The experiment was carried out in the laboratory of Dalian University of Technology (40°41′20.26″ N, 122°7′15.17″ E) in September–October 2021 at 22–26 °C ambient temperatures and approximately 12 daytime hours. The BSF eggs were hatched in a substrate containing soybean meal, corn meal, and wheat bran in a 6:3:1 ratio with 70% moisture content for 6–8 d. The emerging larvae were sieved out and weighed 0.0591 g per 100 individuals. The food waste was fully mixed by a kitchen blender and split into transparent plastic boxes. Each box was filled with 200 g of food waste, 20 g of wheat brain, and 480 larval individuals (0.2837 g). The boxes were 1250 mL in volume with several holds on the lids for passive aeration. A total of 30 parallel boxes were prepared. On Days 3, 5, 7, 9, 11, 13, 15, 17, 19, and 21, triplicate boxes were collected, and the larvae and frass were separated manually, weighted, and stored at −20 °C. Larval samples of all time points were subjected to the detection of body parameters and fatty acid properties. Frass samples of Days 7, 9, 11, 13, 15, and 17 were used for the determination of physiochemical properties.
Food waste components were further adjusted for analysis of carbohydrate effects on the larval bioconversion process. Three substrates were set as 100% food waste (FW100 CM0), 60% food waste and 40% corn meal (FW60 CM40), and 20% food waste and 80% corn meal (FW20 CM80). Percentages of each component were based on their wet weight. The FW100 CM0 group was the food waste treatment carried out above. The FW60 CM40 and FW20 CM80 groups were performed in the same manner as the experiments above, except that the waste components and sampling time points were adjusted. The food waste was still the university canteen waste, whereas the corn meal was prepared by mixing corn meal flour and water in a 3:7 ratio and cooking in a rice cooker for 0.5 h. When the substrates were mixed thoroughly, 21 parallel boxes were prepared for the FW60 CM40 and FW20 CM80 groups, respectively. The sampling time points were set as Days 3, 5, 7, 9,11, 13, and 15. At each time point, triplicate boxes were collected, and the larvae and frass were manually separated and weighted. The larvae were further analyzed for body FA contents and compositions, and the frass samples were further determined for the properties of reducing carbohydrates.
Food waste components were further adjusted for analysis of carbohydrate effects on the larval bioconversion process. Three substrates were set as 100% food waste (FW100 CM0), 60% food waste and 40% corn meal (FW60 CM40), and 20% food waste and 80% corn meal (FW20 CM80). Percentages of each component were based on their wet weight. The FW100 CM0 group was the food waste treatment carried out above. The FW60 CM40 and FW20 CM80 groups were performed in the same manner as the experiments above, except that the waste components and sampling time points were adjusted. The food waste was still the university canteen waste, whereas the corn meal was prepared by mixing corn meal flour and water in a 3:7 ratio and cooking in a rice cooker for 0.5 h. When the substrates were mixed thoroughly, 21 parallel boxes were prepared for the FW60 CM40 and FW20 CM80 groups, respectively. The sampling time points were set as Days 3, 5, 7, 9,11, 13, and 15. At each time point, triplicate boxes were collected, and the larvae and frass were manually separated and weighted. The larvae were further analyzed for body FA contents and compositions, and the frass samples were further determined for the properties of reducing carbohydrates.
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