Assessment of the Physical-Chemical Properties of Stored Corn Submitted to a Treatment with Dusted Seeds of Moringa Oleifera Lam

The employment of phytosanitary agents applied trough seeds is common practice in corn crops. However, increasing concerns over the environment and living beings’ safety bring to light a need for technologies, which aim at reducing the risks originated from manipulation of phyto protectors, which is one of Moringa oleifera Lam. main roles. It has been attempted to, therefore, evaluate the physiologic quality of corn seeds submitted to treatments with Moringa oleifera Lam. dusted seeds, with five repetitions, and doses equal to zero; 0,5; 1.0; 2.0 and 4.0 grams of moringa seed dust for each 10 grains of corn, with contact times of zero; 2; 4; 6 and 24 hours, 30 days (720 hours) and 6 months (4,320 hours). The measured parameters were germination test, humidity, volumetric weight, weight of 1,000 grains, ashes and acidity index. The results show that the physiologic quality of the corn seeds submitted to the application of Moringa oleifera Lam. suffered no impairment, turning its application technically viable for up to six months of storage.


Introduction
Brazil is a country, which presents a high potential for grain production that is yet to be fully explored. Corn is a widespread crop, for it adapts to the most different ecosystems. It covers, in the national territory, over 12 million hectares with an annual production of nearly 40 million tons of corn. Although it is a crop appropriate to the employment of high technology with the potential of producing over 16 t/ha, low cost technologies prevail in the current scenario, which has kept the average national productivity around 2,5 t/ha [1]. Alongside the effort of increasing productivity, there necessarily must be an improvement in harvesting techniques and grain storage conditions. A positive trait of the grains is the possibility of being stored for a large amount of time with no significant losses in quality. However, prolonged storage is only feasible when proper measures of harvest, cleaning, drying, insect combat and fungi prevention are taken [2]. The preservation of seed quality during the storage period is one of the most important steps in the process of production and commercialization. The efforts under taken in production steps could turn ineffective should seed quality preservation fail, at least until a new sowing season starts [3]. [4] have concluded that the speed of deterioration of corn seeds during storage is mainly influenced by the starting physiologic quality of the seeds, as well as relative humidity and temperature of the environment.
The employment of phytosanitary products through seed application is common practice in corn crops, however, increasing concerns over environment and safety during the manipulation process led to a surge in demands for application technologies, which reduce risks without compromising seed quality [5,6]. it is also known as "drumstick" for the form of its fruits which is a staple food in countries such as India and Africa [7,8]. The paste made of raw seeds is antibacterial; active substances are found in seed cotyledons, possessing three main components: "welloil", flocculator, both polypeptides (proteins), substances not yet clearly identified, and antimicrobial substance 4 -L -Rhamnosyl -oxybenzyl -isothio -cyanate (RI), according to [9,10]. The great concern with the environment has led numerous researchers to seek viable, effective and safe alternatives for the use of products applied during the corn grain storage process that allow commercialization, without quality. The purpose of the present study was to test the possibility of increasing corn grains storage times when treating them with dusted seeds of Moringa oleifera Lam. by preserving their physiologic quality.

Materials and Methods
The present study was conducted in the Laboratory of Analytic Chemistry of the Environmental Engineering department of the Catholic University of Pernambuco, Recife, Pernambuco, Brazil.

Calculation of the Concentrations of Moringa Seed Dust and Contact Time with the Corn
The treatments were performed with five repetitions, in doses  The results shown in Figure 1 indicate that the humidity content of the samples analyzed in this study has ranged from 2.09 (0.5g Moringa/4h Contact) to 13.45% (1.0g Moringa/24h Contact), which are all below the maximum value allowed by the Ministry of Agriculture (14.5%) according to the regulation n. 845 from 1976 [13]. Only the treatment of 1.0g Moringa/0h Contact presented a value above the permitted (17.71%). Such contents of humidity, found in the corn samples studied, could have contributed to their level and frequency of contamination (data not presented).

Humidity
In samples of stored corn, the absence of contamination has been attributed to humidity levels between 13 and 13.5% [14]. The development of fungi in corn with humidity content of 14% after storage periods of up to 62 days [15]. In this study, the longest period of storage was 6 months (4,320 hours) in the treatment of 4.0g Moringa/6 months Contact.

Germination Test
The percentage results of the germination of seeds from the hybrid BRS -Gorutuba, both treated and untreated with moringa, it could be verified that seeds subject to phytosanitary treatment generated normal sprouts, which indicates a non-phytotoxic effect of the products over the seeds. It must be highlighted that the seeds presented a good initial quality and the reduction of germination on the treated seeds was only 1%, which validates the possibility of employing moringa to protect the seeds. As stated by [16], the storage potential of seeds is directly related to their initial quality, because a lot of high quality could be stored for longer periods of time, in uncontrolled conditions than one which its initial quality is compromised. Hence the positive results presented with the moringa treatments. It has also been verified that, even with six months of storage, the seeds still kept a percentage of germination above the established minimum for commercialization, which is 85% [17].

Volumetric Weight/ Weight of 1,000 grains
Regarding the volumetric weight of the corn seeds, it was found, on average, a value of 78.95g/ml and an average weight of a thousand grains of 355.39g. Such data corroborate the ones found in germination and humidity, since it could be related to a greater robustness of the seeds employed in the experiment, which is in accordance to what was observed by [18][19][20]. The results show, not only in volumetric weight but also in the weight of a thousand seeds, that the seeds presented satisfactory criteria in terms of quality, which, in a way, agrees with [18]. Such verification was key, bearing in mind the goal of the study. It must be stressed out, however, due to the novel aspect of the research, further studies on the subject are needed.

Mineral Material or Ashes
The corn seeds presented, in the verification of ash content Therefore, the ash content found in all treatments was above permitted. Even though it was not affected by the presence of the moringa, ash content increased in function of increasing levels of moringa/contact, because, as stated by [21], the availability of minerals influences the mineral composition of the corn grains.

Acidity Index
In Figure 3 are presented the acidity index values of corn after the different treatments employed. There have been found, on average, values of 0.35% (0g M/6monthsContact) up to 5.83% (4.0gM/6monthsContact), which point to the fact that the results could be directly related to the presence of insects and fungi amid the grains. An elevated acidity index (above 5%) indicates, therefore, that oil or fat are suffering disruptions in their chains, releasing their main components, fatty acids. That is why measuring this index is of extreme importance in assessing the hydrolytic rancidity of the oil or fat that is being consumed. As stated by [22], insects are the major cause of deterioration and losses during storage. They damage the grains, exposing their inner parts, which facilitates the development of fungi. Their infestation damages the vegetal tissue of this grain, producing carbonic gas (CO 2 ) and water (H 2 O), from grain respiration, which contribute to increasing humidity and, consequentially temperature, which in turn makes fungi multiplication easier (non-presented data).

Conclusion
In the conditions in which this study was performed, it can be concluded that: The content of humidity in all corn treatments was lower than the maximum value permitted by the Ministry of Agriculture (14.5%). The hybrid BRS -Gorutuba corn seeds subjected to the phytosanitary treatment with moringa presented normal sprouts, which indicates a non-phytotoxic effect of the product over the seeds. Film coating did not affect the physiologic quality of corn seeds and did not interfere in the treatments in the seeds with starting high quality. Volumetric weight can be employed as a satisfactory indicator to assess corn seed quality. The weight of a thousand seeds can be employed as an auxiliary indicator of volumetric weigh in assessing the quality of the stored corn seeds. The application of Moringa oleifera Lam. on corn seeds is technically viable. From what has been observed, further research over the subject is needed, including a possible relationship between volumetric weight and the traits that mark seed robustness.