32 Proben verpackten Frischfischs in Selbstbedienungspackungen, 16 Seelachs- und 16 Rotbarschproben aus deutschen Supermärkten wurden mit physikalischen, chemischen, mikrobiellen und sensorischen Methoden untersucht. Ziel der Untersuchung war dieWertung von Untersuchungsmethoden zur Qualitätsbestimmung. Es

zeigte sich, daß neben der sensorischen Beurteilung die Bestimmung des TVB-N geeignet ist, die Qualität dieser Produkte zu beurteilen

Lehmann, Ines

English

Aquatic Commons

Inf. Fischwirtsch. 44(4), 1997 183
Introduction
On the German market the share of fresh fish in total
fish consumption amounts only to about 15 %. To sell
this fish in packages for self-service is a goal for most
sellers. Expensive trained personnel for fish selling is
no longer needed, and customers are able to choose the
product they want without any loss of time. In a lot of
European countries it is common to find pre-packaged
fresh fish in supermarkets. In Germany only a few
manufacturers of such products can be found. These
products are therefore rarely available on the market.
Fish fillet packaged under modified atmosphere,  under
vacuum or wrapped in foil is offered. The last type of
product is only to be used to carry the fish home, unpack
it there and eat it soon. For packages under vacuum
and modified atmosphere a  shelf-life of up to six days
in retail were pretended, if the package is stored under
+2 °C. But this temperature is not often reached in
German households, because the refrigerators have
usually temperatures about +7 to 10 °C. At these
temperatures the fish will spoil soon.
In cooperation with the Federal Federation of the
German Fish Industry several products were looked at
to find out what kind of parameters and criteria describe
freshness or quality of these products and whether there
was a difference between the several kinds of packaging.
Materials and methods
Samples
32 products were investigated, 16 samples of redfish,
16 saithe samples. Six products were vacuumpacked,
ten wrapped in foil and sixteen were packaged under
modified atmosphere. Every sample existed of ten
packages. The products were bought  on retail level in
German supermarkets. Immediately after the purchase
the temperature of the fillets was measured and then
the samples were transported to the institute in a cooling
box with a temperature of +1 to 4 °C. In the institute
the products were kept cool in a cold-storage room at
+2 °C. Temperatures of the packages were between
Pre-packaged fresh fish 
Searching for quality descriptive criteria
Ines Lehmann, Institute for Biochemistry and Technology
32 samples of pre-packaged fresh fish fillets, 16 saithe and 16 redfish samples were bought in German supermarkets
and investigated with physical, chemical, microbiological and sensory methods to find out, which criteria is the
most suitable for quality description. It was shown that sensory assessment besides determination of TVB-N value
is the best criteria to evaluate quality of these products.
Frischfisch in Selbstbedienungspackungen – auf
der Suche nach Untersuchungsmethoden zur
Qualitätsbeschreibung
32 Proben verpackten Frischfischs in Selbstbedienungs-
packungen, 16 Seelachs- und 16 Rotbarschproben aus
deutschen Supermärkten wurden mit physikalischen,
chemischen, mikrobiellen und sensorischen Methoden
untersucht. Ziel der Untersuchung war die Wertung von
Untersuchungsmethoden zur Qualitätsbestimmung. Es
zeigte sich, daß neben der sensorischen Beurteilung
die Bestimmung des TVB-N geeignet ist, die Qualität
dieser Produkte zu beurteilen.
-2,3 °C and +8,4 °C at time of buying, most of the
samples were about +2 °C. The samples were
investigated at the day they were bought or the day after
on the assumption that the consumers would not store
the fish more than one day. For physical, chemical and
sensory  investigations five packages were used, for
microbiology three packages. This was not a representative
examination, but a first attempt to find out what  product
quantity the German consumers get.
Methodologies
Physical
As physical determinations the pH-value and the
Fishtester-value were measured, determined by the
German Intelectron Fishtester VI.
Chemical
The chemical determinations were first to find out the
content of  the total volatile bases nitrogen, the TVB-N,
with two methods. The first method is a steam
destillation of an acidified perchloric acid-extract
(Anon.L.10.00 3). The second method is a steam
distillation of the minced fillet according to Antona
(Antonacopoulus, 1960), which is often used by the
German fish industry.
The value of  tri- and dimethylamine and trimethylamine
oxide,  TMA-N, DMA-N,  and TMAO-N  were
determined by gaschromatography after extraction with
perchloric acid (Anon.). Chloride was investigated
titrimetrically, ethanol, D- and L-lactic acid and proof
Inf. Fischwirtsch. 44(4), 1997184
for frozen/unfrozen fillets were
determined enzymatically (Reh-
bein 1979). Biogenic amines
were investigated by HPLC,
formaldehyde photometrically.
Microbiological
Each package was divided into
nine samples. Subsamples
were homogenizied and
diluted. Determined were the
total viable counts on plate
count agar, Shewanella,
Enteriobacteria, Lactobacilli,
Clostridia and Photobacteria
on selective media.
Sensory
For sensory investigations the fillets
were cooked by microwave without
any additives. For comparison with
unpackaged fish fresh fish from the
fishmarket in Hamburg was bought
at the day the investigations were
done and filleted in the institute. The
members of the panel were first asked
for their preference for one of the
samples. Both samples, the pre-
packed and unpackaged, were not
marked. In the second the members
of the panel were asked to judge the
fish samples with a sensory
assessment with scale. The evaluation
follows a scale with 9 points, where
9 to 7 points characterize the best
sensory quality, 6 to 4 points medium
quality and if getting 3 points or less
the fish is unfit for human
consumption (Paulus et al. 1969).
Consideration was given to
appearance, smell, consistence and
taste were looked at.
Results
Sensory
The sensory preference test showed
that nearly in all cases the fish from
the fishmarket was prefered (figures
1 and 2). The panellists were able to
choose more than one of the samples.
Also, the panellists were able to find
out which the pre-packed sample was.
Va
c-
SB
S1
Va
c-
SB
S4
Va
c-
SB
S9
M
AP
-S
BS
2
M
AP
-S
BS
3
M
AP
-S
BS
11
M
AP
-S
BS
12
M
AP
-S
BS
13
M
AP
-S
BS
14
M
AP
-S
BS
15
M
AP
-S
BS
16
W
ra
-S
BS
5
W
ra
-S
BS
6
W
ra
-S
BS
7
W
ra
-S
BS
8
W
ra
-S
BS
10
pre-packed
unpackaged
number of persons0
2
4
6
8
10
12
pr
ef
er
en
ce
packaging / sample number
pre-packed
unpackaged
number of
persons
Fig. 1: Sensory preference for saith
M
AP
-S
BS
2
M
AP
-S
BS
3
M
AP
-S
BS
11
M
AP
-S
BS
12
M
AP
-S
BS
13
M
AP
-S
BS
14
M
AP
-S
BS
15
M
AP
-S
BS
16
Va
c-
SB
S1
Va
c-
SB
S4
Va
c-
SB
S9
W
ra
-S
BS
5
W
ra
-S
BS
6
W
ra
-S
BS
7
W
ra
-S
BS
8
W
ra
-S
BS
10
0
1
2
3
4
5
6
7
8
po
in
ts
M
AP
-S
BS
2
M
AP
-S
BS
3
M
AP
-S
BS
11
M
AP
-S
BS
12
M
AP
-S
BS
13
M
AP
-S
BS
14
M
AP
-S
BS
15
M
AP
-S
BS
16
Va
c-
SB
S1
Va
c-
SB
S4
Va
c-
SB
S9
W
ra
-S
BS
5
W
ra
-S
BS
6
W
ra
-S
BS
7
W
ra
-S
BS
8
W
ra
-S
BS
10
packaging / sample number
unpackaged
pre-packed
Fig. 3: Sensory valuation of saithe
Va
c-
SB
R1
Va
c-
SB
R4
Va
c-
SB
R9
M
AP
-S
BR
2
M
AP
-S
BR
3
M
AP
-S
BR
11
M
AP
-S
BR
12
M
AP
-S
BR
13
M
AP
-S
BR
14
M
AP
-S
BR
15
M
AP
-S
BR
16
W
ra
-S
BR
5
W
ra
-S
BR
6
W
ra
-S
BR
7
W
ra
-S
BR
8
W
ra
-S
BR
10
pre-packed
unpackaged
number of persons0
2
4
6
8
10
12
pr
ef
er
en
ce
packaging / sample
number
pre-packed
unpackaged
number of
persons
Fig. 2: Sensory preference for redfish
Inf. Fischwirtsch. 44(4), 1997 185
 The sensory valuation for saithe is
shown in figure 3. The values are the
average of the four investigated
attributes appearance, smell, texture
and taste. The samples are sorted for
the different kinds of packaging. The
first eight are packaged under
modified atmosphere (MAP), the next
three vacuum-packaged  (Vac) and the
last five wrapped in foil (Wra). The
majority of the pre-packed fish
samples were of medium quality,
getting 4 to 6 points. Four samples
were in the area above at 7 to 9 points,
which indicates good qualities.
The results for redfish are worse than
for saithe (figure 4). Three samples
are between 7 and 9 points. One
sample received only 3 points, that
means that this sample was unfit for
human consumption. The other
samples were in the middle. The
samples were also sorted for the kind
of packaging. Neither for redfish nor
for saithe a relationsship with the
kind of packaging is obvious.
Considering the shelf-life given by
the producers, up to five days after
purchase, it is obvious that a lot of
products wouldn‘t be eatable any
more at that point of time.  Two
samples, packed under modified
atmosphere,  were stored up to the
end of shelf-life and then opened.
The appearance and smell indicated
total spoilage, so that the samples
were not analysed.
Microbiology
The data for microbiological
investigations show that there was no
significant correlation between
analysed total viable count and
specific spoilage organisms and other
determined criteria. Lactobacilli and
Clostridia were not important for pre-
packed fish. Here also no difference
between the different kinds of
packaging was observed.
Chemistry
For TVB-N only a few samples
exceeded the regulated limiting
content of 35 mg/100g wet weightFig. 6: Content of TVB-N for redfish (mg/100 g w.w.)
0
10
20
30
40
50
60
70
M
AP
-S
BR
2
M
AP
-S
BR
3
M
AP
-S
BR
11
M
AP
-S
BR
12
M
AP
-S
BR
13
M
AP
-S
BR
14
M
AP
-S
BR
15
M
AP
-S
BR
16
Va
c-
SB
R1
Va
c-
SB
R4
Va
c-
SB
R9
W
ra
-S
BR
5
W
ra
-S
BR
6
W
ra
-S
BR
7
W
ra
-S
BR
8
W
ra
-S
BR
10
m
g/
10
0g
 w
.w
. TVB-N
(Per)
Fig. 5: Content of TVB-N of saithe (mg/100g w.w.)
0
10
20
30
40
50
60
70
M
AP
-S
BS
2
M
AP
-S
BS
3
M
AP
-S
BS
11
M
AP
-S
BS
12
M
AP
-S
BS
13
M
AP
-S
BS
14
M
AP
-S
BS
15
M
AP
-S
BS
16
Va
c-
SB
S1
Va
c-
SB
S4
Va
c-
SB
S9
W
ra
-S
BS
5
W
ra
-S
BS
6
W
ra
-S
BS
7
W
ra
-S
BS
8
W
ra
-S
BS
10
m
g/
10
0g
 w
.w
.
TVB-N (Per)
TVB-N (Ant)
Fig. 4: Sensory valuation of redfish
M
AP
-S
BR
2
M
AP
-S
BR
3
M
AP
-S
BR
11
M
AP
-S
BR
12
M
AP
-S
BR
13
M
AP
-S
BR
14
M
AP
-S
BR
15
M
AP
-S
BR
16
Va
c-
SB
R1
Va
c-
SB
R4
Va
c-
SB
R9
W
ra
-S
BR
5
W
ra
-S
BR
6
W
ra
-S
BR
7
W
ra
-S
BR
8
W
ra
-S
BR
10
0
1
2
3
4
5
6
7
8
po
in
ts
M
AP
-S
BR
2
M
AP
-S
BR
3
M
AP
-S
BR
11
M
AP
-S
BR
12
M
AP
-S
BR
13
M
AP
-S
BR
14
M
AP
-S
BR
15
M
AP
-S
BR
16
Va
c-
SB
R1
Va
c-
SB
R4
Va
c-
SB
R9
W
ra
-S
BR
5
W
ra
-S
BR
6
W
ra
-S
BR
7
W
ra
-S
BR
8
W
ra
-S
BR
10
packaging / sample number
unpackaged
pre-packed
Inf. Fischwirtsch. 44(4), 1997186
(w.w.) for saithe and 25 mg/100g w.w. for redfish, if
the §35 method is used (Anon. 1995) (figures 5 and 6).
Samples with high TVB-N content also had high content
of DMA-N and TMA-N.
The content of TVB-N determined with the second, the
direct ditillation, was always higher than with the § 35
method. Therefore the § 35 method should be preferred
because of getting more precise values. Here also no
dependence of packaging to the content of TVB-N,
DMA-N and TMA-N was seen. If  the TVB-N content
is compared to the sensory notes it is obvious that
samples with high content of TVB-N were scored of
being of low quality. It is obvious that high TVB-N
content correspond to low sensory notes. For example
redfish sample number seven had a very high TVB-N
content. The sensory note was very low and the fish
was found not to be edible, this sample reached only
three points in the sensory investigation.  Not the kind
of packaging but the quality of the raw material is
decisive for quality.
The other chemical parameters like content of ethanol
or lactic acid are also suitable for describing quality.
The physical parameters are not suitable because of
getting no distinct results. Sensory analysis and
determination of TVB-N are most suitable for the
description of quality of pre-packaged fish fillet.
Conclusions
Suitable criteria to evaluate quality of pr-packaged fish
fillets are sensory investigations and the determination
of the value of TVB-N. Most of the other determined
criteria confirmed the results got by these investigations,
but are on their own not sufficent to describe the quality
of pre-packaged fish.
Sensory investigations showed that pre-packaged fish
has a different taste to unpackaged fish. All of the
panellists find out the pre-packaged fish. No difference
between the several kinds of packaging was seen.  To
sell these products with good quality on the German
market it is necessary to inform retailers and costumers
about correct handling of these products. If the raw
material is of excellent quality, the cooling chain is not
interrupted, the retailers and the consumers do know
how to handle such a product, then these product could
get a higher market share in German supermarkets.
References
Antonacopoulus, N.: Verbesserte Apparatur zur quantitativen
Destillation wasserdampfflüchtiger Stoffe, Z. Lebensm. Unters.
Forsch., 113: 113-116; 1960
Rehbein, H.: Verfahren zur Unterscheidung gefrosterter/aufgetauter
Filets von Naßfischfilets, Inf. Fischw., 26: 113-119; 1979
Paulus, K.; Gutschmidt, J.; Fricker, A.: Karlsruher Bewertungsschema
- Entwicklung, Anwendbarkeit, Modifikationen, Lebensm. Wiss. u.
Technol., 3: 132-139; 1969
Anon. L 10.00 3: Amtliche Sammlung von Untersuchungsverfahren
nach § 35 LMBG; Bestimmung des Gehaltes von flüchtigen
stickstoffhaltigen Basen (TVB-N) in Fischen und Fischerzeugnissen
Anon.L.10.00 4: Amtliche Sammlung von Untersuchungsverfahren
nach § 35 LMBG; Bestimmung des Gehaltes von Trimethylamin-
Stickstoff (TMA-N) in Fischen und Fischerzeugnissen
Anon.: Entscheidung der Kommission vom 8.März 1995 über TVB-
N-Grenzwerte für bestimmte Kategorien von Fischereierzeugnissen
und die angewendeten Analysenmethoden, 95/362


Pre-packaged fresh fish - Searching for quality descriptive criteria

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Pre-packaged fresh fish - Searching for quality descriptive criteria

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