Upload
others
View
1
Download
0
Embed Size (px)
Citation preview
IA, Fisheries Pitches lir and Oceans et Oceans
DFO - Libra
i Iiiiiirque 10018630
Project Report
Fisheries Development Branch Scotia-Fundy Region Halifax, Nova Scotia
JUL 1 3 1999 LIE.iF;At,
:BEDFORD I 11J .ANOCRArH y H
~ Canada
a 3$O I
PROGRAM DEVELOPMENT DIVISION FISHERIES DEVELOPMENT BRANCH P.O. BOX 550 HALIFAX, NOVA SCOTIA B3J 2S7
NOVA SCOTIA DEPARTMENT OF FISHERIES P.O. Box 2223
AND HALIFAX, NOVA SCOTIA B3J 3C5
This is an unedited consultant's report financed in full or in part by the Fisheries Development Branch, Scotia-Fundy Region. The views expressed in this report are those of the consultant and not necessarily those of the Branch.
This report is not to be cited without written permission from the Branch Director.
Project Officers: P.J. Re 426-9938
M. Drebot 424-4560
No. 110
POTASSIUM SORBATE/METHYLCELLOLOSE TREATMENT OF ICED GUTTED COD (Gadus morhua)
By:
A.D. Woyewoda, C. Stevens, J. Evrovski, D. Singer, D. Sherwood and E.G. Bligh
Canadian Institute of Fisheries Technology P.O. Box 1000 Halifax, N.S.
B3J 2X4
April, 1986
For DSS Contract No.: OSC 84-00596
PROJECT FUNDING
Funding for this project was from 3 sources:
Fisheries and Oceans P.O. Box 550 Halifax, Nova Scotia B3J 2S7
Nova Scotia Department of Fisheries P.O. Box 2223 Halifax, Nova Scotia B3J 3C5
Research Grant to E.G. Bligh Natural Sciences and Engineering Research Council of Canada
ACKNOWLEDGEMENTS
The authors gratefully acknowledge the skillful assistance of Claude Hotton in the raw quality evaluation component of this project.
INTRODUCTION
Data from our Institute has previously shown potassium sorbate
effective as a dip for shelflife extension of cod fillets but not iced
gutted cod. Presumably the sorbate was washed away by the melting of
ice. Incorporation of sorbate into a gel could reduce loss of the
chemical from the washing action of melting ice and extend
effectiveness.
This study includes a brief literature review, a preliminary study
exploring the suitability of gels and finally, results of a pilot run
monitoring iced shelflife of gutted cod over 16 days. Another treatment
incorporating the use of "chemical ice" made from a 3% potassium sorbate
solution as requested by Mr. M. Drebot, Nova Scotia Department of
Fisheries, is also included in the pilot run.
TABLE OF CONTENTS
Page
1.0 BRIEF LITERATURE SURVEY 1
2.0 PRELIMINARY EXPERIMENT 3
2.1 Objective 3
2.2 Method 3
2.3 Results and Discussion 4
2.4 Conclusion 4
3.0 PILOT RUN 5
3.1 Objective 5
3.2 Methods 5
3.2.1 Procurement of Fish 5
3.2.2 Treatment Schedule 5
3.2.3 Treatment Solutions and Sorbate Ice 6
3.2.4 Treatment and Storage of Fish 6
3.2.5 Sampling and Microbiology 7
3.2.6 Evaluation of Raw Quality 7
3.2.7 Chemical Analysis 7
3.2.8 Sorbate Loss from Melting Sorbate Ice 8
3.2.9 Sensory Evaluation 8
3.3 Results and Discussion 9
3.3.1 Raw Quality Evaluation 9
3.3.2 Microbiology 14
3.3.3 Trimethylamine 17
3.3.4 Moisture 20
TABLE OF CONTENTS (cont'd)
Page
3.3.5 Sensory Evaluation 22
3.3.6 Loss of Potassium Sorbate from Chemical Ice 23
3.4 Conclusion 24
4.0 REFERENCES 26
5.0 APPENDICES 30
5.1 Grading Guide for Iced Groundfish 30
5.2 Form for Raw Quality Evaluation 31
5.3 Evaluation Form for Cooked Quality 32
LIST OF TABLES
Page
1. Average Temperature (C°) of Iced Cod 11
2. Comments from Raw Quality Grading Sessions 11
3. Number of Fish in Each Category According to 3 Graders 12
4. Percent of Fish in Each Grade Category 12
5. Total Aerobes (log cfu/g) of Iced Gutted Cod 14
6. Alteromonas putrefaceans (log cfu/g) of Iced Gutted Cod 15
7. Trimethylamine (mg TMA nitrogen per 100 g) of Iced Gutted Cod 18
8. Moisture Content (%) of Iced Gutted Cod 21
9. Parametric Analysis (ANOVA) of Odour of Cooked Cod Fillets 22
10. Parametric Analysis (ANOVA) of Flavour of Cooked Cod Fillets 23
11. Nonparametric Results of Sensory Evaluation 23
LIST OF FIGURES
Page
1. Overall Raw Quality Scores of Iced Cod 13
2. Raw Odor Scores of Iced Cod 13
3. Total Aerobes of Iced Cod 16
4. Log (1+mg TMA-N) of Iced Cod 19
5. Average Flesh Moisture 20
6. K-sorbate in Drip from Chemical Ice 24
1 . 0 BRIEF LITERATURE SURVEY
- 1 -
1.0 BRIEF LITERATURE SURVEY
Sorbates are widely used in the food industry as microbial
inhibitors for a range of products, eg. cheese products, baked goods,
fruit juices, fresh fruits and vegetables, wines, soft drinks, pickles,
sauerkraut and certain meat and fish products (1). Yeasts and molds are
the most affected, particularly at lower pH where sorbate/sorbic acid
effectiveness increases (1). Unfortunately the acid form is very much
less soluble than its potassium salt; 0.16 vs 139.2 g/100 ml at 20°C.
Recent research has shown that even with reduced antimicrobial
activity potassium sorbate is still somewhat effective against pathogens
Clostridium botulinum (2,3), Vibrio parahaemolyticus (4), and
Salmonellae (5). As well, P. fragi (6), Alteromonas putrefaciens (7)
and P. fluorescens (8), proven fish spoilers, are inhibited to various
degrees by sorbate. Growth of three strains of Vibrio parahaemolyticus
was delayed in flounder homogenate acidified to pH 6.2 and treated with
0.05% (w/w) sorbic acid (9). Similar results were found for A.
putrefaciens in a homogenate of English sole (10).
Success in shelflife preservation has been achieved in cod fillets
(11,12, 13), haddock fillets (14), blue grenadier fillets (15) and
scallops (16,17). The positive action of sorbate dips on fillets has
not been duplicated with round fish (12,14) probably due to a lack of
penetration or adhesion of the additive. Only where dwell time or
contact of sorbate has been extended, eg. sorbate ice, has there been
significant shelf life extension of fresh gutted fish (18,19,20,21).
2
Intimate sorbate/fish contact could be facilitated through the use
of thickening agents in the dip. Methylcellulose and
hydroxypropylmethylcellulose are two inert thickeners or suspending
agents which, widely used in bakery products, salad dressings, ice
cream, and flavour emulsions, could in conjunction with sorbate show
potential as coating agents for gutted fish.
2 . 0 PRELIMINARY EXPERIMENT
3
2.0 PRELIMINARY EXPERIMENT
2.1 Objective
To investigate the feasibility of potassium sorbate/methylcellulose
treatment of gutted cod.
2.2 Method
Combinations of methylcellulose (Methocel® A-15C, Dow Chemical
Company, Sarnia, Ontario), potassium sorbate (Monsanto Industrial
Chemicals Co., St. Louis, Mo.) and citric acid (Sigma Chemical Co., St.
Louis, Mo.) were tested for gel stability on wet fish. The mixture
which provided the best gel was Methocel® (2% w/v)/citric acid (1%)/
potassium sorbate (3%). This gel was prepared hot and cooled before
use.
Freshly landed gutted Atlantic cod (Gadus morhua) averaging 1.2 kg
were puchased from a local fish market, transported to the laboratory
and treated by one of the following:
A. No treatment
B. Methocel® (2%) dip
C. Methocel (2%)/citric acid (1%) dip
D. Methocel® (2%)/citric acid (1%)/potassium sorbate (3%) dip
After dipping, fish were iced in a ratio of 3 parts fish to 1 part
ice in large fibreglass boxes and stored in the 1-2°C chill room.
Samples were withdrawn after 0,5,8,12,16 and 20 days for Alteromonas
putrefaciens and trimethylamine (22) measurement. Three fish were
evaluated per treatment at each withdrawal. During the experiment
problems were encountered with chill room temperature control. However
- 4
the experiment was not aborted.
2.3 Results and Discussion
Significant differences were not detected in A. putrefaciens counts
between treatments but the sorbate/methylcellulose/citric acid combina-
tion significantly slowed TMA formation. On day 16 untreated control,
methylcellulose control, methylcellulose/citric acid control, and
methylcellulose/citric acid/potassium sorbate had respective TMA values
of 68, 50,50 and 13 mg nitrogen per 100 g. Considering the limited num-
' ber of fish used for the experiment and the fact that problems were en-
countered with temperature control of the chill room, the statistical
significance of the data may be questionable. In all probability TMA
values of untreated, Methocele, and Methocele/citric acid control fish
were not different. However the 3-way combination of Methocel/citric
acid/sorbate certainly had an inhibitory effect on TMA formation. This
latter combination was also superior to the controls with respect to
physical quality.
2.4 Conclusion
Sorbate in combination with citric acid and Methocele did extend
shelf life of gutted head on cod in the preliminary trial. A pilot run
with better temperature control and greater sample numbers is necessary
to prove:
- the benefit of sorbate application as a gel vs sorbate water dip
- the benefit of citric acid addition to sorbate/gel dips
3 . 0 PILOT RUN
- 5
3.0 PILOT RUN
3.1 Objective
To monitor the quality of gutted cod
- dipped in combination of potassium sorbate, Methocel® gel
and citric acid and stored on ice.
- stored on ice containing potassium sorbate
3.2 Methods
3.2.1 Procurement of fish
Cod fish (Gadus morhua) averaging 3.4 lb caught May 21, 1985 in
Chedabucto Bay, N.S., gutted at sea, transported to Halifax by
refrigerated truck and purchased by CIFT the next day, May 22, from the
Fish Basket Ltd., Eastern Passage, N.S. were treated by CIFT immediately
upon arrival.
3.2.2 Treatment
Fish were coded and dipped for 2 minutes in solutions of Table 1.
Table 1 Treatment Schedule
Code Solution
MA tap water
MB potassium sorbate (3%)
MC Methocel® 856 (1%)/citric acid (1%)
MD Methocel® 856 (1%)/potassium sorbate (3%)
ME Methocel® 856 (1%)/potassium sorbate (3%) /citric acid (1%)
MF chemical ice (potassium sorbate, 3%)
- 6
3.2.3 Treatment Solutions and Sorbate Ice
Methocelo 856 (Dow Chemical Company) purchased from Howard
Industries, Dartmouth, N.S. was mixed in 100 litre lots according to
instructions provided by first preparing a slurry in hot water and
diluting to the required concentration by addition of cold water from a
fine nozzle with vigorous stirring. Citric acid and potassium sorbate,
both food grade (Howard Industries, Dartmouth), were added during the
cooling water addition when required. Prepared solutions were stored
overnight at 2°C to cool.
Chemical ice was prepared by pouring 3% potassium sorbate into
plastic bags on 1 inch high trays and freezing in a plate freezer. The
slabs of ice were kept in the bags at room temperature to temper to
their melting point and then pulverized before application to the cod.
3.2.4 Treatment and Storage of Fish
Cod fish were dipped in groups of 12 for 2 minutes in 100 litres of
non-viscous solutions (MA or MB) and individually in the same volume of
viscous gels (MC to ME).
The fish were immediately iced with 1 part fish to 2.7 parts ice in
90 litre stromborg boxes coded by treatment. A plexiglass sheet, the
length of the box, facilitated icing of 7 fish in each half which
allowed complete removal of contents from one side without disturbing
the other. Ice was added once fish were removed.
Boxes were stacked according to treatment in an insulated enclosure
(1" Purlboarda) in the +2°C chill room. Storage conditions approximated
7
those in a fish hold, i.e. low temperature and slow melting rate of
ice. Fish in the last treatment were iced similarly with "chemical ice"
tempered to its melting point as described in section 3.2.3 but stored
in a separate enclosure.
Addition of extra ice to each box was required only once during the
16 day study indicating that the melt rate was very low.
3.2.5 Sampling and Microbiology
Seven cod fish from each treatment (one half of one box) were
evaluated 0,5,7,9,12,14 and 16 days afer dipping. Four fish per
group were microbiologically sampled by aseptically peeling back a strip
of skin from the posterior left side and excising a 20 g sample of
flesh. Total aerobes and Alteromonas putrefaceans were enumerated
according to standard procedures (28). Cod were then transferred to the
chemistry laboratory for raw quality grading and chemical analysis.
3.2.6 Evaluation of Rev Quality
Quality of seven fish per treatment was evaluated by 3 graders
according to the Fisheries and Oceans grading scheme (23) outlined in
Appendix 1 and 2. A digital thermometer (Temp-Master, model 10C, PID
instruments, Downsview, Ontario) was used for measurement of internal
temperature. Graders were not aware of codes or treatments to prevent
bias. The first grading session was 1 day after dipping.
3.2.7 Chemical Analysis
After grading, 6 complete right fillets were excised, skinned,
paired into 3 groups, macerated in a domestic food processor and 2
subsamples of each blend weighed and frozen for trichloroacetic acid
extraction and trimethylamine determination by the picric acid method
8
(24,25). Remaining fillets were packed in 1 lb waxed cartons and frozen
at -35°C for sensory evaluation. Moisture was determined in duplicate
on each blend by drying at 103°C overnight.
3.2.8 Sorbate Loss from Melting Sorbate Ice
To determine the loss of potassium sorbate from melting chemical
ice, 1 kg of crushed ice made from 3% food grade potassium sorbate
solution was placed in a Buchner funnel at room temperature.
Consecutive 20 ml aliquots were collected until the ice melted
completely. From the absorbance at 254 nm, concentration of potassium
sorbate in the drip was calculated.
3.2.9 Sensory Evaluation
A formal taste panel (in individual booths) was conducted for fish
from sampling days 9, 12 and 14 by defrosting fillets at 5°C overnight,
comminuting briefly in a food processor (with thaw drip added),
with an ice cream scoop portioning into 100 x 20 mm glass petri plates,
covering, and baking at 425°F for 12 minutes. Ten panelists each
received one numerically coded petri plate from treatments MA, MB and MF
plus two plates of good quality reference (MA) frozen on day 0, ie. one
labelled "R" and the other coded (hidden reference). Members were
instructed to taste the reference "R" before each coded sample and then
indicate their grades for odor and flavor on 10 cm grading lines
(Appendix 3). Data was analyzed parametrically by analysis of variance
(26) and non- parametrically by rank (27).
- 9
3.3 Results and Discussion
3.3.1 Raw Quality Evaluation
Average temperatures of fish in sorbate ice (MF) were generally
lowest (Table 1). During the first evaluation session, graders
commented that fish from this treatment were more firm, almost to the
point of being frozen. Subsequently, fillets from cod stored in sorbate
ice (MF) were reported to be opaque and grainy in appearance, as if
previously frozen. Such changes are sometimes observed in fish stored
under superchill conditions. Volunteered written comments of graders
are presented in Table 2. "Best treatments" were from an evaluation
during the latter part of each grading session when samples of all fish
withdrawn that day were presented to 2 graders simultaneously for an
"overall" judgement.
In general, fish were softer than normal when received, ie they may
have been recovering from a post-spawn condition; high moisture values
(see Table 8) indicate starvation. Methocel® dipped cod were glossier
than other fish, especially initially. The treatment gel was not
however visible after 1 day on ice except in one treatment, ME, where a
small amount remained in the belly cavity.
Number and percent of fish in each grade category is shown in
Tables 3 and 4. Data of Table 4, multiplied by 1,2,3 and 5 for grade
A,B,C and R, respectively, and combined is shown in Figure 1. Treatment
MC, ie Methocel® plus citric acid appears inferior in most cases.
Sorbate-dipped fish, MB, remained of good quality until day 14 when melt
water probably removed most of the chemical. Gill appearance and odor
of sorbate-dipped fish was usually better than control fish.
- 10 -
Sorbate-ice cod remained of good quality for most of the study.
Odor of fillets scored well even on day 14 (see Figure 2) and after 16
days on ice this treatment was the only one where all fish were not
rejected. Fillets from sorbate dipped cod (MB) scored better in raw
odor than most other treatments on days 7, 9 and 12.
Generally, the presence of citric acid produced a reddening of the
area along the backbone in the belly cavity. Methocel® 856 did not
appear to affect the action of potassium sorbate until day 14; it may in
fact have physically interfered with sorbate action initially. Sorbate
dip (MB) probably penetrated the gill area more extensively than when
combined with the gel and had an immediate effect on quality.
TABLE 1. Average Temperature (6C) of Iced Cod
Days MA MB MC MD ME MF Post Water Sorbate Methocel + 1% Methocel + 3% Methocel + 3% Sorbate Mortem Dip Dip Citric Acid Sorbate Sorbate + 1% Ice
Citric Acid
1 +1.9 0.0 0.0 -0.1 0.0 -1.0 5 0.0 0.0 -0.9 -0.1 0.0 -0.7 7 0.0 -0.3 +0.1 +0.4 +0.1 -1.0 9 +1.0 0.0 -0.7 0.0 +0.7 -0.1 12 +0.7 +1.1 0.0 0.0 -0.1 0.0 14 0.0 +0.4 +0.3 0.0 0.0 -0.6 16 +0.9 -0.7 0.0 0.0 0.0 -0.9
TABLE 2. Comments from Raw Quality Grading Sessions
Days Post Mortem
MA Water Dip
MB Sorbate Dip
MC Methocel + 1% Citric Acid
MD Methocel + 3% Sorbate
ME Methocel + 3% Sorbate + 1% Citric Acid
MF Sorbate Ice
1 skin slightly bleached
fillets slight- ly jellied
some white gel in belly cavity
stiff, almost frozen
5 mucous in belly cavity
7 best gills pink discolora- tion in belly cavity, discol- ored along backbone
second best gills, opaque flesh, previously frozen
9 poorest appear- ance
best skin appearance
skin slightly bleached, pink inside belly cavity
slight pink in belly cavity
pink stained belly cavity, second best skin appearance
flesh ap-pears spongy
12 red stains in belly cavity
looks best, all gills neutral in odour
very pink cavity bleached skin
pink cavity, looks good, some gills sour
pink cavity, slightly bleached, looks good
spongy flesh, like frozen, grassy odor to fillets
14 very bad best treat- ment
very bad looks good
- 12 -
TABLE 3. Number of Fish in Each Grade Category from 3 Graders
Days Post Treatment
A B
MA Water Dip
C R A
MB Sorbate Dip
B C R A
MC Methocel + Citric Acid
B C R
I I
A
MD Methocel + Sorbate
B C R
ME Methocel + Sorbate + Citric Acid A B C R A
MF Sorbate
Ice
B C R
1 Grader. 1 1 5 1 0 0 7 0 0 0 6 1 0 0 4 3 0 0 5 2 0 0 6 1 0 Grader. 2 5 2 0 0 0 7 0 0 0 4 3 0 0 4 3 0 0 5 2 0 0 4 3 0 Grader# 3 0 6 1 0 0 7 0 0 0 6 1 0 0 2 5 0 0 6 1 0 0 7 0 0
Total 6 13 2 0 0 21 0 0 0 16 5 0 0 10 11 0 0 16 5 0 0 17 4 0 Percent 29 62 10 0 0 100 0 0 0 76 24 0 0 48 52 0 0 76 24 0 0 81 19 0
5 Grader# 1 0 4 2 1 0 4 2 1 0 4 2 1 0 3 4 0 0 3 4 0 0 5 2 0 Grader. 2 0 5 2 0 0 5 2 0 0 0 6 1 0 5 2 0 0 4 3 0 1 1 5 0 Grader. 3 0 5 2 0 0 7 0 0 0 3 3 1 0 3 4 0 0 2 5 0 0 0 5 2
Total 0 14 6 1 0 16 4 1 0 7 11 3 0 11 10 0 0 9 12 0 1 6 12 2 Percent 0 67 29 5 0 76 19 5 0 33 52 14 0 52 48 0 0 43 57 0 5 29 57 10
7 Grader. 1 0 5 2 0 0 2 4 1 0 3 4 0 0 3 4 0 0 5 1 1 0 1 5 1 Grader. 2 0 5 2 0 0 3 3 1 0 1 4 2 0 5 1 1 0 5 2 0 0 2 1 4 Grader# 3 0 5 2 0 0 4 2 1 0 3 3 1 0 2 4 1 0 4 3 0 0 3 3 1
Total 0 15 6 0 0 9 9 3 0 7 11 3 0 10 9 2 0 14 6 1 0 6 9 6 Percent 0 71 29 0 0 43 43 14 0 33 52 14 0 48 43 10 0 67 29 5 0 29 43 29
9 Grader# 1 0 2 5 0 0 0 7 0 0 0 7 0 0 2 5 0 0 2 5 0 0 2 4 1 Grader. 2 0 0 5 2 0 0 7 0 0 0 1 6 0 0 3 4 0 1 1 5 0 3 2 2 Grader# 3 0 2 4 1 0 2 5 0 0 2 3 2 0 5 2 0 0 5 2 0 0 4 3 0
Total 0 4 14 3 0 2 19 0 0 2 11 8 0 7 10 4 0 8 8 5 0 9 9 3 Percent 0 19 67 14 0 10 90 0 0 10 52 38 0 33 48 19 0 38 38 24 0 43 43 14
12 Grader. 1 0 0 4 3 0 0 6 1 0 0 6 1 0 0 5 2 0 0 5 2 0 0 7 0 Grader. 2 0 0 2 5 0 0 6 1 0 0 2 5 0 0 5 2 0 0 3 4 0 0 4 3 Grader. 3 0 1 2 4 0 0 7 0 0 0 0 7 0 1 3 3 0 0 6 1 0 2 5 0
Total 0 1 18 12 0 0 19 2 0 0 18 13 0 1 13 7 0 0 14 7 0 2 16 3 Percent 0 5 38 57 0 0 90 10 0 0 38 62 0 5 62 33 0 0 67 33 0 10 76 14
14 Grader. 1 0 0 2 5 0 0 2 5 0 0 0 7 0 0 6 1 0 0 1 6 0 0 4 3 Grader. 2 0 0 1 6 0 0 0 7 0 0 0 7 0 0 2 5 0 0 1 6 0 0 2 5 Grader. 3 0 0 1 6 0 0 0 7 0 0 0 7 0 0 5 2 0 0 3 4 0 0 7 0
Total 0 0 4 17 0 0 2 19 0 0 0 21 0 0 13 8 0 0 5 16 0 0 13 B Percent 0 0 19 81 0 0 10 90 0 0 0 100 0 0 62 38 0 0 24 76 0 0 62 38
TABLE 4. Percent of Fish in Each Grade Category
Days Post Treatment
MA Water Dip
MB Sorbate Dip
MC Methocel + Citric Acid
MD Methocel + Sorbate
ME Methocel + Sorbate + Citric Acid
MF Sorbate Ice
A B C R A B C R A B C R A B C R A B C R A B C R
1 29 62 10 0 0 100 0 0 0 76 24 0 0 48 52 0 0 76 24 0 0 81 19 0 5 0 67 29 5 0 76 19 5 0 33 52 14 0 52 48 0 0 43 57 0 5 29 57 1U 7 0 71 29 0 0 43 43 14 0 33 52 14 0 48 43 10 0 67 29 5 0 29 43 29 9 0 19 67 14 0 10 90 0 0 10 52 38 0 33 48 19 0 38 38 24 0 43 43 14 12 0 5 38 57 0 0 90 10 0 0 38 62 0 5 62 33 0 0 67 33 0 10 76 14 14 0 0 19 81 0 0 10 90 0 0 0 100 0 0 62 38 0 0 24 76 0 0 62 38
475_
425..
X 0
375_
A
X 325.
8
275_
225_1
175 a
16 10 1'2 14
A MA-(CONTROL) A ma-(3x KS) ❑ MC-(ix MC + ix CIT)
▪ MD-(1z MC + 3x KS) C. ME-Cix MC + 3x KS + lx CIT)
• MF-(3z KS ICE)
O
0
O a
C
*
1_
- 13 -
FIG 1 - OVERALL RAW QUALITY SCORES OF ICED COD
525
A MA-(CONTROL) A ma-(3./.., as) ❑ MC-(1'/. MC + lx CIT)
O MD-(1v. MC + 3x KS)
• ME-(lx MC + 3x KS + lx CIT)
• MF-(3x KS ICE)
A
,
112 114 16 DAYS ON ICE AFTER TREATMENT
FIG 2 - RAW ODOR SCORES OF ICED COD
DAYS ON ICE AFTER TREATMENT
- 14 -
3.3.2 Microbiology
Total aerobes (Table 5 and Figure 3) of sorbate-iced fish (MF) were
significantly lower than all treatments except MD (Methocel® plus
sorbate) overall. Treatments in order of highest to lowest total
aerobes for days 5 to 14 with statistical differences by 2-way analysis
of variance are:
MEa MBa MAab MCab
MDbC
mFC
where common superscripts indicate no significant difference (P<0.05).
Overall, MD was not significantly different from MA, MC or MF.
Alteromonas putrefaceans (Table 6) were unexpectedly low throughout
the study. The slow growth pattern observed was similar to that found
in soft cod reported by Woyewoda et al. (28). Cod used in this study
were softer than normal and high in moisture (Table 8). Data of Table 6
is the average of duplicate determinations on each of 4 fish.
TABLE 5. Total Aerobes (log cfu/g) of Iced Gutted Cod
Days Post Mortem
MA Water Dip
MB Sorbate Dip
MC Methocel + 1% Citric Acid
MD Methocel + 3% Sorbate
ME Methocel + 3% Sorbate + 1% Citric Acid
MF Sorbate Ice
1 3.23
5 3.00 3.10 2.61 2.92 4.82 3.23 *1.54 *0.93 *0.69 *1.00 *1.29 *0.76
7 3.57 2.66 3.27 2.99 3.32 2.35 *0.88 *0.11 *0.72 *1.07 ±0.67 *0.11
9 3.61 2.83 3.48 2.91 3.75 2.86 *0.76 *0.52 *0.54 *0.71 *0.62 ±0.99
12 3.88 4.76 4.31 4.79 5.32 3.17 *0.35 *1.53 *1.16 *0.78 *1.31 *0.54
14 5.17 5.94 4.61 3.63 4.21 4.10
*0.44 ±0.33 *0.82 ±0.31 *0.74 *0.63
16 5.13 5.43 4.93 4.12 4.29 4.25
*0.77 ±0.91 ±0.36 *1.10 *0.79 *0.70
TABLE 6. Alteromonas putrefaceans (log cfu/g) of Iced Gutted Cod
Days Post Mortem
MA Water Dip
MB Sorbate Dip
MC Methocel + 1% Citric Acid
MD Methocel + 3% Sorbate
ME Methocel + 3% Sorbate + 1% Citric Acid
MF Sorbate Ice
5 <1 <1 <1 <1 <1 <1 <1 <1 <1 <1 <1 <1 <1 <1 <1 <1 <1 <1 <1 <1 <1 1.3 est <1 <1
7 1.0
1 4 est fl fl fl fl fl
1.70 est 1.48 est 1.78 est 2.15 est <1 <1 <1 <1 <1 <1 1.30 est <1
9 2.30 est <1 1.70 est <1 <1 <1 1.70 est <1 2.18 est 1.30 est <1 <1 2.57 est <1 <1 <1 <1 1.00 est
<1 <1 <1 <1 1.30 est <1
12 1.60 est <1 1.60 est 1.84 est 1.90 est <1
1.60 est <1 1.30 est <1 3.28 est 1 est
2.04 est 2.08 est <1 2.91 est <1 <1 1.60 est <1 1.30 est <1 1.30 est <1
14 1.70 est 2.49 est 1 est <1 <1 <1
2.34 est 1.70 est 1 est 1 est <1 <1
2 est 2.62 est 1.90 est <1 1 est <1
2.74 est 2.73 est 1.85 est <1 1 est <1
16 1 est 1.48 est 1.78 est 2.38 est <1 <1
3.41 est 2.40 est 1.70 est <1 1.74 est 1.30
1.95 est 1.48 est 2.60 est 2.60 est 1 est <1
1.60 est 1.85 est 1.30 est 1.30 est 1 est <1
3_
--4
\ ..--, -
-
-AS , •...
--).rt ----__-
▪
---a- ,, t4,-...f ._ -
r---'''
d MA-CCONTROL)
• MB-(3m. ES)
O NC-(lx MC + lz CIT) ■ MD-tiz NC + 3% MS)
• NE-C1% MC + 3% ES + lz CIT) • MF-(3z ES ICE)
16 1'2 114 116.
- 16 -
FIG 3 - TOTAL AEROBES OF ICED COD
X
= N
0 4
X 0
C
0
DAYS ON ICE AFTER TREATMENT
- 17 -
3.3.3 Trimethylamine
Trimethylamine (TMA) a product of putrefaceans growth was
significantly lowest in sorbate iced fish, MF (Table 7 and Figure 4).
Treatments arranged from highest to lowest TMA values for days 5 to 14
with statistical differences are:
MCa
MAb MDc MEc MBd MFe
with common superscripts indicating no significant difference. Day 16
was not included in the statistical analysis since all treatments were
considered spoiled at this time, ie. greater than the 15 mg% cutoff.
Citric acid plus Methocel® dipped fish were significantly highest in TMA
overall with water dipped fish (MA), second. Sorbate plus Methocel®
with and without citric acid were better than the control but not as
good as sorbate-dipped or sorbate-iced fish. The results contradict
somewhat previous reports (12) where a sorbate dip did little to extend
shelf life of roundfish. The difference between the two experiments is
the melting rate of the ice; here it was very slow and sorbate was not
washed away. From Figure 4 it appears that the gel treatment had little
effect on TMA formation until later stages of storage while sorbate dip
without Methocel® had an immediate effect which gradually diminished.
- 18 -
TABLE 7. Trimethylamine (mg TMA nitrogen per 100 g)1 of Gutted Iced Cod
Days Post Mortem
MA Water Dip
MB Sorbate Dip
MC Methocel + 1% Citric Acid
MD Methocel + 3% Sorbate
ME Methocel + 3% Sorbate + 1% Citric Acid
MF Sorbate Ice
0 0.365 0.352 0.332
5 1.12 0.575 1.10 0.740 1.50 1.24 1.02 0.622 1.12 0.992 0.712 0.832 1.28 0.530 1.40 1.40 0.795 1.40
7 4.01 1.17 2.70 1.72 1.64 0.795 2.66 0.858 15.3 3.20 2.28 1.10 2.38 1.59 5.95 6.40 0.965 2.47
9 4.07 8.12 7.28 4.10 3.65 3.46 8.06 4.00 17.3 7.56 9.10 3.62 12.4 4.62 10.2 8.30 6.20 4.80
12 10.4 13.7 14.0 15.2 9.61 5.36 16.4 11.6 20.6 12.7 14.7 6.77 21.1 8.99 12.2 6.11 19.2 7.20
14 28.0 16.4 39.7 11.4 20.6 6.00 30.2 16.0 42.3 13.1 14.1 7.34 40.5 11.8 29.8 11.9 14.8 9.79
16 41.0 22.6 42.0 24.1 30.6 19.2 31.6 33.6 50.5 18.9 23.9 20.7 36.1 26.7 35.0 19.0 29.4 22.6
1Each data point represents an average value of duplicate analysis on each of 2 replicates from 1 blend.
10 12 14 16 DAYS ON ICE AFTER TREATMENT
- 19 -
FIG 4 - LOG (l+ngTNA-N) OF ICED COD 1 8
MA-(CONTROL)
A NB-(3Z KS) O NC-(1Z MC + lz CIT)
• ND-(1Z MC + 3Z KS)
NE-(1Z MC + 3% XS + 1Z CIT)
• NF-(3z KS ICE)
15 Mg tna cutoff _
.,..-- ...," 4 .......— ,....
.-''''
..e, .X.-',..
•
„ra' 7., : -,---- __A--------411 . 47/ ,----
/ r'./ / /7 r / rd/ /1
1.6
1.4 ,/
2
▪
83
;82.8
82.6
82.4
82.2
82 18 12 14 16
DAYS ON ICE AFTER TREATMENT
\ F r I Er
- 20 -
a
3.3.4 Moisture
Generally moisture increased slightly during the storage period in
all samples except MF which decreased (Table 8 and Figure 5). Two way
analysis of variance of moisture data from days 5 to 16 indicated that
MF was significantly lower than all other treatments (P<0.05) further
supporting the observation that sorbate-ice stored fish suffered from
slight freezing due to the depressed melting point of the chemical ice.
FIG 5 - AUERAGE FLESH MOISTURE 84 4
84.2
84
83.8
283.6 /
\I .// ,
;183.4 t\fri
W83.2 /
• MA-(CONTROL)
A MB-(3z KS) ❑ MC-(1z MC + 1 CIT)
• MD-(3z MC + 3% KS)
C) ME-(1z MC + 3z KS + lz CIT)
• MF-(3z KS ICE)
- 21 -
TABLE 8. Moisture Content (%) of Iced Gutted Cod
Days Post Mortem
MA Water Dip
MB Sorbate Dip
MC Methocel + 1% Citric Acid
MD Methocel + 3% Sorbate
ME Methocel + 3% Sorbate + 1% Citric Acid
MF Sorbate Ice
0 83.0 83.3 82.3
5 83.2 83.3 83.3 83.4 82.9 81.3 81.0 83.0 82.5 83.4 81.3 82.3 83.3 82.9 82.6 82.9 82.5 83.1
7 83.5 83.2 82.5 84.0 82.2 82.9 82.0 82.9 83.8 82.7 83.9 82.9 81.9 83.5 83.0 83.5 83.2 82.0
9 83.8 83.6 82.7 83.1 82.5 82.3 83.4 83.8 82.9 82.4 83.8 82.9 82.8 83.3 83.1 83.6 84.0 83.4
12 83.5 83.7 83.5 83.0 83.1 82.7 82.0 83.4 82.9 83.1 82.1 82.8 84.1 83.4 81.7 83.0 82.9 82.3
14 84.4 82.6 84.5 83.5 83.7 82.4 84.0 83.5 83.7 83.5 84.6 82.6 83.7 83.1 83.7 83.7 83.5 82.6
16 84.8 83.9 83.5 83.7 84.7 82.0 84.1 84.6 84.6 84.7 83.7 82.4 83.6 83.9 83.8 83.3 83.7 82.8
Average of 2 determinations on each blend.
- 22 -
3.3.5 Sensory Evaluation
Parametrically analyzed data (analysis of variance, Tables 9 and 10)
indicate that on day 9 odour of the day 0 reference was significantly
better than all other samples. Flavour of "R" was better than MA and MB
but not MF. Non-parametrically, odour of "Rn was better than MB but no
differences were found for flavour.
On day 12, "R" was superior in odour and flavour by both
statistical comparisons. At 14 days, however, odour of all samples was
different and declined in quality as R > MF > MB > MA. Flavour of MF
was not different from "R", parametrically (Table 10), but was inferior
non-parametrically (Table 11). Sorbate dipped cod (MB) and the control
(MA) were significantly poorer in flavour than "R" or MF verifying the
loss of sorbate effect in MB samples by day 14.
TABLE 9. Parametric Analysis (ANOVA) of Cooked Cod Fillets
(Best to Poorest Quality)
Day 9 Ra MFb MAb MBb
(3.62) (5.92) (6.24) (7.31)
Day 12 Ra MBb mpb MAb
(2.65) (5.41) (5.44) (7.15)
Day 14 Ra MFb MBc MAd
(2.95) (5.42) (7.22) (9.31)
*Parametric ANOVA analysis (P<0.05)
- 23 -
TABLE 10. Flavour of Cooked Cod Fillets
(Best to Poorest Quality)
Day 9
Day 12
Day 14
Ra (4.08)
Ra (2.97)
Ra (3.34)
mFab
(5.38)
MFb (5.34)
MAb (6.00)
MBb (6.61)
MBb (6.25)
MAb (6.98)
MAb (8.82)
MFa MBb (4.47) (7.68)
*Parametric ANOVA analysis (P<0.05)
TABLE 11. Non-Parametric Results of Sensory Evaluation
Day Odour
9 "R" sig. better than MB
12 "Rn sig. better than all treatments
14
All treatments sig. different from each other, ie. from best to poorest: Ra mFb MBc mAd
Flavour
No sig. differences
"R" sig. better than all treatments
nRn sig. best. MF sig. second best, ie. from best to poorest: Ra MFb MBc MAc
3.3.6 Loss of Potassium Sorbate from Chemical Ice
One kilogram of ice made from a 3% potassium sorbate solution was
allowed to thaw in a Buchner funnel. Concentration of sorbate in
collected 20 ml portions of drip is shown in Figure 6. Initial
concentrations were between 5 and 6% sorbate; original concentration
(3%) was reached once 40% of the ice had melted. This pattern of
sorbate loss is ideal for storage of fish. Release is elevated during
the initial storage period but is never lost completely, ie. decline
after the maximum is almost linear providing some sorbate to the fish
during the entire melt process. Melting temperature of the ice at the
beginning of the test was measured at -3°C.
OF
X-S
OR
DA
TE
(z) IN
DR
IP
4_
- 24 -
FIG 6 - H-SORBATE IN DRIP FROM CHEMICAL ICE
ok
eie • ski
16 36 46 56 610 86 46 106
PERCENTAGE OF ICE MELTED 3.4 Conclusion
Potassium sorbate dip, with or without Methocel® 856, improved
shelf life of gutted cod on ice. The slow melting rate of ice imposed
during the experiment influenced the results. Sorbate alone had an
immediate effect which was gradually lost while Methocel®, not showing
immediate retardation of spoilage, maintained quality during the latter
period of storage. Data of previous experiments (12) where sorbate had
little effect on shelf life of cod on ice was collected under conditions
of more rapidly melting ice.
Citric acid had no positive effect and in fact may have accelerated
spoilage, especially in terms of discoloration. Sorbate ice was clearly
the most beneficial although part of the effect must have been due to
the depressed melting point and lower temperature affecting bacterial
- 25 -
and chemical spoilage. Freshly made 3% sorbate ice was found to melt
around -3°C. Concentration in the ice was probably too high, from a
temperature standpoint and from one of economical practicality.
The authors conclude that an optimal treatment for storing gutted
cod would likely be a sorbate dip (without a gel) and subsequent storage
in sorbic acid ice at a level of approximately 1%. Such treatment would
allow for continuous bathing of the fish with sorbate thereby maximizing
effect with least effort.
4.0 ItEFERENCES
- 26 -
4.0 REFERENCES
1. Chemical Rubber Company, 1968. In Handbook of Food Additives, 2nd
Edition, Volume 1, T.E. Furia (ed.), CRC Press, Florida.
2. Sofos, J.N., F.F. Busta and C.E. Allen, 1979. Botulism control by
nitrite and sorbate in cured meats: A review. J. Food Prot. 42:9.
3. Blocher, J.C., F.F. Busta and J.N. Sofos, 1982. Influence of
potassium sorbate and pH on ten strains of type A and B Clostridium
botulinum. J. Food Sci. 47: 2028-2032.
4. Beauchat, L.R., 1980. Comparison of anti-Vibrio activities of
potassium sorbate, sodium benzoate, and glycerol and sucrose esters
of fatty acids. Appl. Environ., Microbiol. 39: 1178.
5. Park, H.S. and E.H. March, 1972. Inactivation of Salmonella
typhimurium by sorbic acid. J. Food Technol. 35:532.
6. Moustafa, H.R. and E.B. Collins, 1968. Effects of selected food
additives on growth of Pseudomonas fragi. J. Dairy Sci. 52:335.
7. Robach, M.C., 1979. Influence of potassium sorbate on growth of
Pseudomonas putrefaciens. J. Food. Prot. 42:312.
8. Robach, M.C., 1978. Effect of potassium sorbate on growth of
Pseudomonas fluorescens. J. Food Sci. 43:1886.
9. Robach, M.C. and C.S. Hickey, 1978. Inhibition of Vibrio
parahaemolyticus by sorbic acid in crab meat and flounder
homogenates. J. Food Prot. 41:699.
- 27 -
10. Chung, Y.M. and J.S. Lee, 1981. Inhibition of microbial growth in
English sole (Parophrys retulus). J. Food Prot. 44:68.
11. Debevere, J.M. and J.P. Voets, 1972. . Influence of some
preservatives on the quality of prepacked cod fillets in relation
to the oxygen permeability of the film. J. Appl. Bacterial.
35:351-356.
12. Shaw, S.J., E.G. Bligh and A.D. Woyewoda, 1983. Effect of
potassium sorbate application on shelf life of Atlantic cod (Gadus
morhua). Can. Inst. Food Sci. Technol. J. 16:237-241.
13. Anonymous, 1983. Fish bleeding, sorbate preservation studied at
Gloucester Lab. Marine Fisheries Rev. 45(3):24.
14. Regenstein, J.M. and C.E. Regenstein, 1981. The shelf life
extension of haddock in carbon dioxide-oxygen atmospheres with and
without potassium sorbate. Western European Fish Technologists'
Assoc., 11th annual meeting, Copenhagen.
15. Statham, J.A. and H.A. Bremner, 1983. Effect of potassium sorbate
on spoilage of Blue Grenadier (Macruronus norvaezelandiae) as
assessed by microbiology and sensory profiles. J. Food Prot.
46:1084-1091.
16. Bremner, B.A. and J.A. Statham, 1983. Effect of potassium sorbate
on refrigerated storage of vacuum packed scallops. J. Food Sci.
48:1042-1047.
17. Statham, J.A., 1983. Sorbate extends shelf-life of scallops.
Australian Fisheries, July.
18. Wessels, J.P.H., E. Lamprecht, J. Rodrigues and C.K. Simmonds,
1972. Preservation of hake in treated ice. J. Food Technol.
7:203.
- 28 -
19. Fey, M.S. and J.M. Regenstein, 1982. Extending shelflife of fresh
wet red hake and salmon using CO2-02 modified atmosphere and
potassium sorbate ice at 1°C. J. Food Science 47:1048.
20. Regenstein, J.M., H.O. Hultin, M.S. Fey and S.D. Kelleher, 1980.
Utilization of red hake. Marine Fish. Rev. 42(1):32-37.
21. Fey, M.S. 1980. Extending the shelflife of fresh fish by potassium
sorbate and modified atmosphere at 0-1 °C.
22. Gill, T.A. and J.W. Thompson, 1984. Rapid, automated analysis of
amines in seafood by ion-moderated partition HPLC. J. Food Science
49:603.
23. Woyewoda, A.D. and S.J. Shaw, 1984. Operational groundfish grading
and laboratory methods guide, Technical Studies Interim
Manuscript. no. 503, Fisheries and Oceans, Halifax.
24. Dyer, W.J., 1959. Report on Trimethylamine in Fish. J. AOAC
42:292.
25. Tozawa, H., R. Enokiharo, and R. Amano. 1971. Proposed
Modification of Dyer's Method for Trimethylamine Determination in
Cod Fish. In Fish Inspection and Quality Control. R. Rreuzer
(ed.), Fishing News (Books) Ltd., London, p 187-190.
26. Larmond, E. 1977. Laboratory Methods for Sensory Evaluation of
Food, Canada Dept. Ag. Pub., 1637.
27. Siegel, S. 1956. Non-parametric Statistics. McGraw Hill, New
York, p 166.
28. APHA Intersociety/Committee on Microbiological Methods for Foods
1976. Recommended general methods for the examination of fish and
- 29 -
fish products. In Microbiological Examination of Foods (M.L.
Speck, ed.), American Public Health Assoc., Washington, D.C.
29. Woyewoda, A.D., R.E. Spencer, T.A. Gill and R.G. Ackman. 1985.
Characteristics of autumn soft-textured cod. Project Report No.
109, Fisheries and Oceans, Development Branch, Scotia-Fundy Region,
Halifax, N.S.
Grading Guide for Iced Groundfish
ROUND FISH Grade A Grade S Grade C Reject
handling practise fish properly gutted and washed
fish not properly gutted and washed
temperature temperature of 4'C (40'?) or less
temperature greater than 4'C (40'F)
texture of fish flesh is firm and resilient, and springs back immediately when released
reasonably firm, some loss of resiliency, thumb indentations slowly fill out
moderately soft thumb indentations may remain in flesh
excessively soft flesh
ROUND FISH 0 1 2 3 R
neck odour characteristic odour, fresh
neutral, total absence odour, characteristic odour no longer detect- able but off-odours haven't developed
off-odour, sour, putric bilgy, ammonia, unnatural odour
gill odour characteristic of species, fresh
neutral, total absence of odour, characteris- tic odour no longer detectable but off-odours haven't developed
faint sour odour slight to moderate sour odour
very sour, strong or putrid
general appearance
.
good overall appearance skin lustrous and shiny no fading
good overall appearance very alight bleaching of akin
some loss of metallic lustre, some bleaching
.
bloom gone from skin, color faded and bleached
eyes
.
clear, bright, convex eyes
slightly sunken, or somewhat dull ,
dull and/or cloudy
. .
very dull, sunken, and cloudy
gill appearance bright red, little mucus
red, some mucus pinkish red to brownish same mucus
brown, may be covered with mucus •
FILLETS .
Grade A • Grads 2 Grade C Reject
blood clots no blood clots g than 1/2 cm circle
no combination of blood clots exceeding 4 sq ce total area (4, 1x1 squares on 11P0 measuring template) in any one fillet
one or any combinations of blood Clots which exceed 4 square cm total area in any cms fillet
texture of fillets uniform, firm fillets with little or slight gaping
reasonably floe, resilient flesh with moderate gaping
moderately soft flesh with excessive gaping. Ragged cc torn fillets permitted
excessively soft flesh wit= unacceptable amount of gaping
chalkiness and/or jolliness no jelly. none or slightly chalky
slightly jellied or moderately chalky
moderately jellied or heavy chalky
heavy jellied. Do not reject based on chalkiness
discoloration no single discoloration, nor any combination, exceeding 2 sq cm (i.e. two, 1x1 cm squares on grid of DFO measuring template) in any one fillet
no single discoloration, nor any combination, exceeding S sq cm in any one fillet
any single discoloration, or any single discoloration or combination which exceeds 50% of the total surface of any one fillet
combination the total surface area of which does not exceed SO% of the total surface area of any one fillet
fillet odour odour characteristic of species
neutral, total absence of odour
slight off-odour, but not objectionable
any objectionable odour
C.I.F.T. 1985
N
Species: Date Landed: Date Inspected,
Name of Vessels
Name of Fisherman:
Name of Landing Site:
Inspection Location:
Type of Gear:
CPV Number:
Total Catch (lbe)t Sample Size (No):
Fish (No.)
Bled
Gutted
Washed
Iced/Temp *11'
Texture . .
Grade (Table 1)
Odour at Neck . . ... ■
Odour of Gills -
General Appearance
Eves , ,
Color of Gills ...
. .
. , TOTAL POINTS
Average (Table 2) - . . .
Grade A (Average <2) —
Grade B (2.0-2.1) .
Grade C.(2.g1.2.81 . . . 1 .
Grade (Table 2)
Blood Clots
Texture
Diecolourations
Odour
Grade (Table 3)
FINAL GRADE 1111111
Grade A B C
Reject
Number of Fish
Percent (11)
ret
03 E-1
Comments'
Name Date
Evaluate each coded sample in order for odour and flavour. Please comment on unusual (uncharacteristic) aspects of any samples.
Place a slash on each grading line for each sample similar to the example below:
EXAMPLE Like Extremely
X"-
314 po 404 I I ACCEPTABILITY
97`
Dislike Extremely
PLEASE DO ALL SAMPLES FOR EACH CATEGORY
N.B. THE REFERENCE TS OF GOOD QUALITY! PLEASE TASTE TT
!!! BEFORE EACH !!! CODED SAMPLE.
ODOUR Typical Fresh
strong ammonia Putrid or
non-typical (describe)
FLAVOUR
Sea-fresh
anER12 Putrid
Objectionable or
Neutral uncharacteristic
tasteless (describe)
COMMMITS