ready-to-eat-salads-may-harbour-disease-causing-bacteria

Research indicates that ready-to-eat salads that have been sanitised may harbour disease-causing bacteria.

 

A review article featured in the journal Foods outlines a study that explores existing research on minimally processed vegetables (MPVs), with an emphasis on the Brazilian market.

 

The study presents data on hygiene indicators and pathogenic microorganisms, particularly focusing on Escherichia coli (the primary marker of faecal contamination), Salmonella spp., and Listeria monocytogenes, with prevalence rates varying between 0.7% to 100%, 0.6% to 26.7%, and 0.2% to 33.3% respectively.

 

Additionally, the article examines incidences of food-borne illnesses linked to the consumption of fresh vegetables in Brazil spanning from 2000 to 2021. "While it is unclear if these vegetables were consumed as fresh produce or as MPVs, the data underscores the necessity for control measures to ensure the quality and safety of products for consumers," note the authors.

 

Consistent vegetable consumption is vital for human nutrition due to the vitamins, minerals, and fibre present in them. "An increasing number of people are seeking healthy food that can be quickly prepared due to the pressures and pace of everyday life. This demand has led to a global increase in the need for MPVs. Conversely, fresh vegetables and MPVs are often linked to food-borne illnesses. This connection raises concerns. Although MPVs are subject to sanitisation and disinfection, evidence suggests that this process may have its shortcomings, endangering consumer health. Strict regulations are essential to prevent errors and cross-contamination," stated Daniele Maffei, the last author of the article. She is a professor in the Department of Agroindustry, Food and Nutrition at the University of São Paulo’s Luiz de Queiroz College of Agriculture (ESALQ-USP) in Brazil.

 

She is additionally associated with the Food Research Centre (FoRC), which is one of the Research, Innovation, and Dissemination Centers (RIDCs) supported by FAPESP.

 

MPVs are sliced, sanitised, and packaged in closed containers labelled as “ready to eat.” Consumers purchase these to prepare meals more efficiently and minimise waste, as the contents of each package usually correspond to a single serving. Due to their common consumption in a raw state, they are typically washed in chlorinated water to eliminate harmful microorganisms.

 

“The producer must ensure that the marketed products meet microbiological quality and safety standards, necessitating the adoption of control measures throughout the processing stages. Even though washing them at home might seem unnecessary, some consumers may opt to do so for added safety,” added Maffei.

 

As mentioned in the article, minimal processing refers to one or more methods used to transform plant-based foods into ready-to-eat (RTE) or ready-to-cook (RTC) items with an extended shelf life, while keeping the nutritional and sensory quality of fresh vegetables intact.

 

The shelf life can range from a few days to two weeks, influenced by factors such as the initial quality of the vegetables, the processing techniques used, packaging, storage conditions, and the potential presence of pathogenic or spoilage microorganisms.

 

Proper minimal processing, in line with best practices, helps delay nutrient degradation, avoids unwanted changes in texture, colour, flavour, and aroma, and inhibits microbial spoilage. A wide array of vegetables can undergo minimal processing, including leafy greens like arugula, lettuce, and spinach; cruciferous vegetables such as broccoli and cauliflower; root vegetables like carrots and beetroot; as well as cucumbers, among others.

 

In Brazil, the MPV market began to develop in the mid-1970s alongside the rise of fast-food chains, and its availability in retail stores is consistently increasing, especially in major urban areas, even though processing renders them about twice as costly as fresh vegetables.

 

“The expansion of the MPV market is a growing trend in Brazil, and it is crucial to establish legislation to regulate the processing and distribution of these products,” stated Maffei, who has been focusing on this field since 2012 and has authored multiple papers regarding the microbiological risks associated with MPVs in journals like Letters in Applied Microbiology, Food Research International, and the Journal of the Science of Food and Agriculture.