Stabilization of poultry processing by-products and poultry carcasses through direct chemical acidification

Bioresource Technology52 (1995) 69-77

0960-8524(95)00009-7

ELSEVIER

© 1995 Elsevier Science Limited Printed in Great Britain. All rights reserved 0960-8524/95/$9.50

STABILIZATION OF POULTRY PROCESSING BY-PRODUCTS AND POULTRY CARCASSES T H R O U G H DIRECT CHEMICAL ACIDIFICATION T i a n d e Cai, a* O s c a r C. P a n c o r b o , a* W i l l i a m C. M e r k a , b J e a n E. S a n d e r c & H a r o l d M. B a r n h a r t a ~

"Department of Food Science and Technology, bDepartment of Poultry Science and "Departmentof Avian Medicine, University of Georgia, Athens, Georgia 30602, USA (Received 19 August 1994; revised version received 10 January 1995; accepted 11 January 1995)

Therefore, poultry offal and blood must be prevented from putrefaction, to avoid odor problems and reduce nutrient losses while truck-load quantities are accumulated. Poultry carcasses on farms are also difficult to dispose of. Incineration and burial in a pit can pollute air and ground-water (Dobbins, 1990). Rendering and landfilling may be restricted by state and local regulations that prohibit diseased carcass movement across county lines (Dobbins, 1990). Transportation to an incineration or rendering plant may be cost-prohibitive. Carcass disposal costs could be offset by nutrient recovery if carcasses can be stabilized, accumulated and transported in truckload quantities to a rendering plant. Acidification is a potential method for preserving inedible animal parts and fish wastes (Norman et al., 1979; Raa & Gildberg, 1982; Divakaran & Sawa, 1986). Commercial production of fish silage produced by acidification has been practised for decades in Denmark (Raa & Gildberg, 1982). Formic acid- (Divakaran, 1987) treated cattle blood and offal and formic acid-treated poultry offal (Machin et al., 1984) are safe for incorporation into animal diets. Theoretically, any biological material may be preserved without microbial deterioration when treated with an adequate concentration of acid(s). However, acids may adversely alter the material physically and/ or chemically. In order for such a process to be commercially feasible, it should be easily implementable and economical. The present study emphasized the technical and economic feasibility of direct acidification in stabilizing chicken carcasses and chicken-processing offal and blood. Acidification with various acids at different concentrations was investigated with laboratory experiments. Field experiments were then conducted to verify the laboratory findings based on the microbiological and

Abstract

Laboratory and field experiments were conducted to test the feasibility of using chemical acidification for stabilizing poultry-processing offal and blood and poultry carcasses. Acidification of the ground poultry materials with 2% (w/w) of 90% formic acid was the most economical method for preventing putrefactive changes and did not adversely affect crude protein and fat content. The acid-preserved offal and carcasses were stable semi-liquid~solid products with pHs of 4.0-4.2. When stored for 28 days at 30°C, the acidified offal and carcass products had approximately 67 and 62% moisture, 12 and 14% protein, 17 and 15% fat, and 0"16 and 0"23% ammonia, respectively. Several problems were identified, however, when the acid-treated offal was heat-processed to produce a dry feed meal. Key words: Poultry, carcasses, offal, waste, acidification, stabilization, preservation. INTRODUCTION

Poultry-processing offal and blood represent a major by-product problem for the poultry industry. Currently, in the United States, most of the poultry by-products are transported to rendering plants for processing into dry animal feed supplements. However, raw poultry offal and blood putrefy rapidly and transportation costs prevent small quantities produced in small plants from being processed, unless accumulated and transported as a full truck-load. *Present address: Department of Food and Nutrition, North Dakota State University, Fargo, ND 58105, USA. *Present address: Division of Environmental Analysis, Senator William X. Wall Experiment Station, Massachusetts Department of Environmental Protection, 37 Shattuck Street, Lawrence, MA 01843, USA. '~Author to whom correspondence should be addressed. 69

70

T. Cai, O. C. Pancorbo, W. C Merka, J. E. Sander, H. M. Bamhart

chemical composition of the acidified poultry-processing by-products and carcasses.

METHODS

by subtracting ammonia nitrogen from total Kjeldahl nitrogen and multiplying the results by 6.25. Acidity (pH) was measured with a Corning pH meter equipped with a fiat surface combination electrode.

Acids

Microbiological analysis

The following acids were used: folic acid, 90% (BP Chemicals Inc., Hackettstown, NJ); acetic acid, 100% (BP Chemicals); propionic acid, 100% (Eastman Chemical Co., Kingsport, TN); lactic acid, 85% (J.T. Baker, Phillipsburg, NJ); phosphoric acid, 75% and 85% (Monsanto Co., St. Louis, MO); sulfuric acid, 95-98% (J.T. Baker); and peracetic acid, 32% in diluted acetic acid (Aldrich Chemical Co., Milwaukee, WI). Acids were diluted with reagent water (1:3 by weight) before use. The final acid percentages used in following experiments were based on the original stock acid concentrations and the wet weight of the poultry by-products or carcasses.

Samples were blended with 1% buffered peptone water (Thomason et al., 1977), neutralized to pH 7, and then serially-diluted using 0.1% peptone water (APHA, 1989). Fecal coliforms and fecal streptococci were enumerated by spreading 0.1 ml of diluted samples on m-FC agar and KF Streptococcus agar plates, respectively (APHA, 1989). A 3-tube MPN method was adopted to enumerate Salmonella (APHA, 1989) as follows. Buffered peptone water and tetrathionate broth were used as pre-enrichment and enrichment media, respectively. Selective media, brilliant-green agar (APHA, 1989), brilliant-green novobiocin agar (Tate et al., 1990), modified xylose lysine brilliant-green agar (Hussong et al., 1984), xylose lysine tergitol 4 agar (Miller et al., 1991), and modified semi-solid Rappaport-Vassiliadis enrichment medium (De Smedt et al., 1986), were used to recover salmonellae. The biochemical confirmation of Salmonella spp. was accomplished on triple-sugar iron agar, lysine iron agar, and six-sugar fermentation broths (Cox & Williams, 1976) and/or by using Micro-ID Enterobacteriaceae system kits (Organon Teknika Corp.). If either or both confirmation methods gave a positive result, then the MPN tube was considered positive.

Laboratory experiments Poultry-processing offal (viscera, feet and heads) and dead-on-arrival poultry carcasses were obtained from a local broiler processing plant. Whole carcasses (axe-chopped before grinding) and offal were ground separately in a laboratory Enterprise meat grinder with a 12-mm dicing plate. The ground carcasses and offal were mixed with diluted acid(s) to a pH of 3 or 4. The mixtures (1.5 kg) were then placed in a partially-sealed plastic container and stored at room temperature (21+2°C) or 30°C for up to 60 days, during which samples were taken for analysis. Control samples (untreated samples) were run for comparisons.

Field experiments Both the broiler-processing offal and the bloodoffal mixture in the normal ratio (about 1:4) produced per bird were obtained as received at a local rendering plant. The offal was ground and mixed with a diluted acid as described above. Dead laying-hen carcasses obtained from a local farm were ground with a G.P.R. 20 in. poultry grinder (Animal Health Sales, Inc., Selbyville, DE) and mixed with 2% (wAv) of 90% formic acid. Control samples were also tested for comparisons. A 38-40 kg batch of acidified or control samples was then stored in a partially-sealed plastic barrel at 18 or 30°C for 8 days. After the storage period, the samples were dried in a swept surface heat exchanger under 690 kPa (100 psi) for 30 min to evaluate product characteristics. Samples were also taken during storage for chemical and microbiological analysis.

Chemical analysis Crude protein, crude fat, moisture, ash, and ammonia nitrogen in samples were determined by AOAC Official Methods 24.038, 24.005a, 24.003b, and 24.009 (1984) and APHA Standard Method 4500E (1989), respectively. Protein content was calculated

Data analysis Experimental data were analyzed statistically by the method of the general linear model using analysis of variance and Duncan's multiple range test (SAS Institute, 1988). Significance was defined as probabilities of 0.05 or less. Unless otherwise noted, all data presented are on a wet weight basis. RESULTS AND DISCUSSION

Laboratory experiments All acids, except peracetic acid, were added to the ground poultry waste to achieve a pH of 3 or 4. The amounts of acid required to obtain these initial pHs varied with the type of acid (i.e. with the acid's dissociation constant) (Table 1). The pH in most treated samples changed during storage at room temperature (Fig. 1). The changes were more rapid during the first 24 h after acidification as acid penetrated into offal tissue and the buffering capacity of offal substantially increased the pH. Acidification with 10% acetic acid, 1.5% formic acid, 4.8% lactic acid, or 3"8% propionic acid stabilized the offal pH below 4.5. Offal treated with 0.4% formic acid, 1.2% acetic acid, 0.5% or less sulfuric acid, 1.3% lactic acid, 0'5% or less peracetic acid, or 0.7% phosphoric acid putrefied within 36-108 h of storage at room temperature. Untreated offal (control) spoiled

Acidification of poultry waste

71

Table 1. Cost of acid treatment and pH of acidified offal stored for 144 h at 21_+2"C (lab thai)

Acid

Formic Formic Acetic Acetic Propionic Lactic Lactic Sulfuric Sulfuric Phosphoric Phosphoric Peracetic Peracetic Control

Purity (%) 90 90 100 100 100 85 85 95 95 85 85 32 32 0

Price" ($/kg) 0-90 0.90 1.12 1.12 1.85 2.00 2.00 1.28 1.28 1.07 1'07 22.09 22.09 0.00

Acid used in offal (%, w/w)

Acid cost ($/1000 kg offal)

Offal pH b 0h

144 h

0.4 1"5 1.2 10.0 3"8 1.3 4-8 0"2 0.5 0.8 1"5 0-1 0.5 0.0

3-60 13-50 13.44 112.00 70.30 26-00 96"00 2"56 6.40 8.56 16"05 22.09 110.45 0.00

4-00 4-0-02 3.01 4-0.02 3-98 4-0-03 3.00 4-0.02 3.80 4-0.03 4.00 4-0.02 3.00 4-0-03 4.00 4-0"02 2-98 4-0-03 4.00 4-0-02 3"00 4-0"03 3.65 4-0-04 4-75 4-0-04 6-20 4-0.02

6.07 + 0.02 4.03 + 0.04' 5.17_0.02 3-72 + 0.02' 4.38 + 0.04" 5-88 + 0.04 4.05 + 0.07" 6.40 4-0.07 6.33 + 0.04 5.98 + 0-04 4.78 4-0-03 6.48 4-0.04 5.86 4-0.02 6.40 4-0-03

on sale quantity of 200-340 kg, except for peracetic acid based on a quantity of 45 kg, in US dollars. hMeans + standard deviation of two treatment replications. 'Indicates pH (below 4.5) significantly (P < 0.05) lower than those without a superscript. "Based

within 24 h of storage. All putrid samples had a pH above 5-2 while stabilized offal had a pH below 4-5 after 144 h (Table 1). Offal immediately after acidification was very viscous, particularly at high acid levels, but its consistency decreased with storage age. Cost estimates (Table 1) showed that acidification with 1.5% (w/w) of 90% formic acid was the least expensive (US$13.50/1000 kg offal) among the effective stabilization treatments (i.e. endpoint pH of 4.5 or less). Sulfuric acid may be effective at 3%, as reported by Divakaran and Sawa (1986) in pickling cattle offal. However, this treatment would cost approximately US$38/1000 kg offal and cause handling problems (e.g. acid-fast equipment and neutralization before processing or feeding to animals; Raa & Gildberg, 1982). Treatment of offal and carcasses with the mixture of 0-75% (v/w) formic acid and 0-75% (v/w) propionic acid did not stabilize the pH of these wastes during storage at 21°C (Table 2), although this treatment was effective for fish and fish wastes (Johnsen & Skrede, 1981). Whether the discrepancy was due to the different biological materials (i.e. differences in buffering capacity and microflora) or storage time is uncertain. Our acidified chicken offal pH increased from 3-8 to 5.1 and carcass pH rose from 4.1 to 5.1 during 21 days of storage (Table 2). Ammonia nitrogen approximately doubled after 21 days of storage, reaching 4.3-4.5 g/kg. A significant reduction in fat occurred during storage in these trials (Table 2). Carcass protein content also decreased significantly after 8 days. These offal and carcass treatments putrefied after 21-28 days when their pHs had increased to 5.1-5.5. When stored at 30°C for up to 60 days, offal acidified with mixed acids [0.75% (v/w) formic acid and 0.75% (v/w) propionic acid], 2% (w/w) formic acid,

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The pH of acid-preserved chicken offal during storage at room temperature (lab trial).

or 2.5% (w/w) formic acid yielded a stable product with a final pH of 4.4 or less [Fig. 2(a), Table 3]. No significant differences in moisture, protein, fat and ammonia nitrogen, on a dry weight basis, were found between the acid treatments for offal stored

T. Cai, O. C. Pancorbo, W. C. Merka, J. E. Sander, H. M. Barnhart

72

Table 2. Moisture, protein, fat, ammonia nitrogen and pH of broiler offal and carcasses acidified with 0.75% (v/w) formic acid and 0-75% (v/w) propionic acid during storage at 21°C (lab trial) °

Waste sample Offal

Storage (day)

Moisture (%)

Protein (%)

Fat (%)

NH3-N (g/kg)

pH

0

67-7 ( _ 1.6)b

11-6 ( _ 0.9) h 12.0 ( _ 0.7) h 11.3 ( _ 0.6) b . 16.5 ( + 0.8) h 13-9 ( + 0"9)' 14.1 ( + 0-2)' .

15.4 ( + 0.6) b 13.1 ( + 0-4)" 14-1 ( _ 0.3)"

2.3 ( +_0-8)h 2.5 ( _ 0-3)h 4.3 ( + 0.3)"

15.6 ( _ 1.2)b 11-8 ( + 0.4)" 11.7 ( _ 0-7)c

2.4 ( + 0.4) b 2.2 ( + 0-3)b 4-5 ( _ 0.3) c

3.75 ( + 0-09)h 4.65 ( _ 0.09)' 5.14 ( +_0.13) d 5.46 4.09 ( + 0.09) h 4.62 ( + 0.09)' 5.14 ( _ 0.14) d 5.5 (+0.15)"

8 21 Carcass

28 0 8 21 28

69.5

( + 0.4) h 70.7 ( + 0.3) b . 61.8 ( + 1-6)b 62.2 ( + 3.7) h 64-8 ( + 1.5)h .

.

.

.

.

"Means (+_standard deviation of two replications) within a column with different superscripts (b-e) are significantly (P<0-05) different for each type of waste. for 28 days (Table 3). Hence, the mixed acid treatment preserved offal at 30°C equally as well as 2% formic acid, although the former yielded a pH 0.4 units higher than the latter after 28 days of storage (Table 3). These acid treatments liquefied the offal at 30°C after storage for 2 weeks. Offal acidified with 2% or more formic acid had a mild acid, pungent smell after storage for 8 days at 30°C. It was a semi-liquid, stable product which could be separated into a lipid phase, an aqueous soluble phase, and a solid phase by centrifugation, as described for fish silage production (Johsen & Skrede, 1981; Raa & Gildberg, 1982). Acidification with the mixed acid stabilized offal but not carcasses (Fig. 2, Table 3). The different results were probably due to the different compositions of these materials. The pH of mixed acid treated carcasses increased sharply after 14 days, and the carcasses became putrid thereafter. Carcasses treated with 2% or more formic acid were stable and their pHs remained at or below 4.2 over 60 days [Fig. 2(b)]. The ammonia nitrogen and pH of formic acid-preserved carcasses were significantly lower than those of the mixed acids (Table 3). The formic acid treatment contained significantly higher protein content than that of the mixed acids. Protein loss in the latter treatment resulted in the higher production of ammonia nitrogen (Table 3). The production of ammonia partly accounted for the significantly higher moisture content in the mixed acid treatment since volatile compounds (e.g. NH3) are lost during moisture analysis. Carcasses also liquefied more slowly than offal, probably due to the lower concentration of intestinal tract acid enzymes in whole carcasses. As fish intestinal enzymes were responsible for autolysis in fish silage (Raa & Gildberg, 1982), chicken carcass intestinal enzymes accounted for autolysis and liquefaction in acidified carcasses. Carcass liquefaction was observed after 3 weeks of

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70

Time (days) Fig. 2. The pH of (a) chicken offal and (b) carcasses acidified with an initial concentration of 2.0% (w/w) formic acid (FA2.0), 2.5% (w/w) formic acid (FA2.5), or 1.5% (v/w) mixture of 0.75% formic and 0.75% propionic acids (FP1.5) during storage at 30°C (lab trial).

storage at 30°C Overall, carcasses treated with 2% or more formic acid at 30°C were a stable product. No putrid odors nor visible fungal growth or blooms were found when these treatments were stored for 60 days. Field experiments Formic acid, propionic acid, and phosphoric acid were used in field studies because these acids were more effective, economical and/or safer to use than acetic, lactic, peracetic and sulfuric acids based on

Acidification of poultry waste

73

Table 3. Moisture, protein, fat, ammonia nitrogen and pH of acidified offal and carcasses stored 28 days at 30°C (lab trial) °

Waste sample

Acid added h

Moisture (%) c

Protein (%)d

Fat (%)a

NH3-N (g/kg)d

pH

Offal

FA

67.4 (+ 2.7)" 66.0 (+0.7)" 61.9 (+0-1)" 67.2 ( + 1.3)t

32.7 (+2.1) " 32.9 (+2.3) e 32.2 (___2.8)" 13.2 ( + bOy

54.3 (+0.1) e 56.5 (+3.1) e 40.5 (+2.1) e 45.6 ( + 3-1)~

5.1 (+0-5) e 4.9 (+0.7)" 6.0 (+ 1.3)" 30.1 ( + 3.3) r

3-97 (+0.03)" 4.45 (+0.01) r 4.21 (+ 0.01)" 7.55 ( + 0.07)r

FP Carcass

FA FP

"Means (+standard deviation of two treatment replications) within a column with different superscripts (e and f ) are significantly (P< 0-05) different for each type of waste. bFA=2% (w/w) formic acid; FP=0.75% (v/w) formic acid and 0-75% (v/w) propionic acid. ' Wet weight basis. dDry weight basis.

the laboratory studies discussed above. Acidification with 2% formic acid or 4% propionic acid stabilized offal for 8 days, but the treatments with 0.9% or less formic acid, 1% propionic acid or 1.6% or less phosphoric acid were not effective as indicated by pH and ammonia and protein contents (Table 4). Offal treated with 2% formic acid, 2% propionic acid or 4% propionic acid had relatively stable protein and fat contents, whereas other treatments were ineffective, leading to putrefaction, protein loss, ammonia production, and pH elevation to 5.0 or more after 8 days of storage (Table 4). Typical analysis of dried (cooked) offal showed that the protein content increased with the acid concentration (Fig. 3). Protein content in dried, 2% formic or 4% propionic acid treated offal was approximately 34%, while protein content in dried, spoiled treatments was between 26 and 31%, representing a 9-23% protein loss on a dry weight basis. These data further support the findings in uncooked offal as discussed previously. However, all cooked acidified treatments were dark in color after rendering for 30 min at 690 kPa. It appeared that the color was darker with increasing acid concentration. Moreover, it was difficult to press out the fat from the hot solids after cooking. Furthermore, a pungent, acid smell was emitted during cooking, which may require better ventilation or condensation before acid-preserved offal can be processed into poultry meal on a large scale. One possible solution is to separate the solid phase (consisting of protein and fat) from the aqueous phase (containing fat, water and their soluble hydrolysate) in the acid-treated offal by pressing or centrifugation before cooking. This will reduce cooking time for drying and may diminish the development of the dark color. However, soluble proteins in the aqueous phase may be lost. Another solution, perhaps a more practical way, is to mix a small amount of the acidtreated material with fresh offal prior to rendering. Undried acid-preserved offal may also be used

directly as a feed ingredient, as reported by Machin et al. (1984; 1986) and Asgard and Austreng (1986), However, the bulky volume of the undried offal will make storage, transportation and handling difficult. Because formic acid and propionic acid were more effective in stabilizing offal than phosphoric acid, as described above, another trial was conducted to test the feasibility of using these acids to preserve a broiler processing blood-offal mixture. The higher level (1"6%) of phosphoric acid was also included in this study. Results indicated that 2% formic acid stabilized the blood-offal mixture more effectively than the other acid treatments (Table 5). The 2% formic acid treatment had a pH of 4.5 at 8 days while the others were putrid at pH 5.5 or higher. The untreated (control) sample spoiled and, as a result, protein and fat contents decreased and ammonia concentration increased. Ineffective treatments with 0-9% or less formic acid, 1% propionic acid or 1.6% phosphoric acid resulted in higher ammonia and lower protein and/or fat concentrations in the samples at 8 days (Table 5). The blood-offal mixture had a higher initial pH than offal alone with the same acid treatments (Tables 4 and 5), suggesting that the blood-offal mixture had a higher buffering capacity, requiring more acid for stabilization. Numbers of Salmonella spp. in the acidified and untreated blood-offal mixtures declined during storage (Table 6). Salmonella spp. were not detected in any of the acidified blood-offal samples after storage for 8 days. Fecal coliforms and fecal streptococci in acidified blood-offal mixtures were relatively more tolerant to acidification than Sa/mopaella. An approximate two-log reduction in fecal coliforms and no reduction in fecal streptococci occurred during storage, except for the treatment with 2% formic acid (Table 6). The 2% formic acid treatment had lower bacterial counts; thereby bolstering the conclusion that this acid treatment was more effective in inhibiting bacteria. Fecal coliforms and fecal strepto-

T. Cai, O. C. Pancorbo, W.. C. Merka, J. E. Sander, H. M. Barnhart

74

Table 4..Typical analysis of moisture, protein, fat, ash, ammonia nitrogen and pH of acidified broiler-offal stored at 18-!-_2"C (field trial) Acid treatment

Day

Moisture (%)

Protein (%)

Fat (%)

Ash (%)

NH3-N (g/kg)

pH

0.4% Formic

0 2 4 8

67.5 69.1 68.6 71.0

11.1 10.1 9.5 8.3

18.1 18.2 19.2 19.2

1.5 1.2 1.3 1.1

0:3 0.6 1.3 3.6

4.1 5.1 5.6 6.1

0.9% Formic

0 2 4 8

69.2 68.5 68.0 68.6

11.5 11.2 11.1 10.1

18.9 18.7 19.6 19.3

1-4 1-2 1.4 1.2

0.2 0.3 0.4 2.0

~3.4 4.3 4.5 5.0

2% Formic

0 2 4 8

64.4 64-0 64-7 64.2

10.3 10.0 10.2 10.4

22-7 22-6 23.0 22.9

1.2 1.2 1.2 1.1

0.1 0.2 0.2 0-2

3.1 3.7 3.7 3.8"

1% Proplonic

0 2 4 8

64.4 64.5 65-7 67.8

11.6 11.8 10-5 9.6

21.2 22.9 21.6 21.9

1.5 1.3 1.1 1.1

0.2 0-5 0-7 1.6

4.4 5.0 5.1 5.4

2% Proplonic

0 2 4 8

66.5 66-5 66.0 67.0

10.7 10.6 10.5 10.6

19.8 20.3 20-9 20.1

1.1 1.2 1.2 1.1

0-2 0.3 0.3 0.4

4.3 4.6 4.7 4-8

4% Proplonic

0 2 4 8

67.9 67-0 66-8 66.5

10.7 10.7 10.6 9.9

18.9 18.1 20-7 20-7

1.1 1.2 1.3 1-2

0.2 0.2 0.2 0-3

4.0 4.4 4.4 4-4"

0.8% Phosphoric

0 2 4 8

65.2 67.3 67.0 68-4

11.7 10-8 10-4 10.1

20.5 20.3 20.2 20.5

1.8 1.5 1.5 1.4

0.2 2.0 2-3 4.0

4.0 5.2 6-0 6.2

1.2% Phosphoric

0 2 4 8

66.4 67.2 66.9 68.3

12.0 11.5 10.4 10-1

22.3 19.6 20.6 17.5

1.7 1.7 1.6 1-0

0.2 1.0 2.4 4.1

3-5 4.7 5.7 6.2

1.6% Phosphoric

0 2 4 8

66.0 66.1 65.6 67-8

11.2 11.0 10.5 9.3

19.1 18-8 19-1 19.0

2.9 2.9 2.4 2.4

0-2 0-5 1.0 4.4

3.0 4.2 5.3 6-1

Control (noacid)

0 2 4 8

65.9 69.4 70.0 70.3

10.6 8.8 8.7 8.3

22.0 18.9 18-1 17.8

1.0 1.0 1.2 1-0

0.5 3.6 4.3 5.0

6-2 6.3 6-3 6.3

"Indicates satisfactory stabilization for 8 days. cocci were not completely eliminated, however, remaining at 104-105 CFU/g in the acidified bloodoffal mixture (Table 6), presumably because of blood buffering capacity. Acidification of chopped chicken carcasses with 2% formic acid showed the protein, fat and pH were relatively stable during storage for 8 days at 30°C (Table 7). Although ammonia nitrogen increased to 0.06% after 8 days, no marked putrefaction occurred. The endpoint pH was 4.3, 0.4 units higher than the initial value (Table 7). It should be noted that a

coarse poultry grinding machine capable of adoption by farmers was used in these field experiments. The coarser particle size contributed to higher pH values than those observed in our laboratory study [Fig. 2(b)]. Fecal coliforms and fecal streptococci in carcasses acidified with 2% formic acid in the field study were reduced from 108 CFU/g to 104-105 CFU/g during storage for 8 days (raw data not shown). There was a three-log reduction of fecal coliforms and fecal streptococci in acid-preserved carcasses as compared

Acidification of poultry waste to the control. Salmonella spp. were not detected (i.e. less than 30 MPN/100 g) in the acidified carcasses at the end o f the storage period (raw data not shown).

75

In conclusion, l a b o r a t o r y e x p e r i m e n t s showed that effective stabilization of g r o u n d chicken offal for 8 days could be o b t a i n e d by acidification with 1.5% (w/w) formic acid, 3.8% (w/w) propionic acid, or

Table 5. "l~pical analysis of moisture, protein, fat, ash, ammonia nitrogen and pH of acidified broiler-offal (1:4) mixture stored at 18___2°C (field trial) Acid treatment 0.4% Formic 0.9% Formic 2% Formic 1% Propionic 2% Propionic 1.6% Phosphoric Control (no acid)

Day

Moisture (%)

Protein (%)

Fat (%)

Ash (%)

NH3-N (g/kg)

pH

0 8 0 8 0 8 0 8 0 8 0 8 0 8

72-4 75"2 72.4 72.4 71"6 71.2 71-0 75"7 70.8 72.8 69.3 73.7 70.3 77.3

11.5 10"8 12.1 10.1 13.1 12.6 12.1 11.4 11.9 11.6 12.7 9.8 11.7 9.7

12.3 9-4 12.8 13"3 13.1 14.1 12.3 9.6 13.6 14.0 12.5 13.3 12-9 9.3

3"3 1"7 1.7 1"5 1.4 2"3 2.9 1.5 1.4 1.3 2.7 2.8 2.2 1.5

0"4 4.3 0.3 3'1 0'2 1.1 0.4 2.9 0.3 2.2 0.3 3.3 0.7 4.7

4"8 6.4 4.2 6.1 3.8 4.5" 4.7 6"1 4.5 5.5 4-3 6-2 6.2 6-4

"Indicates satisfactory stabilization for 8 days. Table 6. Fecal eoliforms, fecal streptococci and Sa/mone//a spp. in acidified blood-offal (1:4) mixture stored at 18-+2"C (field trial) Acid treatment

Day

Samonella

Fecal coliforms (log CFU/g)"

Fecal streptococci (log CFU/g)"

spp. (log MPN/100 g)"

0.4% Formic

0 2 4 8

7-88 + 0.10 8-38+0.13 7.26 + 0.08 5.92 -+0.05

6.92 + 0.07 7.39+0.14 7.04 __+0.10 6.99 4-_0.03

2.84 + 0-08 2.95+0.10 < 1.48 < 1.48

0.9% Formic

0 2 4 8

8.64+0-17 8-28 _+0.07 7.10-+ 0-09 6.61 + 0.06

6.48+0.13 7.17 + 0.09 7.03 + 0-07 6.96-+ 0.05

3.18+0.09 2.95 -+0-07 2.48 + 0.00 < 1.49

2% Formic

0 2 4 8

6.28-+ 0.08 6.35 -+ 0.05 5.50 + 0.08 4.73 +0.04

6-36 + 0.06 6-52-+ 0-08 6-24 _ 0.10 5.41 -+0.03

2.85 + 0.07 < 1.48 < 1.48 < 1-48

1% Propionic

0 2 4 8

8.04+0.13 8.30_+ 0.07 7.01 + 0-14 6.92 -+0-03

6.55 +0.10 7.26___ 0.14 7.06 + 0.07 6-99 + 0-05

2.61 +0.08 2.48_ 0.01 < 1.48 < 1.48

2% Propionic

0 2 4 8

8.07+0-10 6-70 -+0.04 5-59 -+0.05 5.57 -+ 0-06

6.51 +0.04 6.36 ___0.05 5.87 ___0.03 6.07 + 0.10

2.61 -+0-07 < 1.48 < 1-48 < 1.49

1.6% Phosphoric

0 2 4 8

8.43 4- 0.09 8.65 -+0-07 7"56 -+ 0.10 6.35 -+0-08

6-73 -+0-07 8.06 -+0.14 7-38 _ 0.09 7.18+0.10

2.48 + 0.01 2.48 -+0.00 < 1-48 < 1.48

Control (no acid)

0 2 4 8

8.33 +0.13 9.11 _+0.09 8-42 _+0-07 6.86 4- 0-10

7.70__+0.05 7.93 + 0.07 7.75 _ 0-10 7.44 + 0.09

3.85 +0.07 2.85 _ 0.08 2.48 _ 0.01 2-48 -+0.02

Means + standard deviation of two replications.

76

T. Cat, O. C. Pancorbo, W. C. Merka, J. E. Sander, H. M. Bamhart

Table 7. "l~jpical analysis of moisture, protein, fat, ammonia nitrogen and pH of acidified laying-hen carcasses stored at 30°C (field trial)

Acid treatment

Day

Moisture (%)

Protein (%)

Fat (%)

Ash (%)

NH3-N (g/kg)

pH

0 4 8 0 4 8

63-0 65.3 65-0 63.3 64.2 65.3

19.0 18.1 18-6 20-8 19.0 18.2

9-2 10-0 8.9 9.4 11.8 12.2

6-5 4.0 3.1 5.8 2.8 3-8

0.3 0.4 0.6 0.9 9-2 11-3

3.9 4.3 4-3 6.3 6.6 6.9

2% Formic Control (no acid)

"-"

60

o E

50

E,

4O

o

30

o,

20

c '~

10

o.

0

'o o~

O

ming, Georgia, to the Research Foundation.

.911 21[

211 411

1.8~

hilliill ni? Formic

Propionic

Phosphoric

Acid Type and Concentration

Fig. 3. Effect of acid type and concentration on crude protein in dried, acidified poultry offal at 8 days of storage (field trial).

4.8% (v/w) lactic acid. Treatment of ground offal and carcasses with 2% (w/w) formic acid prevented their spoilage during storage for 60 days at 30°C. The end product was a semi-liquid, stable product with a pH of 4.5 or less. There were no putrefactive odors and no visible fungal growth in these products. Field studies confirmed that acidification of chicken offal, blood-offal mixture and carcasses with 2% (w/ w) formic acid preserved crude protein and fat. The cost of this acidification (US$18/1000 kg product) was the most economical of the effective acid treatments tested. The problems associated with the darker, brown color of the dried acidified offal, the acid odors released during cooking and the difficulty in pressing out the fat from solids after cooking have to be resolved if the acidified offal is to be processed as poultry meal. Mixing of a small proportion of acidified offal with fresh offal to produce a poultry meal may be a practical solution. Further work is also required to evaluate the nutritional quality of the acid-preserved product in more detail according to feed grade specifications and to assess possible toxic effects of formic acid when present in animal feeds. ACKNOWLEDGEMENTS

This work was supported by Grant No. 25-21-RC294-113 from Georgia Proteins, Inc., Cum-

University of

Georgia

REFERENCES

AOAC (1984). Official Methods of Analysis, 14th edn. Assoc. Official Analytical Chemists, Washington, DC. APHA (1989). Standard Methods for the Examination of Water and Wastewater, 17th edn. American Public Health Assoc., Washington, DC. Asgard, T. & Austreng, E. (1986). Blood, ensiled or frozen, as feed for salmonids. Aquaculture, 55 (4), 263-84. Cox, N. A. & Williams, J. E. (1976). A simplified biochemical system to screen Salmonella isolates from poultry for serotyping. Poultry Sci., 55 (5), 1968-71. De Smedt, J. M., Bolderdijf, R. F., Rappold, H. & Lauterschlaeger, D. (1986). Rapid Salmonella detection in foods by mobility enrichment on a modified semi-solid Rappaport-Vassiliadis medium. J. Food Prot., 49 (7), 510-14. Divakaran, S. (1987). An in vitro quality evauluation of slaughterhouse by-products preserved by pickling with sulfuric acid. Biol. Wastes, 19 (4) 281-6. Divakaran, S. & Sawa, T. R. (1986). Characteristics of slaughterhouse by-products preserved by pickling with inorganic acids. Agric. Wastes, 17, 67-75. Dobbins, C. N., Jr (1990). Dead bird disposal through the use of Lactobacillus fermentation (ensilage). Paper presented at the Southeastern Poultry and Egg Association Conference, Atlanta, GA, 11 September 1990. Hussong, D., Enriki, N. K. & Berge, W. D. (1984). Modified agar medium for detecting environmental salmonellae by the most-probable-number method. Appl. Environ. Microbiol., 48 (5), 1026-30. Johnsen, F. & Skrede, A. (1981). Evaluation of fish viscera silage as a feed resource. Acta Agric. Scand., 31, 21-8. Machin, D. H., Hector, D. A., Capper, B. S. & Carter, P. M. (1984). The utilization by broiler chickens of poultry offal hydrolyzed in formic acid. Animal Feed Sci. & Technol., 11, 247-59. Machin, D. H., Silverside, D. E., Hector, D. A. & Parr, W. H. (1986). The utilization by growing pigs of ruminant offal hydrolyzed in formic acid. Animal Feed Sci. & Technol., 15 (4), 273-84. Miller, R. G., Tate, C. R., Mallison, E. T. & Scherrer, J. A. (1991). Xylose-lysine-tergitol 4: an improved selective agar medium for the isolation of Salmonella. Poultry Sci., 70, 2429-32. Norman, G. A., Silverside, D., Hector, D. A. & Francis, S. (1979). The acid treatment of animal by-products. Trop. Sci., 21, 221-9. Raa, J. & Gildberg, A. (1982). Fish silage: a review. CRC Crit. Rev. Food Sci. Nutr., 16, 383-419. SAS Institute (1988). SAS/Stat User's Guide, Release 6.03 edn. SAS Institute Inc., Carry, NC.

Acidification of poultry waste Tate, C. R., Miller, R. G., Mallison, E. T. & Douglass, L. W. (1990). The isolation of salmonellae from poultry environmental samples by several enrichment procedures using plating media with and without novobiocin. Poultry Sci., 69, 721-6.

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Thomason, B. M., Dodd, D. J. & Cherry, W. B. (1977). Increased recovery of salmonellae from environmental samples enriched with buffered peptone water. Appl. Environ. Microbiol., 34 (3), 270-3.