JFS M: Food Microbiology and Safety
Antimicrobial Activity of Catfish Gelatin Coating
Containing Origanum (Thymus capitatus) Oil
against Gram-Negative Pathogenic Bacteria
ABSTRACT: The antimicrobial activity of origanum oil (OG) was determined against Salmonella Typhimurium and
E. coli O157:H7. The efficacy of catfish gelatin coating containing selected concentrations of OG (0.5%, 1.0%, and
2.0%, v/v) was also investigated in catfish flesh irradiated, inoculated with both bacteria, and stored at selected temperatures. The antimicrobial activity of catfish gelatin coating was determined by cell counts during storage at 4 and
10 ◦ C for 12 d. The color properties of catfish flesh coated with catfish gelatin containing OG were also measured. In
the media, the inhibitory effects of OG against S. Typhimurium were greater than the inhibition effects against E. coli
O157:H7, exhibiting complete inhibition against S. Typhimurium at the concentration greater than 0.5% (v/v). The
incorporation of OG into catfish gelatin coating also inhibited both S. Typhimurium and E. coli O157:H7 in catfish
flesh stored at 4 ◦ C. The reduction of S. Typhimurium counts by gelatin coating containing 0%, 0.5%, 1%, 2% (v/v) OG
were 0.58, 0.73, 1.16, and 1.76 log CFU/g, respectively, exhibiting the greatest effect at 2% (v/v) OG (P < 0.05). During storage at 10 ◦ C, the reduction of S. Typhimurium counts by catfish gelatin coatings with 0%, 0.5%, 1%, and 2 %
(v/v) OG were 0.67, 0.91, 1.32, and 2.05 log CFU/g, respectively. The incorporation of OG into catfish gelatin coating
exhibited greater antimicrobial activity against S. Typhimurium than against E. coli O157:H7 at both temperatures.
The lightness and yellowness of catfish flesh was not altered; however, the redness of catfish gelatin was decreased
by catfish gelatin coating containing OG.
Keywords: antimicrobial activity, catfish, coating, gelatin, origanum oil
Introduction
aging (Reddy and others 1997), and use of preservatives (Kim and
Hearnsberger 1994; Williams and others 1995).
As natural resources to replace synthetic preservatives, a broad
range of essential oils extracted from plant sources such as basil,
clove, horseradish, garlic, mustard, oregano, sage, and thyme were
tested (Ismaiel and Pierson 1990; Delaquis and others 1999; Suhr
and Nielsen 2005; Zivanovic and others 2005; Seydim and Sarikus
2006). After testing the antimicrobial activities of essential oils in
laboratory trials, a variety of essential oils were considered for substantial application in the food industry (Kim and others 1995;
Zivanovic and others 2005; Rojas-Grau and others 2007). The application methods for essential oils to food and food products are
broad. In general, essential oils are applied to inhibit bacterial
growth by direct incorporation into foods as an ingredient (Shekarforoush and others 2007; Busatta and others 2008; Solomakos and
others 2008), coating the food surface (Quattara and others 2001),
or fabricating with edible films to wrap foods (Oussalah and others
2006, 2007).
As a multifunctional protein, gelatin has been applied to broad
areas in food, cosmetic, and pharmaceutical industries (Djagny and
others 2001). Gelatins obtained from a wide range of sources were
applied to develop biodegradable and edible films due to the excellent film-forming properties of gelatin. Compared to mammalian
gelatins, fish gelatins possess potential application to unique food
and food products with the issues of transmissible spongiform encephalopathy (TSE) and religious concerns (Gudmundsson 2002;
MS 20080389 Submitted 5/23/2008, Accepted 2/2/2009. Authors are with Haug and others 2004; Muyonga and others 2004; Zhang and others
Dept. of Food and Nutritional Sciences, Campbell Hall, Tuskegee Univ., 2007). With the unique physical and functional properties, catfish
Tuskegee, AL 36088, U.S.A. Direct inquiries to author Oh (E-mail: gelatin extract can be utilized for edible coating and film materials
jhoh@tuskegee.edu).
for food packaging (Yang and others 2007; Zhang and others 2007).
B
iodegradable materials possess potential alternatives to replace synthetic plastics widely used in food packaging industry. Food packaging plays an important role in food and food
products not only to protect the contents from physical damages,
but also to provide effective barriers against moisture, oxygen, light,
and microbial growth. Due to increased consumer demand for natural and safe foods and food products, natural food ingredients
are gaining considerable attention in the market, and the functional properties of natural ingredients are being investigated extensively (Delaquis and others 1999; Ahn and others 2004; Souza
and others 2007). Recently, natural compounds such as essential
oils and herb extracts containing antimicrobial activities are applied to bio-active packaging systems as an alternative to synthetic
antimicrobial agents in packaging films and materials (Suhr and
Nielsen 2005; Zivanovic and others 2005; Seydim and Sarikus 2006).
Seafood products are vulnerable to foodborne pathogenic bacteria such as Listeria, Salmonella, and Escherichia coli (Adesiyun
1993; Embarek 1994). Fresh or frozen channel catfish products can
be contaminated by pathogenic bacteria such as Salmonella, and
coliforms were detected in the various processing steps (Andrews
and others 1977; Suvanich and others 2000). Therefore, extensive
preservation methods were used to process catfish fillets to prevent
bacterial growth or extend shelf life of catfish fillet, including irradiation (Przybylski and others 1989), modified atmosphere pack-
R
Institute of Food Technologists
doi: 10.1111/j.1750-3841.2009.01115.x
C 2009
Further reproduction without permission is prohibited
Vol. 74, Nr. 4, 2009—JOURNAL OF FOOD SCIENCE
M143
M: Food Microbiology
& Safety
B.J. MIN AND J.-H. OH
Catfish gelatin coating with origanum . . .
In addition, the incorporation of natural antimicrobial compounds
into catfish gelatin extract will add functionality to catfish gelatin
coating by improving shelf life of the catfish products. Origanum
oil extracted from the perennial plant (Thymus capitatus) is an essential oil and generally used as flavoring agents similar to other
essential oils (Bounatirou and others 2007). There is limited information available on origanum oil (Thymus capitatus) and antimicrobial activity (Kandil and others 1994). Therefore, the objectives
of this study were (1) to determine the antimicrobial activity of OG
against Gram-negative pathogenic bacteria in culture media and
(2) to investigate the efficacy of OG incorporated into catfish gelatin
for catfish flesh coating to extend the shelf life of catfish during storage at selected temperatures.
Materials and Methods
Materials
M: Food Microbiology
& Safety
Frozen catfish skins for gelatin extract were obtained from the
Harvest Select Inc. plant (Uniontown, Ala., U.S.A.). Frozen skinless
whole catfish fillet was purchased in local groceries and thawed in
a refrigerator for 18 h prior to use. Origanum (Thymus capitatus) oil
(OG) was purchased from Sigma-Aldrich Co. (St. Louis, Mo., U.S.A.).
The other reagents used in the experiments were analytical grade.
Two Gram-negative pathogenic bacteria, Salmonella Typhimurium
ATCC13311 and E. coli O157:H7 204 were used for the antimicrobial
study. S. Typhimurium was provided by James Barbaree and Stuart Price Laboratories at Auburn Univ. (Auburn, Ala., U.S.A.) and E.
coli O157:H7 was provided by the Center for Food Safety at Univ. of
Georgia (Griffin, Ga., U.S.A.).
Antimicrobial activity of origanum
oil in culture media
From the stock culture of S. Typhimurium and E. coli O157:H7,
1 colony of bacteria was transferred to 9.9 mL tryptic soy broth
(TSB) and incubated for 16 to 18 h at 37 ◦ C aerobically. Transferring to a new TSB was repeated using the same procedure. The cultured bacteria in TSB were centrifuged at 3000 × g for 10 min, and
the pellets were diluted with 0.1% peptone solution. From the serial dilution with 0.1% sterile peptone water, bacterial population
in tryptic soy agar (TSA) was counted and the initial population of
bacteria in the peptone solution ranged from 8.0 to 9.0 log CFU/mL.
For the antimicrobial test, the stock solution of OG (2.0%, v/v) with
tween 80 (4.0%, w/v) in sterile distilled water in a 50-mL tube was
prepared by shaking vigorously. Five selected concentrations of OG
ranging from 0.1% to 2.0% (v/v) were diluted from the stock solution. An aliquot of 100 uL OG solutions of selected concentrations
was placed into sterile petri dishes, and mixed with approximately
10 mL molten TSA containing bacteria at the level of 6.0 log
CFU/mL. Therefore, the actual concentration of OG in the media
was approximately 100-fold lower than the indicated concentration. The plates were incubated at 37 ◦ C for 48 h, and the bacterial
colonies were counted after incubation.
Irradiation of catfish flesh
The frozen catfish fillet flesh was thawed in a refrigerator for 18 h,
trimmed, cut into squares (approximately 2.54 × 2.54 cm), vacuum packed in plastic film, and then stored at −70 ◦ C. The average
weight of catfish flesh was 10 g. The frozen catfish flesh was irradiated by exposing to gamma rays from a 60 Co source at the dose of
0.0682 KGy/min for 245 min at Auburn Univ. to achieve complete
inactivation of preexisting microorganisms in the catfish fillet. Sterilization of catfish was confirmed by checking the bacterial growth
in TSA. The irradiated catfish flesh was stored at −70 ◦ C in a deep
freezer until use.
Catfish flesh coating with catfish gelatin
extracts containing origanum oil
The irradiated catfish flesh was thawed at 4 ◦ C for 18 h, and excess water was removed by sterile paper towel before bacterial inoculation. Catfish flesh was submerged into the bacterial solution
containing S. Typhimurium or E. coli O157:H7 for 10 min, and then
dried for 1 h on the sterile screen under the bio hood. Six grams
of catfish gelatin extracts were dissolved in 200 mL distilled water
and boiled. After cooling to approximately 50 ◦ C, 0.5%, 1%, and 2%
(v/v) OG with tween 80 (v/w; 1:2) was incorporated into the catfish gelatin solution to prepare the coating solution. The inoculated
catfish flesh was coated with the catfish gelatin solution containing
OG by dipping the catfish flesh for 10 s. The coated catfish flesh was
dried for 1 h on the sterile screen under the bio hood (Contamination Control Inc., Landale, Pa., U.S.A.).
Bacterial counts during storage
The coated catfish flesh was placed in a sterile sampling bag
(Labplas, Quebec, Canada) and stored at both temperatures of 4
and 10 ◦ C for 12 d. During storage, the bacterial cell counts were
performed with 3-d intervals. Catfish flesh (approximately 10 g) was
mixed with 90 mL of 0.1% sterile peptone water. The mixtures were
blended for 1 min in a Stomacher. Further dilution was done by
0.1% sterile peptone water. Diluted solution was plated in TSA agar
and bacterial numbers were counted after incubation at 37 ◦ C for
48 h. The initial loads of S. Typhimurium and E. coli O157:H7 onto
catfish flesh before gelatin coating were approximately 4.2 and 4 log
CFU/g, respectively.
Color measurement
The colors of catfish flesh before and after coating with catfish
gelatin containing OG were measured using a minolta Chromameter (CR-300, Minolta Co., Osaka, Japan). The CIE (Commission Internationale de l’Eclairage—the Intl. Commission on Illumination)
L∗ , a∗ , b∗ color space values were used to characterize the surface
color.
Statistical analysis
Each experiment was performed 3 times in duplicates. Data were
analyzed using the general linear models procedure in SAS software
program (SAS Inst. Inc., Cary, N.C., U.S.A.). Multiple mean comparExtraction of catfish gelatin
Extraction of catfish gelatin was performed following procedures isons among the log cell counts of uncoated and coated catfish flesh
established in the previous study (Zhang and others 2007). Approx- samples were carried out by Duncan’s multiple range tests at 5%
imately 40 g of cleaned catfish skin were pretreated by soaking in significance level (P < 0.05).
240 mL of 0.09 M acetic acid at 4 ◦ C for 1 h, and washed with 4 ◦ C
distilled water 5 times, followed by soaking in 240 mL of 0.25 M
Results and Discussion
sodium hydroxide at 4 ◦ C for 1 h. The pretreated catfish skins were
placed into a flask with 120 mL distilled water at 50 ◦ C for 3 h in Antimicrobial activity of origanum oil
a water bath for main extraction. The catfish gelatin extracts were
The antimicrobial activity of OG was determined in the culture
filtered through glass wool, and freeze-dried prior to further use.
medium, and the bacterial counts affected by OG with selected
M144
JOURNAL OF FOOD SCIENCE—Vol. 74, Nr. 4, 2009
concentrations from 0% to 2% (v/v) against S. Typhimurium and
E. coli O157:H7 at the level of 6 log CFU/mL are presented in
Table 1. The bacterial counts of both bacteria containing less than
0.5% (v/v) OG exhibited too numerous to count (TNTC), presumably indicating no significant inhibitory effect at the ranges of concentrations. However, OG inhibited the growth of S. Typhimurium
at the concentration of 0.5% (v/v), exhibiting a greater inhibition
than against E. coli O157:H7. OG concentrations greater than 1%
inhibited both bacteria. It was reported that the antibacterial activities of essential oils are dependent on the concentrations. The
antimicrobial activity of thyme oil at the concentrations of 0.3, 0.6,
and 0.9% (v/v) against E. coli O157:H7 in broth systems was greatly
dependent on the concentrations of thyme oil (Solomakos and others 2008). In general, antimicrobial activities of essential oils vary
among various research studies even for the identical essential oils,
because the antibacterial activities of essential oils can be affected
by numerous factors such as region of growth, genotype, harvest
time, drying methods, and so on (Oussalah and others 2007). Therefore, based on the effective concentrations of OG against S. Typhimurium and E. coli O157:H7, 3 concentrations of 0.5%, 1%, and
2.0% (v/v) OG were selected for incorporation into catfish gelatin
coating solution for further study.
Antimicrobial activities of catfish gelatin coating
containing origanum oil against S. Typhimurium
Figure 1 presents the antimicrobial activity of catfish gelatin
coatings containing OG against S. Typhimurium in catfish flesh
during storage at 4 ◦ C. Coating with catfish gelatin containing OG
resulted in significant reduction in cell counts of S. Typhimurium
by approximately 0.5 log CFU/g, compared to uncoated or coated
with catfish gelatin only at initial day (P < 0.05). As the storage
time at 4 ◦ C increased, the cell counts of entire catfish flesh groups
decreased, even in the uncoated catfish flesh. The slight reduction in bacterial growth in uncoated catfish during storage may be
due to the low storage temperature of 4 ◦ C. Oussalah and others
(2006) reported similar trends that the growth of S. Typhimurium
without antimicrobial film treatment decreased in beef muscle,
when stored at 4 ◦ C. Another similar reduction of S. Typhimurium
stored at 4 ◦ C was observed in untreated beef products, when
compared with beef products treated with herb extracts (Cutter
2000).
Catfish flesh coated with gelatin containing OG exhibited greater
inhibition effects against S. Typhimurium than catfish flesh coated
with gelatin only during entire storage time period. The inhibitory
effect of OG against S. Typhimurium was the greatest at 2% (v/v)
concentration of OG (P < 0.05). At the end of storage (day 12), the
cell counts significantly reduced by gelatin coating containing 0%,
0.5%, 1%, and 2% (v/v) OG were 0.58, 0.73, 1.16, and 1.76 log CFU/g,
respectively (P < 0.05).
There is no available research on the antimicrobial activity of
OG extracted from Thymus capitatis applied to seafood to compare.
Coating with thyme oil, a similar type to OG, reduced the growth of
aerobic bacteria and Pseudomonas putida in both irradiated and
unirradiated cooked shrimp (Ouattara and others 2001). The inhibitory effect of coating with thyme oil was dependent on the concentrations of thyme oil, exhibiting the greatest inhibitory effect
from the highest concentration of 1.8%. Zivanovic and others (2005)
also reported that oregano essential oil alone or incorporated into
chitosan films was effective to inhibit Listeria monocytogenes and
E. coli O157:H7, and the inhibitory effects were dependent on the
increased concentrations between 1% and 4% (v/v). The growth
of L. monocytogenes in zero and low-fat hotdogs was reduced by
thyme oil suspension at three concentrations of 1, 5, and 10 mL/L
(Singh and others 2003).
Table 1 --- Bacterial counts of Salmonella Typhimurium and E. coli O157:H7 inhibited by selected concentrations of
origanum oil.
Bacterial count (CFU/mL)
0.0
S. Typhimurium
E. coli O157:H7
Concentration of origanum oil (%)
0.3
0.5
0.1
a
TNTC
TNTC
TNTC
TNTC
< 10 ESPC
TNTC
b
TNTC
TNTC
1.0
2.0
< 10 ESPC
3.9 × 102
< 10 ESPC
1.2 × 102
= too numerous to count.
ESPC = estimated standard plate count based on a plate size of 65 cm2 .
a
TNTC
b
Cell Counts (Log CFU/g)
5
Figure 1 --- Antimicrobial activity of
catfish gelatin coating containing
origanum oil against Salmonella
Typhimurium stored at 4 ◦ C.
(♦) = Uncoated catfish; ( ) = catfish
coated with gelatin only; ( r) =
catfish coated with gelatin
containing 0.5% origanum oil;
( ) = catfish coated with gelatin
containing 1.0% origanum oil; and
() = catfish coated with gelatin
containing 2.0% origanum oil. Bars
represent standard deviation of the
mean.
4
3
2
1
0
0
3
6
9
12
Storage time (days)
Vol. 74, Nr. 4, 2009—JOURNAL OF FOOD SCIENCE
M145
M: Food Microbiology
& Safety
Catfish gelatin coating with origanum . . .
Catfish gelatin coating with origanum . . .
Temperature is one of the critical factors to control microbial
growth during display or storage, and temperature abuse should
be considered to protect food products from the bacterial growth
by initial contamination or postcontamination (Baker and others
1990). The bacterial counts in the catfish flesh samples stored at
10 ◦ C exhibited dramatic increases during storage, as presented
in Figure 2. The growth of S. Typhimurium increased in both uncoated catfish flesh and coated flesh with catfish gelatin only during storage, exhibiting no significant difference (P > 0.05). However,
the incorporation of OG greater than 0.5% (v/v) into catfish gelatin
coatings exhibited significant inhibitory effects against S. Typhimurium from the initial day, similar to the inhibitory effects
from 4 ◦ C storage (P < 0.05). The inhibitory effects of OG with entire concentrations persisted until 9-d storage, exhibiting significant smaller increases in log CFU/g than uncoated catfish flesh
or catfish flesh coated with gelatin only (P < 0.05). However, only
OG with 2% (v/v) maintained the antimicrobial activity against S.
Typhimurium after 9-d storage (P < 0.05). Compared to uncoated
catfish, the bacterial reductions by coating with 0, 0.5, 1, and 2%
(v/v) OG were 0.67, 0.91, 1.32, and 2.05 log CFU/g at the end of
storage 10 ◦ C, respectively. There was also a significant reduction
of S. Typhimurium by coated catfish with 1.5% and 2.0% (v/v) OG
(P < 0.05).
Antimicrobial activities of catfish gelatin coating
containing origanum oil against E. coli O157:H7
The antimicrobial activity of catfish gelatin coating containing
OG against E. coli O157:H7 at 4 ◦ C is presented in Figure 3. Coating with catfish gelatin containing OG inhibited the growth of E.
coli O157:H7 during the entire storage time, compared to uncoated
catfish flesh and catfish flesh coated with gelatin only. Catfish flesh
coated with catfish gelatin only exhibited apparent inhibitory effect; however, the inhibitory effect was not significant. The cell
counts of E. coli O157:H7 at 4 ◦ C including the uncoated catfish
flesh were reduced during storage, exhibiting a similar trend with
S. Typhimurium stored at 4 ◦ C (Figure 1). The growth of E. coli
O157:H7 in vacuum-packaged raw beef without antimicrobials was
reduced at 4 ◦ C during 28-d storage (Mustapha and others 2002).
Cagri and others (2002) also reported a decrease in bacterial counts
of E. coli O157:H7 in sausage without antimicrobial film during
storage at 4 ◦ C. It was speculated that the reduction in bacterial
counts at low-temperature storage might be attributed to the combination effects from low temperature and antimicrobial activity
of OG. At the end of storage time at 4 ◦ C, catfish gelatin coatings,
regardless of the concentrations of OG, significantly reduced the
growth of E. coli O157:H7 by 0.17 to 0.46 log CFU/g (P < 0.05).
The greatest inhibitory effects were obtained in the catfish gelatin
Figure 2 --- Antimicrobial activity of
catfish gelatin coating containing
origanum oil against Salmonella
Typhimurium stored at 10 ◦ C.
(♦) = Uncoated catfish; ( ) = catfish
coated with gelatin only; ( r) =
catfish coated with gelatin containing
0.5% origanum oil; ( ) = catfish
coated with gelatin containing 1.0%
origanum oil; and () = catfish coated
with gelatin containing 2.0%
origanum oil. Bars represent standard
deviation of the mean.
Cell Counts (Log CFU/g)
10
9
8
7
6
5
4
3
0
3
6
9
12
Storage time (days)
5
Cell Counts (Log CFU/g)
M: Food Microbiology
& Safety
11
Figure 3 --- Antimicrobial activity of
catfish gelatin coating containing
origanum oil against E. coli O157:H7
stored at 4 ◦ C. (♦) = Uncoated catfish;
( ) = catfish coated with gelatin only; (
r) = catfish coated with gelatin
containing 0.5% origanum oil;
( ) = catfish coated with gelatin
containing 1.0% origanum oil; and
() = catfish coated with gelatin
containing 2.0% origanum oil. Bars
represent standard deviation of the
mean.
4
3
2
1
0
0
3
6
Storage time (days)
M146
JOURNAL OF FOOD SCIENCE—Vol. 74, Nr. 4, 2009
9
12
Catfish gelatin coating with origanum . . .
Color properties of catfish flesh coated with
catfish gelatin containing origanum oil
The catfish gelatin solution for coating was transparent. The visual appearance of catfish flesh after coating with catfish gelatin solution was glossy. The catfish coating containing OG onto catfish
flesh did not alter the lightness and yellowness of the catfish flesh
(Table 2). However, the redness of catfish flesh was significantly reduced by both catfish gelatin coating and catfish coating containing
OG (P < 0.05).
Conclusions
T
he growth of both S. Typhimurium and E. coli O157:H7 was
inhibited by OG. The antimicrobial activity of OG was greater
against S. Typhimurium than against E. coli O157:H7. The incorporation of OG into catfish gelatin solution for coating catfish
flesh inhibited both bacteria at the temperatures of 4 and 10 ◦ C.
The antimicrobial activity of OG gelatin coatings against S. Typhimurium was greater than the antimicrobial activity against E.
coli O157:H7 at both temperatures. The redness of catfish flesh
coated with catfish gelatin extract containing OG was lower than
redness of uncoated catfish flesh. The results demonstrate the antimicrobial activity of OG against Gram-negative pathogenic bacteria, and suggest that catfish gelatin extract containing OG can be
applied to improve the safety of food products.
11
Figure 4 --- Antimicrobial activity of
catfish gelatin coating containing
origanum oil against E. coli O157:H7
stored at 10 ◦ C. (♦) = Uncoated
catfish; ( ) = catfish coated with
gelatin only; ( r) = catfish coated
with gelatin containing 0.5%
origanum oil; ( ) = catfish coated
with gelatin containing 1.0%
origanum oil; and () = catfish coated
with gelatin containing 2.0%
origanum oil. Bars represent
standard deviation of the mean.
Cell Counts (Log CFU/g)
10
9
8
7
6
5
4
3
0
3
6
9
12
Storage time (days)
Table 2 --- Color properties of catfish flesh coated with catfish gelatin containing selected concentrations of origanum
oil.
L∗
a∗
b∗
Uncoated catfish
Catfish coated with gelatin only
Catfish coated with gelatin + 0.5% OGa
Catfish coated with gelatin + 1.0% OG
Catfish coated with gelatin + 2.0% OG
108.0 ± 2.2A
110.8 ± 3.9A
109.4 ± 3.8A
109.4 ± 3.2A
108.3 ± 2.6A
E. coli O157:H7
4.7 ± 1.1A
1.0 ± 0.3B
−1.7 ± 0.2D
−0.2 ± 0.1C
0.4 ± 0.2BC
14.3 ± 2.1A
15.0 ± 2.7A
13.0 ± 2.5A
13.4 ± 2.6A
13.0 ± 1.5A
Uncoated catfish
Catfish coated with gelatin only
Catfish coated with gelatin + 0.5% OG
Catfish coated with gelatin + 1.0% OG
Catfish coated with gelatin + 2.0% OG
106.4 ± 2.4A
108.5 ± 3.9A
109.0 ± 4.2A
109.8 ± 3.3A
109.4 ± 1.5A
Salmonella Typhimurium
5.5 ± 1.1A
1.5 ± 0.2B
−0.9 ± 0.2C
−0.6 ± 0.2C
−0.6 ± 0.2C
14.5 ± 2.7A
13.0 ± 2.7A
11.8 ± 2.2A
12.4 ± 2.4A
12.4 ± 2.6A
a
OG =
A,B,C,D
origanum oil.
Means within a column with different superscripts are significantly different (P < 0.05).
Vol. 74, Nr. 4, 2009—JOURNAL OF FOOD SCIENCE
M147
M: Food Microbiology
& Safety
coating containing 2.0% (v/v) OG. Busatta and others (2008) reported that there was a significant reduction in E. coli growth in
fresh sausages by the incorporation of marjoram essential oil into
the sausages, and the antimicrobial effects of the marjoram oil were
greatly dependent on the concentration of the oil. However, the authors also reported that E. coli was not completely inhibited even
by the highest concentration of 2.5 times of minimum inhibition
concentration.
During storage at 10 ◦ C, the growth of E. coli O157:H7 in uncoated catfish flesh reached approximately 10 log CFU/g (Figure 4).
The bacterial counts of E. coli O157:H7 in catfish flesh coated with
gelatin containing OG did not significantly reduce the bacterial
counts between 3- and 9-d-storage time periods. However, catfish
gelatin coating containing 2% (v/v) OG exhibited a significant reduction in bacterial counts at 12-d storage (P < 0.05).
The inhibitory effects of OG in catfish flesh were greater against
S. Typhimurium than against E. coli O157:H7 at both temperatures. The essential oils obtained from plants exerted antimicrobial activity tested in broth systems often do not exhibit the similar
antimicrobial effects in the real food products, due to numerous
factors such as food composition, ingredient, storage condition,
and so on. Our results support that the inhibitory effects of OG were
dependent on the concentration, storage temperature, and test
bacteria.
Catfish gelatin coating with origanum . . .
Acknowledgments
The authors would like to thank Dr. Yifen Wang at Auburn Univ.,
Auburn, Ala., U.S.A., for providing catfish skins for this study.
References
M: Food Microbiology
& Safety
Adesiyun AA. 1993. Prevalence of Listeria spp., Campylobacter spp. Salmonella spp.
Yersinia spp. and toxigenic Escherichia coli on meat and seafoods in Trinidad. Food
Microbiol 10:395–403.
Ahn JH, Grun IU, Mustapha A. 2004. Antimicrobial and antioxidant activities of natural extracts in vitro and in ground beef. J Food Prot 67:148–55.
Andrews WH, Wilson CR, Poelma PL, Romero A. 1977. Bacteriological survey of the
channel catfish (Ictalurus punctatus) at the retail level. J Food Sci 42(2):359–63.
Baker DA, Genigeorgis C, Garcia G. 1990. Prevalence of Clostridium botulinum in
seafood and significance of multiple incubation temperatures for determination
of its presence and type in fresh retail fish. J Food Prot 53:668–73.
Bounatirou S, Smiti S, Miguel MG, Faleiro L, Rejeb MN, Neffati M, Costa MM,
Figueiredo AC, Barroso JG, Pedro LG. 2007. Chemical composition, antioxidant and
antibacterial activities of the essential oils isolated from Tunisian Thymus capitatus
hoff. et link. Food Chem 105:146–55.
Busatta C, Vidal RS, Popiolski AS, Mossi AJ, Dariva C, Rodrigues MRA, Corazza FC,
Corazza ML, Oliveira JV, Cansian RL. 2008. Application of Origanum majorana L.
essential oil as an antimicrobial agent in sausage. Food Microbiol 25:207–11.
Cagri A, Ustunol Z, Ryser ET. 2002. Inhibition of three pathogens on bologna and summer sausage using antimicrobial edible films. J Food Sci 67(6):2317–24.
Cutter CN. 2000. Antimicrobial effect of herb extracts against Escherichia coli
O157:H7, Listeria monocytogenes, and Salmonella Typhimurium associated with
beef. J Food Prot 63:601–7.
Delaquis PJ, Ward SM, Holley RA, Cliff MC, Mazza G. 1999. Microbiological, chemical
and sensory properties of pre-cooked roast beef preserved with horseradish essential oil. J Food Sci 64(2):519–24.
Djagny KB, Wang Z, Xu S. 2001. Gelatin: a valuable protein for food and pharmaceutical industries: review. Crit Rev Food Sci Nut 41:481–92.
Embarek PKB. 1994. Presence, detection and growth of Listeria monocytogenes in
seafoods: a review. Int J Food Microbiol 23:17–34.
GudmundssonM. 2002. Rheological properties of fish gelatins. J Food Sci67(6):2172–6.
Haug IJ, Draget KI, Smidsrød O. 2004. Physical and rheological properties of fish
gelatin compared to mammalian gelatin. Food Hydrocolloids 18:203–13.
Ismaiel A, Pierson MD. 1990. Inhibition of growth and germination of C. botulinum
33A, 40B, and 1623E by essential oil of spices. J Food Sci 55(6):1676–8.
Kandil O, Radwan NM, Hassan AB, Amer MM, El-Banna HA, Amer MM. 1994. Extracts
and fractions of Thymus capitatus exhibit antimicrobial activities. J Ethnopharmacol 44:19–24.
Kim CR, Hearnsberger JO. 1994. Gram negative bacteria inhibition by lactic acid culture and food preservatives on catfish fillets during refrigerated storage. J Food Sci
59(3):513–6.
Kim J, Marshall MR, Wei C. 1995. Antimicrobial activity of some essential oils components against five foodborne pathogens. J Agric Food Chem 43:2839–45.
Mustapha A, Ariyapitipun T, Clarke AD. 2002. Survival of Escherichia coli O157:H7 on
vacuum-packaged raw beef treated with polyacetic acid, lactic acid, and nisin. J
Food Sci 67(1):262–7.
Muyonga JH, Cole CGB, Cuodu KG. 2004. Extraction and physico-chemical characterization of nile perch (Lates niloticus) skin and bone gelatin. Food Hydrocol 18:581–
92.
M148
JOURNAL OF FOOD SCIENCE—Vol. 74, Nr. 4, 2009
Oussalah M, Caillet S, Salmieri S, Saucier L, Lacroix M. 2006. Antimicrobial effects
of alginate-based film containing essential oils for the preservation of whole beef
muscle. J Food Prot 69(10):2364–9.
Oussalah M, Caillet S, Salmieri S, Saucier L, Lacroix M. 2007. Antimicrobial effects
of alginate-based films containing essential oils on Listeria monocytogenes and
Salmonella Typhimurium present in bologna and ham. J Food Prot 70(4):901–
8.
Przybylski LA, Finerty MW, Grodner, RM, Gerdes DL. 1989. Extension of shelf-life of
iced fresh channel catfish fillets using modified atmospheric packaging and low
dose irradiation. J Food Sci 54(2):269–73.
Quattara B, Sabato SF, Lacroix M. 2001. Combined effect of antimicrobial coating and
gamma irradiation on shelf life extension of pre-cooked shrimp (Penaeus spp.). Int
J Food Microbiol 68:1–9.
Reddy NR, Roman MG, Villanueva M, Solomon HM, Kautter DA, Rhodehamel
EJ. 1997. Shelf life and Clostridium botulinum toxin development during storage of modified atmosphere-packaged fresh catfish fillets. J Food Sci 62(4):878–
84.
Rojas-Grau MA, Avena-Bustillos RJ, Olsen C, Friedman M, Henika PR, Martin-Belloso
O, Pan Z, Mchugh TH. 2007. Effect of plant essential oil compounds on mechanical
barrier and antimicrobial properties of alginate-apple puree edible films. J Food
Eng 81:634–41.
Seydim AC, Sarikus G. 2006. Antimicrobial activity of whey protein based edible films
incorporated with oregano, rosemary and garlic essential oils. Food Res Int 39:639–
44.
Shekarforoush SS, Nazer AHK, Firouzi R, Rostami M. 2007. Effect of storage temperatures and essential oils of oregano and nutmeg on the growth and survival of Escherichia coli O157:H7 in barbecued chicken used in Iran. Food Control 18:1428–
33.
Singh A, Singh RK, Bhunia AK, Singh N. 2003. Efficacy of plant essential oils as antimicrobial agents against Listeria monocytogenes in hotdogs. Lebensm-Wiss Technol
36:787–94.
Solomakos N, Govaris A, Koidis P, Botsoglou N. 2008. The antimicrobial effect of
thyme essential oil, nisin and their combination against Escherichia coli O157:H7
in minced beef during refrigerated storage. Meat Sci 80:159–66.
Souza EL, Stamford TLM, Lima EO, Trajano VN. 2007. Effectiveness of origanum vulgare L. essential oil to inhibit the growth of food spoiling yeasts. Food Control
18:409–13.
Suhr K, Nielsen PV. 2005. Inhibition of fungal growth on wheat and rye bread by modified atmosphere packaging and active packaging using volatile mustard essential
oil. J Food Sci 70(1):37–44.
Suvanich V, Marshall DL, Jahncke ML. 2000. Microbiological and color quality
changes of channel catfish frame mince during chilled and frozen storage. J Food
Sci 65(1):151–4.
Williams SK, Rodrick GE, West RL. 1995. Sodium lactate affects shelf life and consumer acceptance of fresh catfish (Ictalurus nebulosus, marmoratus) fillets under
simulated retail conditions. J Food Sci 60(3):636–9.
Yang H, Wang Y, Jiang M, Oh, JH, Herring JL, Zhou P. 2007. 2-step optimization of the
extraction and subsequent physical properties of channel catfish (Ictalurus punctatus) skin gelatin. J Food Sci 72(4):C188–95.
Zhang S, Wang Y, Herring JL, Oh JH. 2007. Characterization of edible film fabricated
with channel catfish (lctalurus punctatus) gelatin extract using selected pretreatment methods. J Food Sci 72(9):C498–503.
Zivanovic S, Chi S, Draughon AF. 2005. Antimicrobial activity of chitosan films enriched with essential oils. J Food Sci 70(1):45–50.