Investigation of bioactive, physical, textural and sensory properties of Spirulina platensis added fermented milk during the storage process

With the developing food technology, people today aim to reach maximum nutritional elements in nutrition, even in a single meal. However, the popularity of high-protein foods has increased. While milk and fermented milk products with increased protein content take their place on the shelves, the protein sources of these products or how they are produced have become controversial. Spirulina platensis is a plant-derived, high protein planktonic blue-green cyanobacteria. In this thesis, it is aimed to obtain a herbal, new and functional food with high therapeutic effect and protein content by considering the nutritional values of Spirulina, also known as algae. For this purpose, fermented milk products were produced with the addition of Spirulina platensis at four different concentrations (0%, 0,5%, 0,1% and 1,5%) together with the Control sample. The effect on the physical, textural and sensory quality of fermented milk products was investigated with the addition of Spirulina platensis on the 1st, 7th, 14th and 21st days during the 4-week storage period. In addition, the produced fermented milk products were digested in vitro and their bioactive properties were examined. Moisture and protein analysis was performed on Spirulina platensis and its chemical properties were examined. In addition, information about the soluble protein was obtained according to the total protein amount and comments were made by looking at the isoelectric points of the protein. The highest amount of water-soluble protein was observed at pH 9, while the lowest protein solubility was at pH 3.5. It was determined that the addition of Spirulina platensis did not have a significant effect on the pH value, ash content and titratable acidity of the samples. However, as the Spirulina platensis concentration in the samples increased, the dry matter content of the samples decreased, and the syneresis and water holding capacity increased. As a result of the Kjeldahl protein analysis performed on fermented milk products, it was determined that the highest protein content was found in the S3 sample containing 1,5% Spirulina platensis. Texture analysis was performed on fermented milk products on the 1st, 7th, 14th and 21st days. According to the results of this analysis, no significant change was observed in the internal stickiness, flexibility and gumminess values depending on storage and Spirulina concentration. As a result of color analysis, L* values decreased and a* and b* values increased with the addition of Spirulina platensis. According to the results of the sensory analysis, the effect of Spirulina platensis addition on the odor, sea odor and general impression parameters of the samples was found to be statistically significant (p<0.05). The panelists gave the Control sample the highest score in the overall impression parameter based on taste. This sample was followed by the S1 sample containing 0,5% Spirulina platensis. In the last stage of the study, the bioactive properties of Spirulina platensis added fermented milk products were determined using the in vitro method, and as a result, it was determined that the antioxidant capacity and total phenolic content of the product increased, and it showed antihypertensive and antidiabetic properties. All these results showed that Spirulina platensis can play a role in the production and development of fermented milk products and can achieve the intended targets.