Effects of Sanitizers on the Control of Alternaria sp. Fungus for ‘Palmer’ Mango Conservation

One of the main problems faced by mango growers in the San Francisco Valley, Brazil, is caused by fungi. Among them, the genus Alternaria, Lasodiploida and Colletotrichum stand out. Sanitization methods have been studied in order to control the proliferation of these microorganisms and increase the shelf life of the fruits. Thus, two methods of sanitization were evaluated: Ozone and chlorine dioxide, in the control of fungi of the genus Alternaria and in the increase of post-harvest quality of Palmer mango fruits. We used a 3 × 5 factorial design with three treatments applied to fruits previously inoculated with fungi, five evaluation periods and five replications, totaling 75 experimental units. The treatments consisted of ozonated water at 3 ppm, chlorine dioxide at 12 ppm, and a control without sanitization. We noted the full development of fungi from the 10th day after contamination, more significantly for the control and to a lesser extent for the treatment with ozone. The methods of conservation with ozone and chlorine dioxide proved efficient in the conservation of fruits. The treatment with chlorine dioxide shows a significant efficiency in the control of penetration of fungi of the genus Alternaria inside the fruits.


Introduction
Among the main mango producers in Brazil, the San Francisco Valley stands out not only in quantity, but also in quality of the fruits produced. It is one of the main centers of agricultural production and guarantees the growth and development of fruit production in the region (Vidal & Ximenes, 2016).
It is known that fungi have a great importance for mango cultivation. In addition to causing losses in post-harvest (fruit rot, shorter shelf life, loss of organoleptic quality, etc.), also cause losses in the field. It is a limiting factor for fruit quality (Oliveira et al., 2016).
In this sense, techniques have been sought to minimize the appearance of microorganisms during the processing and transportation phases, in addition to maintaining the physical and chemical characteristics of mango. According to Mathew et al. (2018), in the absence of practical technologies that provide a necessary step to eliminate pathogens, mango producers rely on the use of disinfectants dissolved in washing water to increase fruit safety. In fact, studies have shown that the incorporation of effective disinfectants into washing water can control pathogens in water and, thus, prevent their internalization (Penteado et al., 2004;Soto et al., 2007;Mathew, 2019). conservation of products with high quality parameters of physical and microbiological attributes, since it has a high oxidation potential and can act both in the air as in water. Aafia et al. (2018) reported that the use of ozone gas increases the storage time of fruits (apple, peach, mango, banana, among others), in addition to promoting the maintenance of the physicochemical parameters of the fruits. Oliveira et al. (2016) verified ozone sanitizing action for the control of Fusarium pallidoroseum associated with refrigeration.
In addition, ozone is highly effective in neutralizing ethylene (Tran et al., 2013), a hormone responsible for the maturation process and the subsequent senescence. It is also a chemically reactive substance, exerting significant antibiotic activity on a variety of deterioration organisms, including fungi and bacteria (Carletti et al., 2013), which makes ozonation an alternative to extending the storage time of mango. Glowacz and Rees (2016) emphasized the need for a prior assessment of quantities and methods of application of ozone before its commercial use. The effects of ozone on fruit physiology and quality may vary according to type, chemical composition, maturation status, and applied dose (time and concentration of sanitizer).
On the other hand, chlorine dioxide (ClO 2 ) stands out as an alternative because, although it is derived from chlorine, it is a stable, non-reactive molecule that generates an insignificant quantity of byproducts and acts as a powerful biocide. According to Conteras-Soto et al. (2018), its use is safe and meets the regulatory standards established for the processing of mango.
Conteras-Soto et al. (2019) reported a faster deteriorating action of chlorine dioxide in mangoes compared to sodium hypochlorite. Praguer et al. (2018) observed that the application of aqueous ClO 2 effectively reduces the counts of natural or inoculated microorganisms.
Given the impact of fungi in mango cultivation, it is necessary to evaluate and compare these two treatment methods, to identify their efficiency in control external and internal microorganisms, as well as to preserve the post-harvest quality of fruits during the storage period.

Method
The experiment was conducted at the Agricultural Products Storage Laboratory (LAPA) of the Federal University of Vale do São Francisco, located in the city of Juazeiro, Bahia, Brazil. We used export-type fruits of the variety 'Palmer.' They were collected in the packing house of the Special Fruit farm, located on the margins of the Juazeiro-Curaçá Highway, km 18, Mandacaru, Juazeiro, Bahia, Brazil.

Experimental Design
The treatments consisted of ozonated water at 3 ppm, chlorine dioxide at 12 ppm, and a control without sanitization. It should be noted that such concentrations were defined according to those used in the region and followed the manufacturer's recommendations. We used a 3 × 5 factorial design with three treatments, five evaluation periods and five replications, totaling 75 experimental units. Each experimental unit represented by a single fruit.

Inoculation
After collection, we selected the fruits and inoculated them with colonies of fungi of the genus Alternaria sp. The fungus inoculation was carried out at the Microbiology Laboratory of the Federal University of San Francisco Valley in fruits previously washed with deionized water and neutral detergent. The isolated colonies were transferred to the region of the fruit pendulum using a sterile swab. Then, the inoculated fruits were placed in container boxes, moistened with cotton, and wrapped in plastic bags for 48 hours to provide favorable conditions of temperature and humidity for the germination of fungi. After this period, the treatments were performed.

Treatments
The fruits were separated into three groups, each with 25 fruits, in order to determine the respective treatments. Part of the fruits was treated with ozone. They were submerged in ozonized water at 3 ppm. Another part was treated with chlorine dioxide, which were similarly submerged in chlorinated water at 12 ppm for 20 minutes for both treatments seeking to simulate the conditions of packing houses in the region. A third part of the fruits was reserved for the control (without treatment).
After treatment, the fruits were placed on a bench under refrigeration at 20±2 °C for twenty days, and periodic evaluations were carried out every five days. The fruits of the control group were also submitted to the same storage condition and evaluated at the same periodicity as the others. jas.ccsenet.

Analys
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Results
We noted t and to a le  In addition post-harve 5 th day of only the tr   Note. * Means followed by the same lowercase letter in the row and uppercase in the column do not differ between the second Tukey test and 5% probability. Tran et al. (2013) observed a L* and b* values decrease in mango fruits skin, treated with ozone. The same treatment reduced the flesh a* value.
Likewise, the results for flesh color are shown in Table 5. The main difference for the flesh color parameter was in relation to the variable a, which determines the variation between green and yellow tones. There was an increase in the shade of yellow and a reduction in green for both treatments. In addition, ozone-treated fruits remained at higher values throughout the evaluation period, showing a probable ripening effect on the color of the flesh. Table 5. Means for the flesh color of fruits inoculated with Alternaria sp. and treated with Ozone (O 3 ), Chlorine Dioxide (ClO 2 ) and without treatment (Control) during storage. Reflectance values indicate luminance index (L), a* (index ranging from pure green, -100, to pure yellow, 100), and b* (index ranging from pure blue, -100, to pure red, 100) Note. * Means followed by the same lowercase letter in the row and uppercase in the column do not differ according to the Tukey test at 5% probability. ns Not significant for the Tukey test at 5% probability.
There was an increase in the yellow shade and a decrease in green shade for both treatments. In addition, ozone-treated fruits remained at higher values than chlorine dioxide-treated fruits throughout the evaluation period, showing a probable ripening effect on flesh color. Mathew et al. (2019) found that prolonged washing

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