i

CHARACTERIZATION AND FROZEN STORAGE STABILITY

OF COD MINCE SUBJECTED TO MECHANICAL SEPARATION

OF “SEALWORMS11 OR “CODWORMS”

by

Kermit D. Reppond and Jerry K. Babbitt

Kodiak Investigations--Utilization Research Division

Northwest Fisheries Science Center

National Oceanic and Atmospheric Administration

U.S. Department of Commerce

P.O. Box 1638

Kodiak, AK 99615

February 1991
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ABSTRACT

A Baader Model 694 Meat Separator and a Brown International Model 4000 Finisher were equally effective in producing

minced flesh from fillet trimmings of Pacific cod (Gadus macrocephalus) but only the mince from the Finisher was essentially

free of “sealworms” or “codworms.” Analysis for thaw drip, color,

protein, ash, moisture, and amines indicated that mince from both

machines had similar composition. Tests of sensory properties of

blocks of mince stored for up to 6 months at -18*C indicated no

differences with the exception of texture. Mechanical analysis of

texture confirmed that mince refined with the Finisher tended to

be firmer.
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1

INTRODUCTION

In 1987, almost 40 million pounds (18,200 metric tons) of

minced fish blocks worth over $27 million were imported into the

United States (O’Bannon 1988). These blocks are usually made from

the flesh of the codfishes (Gadidae) family and are mostly

processed into fish sticks. A significant part, if not all, of

these blocks could be produced domestically using Pacific cod

(Gadus macrocephalus) and walleye pollock (Theragra

chalcogramma), also known as Alaska pollock. Over 170 million

pounds (77,000 metric tons) of Pacific cod and 550 million pounds

of Alaska pollock (250,000 metric tons) were landed by U.S.

fisherman in 1987 (O’Bannon 1988). Domestic production of blocks

of minced flesh as the primary product from a fishery is limited

due to the low price of the blocks as compared to fillets and

fillet blocks.

Use of filleting machines is widespread in the processing of

cod and pollock in Alaska, but even the best machine can not

produce a boneless fillet that does not need further candling and

trimming to remove defects such as skin, bones, and parasites. As

much as 10% of the round weight of cod may be discarded as

trimmings during the production of fillets (Babbitt and Reppond

1987). Labor costs, however, will limit the amount of candling

and trimming that is economically feasible. Mechanical meat

separators are available that produce a boneless, skinless mince

from trimmings (Erichsen et al. 1972). A problem facing

production of mince from cod or pollock trimmings is the presence

of parasites commonly called "sealworms" or "codworms."
2

Sealworms reach adult form in marine mammals, but man encounters

them in an intermediate form in certain fish (Hafsteinsson and

Rizvi 1987). Although sealworms do not present a significant

health hazard because they are killed during freezing (-20°C for

60 hours) or cooking (60°C for 10 minutes), their presence is

understandably unacceptable (Margolis 1977, Wootten and Cann

1978). The purpose of this experiment was to determine if

mechanical meat separators could produce a boneless, sealwormfree

mince that could be used in products such as fish sticks or

portions.

MATERIALS AND METHODS

Sample Preparation

The experiment was conducted in Kodiak, Alaska, by personnel

from the Utilization Research Division. The Brown International

Model 4000 Finisher* operates in a manner similar to the refining

apparatus in the production of surimi. Rotating paddles propel

material through a cylindrical two-piece screen. A clam-shell

frame holds the screen and allows for easy cleaning and switching

of screens. Mince is collected in a hopper after it passes

through the screen, while waste material is discharged out the

far end. The Brown Finisher was equipped with paddles having a

pitch of 0.375 in (9.5 mm) and the clearance between the screen

and the paddles was 0.090 in (2.3 mm). Three screens were used in

this work: one with 0.094 in (2.4 mm) diameter holes on

* Reference to trade names does not imply endorsement by the

National Marine Fisheries Service, NOAA.
3

0.188 in (4.8 mm) centers; one with 0.125 in (3.2 mm) holes on

0.25 in (6.4 mm) centers; and one with 0.188 in (4.8 mm) holes on

0.25 in (6.4 mm) centers. These screens shall be referred to as

the 0.094, 0.125, and 0.188 screens hereafter. A heavier backup

screen with 0.625 in (15.9 mm) holes on 0.813 in (20.7 mm)

centers provided support and rigidity for the finer screens. All

screens had an area of 732 in2 (4722 CM2). The speed of paddle

rotation was set at 650 rpm.

To determine the efficiency of parasite removal, trimmings

from a cod filleting line in a local cannery were examined on a

candling table and pieces with worms were saved. About 100 lb

(45.4 kg) of trim with a load of at least 400 worms was first

ground through a meat grinder equipped with a 0.188 in extrusion

plate. The ground flesh was divided into three portions, one for

each of the finisher screens, and then fed through the Brown

Finisher. A sample of 16.75 lb (7.6 kg) from each of the

screenings was examined on a candling table for bones and worms.

To produce enough material to obtain yield data and to

conduct a frozen storage experiment, two lots of cod trimmings

were obtained from the filleting operations of two Kodiak

processors. The trimmings from Lot 1 appeared to have more pin

bone trimmings and fewer belly flaps than the trimmings from Lot

2. Both lots appeared to be of good quality based on color and

odor. Trimmings from Lot 1 were briefly drained on a large mesh

screen then minced using a Baader Model 694 flesh separator

machine equipped with a drum with 5 mm openings. Two 16.75 lb
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blocks of this unrefined mince were frozen in cardboard liners at

-40°C for 4 hours and stored at -18°C for sensory analysis.

Samples for chemical analysis were frozen in plastic bags at

-40°C and stored 1 month at -18°C. The remaining mince was

refined with the Brown Finisher with the 0.094 screen. Samples of

refined mince for sensory and chemical analysis were prepared as

before.

Trimmings from Lot 2 were prepared in a similar manner

except they were fed through a meat grinder equipped with a 0.188

in plate rather than being deboned with the Baader 694. Unrefined

mince was sampled for chemical analysis in the same manner as in

Lot 1. The remaining mince was fed into the Brown Finisher

equipped with either the 0.125 screen or the 0.188 screen.

Samples for sensory and chemical analysis were prepared as

before. With the 0.094 and 0.125 screens, waste material from the

first pass through the Finisher was refined a second time to

increase yield.

Chemical Analysis

Analyses for protein, moisture, fat, ash (Association of

Official Analytical Chemists 1980), trimethylamine (TMA),

dimethylamine (DMA), and trimethylamine oxide (TMAO) (Babbitt et

al. 1987) were conducted within 1 month of frozen storage. At 3

and 6 months of storage, analyses for DMA and TMAO were performed

using unbreaded portions cut for sensory analysis.
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Sensory Analysis

Portions (3 by 1.75 by 0.5 in, 76 by 44 by 13 mm) for

sensory analysis were sawed from the frozen blocks, battered, and

breaded using commercial products (Newlywed Foods), and fried in

vegetable oil at 350°F (177°C) in a Wells Model F-67 deep fat

fryer. Coded samples were served warm to a panel consisting of 8

to 10 experienced judges. Flavor was rated on a seven point

scale: 7, excellent; 4, neutral or bland; 1, extremely bad.

Chewiness and moistness were rated on seven point scales,

respectively: 7, very tough or dry; 4, firm or moist; 1, very

soft or juicy. Desirability was also a seven point scale: 7, very

desirable; 4, neutral; 1, very undesirable. Texture was rated on

a 7 point categorical scale: 7, fibrous; 6, grainy; 5, flakey; 4,

spongy; 3, mushy; 2, crumbly; and 1, rubbery. The panel was also

asked to rank the samples with respect to lightness or darkness

of the cooked flesh. Panel scores were analyzed using analysis of

variance (ANOVA) techniques (Sokal and Rohlf 1969, Bowman and

Cahill 1975). A sample ballot is enclosed as Figure 1.

Thaw Drip, Color, and Mechanical Texture Analysis

Determination of thaw drip by a double-bag immersion method

used the same size portions as those used for sensory analysis.

Each portion was weighed and placed in a perforated polyester

bag. Each bag was then placed in a larger bag equipped with a

weight to insure immersion. The samples were suspended in a

circulating water bath at 15°C for 40 minutes. After thawing, the
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sample was reweighed to determine weight loss. At 3 months of

storage, it became evident that the immersion method gave values

that were too low; therefore, the centrifugal thaw drip method of

Miyauchi (1962) was used at 6 months.

The color of the raw, thawed portions was measured with a

Minolta Reflectance II meter to determine the Hunter L*, a*, and

b* values. Mechanical textural analyses used portions prepared in

the same manner as those used for sensory analysis, except that

the samples were cooled and their breading removed before

testing. A Model 1000 Instron texture testing machine equipped

with a 1 cm cylindrical probe at a crosshead speed of 50 mm/min

was used. Stress and strain at failure were recorded and used to

calculate Young’s modulus (Bourne 1982).

RESULTS AND DISCUSSION

Worms, Bones, and Yield

Using the Brown Finisher, not a single intact worm was

detected in any of the 16.75 lb samples of minced flesh. This is

remarkable considering that the original material had four

parasites per pound (Table 1). As might be expected, more worm

fragments were found when larger screens were used but the 0.125

screen was still highly effective in separating parasites. An

additional block of mince prepared with the 0.188 screen had

three bones (0.3, 0.5, and 1.5 cm) and two worm fragments between

1.0 and 1.5 cm in length. Inspection of a block of minced flesh

from the Baader 694 yielded one 3.2 cm bone, four intact worms
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2 cm or greater in length, and two worm fragments 1-2 cm in

length.

Total yields were 54, 81, and 89%, respectively, for the

0.094, 0.125, and 0.188 screens. It should be noted again that

in using the 0.094 and 0.125 screens, waste material from the

first pass was run through the Finisher a second time to increase

yield. Because some material remained in the Finisher at the end

of each of the the yield experiments, yields in this experiment

may be lower than in a commercial operation.

Chemical Analysis

Moisture content appeared somewhat higher and protein

content somewhat lower for the Lot 2 mince than for the Lot 1

mince (Table 2) but, for the purposes of the experiment, these

differences were not meaningful. The values for protein, ash,

lipid, and TMA appeared to be similar for all samples. Because

the chemical composition of the material from the two lots were

similar, it was assumed that subsequent changes during frozen

storage would be similar; therefore, further reference to Lot 1

and Lot 2 in the text or tables was discontinued. The TMAO

content dramatically decreased between 1 and 3 months while the

DMA content showed a similar increase (Table 3). The high levels

of DMA were somewhat surprising at 3 months as the samples were

largely of good quality according to sensory results. Smaller

changes occurred between 3 and 6 months.
8

Thaw Drip and Color

At 1 month, mince refined with the Brown Finisher had less

thaw drip than unrefined mince (Table 4). At 3 and 6 months,

essentially no thaw drip was detected using the double bag

method. When the 6-month samples were subjected to the

centrifugal thaw drip procedure, the extremely high values

indicated that most of the protein had lost its water holding

ability. Evidently, the immersion method of determining drip is

not suitable for minced products.

Hunter L* values of thawed, raw portions of unrefined and

refined mince were similar at 1 or 3 months, but at 6 months, the

unrefined mince had lower values (Table 5) . Lower L* values

indicate darker color. The Hunter a* values were not affected by

increasing the time of frozen storage. Although a* values were

affected by using the Brown Finisher, the trend was inconsistent.

Higher a* values indicate more red hue. The Hunter b* values

tended to be highest for material that passed through the smaller

screens and tended to increase during frozen storage for the

material passed through the 0.125 and 0.188 screens. A positive

b* value is associated with a yellow hue.

Sensory Analysis

Use of the Brown Finisher did not affect flavor, moistness,

or desirability scores, but did affect chewiness scores as

unrefined Baader mince was less chewy than mince from the Brown

Finisher (Table 6). Overall quality was acceptable at 3 months of

frozen storage for all samples, but at 6 months, blocks of mince
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from the Brown Finisher had mean desirability scores of less than

4.0 indicating lower and perhaps unacceptable quality. Throughout

the study, most panelists rated the unrefined minced portions

from the Baader as darker than the rest. Frozen storage resulted

in more off flavor, more chewiness, less moistness, and decreased

desirability, especially between 3 and 6 months for samples from

the Brown Finisher.

According to a Chi-square analysis, neither screen size (G =

25.07; degrees of freedom, df = 18) nor storage time (G = 20.31,

df = 12) had a significant (P < 0.05) effect on texture ratings.

At 1 month of frozen storage, the mince from the Baader elicited

a variety of texture ratings, while the mince from the Brown

Finisher were predominately spongy (Table 7). At 3 months, the

results were similar except that some rubbery texture was noted

for the Brown Finisher mince. At 6 months, all samples were

predominately spongy, but some rubbery ratings were noted again.

Mechanical Texture Analysis

Mechanical testing of cooked samples showed results similar

to the sensory analyses. Portions made from mince refined with

the Brown Finisher tended to have a higher stress at failure and

a higher Young’s Modulus than portions made from the unrefined

Baader mince (Table 8). Both stress and Young’s modulus increased

during frozen storage with the amount of increase being smallest

for the mince from the Baader. A higher Young’s Modulus meant

that more stress is needed for the same amount of strain.
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Strain at failure tended to be higher for minced samples from the

Brown Finisher, especially at 3 and 6 months of frozen storage.

The strain was higher at 3 months than at 1 or 6 months. A

possible explanation for this result is that samples became

tougher and more deformable between 1 and 3 months, but more

brittle thereafter.

CONCLUSION

Use of the Brown Finisher was effective in producing a mince

essentially free from parasites and with compositional and

chemical characteristics similar to that of mince made with the

Baader 694. However, just as minced fish flesh typically

deteriorates more quickly during frozen storage than intact

fillets (Babbitt et al. 1984), mince refined with the Finisher

may have deteriorated more quickly than unrefined mince. Perhaps

the refining process enhanced the effect of cellular disruption

that is associated with minced products. Mince from the Brown

Finisher was acceptable to at least 3 months of frozen storage at

-18°C, but at 6 months, the texture was tough, resulting in

lowered desirability. Denaturation of protein, as indicated by

high levels of DMA, was probably responsible for textural changes

during frozen storage in all samples. Changes in rheological

properties of cooked portions paralleled those seen in the

sensory work. The size of the holes in the screens did not affect

results to a great degree, but use of the 0.188 screen may not

prove as effective in removing bones and worm fragments as the
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smaller screens. The 0.125 screen may prove more feasible to use

than the 0.094 screen in a commercial operation due to its

greater yield. The frozen shelf life of a commercially produced

product could be influenced by several factors such as the

initial quality of the trim, storage temperature, length of time

before and after cooking, and perhaps the size of serving

portion. Additional experiments should be performed to determine

how these factors affect quality, as well as the feasibility of

using pollock fillet trimmings.
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CITATIONS

Association of Official Analytical Chemists. 1980. Official methods of

analysis, 13th ed., Association of official Analytical Chemists,

Washington, D.C.

Babbitt, J. K., B. Koury, H. Groninger, and J. Spinelli. 1984.

Observations on reprocessing frozen Alaska pollock (Theracrra

chalcogramma). J. Food Sci. 49(2):323-326.

Babbitt, J. K., and K. D. Reppond. 1987. Minced flesh from cod and

pollock trimmings. October-December Utilization Division

Quarterly Progress Report. Northwest Fisheries Science Center,

2725 Montlake Blvd. East, Seattle, WA 98112.

Babbitt, J. K., K. D. Reppond, and A. Hardy. 1987. Frozen storage

stability of modified pollock (Theragra chalcogramma) blocks

containing 15% or 30% minced pollock. J. Food Sci.

52(2):1191-1193 and 1211.

Bourne, M. 1982. Food texture and viscosity: Concept and measurement.

Academic Press, New York, 325 p.

Bowman, K. S., and M. Cahill. 1975. Statistical package for the social

sciences, 2nd ed. McGraw-Hill, New York, 381 p.

Erichsen, L. B., 0. R. Taylor, G. Vedie, and F. J. Miller. 1972.

Commercially available equipment. In Roy E. Martin (editor),

Second Technical Seminar on Mechanical Recovery and Utilization

of Fish Flesh, p. 127-156. National Fisheries Institute,

Washington, D.C.

Hafsteinsson, H., and S. S. H. Rizvi. 1987. A review of the sealworm.

problem: Biology, implications and solutions. J. Food Protect.

50(l):70-84.

Margolis, L. 1977. Public health aspects of "codworm" infection: A

review. J. Fish. Res. Board. Can. 34:887-898.

Miyauchi, D. 1962. Application of the centrifugal method for measuring

shrinkage during the thawing and heating of frozen cod fillets.

Food Technol. 16(l):70-72.

O’Bannon, B. K. 1988. Fisheries of the United States, 1987. Current

Fishery Statistics No. 8700, U.S. Government Printing Office,

Washington, D.C. 20402.

Sokal R. F., and F. J. Rohlf. 1969. Biometry. W. H. Freemand and Co.,

San Francisco, CA, 776 p.

Wootten R., and D. C. Cann. 1978. Round worms in fish. Torry Advisory

Note No. 80. Torry Research Station, Aberdeen, Scotland.
13

Table 1.--Number of worm fragments found in a 16.75 lb (7.6 kg)

block of mince from a Brown Finisher.

* The 0.094, 0.125, and 0.188 in screens had 2.4, 3.2, and 4.8 mm

diameter holes, respectively.
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Table 2.--Results of chemical analyses including trimethylamine

(TMA) of refined and unrefined cod mince after 1 month

storage at -18°C. Values are means ± standard

deviations.

aThe 0.094, 0.125, and 0.188 in screens had 2.4, 3.2, and 4.8 mm

diameter holes, respectively.

bMinced with Baader 694 with 5 mm drum.

cGround through a plate with 0.188-in (4.8 m) holes.

dUnrefined mince.

eHyphen means that no analysis was performed on this sample.
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Table 3.--Change in dimethylamine (DMA) and trimetylamine (TMAO)

content (mg N/100 g) of refined and unrefined cod mince

during storage at -18°C. Values are means ± standard

deviations.

aThe 0.094, 0.125, and 0.188 in screens had 2.4, 3.2, and 4.8 mm

diameter holes, respectively.

bUnrefined mince from Lot 1.
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Table 4.--Change in thaw drip of portions from blocks of refined

mince and unrefined cod mince during storage at -18°C.

Values are means ± standard deviations.

aThe 0.094, 0.125, and 0.188 in screens had 2.4, 3.2, and 4.8 mm

diameter holes, respectively.

bUnrefined mince from Lot 1.

cImmersion method.

dCentrifugal method.
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Table 5.--Change in Hunter L*, a*, and b* values of refined and

unrefined cod mince during storage at -18°C. Values

are means ± standard deviations.

aThe 0.094, 0.125, and 0.188 in screens had 2.4, 3.2, and 4.8 mm

diameter holes, respectively.

bUnrefined mince from Lot 1.
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Table 6.--Change in sensory scores of refined and unrefined cod

mince during storage at -18°C. The F statistic and its

associated probability (P) are included for a series of

one-way analysis of variance (ANOVA) tests. Values are

means ± standard deviations.
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Table 6.--Continued.

1 The 0.094, 0.125, and 0.188 in screens had 2.4, 3.2, and 4.8

mm diameter holes, respectively. 2 Unrefined mince from Lot 1. ABCMeans in the same column sharing the same capital letter were

not significantly different (P < 0.05).

abcMeans in the same row sharing the same lower case letter were

not significantly different (P < 0.05).
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Table 7.--Distribution of texture scores of refined and unrefined

cod mince during storage at -18°C.

aThe 0.094, 0.125, and 0.188 in screens had 2.4, 3.2, and 4.8 mm

diameter holes, respectively.

bUnrefined mince from Lot 1.
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Table 8.--Changes in stress, and strain at failure, and Young’s

modulus of cooked portion of cod mince and refined

mince during storage at -18°C. Values are means ±

standard deviations.
22

Table 8.--Continued.

1 The 0.094, 0.125, and 0.188 in screens had 2.4, 3.2, and 4.8

mm diameter holes, respectively. 2 Unrefined mince from Lot 1.

ABCMeans in the same column sharing the same capital letter were

not significantly different (P < 0.05).

abcMeans in the same column sharing the same lower case letter

were not significantly different (P < 0.05).
23