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Adición de aceite esencial de tomillo y aceite de jojoba para mejorar la calidad de la hamburguesa de vacuno

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Abstract

Los aceites esenciales y sus componentes, son cada vez más populares como agentes antimicrobianos y antioxidantes existentes naturalmente. Por ello, el presente trabajo se centró sobre el efecto de la adición de diferentes concentraciones de aceite esencial (EO) de tomillo (0,02; 0,04; 0,06%) y aceite (O) de jojoba (0,1%) sobre la calidad y estabilidad de hamburguesas de ternera. Los resultados obtenidos indican que la mejor calidad sensorial fue conseguida con la mayor concentración de EO de tomillo (0,06%) mientras que solamente un débil aumento de la calidad sensorial fue registrado en las muestras tratadas con O de jojoba (1%) cuando se compararon con las muestras control. El tiempo de almacenamiento afectó significativamente a los valores de TBA (ácido tiobarbitúrico) mientras que las muestras tratadas con EO de tomillo y O de jojoba, mostraron valores más bajos que los controles. Con referencia a la carga microbiana las muestras tratadas con 0,04 y 0,06% de EO de tomillo, revelaron una reducción significativa con respecto al control en el día 12 de almacenamiento. Por otra parte, los resultados obtenidos ilustran que el O de jojoba no tiene efecto significativo sobre la carga microbiana.
Arch. Zootec. 60 (231): 787-795. 2011.Recibido: 17-12-09. Aceptado: 29-3-10.
IMPROVING THE QUALITY OF BEEF BURGER BY ADDING THYME
ESSENTIAL OIL AND JOJOBA OIL
ADICIÓN DE ACEITE ESENCIAL DE TOMILLO Y ACEITE DE JOJOBA PARA MEJORAR
LA CALIDAD DE LA HAMBURGUESA DE VACUNO
Kassem, G.M.1, Atta-Alla, O.A.1 and Ali, F.H.M.2*
1Department of Food Hygiene. Faculty of Veterinary Medicine Cairo University. Cairo, 12123. Egypt.
2Department of Food Hygiene. Faculty of Veterinary Medicine Beni-Suef University. Beni-Suef 62511.
Egypt. *fatma111969@yahoo.com
ADDITIONAL KEYWORDS
Natural antimicrobials. Natural antioxidants.
PALABRAS CLAVE ADICIONALES
Antimicrobianos naturales. Antioxidantes naturales.
SUMMARY
Essential oils and their components are
becoming increasingly popular as naturally
occurring antimicrobial and antioxidant agents.
Therefore, the present study aimed to investigate
the effect of addition of different concentrations
(0.02, 0.04, 0.06%) of essential oil of thyme (TEO)
and 0.1% oil of jojoba (JO) on the quality and
stability of beef burger. The obtained results
indicated that the best sensory quality was attained
at the highest TEO concentration (0.06%), while
slight improvement in sensory quality was noticed
in samples treated with JO (1%) as compared with
control samples. The storage time significantly
affected the TBA (thiobarbituric acid) values, as
treated samples with TEO and JO showed lower
values of TBA compared with the control samples.
Regarding to microbial load, samples treated with
0.04 and 0.06% of TEO revealed significant
reduction at 12th day of storage as compared with
the control samples. On the other hand, the
obtained results illustrated that JO have no
significant effect on the microbial load.
RESUMEN
Los aceites esenciales y sus componentes,
son cada vez más populares como agentes
antimicrobianos y antioxidantes existentes natu-
ralmente. Por ello, el presente trabajo se centró
sobre el efecto de la adición de diferentes concen-
traciones de aceite esencial (EO) de tomillo (0,02;
0,04; 0,06%) y aceite (O) de jojoba (0,1%) sobre
la calidad y estabilidad de hamburguesas de ter-
nera. Los resultados obtenidos indican que la
mejor calidad sensorial fue conseguida con la
mayor concentración de EO de tomillo (0,06%)
mientras que solamente un débil aumento de la
calidad sensorial fue registrado en las muestras
tratadas con O de jojoba (1%) cuando se compa-
raron con las muestras control. El tiempo de
almacenamiento afectó significativamente a los
valores de TBA (ácido tiobarbitúrico) mientras que
las muestras tratadas con EO de tomillo y O de
jojoba, mostraron valores más bajos que los con-
troles. Con referencia a la carga microbiana las
muestras tratadas con 0,04 y 0,06% de EO de
tomillo, revelaron una reducción significativa con
respecto al control en el día 12 de almacenamiento.
Por otra parte, los resultados obtenidos ilustran
que el O de jojoba no tiene efecto significativo
sobre la carga microbiana.
INTRODUCTION
Modern trends towards production of
pre-cooked, refrigerated ready-to-eat meat
products have made the control of lipid
oxidation increasingly important. Processed
meats which are minced and cooked are
susceptible to accelerate lipid oxidation,
which is one of the main factors responsible
for loss of quality of meat products besides
microbiological deterioration (Rhee, 1989;
Archivos de zootecnia vol. 60, núm. 231, p. 788.
KASSEM, ATTA-ALLA AND ALI
and Singh, 1996). Therefore, much attention
in recent years has been focused on the use
of extracts from herbs and spices to improve
sensory characteristics, retard lipid oxidation
and extend the shelf life of meat products
(Arora and Kaur, 1999; Gulluce et al., 2003
and Lagouri and Nisteropoulou, 2009).
The antimicrobial activity of plant oils
and extracts has formed the bases of many
applications, including processed meat
preservation, pharmaceuticals, alternative
medicine and natural therapies (Akgül and
Kivanç, 1988; Jones, 1996; Reynolds, 1996;
Lis-Ba and Deans, 1997; Elgayyar et al.,
2001; Mejlholm and Dalgaard, 2002; Kalemba
and Kunicka, 2003).
Thyme is traditionally used as flavouring
agents in meat and meat products (Mishra
and Dube 1994; Lawless, 1995). Recently,
its essential oil is known to include carvacol,
borneol, geraniol, but most importantly,
thymol. Thyme essential oil also contains a
variety of flavonoids, including apigenin,
naringenin, luteolin and thymonin (Stahl-
Biskup, 1991; Senatore 1996; Peñalver et al.,
2005). These flavonoids increase thyme
antioxidant capacity (Lacroix et al., 1997).
The volatile oil components of thyme have
also been known to have antimicrobial
activity against different bacteria and fungi
species (Dorman and Deans 2000; Nguefack
et al., 2009). Staphalococcus aureus,
Bacillus subtilis, Escherichia coli and
Shigella sonnei are among bacterial species
against which thyme has been shown to
have antibacterial activity (Kim et al., 1995
and Smith-Palmer et al., 1998). In this regard
Soliman and Badeae (2002) and Kalemba
and Kunicka (2003) found that thyme
essential oil (500 ppm) in vitro possess
strong antimicrobial properties towards food
born bacteria and fungi, including Asper-
gillus flavus, A. parasiticus, A. ochracus
and Fusarium moniliforme. Although
essential oils are well documented in vitro
as natural antimicrobial, some food
components decrease the antimicrobial
effects of the essential oil (Sofos et al.,
1998; Lopez-Malo et al., 2000; Nychas and
Tassou 2000).
Jojoba oil is the liquid wax produced in
the seed of the jojoba (Simmondsia
chinensis) plant. The oil makes up appro-
ximately 50% of the jojoba seed by weight
(Salgm, 2007). It is a straight chain wax ester
of 36 to 46 carbon atoms in length. Each
molecule consists of a fatty acid and a fatty
alcohol joined by an ester bond (Miwa,
1971; Wisniak, 1994; Saguy et al., 1996).
Jojoba oil is not affected by prolonged
storage or changes in temperature when
compared with other vegetable oils, nor
does it facilitate microbial growth (Miwa,
1971 and Wisniak, 1994). Nowadays, there
has been renewed interest in its food
potential as a vegetable and salad oil and
shortening (Kalscheuer et al., 2006).
The questions concerning the safety of
synthetic food additives have encouraged
an increase interest in the use of natural
substances and request more detailed
studies of plant resources and essential oils
(Kalemba and Kunicka, 2003). Therefore,
the objective of this study was to evaluate
the effectiveness of TEO and JO for
controlling sensory, physico-chemical and
microbiological quality of beef burger during
two weeks of refrigeration storage at 5°C.
MATERIALS AND METHODS
EXTRACTION OF TEO
Extraction had been done in the Depart-
ment of Biochemistry, Faculty of Agri-
culture, Cairo University, by hydro-
distillation of dried plant leaves followed by
evaporation under vacuum according to
Cosentino et al. (1999). While JO was
obtained by direct extraction of jojoba seeds
without refining.
BEEF BURGER PRODUCTION
Was carried out in agreement with
Egyptian standard specification for burger
(ESS 1688/1991) as follows: Twenty kilo-
Archivos de zootecnia vol. 60, núm. 231, p. 789.
EFFECTS OF THYME ESSENTIAL OIL AND JOJOBA OIL ON BEEF BURGER QUALITY
grams of freshly beef chuck 24 hours post-
mortem was purchased from local butcher
shop at Giza market-Egypt and directly
transported to the laboratory in an ice box
to be minced in electrical mincer (4 mm).
Minced meat 65%, fat 20%, soybean 5%,
black pepper 0.3%, salt 1.8% and water 10%
were thoroughly mixed for five minutes and
divided into five portions. First portion was
used as control, while the other portions
were either mixed with TEO (0.02, 0.04, 0.06%),
or jojoba oil (0.1%), respectively. The
obtained pastes were formed into 50 g beef
burger using cardboard meat box, packed in
foam plates and stored at refrigerator shelf
at 5ºC. Three samples for each treatment
were examined every three days for two
weeks as follows:
SENSORY QUALITY
Odour, colour and overall acceptability
of raw beef burger samples were assessed
by 5-7 members of Food Hygiene and Con-
trol Department (with past experience in
burger processing and evaluation) to
evaluate their sensory characteristics.
Sensory hedonic scheme, ranged from 0
(very bad) to 8 (very good) following the
procedures of AMSA (1995), was applied.
PHYSICO-CHEMICAL CHARACTERISTICS
Thiobarbituric acid (TBA)-value (mg
malonaldehyde (mal)/kg) was estimated by
distillation technique using 2- thiobarbituric
acid 0.02 M (Sigma Chemical Co. Ltd USA as
described by FAO (1986).
pH determination: 10 g of each sample
were homogenized with 20 ml of distilled
water and pH value was determined using
pH meter (Suntex-T-s-l 9 11005942/ Taiwan)
with calibrated probe type (Ingold 406-M6-
DXk-S7/25), according to Dzudie et al. (2004).
MICROBIOLOGICAL QUALITY
Samples homogenate and serial decimal
dilutions were prepared following the
recommendation of Spencer and De Spencer
(2001). The serial dilutions of each sample
were investigated for count of Entero-
bacteriacae on violet red bile dextrose agar,
Staphylococci on Barid Parker agar, total
mould on Saboureaud dextrose agar,
proteolytic bacteria using 10% skim milk
agar and lipolytic bacteria using tributyrine
agar applying the techniques described by
APHA (1992).
STATISTICAL ANALYSIS
The results are presented as the mean of
three replicates with standard deviation.
The data generated were analyzed by
statistical software package using standard
procedures for analysis of variance and
Duncan multiple range test (Duncan, 1955)
to compare the means and determine the
effect of treatments (SAS, 1995). The
probability value of p0.05 was used as the
criteria for significant differences.
RESULTS AND DISCUSSION
SENSORY EVALUATION
Figure 1 represents odour, colour and
overall acceptability values for all examined
samples for the first three days of storage.
Decline of sensory attributes begin after the
third day of storage with marked reduction
of odour, colour and overall acceptability
values in the control samples at the 6th day
with rejectionable characteristics at the 9th.
While TEO treated samples revealed
acceptability for 12 and 15 days for 0.02%
and 0.04, 0.06% respectively.
It is worth to mention that significant
improvement of odour and overall accep-
tability of investigated samples were
observed at 0 day due to addition of thyme
essential oil, this could be referred to its
aromatic effect (Mishra and Dube, 1994;
Lawless, 1995). Furthermore, highest
concentration (0.06%) TEO treated samples
showed the best sensory quality. On the
other hand, a noticed improvement in
sensory characteristics could be noticed in
samples treated with jojoba oil as compared
with control samples. Addition of TEO and
Archivos de zootecnia vol. 60, núm. 231, p. 790.
KASSEM, ATTA-ALLA AND ALI
TEO (0.04, 0.06%) treated samples with
highest odour, and overall acceptability
value for 0.06% TEO treated samples.
TBA-VALUE
TBA-value is a valuable test in deter-
mination of lipid oxidation (Pikul et al., 1983).
Table I indicates gradual increase of TBA-
values of all examined samples during
storage time. No significant difference
(p0.05) were observed among treated
samples and control at 0 d, which indicates
that oxidative deterioration of beef burger
lipid occurred during storage time.
At the third day of storage significant
reduction (p0.05) of TBA-values of TEO
and JO treated beefburger samples was
obvious. Moreover, an inverse trend was
observed with addition of TEO, where, the
lowest TBA-values were recorded in samples
containing 0.06% followed by 0.04 and
respectively. Such findings may be attri-
buted to the high antioxidant effect of TEO,
which is related to the scavenger nature of
its flavonoids and phenolic content as
apigenin, naringenin, luteolin, thymonin,
carvacrol and thymol (Stahl- Biskup, 1991;
Senatore, 1996; Lacroix et al., 1997; Peñalver
et al., 2005; Skerget et al., 2005; Wojdylo et
al., 2007 and Amarowicz et al., 2009).
Regarding JO treated beef burger, TBA-
values were significantly lower those than
from control samples.These values were
however significantly higher than samples
treated with 0.04 and 0.06% TEO.
In contrast the JO proved weak antio-
xidant effect which is referred to its molecular
stability (Miwa, 1971 and Wisniak, 1994).
It's worth to mention that at the 12th day
of storage both 0.02% TEO and Jojoba oil
treated samples showed TBA-values over
0.5 mg mal/kg which rendered these samples
unacceptable.
PH-VALUE
pH-value of examined samples reveals
that no significant difference (p0.05) could
be established among treated beef burger
0
1
2
3
4
5
6
7
8
Zero 3rd 6th 9th 12th 15th
Control Thy me 0.02 % Thyme 0.04%
Thyme 0.06% Jojoba 0.1%
0
1
2
3
4
5
6
7
8
Zero 3rd 6th 9th 12th 15th
Control Thyme 0.02
%
Thyme 0.04%
Thyme 0.06
%
Jojoba 0.1
%
0
2
4
6
8
Zero 3rd 6th 9th 12th 15th
Control Thyme 0.02
%
Thyme 0.04%
Thyme 0.06
%
Jojoba 0.1
%
colour
overall acceptability
odour
JO to beef burger formulation showed
extension storage time than control samples
by three days for TEO (0.02%) treated
samples and JO (0.1%) and five days for
Figure 1. Changes in burger characteristics
during storage period. (Cambios en las carac-
terísticas de las hamburguesas durante el almace-
namiento).
Archivos de zootecnia vol. 60, núm. 231, p. 791.
EFFECTS OF THYME ESSENTIAL OIL AND JOJOBA OIL ON BEEF BURGER QUALITY
during all storage time. Where pH of con-
trol, 0.02% TEO, 0.04% TEO 0.06% TEO and
JO were 6.53 ± 0.23, 6.38 ± 0.23, 6 .27 ± 0.22,
6.26 ± 0.22 and 6.33 ± 0.22 respectively at 12th
day of storage. Such finding could be
referred to the low quantity of oil added in
the burger formulation and due to buffering
effect of meat (Djenane et al., 2004).
MICROBIOLOGICAL QUALITY
Microbial quality of beef burger was
assessed through estimation of Entero-
bacteriaceae, Staphylococcus, proteolytic,
lipolytic bacterial and total mould counts
(tables II-VI) whereas microbial load could
have been implicated for public hazard.
Enterobacteriaceae, Staphylococcus,
proteolytic, lipolytic bacteria and total mould
counts of control samples were significantly
higher (p0.05) than all treated samples and
continued for the end of the experiment.
Addition of TEO and JO to beef burger
formulation significantly minimized (p0.05)
microbial load of examined samples than
control one. At 0, and 3 d no significant
difference could be established between
treated samples for each examined bacterial
group with expect ion of Staphylococcus
count, where 0.06% TEO treated samples
(2.3±0.083) were significantly lower than JO
Table I. TBA-values in mg malonaldehyde/kg of examined samples. (Valores de TBA en mg de
malonaldehido/kg de muestra analizada).
Period Treatment
(days) Control Thyme 0.02% Thyme 0.04% Thyme 0.06% Jojoba 0.1%
0 0.257 ± 0.009 0.257 ± 0.009 0.257 ± 0.009 0.257 ± 0.009 0.257 ± 0.009
3 0.298 ± 0.011a0.271 ± 0.010b0.264 ± 0.010b0.261 ± 0.009b0.264 ± 0.010b
6 0.495 ± 0.018a0.323 ± 0.012bc 0.302 ± 0.011c0.274 ± 0.010d0.349 ± 0.013b
9 0.712 ± 0.026a0.420 ± 0.015c0.325 ± 0.012d0.318 ± 0.011d0.488 ± 0.018b
12 0.930 ± 0.033a0.511 ± 0.018c0.386 ± 0.014d0.344 ± 0.012e0.553 ± 0.020b
15 1.220 ± 0.044a0.670 ± 0.024b0.422 ± 0.015c0.376 ± 0.014c0.626 ± 0.023b
abIn a row, means with similar letters are not significantly different at p0,05.
Each value represents the mean ± S.D.
Table II. Mean Enterobacteriaceae count log10 cfu /g of examined samples. (Control de
Enterobacteriaceae en log10 de CFU/g de muestra examinada).
Period Treatment
(days) Control Thyme 0.02% Thyme 0.04% Thyme 0.06% Jojoba 0.1%
0 3.00 ± 0.108a2.69 ± 0.097b2.65 ± 0.095b2.65 ± 0.095b2.52 ± 0.091b
3 4.47 ± 0.161a2.65 ± .095bc 2.69 ± 0.097b2.47 ± 0.089c2.65 ± 0.095bc
6 5.77 ± 0.208a3.00 ± 0.108c2.65 ± 0.095d2.48 ± 0.089d3.90 ± 0.140b
9 7.30 ± 0.263a3.90 ± 0.140c3.00 ± 0.108d2.48 ± 0.089e4.30 ± 0.155b
12 8.90 ± 0.320a4.69 ± 0.169c4.30 ± 0.155d3.00 ± 0.108e5.32 ± 0.192b
15 - 6.30 ± 0.227b4.85 ± 0.175c3.30 ± 0.119d7.24 ± 0.282a
abIn a row, means with similar letters are not significantly different at p0.05.
Each value represents the mean ± S.D.
Archivos de zootecnia vol. 60, núm. 231, p. 792.
KASSEM, ATTA-ALLA AND ALI
(2.78±0.1) treated samples (Mohsenzadeh,-
M 2007). After six days of storage, 0.06%
TEO treat beef burger revealed the signifi-
cant lowest count for Enterobacteriaceae,
Staphylococcus, proteolytic, lipolytic bac-
teria and total mould counts followed by
0.04% TEO treated one and continued for
two weeks of refrigerated storage. Mean-
while, microbial load of samples treated with
JO was significantly higher than that of
samples treated with different concentration
of TEO. These results may emphasize the
antimicrobial activity of phenolic com-
pounds in TEO mainly thymol and carvacrol
in (Cosentino et al., 1999; Peñalver et al.,
2005; Šegviæ et al., 2006 and Viuda et al.,
2008).
Considering the antimicrobial effects of
TEO added in burger formulation the data
given in tables (II-VI) indicated that 0.04
and 0.06% concentrations significantly
minimized microbial load than control, 0.02%
thyme and JO treated samples. As 0.04 and
0.06% thyme treated samples revealed 4.6,
4.11, 3.09, 2.22, 2.3 and 5.9, 4.47, 3.39, 3.4 and
3.3 log cfu/g respectively reduction in
counts of Enterobacteriaceae, Staphy-
lococcus, proteolytic, lipolytic bacterial and
Table III. Mean staphylococci count log10 cfu /g of examined samples. (Control de estafilococos
en log10 de CFU/g de muestra examinada).
Period Treatment
(days) Control Thyme 0.02% Thyme 0.04% Thyme 0.06% Jojoba 0.1%
0 2.84 ± 0.102a2.40 ± 0.086bc 2.41 ± 0.087bc 2.30 ± 0.083c2.48 ± 0.089b
3 3.69 ± 0.133a2.48 ± 0.089c2.47 ± 0.089c2.30 ± 0.083c2.78 ± 0.100b
6 4.48 ± 0.161a2.95 ± 0.106c2.60 ± 0.094d2.00 ± 0.072e3.47 ± 0.125b
9 6.30 ± 0.227a3.00 ± 0.108c2.70 ± 0.097d2.30 ± 0.083e3.95 ± 0.142b
12 6.95 ± 0.250a4.30 ± 0.155b2.84 ± 0.102c2.48 ± 0.100d4.47 ± 0.161b
15 - 5.00 ± 0.180c3.48 ± 0.125d3.00 ± 0.108e6.30 ± 0.227b
abIn a row, means with similar letters are not significantly different at p
0.05.
Each value represents the mean ± S.D.
Table IV. Mean proteolytic count log10 cfu /g of examined samples. (Control de proteolíticos
en log10 de CFU/g de muestra examinada).
Period Treatment
(days) Control Thyme 0.02% Thyme 0.04% Thyme 0.06% Jojoba 0.1%
0 3.77 ± 0.136a2.48 ± 0.089b2.48 ± 0.089b2.48 ± 0.089b2.47 ± 0.089b
3 3.77 ± 0.136a2.30 ± 0.083b2.48 ± 0.089b2.30 ± 0.083b2.47 ± 0.089b
6 4.00 ± 0.144a2.69 ± 0.097c2.30 ± 0.083d2.69 ± 0.097c3.60 ± 0.130b
9 4.47 ± 0.161a3.30 ± 0.119c2.80 ± 0.101d2.84 ± 0.102d3.95 ± 0.142b
12 6.39 ± 0.230a4.00 ± 0.144c3.30 ± 0.119d3.00 ± 0.108e4.30 ± 0.155b
15 - 5.30 ± 0.191b3.95 ± 0.142c3.30 ± 0.119d5.60 ± 0.202a
abIn a row, means with similar letters are not significantly different at p
0.05.
Each value represents the mean ± S.D.
Archivos de zootecnia vol. 60, núm. 231, p. 793.
EFFECTS OF THYME ESSENTIAL OIL AND JOJOBA OIL ON BEEF BURGER QUALITY
total mould counts than control samples
respectively at 12th day of storage. These
obtained result confirmed the possibility of
using thyme essential oils in meat products
to prevent the growth of either spoilage
and pathogenic bacteria and extend their
shelf-life.
CONCLUSION
From the obtained results, it could be
concluded that addition of TEO to beef
burger formulation at concentration of 0.04
and 0.06% not only minimize lipid oxidation
but also improved its sensory characteristics
and enhanced the wholesomeness of the
product during two weeks of refrigerated
storage. JO incorporation in beef burger
formulation also showed lower TBA-value
and microbial load than control samples.
Furthermore, during refrigerated storage
shelf life of 0.02% TEO and jojba O treated
samples was extended for three days more
than control. While beef burger treated with
0.04 and 0.06% TEO showed five days more
than Control burger. With superior quality
for TEO 0.06% treated burger at the end of
storage time.
Table V. Mean lipolytic count log10 cfu /g of examined samples. (Control de lipolíticos en log10
de CFU/g de muestra examinada).
Period Treatment
(days) Control Thyme 0.02% Thyme 0.04% Thyme 0.06% Jojoba 0.1%
0 3.00 ± 0.108a2.48 ± 0.089b2.48 ± 0.089b2.48 ± 0.089b2.47 ± 0.089b
3 3.30 ± 0.119a2.48 ± 0.089b2.48 ± 0.089b2.00 ± 0.072c2.47 ± 0.089b
6 3.95 ± 0.142a2.78 ± 0.100c2.30 ± 0.083d2.30 ± 0.083d3.47 ± 0.125b
9 4.00 ± 0.144a3.30 ± 0.119c2.70 ± 0.097d2.30 ± 0.083e3.69 ± 0.133b
12 6.00 ± 0.216a3.95 ± 0.142b3.78 ± 0.136b2.60 ± 0.094c3.69 ± 0.133b
15 - 5.00 ± 0.180a3.78 ± 0.136c3.0 ± 0.108d4.30 ± 0.155b
abIn a row, means with similar letters are not significantly different at p
0.05.
Each value represents the mean ± S.D.
Table VI. Mean total mould count log10 cfu /g of examined samples. (Control de hongos en log10
de CFU/g de muestra examinada).
Period Treatment
(days) Control Thyme 0.02% Thyme 0.04% Thyme 0.06% Jojoba 0.1%
0 2.99 ± 0.108a2.69 ± 0.097b2.70 ± 0.097b2.69 ± 0.097b2.70 ± 0.097b
3 3.95 ± 0.142a2.69 ± 0.097b2.70 ± 0.097b2.48 ± 0.022b2.70 ± 0.097b
6 4.30 ± 0.155a3.30 ± 0.119c2.78 ± 0.100d2.48 ± 0.089e3.90 ± 0.140b
9 5.69 ± 0.205a3.85 ± 0.139c3.95 ± 0.142c2.69 ± 0.097d4.60 ± 0.166b
12 6.60 ± 0.238a5.00 ± 0.180c4.30 ± 0.155d3.30 ± 0.119e6.20 ± 0.223b
15 - 6.60 ± 0.238b4.95 ± 0.178c3.85 ± 0.139d7.30 ± 0.263b
abIn a row, means with similar letters are not significantly different at p
0.05.
Each value represents the mean ± S.D.
Archivos de zootecnia vol. 60, núm. 231, p. 794.
KASSEM, ATTA-ALLA AND ALI
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