(Anti) Nutritional, Techno-functional, and Antimicrobial Properties of the edible bush cricket, Ruspolia differens - A comparative nutritional analysis with locusts and crickets

The continuously growing human population and increasing food insecurity in sub-Saharan Africa stimulate the demand for affordable alternative and sustainable protein sources. Insects are among the most successful organisms on the planet. They have long been a traditional and cultural part of many African diets and are currently promoted as a mainstream source of energy and nutrients to tackle different forms of malnutrition.Of the several insect species consumed in sub-Saharan Africa, Ruspolia differens (Serville, 1983) (Orthoptera, Tettigoniidae) stands out. In East Africa, large volumes of this swarming, cone-headed bush cricket are harvested from the wild. However, the availability of wild-harvested insects is seasonal, limiting their continuous inclusion in diets. In this context, this thesis focuses on the (anti)nutrient content, sustainable rearing, and functional properties of R. differens to enhance food security. Therefore, I investigated the nutritional, anti-nutritional, and techno-functional properties of R. differens after processing. These properties were further compared with crickets and locusts, edible species belonging to the same insect order (Orthoptera). Moreover, I developed a novel artificial diet and conducted experiments to optimize the rearing of R. differens in captivity. As a potential non-food application, I also explored the antimicrobial potential of its extracts.Nutritional profiling after oven- and freeze-drying indicated that R. differens (on a dry matter basis) has a high lipid and protein content. Also, the presence of micronutrients, such as iron, zinc, manganese, and copper contributes to its nutritional quality. In terms of anti-nutrients, oven-drying, when compared to freeze-drying, resulted in significantly higher phytate contents in whole-insect and defatted flours obtained from R. differens, while the drying methods did not significantly affect the content of tannins.To optimize rearing conditions, several biological traits and fitness parameters were assessed for R. differens exposed to two distinct light regimes (i.e., <1h versus 12h photoperiods). The shortest developmental time (58 ± 3 days) and the highest survival rate (84 %) from hatchlings to adults were recorded when the insects were reared almost entirely in the dark (photoperiod <1h). Also, their average final weight was significantly higher (0.43 ± 0.03 g) when compared to insects exposed to a 12h photoperiod. The occurrence of cannibalism was identified as a fundamental challenge for mass-rearing of R. differens. This species also feeds on other insects' prey, an observation that may contribute to the development of rearing strategies in the future.Additionally, techno-functional properties of flours (water binding, foaming capacity and stability, and fat absorption capacity) and oils (acid value, iodine, saponification, and peroxide values) derived from processed (dried and defatted) insects were evaluated. Non-defatted or defatted insect flours could be included as ingredients in various food products to improve their functionality.

Publication year:2022

Accessibility:Embargoed