Fermentation, drying and different tarhana ingredients
affect the functional properties of tarhana [Bilgiçli
2009, Çelik et al. 2005, Hayta et al. 2002]. Functional
properties of tarhana samples are summarised in Table
2. Proteins in the dispersion resulted in lowering
of the surface tension at the water-air interface, thus
creating FC. Since FS is governed by the ability of
the fi lm formed around the entrapped air bubbles to
remain intact without draining, it follows that stable
foams can only be formed by the highly surface active
solutes [Kaushal et al. 2012]. From this study resulted
that addition of a higher proportion of yoghurt
(sample T3) signifi cantly reduced FC, whereas FS
was increased. Tarhana contains milk proteins, mainly
casein, and wheat proteins (for example glutenin and
gliadins) originating from yoghurt and fl our used in
tarhana preparation [Hayta et al. 2002]. Some food
proteins are capable of forming good foams, and their
capacity to form and keep stable foams depends on
the type of protein, degree of denaturation, pH, temperature
and processing methods [Hayta et al. 2002,
Çelik et al. 2005]. Differences in FC and FS among
the samples may refl ect structural changes of proteins
in tarhana during fermentation and drying [Çelik et
al. 2005]. The decrease in FC of sample T3 can be
explained by the proteolytic activity of present microorganisms,
which lead to the weakness in the gas
absorption property of proteins present in the tarhana
formula [Çelik et al. 2005].
WAC is considered as an important property in
viscous food such as sauces, dough and baked products
[Hayta et al. 2002]. WAC is the ability to hold
water against gravity. WAC comprised bound water,
hydrodynamic water, capillary water and physically
entrapped water [Sridaran et al. 2012]. Control sample
absorbed lowest amount of water (0.65 cm3·g-1) while
samples with changed recipe composition exhibit
signifi cantly different WAC (T2 0.73 cm3·g-1 and T3
0.70 cm3·g-1).
The OAC is an important functional property, as it
helps to improve mouthfeel and retention of fl avour
[Ma et al. 2011]. Samples T1 and T2 had signifi cantly
different OAC (0.79 and 0.78 cm3·g-1) than tarhana T3
(0.71 cm3·g-1). EA is the ability of the molecules to
facilitate solubilization or dispersion of two immiscible
liquids [Kohajdová et al. 2013]. From the measurements
also resulted, that sample T3 (increased proportion
of yoghurt) more signifi cantly lower EA than
other tarhana powder samples. The proteolytic activity
of present microorganisms could be effective in this
decrease of EA [Çelik et al. 2005].
Fermentation process is an important stage for the
development of sensory profi le [Erbaş et al. 2005].
Tarhana soup is made by fermented and dried tarhana
dough, and it has acidic and sour taste with a yeasty
fl avour. The use of yoghurt (source of lactic acid bacteria)
together with yeast plays an important role in
developing distinctive tarhana taste and fl avour [Çelik
et al. 2010].
Sensory parameters of tarhana soup samples are
presented in Table 3. Based on chemical analyses
results (pH, acidity and organic acid content) it was
evaluated and compared sensory parameters of samples
fermented for 72 h and 144 h. Control represent
sample T1 144 h and this sample was compared with
the others. Samples with higher yoghurt proportion
(T3 72 h and 144 h) were presented with signifi cantly
lower values of colour. Odour and consistency evaluation
showed, that studied samples differ signifi cantly
from the control sample. The highest overall acceptability
reached control sample, while all samples fermented
for 72 h showed signifi cantly lower values of
overall acceptability. This could be explained, that 72
h fermentation process is insuffi cient for development
of various aroma and taste compounds.