Hasan Toğrul

Production of carboxymethyl cellulose from sugar beet pulp cellulose and rheological behaviour of carboxymethyl cellulose

The sugar beet pulp cellulose was converted carboxymethyl cellulose (CMC) by etherification and the process of carboxymethylation was optimised with respect to the solvent medium, alkali concentration, sodium chloroacetate amount, temperature and time of reaction. The optimised product had a DS of 0.6670 and the optimum conditions for carboxymethylation were sodium chloroacetate amount of 3.0 g, an NaOH concentration of 30%, temperature of 70 °C, time of 360 min with isobutyl alcohol as the solvent medium. The flow behaviour of CMC from sugar beet pulp cellulose was determined using a rotational viscometer for concentration range of 10–30 kg/m3, temperature range of 20–30 °C, and shear rate range of 3.24–64.8 s−1. Newtonian, Bingham and power law models were applied to fit the flow behaviour of CMC solutions. The behaviour of CMC solutions was pseudoplastic and the flow behaviour of CMC solutions was found to be most adequately described by the power-law model. Concentration, temperature and shear rate affected the rheological properties. The temperature dependency of the consistency coefficient and the flow behaviour index was modelled using a Turian approach. Both the consistency coefficient and the flow behaviour index were sensitive to changes in temperature and concentration. The consistency coefficient varied between 0.0024 and 0.0162 whereas the flow behaviour index varied between 0.7017 and 0.9590. The flow behaviour index decreased with concentration and increased with temperature, while the opposite trend was observed with the consistency coefficient. The apparent viscosity decreased with increasing temperature and shear rate implying that CMC solutions studied behaved as shear thinning. The experimental data were fitted by mathematical models to allow prediction of the consistency coefficient, the flow behaviour index and the apparent viscosity as a function of temperature and concentration.

Global solar radiation over Turkey: comparison of predicted and measured data

In this study, various regression analyses were applied to estimate monthly mean solar radiation in Turkey, by using n/N and n/Nnh parameters. Also, equations which represent two periods of the year, winter and summer, were developed by using these parameters. The equations developed by using n/Nnh ratio showed good results for the whole country, but, those which included n/N ratio at different cities showed better results. Even better results were obtained when the equations were applied to the summer and winter. In addition to RMSE and MBE statistics, the t-test method and the harmonic analysis were employed to prove that the results are reliable.

Extending shelf-life of peach and pear by using CMC from sugar beet pulp cellulose as a hydrophilic polymer in emulsions

Peach and pear were treated with different compositions of emulsions to extend shelf-life of fruits and to preserve the fruit quality. Paraffin wax, beeswax and soybean oil; carboxymethyl cellulose (CMC) with degree of substitution of 0.6670; Emulgin PE, triethanolamine, oleic acid and sodium oleate were used as hydrophobic phases, hydrophilic polymer and emulsifying agents in the coatings of peach and pear, respectively. The CMC obtained by etherification of the sugar beet pulp cellulose was used as a hydrophilic polymer. To investigate the post-harvest water loss of peach and pear, fruits were observed during storage while being subjected to dehydrating conditions in storage chamber at 25 °C and 75% relative humidity level. The changes in weight, pH, soluble solids, titratable acidity and ascorbic acid of the coated samples with storage time were measured at regular intervals throughout the storage period to evaluate the effect of storage period on fruit quality. The modified drying models describing the storage time dependence of weight loss were fitted to the experimental data and the model parameters in equations were determined by multiple regression analysis. Some of the coatings decreased the soluble solids, titratable acidity and ascorbic acid losses in comparison to the uncoated peaches and pears. The coating of peach and pear surfaces with emulsions containing CMC from sugar beet pulp cellulose as a hydrophilic polymer extended the shelf-lives of peach and pear to 12 and 16 days, respectively. It was found that a combination using beeswax as hydrophobic phase, triethanolamine and oleic acid as emulsifying agent, CMC as hydrophilic polymer and the emulsion containing soybean oil as hydrophobic phase, sodium oleate as emulsifying agent, CMC as hydrophilic polymers were suitable for the coating of peaches and pears, respectively.

Estimation of global solar radiation under clear sky radiation in Turkey

In this study, the usability of clear sky radiation for predicting the average global solar radiation was investigated. For this aim, the various regression analyses were applied by using n/N and n/Nnh parameters. Also, equations which represent the two periods of the year, winter and summer, were developed by using these parameters.

Estimation of monthly global solar radiation from sunshine duration measurement in Elaziğ

In this study, the relation between a and b terms and n/N was investigated to estimate the global solar radiation in Elazig by using different regression analyses. Equations which contain the whole year and two different periods, winter and summer, were developed. Eqs. (5)–(7) which represent second, third and fourth degree equations respectively, gave the best results in all of the equations having an error less than 1%. Contrary to expectations, the equations developed for summer and winter periods had higher errors than the others.

Filtration of pectin extract from grapefruit peel and viscosity of pectin solutions

Abstract The yield of pectin extracted (85 °C, pH = 2.5, 90 min) by acidified water in a ratio of 25 parts per part of dry peel from dried grapefruit peel was 21.1% (DM basis). The pectin extract was vacuum filtered at different temperatures and under various pressure differences, and the average specific cake resistances were determined. The specific cake resistance was highly dependent on the filtration pressure. The cake compressibility coefficients at 15 °C, 25 °C and 35 °C were calculated as 0.387, 0.379 and 0.379, respectively. The filtration rate observed at 15 °C was higher than that at 25 °C due to flocculation at low temperature. The effects of temperature and concentration on the viscosity of pectin solutions were examined at six different temperatures between 10 °C and 60 °C and four concentration levels between 0.3 g/100 ml and 1.4 g/100 ml. The activation energy for viscous flow was in the range 2·10–3·77 kcal mol−1. Finally, the combined effect of temperature and concentration on the viscosity was expressed as η = 8.52 × 10 −5 exp( −1.6162 C + 1.807 exp(0.5493 C) RT )

Determination of Moisture Transport Parameters of Some Fruits Under Open Sun Drying Conditions

In order to determine the behavior of fruits during drying under natural conditions, open sun drying experiments were conducted on apricots, grapes, peaches, figs, and plums. The drying rate curves of these fruit did not contain constant rate period, but showed a falling rate period. In the present work, Biot numbers and the mass transfer characteristics—namely moisture diffusivity and moisture transfer coefficient—of selected fruits were evaluated by drying coefficients (S) and lag factors (G). The experimental results exhibited mass transfer Biot numbers in the range of 0.115–0.158, thus indicating the presence of finite internal and external resistances.