title: Comparison of different drying methods on the physical properties, bioactive compounds and antioxidant activity of raspberry powders.
abstract: BACKGROUND
  Dehydration has been considered as one of the traditional but most effective techniques for perishable fruits. Raspberry powders obtained after dehydration can be added as ingredients into food formulations such as bakery and dairy products. In this study, raspberry powders obtained by hot air drying (HAD), infrared radiation drying (IRD), hot air and explosion puffing drying (HA-EPD), infrared radiation and microwave vacuum drying (IR-MVD) and freeze drying (FD) were compared on physical properties, bioactive compounds and antioxidant activity.
  
  
  RESULTS
  Drying techniques affected the physical properties, bioactive compounds and antioxidant activity of raspberry powders greatly. FD led to significantly higher (P < 0.05) values of water solubility (45.26%), soluble solid (63.46%), hygroscopicity (18.06%), color parameters and anthocyanin retention (60.70%) of raspberry powder compared with other drying methods. However, thermal drying techniques, especially combined drying methods, were superior to FD in final total polyphenol content, total flavonoid content and antioxidant activity. The combined drying methods, especially IR-MVD, showed the highest total polyphenol content (123.22 g GAE kg(-1) dw) and total flavonoid content (0.30 g CAE kg(-1) dw). Additionally, IR-MVD performed better in antioxidant activity retention.
  
  
  CONCLUSIONS
  Overall, combined drying methods, especially IR-MVD, were found to result in better quality of raspberry powders among the thermal drying techniques. IR-MVD could be recommended for use in the drying industry because of its advantages in time saving and nutrient retention.
authors.affiliation: Institute of Agro-products Processing Science and Technology, Chinese Academy of Agricultural Sciences/Key Laboratory of Agro-products Processing, Ministry of Agriculture, Beijing, 100193, China.
authors.forename: Xu
authors.initials: X
authors.lastname: Si
authors.affiliation: Institute of Agro-products Processing Science and Technology, Chinese Academy of Agricultural Sciences/Key Laboratory of Agro-products Processing, Ministry of Agriculture, Beijing, 100193, China.
authors.forename: Qinqin
authors.initials: Q
authors.lastname: Chen
authors.affiliation: Institute of Agro-products Processing Science and Technology, Chinese Academy of Agricultural Sciences/Key Laboratory of Agro-products Processing, Ministry of Agriculture, Beijing, 100193, China.
authors.forename: Jinfeng
authors.initials: J
authors.lastname: Bi
authors.affiliation: Institute of Agro-products Processing Science and Technology, Chinese Academy of Agricultural Sciences/Key Laboratory of Agro-products Processing, Ministry of Agriculture, Beijing, 100193, China.
authors.forename: Xinye
authors.initials: X
authors.lastname: Wu
authors.affiliation: Institute of Agro-products Processing Science and Technology, Chinese Academy of Agricultural Sciences/Key Laboratory of Agro-products Processing, Ministry of Agriculture, Beijing, 100193, China.
authors.forename: Jianyong
authors.initials: J
authors.lastname: Yi
authors.affiliation: Institute of Agro-products Processing Science and Technology, Chinese Academy of Agricultural Sciences/Key Laboratory of Agro-products Processing, Ministry of Agriculture, Beijing, 100193, China.
authors.forename: Linyan
authors.initials: L
authors.lastname: Zhou
authors.affiliation: Institute of Agro-products Processing Science and Technology, Chinese Academy of Agricultural Sciences/Key Laboratory of Agro-products Processing, Ministry of Agriculture, Beijing, 100193, China.
authors.forename: Zhaolu
authors.initials: Z
authors.lastname: Li
mesh_terms: D000872:Anthocyanins / Q000737:chemistry; D000975:Antioxidants / Q000737:chemistry*; D003116:Color; D003890:Desiccation / Q000379:methods; D005511:Food Handling / Q000379:methods*; D005638:Fruit / Q000737:chemistry*; D011208:Powders; D065856:Rubus / Q000737:chemistry*; D014867:Water / Q000737:chemistry*
chemical_list: D000872:Anthocyanins; D000975:Antioxidants; D011208:Powders; D014867:Water
keywords: antioxidant activity; combined drying; physiochemical quality; raspberry powder; single drying