Ropiness in Bread—A Re-Emerging Spoilage Phenomenon

Abstract

As bread is a very important staple food, its spoilage threatens global food security. Ropy bread spoilage manifests in sticky and stringy degradation of the crumb, slime formation, discoloration, and an odor reminiscent of rotting fruit. Increasing consumer demand for preservative-free products and global warming may increase the occurrence of ropy spoilage. Bacillus amyloliquefaciens, B. subtilis, B. licheniformis, the B. cereus group, B. pumilus, B. sonorensis, Cytobacillus firmus, Niallia circulans, Paenibacillus polymyxa, and Priestia megaterium were reported to cause ropiness in bread. Process hygiene does not prevent ropy spoilage, as contamination of flour with these Bacillus species is unavoidable due to their occurrence as a part of the endophytic commensal microbiota of wheat and the formation of heat-stable endospores that are not inactivated during processing, baking, or storage. To date, the underlying mechanisms behind ropy bread spoilage remain unclear, high-throughput screening tools to identify rope-forming bacteria are missing, and only a limited number of strategies to reduce rope spoilage were described. This review provides a current overview on (i) routes of entry of Bacillus endospores into bread, (ii) bacterial species implicated in rope spoilage, (iii) factors influencing rope development, and (iv) methods used to assess bacterial rope-forming potential. Finally, we pinpoint key gaps in knowledge and related challenges, as well as future research questions.

Exploring the Inhibitory Activity of Selected Lactic Acid Bacteria against Bread Rope Spoilage Agents

“…Sourdough's pH varies depending on the state of fermentation; however, it typically ranges between 3.5 and 5. Harmful microorganisms such as botulism bacteria, E. coli, and spoilage fungi cannot develop in an environment with a pH below 4.6, as this acidity keeps them away [5,57]. We observed that the majority of the strains were able to lower the pH around 4-4.5 (considered a safe pH to avoid spoilage) after 10 h, exhibiting a high acidification ability and underlining the massive production of acids (lactic and acetic acid).…”

Psyllium and okra mucilage as co-carrier wall materials for fenugreek oil encapsulation and its utilization as fat replacers in pan bread and biscuit production

“…Mansuri et al [ 56 ] stated the antibacterial activity of fenugreek oil nanoemulsion against Bacillus subtilis, Staphylococcus aureus, Escherichia coli and Pseudomonas aeruginosa. The members of Bacillus genus ( B. subtilis, B. cereus, and B. licheniformis ) are the causative organisms for the ropeness phenomenon, which is a bacterial decomposition of the bread making it unsafe and improper for consumption [ 105 ]. Also, Nampuak and Tongkhao [ 106 ] showed that okra mucilage exerted strong inhibitory effects against Bacillus cereus, Staphylococcus aureus and Listeria monocytogenes .…”

Isolation and screening of lactic acid bacteria and yeast starters from ersho (traditional Ethiopian sourdoughs) and evaluation of their role in bread production

“…Microbial growth during bread storage produces an unpleasant odour that alters the bread's sensory qualities. They also produce discolouring, slimy rope, and bread crumb degradation by releasing amylase and protease enzymes (Pacher et al ., 2022).…”