Abstract: Thermophysical properties of foods are of considerable relevance to food industry. The One among less explored thermophysical quantities is the thermal effusivity. In this paper the front variant of the photopyroelectric method was applied to determine thermal effusivity of both, fresh hen egg’s yolk and white as well as of their blends. The amount of egg yolk added to the blend affected the thermal effusivity of egg’s white. Thermal effusivity of mixtures containing pork meat and lard was also investigated. Addition of lard reduces significantly thermal effusivity of pork meat (the 1% increase of lard content leads to 6.93 Ws½m-2K-1 drop of thermal effusivity).
Keywords: thermal effusivity, photopyroelectric method, hen’s egg, pork meat, fat content
Abstract: Abstract. Banana discs of 1 cm thickness were immersed into different antioxidant solutions to slow down potentially disturbing discoloration during drying. Samples were randomly split into 8 groups according to the 2p experimental design. Two antioxidant solutions with 1.66% and 4.59% ascorbic acid, two levels of drying temperature with 50°C and 80°C, two levels of drying time with 6h and 8h were used or adjusted. Laser diodes of seven wavelengths (532, 635, 650, 780, 808, 850 and 1064 nm) were selected to illuminate the surface and light penetration pattern was evaluated on the basis of radial profiles. Profiles acquired at three wavelengths (532, 635 and 650 nm) were found to respond sensitively to adjusted parameters. As a result of drying, intensity decay was observed to move closer to incident point. Significant effect of temperature, drying time and their interaction was found on extracted descriptive attributes of intensity profiles: full width at half maximum (FWHM), distance of inflection point (DIP) and slope of logarithmic decay (SLD). Beyond their presence, antioxidant concentration was neutral factor without significant contribution to the model. Results were in agreement with reference spectroscopic measurements, especially with NDVI index. Promising results suggest that evaluated method might be suitable for monitoring purposes during drying of fruits.
Keywords: machine vision, digital image processing, laser backscattering, banana drying
Abstract: Heat pumps have been known to be energy efficient when used in conjunction with drying operations. The principal advantages of heat pump dryers (HPD) emerged from the ability of heat pumps to recover energy from the exhaust as well as their ability to control the drying gas temperature and humidity. The red grape grains were dried with and without treating by hot sodiumcarbonate solution in 3% concentrations. That osmotic treatment is necessary, because the grape grains have waxy layer in the skin which makes difficulties in the dehydration. The drying time was eight hours, till equilibrium weight. The received product has very low humidity (about 70 % dry base), which is already good for storage and stable from the viewpoint of microbiology. To control the effect of treatment not treated samples were also dried for 10 hours (technological time). The received material had smaller dry content about 37 %. Dielectric parameters (between 20Hz and 1MHz) were investigated in every hour. The aim of the experiment series was to see, if the method is useful to follow the drying process.
Keywords: impedance parameters, non-linear regression, drying trends, correlation matrix, gentle drying