A 3D response surface plot for the effect of drying conditionson water activity is shown in Fig. 1b. The water activity is shownto decrease with increase in drying time and temperature. Theindividual optimum region led to be a minimum water activity(Y2 = 0.57±0.18) obtained at 4.9 h drying time, 60°C dryingtemperature and 1.4 kg/m2 loading capacity. The illustrationchanges of aw showed relationship with moisture content.Reducing the aw and moisture content would extend the shelflife and inhibit microorganism. These results were in agreementwith previous studies 41.Texture: The results of this study indicated that texture(brittleness) (Y3) of dried kaffir lime leaves was significantly(p<0.05) affected by both main effect of drying time, dryingtemperature and their quadratic effects, respectively (Table 4).A 3D surface plot displays the effect of drying time and dryingtemperature on the texture (Fig. 1c). The individual optimumregion led to a maximum texture (Y3 = 6.54 ± 0.65) which waspredicted to be obtained at the drying time of 4.9 h, shows dryingtemperature, 60°C and loading capacity, 1.4 kg/m2, respectively.Fig. 1c shows an increase in texture with an increase in dryingtime and drying temperature. The higher texture values mean thesamples are more brittle after undergoing different dryingconditions as compared to the lower texture values (Table 2).The texture of kaffir lime leaves that have been dried at lowtemperature (40°C) was softer than that of kaffir lime leavesthat was dried at high temperature (80°C). Besides that, it took alonger time to fracture the dried samples because during drying,liquid diffuses to the surface of the kaffir lime leaves from theinterior and carries solute with it. It can be observed that thesamples that have been dried at higher temperature resulted invery dry skin compared to low temperature drying. These findingsfurther support the idea of Lin et al. 42 who showed that as themoisture evaporates, solutes concentrate and precipitate, leavinga hard and dry skin.
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