Effect of combined microwave‐hot air drying and superheated steam drying on physical and chemical properties of rice

Abstract

Summary Jasmine rice (Oryza sativa L.) was subjected to two drying operations: combined microwave‐hot air drying (MHA) at initial power intensity of 3, 4 and 6 W g−1 and superheated steam drying (SHS) at 300 °C and 400 °C. During drying, kinetic rate constants of SHS were significantly higher than those of MHA. Both drying operations could decrease enthalpy of starch gelatinisation from 9.28 J g−1 to 1.64–6.17 J g−1, increase gelatinisation extent to 33.51–82.33%, decrease crystallinity from 28.87% to 18.15–21.33%, improve scavenging ability of 1,1‐diphenyl‐2‐picrylhydrazyl, increase ferric reducing antioxidant power and increase hardness of cooked rice from 5.66 N to 5.83–6.55 N, depending on microwave power and drying medium temperature. However, taste profiles and liking scores were comparable to the regular brown rice. Therefore, MHA and SHS operations could be potentially used for reducing drying process and promoting antioxidant activity.

Effect of convective, infrared and microwave heating on drying rates, mass transfer characteristics, milling quality and microstructure of steam gelatinized Paddy

“…They concluded that the A‐type crystallinity decreases with an increase in drying air temperature. Horrungsiwat et al () studied the drying of rice with superheated steam and microwave hot air and reported A‐type crystallinity at 2θ of 15°, 17°, 18°, and 23°.…”

“…Taechapairoj, Prachayawarakorn, and Soponronnarit () dried paddy using superheated steam in a fluidized bed dryer at a temperature in the range 150–170 °C and reported gelatinized and swelled structure of starch granules. Horrungsiwat et al () studied the microstructure of rice dried by microwave and superheated steam and reported a change in starch structure from rough to smooth due to partial gelatinization.…”

“…The diffractograms were taken over a 2 θ (Bragg angle) ranging from 5° to 40° with a step size of 0.02°. The percentage of crystallinity ( X c ) in rice was estimated as follows (Horrungsiwat et al, ; Kale et al, ): …”

“…Many researchers have carried out infrared drying of paddy to give higher head rice, but it is having low penetration depth and takes considerable time at low power to product ratio (6.01–10.08 W g −1 ) (Abe & Afzal, ; Das, Das, & Bal, ; Pan et al, ). Microwave drying is another alternative to dry the parboiled paddy at comparatively faster rates with a power density in the range 3–6 W g −1 (Horrungsiwat, Therdthai, & Ratphitagsanti, ). However, there is no clear research reported showing the actual difference between hot air, infrared hot air, and microwave rotary drum drying (MWD) of steam gelatinized paddy along with the quality evaluation (milling yield, XRD, and SEM).…”

Effects of ultrasonic and enzymatic treatment on physical and chemical properties of brown rice

“…According to several studies, rice starch was classified into A‐type. However, the formation of amylose complex could change the crystalline pattern of starch into V‐type after some treatments such as soaking (Manful, Grimm, Gayin, & Coker, ), drying (Horrungsiwat, Therdthai, & Ratphitagsanti, ), and parboiling (Derycke et al, ), leading to change in starch properties. Thermal properties have been investigated using differential scanning calorimetry (DSC) to determine the gelatinization of rice after treatment which may be related to cooking properties and glycemic response of brown rice (Ramírez‐Miranda et al, ; Zhu, Liu, Wilson, Gu, & Shi, ).…”