CHAPTER 1 INTRODUCTION
The importance of fresh fruits and vegetables as the primary natural source of vitamin and fiber for humans cannot be overemphasized. However, fruits and vegetables are produced, marketed, and consumed with little or no sanitary measures (Fig. 1) in developing nations (Eni, Oluwawemitan, & Solomon, 2010). The use of manure that has not been composted and sewage water that has not been treated as fertilizers further increases the possibility of microbial contamination (Eni et al., 2010) and this practice has led to several outbreaks resulting from the consumption of fresh produce in Europe and the United States (Soon, Manning, Davies, & Baines, 2012). Nonetheless, fresh fruits and vegetables cannot be replaced by any other food source; hence there is a need to make sure that they are safe before consumption. To this end, many decontamination techniques have been devised to counter the effect of harmful microbes. However, the efficacy of many decontamination methods in commercial settings are still doubted (Fonseca & Ravishankar, 2007).
Figure 1 A typical African fruit and vegetable market in Kenya (credit: alamy)
Fresh fruits and vegetables
Being recognized as one of the most important source of vitamins, nutrients, and fiber for humans has made fresh produce popular in the world. The world has seen a large increase in the production of fruits and vegetables by 94% between 1980 and 2004 (Fig. 2) (Olaimat & Holley, 2012). The United States’ importation of fresh produce doubled to 12.7 billion dollars from 1994 to 2004 (Aruscavage, Lee, Miller, & LeJeune, 2006), and the daily sales of fresh produce reached 6 million packages in 2005 (Jongen, 2005) as cited in Olaimat & Holley, 2012.
This increase in the level of consumption of fruits and vegetables and the surge of various locally produced and imported fruits and vegetables in all seasons might be attributed to peoples’ growing attention to staying healthy and eating right as well as the convenience provided from prepared products (Warriner, Huber, Namvar, Fan, &
Dunfield, 2009). The world’s fruits and vegetable consumption has increased at an annual average of 4.5% from 1990 to 2004, and in the United States alone, the annual consumption of fruits and vegetables between 1997-1999 increased by 25% relative to the years 1977-1979 (Olaimat & Holley, 2012).
People became more interested in the consumption of fresh fruits and vegetables after the release of information highlighting the health benefits of the consumption of fruits and vegetable (DuPont, 2007). For example, in a report by the World Health
Figure 2 Global production of fruits and vegetables from 1982 to 2004 (sourced from EU, 2007).
Organization (WHO), it’s recommends at least 400 grams of fruits and vegetables are eaten in a day for protection against the risk of non-communicable diseases and improvement of overall health (Soon et al., 2012). Additionally, Healthy People, a
U.S. government program, aims at increasing the intake of fruits and vegetables for people aged 2 years and above to two daily servings of fruits and three daily servings of vegetables to 75% and 50%, respectively (DuPont, 2007).
However, this increase in consumption of fruits and vegetables has been followed by an increase in outbreaks of foodborne illnesses linked to the consumption of fresh fruits and vegetables (Warriner et al., 2009). This increase in the consumption of fruits and vegetables was associated with change of personal dietary habits increased availability of fresh produce with some coming from sources having uncertain sanitary practices (Beuchat, 2002). The use of manure that has not been composted, untreated sewage, irrigation water contaminated by pathogens, increased contact between livestock and fresh produce due to their proximity to areas of high produce production, and also increased number of immunocompromised consumers further worsens the situation (Beuchat, 2002). The most reported pathogens associated with foodborne illnesses related to the consumption of fresh produce are Salmonella sp. and Escherichia coli O157:H7 (Warriner et al., 2009).
Fresh fruits and vegetables that receive little or no processing and thus do not undergo effective microbial decontamination and elimination steps usually carry microbes, some of which could be harmful to human health (Harris et al., 2003). Contamination can occur at any stage from the farm to the consumer due to environmental, human, or animal contact during production, storage harvesting, and transportation (FDA, 2014).
In less developed countries such as Nigeria, contamination is mostly due to the use of manure and untreated water as fertilizers in the production of fruits and vegetables (Eni et al., 2010). A high microbial contamination was observed in fruits and vegetables in a study conducted in Sango Ota, Ogun state, Nigeria. The high contamination was suggested to be due to cross-contamination during the storage
time of the fruits and vegetables, during washing in markets where many fruits and vegetables are washed using the same water that was earlier used, and during transportation or handling by vendors (Eni et al., 2010).
In another study in Sokoto State, northwestern Nigeria, eight pathogenic microbes were found in tomatoes sold in markets. The microbes isolated were Aspergillus niger, A. ochraceous, A. flavus, A. fumigatus, Penicillium citrinum, Helminthosporim fulvum, Curvularia lunata, and Sclerotium rolfsii (Muhammad, Shehu, & Amusa, 2004). The reality that a significant portion of the Nigerian population are low- income earners and frequently consume rotten tomatoes further aggravates the situation (Muhammad et al., 2004).
