The study focuses on evaluation of the impact of moisture on the relaxation characteristics obtained through uniaxial compression of single wheat kernels. Polish soft wheat (c.v. Emika) at eight different moisture levels. i.e. 8, 10, 12, 14, 16, 18, 20, and 22% (wet basis) was used in the research. The experiments were made with the help of a Zwick Z020 universal machine. Individual wheat kernels were compressed with constant load value of 50 N between two flat plates. Relaxation time was equal to 300 seconds. Values of the relaxation decay parameter Y(t) were established for the determined relaxation time. Parameters k1and k2for the model presented by Peleg and Normand were also calculated. Compression work and deformation increased with the moisture rise from 5 to 25 mJ and 0.2 to 1.0 mm, respectively. An increase of kernels moisture caused the load at relaxation time as well as the decay parameter Y(t) to decrease. The values at 22% moisture were more than two times lower that corresponding 8% water level. Coefficients k1and k2decreased from 3.5 to 1.5, and from 53 to 13, respectively. A linear relation between the two model coefficients was observed. The impact of kernel moisture on the analyzed parameters was described in the form of regression equations.
CHARACTERISTICS OF BASIC PROPERTIES OF NEW THERMAL INSULATION MATERIAL DESIGNED FOR FROZEN FOOD PACKAGING
Autor
Dariusz Góral, Franciszek Kluza, Katarzyna Kozłowicz, Małgorzata Góral
Pages
11–18
Keywords
thermal conductivity, thermal insulation, material, packaging for frozen food, IR image
Abstract
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The new thermal insulation material readily biodegradable and cheap in production, provided for packaging of frozen food, make easier retaining of cold chain, has been proposed. Five different types of material which main component was the paper pulp has been studied. Density of materials, theirs thermal conductivity and thermal images of the packaging made of these materials with the frozen product inside as well as temperature distribution histograms of their surfaces were experimentally characterized. The lowest density was measured for pulp containing albumin of eggs. It was found that the lowest thermal conductivity characterized the pulp with the addition of NaHCO3 + lauryl alcohol ethoxylate + C6H8O7 and pulp with the addition of NaHCO3 and KC4H5O6. Thermal images of the packaging surfaces and histograms of surfaces temperature distribution goes to show a good thermal insulation properties of all samples.
apple shape, Bézier curves, method, mathematical model, model 3D
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This paper presents a proposal for the method of mathematical modeling of the shape of the apple using Bézier curves. Modeling selected apple varieties Ligol and Jonagored. The contour of the apple, which is the meridian described three connected Bézier curves. The basis for the contour the apples are their photographs in 10 changing positions at 36o and 99 Bézier curves arranged along meridians apples. Bézier curves approximating the meridians lying on the surface of apples are the 3D model. The proposal method using Bézier curves can be used for mathematical modeling of the shape of apples.
THE EFFECT OF APPLE MASH PRETREATMENT ON THE RHEOLOGICAL PROPERTIES AND JUICES EXTRACT
Autor
Kamil Wilczyński, Zbigniew Kobus, Rafał Nadulski
Pages
33–40
Keywords
viscosity, apple juice, pretreatment, rheological properties
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The aim of the study was to determine the rheological properties and extract of apple juices. Two varieties of apple were used: Idared and Golden Delicious. The measurements were made using rotational rheometer from Brookfield Engineering Laboratories: model LVDV-II + PRO using spindle working in the range from 20 to 90 rpm/min, changed every 10 rpm/min. Temperature during test was of 21°C. Additionally the soluble solid content in juice was determined. The results showed that freezing and thawing treatment of pulp changed the rheological behaviour of apple juice for both varieties. There was no influence of enzymatic liquefaction on rheological behaviour of obtained apple juice.
Strawberry fruits of dessert variety ‘Elsanta’ were frozen at diversified freezing rate at 4.9; 9.1 and 42.9 mm h-1 and freeze-dried under pressures of 20, 42, 57 and 70 Pa. Obtained lyophilisates were subjected to hardness study with the use of indenter in the form of cone. It was stated that increase of rate freezing of samples causes growth of hardness of obtained lyophilisates. Likewise, while decreasing pressure of freeze-drying process, hardness of lyophilisates increased.