Master Degree / Yüksek Lisans Tezleri
Permanent URI for this collectionhttps://hdl.handle.net/11147/3008
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Master Thesis Dynamics and Bioinformatis of Microbial Spoilage Ecology of Kefir(Izmir Institute of Technology, 2022) Memon, Ayşe; Baysal, Ayşe Handan; Sezgin, EfeIn this study, it was aimed to characterize the microbiological properties, bacterial composition, and microbial stability of 5 different commercial milk kefir beverage products during refrigerated storage. In order to determine the microbiological load and compositions, total mesophilic aerobic bacteria, yeast and molds, lactic acid bacteria, Lactobacilli, Lactococci, total coliforms, and E.coli were investigated by cultural conventional analysis for milk kefir beverages. According to the obtained data, microbiological and hygienic characteristics of the samples were found acceptable. The bacterial load of the kefir beverage samples ranged between 7.086 and 8.794 log10 cfu.ml-1 for viable total aerobic mesophilic bacteria (TAMB), 6.792 and 8.382 og10 cfu.ml-1 for lactic bacteria (LAB), <10 and 6.322 log10 cfu.ml-1for Lactobacillus, 5.857 and 8.146 log10 cfu.ml-1 Lactococcus, 5.176 and 7.218 log10 cfu.ml-1 for yeasts, negative for molds, coliform bacteria and negative for E. coli. Principal component analysis (PCA) of the compounds separated the kefir beverages according to the storage time and kefir brands. Strong relationship were found between storage time and PC1 and between kefir brands and PC2. To date, information on microbial properties, bacterial composition, and constancy of commercial kefir is scant, and to the best of our knowledge, this is the first research to contribute information on kefir beverages in microbial properties, bacterial composition, and their stability during refrigerated storage by evaluating Fourier Transform Infrared Spectroscopy (FTIR) spectra analysis and Bioinformatics besides cultural conventional analysis.Master Thesis Phylogenetic Analysis of Bacterial Communities in Kefir by Metagenomics(Izmir Institute of Technology, 2008) Ünsal, Burcu; Arslanoğlu, AlperKefir is a traditional fermented milk beverage which is produced by adding kefir grains into milk and is allowed for fermentation. Grains contain vital complex flora of microorganisms (bacteria and yeast) that live in harmony. Since health and food safety of fermented milk products is important, population structure of food-type microbes involve in fermentation should be known very well. Rapid determination of kefir bacterial composition may accelerate the determination of food quality and also may facilitate specification of bioactive products that obtain from kefir. The goal of this thesis was to analysis the genomic structure of bacterial communities of the fermented kefir drink and grains by both culture-dependent and culture-independent methods (metagenomic approach). Total Genomic DNA was purified from each analysis methods and the partial small subunits of 16S rDNA were amplified by a pair of universal bacterial primers. 16S rDNAs fragments were cloned and then sequenced. The vast quantities of data were screened in NCBI database by BLASTN program according to similarity scores with related sequences. 7 different bacteria were identified to species level composed of Lactococcus lactis subsp. lactis , Lactobacillus kefiranofaciens, Lactobacillus helveticus, Acetobacter lovaniensis, Acetobacter syzygii, Leuconostoc mesenteroides, Enterococcus faecium and 1 bacteria to genus level named Lactobacillus kefiri or parabucheri. The results of this study showed that the combination of both methods is more efficient to identify high percentage of species than using only one of them. Finally, phylogenetic relationships among identified species inferred from partial 16S rRNAs gene sequencing were determined by Neighbor-joining algorithm.Master Thesis Production of Kefir From Bovine and Oat Milk Mixture(Izmir Institute of Technology, 2011) Kahraman, Cihan; Korel, FigenDuring recent years non-dairy milk types such as cereal and grain milks have been an increased demand from consumers due to their functional properties. The cereal and grain milks do not contain cholesterol or lactose; therefore, these milk types are preferred by consumers who are vegetarians, have special diets or are lactose intolerant.In this study, different concentrations of oat milk (0, 15, 30, 45, and 60%), blueberry aroma(9, 12, 15, 18, and 21%), and kefir culture(1, 2, 3, 4, and 5%) were used for the optimization of the kefir production and samples were stored at 4C for 21 days. The response surface methodology was used for the optimization process. Sensory characteristics, the pH changes and microbial characteristics of the kefir samples were determined during storage and the concentrations of the oat milk, blueberry aroma and kefir culture for the best three kefir products were chosen based on the optimization results According to optimization results, three kefir samples which contained the highest level of oat milk with optimum organoleptic characteristics, optimum pH and optimum microbial counts were selected and produced. Based on the organoleptic results, kefir samples composed of 20% oat milk, 4% kefir culture and 10% aroma concentration, were produced. According to the pH results kefir samples within 15% oat milk, 4% kefir culture and 9% aroma concentration were produced. Based on the microbiological results kefir samples within 30% oat milk, 3% kefir culture and 15% aroma concentration were produced. The pH, titratable acidity, dry matter, fat, protein, phenol content, beta-glucan content, whey off, viscosity, volatile and organic acid profile of samples, color change, microbiological characteristics and sensory characteristics of these samples were investigated during 21 days of storage.