INSECT PROTEIN EXTRACTION AND FRACTIONATION VIA MICROWAVE, PH-SHIFTING, AND MEMBRANE SEPARATION: STRATEGIES TOWARDS INNOVATIVE INGREDIENTS FROM SUSTAINABLE SOURCES
This thesis investigates environmentally friendly methods for extracting and fractionating proteins from edible insects to obtain fractions with improved techno-functional and bioactive properties. Three approaches were studied: microwave-assisted alkaline extraction (MAAE), pH-shifting, and membrane-based separation, providing sustainable alternatives to conventional methods. Four insect species were selected: mealworm (Tenebrio molitor), house cricket (Acheta domesticus), grasshopper (Locusta migratoria), and black soldier fly (Hermetia illucens). MAAE as a mild and effective extraction technique, an increase protein yield was observed particularly for cricket with irradiation energy but had inconsistent effects on emulsifying and foaming properties. pH-shifting, as a chemical modification method, improved the protein functionalities by altering structural and physicochemical properties. Cricket and grasshopper proteins maintained emulsifying capacity while increasing foaming ability after alkaline treatment, suggesting potential for emulsion- and foam-based foods. Ultrafiltration (UF) enhanced protein fractions’ interfacial properties using a 30 kDa membrane. Lowering protein concentration improved permeate flux for mealworm protein but not BSF, highlighting the influence of protein composition. Slight increase in pH improved BSF permeate flux and influenced techno-functional trends depending on the insect. Cricket permeate at pH 7 showed collagenase inhibition and no cytotoxicity, indicating cosmetic application potential. Cascade membrane systems were tested in two configurations. Configuration A (microfiltration followed by three UF steps) yielded balanced protein distribution, whereas Configuration B (500 → 100 → 30 kDa) concentrated proteins early, particularly at 500 kDa, and enhanced emulsifying activity across fractions. Overall, environmentally friendly extraction methods, pH-shifting, and membrane cascades produces insect protein fractions with tailored techno-functional and bioactive properties, supporting their use in food, feed, and cosmeceutical applications.
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