Biofilms associated with the final stages of Baker's compressed yeast production

Abstract

Purpose

The purpose of this paper is to assess equipment surfaces associated with the production of Baker's compressed yeast for microbial biofilms.

Design/methodology/approach

Yeast and bacteria (aerobic plate counts – APC, Enterococcus, E. coli and coliforms) attached to five processing equipment surfaces in a yeast processing factory were enumerated after dislodging from stainless steel squares (“mock” surfaces), or swabbing, after 7, 14, 21 and 28 days of yeast of production. Attached populations were visualized by scanning electron microscopy (SEM).

Findings

A similar increasing trend in attached bacterial counts on all equipment surfaces was observed over 28 days using both “mock” surface and swabbing techniques. However, bacterial and viable yeast counts obtained using “mock” surfaces were significantly higher (P<0.05) by ca. 1 to 2.5 log CFU/cm² compared to corresponding counts obtained by swabbing. Overall E. coli and coliform counts were below the lower detection limit (0.7 log CFU/cm²), Enterococcus counts ranged from 2.30 log CFU/cm² to 4.69 CFU/cm², and APC ranged from 2.17 CFU/cm² to 4.89 CFU/cm². Highest attached bacterial counts were consistently recorded on the hopper and extruder. SEM of “mock” surfaces confirmed the accumulation of yeast cells and attachment of rod and coccoid‐shaped bacterial cells. Predominant surface‐associated bacterial populations were Enterococcaceae (70%), Lactobacillus (20%) and Gram‐negative rods (10%).

Originality/value

Biofilms on stainless steel yeast processing equipment surfaces may act as potential sources of during production spoilage contamination of Baker's compressed yeast.

Citation

O'Brien, S.S., Lindsay, D. and von Holy, A. (2007), "Biofilms associated with the final stages of Baker's compressed yeast production", British Food Journal, Vol. 109 No. 1, pp. 20-30. https://doi.org/10.1108/00070700710718480