Effect of Process Parameters on Quality Properties of Microwave Dried Red Pitaya (Hylocereus costaricensis)

Abstract

The effect of microwave power density on the microwave drying of red pitaya (Hylocereus costaricensis) was investigated using a small modified commercial microwave. Microwave power density was varied in the range of 5.47 to 19.02 W/g. The ambient, internal sample and sample surface temperatures, and moisture loss were measured during microwave drying at various microwave power densities. The drying rate increased with increasing power density. The temperature profiles rapidly reached their saturation level. The experimental moisture loss data were fitted to the Tang and Cenkowski drying model using a value of residual sum of squares (RSS) to evaluate the goodness of fitting the model. The dried product was analysed to examine the quality such as color, shrinkage, tensile hardness and structure. The results showed that the color change is higher at higher power density and temperature because of the faster browning rate and faster drying rate. The beginning of the color change corresponded closely to the beginning of the falling rate period. The microwave drying also caused the red pitaya to shrink to a greater extent of up to 70% at higher power density because of the faster drying rate. The internal structure also tended to collapse during microwave drying.

Drying of Exotic Tropical Fruits: A Comprehensive Review

“…Nordin et al (2008) found that microwave drying of pitaya consists of an initial transient period followed by a falling rate period. Rapid microwave penetration caused the internal and surface temperature to rise rapidly during drying.…”

“…The changes in a values were very small compared to the L and b values, which indicates that the variation in red-green spectrum is minimal whereas the lightness and blue-yellow spectrum were affected by drying significantly. It was reported that the internal structure collapsed during the microwave drying (Nordin et al 2008).…”

Microwave heat treatment of dent corn (Zea mays var. indentata sturt.): Drying kinetic and physical properties

“…The study of the drying kinetic of foods during microwave heat treatment has recently been a subject of interest for various investigators. Some of the previous studies about microwave drying can be listed as; corn (Nair et al, 2011;Gabor et al, 2007;Bake, 1992;Beke and Mujumdar, 1997), basil (Demirhan and Özbek, 2009), apple (Askari et al, 2008), okra (Dadali et al, 2007), spinach (Dadali et al, 2007, noodles (Xue et al, 2008), garlic (Sharma and Prasad, 2006;Souraki and Mowla, 2008), potato (Gunasekaran and Yang, 2007;Oztop et al, 2007), bacon (James et al, 2006), maize (Velu et al, 2006), mint (Özbek and Dadali, 2007), spaghetti (Cocci et al, 2008), tomato (Al-Harahsheh et al, 2009), red pitaya (Nordin et al, 2008), leek , avocado (Guzmán-Gerónimo et al, 2008), Chilean hazelnuts (Uquiche et al, 2008), and parsley (Soysal et al, 2006).…”