Assessment of microbiological safety in the complex processing of secondary raw materials and food industry by-products into finished products
Year: 2026
Type: article
Abstract: This study analyses the qualitative and quantitative composition of the microflora in secondary raw materials of animal and plant origin used to produce extruded complete dry feed for service dogs. A total of 42 pooled samples were analysed — 18 samples of raw materials (chicken meat-and-bone meal, chicken fat, wheat, wheat bran, wheat gluten, corn gluten) and 24 samples of finished feed (four formulations). Microbial counts were determined by standard plate-count methods on meat-peptone agar, wort agar, MRS agar and Czapek agar, and pathogens were screened by membrane filtration on selective media (Endo, chromogenic TTC), following recognised national standards for food microbiology. Plant-derived components showed the highest initial bacterial load (wheat bran, 4.1×10⁵ CFU/g). Immediately after extrusion (up to 130 °C, 7–9 MPa), no mesophilic aerobic and facultatively anaerobic microorganisms, coliforms, Salmonella sp. or Clostridium botulinum were detected in any of the four feed formulations under the applied methods and their detection limits. After 6 months of storage at ambient warehouse temperature (not exceeding 25 °C) and relative humidity not exceeding 75 %, low levels of spore-forming Bacillus subtilis and B. mesentericus (1×10¹–4×10¹ CFU/g) persisted in all four formulations, and Mucor sp. (2×10¹ CFU/g) was additionally detected in one economy-class formulation. These findings indicate that extrusion substantially reduces microbial load but does not eliminate resistant spore forms; the absence of colony growth immediately after processing is reported here as an operational result under the stated detection limits, not as validated commercial sterility.
Source: Scifood.
DOI: 10.5219/scifood.77
Language: English
Topic: Food Safety and Hygiene
Subfield: Food Science
Domain: Life Sciences
SDG: Zero hunger
Open Access status: hybrid
OpenAlex ID: W7223703837