**3.3. Durability and growth of pathogens in the skin and flesh of melon**

Pathogenic bacteria in melon skin survive for a long time and multiply [2]. The number of E. coli O157: H7 bacteria increases by more than 100 times in one square centimeter of melon skin and a temperature of 25°C in 4 days [4]. The large, rough skin of a melon provides a multiplication space for germs. Salmonella formed a biofilm in the skin of the cantaloupe melon at 20°C after 2 h, and the bacterium increased by 200% at room temperature for 24 h [2]. **Table 1** shows the amount and timing of the multiplication of Listeria and Salmonella bacteria in melons and watermelons at different temperatures. It is observed that the proliferation of bacteria has increased in proportion to the temperature; by increasing the temperature from 10 to 30°C, the largest number of these bacteria is produced in the shortest time.

Ukuku et al. [19], in their study, found that the number of aerobic bacteria in the flesh of the cantaloupe was higher than the number of these bacteria in the flesh of the honeydew melon. The microbes in the skin are transferred to the melon flesh during slice cutting [19, 21]. Due to the low acidity of the melon flesh, the bacteria survive and multiply rapidly. Listeria and Salmonella bacteria started multiplication at room temperature after 2 h [19], and the researchers also reported that, as a general rule, the higher the storage temperature, the shorter the bacterial division.

Studies by Li et al. [12] show that Salmonella and E. coli O157: H7 did not grow in the skin of cantaloupe, honeydew, and watermelon at 4°C, but at 15°C and higher. The proliferation of these bacteria began rapidly. E. coli O157: H7 began to multiply more


#### **Table 1.**

*Lag phases and generation times of Listeria and Salmonella bacteria in watermelon and melon [4].*

*Safety of Food throughout the Supply Chain DOI: http://dx.doi.org/10.5772/intechopen.105670*

rapidly than Salmonella at room temperature (23–25°C). Contrary to expectations, despite the different pH of watermelon (pH 5.1–5.6) and melon (pH 6.1–6.6), the same proliferation and growth of bacteria were observed in these two fruits. However, the growth rate of Salmonella and E. coli in honeydew melon was slightly lower than in other types of melons [19].

If the peeled melon is stored for a long time without refrigeration, the risk of germs growing in it increases [19]. Storing melon at 22°C caused severe growth of Salmonella. The number of Salmonella reached 1.3 cfu/g bacteria after 5 h and 0.2 cfu/g in a watermelon after 5 h [19]. In melons that were not refrigerated, the number of Listeria increased at 20°C compared to those refrigerated at 5°C. The researchers concluded that storing melon slices under normal room conditions, even for a limited number of hours, could increase Listeria bacteria [21].

According to scientific studies, washing with water does not significantly reduce the number of germs in melon skin [19]. Washing the cantaloupe melon for 3 minutes did not reduce the number of Salmonella and E. coli [2]. The researchers attributed the large surface area of the melon to the absorption, preservation, and contamination of the melon. To clean the surface of the melon, it is a good way to use a brush. A study by Parnell et al. [15] showed that brushing melon skin for 60 s reduced the number of Salmonella quadruples, and large-skinned melons reduced the number of bacteria by 1.6 times. After the melon was disinfected with 2.5% hydrogen peroxide, the number of microbes was reduced in it, except that Listeria bacteria is still observed in the melon flesh after spraying [19].

### **4. Conclusion and recommendations**

Fruits and vegetables have caused diseases in the most developed countries. In the past, many cases of disease outbreaks have been reported after eating melons, some of which were very serious. For example, 147 people became infected with L. monocytogenes in the United States in 2011 after eating melons, including 33 deaths and a pregnant woman who was unable to give birth as a result of the disease. To reduce diseases, the following orders should be considered along the production chain to consume vegetables, fruits, and especially melon fruits.

During production, use plastic and/or organic mulch to reduce contamination, or place fruits in plastic bags. Another way to reduce contamination is to roll over fruits consistently. This is done by the hands and the hands should be clean, otherwise, it will cause more contamination [10, 21].

Studies show that peeling melon before eating significantly reduces germs [21]. In the United States, Canada, Australia, and New Zealand, the melon is cooled immediately after slicing as a precaution, and discarding melon slices that have been left in normal air for more than 2 h has been ordered [20, 22]. Therefore, observing these measures is recommended.

It is recommended that restaurants, wholesalers, and families cut and consume melon little by little, and melon slices should be consumed in less than 2 h. It is recommended that pregnant women and other vulnerable people, such as young children, adults, and the sick, refrain from eating melon that has been stored outdoors for several hours.

Hygiene measures should be taken when cutting the melon, such as slicing should be done in a wider and clean place with clean hands, and a clean knife and a clean container should be used to prevent contamination of the melon flesh. It is very

important to consider home hygiene and personal hygiene because the infection dose of Listeria bacterium is very low (100 colonies). In addition to maintaining good hygiene, it prevents the melon from becoming contaminated with other germs, such as campylobacter, type A jaundice, and norovirus.

To prevent contamination and disease, retailers, restaurants, cafeterias, and others should cut a small amount of melon and consume it in less than 2 h.

It is recommended that the melon husk be eaten immediately or put in the refrigerator immediately. The suitable temperature for the refrigeration of melon cut is 4-6 Degree Celsius as it minimizes the multiplication of germs. Pregnant women and people with weak immune systems, such as children, the elderly, and the sick, should refrain from eating peeled melons that have been left in the room for more than 2 h.

In the field of exports, since the issue of food safety is more important today than food security, producers and exporters must consider hygiene throughout the stages of the supply chain, because competition and continuity in international markets are possible only if the fruits are healthy and free of pathogens and dangerous elements, such as Argentum, lead, and arsenic; also, free of residues of agricultural chemicals. Therefore, exported fruits must comply with the standards of the global quality control organizations, especially the food standards of the Codex Alimentarius Commission, and HACCP.
