De Volder Ann, De Smet Jeroen, Frooninckx Lotte, Deruytter David, Ceusters Johan, Vandeweyer Dries
Department of Microbial and Molecular Systems (M2S), KU Leuven, Geel Campus, Research Group for Insect Production and Processing (IP&P), Geel, Belgium.
Department of Biosystems, Research Group for Sustainable Crop Production and Protection (SusCroPP), KU Leuven, Geel Campus, Geel, Belgium.
Microbiologyopen. 2025 Jun;14(3):e70020. doi: 10.1002/mbo3.70020.
Insect farming generates substantial amounts of frass, a nutrient-rich by-product with valorization potential as fertilizer/soil improver. Marketing is restricted by EU regulations, imposing a reference heat treatment for 1 h at 70°C to reduce the presence of potential pathogens. This study evaluated the impact of heat treatments (50 → 80°C for 15 → 90 min) on microbiological quality and safety of black soldier fly larvae (BSFL) and yellow mealworm (YM) frass, as well as microbial dynamics during storage, before and after reference treatment. Fresh frass showed high microbial counts, but Salmonella was absent. Untreated BSFL frass did not meet the EU criteria to allow use as fertilizer, while some YM frass samples did. Reference heat-treated BSFL and YM frass complied with the EU criteria. Escherichia coli counts were below the 1000 cfu/g limit, and Salmonella (even when inoculated before treatment) was absent. Only in BSFL frass, Enterococcaceae counts were sufficiently reduced. Milder treatments (temperatures < 70°C and/or times < 1 h) of BSFL frass induced similar reductions of E. coli and (inoculated) Salmonella but Enterococcaceae counts remained above 1000 cfu/g. In some YM frass samples (inoculated) Salmonella was still detected after milder treatment. Refrigerated (4°C) or ambient temperature (26°C-28°C) storage up to 2 weeks of fresh and heat-treated frass did not increase bacterial counts. To ensure frass microbiological safety whilst preserving quality and reducing costs, tailored treatments seem appropriate. This may be no, milder, or more severe treatment, depending on the microbial load (counts and species type).
昆虫养殖会产生大量的虫粪，这是一种营养丰富的副产品，具有作为肥料/土壤改良剂的增值潜力。其销售受到欧盟法规的限制，法规要求进行70°C 1小时的标准热处理，以减少潜在病原体的存在。本研究评估了热处理（50 → 80°C，持续15 → 90分钟）对黑水虻幼虫（BSFL）和黄粉虫（YM）虫粪微生物质量和安全性的影响，以及在标准处理前后储存期间的微生物动态变化。新鲜虫粪显示出高微生物数量，但未检测到沙门氏菌。未经处理的BSFL虫粪不符合欧盟用作肥料的标准，而一些YM虫粪样本符合标准。经过标准热处理的BSFL和YM虫粪符合欧盟标准。大肠杆菌数量低于1000 cfu/g的限值，且未检测到沙门氏菌（即使在处理前接种）。仅在BSFL虫粪中，肠球菌科数量得到了充分减少。对BSFL虫粪进行较温和的处理（温度 < 70°C和/或时间<1小时）可使大肠杆菌和（接种的）沙门氏菌数量产生类似的减少，但肠球菌科数量仍高于1000 cfu/g。在一些YM虫粪样本中，较温和处理后仍检测到（接种的）沙门氏菌。将新鲜和热处理后的虫粪在4°C冷藏或26°C - 28°C环境温度下储存长达2周，细菌数量并未增加。为确保虫粪微生物安全，同时保持质量并降低成本，量身定制的处理方法似乎是合适的。这可能是不进行处理、较温和处理或更严格的处理，具体取决于微生物负荷（数量和种类）。
