Research and development of technology for the production of yoghurt enriched with cereal β-glucan

Abstract

The dissertation is devoted to the development of an improved industrial technology for the production of Yogurt with functional properties due to the addition of dietary fibers. An urgent issue is the creation of fermented milk products with functional properties that contain all the nutrients vital for the body and have increased storage ability without the addition of preservatives. Yogurts contain all biologically active components necessary for the functioning of the body, except for ballast substances (dietary fibers). The introduction of dietary fibers into the composition of yogurts significantly increases their nutritional value and gives them functional properties. Dietary fibers are not absorbed by the body, but they play an important role in the digestion process, increasing intestinal peristalsis. It is known that dietary fibers affect the metabolism of cholesterol in the body, in particular, they stimulate the production and excretion of bile acids, which contain cholesterol. Products containing ballast substances should be included in the daily diet and can be used in therapeutic and preventive nutrition. The application of the oat β-glucan is offered as a source of dietary fibers. The effect of added 0.3% oat β-glucan in yogurt on protein digestion was evaluated using an in vitro gastrointestinal model. It was found that during the digestion phase in the stomach, the amount of soluble proteins and peptides increases up to 25% for the control Yogurt without additives and up to 40% for the yogurt with β-glucan. The presence of 0.3% β-glucan promotes the hydrolysis of product proteins in the gastric digestion phase. Compared with control Yogurt samples (without additives), inhibition of cholesterol solubility of β-glucan Yogurt showed no differences after transbuccal digestion, but was significantly higher after gastrointestinal digestion (21.3% for gastric and 22.7% for intestinal digestion). The research showed that oat β-glucan has water-holding capacity that allows it to maintain the product's optimal viscosity, texture and acidity during the entire storage period (21 days). It was established that the addition of β-glucan has a positive effect on the content of live probiotic bacteria in yogurt during 21 days of storage. Probiotics help stimulate gastric juices and natural enzymes necessary for proper digestion, reduce the number and severity of side effects of antibiotics, promote the breakdown of bile acid salts and normalize lipid metabolism. The presence of probiotic microorganisms in yogurt during the entire storage period gives it functional properties. Adding of oat β-glucan also improves the organoleptic and physicochemical properties of the product. The addition of oat β-glucans to Yogurt showed that the physical and textural properties of Yogurt can be significantly modified by the phase separation between β-glucan and milk proteins. Therefore, the purpose of the dissertation is the development and scientific justification of the technology of a high-quality fermented milk drink - Yogurt with the addition of oat β-glucan as a source of dietary fiber. The effect of the additive on the organoleptic, physicochemical, and rheological properties of the product was investigated in the dissertation. Also its digestibility and storage ability was studied. The therapeutic and preventive properties of the product have been confirmed by the method of medical and biological research. An improved industrial technology for the production of Yogurts with oat β-glucan has been developed by reducing the duration of fermentation by 1.5 hours. The introduction substantiates the relevance of the topic of the dissertation, reflects its connection with scientific programs and topics, defines and substantiates the purpose and tasks of the research, object, subject and main methods, indicates the novelty and practical significance of the obtained work results, determines the personal contribution of the candidate in the conducted research, approbation of the results, and publications on the topic of the dissertation, the structure and scope of the work are given. The first chapter analyzes and summarizes the data of the scientific and technical literature on the effect of oat β-glucan on the properties of fermented milk drinks, sources of dietary fiber acceptable for use in the production of food products. It is shown that oat β-glucan is a promising raw material for the production of yogurts with functional properties. In the second section, a general program of scientific research is developed, in which the main directions of the dissertation work are reflected, the materials and the subject of research are given. The section describes the methods and indicates the equipment that was used in conducting of experimental research. The experimental part of the work was carried out in laboratory conditions at the Department of Technology and Food Safety of the Sumy National Agrarian University and in the laboratories of the School of Food Sciences of the Henan Institute of Science and Technology (China). The industrial approval of the developed product was carried out on the basis of the BRANCH "Sumy Dairy Plant". The standard and generally accepted research methods were used in the study of physico-chemical, microbiological, structural-mechanical and organoleptic indicators, microstructure and nutritional and biological value. The results of the experiments were processed using the methods of mathematical statistics. In the third section, the effect of adding oat β-glucan on the quality of Yogurt, its viscosity, sensory indicators and physicochemical properties is investigated. Oat β-glucan was added to Yogurt of the set-type as a functional ingredient. It was found that the optimal amount to add is 0.3% of oat β-glucan. The introduction of the additive contributes to the improvement of the technology by reducing the fermentation time of yogurt by 1.5 hours. The acidity of set-type Yogurt with oat β-glucan was slightly higher. The addition of OG has a slight effect on chromaticity. The result of microstructure showed that the addition of oat β-glucan destroyed the three-dimensional network structure of Yogurt, and some spherical aggregate particles could be clearly observed at 0.3% OG. The addition of oat β-glucan increased the total number of lactic acid bacteria in the coagulated yogurt, and had a little effect on the fatty acid and amino acid composition of set-type yogurt. SPME-GC/MS analysis confirmed that the addition of oat β-glucan was helpful to increase the types of volatile flavor compounds in the set-type Yogurt. The storage experiment results showed that 0.3% oat β-glucan Yogurt has better water-holding capacity. The acidity value and pH reached their maximum values at 7 d of storage, and no significant (p<0.05) changes were observed after 7 d. Interestingly, the viscosity values increased throughout storage. The addition of 0.3% oat β-glucan has a protective effect on probiotic microflora in Yogurt, which confirms functional properties of the developed product. The textural characteristics of Yogurt were affected by the addition of 0.3% oat β-glucan, leading to decreased adhesiveness, but enhanced hardness and gumminess, throughout storage. The sensory results indicated that 0.3% oat β-glucan yogurt had the highest acceptability value of 86.49 at 14 d of storage. The fourth section studied the effect of OG on in vitro digestion characteristics of set-type yogurt ,the antioxidant activity of set-type yogurt during digestion , and the effects of OG set-type Yogurt on blood lipid metabolism in mice with a high fat diet . In the simulated in vitro digestion experiment, the effects of added 0.3% oat β- glucan in Yogurts on Yogurt protein digestion were evaluated using an in vitro gastrointestinal model. The amount of soluble proteins and peptides increased throughout digestion. Large spherical vesicles were formed for both control Yogurt and 0.3% oat β-glucan Yogurt after gastric digestion. 0.3% oat β-glucan Yogurt after digestion had higher antioxidant activity and higher inhibition of cholesterol solubility. 0.3% oat β- glucan Yogurt after digestion had higher antioxidant activity and higher inhibition of cholesterol solubility. Through DPPH -1,1-diphenyl-2-picrylhydrazyl radical and ABTS 2,2'-azino-bis(3-ethylbenzothiazoline-6-sulfonic acid assays, the antioxidant activity of yogurt was mainly produced during the gastric digestion phase, and 0.3% oat β- glucan could further improve the antioxidant activity of yogurt by promoting the beneficial enzymatic hydrolysis. And, compared with DPPH assay, ABTS assay is more suitable for evaluating the antioxidant activity of set-type Yogurt during digestion. In biomedical experiments, the effect of oat β- glucan set-type Yogurt on blood lipid metabolism in mice with high-fat diet was mainly determined Lee's index, blood lipids TG, TC, HDL, LDL, AST, ALT, liver weight and liver sections were studied. The experiment of effects of oat β-glucan set-type yogurt on blood lipid metabolism in mice with high fat diet provided evidence that 0.3% oat β- glucan set-type Yogurt can be an alternative and a complementary treatment to therapy of obesity-related complications. The fifth section organized the recipe, nutritional value of the product and the technological scheme for the production of Yogurt with addition of oat β- glucan. The production process of OG set-type yogurt is described, the energy loss is calculated, and the energy balance in the production process is carried out. The loss rate of materials is calculated by taking the production of 20 t oat β- glucan set-type Yogurt per day as an example. According to statistics and evaluation of the pilot production, the social and economic benefits of scientific and technological development and the implementation achievements in actual production are listed. The addition of oat β-glucan can effectively enhance the functional characteristics of fermented yoguyrt. Yogurt fortified 0.3% oat β-glucan could be an innovative healthy dairy for enhancing oat β- glucan consumption. OG set-type Yogurt products will bring more health benefits to consumers. Long-term and appropriate consumption will help consumers' health, reduce medical and health expenditure, and thus bring profound social and economic benefits.