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    Dynamic rheological characterization of salep glucomannan/galactomannan-based milk beverages
    (Elsevier Sci Ltd, 2009) Yasar, Kurban; Kahyaoglu, Talip; Sahan, Nuray
    The steady flow and viscoelastic properties of glucomannan (salep) and galactomannans (locust bean gum, LBG and guar gum, GG) in milk beverages were investigated at 25 and 50 degrees C. The consistency index (K), flow behavior index (n), yield stress and thixotropic area were measured as functions of steady shear; elastic modulus (G'), loss modulus (G ''), tan delta and complex viscosity (eta*) parameters were derived from oscillatory shear experiments. The steady flow behavior of mannan-based milk beverages was observed to be shear-thinning and thixotropic. Galactomannans exhibited greater shear-thinning and thixotropy than glucomannan in milk beverages. The synergistic effect was detected between salep and LBG with highest thixotropy. Increasing the temperature decreased Casson yield stresses of GG but not salep and LBG samples. Similar viscoelastic behavior was observed between salep and LBG, they could be classified as concentrated solutions but GG showed gel-like structure. At low frequencies, high tan delta values were observed for the salep and LBG samples indicating viscous character. On the other hand, GG sample had nearly the same tan delta values through the frequency sweep. Cox-Merz rule was tested to correlate the steady and dynamic viscosities of samples. It was found that Cox-Merz rule was applicable only to LBG-milk beverage among the studied samples. (C) 2008 Elsevier Ltd. All rights reserved.
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    Öğe
    Influence of fat replacers on chemical composition, proteolysis, texture profiles, meltability and sensory properties of low-fat Kashar cheese
    (Cambridge Univ Press, 2008) Sahan, Nuray; Yasar, Kurban; Hayaloglu, Ali A.; Karaca, Oya B.; Kaya, Ahmet
    Changes in chemical composition, proteolysis, lipolysis, texture, melting and sensory properties of low-fat Kashar cheese made with three different fat replacers (Simplesse((R)) D-100, Avicel Plus((R)) CM 2159 or P-glucan) were investigated throughout ripening. The low-fat cheeses made with fat replacers were compared with full- and low-fat counterparts as controls. Reduction of fat caused increases in moisture and protein contents and decreases in moisture-in-non fat substance and yield values in low-fat cheeses. The use of fat replacers in the manufacture of low-fat Kashar cheese increased water binding capacity and improved overall quality of the cheeses. Use of fat replacer in low-fat cheese making has enhanced cheese proteolysis. All samples underwent lipolysis during ripening and low-fat cheeses with fat replacers had higher level of total free fatty acid than full- or low-fat control cheeses. Texture attributes and meltability significantly increased with addition of fat replacers. Sensory scores showed that the full-fat cheese was awarded best in all stages of ripening and low-fat variant of Kashar cheeses have inferior quality. However, fat replacers except P-glucan improved the appearance, texture and flavour attributes of low-fat cheeses. When the fat replacers are compared, the low-fat cheese with Avicel Plus((R)) CM 2159 was highly acceptable and had sensory attributes closest to full-fat Kashar cheese.
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    Öğe
    The effects of using exopolysaccharide producing cultures on the microbiological, physicochemical and sensory properties of ayran
    (M H Schaper Gmbh Co Kg, 2006) Sahan, Nuray; Var, Isil; Yasar, Kurban; Zorlugenc, Buelent
    In this study, the microbial properties of ayran made from different starter cultures were investigated during refrigerated storage for 1, 8 or 15 days. Microbiological, physicochemical and also sensory properties of ayran were examined. It was determined that the different starter cultures had a significant effect on the numbers of lactic acid bacteria (p < 0.05),total aerobic mesophilic bacteria (p < 0.05) and yeast counts (p < 0.01). The storage time had a significant effect on the lactic acid bacteria (p < 0.05). The use of various starter cultures significantly influenced acetaldehyde contents (p < 0.05), viscosity (p < 0.01), whey separation (p < 0.01), appearance (p < 0.05) as well as body and texture (p < 0.01). The storage time affected volatile fatty acids (p < 0.01), whey separation (p < 0.01) and appearance (p < 0.01). Addition of exopolysaccharide producing cultures decreased whey separation and caused an increase in viscosity and sensory scores in ayran samples. It is recommended that precautions should be taken to decrease whey separation to prevent the negative effect of storage time.