Master Degree / Yüksek Lisans Tezleri

Permanent URI for this collectionhttps://hdl.handle.net/11147/3008

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Department: search.filters.department.Thesis (Master)--İzmir Institute of Technology, Food EngineeringSubject: search.filters.subject.Yogurt

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  • Master Thesis
    Development of Strained Yogurt Ice Cream With Aronia and Hydrolyzed Collagen
    (01. Izmir Institute of Technology, 2024) Korel, Figen; Korel, Figen; 03.08. Department of Food Engineering; 03. Faculty of Engineering; 01. Izmir Institute of Technology
    Yogurt ice cream, made using yogurt cultures Lactobacillus delbrueckii subsp. bulgaricus and Streptococcus thermophilus, is integrated with freezing technology, and it is a healthy food that creates cooling effect on consumers. In this study, it was aimed to obtain strained yogurt ice cream that would allow consumption of hydrolyzed collagen and aronia together. Different concentrations of collagen were added to samples with and without aronia. Different amounts of stevia were also added to selected sample due to its antioxidant activity. The quality of the ice creams in the study were evaluated by analyses as follows; dry matter, protein, fat, ash, carbohydrates, pH, color, viscosity, overrun, melting rate, antioxidant activity, coliform and lactic acid bacteria counts, and sensory analyses. While aronia decreased pH, collagen increased pH; adding stevia did not cause any significant change on pH. A correct proportion was observed between the viscosity and fat content of formulations. Samples were examined for antioxidant activity by DPPH and total phenolic content analyses. According to DPPH analysis results, sample B containing 20g of aronia had highest antioxidant activity. According to total phenolic content analysis, sample F containing 20g of aronia and 2.5g of hydrolyzed collagen had the highest total phenolic content. After the antioxidant activity was evaluated, stevia was added as a sweetener to sample E, which contained 1g of hydrolyzed collagen. According to sensory analysis results, sample E1 containing 20g of aronia, 1g of collagen and 0.006g of stevia was the most liked yogurt ice cream in terms of taste.
  • Master Thesis
    Isolation, Phenotypic and Genotypic Charecterization of Yoghurt Starter Bacteris
    (Izmir Institute of Technology, 2007) Erkuş, Oylum; Harsa, Hayriye Şebnem; Harsa, Şebnem; 03.08. Department of Food Engineering; 03. Faculty of Engineering; 01. Izmir Institute of Technology
    Specific bacteria cultures, known as starters, are used for manufacturing of fermented milk products. Yoghurt is made from milk by the protocooperative action of well known starters, namely Lactobacillus delbrueckii ssp. bulgaricus and Streptococcus thermophilus. They lead to coagulation of milk by lactic acid fermentation and other products give the characteristic properties, such as acidity, aroma, and consistency. Traditional method, using part of a previous batch to inoculate a new batch, have been used for centuries. Such cultures lead to variable performance, however industrial production needs consistency. The method of choice is the use of bacterial strains with known physiological, biochemical and genotypic characters. The isolation and identification of natural starters is a need not only for the dairy industry, which still import starters abroad, but also for the preservation of natural lactic acid bacteria diversity of Anatolia. With this perspective, the aim of our study was the isolation of starters from artisanal yoghurts, and their biochemical and molecular characterization. At the end of the study, 66 cocci and 71 bacilli were isolated. According to biochemical identification, all the bacilli isolates were found to be L. delbrueckii ssp. bulgaricus, however cocci isolates showed highly variable sugar fermentation results and only 7 of them were characterized as S. thermophilus. The molecular characterization was based on the amplification and restriction fragment length polymorphism (RFLP) of 16S ribosomal DNA (rDNA) and internal transcribed spacer (ITS) region. Species-specific PCR amplification and 16S sequencing were also used for justification. All of the isolates were well identified with the help of molecular techniques.