Moisture Content Prediction of Dried Longan Aril from Dielectric Constant Using Multilayer Perceptrons and Support Vector Regression

Abstract

Problem statement: Estimation of moisture contents of dried food products from their dielectric constants was an important step in moisture measurement systems. The regression models that provide good prediction performance are desirable. Approach: The Multilayer Perceptrons (MLP) and Support Vector Regression (SVR) were applied in this research to predict the moisture contents of dried longan arils from their dielectric constants. The data set was collected from 1500 samples of dried longan aril with five different moisture contents of 10, 14, 18, 22 and 25% Wet basis (Wb.) Dielectric constant of dried longan aril was measured by using our previously proposed electrical capacitance-based system. The results from the MLP and SVR models were compared to that from the linear regression and polynomial regression models. To take into account the generalization of the models, the four-fold cross validation was applied. Results: For the training sets, the average mean absolute errors over three bulk densities of 1.30, 1.45 and 1.60 g cm −3 were 1.7578, 0.6157, 0.3812, 0.3113, 0.0103 and 0.0044% Wb for the linear regression, second-, third-, fourth-order polynomial regression, MLP and SVR models, respectively. For the validation sets, the average mean absolute errors over the three bulk densities were 1.7616, 0.6192, 0.3844, 0.3146, 0.0126 and 0.0093% Wb for the linear regression, 2nd, 3rd and 4th-order polynomial regression, MLP and SVR models, respectively. Conclusion: The regression models based on MLP and SVR yielded better performances than the models based on linear regression and polynomial regression on both training and validation sets. The models based on MLP and SVR also provided robustness to the variation of bulk density. Not only for dried longan aril, the proposed models can also be adapted and applied to other materials or dried food products.

The Drying Kinetics of Chilies using a Rotating Fluidized Bed Technique

“…In addition, after increased the temperature of drying air from 70-120°C, the latent heat was intensified, so the dehydration from the moist produce was improved (Bovornsethanan and Wongwises, 2007;Brooks et al, 2008;Theansuwan et al, 2008). The researchers have been recently reported the same phenomenon for other grain, such as red chilies (Anwarul Huq and Arshad, 2010), Bird's chilies (Amaroek et al, 2010), chopped coconut (Madhiyanon et al, 2009) and apple (Marjan et al, 2010). The drying time to dry chilies from initial moisture content of approximately 350 ± 5%db to final moisture content of approximately 10 ± 1%db were 257,163,131,98,78 and 69 min at 70, 80, 90, 100, 110 and 120°C of drying air temperature, respectively.…”

“…The drying time to dry chilies from initial moisture content of approximately 350 ± 5%db to final moisture content of approximately 10 ± 1%db were 257,163,131,98,78 and 69 min at 70, 80, 90, 100, 110 and 120°C of drying air temperature, respectively. It was reported that the using of another dryer took 13 h to dry chilies from 325-10.5%db at 65°C of drying air temperature (Amaroek et al, 2010;Mazloomi et al, 2010) and 106.7 min to dry the sliced bird's eye chilies to 16%db at 70°C of drying air temperature (Omar et al, 2008). Initially, the abundance of free water on the produce surface contributed the effortless moisture liberation; however, much more difficult it might be to expel water after that, when the produce surface becomes harder due to shrinkage (Kowalski et al, 2010).…”

“…Assuming uniform initial moisture distribution and negligible external resistance, the solution proposed by following (Amaroek et al, 2010):…”

“…The chilies are commonly used as condiment and they are the ripe fruits of the species of genus capsicum (Amaroek et al, 2010). After harvest, chilies contained high moisture estimated 400%db (Amaroek et al, 2010); nevertheless, moisture content of 16%db were acceptable in the export market (Amaroek et al, 2010).…”

“…After harvest, chilies contained high moisture estimated 400%db (Amaroek et al, 2010); nevertheless, moisture content of 16%db were acceptable in the export market (Amaroek et al, 2010). Then, chilies must be dried for making chili powder and for keeping in the short or long term storages.…”