# Experimental Verification of Yam (_Dioscorea rotundata_) Drying with Solar Adsorption Drying
## 3 Results
### Drying Different Yam Cultivars
#### 3.2.2 Drying Effect on Cultivars and Composition  
Figure 8 shows the drying behavior of three yam cultivars ('Pona', 'Lilii', and 'Dente') subjected to SAD, SD and OSD. While it took 3-4 days to dry 'Pona' and 'Lilii' to a specified moisture content, it took 7 to 9 days to dry 'Dente' to a moisture content below 10% (wb). 'Lilii' and 'Pona' have large granules which lead to a lower water binding affinity, whereas 'Dente', has smaller granules that result in higher water binding. For all varieties SAD, which involves night drying, reduced the drying cycle as compared to the SD. The OSD was less effective in terms of moisture removal and subsequently final moisture content.  
By the end of the third day the moisture ratio of 'Lilii' was between 0.0606-0.203 for the three methods while that of 'Dente' was between 0.133-0.224. SAD recorded the lowest moisture ratio and the OSD recorded the highest. It took 4 days for SD to bring the moisture ratio of 'Lilii' to or below 0.06  
Figure 8: Comparison of drying methods on different varieties of yam. The grey portions represent night drying.  
while SAD needed three days. SAD had, thus, the shortest drying cycle compared to the other drying methods. Meanwhile, final moisture ratios of 0.111, 0.116, and 0.119 were reached after 4, 5, and 9 days using SAD, SD, and OSD respectively in drying 'Dente'. These different drying times are only partly as a consequence of the difference in initial moisture content, but mainly due to the differences in the food matrix. It is possible that 'Liii' and 'Pona' may have large granules that lead to lower water binding affinity, whereas the converse holds for 'Dente'.  
Table 2 shows the composition of fresh and dried yam per dry weight basis. The moisture content of fresh yam ranged between 1.55 to 2.06 kg/kg dry matter with 'Pona' recording the least and 'Dente' recording the highest. The final moisture content values of the samples using various drying methods range between 0.05 to 0.09 kg/kg dry matter. The differences between the cultivars are reflected in the granules of the dried powder. The granules of 'Pona' are triangular, oval and irregular, those of 'Liii' oval, elliptical and rounded while 'Dente' had predominantly cylindrical, oval and elliptical or triangular granule shapes. These shapes regimes have effect on the extent of water removal from the sample.  
Table 2 shows that, generally, the drying methods do not affect the proximate composition of samples but rather the final moisture content as mentioned by [PERSON] et al. [15]. Though generally there is marginal increase in fiber and decrease in protein composition between fresh and dried samples, there is no obvious trend in variability among the values of cultivars. Effect of drying on protein is as a result of decrease in its digestibility and biological value as mentioned by [PERSON] [28]. Heating does not generally affect total dietary fiber content [29], however, it causes the increase of the insoluble dietary fiber content as a result of complexing of its components with protein and amino acids [30].