The paper presents the results of the research of the size and shape of parenchyma tissue cells in potato tubers depending on the direction and site of sampling in tubers. An optical confocal microscope was used to observe samples in their natural state. The investigation was carried out for 1 mm thick samples cut from cylindrical samples (10x10 mm) taken in two mutually perpendicular directions of the inner and outer core of each variety. The analysis was done ten times. The methods developed for the composition and image analysis ensure obtaining a sufficient number of cells to determine tissue structure parameters (surface, shape, elongation and number of cells per 1 mm(2)) and decays of these parameters were obtained. Statistical analysis was performed using the lambda- Kolmogorov-Smirnov compliance test. A relationship between the direction of sampling and the size and shape of the inner core of cells was found. Greater surface area and elongation of the inner core cells for the longitudinal direction in the tuber (stolon - top) was demonstrated. There was no such a correlation for the outer core in the tubers of the cultivars examined.

Bacterial cellulose alone, with pectin added and with both pectin and xyloglucan added were produced as models for plant cell walls. The artificial cell wall materials and natural apple tissue were treated with calcium and then subjected to tests of mechanical properties; a tension test for the artificial cell wall materials and a compression test for the apple tissue. It was found that pectin and xyloglucan had a significant effect on the mechanical properties of artificial cell wall materials, making them more extensible. A high concentration of calcium increased the failure strain and decreased the failure stress of these materials. Treatment of apple tissue with calcium had similar effects on the failure stress and the secant modulus, whereas the differences of failure strain and work to failure resulted in behaviour different from that of the artificial material.

A b s t r a c t. Cell walls are the major component of plant tissue which significantly influence on textural properties of fruit and vegetables. Geometrical dimensions of parenchyma cells are very small what makes impossible studying their mechanical properties in the natural state. An alternative is creating of a model artificial cell wall consisting of polysaccharides which imitate properties of the natural cell wall. Polysaccharides network based on bacterial cellulose supplemented with xyloglucan and pectin was proposed as the model cell wall. In this experiment, the nanostructure of the model and the natural cell walls on the basis of their atomic force microscope topographs was compared in order to evaluate correctness of methodology of production of artificial cell walls. It was demonstrated that the bacterial materials have very similar artificial structure to the natural cell walls. However, considering the chemical composition, the most suitable as the model is the BCPX material consisting of bacterial cellulose, pectin and xyloglucan. K e y w o r d s: nanostructure, cell walls, apple, model materials, atomic force microscope

Artificial plant cell walls were produced from bacterial cellulose and cell wall constituents. The artificial cell walls were stored at low, medium and high relative humidity, and then subjected to micro-mechanical tests. From chemical composition and microstructure analysis it was found that, among all artificial cell wall materials produced, the most representative analogue of natural apple cell wall was based on bacterial cellulose supplemented with xyloglucan and pectin. Uniaxial tensile tests revealed that the different cell wall materials differed in their mechanical properties; increasing the humidity during storage resulted in a decrease in the value of the secant modulus. The cell wall model material obtained may be used for the simulation of the effect of external factors on the physical and chemical properties of cell walls.

A b s t r a c t . A major quality problem for producers and consumers of apples is their softening during storage. This paper presents comparison of thre e methods for monitoring quality changes of apples during shelf-life storage: puncture test with acous tic emission and spatial-temporal speckle correlati on technique. Firmness, acoustic emission counts and cross-correlation coefficient difference obtained by these methods, respectively, were analysed. The par ameters show different correlation coefficients wit h time of storage. The highest correlation coefficien t was obtained by the non-destructive spatial-tempo ral correlation technique. Puncture test with acoustic emission shows also significant changes with time and these methods provide information about mechanical properties and especially about the fracture proper ties of the material. Higher correlation coefficien t between firmness and acoustic emission counts was obtained than between firmness and cross-correlatio n coefficient difference. The experiment has shown that for testing the quality of apples there is no difference related to the side of apples. K e y w o r d s : nondestructive method, biospeckle, acoustic emission, puncture

A b s t r a c t . Texture of apples depends on geometrical dimensions of the cellular mechanical skeleton. For quantitative measurements of the dime nsions of cells an image analysis procedure should be developed which is proper to a certain imaging s ystem. In this paper two different image analysis methods are applied: image segmentation and visual texture analysis (VTA) to images obtained by an optical microscope for which a special sample fixat ion procedure for apple tissue was developed. The image analysis was performed for thin sections of a pple, cut by microtome from samples previously subjected to different strain levels: intact tissue , 5%, 10% and 15%. The experiment showed that segmentation of images from the optical microscope is possible after prior manual correction of the images of apple, while visual texture analysis (VTA) provides quantitative results for the size and shap e of objects in the images automatically. The paramet ers obtained by the VTA correlate significantly with geometrical parameters obtained by the segmentation method. The highest correlation was obtained for product of the size of the horizontal an d vertical linear structural element. Geometric dim ensions of objects in the images increases with incre ase of the tissue strain level when observation pla ne is transversal to the direction of deformation. The effect can be affected by large amount of intercel lular spaces in the apple, the volume of which decrea ses during deformation.

A b s t r a c t . Texture of apples depends on geometrical dimensions of the cellular mechanical skeleton. For quantitative measurements of the dime nsions of cells an image analysis procedure should be developed which is proper to a certain imaging s ystem. In this paper two different image analysis methods are applied: image segmentation and visual texture analysis (VTA) to images obtained by an optical microscope for which a special sample fixat ion procedure for apple tissue was developed. The image analysis was performed for thin sections of a pple, cut by microtome from samples previously subjected to different strain levels: intact tissue , 5%, 10% and 15%. The experiment showed that seg- mentation of images from the optical microscope is possible after prior manual correction of the im- ages of apple, while visual texture analysis (VTA) provides quantitative results for the size and shap e of objects in the images automatically. The paramet ers obtained by the VTA correlate significantly with geometrical parameters obtained by the segmentation method. The highest correlation was ob- tained for product of the size of the horizontal an d vertical linear structural element. Geometric dim en- sions of objects in the images increases with incre ase of the tissue strain level when observation pla ne is transversal to the direction of deformation. The effect can be affected by large amount of intercel lu- lar spaces in the apple, the volume of which decrea ses during deformation.