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    Effect of high pressure homogenization on microstructure and rheological properties of hazelnut beverage cold-set gels induced glucono-δ-lactone
    (Academic Press, 2021) Gul, O.; Sarıcaoğlu, Furkan Türker; Atalar, I.
    In this study, high pressure homogenized (HPH) hazelnut beverage samples were acidified with glucono-?-lactone (GDL) and rheological, structural and gel strength properties of the cold-set gels were characterized. Hazelnut beverage at a concentration of 10 g 100 mL?1 was treated with HPH up to 150 MPa pressure and then mixed with GDL (2 g 100 mL?1). Gelation of hazelnut beverages was observed with small deformation oscillatory measurements during 150 min. Hazelnut beverages acidified with GDL displayed shear thinning behavior due to decreasing viscosity with increasing shear rate, however, HPH led to an increase in apparent viscosities of cold set hazelnut beverage gels. Cold set hazelnut beverages were characterized as weak gel-like macromolecular dispersions due to storage modulus (G?) was higher than loss modulus (G?). Angular frequency dependence of complex modulus (G*) was studied to measure the strength of the cross-linking protein network of suspension systems by calculating a constant order of relaxation function (?) and concentration-dependent stiffness parameter (A?). This study revealed for the first time that hazelnut proteins can form good gel structures with acidification, and gel properties can be improved by HPH treatment. © 2021 Elsevier Ltd
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    Effect of thermal treatment on microbiological, physicochemical and structural properties of high pressure homogenised hazelnut beverage
    (Wageningen Academic Publishers, 2019) Atalar, I; Gul, O.; Mortas, M.; Gul, L. B.; Sarıcaoğlu, Furkan Türker; Yazici, F.
    The aim of this study was to investigate the effect of low (65, 72 and 85 degrees C) and high (105, 110 and 115 degrees C) temperature heat treatment on the microbiological, physical and chemical properties of high pressure homogenised hazelnut beverage. The total number of aerobic bacteria decreased with heat treatment and was not detected after 72 degrees C and higher heat treatments. The pH value of hazelnut beverage did not change significantly as a function of temperature (P>0.05). The total soluble content and soluble protein values of the low or high heat treated hazelnut beverage were significantly decreased after the heat treatments considered non-thermal treated ones, and also serum separation was adversely affected (P<0.05). Changes in colour components showed an increase in browning of hazelnut beverage by thermal treatment. The viscosity values of the samples significantly increased depending on the temperature except for the 65 degrees C treatment (P<0.05), and Herschel Bulkley's model was sufficient to describe the flow behaviour. Heat treatment at 85 degrees C for 5 min and higher temperatures led to an increase in particle size due to protein denaturation. Our results showed that the ideal temperature-time parameters were determined as 20 min at 72 degrees C and 1 min at 105 degrees C, based on microbiological results and better physicochemical properties.