Evaluating the efficiency of oven and sun-drying traditional processing methods at bacterial quality improvement for black soldier fly (hermetia illucens) larvae.
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Date
2022
Authors
Mapiki, Prudence
Journal Title
Journal ISSN
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Publisher
The University of Zambia
Abstract
Black soldier fly (Hermetia illucens) larvae (BSFL) are a promising, sustainable source of nutrients for animals and humans. However, they could harbour potentially pathogenic bacteria such as Enterobacteriaceae and Staphylococcus aureus which could be carriers of antimicrobial resistance (AMR) genes due to the environment they are reared in. This is coupled with the limited knowledge regarding processing techniques to ensure food and feed safety on the utilization of BSFL. This study compared the efficiency of sun- and oven-drying methods which are the two commonly used traditional processing methods. The larvae
processed under the two methods were assessed for bacterial load and isolation. Furthermore, antibiotic susceptibility testing was done using disk diffusion, on the identified Escherichia coli and Staphylococcus isolates. PCR was used to identify ESBL and mecA genes in Escherichia coli and Staphylococcus isolates, respectively. Bacterial load for the two processing methods were compared using Jamovi version 2.3.21.0 software by using a Mann Whitney U test and the results indicated a significant difference (p < 0.001) in the efficiency of both methods. The oven-drying method reduced the Estimated Aerobic Total Plate Count
by 86.4% compared to the sun-drying method. Specifically, the observed cell counts were 3 x 103 CFU/mL and 2.6 x104 CFU/mL for oven and sun-drying, respectively. The results of the total bacterial load for both methods were below the acceptable limit for insects of animal feed which is 109 CFU/mL for an insect material to be considered safe for use in feed. One AMR gene (blaCTX-M) was detected from an E. coli strain isolated from sun-dried BSFL, indicating
the need to use more effective processing methods and the need for more diligence in the selection of suitable substrate for BSFL rearing. Altogether, the results suggest that ovendrying is a better method for processing BSFL for feed but, if one cannot afford, sun-drying can as well be used as it can result in a safe end product as long as source of the substrate is considered before use.
Description
Thesis of Master of Science Degree in Food Safety and Risk Analysis.