# Evaluation of Design Parameters on Drying of Kiwi Fruit
## 3 Results and Discussions
### Design Analysis and Analysis of Variance (ANOVA)  
Statistical approaches are used when experimental designs are applied to any system. However, experimental design techniques are not just related to statistics. These techniques are approaches that improve quality, reduce costs and significantly reduce the number of experiments by being used in all research and development activities. In this way resources are being used more efficiently, saving both time and material substantially. The parameters, or alias control factors, selected to enable this work to be performed are; thickness, speed, and drying time. The parameters and their levels are given in Table 3.  
As design of experiment method, the Taguchi technique was used. In this method a statistical value known as the signal to noise (_S/N_) ratio is used to analyze the results obtained from the experiments where \(S\) refers to signal and \(N\) refers to noise. The results obtained from the experiments are evaluated by converting them to the _S/N_ ratio. The \(S\) is the actual value obtained from the system, and \(N\) points out the factors that does not participate in the experiment design but has an effect on the experimental result. Noise sources are all variables that cause the value of the analyzed performance characteristic to deviate from the target value. So the smaller the \(N\) value, the closer the target value is. For this reason, the purpose of this method is always to maximize the _S/N_ ratio. There are various _S/N_ ratios in the literature. In this study, it is desired that the humidity rate value we regard as performance characteristic is minimum. For this reason, the lower is better (LB) criterion is used. The _S/N_ ratios calculated for the humidity rate and the orthogonal array L\({}_{18}\) test design are given in Table 3. The averages of the _S/N_ ratios given in Table 3 are presented graphically in Figure 10.  
Figure 8: Surface temperature as a function of drying time for drying air velocity of 0.5, 1 and 1.5 m/s and slice thicknesses of 8 mm for kiwi fruits. Figure 9: Mass loss of kiwi fruits at different slice thicknesses. It was mentioned that the _S/N_ ratio has to be maximized at all times. In other words, optimum values always occur at the greatest _S/N_ ratios. Accordingly, when Figure 10 is examined it is clear that the optimum levels will take place in the case of A1B3C3. The optimum levels are shown in Table 4. \begin{table}
\begin{tabular}{c c c c c} \hline \hline  & & \multicolumn{3}{c}{**Average _S/N_ Ratios (dB)**} \\ \hline Control factors & Level 1 & Level 2 & Level 3 & \\ A & Thickness of the slices (mm) & 9.48 \({}^{*}\) & 4.68 & – \\ B & Air velocity (m/s) & 4.79 & 4.93 & 11.53 \({}^{*}\) \\ C & Drying time (min) & 3.11 & 5.77 & 12.37 \({}^{*}\) \\ \hline \hline \end{tabular} Average _S/N_ ratio = 7.08 dB, \({}^{*}\) Optimum Level.  
\end{table} 
Table 4: Optimum levels of the variances. Figure 10: Average \(\eta\) for humidity rate. \begin{table}
\begin{tabular}{c c c c} \hline \hline
**Experiment No.** & & **Control Factors** & & _S/N Ratio_ \\ \hline  & A & B & C & \\  
\hline \hline \end{tabular}
\end{table} 
Table 3: _S/N_ ratio and control factors. The main purpose of applying ANOVA method is that, the effect of the parameters used in the experiments on the \"humidity rate\" which we have determined as the performance characteristic can be determined in percentages [23]. However, in order to determine whether the parameters used in the experiments have a statistically significant effect on the performance characteristic, an analysis called \(F\) test is also required. The large value of the \(F\) test means that the effect of the parameters studied on the performance characteristic is also significant. The statistical calculation method required for calculating this value is given in Appendix A. The value of \(F\) given in Appendix A is found by dividing the variance of the parameter being considered by its variance of error.