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Chemical preservation of whole broiler carcasses utilizing alkaline hydroxides1
ENVIRONMENT AND HEALTH Chemical Preservation of Whole Broiler Carcasses Utilizing Alkaline Hydroxides1 D. J. Shafer, J. B. Carey,2 R. P. Burgess, K. A. Conrad, and J. F. Prochaska Department of Poultry Science, Texas A&M University, College Station, Texas 77843-2472 growth, and solids content of the alkaline solutions. Sodium hydroxide at 1.9 and 2.0 M diffused throughout the carcass and produced adequate preservation without apparent putrefaction through 10 d. Aerobic bacteria were not recovered from sodium hydroxide solutions, carcass skin, or intestine samples at the 1.9 M concentration. Treatments of 2.0 M potassium hydroxide and a mixture of 1.5 M potassium hydroxide with 0.5 M sodium hydroxide produced the highest degree of carcass liquification at 10 d without visible putrefaction. Sodium hydroxide solution (2.0 M):carcass weight ratios ranging from 1:1 through 4:1 (wt:wt) were effective in preserving individual carcasses for more than 60 d without putrefaction.
(Key words: mortality, alkaline, preservation, broiler, hydroxide) 2000 Poultry Science 79:1517–1523
INTRODUCTION Consideration of a chemical method to preserve poultry production mortalities has a historical basis within early agriculture and food preservation methods. Bacteria can be digested by exposure to strong (pH >10) alkaline conditions (Atlas, 1984). The preservative action of pH and chemicals has been used by mankind to preserve and enhance food quality (Ayres et al., 1980). Alkaline hydroxides have been used in the past to dry and preserve eggs and meats. Alkaline hydroxide solutions are used in modern food sanitation, processing, and preservation. These chemicals are used by the animal by-products industry to process hides and manufacture mineral slurry and gelatins from bones and connective tissue, and in the industrial manufacturing of soaps from animal tallow (Myers, 1992). Alkaline reagents are used in many of these roles for fast reactivity or corrosive action on the substrate, and may be referred to in these processes as an accelerant or catalyst. Early methods to render feathers included the addition of sodium hydroxide (NaOH) as an accelerant
Received for publication June 10, 1999. Accepted for publication June 19, 2000. 1 The use of trade names in this publication does not imply endorsement by the Texas Agricultural Experiment Station nor criticism of similar products not mentioned. 2 To whom correspondence should be addressed: [email protected].
to hydrolyze feathers in order to lower the temperature and time required for processing. Current guidelines for hydrolyzed poultry feathers require meals to be free of additives or accelerants (AAFCO, 1994). The ability of 17.5% hydrated lime (calcium hydroxide) in water-based solution to preserve carcasses as they are chopped by rotary blades has previously been examined (G. W. Malone, 1993, Research and Education Center, University of Delaware, Georgetown, DE 19947, personal communication). Whole birds with feathers were added at weekly intervals for 8 wk. Preserved, chopped carcass proximate analysis values of 33.0% crude protein and 5.64% fat were observed. Amino acid analyses found cystine and lanthionine concentrations of 0.10 and 0.10%, respectively. These percentages compare with earlier observations from acid-preserved carcasses reported to contain 0.75% cystine and no measurable lanthionine. The low solubility and hardness of calcium in solutions may have inhibited rapid hydrolysis and solubilization of the carcasses. The solution successfully digested feathers, but produced calcium scale and ammonia odor at 7 wk. The production of lanthionine from the disulfide bond disruption of sulfur amino acids and cross-linkage formation of other non-nutritive amino acids due to racemization has been documented in animal and grain proteins (Masters and Friedman, 1979). Studies using poultry byproducts treated with alkali have concentrated on either moderate to mid-range alkaline treatments used in con-
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ABSTRACT The chemical preservation of whole broiler carcasses utilizing aqueous alkaline hydroxide solutions was examined as an alternative method of mortality management. Conversion of the preserved carcasses and solutions into an acceptable poultry by-product meal was examined. This research identified the basic parameters for effective preservative solutions that simultaneously hydrolyzed feathers and preserved the carcass. Euthanized, fully feathered, mature broilers were placed in potassium hydroxide (0.5 to 2.0 M) and sodium hydroxide (0.12 to 2.0 M) solutions for 5 and 10 d. Effectiveness was evaluated by visible feather degradation and carcass solubilization, odor production, inhibition of microbial
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MATERIALS AND METHODS Experiments were conducted to examine the effects of different alkaline hydroxide sources and concentrations on whole feathered broiler carcasses. The experimental design consisted of a one-way analysis of variance with four treatments and three experimental units, using a total of 12 broiler carcasses per experiment. Experiment 1 examined 8% (wt/wt) solutions of calcium hydroxide [1.9 M Ca(OH)2, pH 12.7], magnesium hydroxide [3.5 M Mg(OH)2, pH 10.4], potassium hydroxide [1.6 M KOH, pH 14.0], and sodium hydroxide [1.9 M NaOH, pH 14.0]. Experiment 2 was conducted utilizing NaOH at 0.12 (pH 12.9), 0.24 (pH 13.0), 0.36 (pH 13.2), and 0.48 M (pH 13.4) concentrations. Experiments 3 and 4 evaluated NaOH at 0.48 (pH 13.4), 0.97 (pH 13.7), 1.4 (pH 13.8), and 1.9 M (pH 14.0) concentrations. The NaOH solutions of 0.48 (pH 13.6), 0.72 (pH 13.7), 0.97 (pH 13.7), and 1.2 M (pH 14.0) concentrations were used for Experiments 5 and 6. Experiments 7 and 8 utilized KOH and NaOH in concentrations of 2.0 M NaOH, 1.5 M NaOH plus 0.5 M KOH, 1.5 M KOH plus 0.5 M NaOH, and 2.0 M KOH. The pH values of these solutions were all beyond the range of the pH meter used (pH >14.0).
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Sigma Chemical Co., St. Louis, MO 63178. Leco Corporation, St. Joseph, MI 49085-2396. Difco Laboratories, Detroit, MI 48232.
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Hydroxide Solution and Carcass Preparation Solutions were prepared using analytical reagents of food-grade alkaline hydroxides in accordance with safety guidelines set forth in the material safety data sheets provided by the supplier.3 Dry alkaline hydroxide was dissolved in municipal chlorinated tap water with a pH of 8.0 to 8.4 at 20 C. Alkaline hydroxide solutions were stirred and allowed to equilibrate for 8 h, then were stirred prior to the addition of broiler carcasses. Mature broilers older than 6 wk of age and averaging 2.3 kg body weight were euthanized by carbon dioxide induction. The whole, fully feathered broiler carcasses were punctured with a knife on each side of the abdomen, and the blade was forced into the thoracic cavity to allow for solution entrance to both major body cavities. Individual carcasses were placed in labeled polyethylene smoke nets, with both ends secured with plastic pull ties. The net allowed for easy identification and removal of the carcass from the solution and weighing of the carcass separate from solution. Polyethylene, 15-L containers with lids were used to hold the solution and the carcass. A glass graduated cylinder (25 mL) and polyethylene desiccator plate were positioned between the carcass and lid to assure complete carcass immersion in the solution. Each carcass was placed in 8 L of treatment solution, except in the solution-to-carcass ratio study. Carcass and solution weights were recorded in grams at the start and finish of each experiment. Degradation of feathers and carcasses were observed at 5 and 10 d for evidence of preservation and putrefaction. Solutions were monitored for initial and final pH and temperature values. Samples were collected at the conclusion of each experiment for analysis of solution solids and crude protein. Determinations of solids and protein contents of the solution were used as the measurement of feather and carcass degradation. Samples of the solutions were collected after removal of carcasses. Carcass-free solutions were constantly agitated by a magnetic bar on a stir plate prior to the sampling. Samples were collected with a polyethylene dipper (50 mL) and refrigerated at 5 C until analysis. Solution solids content was determined in 5-g samples, three samples per container (36 samples), and dried for 24 h at 105 C in a mechanical convection oven (AOAC, 1984). No adjustments were made for the solids contributed by the alkaline hydroxide reagents. Solution crude protein was analyzed using an automated nitrogen analyzer (Leco威 FP-428 Nitrogen Determinator)4, using 0.17- 0.20-g liquid samples, with three samples per container (36 samples). Solution and carcass samples were examined microscopically for feather content, cellular disruption, and presence of microbial organisms. Bacterial contents of solution and carcass were evaluated by presence or absence of aerobic plate growth at the end of each 10-d treatment. One milliliter of solution, or 1 g of skin or intestine sample from each container, was aseptically transferred onto a sterile petri dish, and 15 mL tryptic soy agar5 was added. Skin and intestine
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junction with heat processing to determine processing effects on poultry feathers (Latshaw, 1990). Effective handling of mortalities in the future should focus on the ultimate removal of poultry mortalities from the live production facility and their processing in a nutrient recovery facility. The efficacy of a liquid holding system could be evaluated by sample collection and determination of factors such as pH, protein, and solids content. The percentage of solids within the solution would provide information to allow processors to determine whether separate processing of the solution, after carcass removal, would be efficient in terms of energy expended to retrieve the nutrients. However, a uniform emulsion of carcass and solution might be a prudent alternative. The poultry industry could recover nutrients in a hydrolyzed pre-processed form that could be maintained for long periods with proper monitoring and addition of further alkaline hydroxide, if needed, to prevent microbial or pest infestations. If the alkaline solution and treated carcasses were retrieved and processed with neutral or acidic products from processing, such as blood or offal, a neutral-to-mildly alkaline poultry by-product could be produced. The production of poultry by-product meals from mortalities would be enhanced if the mortalities were held on the farm without putrefaction and the associated odors, pests, and biosecurity concerns. As a result, this study was conducted to gain further knowledge under controlled conditions of the effectiveness of alkaline hydroxides in the chemical preservation of whole broiler carcasses.
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PRESERVATION OF BROILER CARCASSES TABLE 1. Solution solids, protein, aerobic plate growth, and solution pH of different alkaline hydroxide solutions1 after 5 d treatment of whole broiler carcasses, Experiment 1 Item
Concentration2
Solids
(M) Treatment NaOH Ca(OH)2 KOH Mg(OH)2 SEM
1.9 1.9 1.6 3.5
Protein (%)
A
20.06 9.62B 20.68A 9.60B 0.26
Growth3
pH
(+/−) A
0.91 0.05B 1.06A 0.19B 0.04
− − − −
13.9 12.6 13.9 10.4
Means with no common superscripts within columns differ significantly (P < 0.01). Means of nine observations. 2 8% by weight in all solutions. 3 Growth (+), no growth (−); observed aerobic plate growth at 72 h. A,B 1
Solution-to-Carcass Ratio To determine the minimum quantity of solution necessary to stabilize and preserve individual, whole broiler carcasses, a range of solution-to-carcass ratios (wt/wt) were examined using 2.0 M NaOH. For four treatments and three experimental units, the experimental design was the same as in previous experiments. Solution-tocarcass ratios of 4:1, 3:1, 2:1, and 1:1 (wt/wt) were examined. For this study, carcass puncture, smoke net, and immersion procedures were omitted. After euthanasia, the carcass was placed into a polyethylene bag with the appropriate weight of 2.0 M NaOH solution, and all air was voided. The top of the bag was tightly sealed with vinyl-coated wire ties. This maintained total immersion of the carcass within the solution among all treatments, even with reduced solution volume at the lower ratios.
Statistical Analysis Data from each experiment were analyzed independently in a one-way analysis of variance. Statistical calculations were processed by computer using SAS statistical analysis software program (Version 6.11).6 Mean differences and pooled SEM were separated by the pdiff option (pair-wise t-tests) of the general linear model procedure.
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SAS Institute Inc., Cary, NC 27511-8000.
RESULTS Experiment 1: 8% Solutions By Day 5, carcasses in the 8% (wt/wt) NaOH (1.9 M) and KOH (1.6 M) solutions were observed to be without the majority of plumage, limbs, and skin, with a final ph of 13.9 for both solutions. Degradation continued past the skin into the deep muscle mass. Most noticeable was the fresh, bright red color of the flesh, with the pectoralis muscles having a frozen appearance when dissected. Internal organs were partially degraded in the thoracic cavity. The abdominal organs were intact, except for the intestines, of which areas exposed to the solution were partially solubilized. Heads and feet had a tendency to dissolve partially, including associated bone structures. Some of the poultry heads were solubilized completely in the NaOH treatments, but not in the KOH treatments. Odor was minimal and was characterized as that of a slight chemical or soap smell. Final solution pH for both the NaOH and KOH treatments was 13.9. There appeared to be production of a crude saponified product from the skin and subcutaneous fat reacting with the hydroxides. The Ca(OH)2 and Mg(OH)2 did not achieve any visible chemical degradation of the carcasses or feathers; final pH was 12.6 for Ca(OH)2 and 10.4 for Mg(OH)2. These carcasses were visibly distended, swollen, and strong in odor. Solution solids and protein were significantly higher in the potassium and sodium alkaline treatments in comparison with the calcium and magnesium solutions (Table 1), further indicating the carcass solubilization occurring in the NaOH and KOH treatments. The effectiveness of the hydroxides may be related to differences in solubility and dissociation characteristics; KOH and NaOH are highly soluble and corrosive compared with the lower solubility and dissociative action of Ca(OH)2 and Mg(OH)2.
Experiment 2: NaOH Molar Solutions Experiment 2 evaluated the use of NaOH at lower concentrations. The solutions of 0.12, 0.24, 0.36, and 0.48 M strength all failed to produce adequate inhibition of putrefaction. The majority of carcasses from the treatments
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tissues were selected for sampling due to the repeatability of sampling among treatments. All plates were allowed to cool and solidify prior to being inverted and incubated at 37 C for 72 h. Plates were examined for the presence or absence of microbial growth at 24, 48, and 72 h. Detection limits were not established, because visual confirmation of growth over time was the only measured parameter. No sample dilutions were performed in the aerobic bacteria growth studies. Highly solubilized carcasses were not evaluated for skin and intestine bacterial growth due to difficulty in obtaining reproducible sampling from the solubilized material. The presence of strictly anaerobic bacteria was not evaluated in the studies.
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TABLE 2. Solution solids, protein composition, and solution pH of different molar concentrations of sodium hydroxide solutions1 after 10 d treatment of whole broiler carcasses, Experiment 2 Item
Solids
Protein
pH
0.03B 0.14B 0.16B 0.41A 0.04
8.7 12.2 12.9 13.0
(%) NaOH,2 M 0.12 0.24 0.36 0.48 SEM
3.37C 3.41C 4.15B 5.11A 0.21
A–C Means with no common superscripts within columns differ significantly (P < 0.01). 1 Means of nine observations. 2 Alkaline hydroxide is expressed as moles per liter concentration equivalent to 0.5, 1.0, 1.5 and 2.0% of solution by weight.
of the carcass over 10 d, with no feathers visibly remaining and minimal non-putrid chemical odor resembling detergent soap with ammonia. Final pH of the solutions was lower than initial pH in all treatments except the 1.9 M NaOH solutions, which remained at pH 14 (Table 3). Solution solids were significantly increased as NaOH concentration increased. Solution protein from the 1.9 M treatment was significantly increased in both experiments.
Experiments 5 and 6: NaOH Molar Solutions
Experiments 3 and 4: NaOH Molar Solutions
Experiments 7 and 8: 2.0 M NaOH and KOH Solutions
A range of NaOH solution concentrations (0.48, 0.97, 1.4, and 1.9 M) were examined over 10 d in duplicate experiments. The 0.97 and 1.4 M treatments resulted in some skin and carcass degradation and feather hydrolysis. Feathers were not removed completely at the 0.48 and 0.97 M concentrations. Skin and muscle degradation were extensive in some samples and not in others at 0.48 and 0.97 M. Odor was minimal through d 10 in the 1.4 and 1.9 M treatments, but offensive odors developed in the 0.48 and 0.97 M treatments by 5 d. The 1.9 M solution showed the most advanced hydrolysis and preservation
Four alkaline hydroxide treatments consisting of 2.0 M KOH, 1.5 M KOH with 0.5 M NaOH, 2.0 M NaOH, and 1.5 M NaOH with 0.5 M KOH were compared. All solutions contained extensive feather and carcass hydrolysis products in a solubilized and visibly preserved form at 10 d. An extensively hydrolyzed uniform emulsified product from carcasses was produced in 2.0 M KOH and 1.5 M KOH with 0.5 M NaOH solutions. An extensively hydrolyzed and coarsely emulsified product was achieved by the 2.0 M NaOH and 1.5 M NaOH with 0.5 M KOH solutions. Remnants of the axial and appendicular skele-
TABLE 3. Solution solids, protein composition, and solution pH of different molar concentrations of sodium hydroxide solutions1 after 10 d treatment of whole broiler carcasses, Experiments 3 and 4 Experiment 3 Solids
Protein
Experiment 4 pH
Solids
(%) NaOH,2 M 0.48 0.97 1.4 1.9 SEM
9.69D 12.69C 18.73B 21.54A 0.57
Protein
pH
0.42C 0.65BC 0.91B 1.84A 0.07
11.2 12.7 13.3 14.0
(%) 0.45C 0.55C 1.46B 3.19A 0.12
12.4 12.5 13.0 14.0
9.63D 12.76C 18.10B 22.05A 0.71
Means with no common superscripts within columns differ significantly (P < 0.01). Means of nine observations. 2 Alkaline hydroxide is expressed as moles per liter concentration equivalent to 2, 4, 6, and 8% of solution by weight. A–D 1
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were swollen and had minimal feather degradation. All carcasses were characterized by strong and extremely putrid odor by 5 through 10 d. One carcass each in the 0.36 and 0.48 M treatments had a larger proportion of feathers released from the skin and visible partial solubilization of skin, head, and feet. A large and variable decline in final pH values of the solutions was evident in all treatments (Table 2). Solution solids were significantly increased in the 0.36 and 0.48 M NaOH compared with lower alkaline concentrations, whereas protein content was significantly higher only in 0.48 M samples.
The 0.48, 0.72, 0.97, and 1.2 M solutions of NaOH were examined in duplicate experiments. These treatments gave mixed results. The majority of feather and carcass degradation occurred in the 0.97 and 1.2 M solutions. The 0.48 and 0.72 M treatments did effectively loosen the majority of feathers from the carcasses. In Experiment 5, the 0.48 and 0.72 M treatments had visibly greater degradation of feathers than the same treatments in Experiment 6. Final pH of the solutions was considerably lower than the initial pH values of all solutions and both experiments. Solution solids were significantly increased as NaOH concentration increased. However, solution protein was unchanged except in the 0.48 M treatment, which was significantly lower (Table 4).
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PRESERVATION OF BROILER CARCASSES TABLE 4. Solution solids, protein composition, and solution pH of different molar concentrations of sodium hydroxide solutions1 after 10 d treatment of whole broiler carcasses, Experiments 5 and 6 Experiment 5 Solids
Experiment 6
Protein
pH
Solids
(%) NaOH,2 M 0.48 0.72 0.97 1.2 SEM
Protein
pH
1.19A 1.47A 1.31A 1.48A 0.14
11.7 11.7 13.7 13.8
(%)
4.20D 5.03C 12.10B 15.72A 0.20
0.86B 1.41A 1.67A 1.47A 0.18
12.9 12.3 12.5 12.8
4.89D 9.14C 12.40B 14.16A 0.33
Means with no common superscripts within columns differ significantly (P < 0.01). Means of nine observations. 2 Alkaline hydroxide is expressed as moles per liter concentration equivalent to 2, 3, 4, and 5% of solution by weight. A–D 1
Experiment 9: Solution-to-Carcass Ratio The 2.0 M NaOH solution concentration was used to evaluate solution-to-carcass ratios (wt:wt) of 1:1, 2:1, 3:1, and 4:1. Each ratio was observed to be effective in carcass preservation and feather liquification by 10 d. All four
ratios were found to be adequate in maintaining the carcass for greater than 60 d without putrefaction. No visible quantity of gas was accumulated in the sealed polyethylene bags. The degree of solubilization to the carcass after 60 d was not visibly different between the four treatments. Feathers, skin, external structures, and the majority of the carcass were solubilized in all treatments. Intact material appeared to be thoroughly preserved and friable upon touch, including skeletal remains. The final pH at 60 d of the 1:1 and 2:1 solution-to-carcass ratios were reduced to 13.5 and 13.8, respectively. The 3:1 and 4:1 treatments were not reduced from an initial pH value of 14. Samples at 60 d were significantly higher in solution solids and protein as ratio of solution decreased, as would be expected from the reduction of volume for each ratio treatment (Table 6).
Aerobic Plate Growth No viable bacteria were observed in Experiment 1 from any of the different alkaline hydroxide solutions after 5 d (Table 1). Microbial growth was observed from all samples of solution, skin, and intestine from the 0.12, 0.24, 0.36, and 0.48 M NaOH treatments of Experiment 2. Bacteria were observed from intestine samples of the 0.48, 0.97, and 1.4 M treatments examined in duplicate experiments.
TABLE 5. Solution solids, protein, aerobic plate growth, and solution pH of sodium and potassium hydroxide solutions1 after 10 d treatment of whole broiler carcasses, Experiments 7 and 8 Treatment concentration NaOH
KOH
Experiment 7 Solids
(M) 2.0 1.5 0.5 0.0
Protein
24.40B 25.04B 36.16A 36.04A
Growth
pH
Solids
2
(%) 0.0 0.5 1.5 2.0
Experiment 8
(+/−) 1.93B 2.26B 3.83A 4.55A
− − − −
23.93B 24.50B 35.10A 35.47A
0.20
0.17
Means with no common superscripts within columns differ significantly (P < 0.01). Means of nine observations. 2 Growth (+), no growth (−); observed aerobic plate growth at 72 h. A,B 1
pH
(+/−) 1.86B 2.21B 3.65A 4.29A
(SEM) 0.22
Growth 2
(%) 14.0 14.0 14.0 14.0
(SEM) 0.26
Protein
− − − −
14.0 14.0 14.0 14.0
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ton and traces of digestive organs were found, but they were extremely soft and appeared to have been thoroughly diffused by the solution. For all of these treatments, the carcasses were hydrolyzed to such an extensive degree that when stirred, there was no distinction between solution solids and carcass. All solutions maintained initial pH values greater than the endpoint measurement of the pH meter (pH >14.0). No decline in pH was observed in any of the solutions. Odor was characterized as primarily chemical or soap, with secondary ammonia undertones. A crude saponified product, presumed to be from the subcutaneous fat reacting with the alkaline hydroxides, was formed and floated on the surface of all undisturbed solutions. No intact feathers were visible in the emulsified solutions. Solution solids and protein were significantly increased from the 2.0 M KOH and the 1.5 M KOH with 0.5 M NaOH treatments compared with the 2.0 M NaOH and 1.5 M NaOH with 0.5 M KOH solutions in both experiments (Table 5).
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TABLE 6. Solution solids, protein composition, and solution pH of different ratios of 2.0 molar sodium hydroxide solution1 to carcass weight after 60 d treatment Item
Solids
Protein
pH
4.24A 3.52B 1.85C 1.18D 0.53
13.5 13.8 14.0 14.0
(%) NaOH:carcass ratio2 1:1 2:1 3:1 4:1 SEM
41.18A 33.73B 20.45C 12.34D 0.89
A–D Means with no common superscripts within columns differ significantly (P < 0.01). 1 Means of nine observations. 2 Ratio of 2.0 molar sodium hydroxide solution to carcass by weight.
Microscopic Evaluation Samples of solution and carcasses were examined visually for presence of feathers. Only those solutions and carcasses that were deemed to be visually free of feathers or remnants of feathers were sampled and inspected microscopically (10× and 40× magnification) for traces of intact feather fragments and other biological structures, such as tissue cells or insects. Samples from the 10-d treatment in 1.9 M NaOH of Experiments 4 and 5 contained microscopically visible feather remnants. Examination of the 10-d KOH solutions of 1.9 and 2.0, and 1.5 M with 0.5 M NaOH were negative for traces of feather, pests, and intact tissue cells. Solution and carcass samples from 10-d treatment with NaOH at 2.0 M and 1.5 M with 0.5 M KOH concentrations were negative for feathers, insects, and other biologically recognizable intact structures under microscopic examination. Samples from the solution-to-carcass ratio treatments were examined after 60 d and found to be negative for feather or other detectable structures for all ratio treatments. Examination of the samples was hindered by the concentration of crudely saponified fat in the lower stocking ratio samples and may have masked minute feather particles.
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Cole-Parmer Instrument Company, Niles, IL 60714. Delta Distributors, Houston, TX 77047.
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Alkaline hydroxide solutions hydrolyzed and preserved whole mature broiler carcasses with feathers. The research identified the basic parameters for effective preservative solutions that simultaneously degraded feathers and preserved the carcass. Effectiveness was related to visible feather and carcass solubilization, absence of putrefactive odors, inhibition of bacterial growth, and solids content of the alkaline solutions. Treatments of 2.0 M KOH and 1.5 M KOH with 0.5 M NaOH produced the highest degree of carcass degradation at 10 d without visible putrefaction; NaOH produced similar results at 1.9, 2.0, and 1.5 M with 0.5 M KOH. These concentrations hydrolyzed all feathers, diffused throughout the carcass, and produced adequate preservation to prevent putrefaction through 10 d. The NaOH inhibited bacteria in the solution at concentrations of 0.72 M, whereas carcass bacteria were not recovered at 1.9 M after 10 d. At a 1:1 ratio (wt:wt) of 2.0 M NaOH solution to whole broiler carcass, individual carcasses were maintained for more than 60 d without putrefaction. Analysis of costs to provide alkaline preservation for an individual broiler production unit was conducted using calculations based on 2.0 M NaOH aqueous solution in a 1:1 ratio (wt:wt) with broiler mortalities. Assuming an average mortality of 0.1% daily over 49 d, a flock of 25,000 broilers will produce 1,134 kg (2,500 lbs) of mortality (Blake et al., 1990). A poultry production unit of four houses, each with a 25,000-broiler capacity, would generate 4,537 kg (10,000 lbs) total mortality over a 49-d growout period. An equivalent amount (wt:wt) of 2.0 M NaOH solution would be required. The total mortality and solution weight would then equal 9,074 kg (20,000 lbs). Assuming that alkaline solution and carcasses will have a density equal to or greater than water, 9,074 kg (20,000 pounds) of alkaline solution and mortalities would, at most, require a container of 9,074 L (2,398 gal). A fully enclosed top-loading tank with 9,462 L (2,500 gal) capacity, manufactured from food grade-polyethylene, would have an estimated cost of $1,300.00.7 To amortize tank costs over 8 yr and 48 flocks, the tank cost per flock will equal $27.08. To produce the 4,537 kg (10,000 lbs) of 2.0 M NaOH solution would require 377 kg (830 lbs) of NaOH. Purchase of NaOH (97% purity) in bulk would cost $0.88/kg ($0.40/lb) for a total 49-d cost of $332.00.8 Therefore, estimated costs (excluding cost of water) to preserve 4,537 kg (10,000 lbs) of mortality over a 49-d period equal $359.08, or $0.0791 per kg ($0.0359/lb), of mortality. These costs are lower than estimates projected by Crews et al. (1995) for a 100,000-broiler production unit utilizing refrigeration, incineration, large-bin composting, or fermentation. One of the primary areas of research necessary prior to implementation of an alkaline preservation treatment for poultry mortalities is its effectiveness when utilized in preserving multiple carcass batches under actual production conditions. Development and integration of onfarm holding limits and scheduling of the preserved mate-
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Bacterial growth were not observed from samples of the solutions and skin at the 1.4 and 1.9 M treatments. The 0.48, 0.72, 0.97, and 1.2 M solutions of NaOH produced some observable microbial growth from samples of skin and intestine, but not from all samples of duplicate experiments. Solution samples from the 0.48 M NaOH treatments produced aerobic growth, whereas 0.72, 0.97, and 1.2 M solutions were negative. In duplicate experiments consisting of 2.0 M KOH, 1.5 M KOH with 0.5 M NaOH, 2.0 M NaOH, and 1.5 M NaOH with 0.5 M KOH, no viable bacterial growth were observed from any of the solutions (Table 5). Skin and intestine samples were not retrieved due to the high degree of chemical degradation to the carcasses.
DISCUSSION
PRESERVATION OF BROILER CARCASSES
rial for nutrient recovery will need to be planned. Equipment for dumping or pumping of tanks, or the exchange of full holding tanks for empty tanks will need to be acquired. Factors for future consideration include the need for research into the processing necessary for nutrient recovery and neutralization of the excess alkaline content of the preserved poultry.
REFERENCES
Ayres, J. C., J. O. Mundt, and W. E. Sandine, 1980. Chemicals in foods. Pages 123–144 in: Microbiology of Foods. W. H. Freeman and Co., San Francisco, CA. Blake, J. P., M. F. Cook, and D. Reynolds, 1990. Dry extrusion of poultry processing plant wastes and poultry farm mortalities. Pages 319–327 in: Proceedings of the Sixth International Symposium on Agricultural and Food Processing Wastes. American Society of Agricultural Engineers, St. Joseph, MI. Crews, J. R., J. O. Donald, and J. P. Blake, 1995. An economic evaluation of dead bird disposal systems. Circular ANR-914. Alabama Cooperative Extension Service, Auburn University, Auburn, AL. Latshaw, J. D., 1990. Quality of feather meal as affected by feather processing conditions. Poultry Sci. 69:953–958. Masters, P. M., and M. Friedman, 1979. Racemization of amino acids in alkali-treated food proteins. J. Agric. Food Chem. 27:507–511. Myers, E. G., 1992. Soaps and detergents. Pages 149–176 in: Inedible Meat By-Products. Vol. 8. A. M. Pearson and T. R. Dutson, ed. Elsevier Science Publishers Ltd., Barking, Essex, England.
Downloaded from http://ps.oxfordjournals.org/ at University of Pennsylvania Library on June 29, 2015
AOAC, 1984. Official Methods of Analysis. 14th ed. Washington, DC. Association of American Feed Control Officials, 1994. Official Publication. West Virginia Department of Agriculture, Charleston, WV. Atlas, R. M., 1984. Microbiology Fundamentals and Applications. Macmillan Publishing Co., New York, NY.
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(Key words: mortality, alkaline, preservation, broiler, hydroxide) 2000 Poultry Science 79:1517–1523
INTRODUCTION Consideration of a chemical method to preserve poultry production mortalities has a historical basis within early agriculture and food preservation methods. Bacteria can be digested by exposure to strong (pH >10) alkaline conditions (Atlas, 1984). The preservative action of pH and chemicals has been used by mankind to preserve and enhance food quality (Ayres et al., 1980). Alkaline hydroxides have been used in the past to dry and preserve eggs and meats. Alkaline hydroxide solutions are used in modern food sanitation, processing, and preservation. These chemicals are used by the animal by-products industry to process hides and manufacture mineral slurry and gelatins from bones and connective tissue, and in the industrial manufacturing of soaps from animal tallow (Myers, 1992). Alkaline reagents are used in many of these roles for fast reactivity or corrosive action on the substrate, and may be referred to in these processes as an accelerant or catalyst. Early methods to render feathers included the addition of sodium hydroxide (NaOH) as an accelerant
Received for publication June 10, 1999. Accepted for publication June 19, 2000. 1 The use of trade names in this publication does not imply endorsement by the Texas Agricultural Experiment Station nor criticism of similar products not mentioned. 2 To whom correspondence should be addressed: [email protected].
to hydrolyze feathers in order to lower the temperature and time required for processing. Current guidelines for hydrolyzed poultry feathers require meals to be free of additives or accelerants (AAFCO, 1994). The ability of 17.5% hydrated lime (calcium hydroxide) in water-based solution to preserve carcasses as they are chopped by rotary blades has previously been examined (G. W. Malone, 1993, Research and Education Center, University of Delaware, Georgetown, DE 19947, personal communication). Whole birds with feathers were added at weekly intervals for 8 wk. Preserved, chopped carcass proximate analysis values of 33.0% crude protein and 5.64% fat were observed. Amino acid analyses found cystine and lanthionine concentrations of 0.10 and 0.10%, respectively. These percentages compare with earlier observations from acid-preserved carcasses reported to contain 0.75% cystine and no measurable lanthionine. The low solubility and hardness of calcium in solutions may have inhibited rapid hydrolysis and solubilization of the carcasses. The solution successfully digested feathers, but produced calcium scale and ammonia odor at 7 wk. The production of lanthionine from the disulfide bond disruption of sulfur amino acids and cross-linkage formation of other non-nutritive amino acids due to racemization has been documented in animal and grain proteins (Masters and Friedman, 1979). Studies using poultry byproducts treated with alkali have concentrated on either moderate to mid-range alkaline treatments used in con-
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ABSTRACT The chemical preservation of whole broiler carcasses utilizing aqueous alkaline hydroxide solutions was examined as an alternative method of mortality management. Conversion of the preserved carcasses and solutions into an acceptable poultry by-product meal was examined. This research identified the basic parameters for effective preservative solutions that simultaneously hydrolyzed feathers and preserved the carcass. Euthanized, fully feathered, mature broilers were placed in potassium hydroxide (0.5 to 2.0 M) and sodium hydroxide (0.12 to 2.0 M) solutions for 5 and 10 d. Effectiveness was evaluated by visible feather degradation and carcass solubilization, odor production, inhibition of microbial
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MATERIALS AND METHODS Experiments were conducted to examine the effects of different alkaline hydroxide sources and concentrations on whole feathered broiler carcasses. The experimental design consisted of a one-way analysis of variance with four treatments and three experimental units, using a total of 12 broiler carcasses per experiment. Experiment 1 examined 8% (wt/wt) solutions of calcium hydroxide [1.9 M Ca(OH)2, pH 12.7], magnesium hydroxide [3.5 M Mg(OH)2, pH 10.4], potassium hydroxide [1.6 M KOH, pH 14.0], and sodium hydroxide [1.9 M NaOH, pH 14.0]. Experiment 2 was conducted utilizing NaOH at 0.12 (pH 12.9), 0.24 (pH 13.0), 0.36 (pH 13.2), and 0.48 M (pH 13.4) concentrations. Experiments 3 and 4 evaluated NaOH at 0.48 (pH 13.4), 0.97 (pH 13.7), 1.4 (pH 13.8), and 1.9 M (pH 14.0) concentrations. The NaOH solutions of 0.48 (pH 13.6), 0.72 (pH 13.7), 0.97 (pH 13.7), and 1.2 M (pH 14.0) concentrations were used for Experiments 5 and 6. Experiments 7 and 8 utilized KOH and NaOH in concentrations of 2.0 M NaOH, 1.5 M NaOH plus 0.5 M KOH, 1.5 M KOH plus 0.5 M NaOH, and 2.0 M KOH. The pH values of these solutions were all beyond the range of the pH meter used (pH >14.0).
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Sigma Chemical Co., St. Louis, MO 63178. Leco Corporation, St. Joseph, MI 49085-2396. Difco Laboratories, Detroit, MI 48232.
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Hydroxide Solution and Carcass Preparation Solutions were prepared using analytical reagents of food-grade alkaline hydroxides in accordance with safety guidelines set forth in the material safety data sheets provided by the supplier.3 Dry alkaline hydroxide was dissolved in municipal chlorinated tap water with a pH of 8.0 to 8.4 at 20 C. Alkaline hydroxide solutions were stirred and allowed to equilibrate for 8 h, then were stirred prior to the addition of broiler carcasses. Mature broilers older than 6 wk of age and averaging 2.3 kg body weight were euthanized by carbon dioxide induction. The whole, fully feathered broiler carcasses were punctured with a knife on each side of the abdomen, and the blade was forced into the thoracic cavity to allow for solution entrance to both major body cavities. Individual carcasses were placed in labeled polyethylene smoke nets, with both ends secured with plastic pull ties. The net allowed for easy identification and removal of the carcass from the solution and weighing of the carcass separate from solution. Polyethylene, 15-L containers with lids were used to hold the solution and the carcass. A glass graduated cylinder (25 mL) and polyethylene desiccator plate were positioned between the carcass and lid to assure complete carcass immersion in the solution. Each carcass was placed in 8 L of treatment solution, except in the solution-to-carcass ratio study. Carcass and solution weights were recorded in grams at the start and finish of each experiment. Degradation of feathers and carcasses were observed at 5 and 10 d for evidence of preservation and putrefaction. Solutions were monitored for initial and final pH and temperature values. Samples were collected at the conclusion of each experiment for analysis of solution solids and crude protein. Determinations of solids and protein contents of the solution were used as the measurement of feather and carcass degradation. Samples of the solutions were collected after removal of carcasses. Carcass-free solutions were constantly agitated by a magnetic bar on a stir plate prior to the sampling. Samples were collected with a polyethylene dipper (50 mL) and refrigerated at 5 C until analysis. Solution solids content was determined in 5-g samples, three samples per container (36 samples), and dried for 24 h at 105 C in a mechanical convection oven (AOAC, 1984). No adjustments were made for the solids contributed by the alkaline hydroxide reagents. Solution crude protein was analyzed using an automated nitrogen analyzer (Leco威 FP-428 Nitrogen Determinator)4, using 0.17- 0.20-g liquid samples, with three samples per container (36 samples). Solution and carcass samples were examined microscopically for feather content, cellular disruption, and presence of microbial organisms. Bacterial contents of solution and carcass were evaluated by presence or absence of aerobic plate growth at the end of each 10-d treatment. One milliliter of solution, or 1 g of skin or intestine sample from each container, was aseptically transferred onto a sterile petri dish, and 15 mL tryptic soy agar5 was added. Skin and intestine
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junction with heat processing to determine processing effects on poultry feathers (Latshaw, 1990). Effective handling of mortalities in the future should focus on the ultimate removal of poultry mortalities from the live production facility and their processing in a nutrient recovery facility. The efficacy of a liquid holding system could be evaluated by sample collection and determination of factors such as pH, protein, and solids content. The percentage of solids within the solution would provide information to allow processors to determine whether separate processing of the solution, after carcass removal, would be efficient in terms of energy expended to retrieve the nutrients. However, a uniform emulsion of carcass and solution might be a prudent alternative. The poultry industry could recover nutrients in a hydrolyzed pre-processed form that could be maintained for long periods with proper monitoring and addition of further alkaline hydroxide, if needed, to prevent microbial or pest infestations. If the alkaline solution and treated carcasses were retrieved and processed with neutral or acidic products from processing, such as blood or offal, a neutral-to-mildly alkaline poultry by-product could be produced. The production of poultry by-product meals from mortalities would be enhanced if the mortalities were held on the farm without putrefaction and the associated odors, pests, and biosecurity concerns. As a result, this study was conducted to gain further knowledge under controlled conditions of the effectiveness of alkaline hydroxides in the chemical preservation of whole broiler carcasses.
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PRESERVATION OF BROILER CARCASSES TABLE 1. Solution solids, protein, aerobic plate growth, and solution pH of different alkaline hydroxide solutions1 after 5 d treatment of whole broiler carcasses, Experiment 1 Item
Concentration2
Solids
(M) Treatment NaOH Ca(OH)2 KOH Mg(OH)2 SEM
1.9 1.9 1.6 3.5
Protein (%)
A
20.06 9.62B 20.68A 9.60B 0.26
Growth3
pH
(+/−) A
0.91 0.05B 1.06A 0.19B 0.04
− − − −
13.9 12.6 13.9 10.4
Means with no common superscripts within columns differ significantly (P < 0.01). Means of nine observations. 2 8% by weight in all solutions. 3 Growth (+), no growth (−); observed aerobic plate growth at 72 h. A,B 1
Solution-to-Carcass Ratio To determine the minimum quantity of solution necessary to stabilize and preserve individual, whole broiler carcasses, a range of solution-to-carcass ratios (wt/wt) were examined using 2.0 M NaOH. For four treatments and three experimental units, the experimental design was the same as in previous experiments. Solution-tocarcass ratios of 4:1, 3:1, 2:1, and 1:1 (wt/wt) were examined. For this study, carcass puncture, smoke net, and immersion procedures were omitted. After euthanasia, the carcass was placed into a polyethylene bag with the appropriate weight of 2.0 M NaOH solution, and all air was voided. The top of the bag was tightly sealed with vinyl-coated wire ties. This maintained total immersion of the carcass within the solution among all treatments, even with reduced solution volume at the lower ratios.
Statistical Analysis Data from each experiment were analyzed independently in a one-way analysis of variance. Statistical calculations were processed by computer using SAS statistical analysis software program (Version 6.11).6 Mean differences and pooled SEM were separated by the pdiff option (pair-wise t-tests) of the general linear model procedure.
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SAS Institute Inc., Cary, NC 27511-8000.
RESULTS Experiment 1: 8% Solutions By Day 5, carcasses in the 8% (wt/wt) NaOH (1.9 M) and KOH (1.6 M) solutions were observed to be without the majority of plumage, limbs, and skin, with a final ph of 13.9 for both solutions. Degradation continued past the skin into the deep muscle mass. Most noticeable was the fresh, bright red color of the flesh, with the pectoralis muscles having a frozen appearance when dissected. Internal organs were partially degraded in the thoracic cavity. The abdominal organs were intact, except for the intestines, of which areas exposed to the solution were partially solubilized. Heads and feet had a tendency to dissolve partially, including associated bone structures. Some of the poultry heads were solubilized completely in the NaOH treatments, but not in the KOH treatments. Odor was minimal and was characterized as that of a slight chemical or soap smell. Final solution pH for both the NaOH and KOH treatments was 13.9. There appeared to be production of a crude saponified product from the skin and subcutaneous fat reacting with the hydroxides. The Ca(OH)2 and Mg(OH)2 did not achieve any visible chemical degradation of the carcasses or feathers; final pH was 12.6 for Ca(OH)2 and 10.4 for Mg(OH)2. These carcasses were visibly distended, swollen, and strong in odor. Solution solids and protein were significantly higher in the potassium and sodium alkaline treatments in comparison with the calcium and magnesium solutions (Table 1), further indicating the carcass solubilization occurring in the NaOH and KOH treatments. The effectiveness of the hydroxides may be related to differences in solubility and dissociation characteristics; KOH and NaOH are highly soluble and corrosive compared with the lower solubility and dissociative action of Ca(OH)2 and Mg(OH)2.
Experiment 2: NaOH Molar Solutions Experiment 2 evaluated the use of NaOH at lower concentrations. The solutions of 0.12, 0.24, 0.36, and 0.48 M strength all failed to produce adequate inhibition of putrefaction. The majority of carcasses from the treatments
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tissues were selected for sampling due to the repeatability of sampling among treatments. All plates were allowed to cool and solidify prior to being inverted and incubated at 37 C for 72 h. Plates were examined for the presence or absence of microbial growth at 24, 48, and 72 h. Detection limits were not established, because visual confirmation of growth over time was the only measured parameter. No sample dilutions were performed in the aerobic bacteria growth studies. Highly solubilized carcasses were not evaluated for skin and intestine bacterial growth due to difficulty in obtaining reproducible sampling from the solubilized material. The presence of strictly anaerobic bacteria was not evaluated in the studies.
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TABLE 2. Solution solids, protein composition, and solution pH of different molar concentrations of sodium hydroxide solutions1 after 10 d treatment of whole broiler carcasses, Experiment 2 Item
Solids
Protein
pH
0.03B 0.14B 0.16B 0.41A 0.04
8.7 12.2 12.9 13.0
(%) NaOH,2 M 0.12 0.24 0.36 0.48 SEM
3.37C 3.41C 4.15B 5.11A 0.21
A–C Means with no common superscripts within columns differ significantly (P < 0.01). 1 Means of nine observations. 2 Alkaline hydroxide is expressed as moles per liter concentration equivalent to 0.5, 1.0, 1.5 and 2.0% of solution by weight.
of the carcass over 10 d, with no feathers visibly remaining and minimal non-putrid chemical odor resembling detergent soap with ammonia. Final pH of the solutions was lower than initial pH in all treatments except the 1.9 M NaOH solutions, which remained at pH 14 (Table 3). Solution solids were significantly increased as NaOH concentration increased. Solution protein from the 1.9 M treatment was significantly increased in both experiments.
Experiments 5 and 6: NaOH Molar Solutions
Experiments 3 and 4: NaOH Molar Solutions
Experiments 7 and 8: 2.0 M NaOH and KOH Solutions
A range of NaOH solution concentrations (0.48, 0.97, 1.4, and 1.9 M) were examined over 10 d in duplicate experiments. The 0.97 and 1.4 M treatments resulted in some skin and carcass degradation and feather hydrolysis. Feathers were not removed completely at the 0.48 and 0.97 M concentrations. Skin and muscle degradation were extensive in some samples and not in others at 0.48 and 0.97 M. Odor was minimal through d 10 in the 1.4 and 1.9 M treatments, but offensive odors developed in the 0.48 and 0.97 M treatments by 5 d. The 1.9 M solution showed the most advanced hydrolysis and preservation
Four alkaline hydroxide treatments consisting of 2.0 M KOH, 1.5 M KOH with 0.5 M NaOH, 2.0 M NaOH, and 1.5 M NaOH with 0.5 M KOH were compared. All solutions contained extensive feather and carcass hydrolysis products in a solubilized and visibly preserved form at 10 d. An extensively hydrolyzed uniform emulsified product from carcasses was produced in 2.0 M KOH and 1.5 M KOH with 0.5 M NaOH solutions. An extensively hydrolyzed and coarsely emulsified product was achieved by the 2.0 M NaOH and 1.5 M NaOH with 0.5 M KOH solutions. Remnants of the axial and appendicular skele-
TABLE 3. Solution solids, protein composition, and solution pH of different molar concentrations of sodium hydroxide solutions1 after 10 d treatment of whole broiler carcasses, Experiments 3 and 4 Experiment 3 Solids
Protein
Experiment 4 pH
Solids
(%) NaOH,2 M 0.48 0.97 1.4 1.9 SEM
9.69D 12.69C 18.73B 21.54A 0.57
Protein
pH
0.42C 0.65BC 0.91B 1.84A 0.07
11.2 12.7 13.3 14.0
(%) 0.45C 0.55C 1.46B 3.19A 0.12
12.4 12.5 13.0 14.0
9.63D 12.76C 18.10B 22.05A 0.71
Means with no common superscripts within columns differ significantly (P < 0.01). Means of nine observations. 2 Alkaline hydroxide is expressed as moles per liter concentration equivalent to 2, 4, 6, and 8% of solution by weight. A–D 1
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were swollen and had minimal feather degradation. All carcasses were characterized by strong and extremely putrid odor by 5 through 10 d. One carcass each in the 0.36 and 0.48 M treatments had a larger proportion of feathers released from the skin and visible partial solubilization of skin, head, and feet. A large and variable decline in final pH values of the solutions was evident in all treatments (Table 2). Solution solids were significantly increased in the 0.36 and 0.48 M NaOH compared with lower alkaline concentrations, whereas protein content was significantly higher only in 0.48 M samples.
The 0.48, 0.72, 0.97, and 1.2 M solutions of NaOH were examined in duplicate experiments. These treatments gave mixed results. The majority of feather and carcass degradation occurred in the 0.97 and 1.2 M solutions. The 0.48 and 0.72 M treatments did effectively loosen the majority of feathers from the carcasses. In Experiment 5, the 0.48 and 0.72 M treatments had visibly greater degradation of feathers than the same treatments in Experiment 6. Final pH of the solutions was considerably lower than the initial pH values of all solutions and both experiments. Solution solids were significantly increased as NaOH concentration increased. However, solution protein was unchanged except in the 0.48 M treatment, which was significantly lower (Table 4).
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PRESERVATION OF BROILER CARCASSES TABLE 4. Solution solids, protein composition, and solution pH of different molar concentrations of sodium hydroxide solutions1 after 10 d treatment of whole broiler carcasses, Experiments 5 and 6 Experiment 5 Solids
Experiment 6
Protein
pH
Solids
(%) NaOH,2 M 0.48 0.72 0.97 1.2 SEM
Protein
pH
1.19A 1.47A 1.31A 1.48A 0.14
11.7 11.7 13.7 13.8
(%)
4.20D 5.03C 12.10B 15.72A 0.20
0.86B 1.41A 1.67A 1.47A 0.18
12.9 12.3 12.5 12.8
4.89D 9.14C 12.40B 14.16A 0.33
Means with no common superscripts within columns differ significantly (P < 0.01). Means of nine observations. 2 Alkaline hydroxide is expressed as moles per liter concentration equivalent to 2, 3, 4, and 5% of solution by weight. A–D 1
Experiment 9: Solution-to-Carcass Ratio The 2.0 M NaOH solution concentration was used to evaluate solution-to-carcass ratios (wt:wt) of 1:1, 2:1, 3:1, and 4:1. Each ratio was observed to be effective in carcass preservation and feather liquification by 10 d. All four
ratios were found to be adequate in maintaining the carcass for greater than 60 d without putrefaction. No visible quantity of gas was accumulated in the sealed polyethylene bags. The degree of solubilization to the carcass after 60 d was not visibly different between the four treatments. Feathers, skin, external structures, and the majority of the carcass were solubilized in all treatments. Intact material appeared to be thoroughly preserved and friable upon touch, including skeletal remains. The final pH at 60 d of the 1:1 and 2:1 solution-to-carcass ratios were reduced to 13.5 and 13.8, respectively. The 3:1 and 4:1 treatments were not reduced from an initial pH value of 14. Samples at 60 d were significantly higher in solution solids and protein as ratio of solution decreased, as would be expected from the reduction of volume for each ratio treatment (Table 6).
Aerobic Plate Growth No viable bacteria were observed in Experiment 1 from any of the different alkaline hydroxide solutions after 5 d (Table 1). Microbial growth was observed from all samples of solution, skin, and intestine from the 0.12, 0.24, 0.36, and 0.48 M NaOH treatments of Experiment 2. Bacteria were observed from intestine samples of the 0.48, 0.97, and 1.4 M treatments examined in duplicate experiments.
TABLE 5. Solution solids, protein, aerobic plate growth, and solution pH of sodium and potassium hydroxide solutions1 after 10 d treatment of whole broiler carcasses, Experiments 7 and 8 Treatment concentration NaOH
KOH
Experiment 7 Solids
(M) 2.0 1.5 0.5 0.0
Protein
24.40B 25.04B 36.16A 36.04A
Growth
pH
Solids
2
(%) 0.0 0.5 1.5 2.0
Experiment 8
(+/−) 1.93B 2.26B 3.83A 4.55A
− − − −
23.93B 24.50B 35.10A 35.47A
0.20
0.17
Means with no common superscripts within columns differ significantly (P < 0.01). Means of nine observations. 2 Growth (+), no growth (−); observed aerobic plate growth at 72 h. A,B 1
pH
(+/−) 1.86B 2.21B 3.65A 4.29A
(SEM) 0.22
Growth 2
(%) 14.0 14.0 14.0 14.0
(SEM) 0.26
Protein
− − − −
14.0 14.0 14.0 14.0
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ton and traces of digestive organs were found, but they were extremely soft and appeared to have been thoroughly diffused by the solution. For all of these treatments, the carcasses were hydrolyzed to such an extensive degree that when stirred, there was no distinction between solution solids and carcass. All solutions maintained initial pH values greater than the endpoint measurement of the pH meter (pH >14.0). No decline in pH was observed in any of the solutions. Odor was characterized as primarily chemical or soap, with secondary ammonia undertones. A crude saponified product, presumed to be from the subcutaneous fat reacting with the alkaline hydroxides, was formed and floated on the surface of all undisturbed solutions. No intact feathers were visible in the emulsified solutions. Solution solids and protein were significantly increased from the 2.0 M KOH and the 1.5 M KOH with 0.5 M NaOH treatments compared with the 2.0 M NaOH and 1.5 M NaOH with 0.5 M KOH solutions in both experiments (Table 5).
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TABLE 6. Solution solids, protein composition, and solution pH of different ratios of 2.0 molar sodium hydroxide solution1 to carcass weight after 60 d treatment Item
Solids
Protein
pH
4.24A 3.52B 1.85C 1.18D 0.53
13.5 13.8 14.0 14.0
(%) NaOH:carcass ratio2 1:1 2:1 3:1 4:1 SEM
41.18A 33.73B 20.45C 12.34D 0.89
A–D Means with no common superscripts within columns differ significantly (P < 0.01). 1 Means of nine observations. 2 Ratio of 2.0 molar sodium hydroxide solution to carcass by weight.
Microscopic Evaluation Samples of solution and carcasses were examined visually for presence of feathers. Only those solutions and carcasses that were deemed to be visually free of feathers or remnants of feathers were sampled and inspected microscopically (10× and 40× magnification) for traces of intact feather fragments and other biological structures, such as tissue cells or insects. Samples from the 10-d treatment in 1.9 M NaOH of Experiments 4 and 5 contained microscopically visible feather remnants. Examination of the 10-d KOH solutions of 1.9 and 2.0, and 1.5 M with 0.5 M NaOH were negative for traces of feather, pests, and intact tissue cells. Solution and carcass samples from 10-d treatment with NaOH at 2.0 M and 1.5 M with 0.5 M KOH concentrations were negative for feathers, insects, and other biologically recognizable intact structures under microscopic examination. Samples from the solution-to-carcass ratio treatments were examined after 60 d and found to be negative for feather or other detectable structures for all ratio treatments. Examination of the samples was hindered by the concentration of crudely saponified fat in the lower stocking ratio samples and may have masked minute feather particles.
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Cole-Parmer Instrument Company, Niles, IL 60714. Delta Distributors, Houston, TX 77047.
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Alkaline hydroxide solutions hydrolyzed and preserved whole mature broiler carcasses with feathers. The research identified the basic parameters for effective preservative solutions that simultaneously degraded feathers and preserved the carcass. Effectiveness was related to visible feather and carcass solubilization, absence of putrefactive odors, inhibition of bacterial growth, and solids content of the alkaline solutions. Treatments of 2.0 M KOH and 1.5 M KOH with 0.5 M NaOH produced the highest degree of carcass degradation at 10 d without visible putrefaction; NaOH produced similar results at 1.9, 2.0, and 1.5 M with 0.5 M KOH. These concentrations hydrolyzed all feathers, diffused throughout the carcass, and produced adequate preservation to prevent putrefaction through 10 d. The NaOH inhibited bacteria in the solution at concentrations of 0.72 M, whereas carcass bacteria were not recovered at 1.9 M after 10 d. At a 1:1 ratio (wt:wt) of 2.0 M NaOH solution to whole broiler carcass, individual carcasses were maintained for more than 60 d without putrefaction. Analysis of costs to provide alkaline preservation for an individual broiler production unit was conducted using calculations based on 2.0 M NaOH aqueous solution in a 1:1 ratio (wt:wt) with broiler mortalities. Assuming an average mortality of 0.1% daily over 49 d, a flock of 25,000 broilers will produce 1,134 kg (2,500 lbs) of mortality (Blake et al., 1990). A poultry production unit of four houses, each with a 25,000-broiler capacity, would generate 4,537 kg (10,000 lbs) total mortality over a 49-d growout period. An equivalent amount (wt:wt) of 2.0 M NaOH solution would be required. The total mortality and solution weight would then equal 9,074 kg (20,000 lbs). Assuming that alkaline solution and carcasses will have a density equal to or greater than water, 9,074 kg (20,000 pounds) of alkaline solution and mortalities would, at most, require a container of 9,074 L (2,398 gal). A fully enclosed top-loading tank with 9,462 L (2,500 gal) capacity, manufactured from food grade-polyethylene, would have an estimated cost of $1,300.00.7 To amortize tank costs over 8 yr and 48 flocks, the tank cost per flock will equal $27.08. To produce the 4,537 kg (10,000 lbs) of 2.0 M NaOH solution would require 377 kg (830 lbs) of NaOH. Purchase of NaOH (97% purity) in bulk would cost $0.88/kg ($0.40/lb) for a total 49-d cost of $332.00.8 Therefore, estimated costs (excluding cost of water) to preserve 4,537 kg (10,000 lbs) of mortality over a 49-d period equal $359.08, or $0.0791 per kg ($0.0359/lb), of mortality. These costs are lower than estimates projected by Crews et al. (1995) for a 100,000-broiler production unit utilizing refrigeration, incineration, large-bin composting, or fermentation. One of the primary areas of research necessary prior to implementation of an alkaline preservation treatment for poultry mortalities is its effectiveness when utilized in preserving multiple carcass batches under actual production conditions. Development and integration of onfarm holding limits and scheduling of the preserved mate-
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Bacterial growth were not observed from samples of the solutions and skin at the 1.4 and 1.9 M treatments. The 0.48, 0.72, 0.97, and 1.2 M solutions of NaOH produced some observable microbial growth from samples of skin and intestine, but not from all samples of duplicate experiments. Solution samples from the 0.48 M NaOH treatments produced aerobic growth, whereas 0.72, 0.97, and 1.2 M solutions were negative. In duplicate experiments consisting of 2.0 M KOH, 1.5 M KOH with 0.5 M NaOH, 2.0 M NaOH, and 1.5 M NaOH with 0.5 M KOH, no viable bacterial growth were observed from any of the solutions (Table 5). Skin and intestine samples were not retrieved due to the high degree of chemical degradation to the carcasses.
DISCUSSION
PRESERVATION OF BROILER CARCASSES
rial for nutrient recovery will need to be planned. Equipment for dumping or pumping of tanks, or the exchange of full holding tanks for empty tanks will need to be acquired. Factors for future consideration include the need for research into the processing necessary for nutrient recovery and neutralization of the excess alkaline content of the preserved poultry.
REFERENCES
Ayres, J. C., J. O. Mundt, and W. E. Sandine, 1980. Chemicals in foods. Pages 123–144 in: Microbiology of Foods. W. H. Freeman and Co., San Francisco, CA. Blake, J. P., M. F. Cook, and D. Reynolds, 1990. Dry extrusion of poultry processing plant wastes and poultry farm mortalities. Pages 319–327 in: Proceedings of the Sixth International Symposium on Agricultural and Food Processing Wastes. American Society of Agricultural Engineers, St. Joseph, MI. Crews, J. R., J. O. Donald, and J. P. Blake, 1995. An economic evaluation of dead bird disposal systems. Circular ANR-914. Alabama Cooperative Extension Service, Auburn University, Auburn, AL. Latshaw, J. D., 1990. Quality of feather meal as affected by feather processing conditions. Poultry Sci. 69:953–958. Masters, P. M., and M. Friedman, 1979. Racemization of amino acids in alkali-treated food proteins. J. Agric. Food Chem. 27:507–511. Myers, E. G., 1992. Soaps and detergents. Pages 149–176 in: Inedible Meat By-Products. Vol. 8. A. M. Pearson and T. R. Dutson, ed. Elsevier Science Publishers Ltd., Barking, Essex, England.
Downloaded from http://ps.oxfordjournals.org/ at University of Pennsylvania Library on June 29, 2015
AOAC, 1984. Official Methods of Analysis. 14th ed. Washington, DC. Association of American Feed Control Officials, 1994. Official Publication. West Virginia Department of Agriculture, Charleston, WV. Atlas, R. M., 1984. Microbiology Fundamentals and Applications. Macmillan Publishing Co., New York, NY.
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