Ufe 500

Cocoa shell samples were obtained after roasting fermented cocoa beans (West Africa mix supplied by Huyser, Möller B.V., Edam, Holland) at 135 °C for 55 min in custom made roaster (Metal workshop “ILMA”, Požega, Croatia). After that, the cocoa shell was easily separated by hand from the cotyledon.
Untreated cocoa shell (UCS) sample was obtained by grinding cocoa shell attained after separation from the cotyledon. Control samples were obtained by mixing the unmilled cocoa shell in water for 15, 30 and 45 min at concentrations of 1.5% and 3.0%. After mixing, the shell was separated from water and dried in the laboratory oven (Memmert, UFE 500, Schwabach, Germany) at 40 °C. Dry samples were ground in the laboratory mill (IKA, M20, Staufen, Germany) (25 g for 2 min with cooling) to obtain a fine powder (composite sample obtained by repeated grinding) and as such were frozen and stored for analyses. The grinded untreated cocoa shell was also frozen and stored for analysis in the same way as a cocoa shell mixed in water.

The control drying was done in electric oven (UFE 500 type, Memmert, Germany) with stable temperature 60°C and air relative humidity 16.2%. The solar drying was conducted in SD installed in the campus of RUA in Phnom Penh, 2013. The drying system was classified to be of the natural convection direct type. A picture of the solar dryer is shown in Figure 1. The solar dryer consisted of a solar air heater collector, drying chamber with drying trays and a blower, connected to the top of the drying chamber. The collector width, length, and depth were 1.50 m, 1.47 m, and 0.12 m, respectively. The solar collector array consists of a solid transparent plastic cover, an insulator, and a black painted aluminum absorber. Air enters into the drying chamber trough the collector by natural convection mode. The chamber dimensions are 1.50 m long, 0.60 m wide, and 1.10 m tall.

Five defect-free boards of Norway spruce (Picea abies Karst. L.) wood with a length of 40 cm and a width of 25 cm were machine-milled to a thickness of 1 cm, and then were used in the experiment. Initially, the boards were dried at 100 °C ± 3 °C to the oven-dry state, and subsequently, four of them were thermally modified at 160 °C, 180 °C, 200 °C, or 220 °C for 4 h at atmospheric pressure in a drying oven (Memmert UFE 500, Schwabach, Germany).
From the reference and four TM boards specimens were prepared with the dimensions of 80 mm × 20 mm × 5 mm (longitudinal × radial × tangential). No knots, splits, checks, or other non-homogeneity occurred in the specimens. Deflection between the growth rings and the cross-sectional areas of the specimens ranged from 30° to 90°. Finally, the areas determined for gluing were sanded using 120-grit sandpaper.
All wood specimens were conditioned at 20 °C ± 2 °C and 65% RH for 21 days to achieve equilibrium moisture content before their gluing, which ranged from 6.7 to 11.8%, depending on the modification temperature, i.e., 11.8% for reference unmodified wood and 6.7% for wood thermally modified at 220 °C. Density of the sound spruce wood was 0.459 ± 0.018 g/cm³ and reduced to 0.426 ± 0.015 g/cm³ for wood TM at 220 °C.

The specimens for compression testing, thermal analysis, horizontal burn tests and morphology investigations were foamed in the small aluminum molds, which were treated with release agent and dried at room temperature for 10 min before use. A specific amount of 2.8 g—equal to a neat foam density of 0.3 g/cm³—plus added fillers of the dispersed resin-carbamate-flame retardant mixture was introduced into each mold. The closed molds were transferred into a laboratory oven UFE 500 (Memmert GmbH + Co. KG, Schwabach, Germany), which was preheated and set at 160 °C, for 90 min for foaming and curing. Figure 1 shows the molds used in this work. The specimens for testing were cut using a band saw (Fa. Metabowerke GmbH, Germany). For each specimen series, at least three specimens were produced for comparison.

Storage stability test: Microparticle (PPE-MD) powders and PPE (non-encapsulated) (100 mg) were transferred to clear glass vials (16 × 100 mm) and stored at 60 ± 1 °C in a forced-air oven (UFE 500, Memmert, Schwabach, Germany) with a controlled temperature and in the absence of light. To determine the anthocyanins’ kinetic degradation, the study was performed over four months for the PPE-MD microparticles and for 48 h for the PPE (non-encapsulated). Triplicate vials were withdrawn at specific times to determine AT content.
Kinetic analysis. The data were best fit by a first-order kinetic model according to Equation (6): $LnC=Ln{C}_0-kt$
where C₀ is the initial concentration of anthocyanin (mg anthocyanin/g), C is the anthocyanin concentration at time t, k is the degradation rate constant, and t is the storage time. The degradation rate constants (k) and correlation coefficient were obtained from the slope of a plot of the natural log of the percentage retention of anthocyanin vs. the time for the first order at each studied temperature (60 °C).
Color difference value (ΔE): ΔE was defined as Equation (7): $∆E=\sqrt{{\left(L^{*}-L\right)}^2+{\left(a^{*}-a\right)}^2+{\left(b^{*}-b\right)}^2}$
where L*, a*, and b* are the values of the samples at zero time and L, a, and b are the measured values of each sample at the final time.
The color parameters, L*, a*, b* were determined by a colorimeter (Ultrascan pro, Hunter Lab, Reston, VA, USA).