Determination of the antimicrobial effect of Spirulina platensis in the model systems

Spirulina platensis has commercial value with its high protein, rich vitamin, pigment content and low fat content. Increasing research emphasizes the nutritional values and positive contributions of algae to human health as a sustainable food alternative. In this context, high pressure and sonication techniques from new non-thermal technologies are effectively used. In this study, the effects of high pressure and sonication processes on the rheological, thermal, structural and particle size distribution of the dry powder form of Spirulina platensis were investigated. For this purpose, Spirulina platensis was dissolved in different solvents, and high pressure homogenization (500, 1000, 1500 bar) at different rates and different amplitude degrees; The effects of non-thermal technologies on Spirulina platensis samples were investigated by applying ultrasound-assisted sonication (sound waves) at %50-100amp and durations (10, 15, 30 min). When the results were evaluated, it was seen that 500 bar high pressure application showed the highest antimicrobial effect (15,60) against B. subtilis bacteria. Protein rates were found to be 81.88% at 50 amp and 77.30% at 500 bar, but no statistically significant difference was found (p>0.05). It is thought that the high protein rate found may be due to the genetic structure of Spirulina. In the study, the TPC value was obtained at 100% amplitude and 30 minutes in sonication application (426.43 mgGAE/100ml), while the highest TPC value was obtained at 1500 bar in pressure application (741.86 mgGAE/100ml). Compared to the control, increasing the amplitude and duration in sonication application and increasing the pressure in high pressure application caused an increase in the total phenolic substance amount. When looking at the Dpph values, it was seen that the sample that was not applied at all in UAE and HPH had the highest value (143.77 μmol TE/ml). In HPH and UAE applications, the color values were different from the control and a statistically significant difference was found between them (p<0.05). The highest L*(brightness) value was obtained at 1000 bar (21.116), the highest a*(+red, -green) value was obtained at 500 bar (-4.483), and the highest b*(+yellow, -blue) was obtained at 1000 bar (-3.153). As a result of the project, it was seen that more successful results were obtained in the degradation of the cell wall of Spirulina platensis microalgae in high pressure application compared to ultrasound-assisted extraction.