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Cricket (Acheta domesticus) Protien Hydrolysates: Functional Properties and Application in a Food Matrix
The farming of insects has been shown to require less land, feed, and water compared to traditional livestock maintenance, while proven to be a source of high-quality protein. The aversion of the Western culture towards edible insects is the major hurdle into their incorporation in the market, unveiling the challenge of integrating them into an existing familiar product. However, studies have shown that merely pulverizing insects into edible “flours” possesses difficulties on itself such as low solubility; severely altering the structural and sensory characteristics of food products upon their addition. Alternatively, scientists have turned to chemical protein isolation techniques to create insect flours with improved functionality. Furthermore, enzymatic proteolysis has shown to aid in extracting the protein bound to insoluble chitin and enhancing techno-functional properties. While this promising technique may open a range of possibilities, no research has been done regarding the incorporation of insect hydrolysates into a food matrix. The purpose of this work was to explore the production of insect hydrolysates with improved techno-functional properties and their impact in the physicochemical, structural, and sensory characteristics on a chosen model matrix: corn tortillas. Crickets (Acheta domesticus) were chosen due to their current relevance in the Western market.
Hydrolysates were produced with low (5%), medium (8%), and high (15%) degrees of hydrolysis (DH) either with Alcalase (AL) or Flavourzyme (FL). Alcalase cricket protein hydrolysates (CPH) resulted in higher fat content, which was suspected of possessing surface-activity. Overall, AL peptides displayed significantly (p < 0.05) higher emulsion and foam capacity and stability, suggesting stronger amphiphilic activity. On the other hand, FL peptides were more soluble and had a lower mean molecular weight, demonstrated by their lower glass transition temperatures. Both of these developments may be explained by Alcalase endopeptidase activity and Flavourzyme primarily exopeptidase activity. Treatments resulted in AL-peptides with large and medium size molecular weights that included hydrophobic terminal ends, while FL peptides were smaller and likely contained free amino acids. The difference in molecular weights were seen upon their addition in the raw corn masa, where AL-CPH increased elastic and viscous behavior compared to control, whereas the smaller FL-CPH lowered them due to the plasticizing capability of hydrophilic small peptides. The ability of FL-CPH to interact with corn macromolecules was observed upon thermal treatment, resulting in FL-tortillas with superior strength and extensibility compared to AL-tortillas. In fact, AL-tortillas fragility was seen by the rollability test, showing a complete disintegration of the tortilla structure. Raman spectroscopy further showed the heat-induced intermolecular interactions of FL-peptides with the corn macromolecules. Raman bands at 1049 cm-1 in FL-tortillas allude to protein-starch complexes and the gauche-gauche region confirmed the presence of disulfide bridges in FL-tortillas, both of these developments were absent in AL-tortillas. Lastly, the formulation of corn chips with these CPH proved to be globally accepted by a population with diverse neophobia levels, confirming theories that consumers are willing to eat insects in an “invisible” format. Flavor and aroma profiles of the chips, quantified by a descriptive analysis study, revealed no commonalities between the two sets of chips. AL-chips were characterized as having corn, shrimp, and roasted peanut notes, while FL-chips were characterized as having tomato, ketchup, and French fry notes. Overall, enzymatic proteolysis was shown to generate cricket peptides with different characteristics, both able to be utilize as a functional ingredient for palatable food products.