【作者】 李鹏；

【导师】 张子德； 马俊莲；

【作者基本信息】 河北农业大学 ， 农产品加工及贮藏工程， 2007， 硕士

【摘要】 冬枣是典型的鲜食品种，其丰富的营养价值和酥脆可口的鲜食品质在市场上很受欢迎。由于冬枣本身固有的生物学和生理学特性，组织结构特殊，采后在自然状态下极易失水皱缩、酒软或霉烂，并伴有Vc大量损失，营养价值降低，鲜食品质逐渐丧失，商品化程度下降。目前冬枣的贮藏保鲜问题尚未解决，严重影响着冬枣业的发展。本研究以河北黄骅地区产的冬枣为试验材料，研究了其采后的衰老生理特性及乙醇积累途径，并对果肉组织超微结构进行了观察与探讨。主要研究结果如下：1．在室温下对冬枣采后呼吸强度进行测定表明，冬枣果实在采后无明显呼吸高峰出现，判断试材为非跃变型果实。2．冬枣采后伴随着贮藏期的延长，硬度不断下降。作为呼吸代谢底物，可滴定酸含量在贮藏中整体上呈下降趋势。总糖含量在贮藏前期短暂增加，后期又逐渐降低，但还原糖含量却一直呈上升趋势。Vc含量呈下降趋势，Vc含量变化与硬度变化呈显著正相关(r=0.916)。乙醇含量不断积累，到枣果衰老时达较高水平。乙醇含量变化与冬枣硬度变化呈极显著负相关(r=-0.968)。Vc含量变化与乙醇含量变化呈极显著负相关(r=-0.953)。MDA含量不断增加，MDA含量变化与枣果硬度变化呈显著负相关(r=-0.9107)。3．冬枣采后PG活性的变化与硬度变化相关性不显著(r=0.646)。PPO活性随枣果实的成熟衰老逐渐上升，其活性变化与鲜枣果肉硬度变化呈显著性负相关(r=-0.833)。POD活性在冬枣贮藏过程中有高峰出现，其活性变化与硬度变化相关性不显著(r=-0.503)。AAO活性在Vc含量下降的同时急剧升高。AAO活性变化与Vc含量变化呈极显著负相关(r=-0.955)。AAO活性变化与果实硬度变化呈显著负相关(r=-0.891)。4．冬枣采后无氧呼吸过程中，果肉丙酮酸含量变化趋势与乙醛变化趋势相一致，二者呈极显著正相关(r=0.928)。丙酮酸与乙醛含量的变化是乙醇积累的重要原因。果皮木质素含量不断上升，影响其含量的关键酶PAL活性呈先上升后下降趋势，PAL活性的上升导致木质素含量的上升。木质素含量变化又与乙醇含量变化呈极显著正相关(r=0.967)。推测木质素含量的变化在冬枣采后乙醇积累过程中起相关作用。对冬枣健康果实及衰老果实的果皮进行了显微观察，发现衰老果实的果皮颜色变为红色，细胞排列松散，胞间隙较大，出现较多裂痕。推测由于果皮结构发生了变化，导致酵母菌侵入枣果组织内部，导致乙醇的积累。5．冬枣果实进入成熟期后，细胞壁内部结构被破坏，细胞壁极其内含物大量降解成无规则丝状物质。胞间层消失，分解成松散的丝状物以及出现了大量的空隙，胞间隙变大。这一系列变化引起果肉组织变化，造成果肉软化衰老。更多还原

【Abstract】 Dongzao jujube fruit was a typical fresh fruit, the affluent in nutrition and crisp high quality were welcome to everyboby. But after harvest, Dongzao jujube fruit was inclined to lose water and crimpled, with softening, rotting and Vitamin C loss, the nutrition, the high quality and commodity value were not maintained because of its connatural characteristics of biology and physiology. At present, the problem of keeping-fresh for Dongzao jujube fruit was not resolved, which affected the development of Dongzao jujube fruit greatly. In this paper, its physiological characteristics in consenescence, accumulate ethanol avenues, and ultrastructure in flesh structure of Hebei huanghua’s Dongzao jujube fruit were studied, The main results were as follows:1. The study on the respiration of Dongzao jujube fruit in the room temperature showed that the distinct respiration peaks were not found after harvest, therefore, this test material belonged to non-climactic fruit.2. The firmness of Dongzao jujube fruit was declined with the delay of storage time. On the whole, the titratable acid content as respiration substance which was declined, totle sugar content was increased temporarily in the prophase of its storsge, and declined gradually in the anaphase of its storage, but the reducing sugar was increased in the whole storage. Vc content was declined, the changes in Vc content was positive correlated with the firmness of Dongzao jujube fruit significantly (r=0.916). ethanol content accumulated continually, and reached higher level when it was consenescence. The changes of enthanol content was negative correlated with the firmness of Dongzao jujube fruit significantly (r=-0.968). The changes in Vc content was negative correlated with the changes of enthanol content significantly (r=-0.953). MDA content increased gradually, the changes of MDA content was negative correlated with the firmness of winter jujube fruit significantly (r=0.9107).3. The activity of PG changes were not correlated with the firmness of Dongzao jujube fruit after harvest significantly (r=0.646). The activity of PPO was increased gradually with the fruit’s maturity, the activity of PPO changes was negative correlated with the firmness of Dongzao jujube fruit significantly (r=-0.833). The activity of POD reached top point with storage, The activity of POD was not correlated with the firmness of Dongzao jujube fruit after harvest significantly (r=-0.503). The activity of AAO increased rapidly with the decreaseness of Vc content. The activity of AAO was negative correlated with Vc content significantly (r=-0.955). The activity of AAO was negative correlated with the firmness of Dongzao jujube fruit after harvest significantly (r=-0.891).4. The pyruvic content changes was positive correlated with the acetaldehyde content changes significantly during respiring without oxygen (r=0.928). The main reasons of ethanol accumulation was the pyruvic and acetaldehyde content changes.The lignin in flesh content increased gradually, the activity of PAL which influenced the lignin in flesh content increased first, and then decreased, the activity of PAL led to lignin content rise. The lignin in flesh content was positive correlated with enthanol content significantly (r=0.967). Therefore, it was conjectured that the lignin in flesh content changes were important during ethanol accumulation.Observing the tissue of pericarp which were healthy and senile with the optical microscope, the results showed that the color of pericarp reddened, the cell structure was not tight, the intercellular space largened and much crack was found easily, so it was conjectured that a lot of collective microzyme in the softening tissue of Dongzao jujube were found because of the flesh structure changes, that led to enthanol accumulation.5. The interior structure of cell wall destroyed during maturity of the fruits, the cell wall and cell content decreased and changed fitful filiform substance. Middle lamella disapeared, decreased and changed filiform substance, the interstice was found easily and intercellular space largened. Those changes arose the flesh structure changes, and led to softening and consenescence in flesh.更多还原