## 4 Discussion  
Inflatable solar dryers have recently become popular in tropical regions, but there is a lack of research on their performance and their effect on the quality of dried products. In this research, the performance of an inflatable solar dryer was compared with direct sun drying (DSD), and the impact on maize quality was evaluated. Five maize quality attributes were evaluated: moisture content, mycotoxins (total aflat), yeasts, and moulds, as well as colour. The temperature in the solar collector was, on average, significantly higher compared to the ambient temperature (Figure 2). The observed drying temperatures were suitable for drying maize with a batch drier. For maize grain intended for flour milling, a maximum temperature of 65 \({}^{\circ}\)C is recommended in order to avoid that the high temperature affects the chemical structure and deteriorates the quality [36]. A higher temperature was associated with a lower relative humidity and resulted in higher drying rates. [PERSON], [PERSON], [PERSON], [PERSON] and [PERSON] [26] developed an ISD for drying paddy rice, and the experiments showed that rice was dried to a moisture content of 8% and 12% in dry and rainy seasons, respectively. [PERSON], [PERSON], [PERSON], [PERSON] and [PERSON] [28] evaluated the drying characteristics of maize grain dryed in a solar bubble dryer, where the moisture content reached a safe storage moisture content after 40 h. Comparable performances were achieved for our experiments in terms of the moisture content and drying time. The cascades observed in these curves are characteristic for solar drying systems. They are caused by the diurnal cycle of solar radiation, which, in turn, affects the air temperature [37]. In terms of moisture content reduction, there was no significant difference in the moisture content reduction in maize dried in the ISD compared to the DSD method, because maize reaches the recommended storage moisture content at a comparable time with both methods. Numerous experiments on maize grain storage have shown that maize with an initial moisture content below 14% w.b. could keep the quality attributes like germination capacity, low ethanol and acetic acid contents, and low microbial count under long-term hermetic storage [38]. To stay below this threshold in our experiment, \(<\)14%, was considered as a safe moisture content for storage, and drying was stopped when the moisture content reached this level (Figure 3). The quality parameters analysed showed a slight effect on the maize quality, mostly on the yeast and moulds and the total aflat (Figures 4 and 5). The total aflat was, on average, higher compared to the standard level of 10 ug kg\({}^{-1}\)[8]. The results of the yeast and moulds in Figure 4 showed a nonsignificant (\(p\leq 0.05\)) effect of the treatment on the contamination level. [PERSON] et al. [39] modelled the impact of ambient air drying on mould growth using a batch dryer. The results showed a mould colony count of up to 10\({}^{7}\) CFU g\({}^{-1}\) in the uppermost layer after 400 h of drying [40]. This is a high level of colony count in comparison to the maximum 1.5 \(\times\) 10\({}^{6}\) CFU g\({}^{-1}\) observed in maize dried under ISD in 3 days. The mould count could not be reduced, but the risk of an increase in the colony count is the minimum, because the maize was dried to a low moisture content, which does not allow further mould growth. [PERSON] and [PERSON] [7] reported that mould infection rate varied with the length of storage and dryness of the region, with a highest rate of 50% of the total analysed samples found in the moist mid-altitude regions of Uganda. In Figure 5, a high variation in the total aflatoxin contamination levels of the different samples analysed was observed. The high prevalence of the total aflat in maize in Uganda was previously reported [7; 9; 10]. In their cross-sectional survey conducted in five major markets in Kampala on different staple crops, [PERSON] et al. [41] found that 40% of the analysed samples were contaminated by aflat.