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Background: Orthosiphon aristatus is a traditional medicinal herb mostly used in Southeast Asia and which has many health benefits. Packaging types and storage temperatures were investigated in order to select the best conditions for producing high bioactive compounds (BC) from two kinds of dried O. aristatus leaves.; Results: Blanched leaves were vacuum packed in polypropylene (PP) and aluminum foil laminated with polyethylene terephthalate and polyethylene (PET/Al/PE) and dried in a freeze dryer (B_FD) or heat pump-assisted dehumidified dryer (B_HPD60) at 60 °C prior to storage at 15, 25 and 35 °C for 6 months. Leaves in PET/Al/PE bags had higher total phenolic content (TPC), antioxidant activity (AOA) and BC than in PP bags (P ≤ 0.05). Storage at 15 °C retained the highest TPC and AOA in PET/Al/PE bags (P ≤ 0.05). The degradation kinetics for BC, sinensetin and eupatorin followed first-order kinetics. Half-lives (t1/2 ) for BC in PET/Al/PE were higher than in PP and were the highest at 15 °C for both packaging types.; Conclusions: Low temperature and PET/Al/PE bags provided the highest bioactive compound retention. The dried leaves from B_HPD60 and packed in PET/Al/PE bags had higher resistance to degradation of sinensetin than B_FD in PP bags. © 2018 Society of Chemical Industry.; © 2018 Society of Chemical Industry.

The stage of maturity for Orthosiphon aritatus (OA) leaves revealed that stage I (young leaves) provided the highest bioactive compounds. Vacuum blanching (VB) for 75 s gave the highest sinensetin ...

Thunbergia laurifolia leaves were dried by freeze drying (FD) and microwave heat pump dehumidified air drying (MHPD). The dried leaves were stored in polypropylene (PP) or aluminum laminated pouches (ALP) at 15, 25 or 35 °C and 60% RH. The samples were held for 180 days to observe changes in moisture content, color, total phenolics, antioxidant activity, catechin and caffeic acid. In general, samples in PP had a greater increase in moisture. Total phenolics content and ferric-reducing antioxidant power values increased for 120 days, then decreased thereafter. After 180 days, both FD and MHPD samples packaged in ALP and stored at 15 °C had the greatest total phenolics, antioxidant activity and bioactive compounds amongst the storage conditions. The first-order equation best described degradation behavior of catechin and caffeic acid for both drying technologies investigated.

BACKGROUND Dried Thunbergia laurifolia leaves are usually prepared using tray drying, resulting in products that have lost substantial amounts of bioactive compounds and antioxidant activity. The maturity of the raw material, blanching techniques and drying methods were investigated in order to select the best condition to produce high qualities of dried T. laurifolia leaves. RESULTS The 1st stage of maturity was selected and steam-microwave blanching (SMB) for 4 min was adequate for blanching leading to the maximum recovery of bioactive compounds. The modified Halsey model was the best desorption isotherm model. A new drying model proposed in this study was the best to fit the drying curves as compared to five common drying models. Moisture diffusivities were increased with the increase of drying temperature when combining SMB and heat pump-dehumidified drying. Microwave heat pump-dehumidified drying (MHPD) provided the shortest drying time, high specific moisture extraction rate (SMER) and could reduce drying time by 67.5% and increase caffeic acid and quercetin by 51.24% and 60.89%, respectively. CONCLUSION MHPD was found to be the best drying method and provided the highest antioxidant activity and bioactive compounds content, high SMER and short drying time. © 2016 Society of Chemical Industry

Gac fruit (Momordica cochinchinensis L.) pulp is high in carotenoids and fiber; however, it is discarded during process. Both maturity stages of matured gac fruit could be used in the drying experiments. Gac fruit pulp was dried by different drying methods including tray drying (40–60 °C), heat pump-assisted dehumidified drying (40–60 °C), microwave drying (450–900 W), mixed-mode solar drying and freeze drying. The Modified Henderson model presented the best fit of desorption isotherms. New model proposed was the best drying model. Quality evaluation by β-carotene, lycopene, lutein, total phenolics and antioxidant activity revealed that heat pump-assisted dehumidified drying at 60 °C provided the highest lutein, total phenolics and antioxidant activity and could reduce drying time by 25 % and increased lutein, total phenolics and antioxidant activity by 12.6 %, 32.0 % and 0.3 %, respectively and is more promising drying method for gac fruit pulp.

The maturity of Thai sweet basil was based on leaf area, % inhibition and total phenolics. Desorption isotherms for sweet basil leaves were performed. It was found that the modified Henderson model showed the best fit to both fresh and blanched sweet basil leaves for Xe = f(Xe,T). Sweet basil leaves were pretreated by blanching prior to drying under three temperatures of 40, 50 and 60C in tray and heat pump-dehumidified (HPD) dryers. The three-parameter model was the most effective model in describing sweet basil leaf drying. The drying constant was related to air temperature using the Arrhenius model. Effective moisture diffusivities increased with increasing temperature and blanching treatment, as well as the HPD dryer. Quality evaluation by % inhibition, total phenolics, rehydration ratio and ΔE* showed that the best quality resulted from sweet basil leaves pretreated by blanching and dried at 40C in HPD dryer. PRACTICAL APPLICATIONS Tray drying of sweet basil leaves is commonly performed in many industries. Up to now, the exporters have faced the problem of low total phenolics and antioxidant activity in dried sweet basil leaves. The new methods proposed in this study are blanching and heat pump-dehumidified (HPD) drying. The results revealed that blanching incorporated with HPD drying could reduce drying time and increase total phenolics, antioxidant activity and color values compared with the conventional tray drying. The three-parameter model proposed in this work was the most effective model to describe the mass transport behavior of dried sweet basil leaves.

The maturity of ivy gourd leaves was based on total chlorophyll and chlorophyll a. Desorption isotherms for fresh and blanched ivy gourd leaves have been measured. A nonlinear regression program was applied to the experimental data to fit with any of the four moisture sorption isotherm models. The modified Henderson model gave the best fit. Ivy gourd leaves were pretreated by different blanching methods prior to drying under three temperatures of 50, 55 and 60°C in tray and heat pump–dehumidified dryer. The drying data were fitted to the modified Page model. The drying constant was related to air temperature using an Arrhenius model. Effective moisture diffusivities were determined using the drying data. The degradation of total chlorophyll followed first-order kinetics. Heat pump–dehumidified drying and blanching methods reduced drying times. Quality evaluation showed best quality for ivy gourd leaves pretreated by blanching with chemicals and dried at 50°C in a heat pump–dehumidified dryer.

The appropriate stage of maturity of Andrographis paniculata (AP) was selected based on the level of phytochemicals. Prior to drying, samples were blanched in boiling water. The Modified Halsey and Modified Henderson models offered the best fit of desorption isotherms for fresh and blanched AP, respectively. AP was dried in a tray dryer (TD) and heat pump-dehumidified dryer (HPD) at 40–60 °C; microwave dryer (MWD) at 270–720 W and freeze dryer (FD). Five mathematical models were fitted into the experimental data. The three-parameter model gave the best fit. The drying rate constant was related to the drying temperature using the Arrhenius model. Effective moisture diffusivity was increased with increase in drying temperature and microwave power. HPD and blanching increased antioxidant activity, total phenolics, andrographolide, and neoandrographolide by 1.45, 11.16, 6.31, and 23.57%, respectively. The blanching pretreatment followed by HPD should be considered for drying AP for its further utilization. Practical applications Andrographis paniculata (Burm.f.) Nees has been used in a traditional herbal medicine to treat the common cold, fever, and diarrhea. The active components of A. paniculata are very bitter diterpene lactones known as andrographolide and neoandrographolide found in the aerial parts but contained the maximum contents in leaf. The pretreatment followed by drying process may greatly influence the quality of A. paniculata leaves. Heat pump-dehumidified dryer (HPD) was adopted for dried A. paniculata in order to obtain dehydrated herb with high drying quality. The knowledge of drying kinetics was used to find the optimum point of the drying process for A. paniculata. The results of this study revealed that blanching followed by HPD could reduce drying time and increase phytochemical contents compared with commercial product and will be useful in the pharmaceutical products with good chemical properties.