Master Degree / Yüksek Lisans Tezleri
Permanent URI for this collectionhttps://hdl.handle.net/11147/3008
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Master Thesis Development of Fermented Vegan Food Formulations With Improved Angiotensin-I Converting Enzyme Inhibitory (ace-I) Activity(01. Izmir Institute of Technology, 2022) Esen, Berna; Harsa, Hayriye ŞebnemVeganism has become popular in recent years and the demand for vegan products is increasing, especially due to the positive effects of plant-based diets on health. Since veganism can be defined as a diet or lifestyle that does not support the consumption of any animal food, protein-rich legumes occupy a large place in the daily diet of vegans. The health-promoting potential of probiotics in various forms has been recognized for years, and one of these health-promoting properties is their antihypertensive effect. In this context, the aim of this thesis is to develop some vegan food formulations, such as vegan mayonnaise-based salad dressings prepared using chickpea aquafaba and plant-based milk alternative (PBMA) fermented using lactic acid bacteria (LAB), showing antihypertensive effect. Microbiological, and quality characteristics and antioxidant properties of the formulations were determined. In addition, proteolytic activity and angiotensin-I converting enzyme inhibitory (ACE-I) activity experiments were carried out to control the antihypertensive properties of salad dressings. As a result, there are 107 CFU/ml bacteria in the final products. The quality characteristics of the formulations were compared with the literature. Consequently, the ACE-I activity of PBMA was enhanced by LAB fermentation and vegan mayonnaise was enriched with these high-value ingredients.Master Thesis Modulating Akkermansia Muciniphila by Probiotics for Obesity Management(Izmir Institute of Technology, 2021) Kamber, Aslıhan; Harsa, Hayriye Şebnem; Bulut Albayrak, ÇisemThe aim of this thesis is to investigate the potential of lactic acid bacteria (LAB) having probiotic properties to trigger Akkermansia muciniphila as anti-obesity candidate. Artisanal strains of LAB were evaluated in terms of stability in gastrointestinal conditions, mucin/mucus non-utilization properties, growth in the presence of mucin, adhesion to the mucin/mucus layer, biofilm formation, lactate production abilities, antimicrobial properties, HT-29 cell binding and mucin/mucus thickness increment abilities. Among 40 strains, 17 of LAB including 6 olive isolates were selected for their tolerance to gastrointestinal conditions and analyzed for further abilities e.g., mucin promotion potential. Most of them (13 of the 17 bacteria) remained viable in the range of 106-108CFU/mL in the simulated gastric juice, and these bacteria continued their viability in the range of 105-107 CFU/mL in the simulated intestinal fluid. Besides, 6 reference and 7 L. bulgaricus isolates did not utilize the mucin and showed no or negligible growth in the presence of mucin. Additionally, 13 of the 17 bacteria adhered to mucin layer with variable degree of binding between 41.03-65.37%. Furthermore, variable degree biofilm formation efficiencies can also support their existence and adhesion to intestinal cells. Varying amounts of lactate by 7 LAB were produced (6.51-18.17 g/L) and this ability is another important criteria for supporting mucus pathway. All those strains adhered to HT-29 cell line and they showed significant increase in mucin thickness by comparing the control. L. plantarum C47 and Lactobacillus AK50 isolates were selected as the antiobesity prototype candidates for their desirable attributes.Master Thesis Investigations on Aroma Profile of Artisanal Yoghurt Starter Cultyres(Izmir Institute of Technology, 2012) Baran, Ezgi; Harsa, Hayriye ŞebnemYoghurt is an important fermented milk product that is consumed widely around the world as a part of the diet. Yoghurt is produced by lactic acid fermentation using Streptococcus thermophilus, and Lactobacillus delbrueckii ssp. bulgaricus. The most important criteria in yoghurt production are the selection of artisanal yoghurt starter cultures to achieve the typical aroma and quality of the final product. The typical aroma of yoghurt is identified chiefly by acetaldehyde that is the most important for yoghurt aroma. The aim of this study is to determine artisanal yoghurt starter cultures that provide the most desirable aroma to yoghurt, in order to promote industrial production with such flavor. In the first part of this study, the influence of different aroma cultures addition on the aroma production properties in yoghurt products was investigated. Nine different aroma cultures were added into the starter culture combinations at two different inoculation ratios. Among all of the combinations, just one yoghurt combination was selected according to the highest acetaldehyde and also the highest sensory scores. According to the results, two batches of yoghurt were produced: Sample 1 containing only yoghurt starter cultures (Lactobacillus bulgaricus Y30 + Streptococcus thermophilus Y24), was used as control yoghurt; Sample 2 containing yoghurt starter cultures plus with selected aroma culture (P10), was used as yoghurt with aroma culture. Yoghurt samples were stored at 4 °C for 21 days. The pH, titratable acidity, total solids, fat, protein, syneresis, viscosity, aroma profile, lactic acid and lactose profile, proteolytic activity, microbiological characteristics and sensory characteristicsMaster Thesis Structural Changes of Gliadins During Sourdough Fermentation as a Promissing Approach To Gluten-Free Diet(Izmir Institute of Technology, 2010) Kömen, Gökçen; Harsa, Hayriye ŞebnemGluten intolerance, celiac disease, is an autoimmune disease caused by the ingestion of gluten proteins and the only treatment is the strict gluten-free diet which results in a mucosal recovery. At this point, the variety, availability and low price of gluten-free products on the market are of great importance. Sourdough is a traditional fermented semi-product that contains lactic acid bacteria (LAB). LAB are capable of metabolizing proteins and peptides with their proteolytic enzymes. It is predicted that gluten proteins are able to be hydrolyzed with the help of this proteolytic mechanisms and also by the wheat proteolytic enzymes. the help of this proteolytic mechanisms and also by the wheat proteolytic enzymes. gliadins involved in gluten intolerance during sourdough fermentation with selected LAB. First, sourdough fermentation with selected Lactobacillus strains was accomplished. As a control, dough with no inoculation and chemically acidified dough were prepared. During 48 h of fermentation, changes in pH, acidity, LAB concentration and free amino nitrogen content were investigated. SDS-PAGE, 2-D electrophoresis and RP-HPLC were applied to prolamins extracted from each sourdough sample taken at definite time intervals. The results showed that the inoculated LAB adapted to the dough environment and as they grew, a decrease in pH, and an increase in acidity and free amino nitrogen were observed. According to SDS-PAGE, 2-D electrophoresis and RP-HPLC results, some modifications in the protein patterns were observed in the inoculated doughs. The same alterations occurred in control and chemically acidified doughs, but not as fast as inoculated ones.