Abstract:

Three different calcium solutions and water (CK) were sprayed three times to the surfaces of the young Zizyphus jujube Mill. cv. Dongzao fruits during the early stage of fruit growth. Effects of different calcium solutions on the quality of young Zizyphus jujube Mill were studied. Forms of calcium during the storage were fractionated by sequent extraction in this paper. Besides, location and distribution of calcium were observed by transmission electron microscopy combined with in situ precipitation of calcium with an improved method of potassium pyroantimonate technique. Results showed that the three different calcium treatments could remarkably retard the increase in browning index and prolong the shelf-life with higher fruit firmness. Although the calcium treatments have no effect on the content of vitamin C (VC), they could prevent the VC consumption during storage effectively. The effects of different calcium treatments show no obvious difference on the content of total soluble solids, sugar and titratable acidity. Compared to the calcium treatment, the titratable acidity in fruits treated by CK is lower at 60th day after storage. Calcium treatment significantly increases the content of total calcium, H2O-Ca, NaCl-Ca and HAc-Ca. The content of ALc-Ca is the highest in fruit, which is about 37.9% to 55.1%. The content of NaCl-Ca and HAc- Ca declines, but the ALc-Ca content increases at 60th day after storage. Calcium containing antimonite precipitates are mainly distributed in cell wall tonoplast, nuclear membrance,and nucleoplasm. There are much more calcium containing antimonite precipitates in fruit cytoplast treated by CK than those of calcium treatments.

Key words: Zizyphus jujube Mill. cv. Dongzao, calcium, storage, quality, subcellular distribution