Magdalena Kręcisz

A STUDY OF THE SOLUBILITY OF BIODEGRADABLE FOAMS OF THERMOPLASTIC STARCH

The paper presents the results of a study on the water absorption capacity and solubility of biodegradable starch foams produced with single-screw extruder TS-45 with L/D=12. Two different moulding dies were used: one with a circular hole with the diameter of 3 mm and one with a ring hole with the inner diameter of 5 mm. During the extrusion process, the temperature of the cylinder ranged from 80 to 130°C and the screw speeds applied were: 100 and 130 rpm. For the application of the ring die, it was observed that regardless of the speed of the screw, the use of the raw material of higher moisture content led to the production of materials with higher solubility. As a result, the obtained materials revealed solubility at a level of 40%. The results demonstrate good solubility of the starchy fillers of the packaging, which may indicate their susceptibility to decomposition in the conditions of high ambient humidity. A statistical analysis showed a significant impact of moisture of the raw material on the WSI of starch foams used irrespective of the other parameters of the extrusion-cooking process. The raw material moisture had a significant effect on the water absorption capacity of only TPS foams produced in the ring die at the screw speed of 100 rpm.

Effect of PVA and PDE on selected structural characteristics of extrusion-cooked starch foams

The aim of this work was to determine selected physical properties of biodegradable thermoplastic starch (TPS) filling foams manufactured by extrusion-cooking technique from different combinations of potato starch and two additives: poly(vinyl alcohol) PVA and Plastronfoam PDE. Foams were processed with seven starch/additives combinations at two different extruder-cooker’s screw rotational speeds. The densities of starch foams depended significantly on the additive type and content. The linear relationship between the Young modulus and the ultimate compression force and apparent density was found. The foams processed with the addition of PVA had low density, porosity and lower values of the Young modulus than the foams prepared with PDE.

Effect of processing conditions and concentration of water and milk suspensions on the dynamic viscosity of corn-cranberry gluten-free instant gruels

A b s t r a c t. Selecting the parameters of the extrusion-cooking process makes it possible to produce various types of extrudates with a certain density, expansion, water absorption capacity, stickiness, etc. Porridges and gruels for children are products in a loose form, obtained from rice, corn, rye, oat, barley, buckwheat, millet or wheat flour, that can be produced with conventional drumdrying but also with the application of extrusion-cooking. The aim of the study was to evaluate the effect of dried cranberries addition level and processing conditions of instant corn-cranberry gruels on the dynamic viscosity of solutions with various concentrations and liquid medium used. The results showed that increasing content of cranberries in the recipe resulted in an increase of the dynamic viscosity value of extruded gruels suspensions. Increasing the screw speed during processing caused a decrease in the dynamic viscosity of extruded gruels in the case of aqueous suspensions tested at 40°C. Increasing viscosity along with the increase of screw speed was observed in all milk suspensions. Increasing the temperature of water and milk suspensions caused a decrease in the dynamic viscosity values of extruded corn-cranberry instant gruels. Higher values of dynamic viscosity were observed in the case of suspensions prepared with milk. K e y w o r d s: extrusion-cooking, corn, cranberry, gluten-free, dynamic viscosity

Radical scavenging activity of instant gruels enriched with cranberry fruits determined by thin-layer chromatography—DPPH test and by spectrophotometric method

Natural compounds possess multiple biological properties, among others antioxidant activity. Phenolic compounds which exhibit excellent antiradical activity may act as scavengers of free radicals or prevent their formation. The main objective of the present research was the examination of the free radical scavenging activity of instant corn gruels with 0%, 1%, 3%, 5%, and 10% addition of dried cranberry fruits. The extrusion of gruels was carried out at varying rotational speeds of the plasticising system (80, 100, and 120 rpm). The study was developed using two methods: thin-layer chromatography—2,2-diphenyl-1-picrylhydrazyl (DPPH) test and spectrophotometric analysis. The findings confirm that the use of higher screw rotations during the extrusion entailed a higher antioxidant activity of the obtained extrudates. Also, a high activity was reported for the extruded corn gruels without additives. This, in turn, demonstrates an insignificant influence of the extrusion process on the biological value of the obtained products.

Energy Consumption and Selected Physical Properties of Corn-oat Instant Gruels Under Specific Extruder Configurations

The extrusion-cooking technique was used for the processing of corn-oat blends with three various screw configurations. The procedure involved the assessment of the effects of the processing conditions on energy consumption. The initial moisture level ranged from 16 to 22% and the screw speed applied during the processing varied from 80 to 120 rpm. Corn-oat gruels were tested for water absorption and bulk density. A significant effect was reported of the initial moisture and screw speed on energy demand as well as on the physical properties of extrudates. The use of the shortest version of the extruder requires more energy than with the longer ones. Corn-oat instant gruels processed with an elongated barrel showed lower water absorption compared with the shorter one. The most important parameter having an influence on the product quality was the initial moisture content of extruded blends. The obtained results can be helpful in management of sustainable settings, low-energy processing conditions and the proper characteristics of extruded instant corn-oat gruels.

Evaluation of selected properties of gluten-free instant gruels processed under various extrusion-cooking conditions

BACKGROUND For consumers suffering with gluten intolerance, the only way to manage the condition is to avoid foods which are high in gluten. Instant gruels, processed from gluten-free corn and rice by extrusion cooking, could be used as a ready meal both for children and for adults on a gluten-free diet. The aim of the study was to evaluate the effects of various processing conditions on selected characteristics of corn-rice instant gruels. METHODS Corn-rice mixtures (75:25 and 50:50) were processed at 12, 14, 16 and 18% of initial moisture content, using an extruder with screw speeds of 80, 100 and 120 rpm. Bulk density, water absorption and solubility, gel formation, color and sensory characteristics were assessed, under various pro- cessing conditions and with various corn:rice ratios. RESULTS The composition of the raw materials, initial moisture content and screw speed applied during processing affected the characteristics of the corn-rice extruded instant gruels. Increasing the amount of rice in the recipe from 25 to 50% resulted in decreased bulk density, water solubility, volumetric gel formation ability and b* value. Increasing the initial moisture content increased the bulk density, L*, a* and b* intensity, and gel formation index values of extrudates made with a 75:25 corn-rice recipe. Increased rpm increased extrudate solubility and water absorption, if the initial moisture content was higher than 14%. The highest scores for overall acceptability were found for milk suspensions of 75:25 and 50:50 corn-rice instant gruels processed at 12 and 14% of initial moisture content, at 120 rpm. CONCLUSIONS Corn-rice instant gruels can be successfully produced by extrusion-cooking. Variable param- eters, like the initial moisture content of raw materials or screw speed during processing significantly affected the properties of the products. An understanding of the effects of processing conditions on some qualities of extruded instant gruels allows more desirable products to be created. Moreover, the various components can be used for extruded products for consumers on gluten-free diets. Functional additives incorporated in the recipe to improve the nutritional value of the extrudates, which will be investigated in our upcoming research.

Energy consumption during produciton of corn extrudates in relation to the process parameters

Abstract The objective of the paper was to determine the impact of the rotational screw speed and the level of moisture of raw material on the efficiency and energy consumption of the extrusion-cooking process. Measurement of the extrusion-cooking process efficiency (Q) was carried out through determination of the extrudates mass and energy consumption was determined with the use of a specific mechanical energy (SME). Based on the research results it was found out that the factor which significantly decides on the measured values was a rotational screw speed. Along with the increase of this parameter the energy consumption and extrusion-cooking process efficiency increased during processing of corn grits. Extrusion-cooking process efficiency depended also on the level of moisture of raw material. At lower moisture of raw material the efficiency decreased along with the increase of the screw speed and above 18% of the moisture level it increased. Reverse relation was reported during testing the energy consumption of the extrusion-cooking process.