Hrytsevich M. “ Improving the technology of low-protein cookies" - Qualifying scientific work on the rights of the manuscript.
Dissertation for the degree of Doctor of Philosophy in the speciality 181 "Food Technologies" - National University of Food Technologies, Ministry of Education and Science of Ukraine, Kyiv 2023.
The dissertation is devoted to the improvement of low-protein cookies technology that could be consumed by patients with phenylketonuria.
The thesis discusses the issue of phenylketonuria, including its prevalence, symptoms and treatment methods, especially dietary therapy. Dietary therapy is recognised as the most effective treatment, and the scientific work provides recommendations on a low-protein diet and daily intake of phenylalanine for patients. A separate aspect is devoted to the analysis of the market for low-protein foods for people with phenylketonuria and the study of the composition of traditional biscuits with a focus on reducing the phenylalanine content.
The literature review indicates that there are no detailed publications on low-protein cookies formulations and their properties. The components for further research of low-protein cookies technology, in particular hydrocolloids and starches, were selected. A research flowchart for improving production technologies was developed.
A number of low-protein cookies recipes have been developed and a model of an ideal product for children of different ages with phenylketonuria has been calculated.
The study of the rheological properties of low-protein emulsions showed that the viscosity curves exhibit shear thinning behaviour, which is typical of pseudoplastic liquids. The presence of xanthan gum increases the viscosity of the emulsions, and the replacement of butter with corn oil led to a decrease in viscosity. Emulsions with higher viscosities require more powerful equipment.
The bubbles of the dispersed phase of the emulsion without structuring agents are characterised by heterogeneity in size, it is recommended to increase the whipping speed to obtain a more uniform consistency.
The study of the rheological properties of the dough revealed that the viscosity moduli of low-protein dough are lower than those of traditional butter dough, and the elasticity and viscosity curves do not intersect, indicating that the dough does not flow. All low-protein dough samples are recommended to be moulded using the notching method. The complex viscosities of low-protein products are in the same range as the dough for traditional cookies, which confirms the possibility of production using existing equipment.
The analysis of alveographic studies confirms the absence of elasticity in low-protein dough, and the addition of tapioca starch increases the extensibility, which facilitates dough moulding.
The samples of low-protein and traditional dough have pronounced plastic properties. The addition of maltodextrin and tapioca starch increases the elasticity of the dough. Samples of low-protein dough and dough for the production of traditional butter biscuits are deformed under force and do not fully restore their shape. The recovery coefficients for low-protein dough are in the range of 0.385 to 0.525, and for traditional butter biscuit dough - 0.490.
The dough for low-protein cookies has similar rheological properties to the dough for traditional cookies, which confirms the possibility of producing low-protein cookies using existing equipment.
As a result of the thermal analysis carried out by thermogravimetry and differential scanning calorimetry, the temperature of loss of all calculated moisture of low-protein samples was determined, and the thermal decomposition of the studied samples during further heating was proved.
It has been established that the rational duration of baking and drying of low-protein cookies is 40% longer than that of traditional butter cookies. It was determined that less energy is required for the heat treatment of traditional butter cookies than for the heat treatment of low-protein cookies (ΔH=124.05 J/g and ΔH=199.46-268.33 J/g, respectively). The addition of maltodextrin to low-protein dough formulations does not significantly reduce the amount of energy required for cookies heat treatment, while the replacement of 20% corn starch with tapioca starch reduces the amount of energy required for cookies heat treatment by 25.7%.
It has been determined that the sensory characteristics of low-protein cookies meet the requirements of current regulatory documents, and heat treatment affects the geometric dimensions of products, requiring adjustment of moulding equipment. The physicochemical characteristics of the developed low-protein products comply with the current regulatory documents, and the phenylalanine content makes them safe for consumption by patients with phenylketonuria.
Low-protein cookies exhibit polymolecular adsorption with changes in moisture retention, affecting their shelf life.
