Ömer Said Toker - Academia.edu (original) (raw)

Papers by Ömer Said Toker

TURKISH JOURNAL OF AGRICULTURE AND FORESTRY, 2014

In the present study, the effects of 2 different oil types (soybean and olive oil) and 3 differen... more In the present study, the effects of 2 different oil types (soybean and olive oil) and 3 different gums (xanthan gum, sodium alginate, locust bean gum, and their blends) on the rheological and physicochemical properties (pH, titratable acidity, moisture, and color), overrun, melting rate, melting time, and sensory properties of frozen mellorine samples were determined. Apparent viscosity of all mix samples decreased with shear rate, meaning that mellorine mix samples showed shear thinning behavior. Mellorine mix samples showed Ostwald-de Waele flow behavior (R 2 ≥ 0.9915). Viscous synergy indexes were calculated to determine if the gums had synergic interaction. The viscous synergy index value of the xanthan and locust bean gum combination was found to be approximately 1.80, indicating synergic interaction between them. The effects of different gums on the apparent viscosity values at 50 s -1 (η 50 ) were satisfactorily modeled by a modified power-law model. The adaptive neuro-fuzzy inference system (ANFIS) model was also found to be sufficient to predict apparent viscosity values based on the oil type, gum concentrations, and shear rate (R 2 = 0.9121). According to the combined design, the optimum gum concentration was determined to be 56.3% xanthan gum and 43.7% locust bean gum.

Carbohydrate Polymers, 2015

This study aimed to investigate the role of in situ exopolysaccharide (EPS) production by EPS(+)S... more This study aimed to investigate the role of in situ exopolysaccharide (EPS) production by EPS(+)Streptococcus thermophilus strains on physicochemical, rheological, molecular, microstructural and sensory properties of ice cream in order to develop a fermented and consequently functional ice-cream in which no stabilizers would be required in ice-cream production. For this purpose, the effect of EPS producing strains (control, strain 1, strain 2 and mixture) and fermentation conditions (fermentation temperature; 32, 37 and 42°C and time; 2, 3 and 4h) on pH, S. thermophilus count, EPS amount, consistency coefficient (K), and apparent viscosity (η50) were investigated and optimized using single and multiple response optimization tools of response surface methodology. Optimization analyses indicated that functional ice-cream should be fermented with strain 1 or strain mixture at 40-42°C for 4h in order to produce the most viscous ice-cream with maximum EPS content. Optimization analysis results also revealed that strain specific conditions appeared to be more effective factor on in situ EPS production amount, K and η50 parameters than did fermentation temperature and time. The rheological analysis of the ice-cream produced by EPS(+) strains revealed its high viscous and pseudoplastic non-Newtonian fluid behavior, which demonstrates potential of S. thermophilus EPS as thickening and gelling agent in dairy industry. FTIR analysis proved that the EPS in ice-cream corresponded to a typical EPS, as revealed by the presence of carboxyl, hydroxyl and amide groups with additional α-glycosidic linkages. SEM studies demonstrated that it had a web-like compact microstructure with pores in ice-cream, revealing its application possibility in dairy products to improve their rheological properties.

Food and Bioprocess Technology, 2011

... Mahmut Dogan & Omer S. Toker & Tugba Aktar & ... more ... Mahmut Dogan & Omer S. Toker & Tugba Aktar & Meryem Goksel ... In the model, the optimum gum combination was found by simplex centroid mixture design as 59% xanthan gum and 41% locust bean gum, and the highest K value was 33.56 Pa sn. ...

Journal of Cleaner Production, 2015

Cleaning of food fouling deposits in processing equipment is costly and time consuming. Fouling d... more Cleaning of food fouling deposits in processing equipment is costly and time consuming. Fouling deposits form as a result of adhesion of species to the surface and cohesion between elements of the material. Cleaning can result from either or both adhesive and cohesive failure. In this study, the aim was to investigate the removal kinetics of an adhesive material and to design a novel cleaning in place (CIP) protocol for these kinds of materials at industrial scale to reduce environmental impact of cleaning processes. It was detected that different variables controlled the cleaning process in removal of adhesive deposit. Temperature was not found as a significant variable in the initial stage of cleaning. Velocity of cleaning water controlled the cleaning at this stage when top layers of the deposit were removed by fluid mechanical removal due to breakdown of weak cohesive interaction. In the later cleaning stage, both velocity and temperature significantly contributed to cleaning, which suggested that both hydrodynamic forces and rheological changes are needed to overcome adhesion forces between the deposit and surface. Hence, a novel "two step CIP protocol" was proposed due to existence of different mechanisms in cleaning. When compared with conventional one step CIP protocols currently used in the processing plants, the proposed CIP protocol reduced the energy consumption by 40% without decreasing the cleaning efficiency.

LWT - Food Science and Technology, 2015

Food Research International, 2013

Kofter is a traditional product which is composed of water, molasses and starch. The quality of K... more Kofter is a traditional product which is composed of water, molasses and starch. The quality of Kofter depends on many factors involving concentration of the ingredients, starch concentration and type, composition and type of the molasses and drying temperature and time. In the present study, the effect of molasses concentration (75-25%) on the pasting and textural properties of the Kofter samples was investigated. All pasting properties (peak viscosity, trough viscosity, breakdown viscosity, final viscosity, setback viscosity, peak time, pasting temperature) were significantly affected by molasses concentration used in the formula. The increase in water concentration generally caused increase in hardness, adhesiveness, gumminess and chewiness value of the Kofter samples. Sensory analysis was also performed to determine mostly preferred sample regarding appearance, color, texture, taste, odor and overall preference. According to the sensory results, Kofter sample including 40% molasses and 60% water was found to be mostly preferred sample.

Food Chemistry, 2015

The objective of this research was to develop a rapid spectroscopic technique as an alternative m... more The objective of this research was to develop a rapid spectroscopic technique as an alternative method for the differentiation and authentication of gelatin sources in food products by using attenuated total reflectance Fourier transform infrared (ATR-FTIR) spectra combined with chemometrics. Clear discrimination and classification of all the studied gelatin sources (bovine, porcine, and fish) were achieved by hierarchical cluster and principle component analysis (PCA). Amide-I (1700-1600cm(-1)) and Amide-II (1565-1520cm(-1)) spectral bands were used in a chemometric method. Moreover, ATR-FTIR spectral data successfully discriminated pure bovine gelatin from mixture of bovine and porcine gelatins, which is very important for the food industry. The method that we adopted could be beneficial for rapid, simple and economic determination of both gelatin presence and its origin from food products such as yogurt, ice cream, milk dessert or other gelatin containing products such as pharmaceuticals and cosmetics.

Food Research International, 2015

Innovative Food Science & Emerging Technologies, 2014

European Food Research and Technology, 2013

In this study, the effect of starch concentration (5, 7.5 and 10 %) and temperature (60, 70 and 8... more In this study, the effect of starch concentration (5, 7.5 and 10 %) and temperature (60, 70 and 80°C) on the creep and recovery behaviour of grape molasses was investigated. Adaptive neuro-fuzzy inference system (ANFIS) and artificial neural network (ANN) models were established for the prediction of the compliance values (J(t)) based on temperature, starch concentration and time of the creep or recovery phases. The root mean square error, mean absolute error and R 2 values were used for the comparison of the models which showed that the ANFIS model performed better than the ANN model for the desired purpose. The Burger model fitted the J(t) versus time data with R 2 values ranging from 0.987 to 0.999. Response surface methodology (RSM) was performed to investigate the dependency of the creep (G 0 , G 1 , n 0 and n 1 ) and recovery (J KV , B, C, J max , J ? and % recovery) parameters to temperature and starch concentration. As a result of this study, it was observed that deformation of the grape molasses samples increased with decrease in starch concentration and increase in temperature. The gel strength (S) values of the samples were also calculated and modelled by RSM. As increase in starch concentration caused an increase in S value, there was an inverse proportion between the temperature and S value.

Food and Bioprocess Technology, 2011

Steady and dynamic shear properties of grape molasses having varying levels of starch (5%, 7.5%, ... more Steady and dynamic shear properties of grape molasses having varying levels of starch (5%, 7.5%, and 10%) have been determined at 60°C, 70°C, and 80°C. The consistency coefficient (K) and apparent viscosity (η 50 ) increased with the starch concentration and decreased with temperature. Similar behavior was also observed in storage modulus (G′), loss modulus (G″), complex modulus (G*), and complex viscosity (η*). The 5-hydroxymethylfurfural (HMF) content of mid-product mix decreased with the increase in the starch concentration. Hardness, gumminess, and chewiness values increased with the starch concentration and temperature. The HMF content of the final product increased with the increase in drying temperature and decreased as the starch concentration increased.

Food and Bioprocess Technology, 2012

The selection of optimum aroma among vanilla, strawberry and cacao for prebiotic pudding was aime... more The selection of optimum aroma among vanilla, strawberry and cacao for prebiotic pudding was aimed based on sensory analyses by performing multi-criteria decision techniques [analytic hierarchy process (AHP), simple additive weighting (SAW), technique for order preference by similarity to ideal solution (TOPSIS) and elimination et choix traduisant la realite-elimination and choice translating reality (ELECTRE)]. In the first part of the study, the physicochemical (pH, viscosity, dry matter and ash content) and functional properties (bulk density, water-holding capacity and oil-holding capacity) of the dietary fibres (lemon, inulin, apple and wheat) were determined. According to our results, there are significant differences between the fibres (P<0.05). In the second part of the study, the INU/OLI dietary fibre was added to the different flavoured pudding samples (cacao, strawberry and vanilla). Some of their physicochemical (bulk density, dry matter and viscosity) and sensorial properties (appearance, consistency of appearance, consistency in the mouth, taste and smell, adhesiveness and general acceptability) were identified. In the last part of the study, multi-criteria decision techniques (AHP, SAW, ELECTRE and TOPSIS) were applied to obtain the ranking of the pudding samples based on the sensorial scores. According to the results of this study, strawberry-flavoured pudding (not including fibre) was mostly preferred. By considering the ranking of the puddings, it was seen that strawberry flavour was the most appropriate for prebiotic pudding. As a result of this study, it was found that multicriteria decision techniques may be performed to sensorial scores in the food industry to reduce many results to one result thus facilitating the comparison of samples and the explication of results obtained from sensory analysis.

International Journal of Food Engineering, 2015

ABSTRACT

Industrial Crops and Products, 2013

In this study, the effect of different storage temperatures (25, 35 and 45 • C) and storage times... more In this study, the effect of different storage temperatures (25, 35 and 45 • C) and storage times (0, 45 and 90 days) on physicochemical properties (color values, pH, and brix) and HMF (5-hydroxymethylfurfural) contents of grape, mulberry, black mulberry and carob molasses samples was studied. A two factorthree level composite face center design was performed to model and study effects of these factors on the HMF contents of these samples. As a result, storage temperature and time values were found to remarkably change the physicochemical properties and HMF contents. HMF content of the molasses samples increased with temperature and storage time. The highest HMF levels were generally observed in mulberry and black mulberry molasses. The best fitting second order polynomial models were developed using multiple linear regression analysis with backward elimination regression (BER) procedure to remove insignificant factors and interactions from the models. R 2 values of the established models were higher than 0.844, indicating that models were adequate to predict HMF content.

Industrial Crops and Products, 2013

In this study, physicochemical, microbiological and bioactive properties, major sugar and aroma p... more In this study, physicochemical, microbiological and bioactive properties, major sugar and aroma profiles of total 20 artisanal (n = 10) and retail (n = 10) honey samples harvested in Turkey were determined. Physicochemical analyses showed that all honey samples were fresh and with good properties. In terms of sanitary conditions, all honey samples were considered as microbiologically safe. Total aerobic mesophilic and spore forming bacteria were detected in low counts while yeasts and molds were found in 15% and 20% of the honey samples, respectively. One retail honey sample did not meet the Codex Alimentarius standards in terms of its total glucose and fructose content while 75% of the honeys (60% and 90% of artisanal and retail honeys, respectively) had sucrose levels over the allowed limits (5%). There was a positive relationship between total phenolic content and DPPH scavenging activity of the honey samples. However, their antioxidant capacities were variable. Total 88 aroma compounds were detected by Gas Chromatography-Mass Spectrometry (GC-MS) analysis of the honeys. This study showed that there were not very sharp discriminations between retail and artisanal honeys when considering many of the parameters analyzed. Overall, it was confirmed that the quality of the analyzed honeys was good, which facilitates its national and international commercialization.

TURKISH JOURNAL OF AGRICULTURE AND FORESTRY, 2014

In the present study, response surface methodology was conducted for the determination of effects... more In the present study, response surface methodology was conducted for the determination of effects of some phenolics (gallic acid, ellagic acid, and quercetin) on some stability parameters of mixed oil prepared with sunflower and hazelnut oils (50:50, v/v). In this respect, peroxide value (PV), free fatty acids (FFAs), p-anisidine value, induction period, and refractive index of mixed oil were investigated. Predictive regression equations were constructed for the estimation of each studied parameter (R 2 > 0.861). The storage period caused a significant increase in the peroxide value, FFAs, p-anisidine, and refractive index values of the mixed oil, while it decreased the induction period value of oil (P < 0.01). The addition of gallic acid significantly retarded oxidation (P < 0.05), and in general gallic acid and quercetin were found to be effective for preserving oil against oxidation.

Food and Bioprocess Technology, 2012

In this study, effect of processing temperature (5, 15, 25, and 35°C) on the steady, dynamic, and... more In this study, effect of processing temperature (5, 15, 25, and 35°C) on the steady, dynamic, and creep recovery rheological properties of the ice cream mix (ICM) was investigated. It was found that processing temperature significantly affected all rheological parameters of the ICM sample. The flow behavior of the ICM sample was fitted to the Ostwald de Waele model. The magnitude of storage modulus (G′) was higher than that of loss modulus (G″) indicating that ICM sample had weak gel-like structure. Modified Cox-Merz rules were satisfactorily applied to the ICM sample to observe relationship between steady and dynamic shear properties. Additionally, Burger model was used to characterize the viscoelastic properties of the ICM sample. The gel strength (S) value was also calculated, and a decrease was observed with the increase of temperature. Arrhenius equation satisfactorily described the temperature dependency of the rheological parameters such as apparent viscosity at 50 s −1 (η 50 ), consistency coefficient (K), the instantaneous shear modulus of the Maxwell unit (G 0 ), permanent deformation (J ∞ ), and S values that may be predicted by using established equations depending on the temperature. The increase in processing temperature caused a decrease in resistance of the mixture subjected to the deformation, which is very important for production of high quality ice cream.

European Food Research and Technology, 2014

the ingredients simultaneously based on the requirements. The gum combination including 59.5 % ca... more the ingredients simultaneously based on the requirements. The gum combination including 59.5 % carrageenan and 40.5 % guar gum or 52.7 % carrageenan, 33.8 % guar gum and 13.5 % xanthan gum was determined to be the optimum in terms of quality of the product.

International Journal of Food Properties, 2015

Physicochemical (pH, brix, and color), sensory (color, taste, odor, mouthfeeling, consistency, bi... more Physicochemical (pH, brix, and color), sensory (color, taste, odor, mouthfeeling, consistency, bitter flavor, and general acceptability), and rheological properties of the hot chocolate beverages including different cocoa combinations were investigated in the present study. Cocoa type significantly affected all of the properties. Simple additive weighting approach was applied to obtain one score from seven different sensory parameters and simple additive weighting score was used in mixture design to determine optimum cocoa type or cocoa combination. Ostwald de Waele model described the flow behavior of the hot chocolate beverage samples with R 2 values ranged between 0.818 and 0.999. The consistency coefficient (K) and apparent viscosity at shear rate 50 s −1 (η 50 ) were significantly affected by cocoa type found in the formulation of the beverage. The mixture design approach was performed in order to determine variation of the responses (physicochemical, sensory, and rheological parameters) as a function of cocoa concentration. Simple additive weighting scores were satisfactorily described by established equation as a function of cocoa concentration to be used in the formulation of the hot chocolate beverage (R 2 = 0.8645).

International Journal of Food Properties, 2015

Principal component analysis and hierarchical cluster analysis were applied to investigate physic... more Principal component analysis and hierarchical cluster analysis were applied to investigate physicochemical and instrumental textural properties of fresh kashar cheese. Four different principal components sufficiently explained the variability in the cheese samples. In addition, hierarchical cluster analysis was performed to group the kashar cheese samples regarding physicochemical and instrumental textural properties. Instrumental textural properties indicated greater variability than chemical composition of cheese samples. Principal component analysis revealed that color parameters were positively correlated with textural and chemical parameters. The results of this study revealed that other parameters rather than chemical composition would be effective on the instrumental textural properties. It was proved that principal component analysis was a very effective statistical tool to determine quality of cheese samples. According to the principal component analysis and hierarchical cluster analysis results, the attributes defining the kashar cheese samples were determined to be primarily the texture profile analysis parameters.

TURKISH JOURNAL OF AGRICULTURE AND FORESTRY, 2014

In the present study, the effects of 2 different oil types (soybean and olive oil) and 3 differen... more In the present study, the effects of 2 different oil types (soybean and olive oil) and 3 different gums (xanthan gum, sodium alginate, locust bean gum, and their blends) on the rheological and physicochemical properties (pH, titratable acidity, moisture, and color), overrun, melting rate, melting time, and sensory properties of frozen mellorine samples were determined. Apparent viscosity of all mix samples decreased with shear rate, meaning that mellorine mix samples showed shear thinning behavior. Mellorine mix samples showed Ostwald-de Waele flow behavior (R 2 ≥ 0.9915). Viscous synergy indexes were calculated to determine if the gums had synergic interaction. The viscous synergy index value of the xanthan and locust bean gum combination was found to be approximately 1.80, indicating synergic interaction between them. The effects of different gums on the apparent viscosity values at 50 s -1 (η 50 ) were satisfactorily modeled by a modified power-law model. The adaptive neuro-fuzzy inference system (ANFIS) model was also found to be sufficient to predict apparent viscosity values based on the oil type, gum concentrations, and shear rate (R 2 = 0.9121). According to the combined design, the optimum gum concentration was determined to be 56.3% xanthan gum and 43.7% locust bean gum.

Carbohydrate Polymers, 2015

This study aimed to investigate the role of in situ exopolysaccharide (EPS) production by EPS(+)S... more This study aimed to investigate the role of in situ exopolysaccharide (EPS) production by EPS(+)Streptococcus thermophilus strains on physicochemical, rheological, molecular, microstructural and sensory properties of ice cream in order to develop a fermented and consequently functional ice-cream in which no stabilizers would be required in ice-cream production. For this purpose, the effect of EPS producing strains (control, strain 1, strain 2 and mixture) and fermentation conditions (fermentation temperature; 32, 37 and 42°C and time; 2, 3 and 4h) on pH, S. thermophilus count, EPS amount, consistency coefficient (K), and apparent viscosity (η50) were investigated and optimized using single and multiple response optimization tools of response surface methodology. Optimization analyses indicated that functional ice-cream should be fermented with strain 1 or strain mixture at 40-42°C for 4h in order to produce the most viscous ice-cream with maximum EPS content. Optimization analysis results also revealed that strain specific conditions appeared to be more effective factor on in situ EPS production amount, K and η50 parameters than did fermentation temperature and time. The rheological analysis of the ice-cream produced by EPS(+) strains revealed its high viscous and pseudoplastic non-Newtonian fluid behavior, which demonstrates potential of S. thermophilus EPS as thickening and gelling agent in dairy industry. FTIR analysis proved that the EPS in ice-cream corresponded to a typical EPS, as revealed by the presence of carboxyl, hydroxyl and amide groups with additional α-glycosidic linkages. SEM studies demonstrated that it had a web-like compact microstructure with pores in ice-cream, revealing its application possibility in dairy products to improve their rheological properties.

Food and Bioprocess Technology, 2011

... Mahmut Dogan &amp;amp;amp; Omer S. Toker &amp;amp;amp; Tugba Aktar &amp;amp;amp; ... more ... Mahmut Dogan &amp;amp;amp; Omer S. Toker &amp;amp;amp; Tugba Aktar &amp;amp;amp; Meryem Goksel ... In the model, the optimum gum combination was found by simplex centroid mixture design as 59% xanthan gum and 41% locust bean gum, and the highest K value was 33.56 Pa sn. ...

Journal of Cleaner Production, 2015

Cleaning of food fouling deposits in processing equipment is costly and time consuming. Fouling d... more Cleaning of food fouling deposits in processing equipment is costly and time consuming. Fouling deposits form as a result of adhesion of species to the surface and cohesion between elements of the material. Cleaning can result from either or both adhesive and cohesive failure. In this study, the aim was to investigate the removal kinetics of an adhesive material and to design a novel cleaning in place (CIP) protocol for these kinds of materials at industrial scale to reduce environmental impact of cleaning processes. It was detected that different variables controlled the cleaning process in removal of adhesive deposit. Temperature was not found as a significant variable in the initial stage of cleaning. Velocity of cleaning water controlled the cleaning at this stage when top layers of the deposit were removed by fluid mechanical removal due to breakdown of weak cohesive interaction. In the later cleaning stage, both velocity and temperature significantly contributed to cleaning, which suggested that both hydrodynamic forces and rheological changes are needed to overcome adhesion forces between the deposit and surface. Hence, a novel "two step CIP protocol" was proposed due to existence of different mechanisms in cleaning. When compared with conventional one step CIP protocols currently used in the processing plants, the proposed CIP protocol reduced the energy consumption by 40% without decreasing the cleaning efficiency.

LWT - Food Science and Technology, 2015

Food Research International, 2013

Kofter is a traditional product which is composed of water, molasses and starch. The quality of K... more Kofter is a traditional product which is composed of water, molasses and starch. The quality of Kofter depends on many factors involving concentration of the ingredients, starch concentration and type, composition and type of the molasses and drying temperature and time. In the present study, the effect of molasses concentration (75-25%) on the pasting and textural properties of the Kofter samples was investigated. All pasting properties (peak viscosity, trough viscosity, breakdown viscosity, final viscosity, setback viscosity, peak time, pasting temperature) were significantly affected by molasses concentration used in the formula. The increase in water concentration generally caused increase in hardness, adhesiveness, gumminess and chewiness value of the Kofter samples. Sensory analysis was also performed to determine mostly preferred sample regarding appearance, color, texture, taste, odor and overall preference. According to the sensory results, Kofter sample including 40% molasses and 60% water was found to be mostly preferred sample.

Food Chemistry, 2015

The objective of this research was to develop a rapid spectroscopic technique as an alternative m... more The objective of this research was to develop a rapid spectroscopic technique as an alternative method for the differentiation and authentication of gelatin sources in food products by using attenuated total reflectance Fourier transform infrared (ATR-FTIR) spectra combined with chemometrics. Clear discrimination and classification of all the studied gelatin sources (bovine, porcine, and fish) were achieved by hierarchical cluster and principle component analysis (PCA). Amide-I (1700-1600cm(-1)) and Amide-II (1565-1520cm(-1)) spectral bands were used in a chemometric method. Moreover, ATR-FTIR spectral data successfully discriminated pure bovine gelatin from mixture of bovine and porcine gelatins, which is very important for the food industry. The method that we adopted could be beneficial for rapid, simple and economic determination of both gelatin presence and its origin from food products such as yogurt, ice cream, milk dessert or other gelatin containing products such as pharmaceuticals and cosmetics.

Food Research International, 2015

Innovative Food Science & Emerging Technologies, 2014

European Food Research and Technology, 2013

In this study, the effect of starch concentration (5, 7.5 and 10 %) and temperature (60, 70 and 8... more In this study, the effect of starch concentration (5, 7.5 and 10 %) and temperature (60, 70 and 80°C) on the creep and recovery behaviour of grape molasses was investigated. Adaptive neuro-fuzzy inference system (ANFIS) and artificial neural network (ANN) models were established for the prediction of the compliance values (J(t)) based on temperature, starch concentration and time of the creep or recovery phases. The root mean square error, mean absolute error and R 2 values were used for the comparison of the models which showed that the ANFIS model performed better than the ANN model for the desired purpose. The Burger model fitted the J(t) versus time data with R 2 values ranging from 0.987 to 0.999. Response surface methodology (RSM) was performed to investigate the dependency of the creep (G 0 , G 1 , n 0 and n 1 ) and recovery (J KV , B, C, J max , J ? and % recovery) parameters to temperature and starch concentration. As a result of this study, it was observed that deformation of the grape molasses samples increased with decrease in starch concentration and increase in temperature. The gel strength (S) values of the samples were also calculated and modelled by RSM. As increase in starch concentration caused an increase in S value, there was an inverse proportion between the temperature and S value.

Food and Bioprocess Technology, 2011

Steady and dynamic shear properties of grape molasses having varying levels of starch (5%, 7.5%, ... more Steady and dynamic shear properties of grape molasses having varying levels of starch (5%, 7.5%, and 10%) have been determined at 60°C, 70°C, and 80°C. The consistency coefficient (K) and apparent viscosity (η 50 ) increased with the starch concentration and decreased with temperature. Similar behavior was also observed in storage modulus (G′), loss modulus (G″), complex modulus (G*), and complex viscosity (η*). The 5-hydroxymethylfurfural (HMF) content of mid-product mix decreased with the increase in the starch concentration. Hardness, gumminess, and chewiness values increased with the starch concentration and temperature. The HMF content of the final product increased with the increase in drying temperature and decreased as the starch concentration increased.

Food and Bioprocess Technology, 2012

The selection of optimum aroma among vanilla, strawberry and cacao for prebiotic pudding was aime... more The selection of optimum aroma among vanilla, strawberry and cacao for prebiotic pudding was aimed based on sensory analyses by performing multi-criteria decision techniques [analytic hierarchy process (AHP), simple additive weighting (SAW), technique for order preference by similarity to ideal solution (TOPSIS) and elimination et choix traduisant la realite-elimination and choice translating reality (ELECTRE)]. In the first part of the study, the physicochemical (pH, viscosity, dry matter and ash content) and functional properties (bulk density, water-holding capacity and oil-holding capacity) of the dietary fibres (lemon, inulin, apple and wheat) were determined. According to our results, there are significant differences between the fibres (P<0.05). In the second part of the study, the INU/OLI dietary fibre was added to the different flavoured pudding samples (cacao, strawberry and vanilla). Some of their physicochemical (bulk density, dry matter and viscosity) and sensorial properties (appearance, consistency of appearance, consistency in the mouth, taste and smell, adhesiveness and general acceptability) were identified. In the last part of the study, multi-criteria decision techniques (AHP, SAW, ELECTRE and TOPSIS) were applied to obtain the ranking of the pudding samples based on the sensorial scores. According to the results of this study, strawberry-flavoured pudding (not including fibre) was mostly preferred. By considering the ranking of the puddings, it was seen that strawberry flavour was the most appropriate for prebiotic pudding. As a result of this study, it was found that multicriteria decision techniques may be performed to sensorial scores in the food industry to reduce many results to one result thus facilitating the comparison of samples and the explication of results obtained from sensory analysis.

International Journal of Food Engineering, 2015

ABSTRACT

Industrial Crops and Products, 2013

In this study, the effect of different storage temperatures (25, 35 and 45 • C) and storage times... more In this study, the effect of different storage temperatures (25, 35 and 45 • C) and storage times (0, 45 and 90 days) on physicochemical properties (color values, pH, and brix) and HMF (5-hydroxymethylfurfural) contents of grape, mulberry, black mulberry and carob molasses samples was studied. A two factorthree level composite face center design was performed to model and study effects of these factors on the HMF contents of these samples. As a result, storage temperature and time values were found to remarkably change the physicochemical properties and HMF contents. HMF content of the molasses samples increased with temperature and storage time. The highest HMF levels were generally observed in mulberry and black mulberry molasses. The best fitting second order polynomial models were developed using multiple linear regression analysis with backward elimination regression (BER) procedure to remove insignificant factors and interactions from the models. R 2 values of the established models were higher than 0.844, indicating that models were adequate to predict HMF content.

Industrial Crops and Products, 2013

In this study, physicochemical, microbiological and bioactive properties, major sugar and aroma p... more In this study, physicochemical, microbiological and bioactive properties, major sugar and aroma profiles of total 20 artisanal (n = 10) and retail (n = 10) honey samples harvested in Turkey were determined. Physicochemical analyses showed that all honey samples were fresh and with good properties. In terms of sanitary conditions, all honey samples were considered as microbiologically safe. Total aerobic mesophilic and spore forming bacteria were detected in low counts while yeasts and molds were found in 15% and 20% of the honey samples, respectively. One retail honey sample did not meet the Codex Alimentarius standards in terms of its total glucose and fructose content while 75% of the honeys (60% and 90% of artisanal and retail honeys, respectively) had sucrose levels over the allowed limits (5%). There was a positive relationship between total phenolic content and DPPH scavenging activity of the honey samples. However, their antioxidant capacities were variable. Total 88 aroma compounds were detected by Gas Chromatography-Mass Spectrometry (GC-MS) analysis of the honeys. This study showed that there were not very sharp discriminations between retail and artisanal honeys when considering many of the parameters analyzed. Overall, it was confirmed that the quality of the analyzed honeys was good, which facilitates its national and international commercialization.

TURKISH JOURNAL OF AGRICULTURE AND FORESTRY, 2014

In the present study, response surface methodology was conducted for the determination of effects... more In the present study, response surface methodology was conducted for the determination of effects of some phenolics (gallic acid, ellagic acid, and quercetin) on some stability parameters of mixed oil prepared with sunflower and hazelnut oils (50:50, v/v). In this respect, peroxide value (PV), free fatty acids (FFAs), p-anisidine value, induction period, and refractive index of mixed oil were investigated. Predictive regression equations were constructed for the estimation of each studied parameter (R 2 > 0.861). The storage period caused a significant increase in the peroxide value, FFAs, p-anisidine, and refractive index values of the mixed oil, while it decreased the induction period value of oil (P < 0.01). The addition of gallic acid significantly retarded oxidation (P < 0.05), and in general gallic acid and quercetin were found to be effective for preserving oil against oxidation.

Food and Bioprocess Technology, 2012

In this study, effect of processing temperature (5, 15, 25, and 35°C) on the steady, dynamic, and... more In this study, effect of processing temperature (5, 15, 25, and 35°C) on the steady, dynamic, and creep recovery rheological properties of the ice cream mix (ICM) was investigated. It was found that processing temperature significantly affected all rheological parameters of the ICM sample. The flow behavior of the ICM sample was fitted to the Ostwald de Waele model. The magnitude of storage modulus (G′) was higher than that of loss modulus (G″) indicating that ICM sample had weak gel-like structure. Modified Cox-Merz rules were satisfactorily applied to the ICM sample to observe relationship between steady and dynamic shear properties. Additionally, Burger model was used to characterize the viscoelastic properties of the ICM sample. The gel strength (S) value was also calculated, and a decrease was observed with the increase of temperature. Arrhenius equation satisfactorily described the temperature dependency of the rheological parameters such as apparent viscosity at 50 s −1 (η 50 ), consistency coefficient (K), the instantaneous shear modulus of the Maxwell unit (G 0 ), permanent deformation (J ∞ ), and S values that may be predicted by using established equations depending on the temperature. The increase in processing temperature caused a decrease in resistance of the mixture subjected to the deformation, which is very important for production of high quality ice cream.

European Food Research and Technology, 2014

the ingredients simultaneously based on the requirements. The gum combination including 59.5 % ca... more the ingredients simultaneously based on the requirements. The gum combination including 59.5 % carrageenan and 40.5 % guar gum or 52.7 % carrageenan, 33.8 % guar gum and 13.5 % xanthan gum was determined to be the optimum in terms of quality of the product.

International Journal of Food Properties, 2015

Physicochemical (pH, brix, and color), sensory (color, taste, odor, mouthfeeling, consistency, bi... more Physicochemical (pH, brix, and color), sensory (color, taste, odor, mouthfeeling, consistency, bitter flavor, and general acceptability), and rheological properties of the hot chocolate beverages including different cocoa combinations were investigated in the present study. Cocoa type significantly affected all of the properties. Simple additive weighting approach was applied to obtain one score from seven different sensory parameters and simple additive weighting score was used in mixture design to determine optimum cocoa type or cocoa combination. Ostwald de Waele model described the flow behavior of the hot chocolate beverage samples with R 2 values ranged between 0.818 and 0.999. The consistency coefficient (K) and apparent viscosity at shear rate 50 s −1 (η 50 ) were significantly affected by cocoa type found in the formulation of the beverage. The mixture design approach was performed in order to determine variation of the responses (physicochemical, sensory, and rheological parameters) as a function of cocoa concentration. Simple additive weighting scores were satisfactorily described by established equation as a function of cocoa concentration to be used in the formulation of the hot chocolate beverage (R 2 = 0.8645).

International Journal of Food Properties, 2015

Principal component analysis and hierarchical cluster analysis were applied to investigate physic... more Principal component analysis and hierarchical cluster analysis were applied to investigate physicochemical and instrumental textural properties of fresh kashar cheese. Four different principal components sufficiently explained the variability in the cheese samples. In addition, hierarchical cluster analysis was performed to group the kashar cheese samples regarding physicochemical and instrumental textural properties. Instrumental textural properties indicated greater variability than chemical composition of cheese samples. Principal component analysis revealed that color parameters were positively correlated with textural and chemical parameters. The results of this study revealed that other parameters rather than chemical composition would be effective on the instrumental textural properties. It was proved that principal component analysis was a very effective statistical tool to determine quality of cheese samples. According to the principal component analysis and hierarchical cluster analysis results, the attributes defining the kashar cheese samples were determined to be primarily the texture profile analysis parameters.