Optimization of extraction of different fractions from Locusta migratoria, characterization and investigation of usage in food system

Objective: The thesis study aimed to optimize the process conditions for oil and protein extraction from Locusta migratoria and to characterize the obtained fractions. Additionally, the possibility of utilizing the protein fraction in a food system was investigated. Material and Methods: Locusta migratoria was first subjected to freeze drying and the physicochemical properties of the resulting powder sample were determined. The oil extraction process, where the temperature, time and solvent/sample ratio were evaluated as the process parameters, was optimized using the response surface methodology (RSM). Locusta migratoria oil produced under optimum conditions was characterized. Protein extraction was carried out from the defatted powder sample remaining after the oil extraction process, using two different methods: alkaline and enzymatic. Alkaline protein extraction process parameters were determined as temperature, time and pH; enzymatic protein extraction process parameters were determined as temperature, time and enzyme ratio. Both protein extraction processes were optimized using RSM. The structural and techno-functional properties of the protein fractions obtained under optimum process conditions, were compared. The fraction obtained by the enzymatic extraction was used for the enrichment of food system (muffin). Physicochemical and textural properties of muffin samples produced with protein content of 2.5%, 5%, 7.5% and 10% were determined and the samples were evaluated for their sensorial aspects. Results: The optimum process conditions for oil extraction were determined as 30°C temperature, 80 minutes time and 17:1 mL/g solvent/sample ratio. In Locusta migratoria oil obtained under these conditions, the predominant fatty acid was determined to be oleic acid (36.82%) and the major triglyceride was palmitodiolein (14.97%). The sterol content of the oil obtained is 12638.66 mg/kg and 83.80% of the total sterols is cholesterol. Additionally, a significant amount of γ-tocopherol (223.31 ppm) was detected in the oil. The optimum protein extraction conditions were determined to be 50.62ºC temperature, 95.50 minutes time and 11.15 pH for the alkaline process; 51.68ºC temperature, 115.56 minutes time and 9.69% enzyme ratio for the enzymatic process. The basic amino acid in the protein fractions obtained by both methods under optimum conditions was lysine. The essential amino acid index (EAAI) value was found to be higher in the fraction obtained as a result of enzymatic extraction. SEM images revealed that both protein fractions had similar spherical morphological structure. When the FTIR spectra were examined, characteristic bands were observed in the amide I and amide III regions in the protein fraction obtained by the alkaline extraction and in the amide B and amide II regions in the protein fraction obtained by the enzymatic extraction. Statistically significant differences were found between the techno-functional properties of the protein fractions except foam stability (p<0.05). Texture profile analysis applied to muffin samples revealed that, with the increase in protein fraction, especially hardness, gumminess and chewiness values were affected significantly. The data obtained as a result of sensory analysis showed that the muffin samples with 2.5% protein fraction were generally liked by the panelists. Increasing the protein fraction to 10% negatively affected the textural properties and consumer preference of the samples. Conclusion: In this thesis study, oil and protein extraction conditions from Locusta migratoria, an alternative food source, were optimized and the phases produced under optimum conditions were characterized. It was concluded that the obtained protein fraction could be used in food systems.