Functional, Antioxidant, and Anti-Inflammatory Properties of Cricket Protein Concentrate (Gryllus assimilis)

Edible insects can represent an alternative to obtain high-quality proteins with positive biological properties for human consumption. Cricket flour (Gryllus assimilis) was used to obtain cricket protein concentrate (CPC) using pHs (10.0 and 12.0) of extraction and pHs (3.0, 4.0, 5.0, and 6.0) of isoelectric precipitation (pI). Protein content, water and oil absorption capacity, protein solubility, antioxidant, and anti-inflammatory activities were determined. In addition, the protein profile was characterized by electrophoresis and the in vitro CPC digestibility was evaluated. Cricket flour presented 45.75% of protein content and CPC 12-5.0 presented a value of 71.16% protein content using the Dumas method. All samples were more soluble at pH 9.0 and 12.0. CPC 12-3.0 presented a percentage of water-binding capacity (WBC) of 41.25%. CPC 12-6.0 presented a percentage of oil-binding capacity (OBC) of 72.93%. All samples presented a high antioxidant and anti-inflammatory activity. CPC 12-4.0 presented a value FRAP of 70,034 umol trolox equivalents (TE)/g CPC, CPC 12-6.0 presented a value ABTS of 124,300 umol TE/g CPC and CPC 10-3.0 presented a DPPH value of 68,009 umol TE/g CPC. CPC 10-6.0 and CPC 12-6.0 presented high anti-inflammatory activity, with values of 93.55% and 93.15% of protection, respectively. CPCs can be used as functional ingredients in the food industry for their excellent functional and biological properties.

Enzymatic hydrolysis of black cricket (Gryllus assimilis) proteins positively affects their antioxidant properties

The development of innovative ingredients through biotechnological routes has established insect proteins as an emerging source of bioactive peptides. The current study aimed to evaluate the antioxidant properties of black cricket (Gryllus assimilis) protein hydrolysates produced using the proteases Flavourzyme^TM 500L, Alcalase^TM 2.4L, and Neutrase^TM 0.8L, either individually or in binary/ternary combinations. The enzymatic hydrolysis promoted an increase of approximately 160% in total antioxidant capacity and 93% in the ferric reducing antioxidant power. The isolated use of the enzyme Flavourzyme^TM 500L showed the most prominent positive effect on the antioxidant properties, presenting an IC₅₀ value of 455 and 71 µg/mL for DPPH and ABTS radicals scavenging activities, respectively. This sample was composed mainly of small peptides (MW < 3 kDa), in which the antioxidant properties increased after fractionation by ultrafiltration. Gel electrophoresis analysis showed protein hydrolysates composed mainly of polypeptide chains with a mass of less than 14 kDa. Finally, the enzymatic treatment proved to be an efficient process to improve the antioxidant properties of black cricket proteins, increasing the possibility of applying these hydrolysates as bioactive ingredients in food or nutraceutical products. PRACTICAL APPLICATION: Insects represent an alternative source of proteins. Their modification through hydrolysis allows for the acquisition of compounds with great potential in industrial applications, such as functional ingredients or for nutraceutical purposes. The use of our experimental design proved to be an adequate tool for defining the best process conditions required for increasing the attainment of biologically active compounds.

Developmental changes in the levels and redox potentials of main hemolymph thiols/disulfides in the Jamaican field cricket Gryllus assimilis

Main thiols and disulfides were determined in the hemolymph of the Jamaican field cricket Gryllus assimilis at various developmental stages. On the basis of these data, redox potentials of the glutathione, cysteine and homocysteine redox systems were calculated. The concentrations of all thiols studied decreased during development (at a stage of 6 molts) with respect to young crickets, and increased again in adult insects. Redox potentials of the glutathione and cysteine systems increased from values of -131.0±5.6 mV and -86.9±17.1 mV, respectively in young crickets to -58.0±3.6 mV and -36.1±4.2 mV, respectively, at the stage of 6 molts and decreased to values of -110.4±24.8 mV and -66.3±12.2 mV, respectively, in adult insects. Redox potentials of the glutathione and cysteine systems in the hemolymph of young and adult insects were similar to those reported for human plasma.

Nutritional Potential of Selected Insect Species Reared on the Island of Sumatra

Inhabitants of the Indonesian island of Sumatra are faced with the problem of insufficient food supplies and the consequent risk of undernourishment and health issues. Edible insects as a traditional and readily available food source could be part of the solution. The nutritional value of insects depends on many factors, e.g., species, developmental stage, sex, diet, and climatic conditions. However, edible insects bred in Sumatra for human consumption have never before been assessed with regard to their nutritional value. Our study involved analyses of crude protein, chitin, fat and selected fatty acid contents of giant mealworm larvae (Zophobas morio), larvae of the common mealworm (Tenebrio molitor) and nymphs of the field cricket (Gryllus assimilis). Crude protein content in the samples ranged from 46% to 56%. Highest (35%) and lowest (31%) amounts of fat were recorded in giant mealworm larvae and larvae of the common mealworm, respectively. Chitin amounts ranged from 6% to 13%. Based on these values, which are comparable to those known from other food insects reared in different regions of the world, the edible species bred in Sumatra could become food sources with a potential to help stave off hunger and undernourishment.

Regulation of body metal concentrations: Toxicokinetics of cadmium and zinc in crickets

Previous studies indicated that essential and xenobiotic metals differ substantially in terms of their toxicokinetics. Whether these differences are due to different assimilation rates, different elimination rates, or both, and whether all metals are regulated in a similar manner but with different efficiency remains unclear. To compare the mechanisms responsible for the regulation of different metals, parameters for toxicokinetic models have to be tested under exposures to the identical molar concentration of those metals. In this study, the cricket Gryllus assimilis was exposed to Zn or Cd at 2.5, 10, and 40mMkg(-1) dry food. The body concentrations of the metals were not perfectly regulated by the crickets. For Zn, a clear increase in the body concentration was found only at the highest treatment; whereas at the lowest treatment, the internal concentration remained unchanged throughout the experiment. At the lowest Zn concentration, the assimilation (kA) [day(-1)] and elimination (kE) [day(-1)] rate constants were balanced (kA=0.024, kE=0.024). When increasing the Zn exposure, kA decreased to 0.018 at 10mMkg(-1) and 0.01 at 40mMkg(-1), and kE increased to 0.05 and 0.07, respectively. Therefore, the body concentration of Zn was regulated by simultaneously changing the assimilation and elimination rate. By contrast, even at the lowest treatment, a significant increase in Cd concentration was observed in the crickets. The equilibrium Cd concentration resulted almost exclusively from increasing kE from 0.17, through 0.28 to 0.61 at 2.5, 10 and 40mMkg(-1). The kA for Cd did not reveal any clear trend. Zn was more efficiently regulated by crickets than was Cd: a 16-fold increase in exposure concentration (from 2.5 to 40mM Znkg(-1)) resulted only in a twofold increase of internal concentration, whereas the identical increase in Cd exposure concentration resulted in almost a sevenfold increase in internal concentration of this metal.

How male sound pressure level influences phonotaxis in virgin female Jamaican field crickets (Gryllus assimilis)

Understanding female mate preference is important for determining the strength and direction of sexual trait evolution. The sound pressure level (SPL) acoustic signalers use is often an important predictor of mating success because higher sound pressure levels are detectable at greater distances. If females are more attracted to signals produced at higher sound pressure levels, then the potential fitness impacts of signalling at higher sound pressure levels should be elevated beyond what would be expected from detection distance alone. Here we manipulated the sound pressure level of cricket mate attraction signals to determine how female phonotaxis was influenced. We examined female phonotaxis using two common experimental methods: spherical treadmills and open arenas. Both methods showed similar results, with females exhibiting greatest phonotaxis towards loud sound pressure levels relative to the standard signal (69 vs. 60 dB SPL) but showing reduced phonotaxis towards very loud sound pressure level signals relative to the standard (77 vs. 60 dB SPL). Reduced female phonotaxis towards supernormal stimuli may signify an acoustic startle response, an absence of other required sensory cues, or perceived increases in predation risk.

How age influences phonotaxis in virgin female Jamaican field crickets (Gryllus assimilis)

Female mating preference can be a dominant force shaping the evolution of sexual signals. However, females rarely have consistent mating preferences throughout their lives. Preference flexibility results from complex interactions of predation risk, social and sexual experience, and age. Because residual reproductive value should theoretically decline with age, older females should not be as choosy as younger females. We explored how age influences phonotaxis towards a standard mate attraction signal using a spherical treadmill (trackball) and a no-choice experimental protocol. Female Jamaican field crickets, Gryllus assimilis, were highly variable in their phonotaxis; age explained up to 64% of this variation. Females 10 days post imaginal eclosion and older oriented toward the mate attraction signal, with 10- and 13-day females exhibiting the greatest movement in the direction of the signal. Our study suggests 10- and 13-day old females would be most responsive when quantifying the preference landscape for G. assimilis sexual signals.