Skip to main content

LUP Student Papers

LUND UNIVERSITY LIBRARIES

Application of Novel Plant Probiotics to Increase the Health Value of Ready-to-Eat Leafy Greens

De Mel, Rumathi LU (2024) KLTM02 20241
Food Technology and Nutrition (M.Sc.)
Abstract
Ready-to-eat (RTE) leafy greens offer an appealing way to integrate leafy greens into meals. Unfortunately, these leafy greens can
get contaminated with human pathogens such as Salmonella, and Shiga toxin producing Escherichia coli (STEC) at any stage along the
manufacturing chain, potentially leading to serious foodborne diseases. Currently, there is no single step in the production and processing of RTE leafy vegetables that guarantees the elimination of all potential pathogens, leaving the final product susceptible to contamination. To address this challenge, this master’s thesis proposes a novel approach: the direct inoculation of previously evaluated plant probiotics on the day of delivery, known for their antagonistic effects... (More)
Ready-to-eat (RTE) leafy greens offer an appealing way to integrate leafy greens into meals. Unfortunately, these leafy greens can
get contaminated with human pathogens such as Salmonella, and Shiga toxin producing Escherichia coli (STEC) at any stage along the
manufacturing chain, potentially leading to serious foodborne diseases. Currently, there is no single step in the production and processing of RTE leafy vegetables that guarantees the elimination of all potential pathogens, leaving the final product susceptible to contamination. To address this challenge, this master’s thesis proposes a novel approach: the direct inoculation of previously evaluated plant probiotics on the day of delivery, known for their antagonistic effects against E. coli. The bacterial levels on the day of delivery and the best-before date were analyzed using viable cell count, quantitative polymerase chain reaction (qPCR), and Next Generation Sequencing (NGS).

The findings from the viable cell count revealed a consistent reduction in non-pathogenic E. coli for all the plant probiotic strains tested. Particularly, Bacillus coagulans LMG P-32205 and Pseudomonas cedrina LMG P-32207 showed the most significant effectiveness (p ≤ 0.01) throughout the shelf-life period. Additionally, qPCR analysis showed that Pseudomonas cedrina LMG P-32207 had higher concentrations on the last day of shelf-life compared to the control. Moreover, Illumina MiSeq sequencing revealed a lower relative abundance of pathogenic genera, especially Escherichia coli, in the microbiota of the leafy greens. The mixed salad and mixed lettuce samples inoculated with probiotics exhibited a higher relative abundance of Proteobacteria and Bacteroidetes compared to the control group. Over all trials, the top family with the highest relative abundance was Pseudomonadaceae.

The α-diversity exhibited variations only among mixed lettuce and mixed salad samples inoculated with probiotics. Higher β-diversity was observed in all mixed salad groups compared to day 1, as a shift to the right. Indicating that inoculation of probiotics and E. coli has induced substantial changes in the native microbiota of the mixed salad leaves. The effect of probiotic strains varied between different leafy green products, thus no conclusions could be drawn. Nonetheless, these results encourage the use of bacterial antagonists as part of a global solution to reduce the risk of human pathogens on leafy green vegetables. (Less)
Popular Abstract (Swedish)
Färdigskurna bladgrönsaker erbjuder ett tilltalande sätt att inkludera lite grönt i måltider. Tyvärr kan dessa bladgrönsaker bli kontaminerade med humana patogener som Salmonella och shiga toxin producerande Escherichia coli (STEC) i tillverkningskedjan, vilket kan leda till allvarliga livsmedelsburna sjukdomar. För närvarande finns det ingen enskild åtgärd I produktionen eller bearbetningen av de färdigskurna bladgrönsakerna som garanterar eliminering av potentiella patogener. För att tackla denna utmaning föreslår denna masteravhandling en ny metod: applicering av tidigare utvärderade växtprobiotika kända för sina antagonistiska effekter mot E. coli på bladgrönsaker. Bakterienivåerna på leveransdagen och bäst-före-datumet analyserades... (More)
Färdigskurna bladgrönsaker erbjuder ett tilltalande sätt att inkludera lite grönt i måltider. Tyvärr kan dessa bladgrönsaker bli kontaminerade med humana patogener som Salmonella och shiga toxin producerande Escherichia coli (STEC) i tillverkningskedjan, vilket kan leda till allvarliga livsmedelsburna sjukdomar. För närvarande finns det ingen enskild åtgärd I produktionen eller bearbetningen av de färdigskurna bladgrönsakerna som garanterar eliminering av potentiella patogener. För att tackla denna utmaning föreslår denna masteravhandling en ny metod: applicering av tidigare utvärderade växtprobiotika kända för sina antagonistiska effekter mot E. coli på bladgrönsaker. Bakterienivåerna på leveransdagen och bäst-före-datumet analyserades med hjälp ahjälp av odling, quantitative polymerase chain reaction (qPCR) och Next Generation Sequencing (NGS).

Resultaten från odlingen visade en konsekvent minskning av E. coli för alla testade växtprobiotiska stammar. Särskilt Bacillus coagulans LMG P-32205 och Pseudomonas cedrina LMG P-32207 visade den mest betydande effekten (p ≤ 0.01) under hela hållbarhetsperioden. Dessutom visade qPCR-analys att Pseudomonas cedrina LMG P-32207 återfanns i högre koncentrationer på sista dagen av hållbarhetstiden jämfört med kontrollen. Vidare visade Illumina MiSeq-sekvensering en lägre relativ förekomst av patogener, särskilt Escherichia coli, i mikrobiotan hos de färdigskurna bladgrönsakerna. Prov av blandad sallad och blandad isbergsmix med tillsatta probiotika visade en högre relativ förekomst av Proteobacteria och Bacteroidetes jämfört med kontrollgruppen. Totalt sett var den mest förekommande familjen Pseudomonadaceae.

α-diversiteten, beräknad med Shannon diversitetsindex, uppvisade variationer endast blandad sallad och blandad isbergsmix inokulerade med probiotika. Högre β-diversitet observerades i alla grupper med blandad salad jämfört med dag 1 (kontroll), som en förskjutning till höger. Detta tyder på att inokulering av probiotika och E. coli har inducerat betydande förändringar i den naturliga mikrobiotan på salladsbladen. Dessa resultat uppmuntrar till användningen av bakteriella antagonister som en del av en global lösning för att minska risken för humana patogener på färdigskurna bladgrönsaker. (Less)
Please use this url to cite or link to this publication:
author
De Mel, Rumathi LU
supervisor
organization
course
KLTM02 20241
year
type
H2 - Master's Degree (Two Years)
subject
keywords
Ready-to-eat, Leafy greens, E. coli, Plant probiotics, Food outbreaks, qPCR, NGS, food engineering, nutrition and food chemistry
language
English
id
9154733
date added to LUP
2024-05-30 13:29:32
date last changed
2024-05-30 13:29:32
@misc{9154733,
  abstract     = {{Ready-to-eat (RTE) leafy greens offer an appealing way to integrate leafy greens into meals. Unfortunately, these leafy greens can
get contaminated with human pathogens such as Salmonella, and Shiga toxin producing Escherichia coli (STEC) at any stage along the
manufacturing chain, potentially leading to serious foodborne diseases. Currently, there is no single step in the production and processing of RTE leafy vegetables that guarantees the elimination of all potential pathogens, leaving the final product susceptible to contamination. To address this challenge, this master’s thesis proposes a novel approach: the direct inoculation of previously evaluated plant probiotics on the day of delivery, known for their antagonistic effects against E. coli. The bacterial levels on the day of delivery and the best-before date were analyzed using viable cell count, quantitative polymerase chain reaction (qPCR), and Next Generation Sequencing (NGS).

The findings from the viable cell count revealed a consistent reduction in non-pathogenic E. coli for all the plant probiotic strains tested. Particularly, Bacillus coagulans LMG P-32205 and Pseudomonas cedrina LMG P-32207 showed the most significant effectiveness (p ≤ 0.01) throughout the shelf-life period. Additionally, qPCR analysis showed that Pseudomonas cedrina LMG P-32207 had higher concentrations on the last day of shelf-life compared to the control. Moreover, Illumina MiSeq sequencing revealed a lower relative abundance of pathogenic genera, especially Escherichia coli, in the microbiota of the leafy greens. The mixed salad and mixed lettuce samples inoculated with probiotics exhibited a higher relative abundance of Proteobacteria and Bacteroidetes compared to the control group. Over all trials, the top family with the highest relative abundance was Pseudomonadaceae. 

The α-diversity exhibited variations only among mixed lettuce and mixed salad samples inoculated with probiotics. Higher β-diversity was observed in all mixed salad groups compared to day 1, as a shift to the right. Indicating that inoculation of probiotics and E. coli has induced substantial changes in the native microbiota of the mixed salad leaves. The effect of probiotic strains varied between different leafy green products, thus no conclusions could be drawn. Nonetheless, these results encourage the use of bacterial antagonists as part of a global solution to reduce the risk of human pathogens on leafy green vegetables.}},
  author       = {{De Mel, Rumathi}},
  language     = {{eng}},
  note         = {{Student Paper}},
  title        = {{Application of Novel Plant Probiotics to Increase the Health Value of Ready-to-Eat Leafy Greens}},
  year         = {{2024}},
}