Evaluation Of Hermetic Technologies In The Control Of Insect Infestation, Mold Proliferation And Mycotoxin Contamination Of Stored Maize In Kenya

Abstract

In Africa, maize is one of the most important food crops, yet it is also susceptible to insects infestation, microbial attack and mycotoxin contamination. These cause significant economic losses and deleterious health effects to humans and animals. Strategies such as storage of maize in hermetic bags are known to be effective in reducing post-harvest contamination by fungi and mycotoxin production. This study was conducted with the aim to investigate the effectiveness of using hermetic technologies in the control of insect infestation, fungal proliferation, and mycotoxin contamination as well as preserve the nutritional quality and seed viability in a safe and environmentally friendly system. Maize used for this study was collected from the farmers in Nakuru County and data on maize production practices recorded using a semi-structured questionnaire. Three factors were used in the design of this study: contaminated grain with molds vs. clean grain; two levels of grain moisture levels; and ten storage methods, of which eight were hermetic. The overall study design was a 2 x 2 x 10 completely randomized block design (RCBD) with 3 replications. The first factor was artificial infestation with fungi (fusarium and aspergillus strains). All technologies were tested with artificially inoculated molds and the other set was not be inoculated. The second factor is grain moisture. All the treatments were subjected to two grain moisture levels, low (12-13%) or high (14-15%) determined using standard methods. The final factor was the storage technologies; metal silos (MS); plastic silos (PS); Super Grain IV-RTM bag (SGB); AGRO-Z (A-Z-); AGRO-Z+ (A-Z+) impregnated with insecticides PICS bag; Elite bag; ZeroFly and two controls; the standard woven polypropylene (PP) bags one with grain treated with 0.05% Actellic Super (PP+) and one without insecticide. Each technology was analyzed for gas composition. Grain samples of approximately 1kg were collected from each storage technology at 0, 4 and 8 months and analyzed for moisture levels, insect infestation, fungal proliferation, mycotoxin contamination, seed viability and grain composition during the xx experiment. During artificial inoculation, the fungal inoculums (fusarium and aspergillus strains) were placed in the middle of the grain in perforated bags that allowed contact with the other grains. Sitophillus zeamais and Postephanus truncatus types of storage insects were counted and recorded as live and dead from 1000 sampled kernels. Natural infestation relied on existing insect infestation only. Isolation of mycotoxin producing fungi was done employing the serial dilution and spread plate technique on Potato Dextrose Agar; and total aflatoxin and fumonisin in maize kernels was analyzed by Vicam kits. Maize from the farmers was found to contain less than 10 ppb aflatoxin with an average of 1.63 ppb under moisture content that varied from 13-16.47 %. Hermetic technologies were able to modify gas composition, increasing CO2 by 12.98 % and dropping O2 by 11.77%. After 8 months of maize storage, there was 21% insects infestation in hermetic technologies and 53 % in PP bags and the least amount 17% in PP+ bags. Mycotoxin fungi and aflatoxin contamination were higher in PP bags above the local and international standards and the metal and plastic silos with un-inoculated grains complied with the European Commission (EC 4 ppb) limit but grain inoculated was above this limit. The hermetic bags were effective in the control of aflatoxin contamination below the limit of 10 ppb set by KEBS except for the grain inoculated in PP bags that were above 20 ppb (FDA max limit), KEBS and EC limits. The percentage seed viability reduced to less than 5% in PP bags, 45% in hermetic storages and 55% in PP+ bags. There was no significant difference in nutritional composition of maize in all the storage technologies at P>0.001. The success of the hermetic technologies in preserving the quality of maize is synergized with proper drying of maize before storage and good handling practices of both the maize and the technologies.