Drying is the main process used to treat lotus seeds for storage. In this study, response surface methodology was used to optimize processing methods for microwave vacuum (MWV) drying of lotus seeds and to create a desirable product. A central composite design with three important factors: microwave output power (2.0–4.0 kW), vacuum degree (−0.070 to −0.090 MPa) and on/off ratio (68/52 s to 99/21 s) was used to study the response variables of drying time, shrinkage ratio, rehydration ratio and whiteness index. The optimum conditions for MWV drying of lotus seeds were determined to obtain a minimal drying time, minimal shrinkage ratio, maximum rehydration ratio and maximum whiteness index. The optimum drying conditions were found to be: microwave output power 3.2 kW, vacuum degree −0.083 MPa and on/off ratio 94/26 s. Under these optimal conditions, drying time, shrinkage ratio, rehydration ratio and whiteness index were found to be 10 min, 37.66%, 157.1% and 68.83, respectively.
AbeTAfzalTM (1997). Thin-layer infrared radiation drying of rough rice. Journal of Agricultural Engineering Research67(4): 289–297.
2.
Al-HarahshehMAl-MuhtasebAHMageeTRA (2009). Microwave drying kinetics of tomato pomace: effect of osmotic dehydration. Chemical Engineering and Processing48(1): 524–531.
3.
AlibasI (2010). Determination of drying parameters, ascorbic acid contents and color characteristics of nettle leaves during microwave-, air- and combined microwave-air-drying. Journal of Food Process Engineering33(2): 213–233.
4.
ArgyropoulosDHeindlAMullerJ (2011). Assessment of convection, hot-air combined with microwave-vacuum and freeze-drying methods for mushrooms with regard to product quality. International Journal of Food Science and Technology46(2): 333–342.
5.
ArtnaseawATheerakulpisutSBenjapiyapornC (2010). Development of a vacuum heat pump dryer for drying chilli. Biosystems Engineering105(1): 130–138.
6.
BhatRSridharKR (2008). Nutritional quality evaluation of electron beam-irradiated lotus (Nelumbo nucifera) seeds. Food Chemistry107(1): 174–184.
7.
BondarukJMarkowskiMBlaszczakW (2007). Effect of drying conditions on the quality of vacuum-microwave dried potato cubes. Journal of Food Engineering81(2): 306–312.
8.
ChangrueVOrsatV (2009). Osmotically dehydrated microwave vacuum drying of carrots. Canadian Biosystems Engineering51: 11–19.
9.
ContrerasCMartínMEMartinez-NavarreteNChiraltA (2005). Effect of vacuum impregnation and microwave application on structural changes which occurred during air-drying of apple. LWT - Food Science and Technology38(5): 471–477.
10.
CuiZWLiCYSongCFSongY (2008). Combined microwave-vacuum and freeze drying of carrot and apple Chips. Journal of Food Engineering26(12): 1517–1523.
11.
CuiZWXuSYSunDW (2003). Dehydration of garlic slices by combined microwave-vacuum and air drying. Drying Technology21(7): 1173–1184.
12.
CuiZWXuSYSunDW (2004). Microwave-vacuum drying kinetics of carrot slices. Journal of Food Engineering65(2): 157–164.
13.
DeveceCRodriguez-LopezJNFenollLGTudelaJCatalaJMde los ReyesE (1999). Enzyme inactivation analysis for industrial blanching applications: comparison of microwave, conventional, and combination heat treatments on mushroom polyphenoloxidase activity. Journal of Agricultural and Food Chemistry47(11): 4506–4511.
14.
FengHTangJ (1998). Microwave finish drying of diced apples in a spouted bed. Journal of Food Science63(4): 679–683.
15.
FigielA (2009). Drying kinetics and quality of vacuum-microwave dehydrated garlic cloves and slices. Journal of Food Engineering94(1): 98–104.
16.
FigielA (2010). Drying kinetics and quality of beetroots dehydrated by combination of convective and vacuum-microwave methods. Journal of Food Engineering98(4): 461–470.
17.
GiriSKPrasadS (2007a). Drying kinetics and rehydration characteristics of microwave-vacuum and convective hot-air dried mushrooms. Journal of Food Engineering78(2): 512–521.
18.
GiriSKPrasadS (2007b). Optimization of microwave-vacuum drying of button mushrooms using response-surface methodology. Drying Technology25(4–6): 901–911.
19.
GuoHB (2009). Cultivation of lotus (Nelumbo nucifera Gaertn. ssp nucifera) and its utilization in China. Genetic Resources and Crop Evolution56(3): 323–330.
20.
HouXJChenW (2008). Optimization of extraction process of crude polysaccharides from wild edible BaChu mushroom by response surface methodology. Carbohydrate Polymers72(1): 67–74.
21.
KredyHMHuangDHXieBJHeHYangENTianBQXiaoD (2010). Flavonols of lotus (Nelumbo nucifera, Gaertn.) seed epicarp and their antioxidant potential. European Food Research and Technology231(3): 387–394.
22.
LinTMDuranceTDScamanCH (1998). Characterization of vacuum microwave, air and freeze dried carrot slices. Food Research International31(2): 111–117.
23.
LiuCPTsaiWJLinYLLiaoJFChenCFKuoYC (2004). The extracts from Nelumbo nucifera suppress cell cycle progression, cytokine genes expression, and cell proliferation in human peripheral blood mononuclear cells. Life Sciences75(6): 699–716.
24.
MaskanM (2000). Microwave/air and microwave finish drying of banana. Journal of Food Engineering44(2): 71–78.
25.
Oms-OliuGSoliva-FortunyRMartin-BellosoO (2008). Modeling changes of headspace gas concentrations to describe the respiration of fresh-cut melon under low or superatmospheric oxygen atmospheres. Journal of Food Engineering85(3): 401–409.
26.
PCCn (2005). Pharmacopoeia Committee of PR China, Beijing: Chemical Industry Publishing House, pp. 193–193.
27.
ShamPWYScamanCHDuranceTD (2001). Texture of vacuum microwave dehydrated apple chips as affected by calcium pretreatment, vacuum level, and apple variety. Journal of Food Science66(9): 1341–1347.
28.
SongXJZhangMMujumdarASFanLP (2009b). Drying characteristics and kinetics of vacuum microwave-dried potato clices. Drying Technology27(9): 969–974.
29.
Song HB, Zheng BD, and Zeng SX (2009a) Stereo collocation microwave vacuum drying machine. PRC Utility Model Patent CN 201281532, 29 July.
30.
WuYCuiSWTangJGuX (2007). Optimization of extraction process of crude polysaccharides from boat-fruited sterculia seeds by response surface methodology. Food Chemistry105(4): 1599–1605.
31.
YenGCDuhPDSuHJ (2005). Antioxidant properties of lotus seed and its effect on DNA damage in human lymphocytes. Food Chemistry89(3): 379–385.
32.
YongsawatdigulJGunasekaranS (1996). Microwave vacuum drying of cranberries: part II: quality evaluation. Journal of Food Processing and Preservation20(2): 145–156.
