Simultaneous time-temperature-thickness superposition theoretical and statistical modelling of convective drying of guava

Abstract

Modelling studies of guava drying and quality are presented using theoretical and statistical models by varying temperature from 55 to 75 °C and slice thickness from 3 to 9 mm. The quality of dried fruit was measured for its water activity, colour, vitamin C, and texture. The superposition technique with Midilli-Kucuk model showed efficiency in modelling the drying process with R (2) = 0.9991. The second-order polynomial equations adequately described the quality of dried guava with regression coefficient, R (2) > 0.7. Drying time was a good function of temperature and thickness (P < 0.001); water activity, colour and vitamin C showed strong dependence on temperature (P < 0.1); while texture was mainly influenced by its thickness (P < 0.005). The optimum drying temperature of 70 °C at slice thickness of 6 mm was determined using the desirability function method. Simultaneous modelling using the theoretical and statistical drying models provides information on water diffusion and evaporation with the drying responses and factors.

Use of response surface methodology to optimize the drying conditions of a bioactive ingredient derived from the African opaque sorghum beer

“…This is confirmed by its surface plot (Figure 1b). The same trend was reported by Kek et al (2014) for drying of guava.…”

“…Thus, the experimental value was compared with the predicted one from the optimized model by calculating the percentage error to determine the adequacy of the drying process and response surface models. The percentage error, PE which is lower than 10 % indicates a good fit (McLaughlin and Magee, 1998;Kek et al, 2014).…”

Investigation of dynamic quality changes and optimization of drying parameters of carrots (Daucus carota var. laguna)

“…The authors reported total drying times of approximately 4.3, 3.3, and 2 hr for 3 mm thickness when dried at 55, 65, and 75°C with an airflow of 2.0 m/s and around 6, 4, and 3 hr when drying under the same conditions for 6 mm. The increase in drying time with an increase in slice thickness must be due to the lower surface area‐to‐volume ratio, and the longer distance for the moisture to travel from the inside of the material to the surface (Kek, Chin, & Yusof, ). In other words, the drying rate will increase as the temperature increases, and the slice thickness decreases due to shorter transport distance and an increased relative of heat and mass transfer (Figure ).…”

Stability of vitamin C in fresh and freeze-dried capsicum stored at different temperatures

“…It is the most sensitive and destructed when a commodity is exposed to adverse handling and storage conditions (Lee and Kader 2000). Vitamin C stability in fruits and vegetables was studied during different methods of drying (Goula and Adamopoulos 2006;Marques et al 2006Marques et al , 2007Gupta et al 2013;Kek et al 2013) and during storage at chilled or around room temperature (Johnston and Hale 2005;Burdurlu et al 2006;Torregrosa et al 2006;Klimczak et al 2007;Majumdar et al 2009;Gonzalez-Molina et al 2012). The loss of vitamin C during storage was considerably lower in freeze dried powder as compared to vacuum, and tunnel dried guava powder (Verma et al 1993).…”