Master Degree / Yüksek Lisans Tezleri
Permanent URI for this collectionhttps://hdl.handle.net/11147/3008
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Master Thesis Investigation of Probiotic Properties of Cold Brewed and Fermented Cold Coffee Beverage(01. Izmir Institute of Technology, 2023) Semiz, Şevval; Baysal, Ayşe Handan; Baysal, Ayşe Handan; 03.08. Department of Food Engineering; 03. Faculty of Engineering; 01. Izmir Institute of TechnologyThe goal of the project was to produce a functional probiotic fermented cold brewed coffee that is perapered with medium roasted, grinded Colombian Arabica beans with patented probiotic yeast Saccharomyces boulardii that can survive in human gastrointestinal conditions. With pasteurization of the product, safe fermentation environment and long shelf life was achieved. Coffee brew samples were prepared with different techniques to understand the effects of fermentation and glucose fortification to fermentation media on coffee chemistry, microbiota and sensory characteristic. One of the three coffee brews was only pasteurized (P), one of them fermented (F) and the other was fermented with glucose (FG). The cold brewing and fermentation were performed respectively at 22 °C and 30 °C for 24 hours. The brewed samples were pasteurized before fermentation at 65 °C for 30 minutes. Each sample was examined during their 120 days shelf life (at +4 °C). Although the probiotic yeast enabled fermentation in coffee, it did not survive after the first week. Pasteurization was successful, so pathogen growth was not detected in any of the samples during their shelf life. While FG was evaluated as undrinkable, the other samples gave positive results in terms of sensory. Caffeine, chlorogenic acid, and ethanol levels were significantly altered during shelf life. This is the first study in which chemical, microbiological and sensory analyzes of cold coffee that was brewed via cold immersion method, pasteurized and fermented with patented S. boulardii yeast during shelf-life were conducted, and will lead to new studies in this field.Master Thesis Investigation of Applicability of Uv-Light Emitting Diodes (uv-Leds) as an Alternative Technology in Pasteurization of Cold-Pressed and Newly Formulated Mixed Beverage(Izmir Institute of Technology, 2022) Baykuş, Gökçen; Ünlütürk, Sevcan; Ünlütürk, Sevcan; 03.08. Department of Food Engineering; 03. Faculty of Engineering; 01. Izmir Institute of TechnologyThe aims of this thesis were to evaluate the cold pressing technique for juice extraction and to evaluate whether the cold pressed mixed beverage can be pasteurized with ultraviolet light emitting diodes (UV-LEDs) using E. coli K12 as the target microorganism. Initially, the physical, chemical and optical properties of cold pressed juice (CPJ) were compared with juice extracted by centrifugal juicer (CDJ). The CPJ was then exposed to UV-LEDs simultaneously and sequentially and the microbial inactivation was evaluated. Besides, barrier technologies have been tried to increase the UV-LED inactivation effect. It has been found that the juice yield performance of the cold pressing technique is better than the centrifuge method. The total phenolic content of the CDJ and CPJ was 922 ± 0.01 mg GAE/L, and 867.25 ± 0.01 mg GAE/L, respectively. However, DPPH radical scavenging activity of both beverages were not significantly different. The use of UV-LEDs in simultaneous or sequential mode could not achieve a 5-log reduction in pertinent microorganism required as part of HACCP mandated by US Federal regulations for juice issued by the Food and Drug Administration (FDA). However, filtration and addition of ginger juice revealed that the inactivation efficiency of UV-LEDs increased in highly turbid juice reaching to 3.65 ± 0.218 log10 CFU/ml. In conclusion, this study showed that UV-LEDs used simultaneously at different wavelengths may have the potential to be used in turbid cold press juice pasteurization when combined with different barrier technologies.Master Thesis Investigation of Microwave Processing for Pasteurization of Vegan Milk Products(01. Izmir Institute of Technology, 2021) Erol, Büşra; Korel, Figen; Erol, Büşra; Korel, Figen; Erdoğdu, Ferruh; 01. Izmir Institute of Technology; 03.08. Department of Food Engineering; 03. Faculty of EngineeringIn this study microwave processing was applied for the pasteurization of three different vegan milk products (almond, soy, and oat milk). For microwave process, 360 Watt power applied for 38 seconds. Also, results were compared with conventional thermal treatment which was carried out in a water bath at 70 ℃ during come-up times and 30 seconds holding time. For three vegan milk products, dielectric properties were investigated at different temperature values. After the treatments, important quality properties such as color, pH, particle size distribution and zeta potential values were evaluated. After all treatments, more than 5- log reduction of Salmonella Enteritidis was observed in three vegan milk products. Dielectric properties generally were significantly changed with temperature and frequency (p <0.05). Color differences of vegan milk samples were not perceptible or perceptible through close observation. The pH values generally were not affected by the heat treatments for soy and oat milk (p >0.05). Only there is a significant increase in the almond milk pH value with the heat treatments (p <0.05). Only soy milk's zeta potential values were significantly affected by the different processes (p <0.05). However, microwave pasteurized samples gave the closest value to untreated samples. Also holding process affected the stability of the oat milk. Particle size diameters were changed after the different processes. According to the results, the holding process is not required for the conventional pasteurization at 70 ℃. Microwave heating could be a promising new pasteurization method for vegan milk.