A method is proposed for assessing the maturity and quality of seeds, based on measuring the amount of chlorophyll fluorescence (CF) signals of intact seeds. In general, the amount of chlorophyll is directly related to the degreening process and thus the maturity. Cabbage seeds (Brassica oleracea var. capitata) were separated into three subsamples based on the CF signals of the individual intact seeds. Seeds with the lowest amount of CF had the highest percentage of germination and normal seedlings. In a controlled deterioration test, the subsample with the lowest CF signal had slightly lower germination and normal seedling percentages than the non-treated seeds, whereas the seeds with the highest CF signals had much lower germination and normal seedling percentages. Advantages of the CF method for determining seed maturity and seed quality are its high sensitivity and fully non-destructive nature and the high speed at which the fluorescence is generated and measured.

Chlorophyll fluorescence of the testa of seeds is proposed as a non-invasive method for the determination of maturity and quality of seeds. In this study cabbage seeds (Brassica oleracea) were sorted individually based on the chlorophyll fluorescence signals into four subsamples labeled with respect to their chlorophyll fluorescence signal (low, medium, high and very high). The results show that the magnitude of the chlorophyll fluorescence signal was inversely related to the quality of the seeds, expressed as germination %, normal seedling %, germination rate (T50) and uniformity of germination (T75-T25). The seed lot could be improved from 90 to 97% normal seedlings by sorting out 13% of the seeds with very high chlorophyll fluorescence signals. Advantages of the chlorophyll fluorescence method for sorting seeds are the high sensitivity, the method being fully non-destructive, the high speed at which the fluorescence is generated and measured and the specificity for only chlorophyll. Other pigments or substances which can influence seed colour but do not fluoresce at the specific wavelengths of excitation and emission of chlorophyll, will not contribute to the fluorescence signal. These characteristics make chlorophyll fluorescence highly suitable as a new sorting technique.

The photopyroelectric (PPE) technique is proposed to detect solid-to-liquid phase transitions in fatty acids and triglycerides. Various PPE configurations and cell geometries were used to obtain thermal parameters in the vicinity of the melting points for these samples. In the standard (SPPE) configuration used to determine specific heat, the sample is thermally thin and optically opaque, while the sensor itself is thermally thick. The same configuration, but with a thermally thick sample instead, allows direct measurement of the sample's thermal diffusivity. The temperature dependence of the thermal effusivity was obtained for a thermally thick sample and a thermally thin sensor [inverse (IPPE) configuration], and for a semitransparent thermally thick sensor by making use of the front configuration. JAOCS 72, 273-279 (1995).

The photopyroelectric (PPE) technique was used to detec~ so}id-to-liquid phase transitions in saturated [C6:0, C10:0, CI 2:0, C16:0 palmitic acid (P), C] 8:0 stearic acid (S)] and unsaturated (C18:2) fatty acids and some triglycerides (PSP, PPS). By using the standard PPE configuration with a thermally thin and optically opaque sample and a thermally thick sensor (a1.1 ); the temperature behavior of the volume-specific heat in a temperature range that includes the melting points for C10:0, C12:0, C16:0, and C18:0 was obtained. When the standard PPE configuration, with sample and sensor both being thermally thick and the sample being optically opaque (a1.2), was used, the information contained in the phase of the PPE signal allowed direct measurement of the thermal diffusivity for C10:0, C12:0, and PSP. The inverse configuration with a thermally thick sample and thermally thin sensor (b1.2) or a semitransparent thermally thick sensor (b2) was used to obtain critical behavior of the thermal effusivity for C10:0 and C12:0, respectively. Critical behavior of the thermal conductivity for same samples was computed from information obtained from amplitude and phase measurements (a1.2), or by combining a1.1 and b1.2 data. The history (age, storage conditions, annealing) of the samples affects the critical behavior of thermal parameters. JAOCS 72, 281-287 (] 995).

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