Occurrence and enumeration of rope-producing spore forming bacteria in flour and their spoilage potential in different bread formulations

Abstract

This study aimed to investigate the prevalence of spore forming rope-producing microorganisms in different types of flour and to evaluate the potential for spoilage of the isolates through the simulation of the bread manufacturing process. Mesophilic and thermophilic aerobic spore forming bacteria were enumerated in 100 flour samples. Strains isolates were evaluated for their ability to produce amylase and cause rope spoilage in different bread formulations. Amylase-producing strains were identified through 16S rRNA sequencing. The wholemeal flour from industry presented the highest aerobic mesophilic spore forming bacteria counts (3.1 log spores/g). A total of 327 strains were isolated from flours, among which 45 produced amylase. These isolates were identified as Bacillus licheniformis (62%), B. sonorensis (20%) B. cereus (11%), B. pumilus (2%), and Paenibacillus polymyxa (2%). All 45 strains were able to cause spoilage in bread with and without preservatives. The addition of calcium propionate and reduction of water activity and pH were able to prevent the development of rope for 7 days. The development of new formulations can help to assure the microbiological quality and safety of baked products.