The combination of microbiological, biochemical, and quality index methods in quality evaluation of pacific white shrimps (Litopenaeus vannamei) preserved at 0°C
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Life ScienceS Agriculture
DOI: 10.31276/VJSTE.63(2).45-51
The combination of microbiological, biochemical,
and quality index methods in quality evaluation of pacific
white shrimps (Litopenaeus vannamei) preserved at 0°C
Nhat Tam Le1*, Nguyen Que Anh Huynh1, Nhu Khue Doan1, Thuy Xuan Uyen Phan1, Ba Thanh Nguyen1,
Sao Mai Dam1, Thi Van Thi Tran2, Le phuong Lien Nguyen3, Van Hai Chu4, Huynh Anh Vu Truong4
1Institute of Biotechnology and Food Technology, Industrial University of Ho Chi Minh city, Vietnam
2Hue University of Science, Hue University, Vietnam
3Department of Refrigeration and Livestock Product Technology, Szent István University, Budapest, Hungary
4Center of Analytical Services and Experimentation Ho Chi Minh city, Vietnam
Received 28 May 2020; accepted 21 August 2020
Abstract:
In this study, the sensory, microbiological, and biochemical qualities were used to examine the quality of Pacific
white shrimps (Litopenaeus vannamei) preserved at 0°C during a 10-day period. The sensory quality was evaluated
by a quality index (QI) that resulted from a quality index method (QIM) scheme. Meanwhile, the total viable count
(TVC) and K-value were used to assess the microbiological and biochemical qualities of the shrimp. On day 9, the
results from TVC and QIM have shown that the shrimp showed signs of spoilage, corresponding to a log CFU/g of
6.4 and a QI of 21.37, which is unacceptable to consumers. The QI increased linearly with storage days therefore the
remaining shelf-life of the shrimp was estimated from a linear regression equation. In particular, this study found
a linear relationship between QI, K-value, and hypoxanthine content. Furthermore, hypoxanthine itself could be
considered as an independent quality index like the K-index. In conclusion, the quality of Pacific white shrimp was
categorized into four different classes: excellent, good, acceptable, and moderately acceptable, based on its sensory
and biochemical quality indicators.
Keywords: hypoxanthine, K-value, pacific white shrimp, QIM.
Classification number: 3.1
qualities are established based on these impact factors [2].
The organoleptic quality assessment method is based on
Introduction
Shrimp are an important source of seafood with
variations of sensory properties including the color, smell,
considerable nutrition and economic value in many
taste, and texture. The intensity rating method is considered
countries around the world [1]. In Vietnam, Pacific white
shrimp (Litopenaeus vannamei) have achieved a high
the most popular at present, followed by the Torry scheme,
quantitative descriptive analysis (QDA), and QIM, to name
export turnover rate in the seafood industry in recent years.
a few. Among those, QIM is predicted by Hyldig as the
However, the method used to assess the quality of shrimp
potential method for quality assessment in the European
in particular, and seafood in general, is not consistent with
Community. QIM was developed by the Tasmanian Food
the current methods in other parts of the world. The quality
Research Unit in Australia [4] and is continually being
developed. QIM possesses many advantages such as short
training time, short evaluation time, and high reliability in
assessing the freshness of seafood preserved in ice [5]. The
difference between QIM and other methods is that QIM is
built to evaluate the sensory changes of specific species.
QIM focuses on the correlation between the quality index
of post-harvest shrimp decreases with storage time due to
the impact of three main factors, which include the activity
of endogenous enzymes, microorganisms, and chemical
reactions. These activities alter the sensory state, chemical
composition, as well as the total amount of aerobic
microorganisms in shrimp [2, 3]. Therefore, methods that
assess sensory, chemical, microbiological, and physical
*Corresponding author: Email: [email protected]
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Reagents
and the storage time expressed via a linear regression
equation. Thus, QIM allows an estimation of the remaining
shelf-life of seafood. So far, QIM-Eurofish has developed
28 QIM schemes mainly for fish, shrimp, and squid species.
However, the QIM scheme for Pacific white shrimp has
not yet been developed [6]. In Vietnam, shrimp quality is
assessed according to TCVN 3276-89 [7]. This standard is
generally applied to all shrimp species and is not an intensity
rating method, however, it is a semi-quantitative assessment
that describes changes in the properties of shrimp. Therefore,
quality results from TCVN 3276-89 do not resemble those
obtained by the rating method used in importing countries.
This leads to disputes over quality and financial losses for
exporting enterprises. After shrimp die, the process of self-
decomposition takes place immediately, which is followed
by the process of decomposition [8]. This autolysis is
caused by endogenous enzymes in the shrimp and results
in the release of nucleotides and its derivatives. In 1959,
Saito and his colleagues introduced the “K-value”, which is
calculated based on nucleotides and their derivatives. The
“K-value” has been formulated as an index of freshness
in seafood [9]. Unlike quality indicators such as TVB-N,
TMA-N, or histamine that are suitable for assessing quality
during the decomposition stage, the K-value tends to
linearly correlate with storage time [10-15]. This allows
researchers to develop a regression equation between the
QI and K-value.
Reagents
including
Adenosine-5’-triphosphate
(PubChem CID: 5957), Adenosine-5’-diphosphate
(PubChem CID: 6022), Adenosine-5’-monophosphate
(PubChem CID: 6083), Inosinmonophosphate (PubChem
CID: 8582), Inosine (PubChem CID: 6021), and
hypoxanthine (PubChem CID: 790) were purchased from
Sigma - Aldrich (Merck KGaA, Germany). Other reagents
such as methanol (PubChem CID: 887), ethanol (PubChem
CID: 702), and HPLC-grade water were bought from Merck
Vietnam Ltd. Co.
Determination of TVC
TVC was measured according to Leboffe and Pierce
(2015) [16]. In brief, 10 g of peeled shrimp were minced
and mixed with 90 ml of 0.9% NaCl solution and then
centrifuged at 3000 rpm at 30o
C for 5 min. The pour-plate
method using plate count agar was applied to determine
the total plate counts. The extract from the samples were
inoculated on agar plates and incubated at 30oC for 48 h
before the colonies were counted. The experiments were
repeated three times and the TVC values were expressed as
log CFU/g (colony forming units).
Development of QIM scheme
The QIM scheme was developed based on three main
steps according to Bernardi, et al. (2013) and Le, et al.
(2017) [17, 18], which include: (1) identification of quality
attributes, (2)mainsensoryevaluation, and(3)quantification
of the developed (sensory) QI, as mentioned below.
Therefore, this study aims to develop a complete
quality assessment process including the analytical
methods measuring the microbiological, biochemical, and
sensory changes. The expected findings include the quality
classification of Pacific white shrimp based on the QI and
K-value as well as the linear regression equations between
the quality indicators investigated.
Step 1 (preliminary program): three sensory experts
observed all the changes in quality attributes (e.g. shape,
odor, texture, eyes, shell color, and formation of black spots
on the abdomen, body, tail). The terms were noted from
direct observation [18-20]. The CATA (check all that apply)
method was applied to select the most suitable descriptive
terms from the preliminary terminology. Each attribute was
then given a score from 0 to 3, with a low score suggesting
a high quality level.
Materials and methods
Shrimp collection and storage
Healthy Pacific white shrimp were purchased from the
Binh Dien market in Ho Chi Minh city. The shrimp samples
were then washed with filtered water and packaged in
polyethylene zipper bags (26.8×27.9 cm) (Alcoa Products
Inc., VA, USA). These sample bags were placed directly in
a polystyrene container containing shaved ice with a ratio
of 1 shrimp to 2 shaved ices (w/w) and were delivered to
the testing facility within 2 hours. At the testing facility,
the sample bags were preserved at 0°C in a refrigerator for
research purposes.
Step 2 (main program development and panel training):
the shrimp samples were evaluated daily for ten consecutive
daysat0°C.Thestartofday0wasdeterminedtoberightafter
the shrimp arrived at the testing facility. The examination
of the shrimp at different time points was conducted by six
sensory panelists for one month. The panelists evaluated
the samples and recorded the results without knowing the
storage time. This process ensured accuracy, reliability, and
minimized bias in data.
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Step 3 (quantification of the recorded sensory QI): this
step primarily involved quantification of the data collected
from the QIM scheme. The regression equation between
the days in storage and QI was developed to compare the
projected shelf life with actual shelf life of shrimps. The
data collected from ten different samples corresponded to
each of the 10-day storage periods.
Results and discussion
The change in TVC
The initial number of microorganisms in shrimp was
mainly from the breeding environment [23]. The shrimp
samples, after being washed with clean water, were stored
at 0°C and the TVC with a log CFU/g value of 4.7 was
recorded on day 1. The TVC values for the following days
2, 3, and 4 did not change significantly with 4.78, 4.89,
and 5.01 (log CFU/g), respectively. However, starting
from day 5, significant changes were observed (p<0.05).
The TVC value was 5.55 on day 5, 5.78 on day 6, 5.77
on day 7, 5.89 on day 8, 6.4 on day 9, and 6.4 on day 10.
The TVC values increased rapidly after day 4 for 10 days
and exceeded 6 log CFU/g on day 9. The value of 6 log
CFU/g is regarded as the limit allowed by the International
Commission on Microbiological Specifications for Foods
(ICMSF) for frozen shrimp. Thus, the shelf life of shrimps
was set at day 8. Two recent studies by Naik, et al. (2014)
[23] and Okpala, et al. (2014) [24] on black tiger and white
shrimp samples have also shown that the shelf life are 8
days and 7 days, respectively. This difference in shelf life
may be from different species, seasons, harvest techniques,
age, and physiological conditions [2]. Microbiological
changes in shrimp are closely related to sensory and
biochemical changes. In the autolytic stage, as mentioned
above, the main cause is due to the endogenous enzymes.
Some components that are quickly metabolized during this
period are ATP, glycogen that produces sweet IMP, and
hypoxanthine derivatives that produce a bitter taste [2]. A
decrease in pH, which is caused by lactic acid produced from
glycogen digestion, facilitates the hydrolysis of the proteins
of acidic enzymes. The hydrolysis of proteins forms basic
substances such as TVB and biological amines [25]. This
leads to the decomposition of proteins and lipids. This is the
source of the unique flavors such as alcohols and aldehydes,
especially aldehydes that have double bonds in the third
position [26, 27]. Biochemical changes also strongly occur
during the decomposition stage. TMA compounds have a
fishy smell, which are formed by the reduction of TMAO
and NH3 resulting from the metabolism of amine acids by
enzyme deaminases.
ATP, related compounds, and K-value
Nucleotides and related compounds including ATP,
ADP, AMP, IMP, inosine, and hypoxanthine were
measured by high-performance liquid chromatography
with a diode array detector (HPLC-DAD). In this method,
nucleotides and related compounds were extracted with
0.6 M perchloride acid and detected by the 2018 Cosmosil
application (Nacalai Tesque, Japan) and Veciana-Nogues, et
al. (1997) [21, 22]. In summary, 3±0.01 g of shrimp meat
was blended with 10 ml of 0.6 M perchloride acid for 10
min by vortex. The mixture was then centrifuged at 3000
rpm for 10 min to collect the supernatant. This process was
repeated three times. The extract was neutralized to pH 7.0
using 1 M KOH filtered through Whatman Grade 1 filter
paper (Sigma-Aldrich, Germany) and diluted to 50 ml by
volume. One milliliter of the diluted extract was uploaded
into an SPE C18 column (Agilent Technologies, USA) and
eluted with a 0.05 M K2HPO4 buffer to harvest 10 ml. Then,
50 µl of the harvested extract was injected into the column
for the analysis of nucleotides and related compounds by
HPLC. HPLC analyses were performed using an Agilent
1260 apparatus (Agilent Technologies, USA) equipped with
diode array detector (Agilent 1260 detector), 5C18-PAQ
column (size 5 mm, length 250 mm - 4.6 mm I.D) (Nacalai
Tesque, Japan) at 30oC. The mobile phase of 0.05 M K2HPO3
was controlled at a flow rate of 1 ml/min. Nucleotides and
related compounds were detected at a wavelength of 260
nm.
The K-value was calculated as the percent ratio of
inosine (HxR) and hypoxanthine (Hx) to the sum of ATP
and degradation products as shown below.
K-values(%)=100(inosine+hypoxanthine)/(ATP+ADP+
AMP+IMP+inosine+hypoxanthine).
Development of QIM scheme for the quality evaluation
Data analysis
of Pacific white shrimps
All experiments were conducted in triplicate. The
obtained data were preprocessed with Microsoft Excel
(version 2010) and analyzed using Statgraphics centurion
software. A linear regression model was fit to the data. The
significance level was at p<0.05.
Changes in sensory qualities such as color, odor,
and texture of head and tail were noted with preliminary
descriptive terms. The CATA method was applied to
select and arrange the terms in descending quality order as
described in Table 1 [28].
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Table 1. QIM scheme for Pacific white shrimp (Litopenaeus
vannamei).
Other shrimp samples with different storage times
were evaluated by the trained panel for ten consecutive
days. Changes in sensory attributes, corresponding QI, and
quality class from day 0 to day 10 are presented in Table 2.
Characters
Description
Score
Table 2. Sensory changes, QI, and Pacific white shrimp quality
Fresh ocean smell
0
1
classifications during storage at 0°C.
Lightly fishy smell, smell of seashells
Days
Descriptions
QI
Class
Odor
Meat
Neutral or slightly trimethylamine (TMA) 2
Shrimp has fresh ocean smell, blueish-gray head.
Roes begin to turn yellow. The head has no black
spots. Head is intact and tightly attached to the
body
Body is shiny gray and intact. The back is yellow.
Body has no black spots
Tail is gray, a bit purple at the top end and has no
black spots. Tail is attached to the body
Shell is hard and tough
Strong trimethylamine (TMA)
Gray, gray - green, no spot
Gray, gray - green, light yellow
Light black, scattered black spots
Black, large black spots
3
0
1
2
3
0
1
2
1
1.32
Head
Body
Meat is translucent, firm and elastic
Excellent
Shiny, gray, yellow, spotless
Gray, green, some spots
Shrimp has fresh ocean smell. Head is blueish-
gray. Roes are light yellow. Head has no black
spots. Head is intact and tightly attached to the
body
Body is shiny gray and intact. The back is yellow.
Body has no black spots
Tail is gray, a bit purple at the tip of the tail, and
has no black spots. Tail is attached to the body
Shell is less tough
Gray, slightly pink, scattered spots
2
2.90
Yellow, pink. Large black spots on the
body and legs
Color
3
Gray, purple, spotless
Gray, green, some spots
Green, pink, large black spots
Black
0
1
2
3
0
1
2
3
0
1
2
3
Meat is translucent, firm and elastic
Tail
Seashell smell, lightly fishy. Roes are yellow
Head is blueish-gray, lightly loose from the body,
and has some black spots
Body is shiny, gray, and green, has no spots
Body is intact
Tail is gray and blue and has some black spots
Tail is attached to the body
Shell is less tough and less hard
3
5.60
Pearl color, translucent
Translucent, silver-ish or gray-ish
Milky white
Meat
Shell
Meat is translucent and grayish. Meat is less firm
Good
Seashell and fishy smell. Roes are yellow
Head is blueish-gray. Black spots appear on the
swimming legs. Head is intact
Body is shiny, gray, and green. The body has
black spots. Body is intact
Tail is gray and blue, has some black spots. Tail
is attached to the body
Meat is translucent, silver gray. Meat is less firm
Shell is less tough
Milky white, pink, yellow
Hard, elastic
4
8.87
Hard, slight elastic
Slightly soft
Soft
Seashell and fishy smell. Roes are yellow. Head
is gray. Black spots appear on the swimming
legs. Head is loose from the body
Body is gray, and green. The body has black
spots. Body is intact but lightly stretched
Tail is gray and blue, has black spots. Tail is
attached to the body
Head and body are intact. The head is
tightly attached to the body. The tail is 0
attached to the body
5
10.53
Head is loose but body is still intact, and
the tail is attached to the body
1
Texture
Appearance
Meat is milky white and lightly soft
Shell is less tough
Head is loosely attached to body; and
flesh is loosely attached to shell
2
Moderately
acceptable
Head is very loose, may not attached to
the body; flesh is easily separated from 3
shell
Fishy smell. Roes are light orange. Head is
pinkish gray. Black spots on swimming legs
Head is loose from the body
Body is gray; light pink on the back. The body
has black spots. Body is intact but lightly
stretched
Tail is blue and has dark spots. Tail is attached
to the body
Firm, springy, elastic
0
1
2
3
6
14.12
Slightly less firm, less springy
Soft, sticky, slightly elastic
Soft, deformed
Meat
Crispy shell
Meat is silver gray and lightly soft
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to the loose body. The shrimp had a reddish body with a
moderate density of black spots and opaque shell. The meat
was not attached to the skin. It was slightly pink, soft, and
had slightly sour smell, which acquired QI scores of 16.93
and 18.50, respectively. In stage 5 (from day 9 to day 10),
the head was almost detached from the body, the shrimp had
a foul and sour smell, soft meat, a lot of black spots, and no
legs. The QI scores during this stage were 21.37 and 22.77,
respectively. A linear relationship between storage days and
QI score was found by a simple linear regression equation:
QI=2.4×day-0.79 (R²=0.990). The shelf life of Pacific white
shrimp at 0°C was projected to 8 days corresponding to QI
of 18.5. Le, et al. (2017), Okpala, et al. (2014), Nirmal, et al.
(2009), and Hanpongkittikun, et al. (1995) [18, 24, 29, 30]
also obtained a shelf-life for black tiger and white shrimp
ranging between 7 and 8 days. In reference to previously
published studies, we categorize the quality of Pacific white
shrimp into 4 classes: Excellent (QI from 0-2.9), Good (QI
2.9-8.87), Moderately Acceptable (QI 8.87-14.12), and Just
Acceptable (QI 14.12-18.50). The established QIM scheme
was validated by comparison between its projected shelf-
life and the actual shelf-life of the shrimp samples. Ten
shrimp samples with different storage times were randomly
selected and subjected to the QI evaluation. The QI score
for each sample was the average score given by the sensory
panel. The estimated shelf life was calculated using the
linear regression equation (QI=2.41×day-0.79; R²=0.990).
The results in Table 3 show that the actual shelf life was not
significantly different from the estimated shelf life (p<0.05).
Table 3 describes the data from the 10 experimental samples.
Fishy, ammonia smell
Roes are light orange. Head is pinkish gray
Black spots on swimming legs and head. Head is
loose from the body
Body is gray and pink. The body has large black
spots. Body is stretchy
Tail is blue, pink and has dark spots. Tail is
attached to the body
Crispy shell
7
16.93
Meat is milky gray and soft.
Just
acceptable
Fishy, slightly trimethylamine odor
Roes are orange and broken. Head is pinkish
gray. The head has large black spots. Head is
loose from the body
Body is gray and pink. The body has large black
spots. Body is stretchy
Tail is blue, pink at the tip of the tail. Tail is
attached to the body
Crispy shell
8
18.50
Meat is milky gray and soft, not elastic, sticky
Fishy, trimethylamine odor
Head is orange, and black. Large black spots
Head is loose from the body. Roes are broken
Body is yellow, pink. Body has large black spots
Black spots appear on the abdomen. Body is
stretchy
Tail is black. Tail is attached to the body
Soft shell
Meat is milky white, yellow, pink. Meat is sticky
9
21.37
Rejected
Strong trimethylamine smell (rotten smell)
Head is orange, black. Large black spots. Head is
loose from the body. Roes are broken
Body is yellow, pink. Body has large black spots.
Black spots are on the abdomen and legs. Body
is stretchy
Black tail. Tail is attached to the body
Soft shell
Meat is milky white, yellow, pink. Meat is sticky
10
22.77
The changes in the sensory quality of Pacific white
shrimp were divided into five stages corresponding to five
storage periods: from day 1 to day 2; from day 3 to day 4;
from day 5 to day 6; from day 7 to day 8; and from day
9 to day 10. In stage 1 (from day 1 to day 2), the shrimp
underwent a period of stiffness and there were almost no
changes in color, texture, and odor. The QI scores of day
1 to 2 went from 1.32 to 2.9, respectively. In stage 2 (from
day 3 to day 4), the sensory characteristics of the shrimp
were similar to those on days 1 and 2, however, the color of
head and tail began to change and therefore the QI scores
were 5.60 and 8.87, respectively. In stage 3, (from day 5
to day 6), the shrimp shell lost its glossiness and became
slightly opaque. At this point, the shrimp were still quite
fresh, milky white, and slightly soft, but they had lost their
elasticity and had a few black spots on the head and tail.
Thus, the QI scores were between 10.53 and 14.12. In
stage 4 (from day 7 to day 8), the color of the head and tail
changed considerably compared to the initial samples. The
head and tail were slightly black and the head was attached
Table 3. Validation of the QIM scheme with the projected and
the actual shelf life.
Equivalent number projected shelf life Actual
Samples QI
of storage days
in ice
according to QIM shelf life
scheme
(n=3)
1
2
3
4
5
6
7
8
9
10
1.14 0.8
2.82 1.5
7.2
6.5
5.9
5.0
3.5
2.2
6.6
2.3
4.8
3.6
7.07±0.06
6.5±0.10
4.27 2.1
6.43 3.0
10.04 4.5
13.17 5.8
2.58 1.4
12.93 5.7
6.92 3.2
9.80 4.4
5.97±0.12
5.03±0.12
3.57±0.15
2.23±0.15
6.50±0.10
2.23±0.12
4.97±0.15
3.50±0.10
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Table 3 shows that the remaining shelf-life of the
samples were nearly equal to the shelf-life calculated from
the linear regression equation between QI and storage days.
This validated the efficiency of the QIM scheme for Pacific
white shrimp and proved that this scheme can be used to
evaluate the quality and the classification of shrimp quality
as shown in Table 2.
8
7
6
5
4
3
2
1
0
ATP
ADP
AMP
IMP
HxR
Hx
The change in K-value
Days
Shrimp undergo the autolysis process quickly after
harvest. ATP is one of the first metabolites in fisheries after
death. The changes in nucleotide and related compounds are
presented in Fig. 1. From this figure, the changes of ATP,
ADP, AMP, IMP, and inosine became quickly prone due to
the endogenous enzymes possess in fish and shellfish. In
contrast, the transformation from hypoxanthine to uric acid
occurred slowly. Therefore, the amount of hypoxanthine
increasedwiththestoragetime.Fig.1depictstheATPcontent
and its derivatives resulting from the ATP autolytic process.
The ATP components and their derivatives are expressed
in µM/g. The contents of ATP, ADP, AMP, IMP, HxR, and
Hx measured on day 1 were 0.4, 1.07, 7.03, 0.4, 0.44, and
0.59 µM/g, respectively. This proved that the metabolism
from ATP to AMP occurred quickly at the beginning. The
amount of ATP and ADP from the 3rd day onward had very
low values in the remaining days. The amount of AMP
decreased rapidly until day 4 (4.12 µM/g), meanwhile, the
amount of IMP, Hx, and HxR increased gradually to 1.24,
1.09 , and 0.84 µM/g, respectively, on day 4. However, there
were differences in these components in the following days:
the amount of AMP decreased steadily; IMP increased until
day 6 then decreased slightly to day 10; HxR almost did
not change; while Hx increased gradually over the storage
time. Thus, among the components considered, the Hx
value increased linearly with the storage time and the linear
regression equation between Hx and the storage day was
0
1
2
3
4
5
6
7
8
9
10
Fig. 1. Changes in nucleotide content and the composition of
derivatives during 10-day storage. Adenosine triphosphate -
ATP; Adenosine diphosphate - ADT; Adenosine monophosphate
- AmP; Inosine monophosphate - ImP; Xanthine - Hxr;
Hypoxanthine - Hx.
40
K%
35
30
25
20
15
10
5
y=3.05x+1.77
R²=0.992
Days
10 11
0
0
1
2
3
4
5
6
7
8
9
Fig. 2. Changes of K-value during 10-day storage.
Correlation between the quality indices and
classification of shrimp quality
TheresultsshowedthattheQI,K-value,andhypoxanthine
correlated linearly with storage time. Therefore, these
quality indicators correlate linearly with each other. The
linear regression equation between the indicators are as
follows: QI=0.79K-9.49 (R2=0.956); QI=13.54Hx-7.44
(R2=0.979); Hx=0.06K-0.13 (R2=0.950). Table 4 presents
the results of a combined quality classification of Pacific
white shrimp between the QIM and chemical indicators
including K-value and hypoxanthine.
Hx=0.177×day+0.33 (R2
=0.974). The K-value calculated
from the equation increased with time of storage. The linear
regression equation between the K-value and storage day
was K-value=3.05×day+1.8 (R²=0.992) (Fig. 2). Studies
[10-15, 31] also show that the K-value and hypoxanthine
amount increase linearly with storage time. This suggests
that it is possible to use the amount of hypoxanthine to
assess the quality change of Pacific white shrimps preserved
at 0°C using the linear regression procedure between the
K-value and hypoxanthine presented above.
Table 4. Quality classification of Pacific white shrimps based on
QI, K-value, and hypoxanthine.
Quality class
Excellent
Good
QI
K-value
Hypoxanthine (Hx)
0≤QI≤2.9
2.9<QI≤8.87
0≤K≤18.36
0≤Hx≤0.75
18.36<K≤24.30 0.75<Hx≤1.09
Acceptable
8.87<QI≤14.12 24.30<K≤29.34 1.09<Hx≤1.35
Moderately acceptable 14.12<QI≤18.5 29.34<K≤ 34.11 1.35<Hx≤1.72
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[15] Y.R. Huang, M.F.J. Zelaya, C.Y. Shiau (2016), “Changes in biochemical
compositions and quality of white shrimp (Litopenaeus vannamei) during
storage”, Journal of Aquatic Food Product Technology, 25(1), pp.35-45.
Conclusions
A QIM scheme has been developed for Pacific white
shrimp (Litopenaeus vannamei) stored at 0°C. The scheme
employs the descriptive terms for quality changes in sensory
attributes in accordance with the quality requirements
required by QIM (from 0 to 3). The quality of the shrimp
was categorized into four classes, including Excellent,
Good, Acceptable, and Moderately Acceptable, which are
based on the QI score. The QIM scheme for Pacific white
shrimp was validated for its accuracy and efficiency. This
scheme can be combined with the K-value or hypoxanthine
value for the quality assessment of Pacific white shrimp.
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COMPETING INTERESTS
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farmed black tiger shrimp (Penaeus monodon) in supply chain: Organoleptic
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The authors declare that there is no conflict of interest
regarding the publication of this article.
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Vietnam Journal of Science,
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