abstract: This dissertation presents the investigation on application of passive and active thermography for evaluation of seed and fruit quality. A hypothesis was formulated, that internal defects and physiological disorders of fruit as well as biochemical processes which cause diminishing of seed viability lead to changes of thermal properties within these objects.
It was stated that radiation temperature of seed and fruit surface is a good parameter of evaluation of their quality. During thermal stimulation, hetero-geneities of thermal properties lead to the occurrence of thermal contrasts on the surface of these materials which can be successfully registered with the use of thermographic device.
A method was elaborated of early detection of apple bruises with the use of pulsed phase thermography (PPT). On the base of model investigations of heat transfer in fruit, optimal parameters of thermographic registration were chosen. Both model and experimental studies revealed that heat pulse of 1000 W, ranging from one to three seconds, caused the increase of fruit surface temperature of only 3-4°C, however due to the high heat capacity of apple skin its internal temperature did not increase above 1°C. The use of Fourier transformation, the analysis of ampligrams and phasegrams of fruit heat response as well as thermographic signal reconstruction (TSR) enabled to eliminate from the thermographic images the contrasts resulting from non-uniform heating of the object and to distinguish defects occurring at different depths.
The studies were performed on detection of flesh watercore in apples through the analysis of radiation temperature change on the surface of fruit during short-time heating. It was stated that the derivative of apple temperature in time per apple mass is a good parameter to evaluate the differences in thermal properties between apples with and without watercore affected tissues. The temperature gradient of 18.5°C between the fruit surface and the ambient temperature is sufficient to distinguish the differences in the rate of heating between watercored and unaffected apples.
The analysis of relation between the rate of apples heating and the physical parameters of their quality indicated that with the increase of both soluble solid content and density of fruit, the derivative of apple temperature in time per apple mass decreases for apples with and without watercore symptoms. There was no significant correlation between the derivative of apple temperature in time per apple mass and fruit firmness.
The usefulness of thermographic method for determination germination capacity of leguminous seeds was stated. Elaborated method enables to determine the average temperature of whole seeds and their parts. By applying automatic segmentation of thermographic images it possible to distinguish within thermograms the fields representing particular seeds. The analysis of radiation temperature changes on the seed surface shows the occurrence of considerable differences of this parameter in particular stages of germination process. In the conditions of the experiment, seeds which have ability to germinate revealed considerable decrease of temperature in the first stage of swelling process (for bean seeds 2°C during first 45 hours and for pea seeds 1°C during first 24 hours) Temperature changes of seed during first hours of swelling can be an indicator of their germination capacity (energy of germination). High agreement of thermo¬graphic method with standard germination test was stated.
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