Hot Air Drying Characteristics of Sweet Potato Using Moisture Sorption Isotherm Analysis and Its Quality Changes During Drying

Abstract

Changes in the quality of sweet potato during hot air drying, such as L-ascorbic acid, sugar content, surface color and hardness, and drying characteristics, were investigated at temperatures of 30, 40, 50, and 60°C. Equilibrium moisture contents (EMC) of sweet potato samples in the desorption process were measured by a static method at the four aforementioned temperatures and six selected relative humidity levels. Using both the measured moisture content data in the drying test and the EMC values, hot air drying characteristics of sweet potato was estimated. Changes in L-ascorbic acid content of sweet potato during hot air drying was measured, wherein a first-order reaction rate equation was applied to model the change in decomposition of L-ascorbic acid content. In addition, surface color, sugar content, and surface hardness were also measured. The total color change (?E) of the samples was observed to decrease as drying temperature was increased. The effects of sample sugar concentration on surface hardening during hot air drying of sweet potato are discussed.

Applicability of vacuum-microwave drying for tomato fruit based on evaluations of energy cost, color, functional components, and sensory qualities

“…Hot air drying (HAD) is a simple method commonly applied to fruits and vegetables (Bazyma et al, ; Ogura, ). A number of researchers have examined HAD of fruits and vegetables with a high moisture content, such as kiwifruits (Orikasa et al, ), apples (Sjöholm & Gekas, ), garden beets and carrots (Pabis & Jaros, ), and sweet potatoes (Orikasa et al, ). Some disadvantages of HAD include its low energy efficiency and the lengthy drying time required during the falling‐rate period (Bazyma et al, ; Drouzas, Tsami, & Saravacos, ).…”

Impacts of hot air and vacuum drying on the quality attributes of kiwifruit slices

“…Hot air drying is a simple, common method for drying vegetables and fruits (Leonid et al, 2006;Ogura, 1993). Numerous investigators have examined the hot air drying characteristics in fruits and vegetables with a high moisture content, such as tomatoes (Orikasa et al, 2005), apples (Sjoholm and Gekas, 1995), garden beets, carrots (Pabis and Jaros, 2002), and sweet potatoes (Orikasa et al, 2010). The disadvantages of hot air drying include its low energy efficiency and lengthy drying time during the falling rate period.…”

An Inexpensive, Stable, and Accurate Relative Humidity Measurement Method for Challenging Environments

“…Compared to modern electronic relative humidity sensors such as capacitive relative humidity sensors or resistive relative humidity sensors, the psychrometer is one of the relative humidity measurement devices that can be used in a dirty environment, can withstand state changes of water, and can provide a large range of measurement values. The psychrometer is used in different measurement environment in many current applications [ 9 , 10 , 11 , 12 , 13 ].…”

“…Several researchers discuss the measurement accuracies of psychrometer. Ustymczuk and Giner examined the errors of psychrometric measurement of relative humidity and used an error propagation formula to convert temperature errors to relative humidity errors [ 10 ]. Mittal and Zhang developed a trained artificial neural network based psychrometric chart that can be used to predict psychrometric parameters in practical applications [ 25 ].…”