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Microbiological quality and occurrence of antibiotic resistant bacteria in ready-to-eat salad

Lupan, Tamara LU (2016) KLGM01 20161
Food Technology and Nutrition (M.Sc.)
Abstract
An increase in demand for fresh vegetables resulted in an increased production of minimally processed, ready-to-eat salad in Sweden. That also brought new food safety challenges that are yet to be addressed.
To assess whether ready-to-eat leafy green vegetables present a threat in terms food borne outbreaks, aerobic bacteria, as well as bacteria belonging to the Enterobacteriaceae family were recovered, using selective media, from 3 different sets (n=18) of ready-to-eat rocket salad.
Bacterial investigation showed that most bacteria retrieved from ready-to-eat rocket salad belongs to the Pseudomonadaceae family, which are typical spoilage bacteria commonly associated with vegetables. No food-borne pathogens (e.g. Clostridium botulinum,... (More)
An increase in demand for fresh vegetables resulted in an increased production of minimally processed, ready-to-eat salad in Sweden. That also brought new food safety challenges that are yet to be addressed.
To assess whether ready-to-eat leafy green vegetables present a threat in terms food borne outbreaks, aerobic bacteria, as well as bacteria belonging to the Enterobacteriaceae family were recovered, using selective media, from 3 different sets (n=18) of ready-to-eat rocket salad.
Bacterial investigation showed that most bacteria retrieved from ready-to-eat rocket salad belongs to the Pseudomonadaceae family, which are typical spoilage bacteria commonly associated with vegetables. No food-borne pathogens (e.g. Clostridium botulinum, Escherichia coli O157:H7, Salmonella spp., Shigella spp., Listeria monocytogenes) were isolated from any of three sets of rocket salad.
Following the assumption that microbiological quality of the salad could change during the storage period, as well as a result of salad bags being opened, sealed, stored and opened again in the household, the total aerobic count as well as total amount of Enterobacteriaceae were assessed every day before the best-before date.
Following the NSW food Authority guidance on the microbiological status of ready-to-eat food, it can be confirmed, that each of three sets of salad were from the first day after packaging, unsatisfactory in regards to total aerobic count, showing values higher than 5 log CFU/g.
The bacterial investigation also concluded that opening the bags and storing them sealed in the household will produce little, if any effect on the microbiological quality and will not challenge the validity of the expiration dates.
To asses weather ready-to-eat rocket salad available for sale in Sweden, could be a possible reservoir of antibiotic resistance, the isolated bacteria from each bag of salad were tested for susceptibility to eight antibiotics, representative of the six classes of antibiotic compounds commonly used in clinical settings in Sweden. The cases of possible acquired antibiotic resistance were rare, however, the bacteria suspected to be immune to drug action should be subject for further investigations aimed to discover the mechanism of such resistance. (Less)
Popular Abstract
The increasing demand for fresh fruits and vegetables resulted in a rising market of ready-toeat salad in Sweden. Pre-packed salad can be found in almost every grocery store and is served from fast food chains and restaurants to hospitals and school canteens. This salad is fresh, previously washed by the manufacturer, dried and afterwards packed in bags with modified atmosphere. Being a ready-to-eat product, it does not require any treatment, like washing or cooking before being served to table.
Consumers do not associate vegetables with any health risks and assume that salad is a safe product. However, according to the European Food Safety Authority there is an increase in numbers of food-borne outbreaks associated with food of... (More)
The increasing demand for fresh fruits and vegetables resulted in a rising market of ready-toeat salad in Sweden. Pre-packed salad can be found in almost every grocery store and is served from fast food chains and restaurants to hospitals and school canteens. This salad is fresh, previously washed by the manufacturer, dried and afterwards packed in bags with modified atmosphere. Being a ready-to-eat product, it does not require any treatment, like washing or cooking before being served to table.
Consumers do not associate vegetables with any health risks and assume that salad is a safe product. However, according to the European Food Safety Authority there is an increase in numbers of food-borne outbreaks associated with food of non-animal origin, they being responsible for a quarter of food illness cases and a half from the total number of deaths.
The food-borne outbreaks related to ready-to-eat salad are mainly caused by bacteria and viruses that contaminate the product somewhere in the production chain, i.e. via contaminated water used during irrigation; dirty equipment in the packaging facility or an infected food worker. The risk is further aggravated because washing the salad at home will not significantly improve the situation.
In the frame of this project three different types of rocket salad were examined for total number of bacteria as well as for the presence of pathogen bacteria. The investigation showed that most bacteria present in ready-to-eat salad were typical spoilage bacteria commonly associated with vegetables and no food-borne pathogens were isolated from any of three sets of rocket salad.
Following the guidance on the microbiological status of ready-to-eat food, it can be confirmed, that each of three sets of salad were from the first day of purchase unsatisfactory high in total bacterial content and contained opportunistic pathogens. Taking in account that salad can be consumed by everyone, including children, pregnant women, elderly and immunocompromised people, it was suggested that producer should place additional information on the packaging preventing some groups of population from eating the product raw.
The second part of this project was directed to asses weather ready-to-eat rocket salad sold in Sweden could be a possible reservoir of antibiotic resistant bacteria. During the study,bacteria from each bag of salad were tested for susceptibility to eight antibiotics commonly used in Sweden. The cases of acquired antibiotic resistance were rare, however, some bacteria were immune to the drugs. These isolates should be directed for further investigations in order to understand if they present any health threat. (Less)
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author
Lupan, Tamara LU
supervisor
organization
course
KLGM01 20161
year
type
H2 - Master's Degree (Two Years)
subject
keywords
food technology, livsmedelsteknologi
language
English
id
8886496
date added to LUP
2016-08-03 10:35:32
date last changed
2016-08-03 10:35:32
@misc{8886496,
  abstract     = {An increase in demand for fresh vegetables resulted in an increased production of minimally processed, ready-to-eat salad in Sweden. That also brought new food safety challenges that are yet to be addressed. 
To assess whether ready-to-eat leafy green vegetables present a threat in terms food borne outbreaks, aerobic bacteria, as well as bacteria belonging to the Enterobacteriaceae family were recovered, using selective media, from 3 different sets (n=18) of ready-to-eat rocket salad. 
Bacterial investigation showed that most bacteria retrieved from ready-to-eat rocket salad belongs to the Pseudomonadaceae family, which are typical spoilage bacteria commonly associated with vegetables. No food-borne pathogens (e.g. Clostridium botulinum, Escherichia coli O157:H7, Salmonella spp., Shigella spp., Listeria monocytogenes) were isolated from any of three sets of rocket salad.
Following the assumption that microbiological quality of the salad could change during the storage period, as well as a result of salad bags being opened, sealed, stored and opened again in the household, the total aerobic count as well as total amount of Enterobacteriaceae were assessed every day before the best-before date.
Following the NSW food Authority guidance on the microbiological status of ready-to-eat food, it can be confirmed, that each of three sets of salad were from the first day after packaging, unsatisfactory in regards to total aerobic count, showing values higher than 5 log CFU/g.
The bacterial investigation also concluded that opening the bags and storing them sealed in the household will produce little, if any effect on the microbiological quality and will not challenge the validity of the expiration dates.
To asses weather ready-to-eat rocket salad available for sale in Sweden, could be a possible reservoir of antibiotic resistance, the isolated bacteria from each bag of salad were tested for susceptibility to eight antibiotics, representative of the six classes of antibiotic compounds commonly used in clinical settings in Sweden. The cases of possible acquired antibiotic resistance were rare, however, the bacteria suspected to be immune to drug action should be subject for further investigations aimed to discover the mechanism of such resistance.},
  author       = {Lupan, Tamara},
  keyword      = {food technology,livsmedelsteknologi},
  language     = {eng},
  note         = {Student Paper},
  title        = {Microbiological quality and occurrence of antibiotic resistant bacteria in ready-to-eat salad},
  year         = {2016},
}