Antonio Marsaioli

Study of a Microwave Assisted Vacuum Drying Process Applied to the Granulated Pharmaceutical Drug Hydrochlorthiazide (HCT)

Drying processes have evolved considerably over the years, aiming at the best conditions to shorten the processing time, but maintaining the highest final product quality. The application of vacuums to the microwave drying process might be interesting, especially for thermally sensitive products because the reduced boiling point of the solvent allows a lower temperature processing. The objective of the present work is to study and evaluate the process of drying a granulated product that is the basis of the drug hydrochlorthiazide, with an initial moisture content of 21% in dry basis. This study monitored the drying kinetics, product temperature and power absorbed by the sample using a bench scale vacuum microwave dryer. The equipment consisted of a cylindrical pressure vessel crossed by a wave guide, setting up a system whereby the vacuum pressure, the sample weight and the incident, reflected and residual microwave powers could be measured and evaluated, throughout the entire process. The experimental runs were established with an approximate incident microwave power at 20 W for absolute pressure levels of 50 and 75 mbar, working with samples of about 1.4 g. It was observed that the vacuum microwave process kinetics at both pressure levels showed little difference. The processes were carried out almost entirely in a regime of water evaporation, the product’s temperature remaining below the solvent boiling temperature. The drying times were similar for both processes, whereas the absorbed power was slightly higher at the pressure of 75 mbar.

Energy Analysis of Poly-hydroxybutirate (PHB) Drying Using a Combined Microwave/Rotating Pulsed Fluidized Bed (MW/RPFB) Dryer

The aim of this study was to investigate the drying kinetics and energy efficiency of a combined microwave/rotating pulsed fluidized bed (MW/RPFB) dryer to dry particles of poly-hydroxybutirate (PHB). In order to analyze the effects of microwaves and hot air conditions on the drying kinetics of PHB and energy efficiency, an experimental design technique was applied. Drying energy efficiencies were in the range of 12–30%, and an estimated value of 10.5% was found for pure convective drying of PHB in an RPFB with the same final moisture content.

Fragmentação mecânica de amêndoas de cupuaçu (Theobroma grandiflorum)

Cupuassu (theobroma grandiflorum) is a native fruit from the Brazilian Amazon region whose seeds suitably fermented, dried and roasted can be used to manufacture a product similar to chocolate. This work aimed at devising an alternative way of cracking the dried but not roasted kernels by using a roller crusher, followed by using a set of sieves for separating the fractions. The variables studied for determining the nibs (scrapped cotyledons) acquisition yield as well the purity of such material (expressed as percent of shell and embryo fragments) were the moisture of the whole kernel and the differential speed of the double rollers of the crusher. The results confirmed that the moisture of the whole kernel was the variable that most influenced the cracking of kernels. The greater yield obtainment of nibs was reached at the 5% moisture level of the whole kernels. The variation of the double rollers differential speed did not present any significant difference as regards the nibs acquisition yield. As to the percent values of shell and embryo fragments, no studied variables have shown any significant difference on such a response values, even so the results were very well satisfactory, presenting values below the 1.75%. The yield of this alternative process is 90% of the cotyledons acquisition from certain kernels mass. As a conclusion, the process proposed herewith set oneself up as a mechanized alternative, showing good nibs acquirement yield, and percent of shells and embryo below the tolerated value.

COMPARAÇÃO DAS PROPRIEDADES REOLÓGICAS DA MASSA DE CACAU TORRADA CONVENCIONALMENTE E POR MICROONDAS

Two kinds of roasting cocoa system: conventional batch method in electrical oven, and by microwaves, in a continuous microwave rotary applicator (2450MHz), were compared with respect to viscosity. Cocoa was roasted in whole beans and in nibs. The variable used in the microwave treatment was the power density applied to the whole beans (254,45 to 290,80 Wh/kg) and to the nibs (227,27 to 262,23 Wh/kg), with a constant holding time of 10 minutes. The variable used in the conventional roasting process was the roasting time of the beans (40 to 44 min) and the nibs (34 to 38 min), with constant temperature in the jacket of electric oven (150°C). Viscosity was measured in a Brookfield rheometer (mod RV-DVIII) at 40°C. In general, the plastic viscosity of the microwaved samples was lower than that of the conventional roasted samples. Also the nibs showed lower viscosities than the whole beans when roasted in the electric oven. The viscosity of the samples roasted in the microwave oven was lower in the whole beans than in the nibs. The product was sensorially evaluated by three experts in cocoa flavour, and it was shown that the flavour of the microwave roasted products was similar to that of the conventionally roasted products, with the advantage of a reduction in process time.