How safe is your salad?

Posted: 31 August 2023 | | No comments yet

A recent review of research on minimally processed vegetables has highlighted cases of unsatisfactory microbiological safety.


A recent study carried out by the University of São Paulo, has flagged concerns regarding minimally processed vegetables (MPVs), with a specific focus on the Brazilian market.

Published in the journal Foods, the data is presented on hygiene indicators and pathogenic microorganisms, especially Escherichia coli (the main indicator of fecal contamination), Salmonella spp., and Listeria monocytogenes, with prevalence rates ranging from 0.7 percent to 100 percent, 0.6 percent to 26.7 percent, and 0.2 percent to 33.3 percent respectively.

In addition, the article outlines outbreaks of food-borne disease (associated with consumption of fresh vegetables in Brazil between 2000 and 2021.

“Although there is no information about whether these vegetables were consumed as fresh vegetables or MPVs, the data highlights the need for control measures to guarantee products with quality and safety for consumers,” the study authors explained.

“More and more people want healthy food that can be prepared in a short time because of the hurry and stress of everyday life. This trend has led to rising global demand for MPVs,” said Daniele Maffei, 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 also affiliated with the Food Research Center (FoRC), one of the Research, Innovation and Dissemination Centers (RIDCs) funded by FAPESP.

“On the other hand, fresh vegetables and MPVs are frequently associated with food-borne diseases. The link is a matter of concern. MPVs are sanitized and disinfected, but studies show this process can be flawed, putting consumer health in danger. Rigorous controls are needed to avoid flaws and cross-contamination.”

The study authors have pointed out that MPVs are cut, sanitised and sold in closed packaging with labelling that suggests they are “ready to eat”. Consumers buy them to prepare meals more quickly and reduce waste, given that the entire contents of each package typically correspond to a single portion. Because they are usually eaten raw, they are normally washed in chlorinated water to remove pathological microorganisms.

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“The producer is responsible for marketing products with microbiological quality and safety, which require the implementation of control measures throughout processing. Although washing them at home may be considered unnecessary, some consumers can choose to do so for extra safety,” said Maffei.

According to the article, minimal processing means the use of one or more methods to transform plant-based foods into ready-to-eat (RTE) or ready-to-cook (RTC) products with an extended shelf life while maintaining the same nutritional and organoleptic (sensory) quality of fresh vegetables. The length of shelf life on food ranges from a few days to two weeks depending on several factors, including the quality of the vegetables when fresh, the processing method, packaging, storage conditions, and the possible presence of pathogenic or spoilage microorganisms.

However, the study notes that minimal processing performed in accordance with best practices delays nutrient loss, avoids undesirable changes in texture, colour, flavour, and aroma, and prevents microbial spoilage. A wide variety of vegetables can be minimally processed, including leafy greens, such as arugula, lettuce and spinach; cruciferous vegetables, such as broccoli and cauliflower; root vegetables, such as carrots and beetroot; and cucumbers, among others.

In Brazil, the market for MPVs emerged in the mid-1970s with the expansion of fast-food chains, and the presence of MPVs in retail stores is steadily growing, particularly in large urban centres, even though processing makes them about twice as expensive as fresh vegetables, according to the study.

“Growth of the market for MPVs is a trend in Brazil, and it’s imperative to bring in legislation to regulate the processing and sale of these products,” concluded Maffei.