This study investigated the turmeric drying characteristics and process parameters optimization for far‐infrared (FIR) radiation drying of turmeric. The initial moisture contents of the sliced wet turmeric samples were approximately 80 ± 0.12% (wb). The turmeric was exposed to 6.65, 5.97, 4.97, and 4.80 μm FIR radiation for 70, 30, 25, and 20 min, respectively. The moisture content and color (L*, a*, and b* values) of turmeric were measured during the experiment. The optimization experiments were conducted based on response surface methodology according to a central composite design with two independent variables: exposure time and FIR wavelength. The dependent variables considered were moisture content, curcumin content, energy consumption, and color‐changing index. The final moisture content and curcumin content were reduced with decreasing FIR radiation wavelength. FIR radiation drying of turmeric was observed to be a falling rate process. The optimal conditions were obtained with the FIR wavelength of 5.51 μm and exposure time of 21 min by applying the desirability function method. Under the optimal conditions, the predicted values of response variables, curcumin content, color‐changing index, energy consumption, and final moisture content were 3.26% (dry weight), 13.29, 2.51 kWh/g water, and 10.25% (wb). The desirability of 0.8157 under the optimal conditions further confirmed the validation of models. The results concluded that the FIR radiation could effectively apply for drying turmeric. Practical Applications The far‐infrared radiation can be applied for turmeric drying on an industrial scale. The drying rates and color‐changing index of turmeric increased with decreasing far‐infrared wavelength and increasing far‐infrared exposure time. Curcumin was reduced by increasing the far‐infrared wavelength and far‐infrared exposure time. The wavelength of 5.51 μm and exposure time of 21 min was the optimal conditions for FIR drying of turmeric. Therefore, the industry can achieve the optimum quality of turmeric within a shorter period of time by applying this technique.

BACKGROUND: Chili is hygroscopic and needs a fast-drying method before feeding into pulverizers. The far-infrared radiation (FIR) roasting technique provides various benefits, such as higher drying rates within a short duration, reduction of mycotoxins, and improvement in the textural quality of agricultural produce. In addition, thin-layer modeling supports understanding the drying kinetics of agricultural produce. Therefore, the objective of this research was to study the thin-layer drying characteristics and color of whole chili pod and its components (i.e. seeds, pedicel, and placenta) of sun-dried chili during FIR roasting. The samples were dried at 7.76 ∼m (100 °C), 6.12 ∼m (200 °C), 5.056 ∼m (300 °C), and 4.30 ∼m (400 °C) by exposing them to FIR in a single layer and the drying kinetics were studied using the Midilli model. Further, the color variation during FIR roasting was studied.RESULTS: FIR roasting of chili pods and their components (i.e. seeds, pedicel, and placenta) shows a falling rate drying period at each wavelength. The moisture content decreased with decreasing FIR wavelength. The ΔE values for pods, pedicel, and placenta were increased during FIR roasting. The Midilli model results in R 2 and root-mean-square error value ranges of 0.7563-1.000 and 5 × 10 −8 -0.1238 respectively for the current study. The Midilli model at 300 °C shows that the FIR has minor variation compared with other FIR temperatures.CONCLUSION: FIR technology can be implemented to roast chili pods and their components (i.e. seeds, pedicel, and placenta) within a short period. Further, the application of FIR for roasting purposes desirably increases the color variation. The Midilli model can effectively describe the drying kinetics of the chili pods and their components during FIR roasting.

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Water use of a forest ecosystem is: nn important determinant of the water balance of a whole watershed. Kandyan Forest Gardens (KFGs) contain a mixture of different tree species. The different tree species are of different sizes and are arranged into distinct vertical canopy layers. The total water use of the KFG is determined by the transpiration rates of individual trees, which form these different vertical layers. The study was conducted in a KGF at Pilapitiya, Pilimathalawa in the Mid-Country Wet Zone (WM3) during the period from Marci to July 2001. A vegetation survey showed that there were 56 tree species in this KFG. Out cf these, three tree species representing three vertical canopy layers were selected for continuous measurement of transpiration. These were Jak (Artocarpus heterophyIlus), toona (Toona ciliata) and Mahogany (Swietenia macrophylla) which represented upper, middle and lower canopy layers respectively. Transpiration of all trees was measured as the sap flow in their trunks using two thermal methods. In jak (DBH = 40.5 ern) and toona (DBH=9cm), which had larger trunks, sap flow was measured using thermal dissipation probes. In mahogany, which had a smaller trunk (DBH=3cm), sap flow was measure using a dynagage. Solar radiation incident on the respe-ctive tree canopies were measured using tube solarimeters. Relative humidity in the open and inside the KFG was measured by two solid state humidity sensors. Soil moisture content at three soil depths (30, 60 and 120 em) was measured using theta probes. All measurements were done continuously at 30 second time intervals using a data logger. The data were averaged every 5 minutes and stored in the logger. Detailed continuous measurements taken during a n-hour period (i.e. from 0000 hours on 23.06.2001 to 2400 hours 25.06.20)1) were analysed. All three-tree species showed similar diurnal variation patterns in their S8P flow rates with maximum rates occurring between 1300 and 1400 hours. Sap flow rate of jak was significantly greater than those of toon a and mahogany, which did not differ significantly. However, the velocity of sap flow was highest in the smallest tree, i.e. mahogany, and decreased with increasing sap wood cross-sectional area. The daily transpiration rates oftoona and mahogany ranged from 19% to 27%. The incident solar radiation was highest on the upper canopy tree (i.e. jak), Both the middle canopy (toona) and lower canopy (mahogany) trees received similar levels of radiation because of the incomplete upper canopy cover in the KFG. There was a clear linear relationship between daily transpiration of all tree species and the solar radiation levels received by the respective trees. This relationship can be used to predict the daily water use of a given tree when there is no significant soil water deficit. The relative humidity (RH) under both open conditions and within the KFG showed a similar variation pattern. However, RH within the KFG was slightly higher than that in the open. Transpiration rates of all tree species had negative l...