Carbohydrate composition during long-term storage of carrots as influenced by the time of harvest

Correlations between Polyacetylene Concentrations in Carrot (Daucus carota L.) and Various Soil Parameters

This study assessed the concentrations of three falcarinol-type polyacetylenes (falcarinol, falcarindiol, falcarindiol-3-acetate) in carrots and the correlations between these and different soil traits. A total of 144 carrot samples, from three different harvests taken a single season, were analysed in terms of their polyacetylene concentrations and root development. On one of the harvesting occasions, 48 soil samples were also taken and analysed. The chemical composition of the soil was found to influence the concentrations of falcarinol-type polyacetylenes in carrots. When the total soil potassium level was 200 mg/100 g soil, the concentration of falcarindiol (FaDOH) in the carrot samples was 630 μg/g DW, but when carrots were grown in soil with a total potassium level of 300 mg/100 g soil, the FaDOH concentration in the carrots fell to 445 μg/g DW. Carrots grown in soils generally low in available phosphorus exhibited higher levels of falcarindiol if the soil was also low in available magnesium and calcium. The concentrations of polyacetylenes in carrots were positively correlated with total soil phosphorus level, but negatively correlated with total soil potassium level. Of the three polyacetylenes analysed, FaDOH concentrations were influenced most by changes in soil chemical composition.

Polyacetylenes in fresh and stored carrots (Daucus carota): relations to root morphology and sugar content

BACKGROUND

Carrot roots contain polyacetylenes, reported to be both beneficial and distasteful when consumed by humans. This study aimed to investigate the relationships between polyacetylene contents, root morphology and sugar content in order to increase the opportunities to optimise the composition of polyacetylenes in carrots.

RESULTS

The falcarinol/total polyacetylene ratio was positively correlated with root size, the amount of sucrose and the sucrose/total soluble sugar ratio among both fresh and stored samples. Root size was inversely correlated with the amounts of falcarindiol and falcarindiol-3-acetate, especially among stored samples. Stored carrots exhibited an inverse correlation between polyacetylenes and the amount of soluble sugar. At a falcarinol content at harvest below approximately 200 mg kg(-1) dry weight the amounts of all polyacetylenes increased during storage, but above that level the amounts of all polyacetylenes instead decreased.

CONCLUSION

The results indicate similarities in the activity of the enzymes transforming sucrose to hexoses and the enzymes transforming falcarinol to falcarindiol-3-acetate and falcarindiol. The negative correlation between root size and polyacetylenes seems to be partly due to dilution but also to a higher synthetisation rate in smaller roots. The results indicate the existence of an equilibrium regulating the level of falcarinol.

Factors Affecting Quality and Postharvest Properties of Vegetables: Integration of Water Relations and Metabolism

Growing of vegetables in the field, harvesting, handling in the packing house and storage are events in the lifetime of vegetables that are analysed from the point of view of the complex series of physiological transitions taking place in each of these events. Water is the major factor limiting plant metabolism and plants have developed fascinating mechanisms to cope with this limiting factor. Therefore, water relations (water, pressure and osmotic potential) are used as criteria for discussing plant stress physiology aspects such as osmotic, elastic adjustment and cold acclimation, as well as mechanical stress when the vegetable is harvested and during handling in the packing house. Consequences for the storage potential and quality of the vegetable are discussed. After harvesting, the postharvest cell has the ability to complete a complex series of physiological transitions that will influence vegetable quality andfurther processing operations. Metabolic changes in the cytosol, cell membrane and cell wall are described.