Evaluation on techno-functional, fatty acids and in vitro antioxidant activity of edible house cricket (Acheta domesticus)

Abstract

Since prehistoric times, insects have been eaten by humans at every stage of their life, including eggs, larvae, pupae and adults. The main reason for this was that people did not have the necessary tools for hunting or farming. The use of insects for human consumption, as mentioned, is called entomophagy. The origin of this word is basically a combination of two Greek words, "ἔντομον (éntomon)" meaning "insects" and "φᾰγεῖν (phagein)" meaning "food". Currently, approximately 2.5 billion people worldwide engage in insect-eating action. In contrast, insect consumption in Europe is very low. It is thought that the rapidly increasing world population will reach 9.8 billion by 2050. Therefore, current food production needs to be doubled to ensure adequate food supply for the estimated population. This means that both land and water resources begin to become insufficient. On a dry basis, the protein part of insects is between 50% and 82%, and essential and semi-essential amino acids have made them an important food source. They also have a significant amount of lipids on a dry basis; Some insects, among all other sources of lipids, contain very high amounts of fat, up to 75% and carbohydrate value of insects between 6-16%, which contain high levels of glycogen and chitin. They usually contain a good amount of minerals, to be more specific, some insects have iron and calcium values that surpass livestock and also contain good amounts of zinc. The energy values of insects vary according to the amount of fat. Insects in the larval or pupal stage have more energy than adult insects due to their high fat content. In general, its energy values are similar to red meat, but not similar to pork, as it contains a large amount of fat. Insects have been applied to wounds, respiratory and stomach problems since ancient times, and there is little research on their functional properties. Insects possess many bioactive materials; They have attracted more attention from researchers due to their contents such as peptides, polysaccharides, fatty acids and phenols. Moreover, peptides obtained from insect proteins have been shown to have health benefits such as antihypertensive, antimicrobial and antioxidant properties. In vitro antioxidant properties of insects have shown that their protein hydrolysates exhibit similar antioxidant properties to fish, wheat and flaxseed protein hydrolysates. On the other hand, insects bring with them some risk factors when used for human consumption, as they may have some pathogenic microorganisms that carry disease. Moreover, from an industrial point of view, proteins are needed in many areas due to their techno-functional properties. Accordingly, insect proteins can be used to meet such needs. A. domesticus is an insect species that belongs to the Orthoptera order and its common name is "house cricket". Although A. domesticus can be found all over the world, its origin is in Southwest Asia. In the context of the textural, nutritional and taste aspects of this species, it is produced especially in Thailand for use in the diets of individuals. Previously, studies on house crickets were predominantly done for animal feed substitutes, but as times have changed, there is now more room to be studied for human food as well. In the thesis study, the techno-functional properties of A. domesticus were observed as flour, defatted flour, or protein extract obtained from flour. The water and oil binding capacity were performed in both defatted flour and flour. Water binding capacities were found 1.91 gwater/g for defatted insect flour, and 1.41 gwater/g for insect flour. While the oil binding capacity was 1.37 goil/g for defatted insect flour, and 0.93 goil/g for insect flour. The foam capacities of the extracted protein and insect flour were found to be 148.33% and 6.67%, respectively, while the foam stabilities were found to be 91.60% and 97.66%, respectively. The protein extracts of A. domesticus flour were studied at different pH (3-5-7) and different concentrations (0.1%, 0.08%, 0.06%, 0.04%, 0.02%) to find out the emulsifying activity, stability and capacity. In the results examined, the activity varied between 0% and 52.63%. All concentrations at pH 9 showed the highest activity with no significant difference between them. On the other hand, the highest emulsification stability was observed in pH 9 sample containing 85.46% and 0.1% protein. While the emulsifying capacity was observed in the samples at the highest pH value, it was observed that there was an inverse proportion between the protein concentrations and the capacity at this pH. Protein solubility was investigated on insect flour at different pH (3-5-7-9) of different salt concentrations (0% and 3%). Results varied between 2.85% and 52.32%. The highest solubility value was found at pH 9(0%) salt, while the lowest value was found at pH 5(0%). Although the addition of salt at pH 9 significantly reduced the solubility, it remained to show higher solubility than other pH values. A. domesticus flour was analyzed for its fatty acid composition, and cis-linoleic acid (C18:2n6) showed the highest fatty acid value with 35.77% it was followed by palmitic (C16:0) and cis-oleic acid (C18:1n9) with 26.46% and 25.85%, respectively. Linolenic acid (C18:3n3) and cis-linolenic acid (C18:3n6) were found to be 1.04% and 0.27%, respectively. The lowest fatty acid composition was observed as 0.21% for heptadecanoic acid (C17:0). Some saturated fatty acids were also found, such as myristic acid (C14:0), palmitic acid (C16:0), palmitoleic acid (C16:1), stearic acid (C18:0) and heneicosanoic acid (C21:0). As a result of the DPPH analysis performed after in vitro gastrointestinal digestion, the IC50 (mg/ml) value was found to be too high as 31.96 for the stomach and 78.27 for the intestine. Inhibition percentages were found as 78.3% and 31.96% for the stomach and intestines, and values in terms of Trolox equivalent were observed as 3.62 mgTE/g in the stomach and 1.54 mgTE/g in the intestine. The results of this thesis clearly showed that A. domesticus flour and its derivatives showed potential as techno-functional. In addition, various fatty acid content and moreover, antioxidant properties obtained as a result of in vitro gastrointestinal digestion were similar to the results in the literature on health and showed that it could be used in this direction.