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Response surface methodology was employed to investigate the effects of drying temperature (15.0-45.0C), air velocity (1.00-2.00 m/s), moisture content at conversion point (40.0-60.0%) and microwave (MW) power (1.0-3.0 W/g) on the average drying rate (DR), specific moisture evaporation rate (SMER), total color difference (ΔE), rehydration ratio (RR) and shrinkage ratio (SR) of yacon dried by combined heat pump (HP) and MW methods. A central composite rotatable design was used to develop models for responses. The coefficients of determination R 2 of DR, SMER and ΔE were higher than 0.7. However, R 2 of RR and SR were 0.540 and 0.343, respectively. Based on response surface and desirability functions, the optimum conditions for combined HP and MW drying of yacon were drying temperature of 42.7C, air velocity of 1.69 m/s, moisture content at conversion point of 50% and MW power of 2.0 W/g. At this optimum point, DR, SMER and ΔE were 0.262 kgH2O/kg(d.b.)·h, 0.222 kg/kW·h and 23.59, respectively. PRACTICAL APPLICATIONSYacon are rich in essential amino acids, minerals and fructooligosaccharides (FOS). However, FOS hydrolyzation, browning and decay are the common phenomena during postharvest storage and transportation. Hybrid drying techniques are being developed to minimize weakness and maximize merits of different drying techniques to produce better quality of foodstuffs, reduce drying time, decrease energy consumption and increase drying efficiency. Therefore, response surface methodology was employed to investigate the effects of drying temperature, air velocity, moisture content at conversion point and MW power on the average DR, SMER, ΔE, RR and SR of yacon dried by combined HP and MW methods, and the optimum process conditions were determined to obtain the criteria of maximum DR and SMER, and minimum ΔE. This research will provide valuable information for industrialization of yacon dried by combined HP and MW methods.

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An intentional or inadvertent mixing of plant materials containing ephedrine alkaloids, especially Ephedra, is illegal. In order to better detect plant materials containing ephedrine alkaloids in export and smuggling, DNA barcoding combined with a TaqMan real-time PCR-based assay were used in this study. We collected 201 samples from 18 species belonging to four genera distributed in three families to amplify two barcoding markers, internal transcribed spacer 2 (ITS2) and psbA-trnH. 175 ITS2 sequences and 136 psbA-trnH sequences were obtained. Alignments and the neighbor-joining tree indicated that ITS2 showed a better discrimination of species than psbA-trnH. In addition, based on the sequence comparison of the ITS2 region from 18 species, three sets of primer/probes were designed using the real-time PCR assay platform. A sensitivity test showed the above primer/probe sets were specific and sensitive (as little as 0.0050 ng/μL target DNA) to identify species containing ephedrine alkaloids. Hence, the combination of novel DNA barcoding and the TaqMan real-time PCR-based technique are promising tools for the identification of plant materials containing ephedrine alkaloids. It is beneficial to standardize market circulation and detection of plant materials containing ephedrine alkaloids.