In this study,kiwifruit was used as raw materials,and FD-MVD combined drying method was used to select different moisture conversion points (FD 4 h,FD 6 h,FD 8 h,FD 10 h,FD 12 h). By combing the following characters including sensory quality,rehydration ratio,bulk density,porosity of kiwifruit during drying,with the drying characteristics,pore structure and moisture distribution characteristics of kiwifruit slices during the drying process,the optimal moisture transfer point was determined. The results showed that the drying characteristics of kiwifruit slices varied greatly under different moisture levels. The sensory score and rehydration ratio increased with the increase of the FD time. Moreover,the MVD time decreased with the increase of the FD phase time,on the contrary,the total drying time increased. And the results of the micrographs indicated that the cell sizes of the central and peripheral parts of the kiwifruit were significantly different,which caused the different conversion of moisture in the central and peripheral parts. So,FD 12 h was the optimal moisture conversion point based on the sensory quality analysis. While,if the microstructure was considered as the prefer condition,the FD 8 h sample had the best cell structure. The choice of moisture conversion point was not only affected by the quality of the sample,but also by drying time and drying energy consumption. Therefore,FD 8 h was the optimal moisture conversion point when total drying time and quality (sensory,microstructure) were considered.
[1] HWANG J S, CHO C H, BAIK M Y, et al.Effects of freeze-drying on antioxidant and anticholinesterase activities in various cultivars of kiwifruit (Actinidia spp.)[J]. Food Science and Biotechnology,2017,26(1): 221-228.
[2] MARA B,PAULA V,ANA S,et al.Effect of microwave heating on sensory characteristics of kiwifruit puree[J].Food and Bioprocess Technology,2012,5(8): 3 021-3 031.
[3] CONCHA-MEYER A A, D′IGNOTI V, SAEZ B,et al. Effect of storage on the physico-chemical and antioxidant properties of strawberry and kiwi leathers[J]. Journal of Food Science,2016,81(3):C569-C577.
[4] ORIKASA T, WU L, SHIINA T, et al.Drying characteristics of kiwifruit during hot air drying[J]. Journal of Food Engineering,2007,85(2):303-308.
[5] MASKAN M.Kinetics of colour change of kiwifruits during hot air and microwave drying[J]. Journal of Food Engineering,2001,48(2): 169-175.
[6] TIAN Y T,WU S Z,ZHAO Y T.Drying characteristics and processing parameters for microwave-vacuum drying of kiwifruit (Actinidia deliciosa) slices[J]. Journal of Food Processing & Preservation,2015,39(6): 2 620-2 629.
[7] CHANDRASEKARAN S, RAMANATHAN S, BASAK T.Microwave food processing—A review[J]. Food Research International,2013,52(1):243-261.
[8] KONE K Y, DRUON C, GNIMPIEBA E Z, et al.Power density control in microwave assisted air drying to improve quality of food[J]. Journal of Food Engineering,2013,119(4):750-757.
[9] CHENG W M, RAGHAVAN G S V, NGADI M, et al. Microwave power control strategies on the drying process I. Development and evaluation of new microwave drying system[J]. Journal of Food Engineering,2006,76(2):188-194.
[10] ZHU C H,GONG Q,LI J X.Research progress on comprehensive utilization of kiwifruit processing[J]. Preservation and Processing,2013,13(1):57-62.
[11] REYES A, EVSEEV A, MAHN A, et al.Effect of operating conditions in freeze-drying on the nutritional properties of blueberries[J]. International Journal of Food Sciences and Nutrition,2011,62(3):303-306.
[12] JIANG H, ZHANG M, MUJUMDAR A S, et al.Comparison of drying characteristic and uniformity of banana cubes dried by pulse-spouted microwave vacuum drying,freeze drying and microwave freeze drying[J]. Journal of the Science of Food and Agriculture,2014,94(9):1 827-1 834.
[13] ANTAL T.Comparative study of three drying methods: freeze,hot air-assisted freeze and infrared-assisted freeze modes[J]. Agronomy Research 2015,13(4): 863-878.
[14] ORAK H, AKTAS T, YAGAR H, et al.Effects of hot air and freeze drying methods on antioxidant activity,colour and some nutritional characteristics of strawberry tree (Arbutus unedo L.) fruit[J]. Food Science and Technology International,2012,18(4):391-402.
[15] CUI Z W, LI C Y, SONG C F, et al.Combined microwave-vacuum and freeze drying of carrot and apple chips[J]. Drying Technology,2008,26(12):1 517-1 523.
[16] ZHOU B, ZHANG M, FANG Z, et al.A combination of freeze drying and microwave vacuum drying of duck egg white protein powders[J]. Drying Technology,2014,32(15):1 840-1 847.
[17] 叶晓梦. 铁棍山药冻干-微波真空联合干燥工艺研究[D]. 石河子: 石河子大学,2014.
[18] JIANG N,LIU C,LI D, et al.Evaluation of freeze drying combined with microwave vacuum drying for functional okra snacks: antioxidant properties,sensory quality,and energy consumption[J]. LWT - Food Sci Technol,2017,82: 216-226.
[19] PEI F,SHI Y,GAO X,et al.Changes in non-volatile taste components of button mushroom (Agaricus bisporus) during different stages of freeze drying and freeze drying combined with microwave vacuum drying[J]. Food Chem,2014,165: 547-554.
[20] PEI F,SHI Y,MARIGA A M,et al.Comparison of freeze-drying and freeze-drying combined with microwave vacuum drying methods on drying kinetics and rehydration characteristics of button mushroom (Agaricus bisporus) slices[J]. Food Bioprocess Technol,2014,7(6): 1 629-1 639.
[21] HUANG L L,QIAO F,FANG C F.Studies on the microstructure and quality of iron yam slices during combined freeze drying and microwave vacuum drying[J]. Journal of Food Process Pres,2015,39(6): 2 152-2 160.
[22] HUANG L L,ZHANG M,WANG L P,et al.Influence of combination drying methods on composition,texture,aroma and microstructure of apple slices[J]. LWT-Food Sci Technol,2012,47(1): 183-188.
[23] HUANG L L,ZHANG M,MUJUMDAR A S,et al.Comparison of four drying methods for re-structured mixed potato with apple slices[J]. Journal of Food Eng,2011,103(3): 279-284.
[24] ABBASI S,MOUSAVI S M,MOHEBBI M.Investigation of changes in physical properties and microstructure and mathematical modeling of shrinkage of onion during hot air drying[J]. Iranian Food Science and Technology Research Journal,2011,7(1): 92-98.
[25] 麦润萍,冯银杏,李汴生. 基于分形理论的预冻温度对冻干猕猴桃片干燥特性及品质的影响[J]. 食品与发酵工业,2018,44(12):155-160;165.
[26] HUANG L L,ZHANG M,MUJUMDAR A S,et al.Studies on decreasing energy consumption for a freeze-drying process of apple slices[J]. Dry Technol,2009,27(9): 938-946.
[27] VEGA-GALVEZ A,AH-HEN K,CHACANA M,et al.Effect of temperature and air velocity on drying kinetics,antioxidant capacity,total phenolic content,colour,texture and microstructure of apple (var. Granny Smith) slices[J]. Food Chem,2012,132(1): 51-59.
[28] MONTEIRO R L,LINK J V,TRIBUZI G,et al.Effect of multi-flash drying and microwave vacuum drying on the microstructure and texture of pumpkin slices[J]. LWT-Food Sci and Technol,2018,96: 612-619.
[29] DUAN L L,DUAN X,REN G Y.Structural characteristics and texture during the microwave freeze drying process of Chinese yam chips[J]. Dry Technol,2020,38(7):928-939.
[30] DUAN X,HAN H,DENG R.Drying treatments on Chinese yam (Dioscorea spp.) prior to wet milling influence starch molecular structures and physicochemical properties[J]. Food Hydrocolloids,2020,102: 105 599.
[31] LIU Y H,ZENG Y,HU X Y,et al.Effect of ultrasonic power on water removal kinetics and moisture migration of kiwifruit slices during contact ultrasound intensified heat pump drying[J]. Food Bioprocess Technol,2020,13(6): 430-441.
[32] WITROWA-RAJCHERT D,RZACA M.Effect of drying method on the microstructure and physical properties of dried apples[J]. Dry Technol,2009,27(7): 903-909.
