Emergence of Leuconostoc mesenteroides as a causative agent of oozing in carrots stored under non‐ventilated conditions

Abstract

SummaryLong‐term storage and transport of post‐harvest carrots (Daucus carota L.) require a low‐temperature, high‐relative‐humidity environment, usually with low ventilation. Following long‐term storage, a slimy exudate (oozing) often appears on the carrots, leading to severe spoilage. We characterized the environmental conditions leading to these symptoms and identified the causative agent. Simulation of non‐ventilated storage conditions revealed accumulation of CO 2 (to 80%) and ethanol (to 1000 ppm); then, a transparent exudate appeared on the carrot surface which, upon ventilation, developed into tissue browning and soft rot. Peels from oozing carrots contained over 10‐fold the total bacterial counts of healthy carrots. The total peel microbiome was determined by 16S rDNA sequencing. During oozing stage, the surface of carrots incubated in a CO 2‐rich (98%) environment harboured a bacterial population dominated by Lactobacillales and Enterobacteriales, differing markedly from those incubated in air. Three prevalent bacterial isolates from the oozing carrots were identified as Pantoea agglomerans, Rahnella aquatilis and Leuconostoc mesenteroides. Inoculation of carrot discs with L. mesenteroides, but not the others, induced oozing under high CO 2, suggesting that this bacterium is responsible for oozing of stored carrots. These findings should enable development of approaches to preventing carrot spoilage during long‐term storage.

Enrichment and Characterisation of a Mixed-Source Ethanologenic Community Degrading the Organic Fraction of Municipal Solid Waste Under Minimal Environmental Control

“…The SOC initial average similarity (43.97%) was mostly due to five OTUs, three of which were not taxonomically assignable below the bacterial domain level, This diversity decreased (32.29%) by 11 days and was characterised by three sequence types all closely related to Leuconostoc mesenteroides (>97% similarity), a facultative anaerobe typically found on the skin of fruits and vegetables (Lampert et al, 2017) and two Pseudomonas sequence types related (99% similarity) to Pseudomonas proteolytica and Pseudomonas weihenstephanensis , both isolated from raw milk and dairy products (Stoeckel et al, 2016; Von Neubeck et al, 2016). These sequence types accounted for up to 73.87% of the cumulative similarity of these 11-day replicates.…”

Abundance, diversity and plant‐specific adaptations of plant‐associated lactic acid bacteria

“…Generalist LAB are also responsible for food spoilage. Post‐harvest spoilage of carrots was found to be the result of uncontrolled growth of L. mesenteroides (Lampert et al ., ). Psychrotrophic, generalist species of Leuconostoc and Lactococcus such as Leuconostoc gasicomitatum , Leuconostoc gelidum and Lactococcus piscium have been associated with spoilage of ready‐to‐eat salads (Pothakos et al ., ).…”

Microbial safety and probiotic potential of packaged yogurt products in Pakistan

“…L. mesenteroides strains have been used as dairy starters (Akabanda, Owusu‐Kwarteng, Tano‐Debrah, Parkouda, & Jespersen, ; Hati, Mandal, & Prajapati, ), and was previously isolated from fermented vegetables (Anisha, Anandham, Kwon, Gandhi, & Gopal, ; Dallal, Zamaniahari, Davoodabadi, Hosseini, & Rajabi, ). However, these fermentation abilities are highly strain‐specific (Lampert et al, ). L. acidophilus is one of the most commonly used probiotic species (Bull, Plummer, Marchesi, & Mahenthiralingam, ), frequently added to yogurt along with starter to aid fermentation and add probiotic value (Pyar & Peh, ).…”