Cryopreservation of Citrus seeds

GRAIVER NATALIA, CALIFANO ALICIA, ZARITZKY NOEMÍ.

Lima

Congreso; 8º Congreso CIBIA 2011 Congreso Iberoamericano de Ingenieria de Alimentos; 2011

Comite del CIBIA

Seeds have been categorized into three groups according to their response to desiccation and their storage physiology: orthodox (desiccation-tolerant), recalcitrant (desiccation sensitive) and intermediate.  Intermediate seeds are freezing sensitive and cannot be stored in liquid nitrogen (LN) without a previous partial dehydration process. The water content of the seeds at the moment of immersion in LN must be regarded as the most critical factor in cryopreservation process. The objectives of this study were: a) to investigate the optimal moisture content for cryopreservation of different Citrus seeds: Citrus sinensis  (sweet orange), Citrus paradise (grapefruit), Citrus reticulata var. Criolla and Citrus reticulata var. Dancy (mandarin); b) to analyze  the tolerance ( viability)  to LN exposure of seeds of  the genus Citrus; c) to establish  the relationships between equilibrium relative humidity (ERH), seed water content, presence of frozen water and germination percentage after immersion in LN. To study the tolerance to dehydration and LN exposure, seeds were desiccated by equilibration at relative humidities between 11 and 95%. Sorption isotherms were determined and modeled; lipid content of the seeds was measured. Seed viability was analyzed by germination experiments. Differential scanning calorimetry (DSC) thermograms were determined on cotyledon tissue at different moisture contents; ice melting enthalpies and unfrozen water content were measured. Samples of total seed lipid extract were also analyzed by DSC to identify lipid transitions in the thermograms. Obtained results showed that the limit of hydration for LN Citrus seeds treatment corresponded to the unfrozen water content in the tissue, confirming that seed survival strictly depended on avoidance of intracellular ice formation