Determination of Optimum Process Parameters of the Drying Rate of Cassava Samples Using the Square Design Method

. Drying is the removal of moisture content and other chemical compositions. The study aims to improve the process parameters involved in cassava chip drying. A statistical approach was utilized to evaluate the significance of the drying variables, such as the various cassava species, the drying temperature, and the drying duration, and their influences on the drying rate of cassava chips. The Latin Square Experiment Design was taken into account when determining the interaction between the critical optimum parameters. At the P 0.05 significance level, an ANOVA was used to analyze the linear and interaction influence of the drying variables on various quality parameters. The study used analysis to compare the F-statistic at four degrees of freedom and obtained an optimal significant level of 3.26. Also, the results showed a significant influence of temperature and period of drying on the drying rate of the cassava chips, but the cassava species did not affect the drying rate of the cassava chips. Also, the results from the statistical analysis were validated and can be employed for monitoring the drying process of cassava chips.


Introduction
Drying is a complex process that involves the temporary movement of heat and mass as well as several rate processes, including physical or chemical transformation, which may modify both the mechanisms of heat and mass transfer and the quality of the final product [1].Shrinkage, puffing, crystallization, and/or glass transition are some examples of the physical modifications that could take place [2].The color, texture, odor, or other qualities of the solid product may occasionally change as a result of desired or undesirable chemical or biological processes [3,4,5].There are oven and open-air sun drying methods available for drying cassava chips.In drying, the main target is the reduction of moisture content and other chemical compositions.The removal of water from a product is achieved during drying by the movement of the water from the innermost, deepest layers to the surface.[2] deduced that the drying of a substance can be classified into two phases, namely, the constant rate phase and the falling rate phase.The first stage, the constant rate period, involves the surface being wet while the rate of drying depends on the condition of the atmospheric air around it; in this case, if the condition of the surrounding air remains constant, then the drying rate would remain constant [6].But the second phase can only begin after the drying of the surface moisture [7].It depends on the rate at which moisture can be transferred to the surface of the substance.Although the concentration of moisture in the substance drops, this influences the rate of drying, so there will be a drop in the rate of movement of moisture from the inner layer to the surface.This implies that the rate of drying will begin to drop.Cassava is an important source of carbohydrates for many people in Nigeria and other parts of the world.Varieties of end products are obtainable from cassava, such as gari, fufu, tapioca, elubo, flour for baking, ethanol, although cassava is one of the easiest root crops to grow, its post-harvest processing is the most difficult because it needs to be handled quickly and detoxified to be edible [8].
The high perishability of the tubers is one of the main problems with cassava processing.Within two to three days of uprooting, degradation caused by metabolic changes and microbial infestation begins.Distances between production areas and processing facilities are frequently an issue, which results in significant post-harvest losses [9].Also, the work of [2] deduced that a high moisture content of about 65% presents a significant obstacle to the processing and production of cassava.It is required to transform cassava into dry, shelf-stable forms by lowering the moisture content to reduce bulk and shipping costs because there are no practical commercial storage options [10].Cassava must undergo special processing to remove or minimize the quantities of cyanogenic glucosides, making the product safe for humans to eat.
There are two affordable methods of drying cassava, which are trenches and sawdust; however, these methods are limited to small-scale drying [8].Also, according to Doymaz and Pala [11], the total disintegration of the cassava root will aid in the release of the natural linamarase enzyme, which facilitates the hydrolysis of linamarin into glucose and acetone cyanohydrins.Above pH 6, these chemical components will break down into volatile hydrogen cyanide (HCN), which is quickly expelled from the system.Over hundreds of years, numerous techniques have been created to better treat cassava roots, resulting in lower cyanide residue [8,12].
There are various techniques to dry cassava, from open-air sun exposure to methods using an oven [13].Due to greater quality control to reduce contamination and control over the drying atmosphere, oven dryers have been considered to have far more advantages.Several reports pointed at a substantial reduction of moisture and cyanogens via the drying of cassava, and the study in [8,14] reported a good amount of cyanogen content removal.According to Udoro et al. [15], the drying rate is influenced by the cassava chip size, loading density, and initial moisture, while the drying process is suitable at temperatures between 45 and 70oC.Furthermore, discussion on the drying kinetics of cassava chips can be found in the works of [9,16,17].
This research would utilize experimental methods to investigate the influence of process parameters such as species, time, and temperature on the drying rate and moisture content of cassava chips.A Latin Square experimental design would be adopted to generate the interactions between the critical optimum parameters, and the accuracy of the linear and interactive process parameters on the drying variables would be determined using ANOVA.

Material Preparation
Fresh cassava roots with various varieties were obtained locally in Enugu, Nigeria.About 2kg of the cassava samples were washed, cleaned, peeled, and chipped to a rectangular shape of 5 cm x 3 cm x 0.2 cm.The chips cassava was then sorted into the same size prior to drying at a given temperature and drying time as shown in Table 1 and Fig. 1.

Table 1. Categorization of the cassava varieties sourced
Figure1.Samples used in the Experiment

Experimental Design
The critical optimum parameters essential in the drying rate of the cassava samples and their interactions were determined using the Latin Square Design of the Experiment of [18].The design is employed to ascertain the statistical significance of variables such as various cassava species, the drying temperature, and drying time on the rate of drying of the chips.As illustrated in Table 2, the Latin Square Design is a randomized design where each parameter only appears once in a column and once in a row.The statistical technique utilized for this investigation is the analysis of variance (ANOVA) as shown in Table 3.The null hypothesis, in this case, is that the drying rate is not significantly impacted by the parameters.At a specific degree of freedom and level of significance, the F-statistic from the ANOVA would be compared to the critical F-statistic.If a parameter's F-statistic is smaller than the crucial F-statistic, the null hypothesis may be accepted, indicating that the parameter has no discernible impact on the drying rate; otherwise, the null hypothesis may be rejected, indicating that the parameter has a discernible impact on drying rate.

The Analysis of Variance (ANOVA)
The design matrix with the response of the Latin Square Design of the Experiment is shown in Table 4.The ANOVA calculation follows the formula in Table 2.The Latin Square Design with the response is shown in Table 5, while the result of the ANOVA calculation is presented in the ANOVA (Table 6).
The F-statistics calculated for the factors were compared with the critical F statistic at four degrees of freedom and a 0.05 significant level [18,19,20].The critical F-statistic at the 0.05 significant level is 3.26.The null hypothesis, which indicates no influence of the drying time and temperature on the rate of drying, can be rejected based on the data in Table 5, whereas the alternative hypothesis, which indicates that the drying time and temperature have a significant impact on the rate of drying, can be accepted.Also, it can be seen that the Fstatistic for the species of cassava was lower than the critical F-statistics at a significant level.This implies that cassava species can be neglected when analyzing drying parameters on cassava chips, while temperature and time are critical parameters.
, 01 The results obtained from the statistical analysis showed that the mean square ranges from 0.00796 to 0.00067, F-statistic ranges from 11.94 to 2.04.The analysis was acceptable for the prediction of the drying behaviour of cassava chips.Also, the data from the results are in good agreement with the results on cassava chip drying in other literature [1,8,17].However, a slight difference in the drying prediction in this work compared to other experimental results in the work of [8,17] can be attributed to the amount of moisture that has evaporated following the experiment, which is in agreement with the work of [9,19,20].

Evaluation of the effects of temperature (T) and time (t) on moisture content (MC)
The influence of drying time on MC of the 5 cassava chip samples under 100 °C constant temperature is shown in Fig. 2; the results show that time is still an important factor in drying.It was further discovered that an increase in drying time resulted in a further decrease in the five samples' MC until equilibrium was attained.This is in line with the study in [17].As seen in Fig. 1, the moisture content of all the samples decreased non-linearly with increased drying time, which can be attributed to the varying forms of water in the cassava roots and the internal factor of diffusion mechanisms in the chips.Another key finding is that the drying process does not depend much on the shape of the chips.The results of MC variation with time and temperature obtained from the design matrix show that the final moisture contents of samples A-E are 12.04, 10.4, 12.05, 13.75, and 13.83%, respectively, after a drying time of 60 min.-5 show the relationship between temperature and time with drying rates.As seen in Fig. 4, the samples' rate of drying was significantly influenced by temperature.Higher temperatures lead to an increase in the drying rate, demonstrating the importance of heat in causing temperature changes and inducing drying in the cassava chips.This supports the view of [21,22,23].The drying rates obtained at the peak temperature for samples A to E are 0.1557, 0.1543, 0.1657, 0.1600, and 0.1529 g/min, respectively.Fig. 5 shows the relationship between drying time and the drying rate of the samples when the temperature is constant.The curve shows an increase in the drying rate with time, with a steep increment from 10 to 50 min later followed by a sharp drop towards the end test time of 60 min, which can be attributed to the chemical composition difference of the samples.This observation is supported by the results obtained in the work of [24].Figs.6-7 depict the interactive plots for dying rate and moisture contents.An increase in temperature and time greatly enhanced the drying rate of the cassava chips as the moisture content decreased.The rapid drop in moisture content was due to chemical composition [24,25,26], while the change in drying rate was attributed to the internal factor of the diffusion mechanism in cassava chips [8,9].

Conclusion and Recommendation
The need for food processing has been fundamental to the continued existence of humans on earth.Like Nigeria, one of the most common household foods is gari, which is one of the end products of cassava.Cassava, due to its easy perishability, calls continuous research on methods to improve its processing techniques.Among the existing methods, both the traditional and mechanized methods have continued to be explored.There is a need to evaluate these methods both experimentally and analytically to obtain the optimum drying parameters.Exploring statistical tools has been reported by various researchers across various strata of academia as an important tool that requires less cost, and time and eliminates the tedious labour required by experimental methods.However, the result of this research showed that statistical tools and optimization tools are important in identifying the critical parameters involved in the drying of cassava chips.The F-statistic at the 0.05 significant level was 3.26.Also, the result showed that the F-statistic for the species of cassava was lower than the critical F-statistics at the significant level.This means that the species of cassava have no significant effect on the drying rate of cassava.Therefore, temperature and time are the two critical factors that affect the drying rate of cassava chips.

Figure 2 .
Figure 2. Influence of Time on Moisture Content at Constant Temperature Fig.3depicts the impact of drying temperatures on samples of cassava chips' moisture contents (%) under a continuous 60-minute drying duration.The results show the significance of temperature in the drying process.At the inception of the drying process, the moisture content looked unaltered.Thereafter, the moisture content against the varying temperature decreased steadily as the higher temperature favoured moisture removal from the samples[21].The five samples exhibited similar moisture contents and temperatures relationship.

Figure 3 .
Figure 3. Influence of Temperature on Moisture Content at Constant Time

Table 2 .
Latin square randomized blocks of experimental design

Table 3 .
The ANOVA Formulae for Latin Square Design

Table 4 .
Design Matrix for the Latin Square

Table 6 .
The ANOVA Table