Effect of addition of dietary fiber in coating mixtures on a
textural properties and oil uptake in deep fried chicken meat
Sven Karlovi?, Damir Ježek, Branko Tripalo, Mladen Brn?i?, Tomislav Bosiljkov
Faculty of Food Technology and Biotechnology, University of Zagreb
Pierottijeva 6, 10000 Zagreb, Croatia
In this study instrumental analysis of various different coating mixtures for coating of
chicken meat (pectoralis major) was conducted. As dietary fibers, Fibrex (0.5 %, 1.5 % and
2.5 %) and pectin (0.5 %, 1.5 % and 2.5 %) were added in the mixtures. After frying of meat
at 180 oC for 5 minutes, effects of addition of dietary fibers were evaluated. Analysis of oil
uptake and main texture properties of meat (hardness and elasticity) were performed.
Addition of pectin or Fibrex to mixtures shows significant decrease in oil uptake (up to 30
%). Water loss from meat was decreased, and consequently elasticity was much larger for
samples coated with pectin or Fibrex coatings than for sample without dietary fiber
coatings. Hardness of samples decrease up to 38 % with the increase of addition of Fibrex,
and up to 47.5 % for samples coated with coatings which contain pectin. It can be concluded
that the addition of dietary fiber to coating formulations have positive influence on textural
properties of meat, as well as known health benefits.
Keywords: texture analysis, hardness, elasticity, oil uptake, dietary fiber
As one of the basic sensory properties, texture has large influence in determining of quality
of foodstuff (Drewnowski, 1997.). Texture and colour of coating are first things noticed
during observation and chewing of fried chicken meat. From consumer point of view,
sensory properties of foodstuff, as well as nutritive characteristics are main factors in buying
decision. In this light, it is important to maintain consistent textural and other physical as
well as chemical characteristics, while trying to improve the nutritive value of food. This
paper will show if addition of dietary fibres to coating mixtures will fulfil this task and at
the same time lower the energy content of food by decreasing the oil content.
Dietary fibres consist mostly of non-starch polysaccharides such as cellulose and
hemicellulose. Rest of the dietary fibre structure consist of other plant components such as
dextrin. Pectin as one of the most common dietary fibre is linear chain of galacturonic acid
units linked with ?-(1-4) glucosidic bonds. It is usually extracted from citrus fruits. Fibrex is
commercial product made from sugar beet. Hemicellulose and cellulose make 75 % of
Fibrex and the rest of it consist of pectin from citrus. It has very high water holding capacity
and stability on high and low temperatures (frying, freezing, etc.). Fibrex is also gluten free,
so it can be used in broad variety of applications.
Samples coated with mixtures containing dietary fibres should have lesser oil content, which
drastically reduce energy content of food. Dietary fibres also contribute to lipid metabolism,
stool volume and decrease risk of some cancers and cardiovascular diseases (Langkilde et
al, 1993.; Overton et al, 1994.).
Rice starch was used as a substitute for eggs which act as a binding agent. It increase
adhesivity of coatings to meat and consequently increase amount of coating in the final
product after frying. By eliminating eggs from list of ingredients, coatings have better
nutritive characteristics, which include less cholesterol and fat content. At the same time,
safety of food is greater and shelf life is increased.
This work was oriented on determining influence of dietary fibres mixed in coatings on
textural properties of coated chicken meat. Texture analysis was performed and oil content
for 7 different coating mixtures was analyzed.
2. Materials and methods
For the manufacture of coating mixtures, extruded corn flour (Naše klasje d.o.o., Croatia)
and rice starch (Pen-prom d.o.o, Croatia) were used in all mixtures. High ester Grinsted
XSS pectin on the citrus base (Danisco A/S, Denmark) and Fibrex (Danisco A/S, Denmark)
were used as dietary fibres. As a frying medium, palm oil was used (Zvijezda d.o.o.,
Croatia). Meat used for coating was chicken breasts (pectoralis major) (Konzum, Croatia).
Table 1. Ingredients used in preparing of coating mixtures.
C 96.0 4.0
1P 95.5 4.0
2P 94.5 4.0
3P 93.5 4.0
1F 95.5 4.0
2F 94.5 4.0
3F 93.5 4.0
Mixtures were labelled in such way that C is control sample, numbers (1, 2 and 3) represent
number of mixture, P stands for mixtures which contain pectin and F for Fibrex.
All ingredients were homogenised in mixtures using Retsch NM 301 homogenizer.
Weighing of ingredients and mixtures was conducted on Sartorius GP 4102 (Great Britain)
Chicken breasts were sliced on pieces with dimensions of 3 cm x 3 cm and 1 cm of
thickness. Meat was uniformly coated in mixtures and left on room temperature for 30
minutes. Frying was conducted using deep fat fryer (Philips HD 6180) on 180 °C for 5
minutes. After drying and cooling of samples on room temperature, instrumental analysis
was conducted. Oil was changed every 30 minutes, and mass ratio of meat in oil was 100 g
in 3000 g (3167 mL) (Christensen et al, 2000; Bejerholm and Aaslyng, 2003; Saguy and
Instrumental analysis was performed on texture analyzer (Stable Micro Systems,
TA.HDPlus, Great Britain). Data for hardness and elasticity of samples was collected.
Hardness is defined as force needed for penetration in the sample. It is analyzed using the
blade set. Depth of penetration was set at 5 mm (half of sample thickness), penetration
speed was 0.5 mm/s. On obtained graph, hardness was calculated using value of force in the
maximum peak. Elasticity of fried samples was tested using the P/6 probe. Penetration time
was set at 8 s and penetration depth at 10 mm. For elasticity, maximum force applied for
breaking of surface and penetration in sample, as well as depth of penetration before
breaking were measured (Cavitt et al, 2005).
Oil content was measured using Soxhlet method. Samples were weighed, before and after 4
hours of continuous extraction using organic solvent. After drying, weight of flask was
measured. Content of oil was calculated using the equation:
a – mass of empty flask [g]
b – mass of flask with oil [g]
m – mass of sample [g]
For every mixture, 5 samples were prepared and analyzed. Statistical analysis was
conducted and samples coated in dietary fiber were compared to each other and to control
From Figure 1 it can be concluded that increase of the amount of pectin or Fibrex in
mixtures used for coating of samples leads to increase in oil uptake of samples after deep fat
frying. Results show that samples with Fibrex (1F – 3F) absorb smaller quantities of oil than
samples 1P, 2P and 3P which contain pectin. Nevertheless, all samples show lower
absorption of oil than control sample (58.27 %) without any dietary fiber in mixture
composition. It can be concluded that addition of dietary fibres (specifically Fibrex and
pectin) in coating mixtures significantly reduce amount of oil uptake in samples, which is
considerable gain from sensory and health aspects (García et al, 2002.; Abdul-Hamid and
Luan, 2000.). Increase in oil uptake with increase of dietary fibre content can be explained
with physical characteristics of fibres. During the frying process, fibres swell and block oil
from absorbing into meat. At the same time, fibres block water in meat, which contribute to
softness of samples.
Texture analysis data presented in Figure 2 show that hardness rise with increase of pectin
content in samples, with maximum value in sample 3P. This is also evident in samples
coated with mixtures which include Fibrex, where maximum value have sample 3F. All
samples coated with dietary fibres are significantly softer than control sample. The same
mechanism of water retention and uptake of oil is responsible for decrease in hardness.
Increase in fibres content in mixtures leads to increase in oil absorption and at the same time
oil molecules close pores in mixture microstructure. This succesively leads to retention of
water, which evaporates during frying, but in larger part it is unable to cross through the
Figure 1. Oil uptake in samples 1F-3F and 1P-3P.
Figure 2. Hardness of samples.
Figure 3. Elasticity of samples
Despite of the lower oil absorption of Fibrex, in Figure 3 is visible that samples 1F to 3 F
are more elastic than samples 1P to 3P and control sample. This is result of better water
retaining capability of Fibrex, which prevent drying of meat and preserve elasticity.
Generally, all samples which contain dietary fibres have more elasticity than control sample.
Increasing the amount of dietary fibres in coating mixtures lead to increase in elasticity, so
maximum elasticity is reached in sample 3F.
Significantly softer and more elastic samples coated with dietary fibres still satisfy all
sensory demands from consumer point of view. It this view, decrease of oil uptake has
meaningful health and other improvements, without impact on sensory characteristics of
final product. Thus, it can be concluded that the addition of dietary fibre in coating mixtures
is beneficial and desirable.
Hardness gradually drops with increase of Fibrex or pectin in samples.
Fibrex absorbs more oil than pectin and consequently hardness of samples containing Fibrex
is lower than samples with pectin.
Both dietary fibres absorb lower amount of oil than control sample. Water loss is evidently
higher in control sample, so its hardness is highest.
Elasticity is greatest in samples which contain Fibrex and its value increase with increase in
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