This study analyzed the effects of thermohydrolysis on the anaerobic conversion efficiency of lignocellulosic biomass, comparing conventional and microwave heating methods. The research aimed to identify the optimal temperature and duration for biomass pre-treatment to maximize biogas output. Four temperatures (100 °C, 130 °C, 150 °C, and 180 °C) and six durations (10, 15, 20, 25, 30, and 40 min) were tested. The results showed that microwave heating increased biogas production compared to conventional heating at the same temperatures and durations. At 150 °C, microwave heating for 20 min produced 1184 ± 18 NmL/gVS of biogas, which was 16% more than the 1024 ± 25 NmL/gVS achieved through conventional heating. Statistically significant differences in biogas output between microwave and conventional heating were observed at 130 °C, 150 °C, and 180 °C, with the greatest difference recorded between 130 °C and 150 °C: 13% for conventional heating and 18% for microwave heating. Notably, increasing the temperature from 150 °C to 180 °C did not result in a statistically significant rise in biogas production. The energy balance analysis revealed that microwave heating, despite its lower efficiency compared to conventional heating, resulted in higher net energy gains. The most favorable energy balance for microwave heating was observed at 150 °C, with a net gain of 170.8 Wh/kg, while conventional heating at the same temperature achieved a gain of 126.2 Wh/kg. Microwave heating became cost-effective starting from 130 °C, yielding an energy surplus of 18.2 Wh/kg. The maximum energy output from microwave conditioning was 426 Wh/kg at 150 °C, which was 158 Wh/kg higher than conventional heating. These findings suggest that microwave thermohydrolysis, particularly at 150 °C for 20 min, enhances both biogas production and energy efficiency compared to conventional methods. The results highlight the potential of microwave pre-treatment as an effective strategy to boost methane fermentation yields, especially at temperatures above 130 °C.

A simplified model was proposed to describe the drying kinetics of wet solids. The model was validated on the basis of measurements of drying kinetics parameters of raw and blanched carrot cubes and raw potato cubes dried by convection with hot air (50-90 degrees C). The model values matched the exptl. data well for all drying time intervals. The proposed model was simpler and easier to use than theoretical or other multi-parametric empirical models and can be used to calculate the total drying time and to det. changes in the moisture content and drying rate of solid food materials.

Wydawnictwo SIGMA-NOT wydaje czasopisma fachowe informujące swoich czytelników o najnowszych osiągnięciach naukowych i nowoczesnych rozwiązaniach technicznych w Polsce i na świecie, popularyzuje problemy techniczne oraz poszerza wiedzę i kulturę techniczną.

This article describes a method for analyzing and modeling a complex agrotechnological system using the example of an industrial grain drying line. Elements of graph theory were used to develop an effective tool for modeling such a system and to formally validate its structure. The proposed method can be applied to transform a general structural model into a set of relational models, to formally evaluate the resulting models’ functionality, and to comprehensively analyze different variants of the process. The method can be deployed at the stage of designing and operating an industrial grain drying line, and it can also be adapted for use in other areas, such as processing lines in the agri-food industry.

Convective cereal grain drying is an energy-intensive process. Mathematical models are applied to analyze and optimize grain drying processes in different types of dryers and in different stages of drying to improve final grain quality and reduce energy consumption. The aim of the present study was to develop a generalized mathematical model of the grain drying process that accounts for all drying stages, including loading and unloading of unprocessed grain, drying, and cooling of dry grain. The developed mathematical model is a system of algebraic equations, where the calculated coefficients are determined by the thermophysical and diffusive properties of dried grain. The model was validated for batch drying of wheat, canola, and corn grain, as well as continuous flow drying of wheat grain. The results were compared with published findings. The relationships between energy consumption during drying and drying time vs. air temperature at the dryer inlet and air stream volume were determined. Dryer capacity and drying conditions specified by the manufacturers, as well as loading and unloading capacity, were considered during batch drying. Continuous flow drying simulations were conducted in counter-flow, parallel-flow, and cross-flow mode. Simulation results indicate that the proposed models correctly depicted process flow in both batch and continuous flow dryers.

The aim of the work was to provide accurate models for an evaluation of a potato starch colloid properties based on fast ultrasonic tests. All measurements were performed considering five temperatures (20, 25, 30, 35 and 40 degrees C) of colloids with a starch concentration from 1 to 5%. In these conditions, density of studied colloids was determined, and ultrasound signals transmitted through them were registered. Based on the ultrasonic measurement, the sound velocity was determined. Results of these measurements were used to derive several empirical models. These models allow, for example, to perform rapid calculations of potato starch colloid density at a given temperature based on the sound velocity measurement with a relative error of 0.15% or even 0.09% for specific frequency (10 MHz), which is the highest accuracy of considered methods. Findings of this work can be implemented in industrial devices used for real-time on-line monitoring of technological processes. (C) 2020 Elsevier Ltd. All rights reserved.

A sophisticated relationship between strain rate and stress in plant tissues subjected to mechanical loads reflects the structural complexity and properties of biological tissues. The aim of this study was to develop a mathematical model explaining the above relationship. A simplified, non-linear rheological model of a cellular solid characterised by elastic cell walls and the presence of incompressible fluid in cells was developed. In this model, changes in tissue deformation are determined by the elasticity of the cell wall, the ratio of cell wall thickness to cell diameter, the flow resistance coefficient and tissue porosity. Plant materials (discs cut out from fresh sugar beet roots, celery roots and potato tubers) were analysed to verify the model's adequacy. The developed model indicates that in samples with a constant volume during compression, stress in compressed tissue is determined not only by strain and strain rate, but also by the cellular structure and the shape of the sample. Further research is needed to test the model in other types of materials. The model should also be analysed for its sensitivity to cell size and shape, and the morphological structure of biological tissues.

The most popular mathematical models for analyzing the rheological properties of liquid, semi-solid and solid foods were presented. Mechanical tests play an important role in empirical evaluations of the rheological properties of raw materials and food products. Raw materials and food products have liquid, semi-solid and solid consistency. A stress relaxation test is an alternative method for evaluating creep compliance, and it can also provide valuable information about the viscoelastic properties of food. The main emphasis was placed on the rheological models of solid foods. The existing rheological models of solids have several weaknesses, in particular when they are used to describe the results of creep and stress relaxation tests of foods with a cellular structure. The structure of food materials can undergo various changes during processing due to the influence of external factors. Rheological models describing the free flow of liquid and semi-solid foods cannot be used to determine the viscoelastic properties of solid foods and liquids.

Professor Stanisław Pabis passed away suddenly on September 13, 2019, at the age of 94. We lost an outstanding scientist in the field of Biosystems Engineering who founded the scientific school of methodology of empirical sciences and who made a significant contribution to the development of systems engineering in agriculture and food processing.

The aim of this study was to determine the compression characteristics of nonhomogeneous plant materials with a complex morphological structure (beetroots, celery roots, and potato tubers), to compare the analyzed samples with the compression characteristics of reference materials (homogeneous isotropic structural materials: steel coil spring and vulcanized rubber), and to determine the influence of the compression rate on stress in compressed samples. Structural materials and plant materials clearly differed in compression characteristics. Excluding the short initial compression phase, the compression curves for the steel coil spring and vulcanized rubber were straight parallel lines, and the higher the crosshead speed, the higher the lines' location in the diagram. In tests conducted on plant materials, the rate of changes in compression force increased throughout the experiment with an increase in crosshead speed. The greatest variations in compression force resulting from differences in crosshead speed were observed in potato samples. The apparent retardation times determined in the developed rheological model ranged from 0.079 s for the steel coil spring to 6.863 s for potatoes.

The aim of this study was to evaluate the effect of convective and cryogenic freezing, hot air convective drying (HACD) at 60, 70, 80, and 90 degrees C and microwave vacuum drying (MWVD) at 100, 150, 200, 300, 450, and 500 W on the drying kinetics and texture of whole cranberries. Effective moisture diffusivities and drying rates were higher, whereas drying times were shorter for the samples dried by MWVD compared with the samples processed by HACD. The drying kinetics of cranberries during MWVD was discussed based on the hypothesis postulating that changes in the drying rate of cranberries during MWVD can be explained by and correlated with changes in the pressure gradient on material surface. Cranberries processed by MWVD were characterized by significantly greater hardness, gumminess, and chewiness in comparison with HACD samples. MWVD was found to be an effective method for producing dried snacks characterized by hard and crispy texture and considerable resistance to stress associated with manufacturing, packaging, storage, and delivery. HACD produced brittle fruit that were difficult to store and transport and were not fully suitable for direct consumption. Convective freezing before MWVD improved the overall appearance of cranberries, whereas cryogenic freezing combined with high temperature HACD adversely influenced the drying rate and produced dried cranberries with suboptimal overall appearance.

The objectives of this study were (i) to evaluate moisture loss (ML), solids gain (SG), moisture loss rate (d(ML)/dt), solids gain rate (d(SG)/dt), effective moisture diffusivity (D-eM ), and effective solids diffusivity (D-es) during osmotic dehydration (OD), ultrasound-assisted osmotic dehydration (UA-OD), and osmotic dehydration of whole cranberries, preceded by microwave-vacuum pretreatment (MV + OD) or freezing/thawing treatment (F + OD ) and (ii) to use a mathematical model to predict moisture content MI infinity and solids content SG(infinity) in equilibrium state and the distribution of moisture and sucrose in whole cranberries during dehydration. Microwave-vacuum and OD treatments produced cranberries with the highest values of ML and SG (39.7 and 8.4 g 100 g fresh fruit(-1) , respectively), d(ML)/dt and d(SG)/dt (76.9 and 8.5 h(-1), respectively), D-eM and D-es (6.1 and 3.7 x 10(-10) m(2) s(-1), respectively). Azuara's and Peleg's models adequately described the OD kinetics of whole cranberries in terms of ML and SG. The results indicate that the equilibrium values of ML infinity and SG(infinity) were not reached under the conditions specified in the present study.

This study analyzed the influence of temperature on the thermal conductivity and thermal capacity of kefir grains during heating and cooling in the temperature range between 3 and 30 degrees C. The correlations between the thermal conductivity vs temperature of kefir grains during heating differed from those observed during cooling. During heating, the thermal conductivity of kefir grains decreased from 0.46 to 0.40Wm(-1) K-1 according to the Arrhenius law. During cooling, the thermal conductivity remained stable at 0.36 +/- 0.03 W m(-1) K-1. The observed differences in the behavior of thermal conductivity of heated and cooled kefir grains could be related to the stimulating impact of heat on microbial activity inside the grains. The maximum thermal capacity of 3776 J kg(-1) K-1 was noted at 9.3 degrees C and the minimum thermal capacity of 2987 J kg(-1) K-1, -at 30.0 degrees C. In-depth knowledge of the thermal properties of kefir grains can contribute to improving their efficiency and optimizing the kefir production process. (C) 2017 Curtin University of Technology and John Wiley & Sons, Ltd.

The aim of this study was to compare the effectiveness of microwave-vacuum pretreatment conducted at 100, 500 and 800 W on the drying kinetics of whole cranberries (Vaccinium macrocarpon) during hybrid osmotic and microwave-vacuum drying. Additionally, the effect of microwave-vacuum pretreatment and subsequent osmo-microwave-vacuum drying on selected quality indicators of dried cranberries, including phenolic content, antioxidant activity and color, was studied, and the quality of samples was compared with freeze dried, microwave-vacuum dried and osmo-microwave-vacuum dried samples. Irrespective of microwave power, the initial pretreatment accelerated mass transfer during osmotic dehydration of cranberries, and the Weibull model well fitted the experimental data. Final microwave-vacuum drying of cranberries was a two-stage process involving a relatively long phase with a constant drying rate, followed by a short period with a decreasing drying rate. Microwave-vacuum and osmo-microwave-vacuum drying resulted in similar retention of polyphenols and similar antioxidant activity, both of which were relatively higher than in freeze-dried cranberries. However, microwave-vacuum pretreatment at low microwave power (100 W) before dehydration also resulted in high retention of phenolic compounds, high antioxidant activity and attractive color, which were consistent with the high content of total anthocyanins and flavonoids. Microwave-vacuum, osmo-microwave-vacuum and osmo-microwave-vacuum drying combined with microwave-vacuum pretreatment at low microwave power (100 W) were the most suitable methods for the production of high-quality dried whole cranberries.

The aim of this study was to compare the thermal properties of cranberry fruits measured with a thermal probe with the values calculated based on the chemical composition of raw, hot air convective dried (HACD, 80 degrees C) and microwave-vacuum dried (MWVD, microwave power density of 0.75 Wg(-1), absolute pressure of 4-6 kPa) cranberry fruits. The influence of the drying technique on the thermophysical properties of cranberries was also evaluated. Dried cranberries were characterised by lower values of thermal conductivity and specific heat, and higher thermal diffusivity than raw fruits. The measured values were as follows: thermal conductivity - 0.248, 0.066 and 0.054 W m(-1) center dot K-1, specific heat - 3509, 2288 and 1922 J kg(-1) K-1 for raw, HACD and MWVD cranberries, respectively. The respective calculated values were as follows: thermal conductivity - 0.231, 0.068 and 0.053 W m(-1)center dot K-1, specific heat - 3709, 1922 and 1953 J kg(-1) K-1. The measured values of thermal diffusivity were 1.06 x 10(-7),1.08 x 10(-7) and 1.23 x 10(-7) m(2) s(-1), whereas the calculated values were 1.22 x 10(-7),1.54 x 10(-7) and 1.37 x 10(-7) m(2) s(-1) for raw, HACD and MWVD fruits, respectively. (C) 2017 Elsevier Ltd. All rights reserved.

In this study, an attempt was made to modify the existing ultrasound method (two-velocities method, TVM) for estimating the proximate chemical composition of meat products by replacing one of the two sound velocity measurements with a measurement of product density at the same temperature (velocity-density method, VDM). Both methods were used to determine the chemical composition of the same five batches of three selected meat products made in Poland: pork canned ham, pork ‘Krakowska’ sausage and pork ‘Podwawelska’ sausage. In all three products, the mass percentage of every ingredient determined by TVM differed significantly from the results of chemical analysis, whereas the mass percentage estimated by VDM did not differ significantly from the results of chemical analysis in any of the tested products. The study proposes a new, more accurate method for determining the proximate chemical composition of meat products. The method relies on measurements of product density, but it eliminates the need for measuring sound velocity at two different temperatures.

The study was performed to examine whether the chemical composition of processed meats can be identified based on their rheological properties. The analyzed material comprised ten types of pork and poultry cold cuts supplied by renowned manufacturers and available throughout Poland. The rheological properties of cold cuts were derived using a nonlinear rheological model and correlated with the results of proximate chemical analysis. An analysis of processed meats did not show correlations between variations in their rheological properties and proximate chemical composition versus production date. However, the results of proximate chemical and rheological analyses supported the identification of the evaluated products. Both methods produced similar results only when the type of product or raw materials were known. The rheological properties of the analyzed processed meat products supported the identification of their protein, ash and dry matter content, but could not be used to estimate their collagen and fat content with satisfactory precision.PRACTICAL APPLICATIONSThe manuscript presents an attempt to develop a mathematical model describing the rheological properties of the analyzed material, including the elastic modulus, consistency index, flow index and flow limit, which are not dependent on the stress relaxation tests used to establish those values. We also described an approach to the identification of protein, ash and dry matter content of sausages based on rheological data, and correlations between rheological/mechanical measurements and the chemical composition of meat products. The indirect method for identifying the proximate chemical composition of processed meat products based on their rheological properties poses an alternative to laborious and timeconsuming analytical techniques, and it can be used to design a simple measuring device. The proposed methodological approach can have important implications for both industrial practice and research.

The aim of this study was to determine the effect of: (a) different drying methods, (b) hot air temperature in a convection oven, and (c) the moisture content of fruits dehydrated by multi-stage drying which involves a transition between different stages of drying, on the rehydration kinetics of dry blueberries. Models describing rehydration kinetics were also studied. Blueberries dehydrated by multi-stage microwave-assisted drying, which involved a hot air pre-drying step at 80 °C until the achievement of a moisture content of 1.95 kg H2O kg(-1)DM, were characterized by significantly higher rates of initial and successive rehydration as well as smaller initial loss of soluble solids in comparison with the samples dried by other methods. The highest initial rehydration rate and the smallest loss of soluble solids after 30 min of soaking were determined at 0.46 min(-1) and 0.29 kg DM kg(-1)DM, respectively. The Peleg model and the first-order-kinetic model fit the experimental data well.