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Food Processing and Engineering Studies: |
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Boza is determined to behave as a thixotropic fluid in this
study, under the effects of such technological parameters as shear rate,
temperature, shear time and storage time. Chemical composition of boza used in
this work was found to be 0,33 % ash, 16,6 % total sugar, 1,38 % protein and
0,42 % ethanol, where dry matter content for boza was 23,4 %. Besides total
acidity and pH of boza was found to be 0,92 % and 3,8 respectively. Within the
temperature range of 5-30 ?C and shear rate range of 0,13-300 s-1, boza
exhibited thixotropic behavior with a yield stress, which was characterized by
using Tiu and Boger model. The yield stress of boza varied between 11,2 and 33,7
Pa. Equilibrium structural parameters and the rate constant for the decay of the
structural parameter were found to be 0,65 and 0,00697 for the first set of
experiments and 0,72 and 0,00820 for the second, respectively. Behavior index
for boza was determined to be independent from the effects of temperature and
day, resulting in a single mean value of 0,370 where consistency index varied
within the range of 6,9-32,4 Pa.sn. The final equation established, predicted
the viscosity curves of boza under the effects of varying parameters, with an
average error of 10 %, but was not able to represent time dependent rheological
behavior of boza so accurately on the flow curves. Differing results obtained
from the experiments which were carried out with different boza production
parties strengthened the opinion that boza is not produced in a standard
way. |
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Objectives of this research were to (1) obtain edible film that increased shelf
life from plum puree, (2) investigate water vapor permeability, sorption and
moisture diffusion properties of this film and (3) determine the effect of apple
puree and whey protein isolate addition (10, 30 and 50 % of plum puree’s dry
matter) on film properties. For these objectives, plum puree (8,60 % sugar, 18 %
dry matter), apple puree (10,99 % sugar, 24 % dry matter) and whey protein
isolate (WPI) (95 % protein) were used as a material. Effect of WPI and apple
puree addition on properties of films were investigated. Increasing level of
whey protein isolate, water vapor permeability and diffusion coefficient of
films were increased. Moreover, increasing level of whey protein isolate, it is
determined that moisture contents of films due to water activity were decreased.
Addition of apple puree into film formulations was caused increasing water vapor
permeability and diffusion coefficient. |
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In this study the use of Turkish commercial wheat flours for
noodle which is a popular product in Far Eastern countries was studied.
Moisture, ash, protein, falling number, wet and dry gluten, farinograph and
extensograph analysis were carried out on flour samples which were obtained from
seven geographical regions of Turkey. Noodles which were produced in lab
conditions, had similar color, surface appearance, elasticity, smoothess and
taste scores compared to the reference flour. Noodles samples had statistically
significant difference with the reference noodle sample. In terms of cooking
tests, a statistically significant relation was detected between the cooked
weight of noodles and protein content, dry gluten content and farinograph
stability values of flour samples. In terms of color scores, a statistically
significant relation was determined with ash and protein contents of flour
samples. In terms of elasticity, a signifivant relation was determined with ash
content and fainograph development time values of the flour samples. According
to the sensory analysis scores which were carried out by a comparison of the
flour samples to a reference flour, %40 of Type 1 and %30 of Type 2 commercial
Turkish wheat flours could be utilized for the production of dry alkaline
noodles. |
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Partially defatted and ground white and black grape seeds from
Turkey, Adiyaman, Besni Region was compared with wheat, oat and rye bran and soy
and pea fibers with respect to thier physicochemical properties. In this context
density, particle size distribution, water holding capacity and the effects of
pH and ionic materials on water holding capacity, oil holding capacity and
cation exchange capacity was determined for both grape seeds and other
commercial fiber sources. Compositional analysis of grape seed powders was also
done. Partially defatted black and white grape seed powders had in the order of
4.46% and 2.16% fat, 8.42% and 8.8% protein, 8.69% and 8.69% moisture, 2.91% and
3.04% ash, 34.4% and 41.1% nitrogen free extract, 41.17% and 36.21% crude fiber
respectively. Grape seed powders that have particle sizes between 106 – 212 mikronmeter,
had similar water holding capacity with those of wheat, oat and rye bran (3.21 g
water / g sample). Presence of ionic materials and change in pH value was not
made considerable changes in water holding capacities of the samples. Extracted
soy and pea fibers had relatively higher water holding values under all
conditions compare to other samples. Oil holding capacities of the samples was
close to each other (2,94 – 1,95 g oil / g sample). Oil holding capacities of
white and black grape seeds were 2.22 and 2.19 g oil / g sample respectively.
Cation exchange capacities of black and white grape seed powders were very close
to that of wheat bran (1.03 meq / g dry sample). The data obtained from this
research indicated that the grape seed meals obtained after oil extraction could
be a good source of dietary fiber. |
In this study, chemical composition and rheological properties
of tahina were investigated in detail. Rheological measurements on tahina and
tahina oil were conducted between 20°C and 70°C in the shear rate range of
0.13-500 s-1. Also studied was the contribution of solid matter to the overall
rheology of tahina. Moreover, effect of storage time on rheological properties
of tahina was examined. With the exception of salt content, chemical composition
and fatty acids content of tahina were well in agreement with the values given
in the Turkish standards and the literature. For temperature and shear rate
conditions studied in this work, tahina oil behaved like a Newtonian liquid,
whereas tahina itself exhibited a shear-thinning (pseudoplastic) behavior.
Temperature effect on viscosity of tahina and tahina oil was of Arrhenius type
with the activation energies of flow as 20 500 kJ/kg mol and 35 710 kj/kg mol,
respectively. Suspensions of 10, 20 and 30% (w/w) solid matter were prepared by
simply adding tahina oil to tahina. Rheological behavior of the first two
suspensions was characterized as Newtonian, whereas that of the last one was
found to be shear-thinning; similar to normal tahina with 41.30% solid matter.
Solid matter of tahina is shown to have polydisperse particle size.
Viscosity-volume fraction relationships for tahina and the other prepared
suspensions were satisfactorily described by Krieger-Dougherty equation. One of
the parameters of Krieger-Dougherty equation, namely the maximum packing
fraction, was found to vary between 0.4 and 0.5 for tahina. There was no clear
and consistent change in rheology of tahina stored at room temperature. |
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Food Engineering Department,
Istanbul
Technical University, 34469 Maslak - Istanbul, TURKEY
food@itu.edu.tr