abstract: This work is concerned with a method of the assessment of quality changes in a sample of agricultural material in which certain elements are distinguished and are subject to an agreed classification. The analysed changes related to an investigated quality attribute may have either one- or bi-directional character. This means that either a decrease or increase of the attributes value can be expected. A lack of changes in a portion of the sample elements is also acceptable, and this is usually a subject of a particular interest. A so called transition table was used for the record of the sample quality changes. This is a modified form of a transition matrix, used in the processes theory and operation research methods. The elements of the transition table are frequencies (empirical probabilities) of sample elements transitions from one quality class to another or else, non-transitions (i.e., the element remains in the same class). As a measure of quality changes in the material sample, an index was proposed which is a linear function of the transition table frequencies. Appropriately constructed weights are the parameters of these frequencies. It ensures additivity of this measure. A set of binary weights were proposed whose exponents contains information on the numbers by which the elements of the sample in the adopted classification have moved. Using optimisation methods (simplex algorithm of linear programming for one- and bi-directional changes or custom created algorithm for one-directional changes), a interval was identified, across which a value of the quality transition index can change. In addition, a few other indices were proposed which describe variability of the material sample.
The proposed method was illustrated using two examples. The first one is related to the assessment of changes in resistance of wheat kernels to internal cracking of their endosperm during drying (one-directional changes). The extent of cracking was determined using the X-ray technique and subsequent evaluation using specially created software. The second example is concerned with the assessment of stability of the soil aggregates selected samples when exposed to water. Water resistance of soil aggregates was determined using four analytical methods: rainfall, 1 and 10 cycles of wetting-drying and wet sieving. In the first part of the example, stability of aggregates were ascertained with an assumption that they may disintegrate or their diameters may remain unchanged. The second part is an attempt of applying the proposed method in a model in which changes of aggregation are possible in both directions, i.e., both disintegration and formation of aggregates. The proposed method may have a much wider application, beyond the field of agrophysics.