Kailgraudu mieži ierauga fermentācijā = Hull-less barley in sourdough fermentation
Authors:   ,   Latvia University of Life Sciences and Technologies, Reidzāne Sanita 
Published: May 2024

The doctoral thesis "Hull-less barley in sourdough fermentation" was developed from February 2020 to December 2023 in the Latvia University of Life Sciences and Technologies (LBTU) Food Institute (former Faculty of Food Technology) laboratories. The analyses of samples were conducted at the Institute of Agricultural Resources and Economics (AREI) of Stende Research Centre, Division of Smart Technologies (LBTU), Center of Food and Fermentation Technologies (TFTAK) in Estonia, Budapest University of Technology and Economics, Department of Applied Biotechnology and Food Science. Statistical data processing was conducted in collaboration with the Institute of Computer Systems and Data Science of the Faculty of Engineering and Information Technologies. The hypothesis of doctoral thesis: hull-less barley is an alternative raw material for sourdough fermentation and breadmaking. Research objects: hull-less barley spontaneous sourdough, with starter cultures fermented sourdough, as well as hull-less barley sourdough bread. The following theses have proved the hypothesis. 1. Under the influence of optimal technological fermentation parameters, the succession of typical sourdough microbiota occurs. 2. The microbiological and physical indicators of the spontaneous sourdough of hull-less barley resemble the characteristic indicators of active sourdough, and sourdough fermented with starter cultures can possess enhanced proteolytic activity. 3. The gluten content in hull-less barley sourdough fermentation decreases relative to its content in flour. 4. The content of non-starch polysaccharides affects the physical properties of bread. The aim of doctoral thesis: to study the fermentation of hull-less barley sourdough and evaluate its effect on the content of gluten and non-starch polysaccharides and the physical properties of barley bread. The tasks set to achieve the goals. 1. To determine the optimal technological parameters for the spontaneous fermentation of hull-less barley and the taxonomic composition of lactic acid bacteria and microscopic fungi. 2. To specify the microbiota succession in the spontaneous sourdough fermentation of hull-less barley. 3. To evaluate the quality indicators and rheological properties of hull-less barley sourdough fermented spontaneously and with starter cultures. 4. To study the physical properties of hull-less barley and wholegrain wheat bread prepared with hull-less barley sourdough. 5. To determine the gluten content in hull-less barley sourdough and hull-less barley bread. 6. To analyze the content of non-starch polysaccharides in hull-less barley and wholegrain wheat bread and to explain their effect on the physical properties of the bread. The thesis is summarized in three chapters. Chapter 1 characterizes the types of sourdough and describes the main influencing factors of sourdough. Reflected spontaneous sourdough microbiota. Characteristics of hull-less barley as an alternative raw material are given. The information regarding the structure of sourdough and dough is provided. An insight into changes in flour's chemical composition and physical properties during sourdough fermentation is provided. Chapter 2 outlines the materials and methods used in the study. Chapter 3 summarizes the results of the study.  The influence of variable factors in the three steps of fermentation of hull-less barley was characterized, and the optimal technological parameters were determined. Identified microbiota and analyzed its succession in the three steps of fermentation.  Microbiological (number of lactic acid bacteria, yeasts colony-forming units) physical (pH, complex viscosity, loss and storage moduli) and chemical (titratable acidity, proteolytic activity) indicators of hull-less barley sourdough summarized; structure formation and changes in sourdough and dough fermentation were analyzed.  The content of gluten in hull-less barley flour and sourdough was determined, and its changes in bread prepared with hull-less barley sourdough were analyzed.  The content of β-glucans, fructans, and mannans in bread prepared with hull-less barley sourdough was analyzed, and their influence on the physical properties of the bread was elucidated. A PhD thesis is written in Latvian, it consists of 100 pages, 16 tables, 23 images and 173 bibliographic sources and 4 appendices. The study was financed by the grants: “Strengthening Research Capacity at Latvia University of Life Sciences and Technologies” project “The biotechnological solutions for barley sourdough” (Contract No 3.2.-10 /125); Latvia University of Life Sciences and Technologies program project “Biologically active compound content in the developed barley bread” (Contract No 2020-LLU-141); “Transition to the new doctoral funding model at the Latvia University of Life Sciences and Technologies” (Contract No 8.2.2.0/ 20/I/001).