3.2.1. Hazard identification

Microbiological hazard was designated for six products (Table 1) with high risk of contamination with pathogens. The food safety scheme was developed to introduce minimum regulatory requirements for businesses producing high-risk plant products, and to implement control measures to minimize the risks from the microbiological hazards associated with these products.

Table 1. Microbiological hazards associated with plant products

Fresh cut vegetablesFresh cut fruits and vegetables are raw agricultural products that have been processed by means of washing, trimming, cutting or slicing to be made ready for consumption. Contamination of vegetables may occur during growth, harvest or processing. Under certain conditions microorganisms can also become internalized within the vegetables. Conditions that promote internalisation of microorganisms include damage to the natural structure (e.g. punctures, stem scars, cuts, and splits) and placing warm produce into cooler, contaminated wash water.These foods have a high potential risk due to the contamination with pathogenic E. coli, Salmonella serovars and L. monocytogenes. The actual process of cutting and/or removing the protective outer surfaces of the plants may increase the potential for pathogenic bacteria to survive and/or grow. Many vegetable products do not undergo a kill step that will completely eliminate pathogens; however, measures such as sanitising washes may be used to reduce microbial contamination with pathogens.

Many fresh cut vegetables are packaged using MAP and refrigerated to extend the shelf life. This form of processing may lead to an increased risk from pathogens such as L. monocytogenes and psychrotrophic strains of C. botulinum by enhancing the conditions for their survival and allowing additional time for growth. MAP products may become fully anaerobic if the plant tissue is actively respiring and uses up all the oxygen. As any competition from aerobic spoilage organisms is inhibited, this may increase the opportunity for anaerobic or facultative anaerobic pathogens to grow.

Fresh cut fruit

Fresh fruit are normally perceived as low risk foods, as they tend to have a thicker protective skin than most vegetables and most are harvested from trees or bushes. The notable exceptions are melons and strawberries, which are considered higher risk because they grow close to the ground and their surfaces may become contaminated with soil.

Contamination of fruit may occur at any point from growing (soil, fertilisation, irrigation water, and animal/bird waste), through harvesting and processing (including washing), to distribution, marketing, and consumption. Many microbial pathogens cannot survive or grow on most fruit due to the low pH environment. However, melons and strawberries have relatively high pH, which makes them more likely to be a food safety hazard. In addition, the skin of rockmelon tends to be porous, which may allow the penetration of pathogens and agricultural chemicals into the fruit. Melons are often dipped in a sanitizing solution after harvest (FSA, 2000a).

Fresh cut fruits may be value added by peeling, chopping, slicing, and packaging. Many fresh cut fruit are packaged using MAP and refrigerated to extend the shelf life. With additional time, this can lead to an increased risk from pathogens that are adapted to the acidic environment of fruit and are able to survive and grow in these foods.

A range of bacterial (E. coli, Salmonella serovars, and L. monocytogenes) and viral pathogens, and enteric parasites(Cryptosporidium parvum) have been identified as being of concern in fresh cut fruit. The actual process of cutting and/or removing protective outer surfaces of the fruit may increase the potential for pathogens to survive and/or grow. Fruit pickers and handlers with infections are also an important source of contamination.

Vegetables in oil

This product category includes a diverse range of vegetables and mixtures of vegetables and herbs that may be used fresh, dried, roasted or acidified. Oil is added to exclude air, which prevents discoloration of the vegetable. Although immersion of vegetables in oil reduces the available oxygen in the container, contrary to popular belief, it does not preserve the food. Some pathogenic bacteria are able to survive and grow in reduced levels of oxygen and even under anaerobic conditions.C. botulinum is the main pathogen of concern because of its ability to grow anaerobically and it has been linked to outbreaks of illness from the consumption of vegetables in oil. Vegetables may be contaminated by C. botulinum spores, which are frequently associated with soil, and processes such as cooking and acidification may be insufficient to inactivate the spores or prevent their germination and growth. Acidification to below pH 4.6 should prevent outgrowth; however, more than one hurdle is recommended as a safeguard.

Seed sprouts

Seed sprouts are usually consumed raw and include alfalfa, mung bean, chickpeas, cress, fenugreek, soy, lentils, sunflower, onion, and radish. Seeds for sprouting generally do not receive any special treatment during harvesting and transport, and so may become contaminated with pathogenic organisms in the field or during harvesting, handling, processing, and distribution. While some bean sprouts may be cooked prior to consumption, many others are consumed raw, for instance with salads.

The microbiological pathogens frequently found associated with seeds for sprouting include B. cereus, Salmonella serovars, and E. coli and these organisms have also been implicated in foodborne illness outbreaks. The rough surfaces and cracks in the seed may protect the pathogens from microbiocidal treatments and may make detection during routine analysis difficult. High levels of organic matter also reduce the effectiveness of chlorine treatments during seed washing and seed sprouting. Bacterial populations of 10²–10⁷ cfu/g have been observed on seeds for sprouting, and this natural population can rapidly increase under the high moisture and moderate temperature conditions used in sprouting facilities. Microorganisms may also become internalized in the sprout during growth, so sanitising wash treatments of sprouted seeds are not likely to be effective (FSA, 2000a).

Unpasteurized fruit juice

Fruit juices are made by extracting fruit (citrus juices) or by macerating fruit (grape, cherry, berry, apple juice, etc). This may be followed by clarification, filtration, pasteurisation, and/or other processes to reduce the microbial load. In recent years, there has been a trend to produce ‘natural’ fruit juices containing no preservatives and receiving little or no heat treatment.

Any microorganisms present on the surface of fruit may potentially contaminate the juice made from it. Bacterial pathogens are unlikely to grow due to the low pH but some bacteria, viruses or protozoa may be able to survive for extended periods. The length of time the microorganism may survive is dependent on the pH of the juice, the storage temperature, and the physiological state of the microorganism. Some Salmonella serovars and strains of pathogenic E. coli are known to be particularly acid tolerant, with this response thought to be activated by previous exposure to sub-lethal pH values.

Apple and pear juice can become contaminated by the mycotoxin patulin, which is produced by several Penicillium and Aspergillus species. P. expansum appears to be the main patulin producer in apples and apple products. Since patulin is concentrated in the rotting tissue of fruit, it is a good indicator of the quality of fruit used to make the juice.

The acidic nature of fruit juices makes them corrosive to metals. To avoid potential chemical contamination, only stainless steel or corrosion resistant vessels should be used to store these products. Other metals such as copper can leach into the beverage during storage.