Non-invasive quality determination of spinach under simulated sale conditions and prediction of possible changes

Abstract

Chlorophyll fluorescence, especially the optimum quantum yield Fv/Fm, is used to quantify the physiological state of plants, because stress, infections or wilting may lower the optimum quantum yield. The characteristics of chlorophyll fluorescence have attracted our attention for its use to determine the quality of spinach, because the measurement of Fv/ Fm during storage can be performed quickly and non-destructively, delivering information about spinach quality and its sale suitability. Applicability of modern techniques for quick and non-invasive in vivo determination of such parameters as quality and freshness of spinach under simulated sale conditions was tested in our study. In this experiment, application of chlorophyll fluorescence for quantification of quality as well as physical and physiological changes which occur in fresh products was verified. The experiment was conducted on spinach, a product characterized by rapid appearance of postharvest losses. Spinach was harvested as leafy vegetable for direct consumption and stored for 5 days (16 h in a cooling room at 2-4°C, 96-98% relative humidity, followed by 8 h at room temperature: ca 22oC, 65% relative humidity). Variants were represented by different cultivation conditions (fertilizer, leaf application of Previcur, CaCl2 and Cerone). The investigations revealed that fresh mass losses in the postharvest phase could be described by changes of Fv/Fm spinach leaves adapted to darkness by a linear relationship of parameters (r=0.77). The disadvantage of chlorophyll fluorescence measurement was the less precise determination of the critical loss of fresh mass of 3%. Instead, losses of 4 to 5% resulted in a the decrease of optimum quantum yield below the critical value of 0.80, which indicates the occurrence of postharvest stress. Leaf application