite closely resembled the odor of the product being fried. To produce a comparable condition with laboratory quantities a four quart pressure cooker was equipped with a tee fitting to allow for the pressure release valve and a needle valve that could be opened (Figure 1). When this valve was opened during the latter stages of pressure frying chicken, the existing steam volatiles bore a remarkable resemblance to those of freshly fried chicken. Chicken parts were prepared as before by dredging in batter and breading in all purpose flour. The coated parts from one half chicken were cooked in cottonseed oil heated to 185°C. by an electric hot plate. The lid to the pressure cooker was immediately sealed and needle valve closed. Tests showed that the temperature of the hot oil 3
A commercial pressure deep-fat cooker using 9 p.s.i. head pressure manufactured by Henry Penny Corporation, Eaton, Ohio.
Downloaded from http://ps.oxfordjournals.org/ at Southern Illinois University on June 6, 2015
FIG. 1. Apparatus for distillation and trapping of fried chicken volatiles.
256
K. K. HALE, JR., W. J. STADELMAN AND V. D. BRAMBLETT
zation detectors. Hydrogen and air necessary for the flame ionization were supplied from cylinders. Several different liquid coatings with various column lengths and percent liquid coatings were tested for ability to separate the flavor volatiles. In particular, Carbowax 20 M, OV-1, OV-17, OV-101 and DEGS were tried. However, a £" X 10' stainless steel column packed with 12 percent FFAP on Chromasorb W (HMDS treated) 60/80 mesh gave the best results. The following are the operating conditions for the gas chromatograph: Na flow Air flow H2 flow Injector temperature Detector temperature Oven temperature
30 ml./minute 300 ml./minute 25 ml./minute 1S0°C. 200°C. Manually programmed from 60°C. to 160°C. at a programmer setting of 60 (essentially linear at 10°C./min.
Stepwise Discriminant Analysis. Stepwise discriminant analysis of gas chromatographic data as outlined by Powers and Keith (1968) was used to determine differences between the chromatograms of wetchilled and dry-chilled chicken. However, before the BMD-7M program (Dixon, 1965) could be used, another program was written to compute the ratios of the gas chromatographic peaks to each other (Table 6). This ratio program gives a print-out of the ratios computed and punches 10 ratios to a computer card. The program was written in such a way that reciprocal ratios were not computed. The input requirements of the ratios program, as written, require at least two cards for each chromatogram. The first card identifies the chromatogram and gives the number of peaks from which ratios are to be formed. The second and subsequent cards
Downloaded from http://ps.oxfordjournals.org/ at Southern Illinois University on June 6, 2015
immediately dropped to 150°C. During the next ten minutes of cooking, the temperature did rise to approximately 170°C. Intermittently during cooking, the needle valve was fully opened to expell any accumulation of distillates from the valve assembly. Pressure was maintained at 9 p.s.i. during cooking by the release valve. After ten minutes of cooking the heat was shut off and the needle valve opened into two glass vacuum traps in series in an ice water bath. The steam pressure was regulated so that over 95 percent of the steam was condensed by the first cold trap. The second cold trap collected less than five percent of the total volatiles collected. After five minutes of collection of condensate the cold traps were disconnected from the valve assembly and the contents of both traps poured into a rubber stoppered jar. Ten ml. of anhydrous diethyl ether was then mixed with the steam condensate by shaking for 30 seconds. The mixture was poured into a 125 ml. separatory funnel and layers allowed to form. The bottom layer of water was then drawn off and discarded. The remaining ether-water interface and ether layer were then chilled at — 23°C. This froze any water in the mixture/solution and thus the ether plus extract could be poured into a clean dry vial. Gas chromatographic tests of a second ether extraction indicated that one extraction with ether yielded approximately 90 percent of the ether extractable volatiles from the steam condensates. Volatiles of the first extraction were of sufficient concentration for GC analysis and thus subsequent extraction of the steam condensate was not deemed practical. Gas chromatography in this study was performed on an Aerograph 204 (VarianAerograph, Walnut Creek, California) with dual columns and independent flame ioni-
257
DRY CHILLING AND FRIED CHICKEN FLAVOR TABLE 3.—Analysis of variance for preference tests in Trial 1 Source
df
SS
TABLE 4.—Average panel scores for preference tests in Trial 1
MS
Main effects 1 4.2463 4.2463 1.28 Average preference 1 4.2463 4.2463 1.28 Order effects 1 15.4719 15.4719 4.65* Means 2 19.7183 9.8592 2.97 Error 112 372.2817 3.3239 * Significant at the 0.05 level of probability.
RESULTS
Trial 1. The data from 114 individual preference tests were analyzed utilizing the analysis of variance for paired comparisons according to Scheffe (1952). The analysis of variance data (Table 3) indicated that there was no statistical difference between the two chilling methods. However, a significant (P < 0.05) order of testing effect was noted. The means presented in Table 4 lend credence to this order effect. The rigor of the Scheffe test is demonstrated by the significant t-value when dry-chilled birds were evaluated first. When the data from the natural flavor scores were analyzed, the method of chill-
first first
Calculated2 t-value
5.201 4.404
0.803 2.108
1 A preference score below 5.000 indicates a preference for dry-chilled. 2 t(0.05, 11 df) = 1.786, H 0 ; M = 5.0.
ing did prove to be of statistical significance (Table 5). The significant order of tasting by chilling method interaction confirms the order effect noted for the preference data. The mean natural flavor scores indicated that dry-chilling significantly improved the flavor of fried chicken. The analysis of off-flavor scores revealed that neither product produced a detectable, consistent off-flavor. Trial 2. Flavor Panel. When the data from 256 preference tests were analyzed using the paired comparisons procedure of Scheffe (1952), a highly significant (P < 0.01) preference for dry-chilled fried chicken was indicated. A significant order of tasting effect like that found in Trial 1 is evidenced by the preference scores given in TABLE 5.—Analysis of variance and significant means for natural flavor in Trial 1 Analysis of Variance Source df
SS
MS
.0507 .0507 Order of tasting (0) 1 Error " a " 22 25.1905 1.1450 Chilling (C) 1 3.3496 3.3496 OxC 1 3.5317 3.5317 .5750 Error " b " 22 12.6494 Total 47 44.7719
<1 5.825* 6.142*
Significant Means** Chilling Wet-chilled 6.002a Dry-chilled 6.530b Sy=.155 * Significant at the 0.05 level of probability. ** Means with different letters differ statistically, at the 0.05 level of probability.
Downloaded from http://ps.oxfordjournals.org/ at Southern Illinois University on June 6, 2015
give the peak areas, limited by this program to a four digit input field. When n = number of peaks, the number of ratios generated equals n(n — l ) / 2 . Thus, for 13 peaks 13(12)/2 = 78 ratios would be generated and eight data cards would be punched. Any peak ratio of less than 0.001 was given a value of 0.001 because of punch output limitations. Generally, ratios less than 0.001 were generated only when very small values were inserted for missing peaks in the chromatogram. Other statistical analyses were conducted using the BMD-2V program (Dixon, 1965). The Student-Newman-Keuls test as outlined by Steel and Torrie (1960) was used to determine significant differences between treatment means.
Tasted wet-chilled Tasted dry-chilled
Average1 Panel score
258
K. K. HALE, JR., W. J. STADELMAN AND V. D. BRAMBLETT T A B I E 6.—Ratios program for gas
chromatographic data
K = 10 L= l IF(K.GT.M.)K=M PUNCH 202,N$L,(Y(I),I=J,K) 202 FORMAT(212,10F7.0) IF(K.GE.M) GO TO 50 J=J+10 K=K+10 L=L-+-1 GO TO 20 60 STOP END 20
Table 7. As before, when the dry-chilled product was tested first, a rather strong preference for the dry-chilled was indicated. However, when the wet-chilled was tasted first, essentially no difference was indicated. The other characteristics evaluated by the taste panel also indicated that drychilling was preferred (Table 8). The only characteristic showing statistical signifi-
Flavor Volatiles. Figures 2 and 3 illustrate the close resemblance of the chromatograms from dry-chilled and wet-chilled fried chicken volatiles. Table 9, which summarized eight chromatograms each from the two chilling processes, further confirms the almost identical relative peak areas of the two groups. It was noted that in all cases the standard deviation for each peak TABLE 8.—Marginal means of taste panel scores for
natural flavor, of-flavor and general acceptability in Trial Z Means*1 Factor
Analysis of variance Source Main effects Averagepref. Orders effects Means Error *p<0.05 **p<0.01
df
SS
MS
1 1 1 2 254
18.05910 18.05910 10.57190 28.53100 653.36900
18.0591 10.0591 10.5719 14.3155 2.5723
7.020** 7.020** 4.110* 5.565**
Means of Preference Scores Tasted dry-chilled first Tasted wet-chilled first 5.47 5.0625 N.B. A preference score above 5.00 indicated a preference for dry-chilled.
Natural flavor 6.129 6.103
Offflavor 8.170 8.167
General acceptability 214 185
Sex
Male Female
Chilling
Wet Dry
6.026 6.206
8.135 8.202
090 308*
Pseudofactor C
ci
6.192 6.039
8.200 8.137
239 170
Packaging
Whole Cut-up
6.167 6.065
8.180 8.160
289 109
6.048 6.183
8.214 8.124
097 301
6.024 6.208
8.093 8.244
164 235
TABLE 7.—Analysis of variance and means for
preference tests in Trial 2
Level
Pseudofactor E Temperature
Fresh Frozen Sy =
.076
* Means were statistically different at the 0.05 level of probability. ** Refer to Table 2 for elucidation of flavor scores.
Downloaded from http://ps.oxfordjournals.org/ at Southern Illinois University on June 6, 2015
DIMENSION X (100),Y(300),Z(300) 50 READ(5,100)N,NM,(X(I),I = 1,NM) 100 FORMAT(213/(20F4.2)) IF(EOF,5)60,12 12 K = 2 M=0 MN=NM-1 WRITE(6,105)N 105 F0RMAT(1H1,3X*CHROMATOGRAM =*I3//4X, *VAR I / J RATIO*/) DO 10 1 = 1, MK DO 101.J=K.NM M=M-fl Z(M)=X(I)/X(J) Y(M) =Z(M)*1000 IF(Y(M).GT.1.0) GO TO 210 Y(M) = 1.0 210 CONTINUE WRITE(6,110)M,IJ,Z (M) 110 FORMAT(16,15,*/*I2,F11.4) 101 CONTINUE K=K+1 10 CONTINUE PUNCH 200.N 200 FORMAT(3X$*CHROMATOGRAM NO.*I3)
cance (P < 0.05) was general acceptability, however, the average numerical value of dry-chilled scores was higher for both natural flavor and off-flavor. As expected, the factors of sex, packaging or electrolytes did not seem to have any effect on flavor. Although not statistically significant, the average flavor scores for the frozen birds were higher for all three characteristics. This occurrence was logical since the fresh product had begun to deteriorate microbiologically about ten days after processing. Had flavor evaluation been continued for about three more days, the flavor scores for the fresh product (merely unfrozen by that time) would most probably have been statistically lower.
2S9
DRY CHILLING AND FRIED CHICKEN FLAVOR
4 6 8 10 12 FIG. 2. Gas chromatogram of volatiles of dry-chilled fried chicken.
was too large to allow rejection of the null hypothesis of no difference between individual peaks. One can note from Figures 2 and 3 that
PEAK
I
2
3
I TIME
2
^J
4
I
5
I
I
6
7
I
14
there were a few small peaks which were not numbered. These smaller peaks and others which showed up at a higher attenuation setting were not included in the anal-
8
9 10
I
I
II
I
12
I
I
4 6 8 10 12 FIG. 3. Gas chromatogram of volatiles of wet-chilled fried chicken.
13
l
_ 14
Downloaded from http://ps.oxfordjournals.org/ at Southern Illinois University on June 6, 2015
TIME
260
K. K. HALE, JR., W. J. STADELMAN AND V. D. BRAMBLETT
TABLE 9.—Means and standard deviations of percentage peak area from gas chromalograms of wet- and dry-chilled fried chicken
Peak
Dry-Chilled
Wet-Chilled
% of Total Standard area deviation
% of Total Standard area deviation
2.36 2.52 6.12 .78 7.71 14.68 4.65 1.25 .89 3.27 1.20 11.01 37.52
.479 .298 1.370 .153 3.400 3.282 .611 .302 .364 .431 .530 2.070 5.956
2.37 2.09 4.74 .60 7.04 14.13 5.01 1.30 1.16 3.78 1.31 10.24 38.67
.775 .685 .598 .166 1.675 3.274 .719 .318 2.97 .480 .426 1.601 4.435
ysis. In addition, the unresolved peak occurring with peak 7 appeared intermittently in the two chilling groups and was not considered as part of the analysis of the 13 major peaks. Stepwise Discriminant Analysis. Table 10 lists by steps the number of cases in each group correctly classified by the stepwide program. It is noteworthy that only one variable was required to obtain correct classification for all but two of the chromaTABLE 10.—Classification of wet- and dry-chilled broilers by step-wise discriminant analysis Predicted group Dry
Wet
Step 1 Dry Wet
7 1 Step 2
1 7
Dry Wet
7 2 Step 3
1 6
Dry Wet
8 0 Step 4
0 8
Dry Wet
7 0 Step 5
1 8
DISCUSSION The flavor panel results of Trial 1 indicated that the natural fresh fried chicken flavor of dry-chilled poultry was more intense. However, the analysis of the preference tests by the procedures of Scheffe (1952) did not allow rejection of the null hypothesis of no difference between the two chilling treatments. The analysis revealed a significant order of tasting effect. TABLE 11.—Summary of stepwise discriminant analysis of data from wet- and dry-chilled chicken
ratio
F value to enter or remove
U-statistic
3/10 11/13 5/07 9/12 3/05
11.3451 2.6489 9.0064 1.7752 1.1850
.5524 .4589 .2621 .2257 .2018
i7„-:„ui Variable entered
Peaks used
Step 1 2 3 4 5
30 77 44 71 25
t0 form
TABLE 12.—Mean ratios of gas chromatographic peaks from wet- and dry-chilled cooked chicken Step no. Peak ratio
Dry Wet
1 2 3 4 5
3/10 11/13 5/07 9/12 3/05
Dry
Wet
1.88090 .03262 1.63640 .08075 .05850
1.28110 .03475 1.43050 .11737 .69610
Downloaded from http://ps.oxfordjournals.org/ at Southern Illinois University on June 6, 2015
1 2 3 4 5 6 7 8 9 10 11 12 13
tograms. After five steps the cases were correctly classified and addition or deletion of more ratios (steps) did not alter the classification. A summary of the analysis is given in Table 11. It was noted that as the number of steps increased, the "fit" of the classification became more perfect as measured by the U-statistic (Rao, 1952). Table 12 displays the mean ratios of the ratios that did the best job of discriminating. Generally the ratios greater than or approximately equal to unity were highest for the drychilled. The ratios considerably less than one (which would be ratios of small to large peaks) were greater for the wetchilled product.
DRY CHILLING AND FRIED CHICKEN FLAVOR
This difference in flavor between wetand dry-chilled poultry is probably due to a leaching of flavor precursors during the wet-chilling process. Pippen et al. (1954) showed that broth from chicken immersed in ice water for as little as five hours had less flavor than broth from unsoaked halves. Pippen and Klose (195S) indicated that the neutral ash of the substances extracted during ice water soaking of chicken considerably restored lost flavor when reincorporated into broth preparations. The gas chromatographic data of Trial 2 revealed that the two chilling methods yielded volatiles in seemingly equal proportions when analyzed by standard methods. However, when the stepwise descriminate analysis technique outlined by Powers (1968) was used, the two chilling groups could be separated after only five steps by the program. A summary of the mean ratios of the gas chromatographic peaks from the two chilling groups indicated that the peak ratios with greatest discriminating powers were of higher value from the dry-
chilled product when the ratios were greater than or approximately equal to unity (which would normally be the ratio of a large over a small peak). The ratios considerably less than unity (which would be ratios of small to large peaks) were smaller in value for the dry-chilled product. This would generally indicate that the large peaks associated with the most discriminating ratios were largest with the product of greatest natural intensity, drychilled. Significant insight into the chemical reasons behind a more intense fried chicken flavor might be gained from a study of chicken treated with the compounds associated with the most discriminating ratios. REFERENCES Dixon, W. J., 1965. Biomedical computer program. Health Sciences Computing Facility, Dept. of Preventive Medicine and Public Health, School of Medicine, University of California, Los Angeles, California. Hale, K. K., Jr., and W. J. Stadelman, 1972. Effects of electrolyte treatments and dry-chilling on yields and tenderness of broilers. Poultry Sci. 5 1 : 244-252. Hale, K. K., Jr., and W. J. Stadelman, 1969. Flavor differences between wet-chilled and drychilled broilers. Poultry Sci. 48: 1814-1815. May, K. N., R. L. Helmer and R. L. Saffle, 1963. Effect of phosphate treatment on carcass-weight changes and organoleptic quality of cut-up chicken. Poultry Sci. 42: 24-32. Kotula, A. W., J. E. Thomson and J. A. Kenner, 1960. Water absorption by eviscerated broilers during washing and chilling, U. S. Dept. Agr. Mktg. Res. Report No. 438. Pippen, E. L., A. A. Campbell and I. V. Streeter, 1954. Flavor studies: Origin of chicken flavor. J. Agr. Food Chem. 2 : 364-367. Pippen, E. L., and A. A. Klose, 1955. Effects of ice water chilling on flavor of chicken. Poultry Sci. 34: 1139-1146. Pippen, E. L., and M. Nonaka, 1963. Gas chromatography of chicken and turkey volatiles: The effect of temperature, oxygen and type of tissues on composition of the volatile fraction. J. Food Sci. 28:334-341. Powers, J. J., 1968. Toward objective evaluation
Downloaded from http://ps.oxfordjournals.org/ at Southern Illinois University on June 6, 2015
The results in Trial 2 did not indicate a more intense fresh fried flavor but the paired comparisons tests for preference demonstrated that the dry-chilled was preferred by the student panel used in this trial. As in Trial 1 a significant order of tasting effect was noted. It was hypothesized that this order effect is due to the fact that the dry-chilled fried chicken probably contained more of the volatile compounds associated with a "chickeny flavor." When the wet-chilled is tasted first, the flavor of the dry-chilled product probably seemed somewhat foreign to the panel members. When dry-chilled was tasted first, the flavor of the wet-chilled seemed bland in comparison. Thus, the panel members scored dry-chilled higher when it was tasted first. When wet-chilled was tasted first, they were indecisive and average panel scores indicated no difference.
261
262
K. K. HALE, JR., W. J. STADELMAN AND V. D. BRAMBLETT
of food flavor. Food Technol. 22: 383-388. Powers, J. J., and E. S. Keith, 1968. Stepwise discriminant analysis of gas chromatographic data as an aid in classifying the flavor quality of foods. J. Food Sci. 33: 207-213. Rao, C. R., 19S2. Tests of significance in multivariate analysis. In Advanced Statistical Methods in Biometric Research. John Wiley and Sons, Inc., New York.
Scheffe, H., 1952. An analysis of variance for paired comparisons. J. Am. Statistical Assoc. 7: 381-400. Steel, R. G. D., and J. H. Torrie, 1960. Principles and Procedures of Statistics. McGraw-Hill Book Company, Inc., New York. Stevens, A., 1970. Chilling equipment must go, Hillcrest's Stevens insists. Broiler Industry, 33(3): S3.
J. W. DEATON, 1 F. N. REECE, 2 L. F. KUBENA, 1 B. D. LOTT 1 AND J. D. MAY 1 United States Department of Agriculture, A.R.S., State College, Mississippi 39762 (Received for publication May 1, 1972)
ABSTRACT Previous work at this laboratory demonstrated that broiler chicks could compensate by market age from early growth depression when reduced brooding temperature was the deterrent. Lott (1971) demonstrated diets which depressed broiler body weight at 4 weeks of age. The major diet differences were dietary energy levels. In an attempt to determine if the compensatory ability phenomenon could be utilized in broiler diet formulations for possible economic gain, 3 trials utilizing a total of 2,736 commercial broiler chickens were conducted. Results obtained showed that birds fed a diet containing 3141 kcal. of M.E.Ag- had a 4% reduction in body weight at 4 weeks of age, as compared to birds fed a diet containing 3306 kcal. of M.E./kg. By 8 weeks of age the males were able to compensate for the 4% reduction in 4-week body weight when fed a high-energy diet containing 3372 kcal. of M.E.Ag- Females could compensate for the 4% reduction in 4-week weight by 8 weeks of age when fed diets containing either 3207 or 3372 kcal. of M.E./kg. The percentage ether extract of the carcass at market age increased, however, for the groups demonstrating compensatory weight gain ability. Feed required per unit of gain increased as energy content of diet combinations decreased. POULTRY SCIENCE 52:
INTRODUCTION
P
REVIOUS work at this laboratory (Reece and Deaton, 1968) demonstrated that when body weights for broiler chicks brooded with reduced heat were not more than 13% lower at 3 weeks than those conventionally brooded, the bodyweight differences were eliminated by 8 weeks of age. Between 3 and 8 weeks, all birds were reared in one group. Lott 1 Animal Science Research Division, Poultry Research Branch, South Central Poultry Research Laboratory, State College, Mississippi. 2 Agricultural Engineering Research Division, Farm Electrification Research Branch, South Central Poultry Research Laboratory, State College, Mississippi.
262-265,
1973
(1971) demonstrated diets which depressed broiler body weight at 4 weeks of age. The major diet differences were dietary energy levels. In an attempt to determine if the compensatory ability phenomenon could be utilized in broiler diet formulations for possible economic advantage, the following study was conducted. EXPERIMENTAL PROCEDURE
Three trials utilizing a total of 2,736 commercial broiler chickens were conducted. For each trial, 12 1.51- by 3.7-meter pens were used with 38 male and 38 female broiler chicks placed per pen. The
Downloaded from http://ps.oxfordjournals.org/ at Southern Illinois University on June 6, 2015
The Ability of the Broiler Chicken to Compensate for Early Growth Depression