运输振动和冲击对苹果品质影响及其机理研究

During transport and handling, the fresh fruits experience a variety of loading conditions that may lead to damage and bruising. The three factors which can physically cause fruit bruising are vibration, compression and impact. During these processes, the mechanical damage can reduce the fruit quality, the loss of fruits during transport and distribution was about higher than 30% in China. However the mechanism of fruit quality changes during transport is still unclear. Therefore, how to reduce the fruits losses during transport and distribution becomes an important project among the researches on fruit processing, distribution and storage..Based on the previous analysis on the characteristics of vibration and shock during truck transport for fruits, three aspects would be studied in this project. Firstly, by using accelerometers, vibration and shock levels would be measured continuously over several typical truck transport routes for fruits in China. Accelerometers monitor acceleration vertically, longitudinally and laterally. In order to better understand the Chinese fruit distribution environment, an improved lab-simulated method of vibration and shock would be proposed. Secondly, the effect of vibration and shock levels on the physical and physiological characteristics of apple fruits during transport and distribution would be investigated. Several apple cultivars with different maturity would be used in this project. The changes of physical characteristics (including flesh firmness, bruise area and volume, sensory index, weight loss, etc) and physiological characteristics (including respiration rate, ethylene production, ACC synthase activity, ACC oxidase activity, LOX activity and MDA content, relative electric conductivity, etc) of apple fruits would be determined. Thirdly, the changes of the ethylene-related gene expression due to the different vibration and shock conditions would be surveyed. RNA would be extracted according to Chang et al. (1993) with some modifications. Quantitative real time RT-PCR analysis would be carried out for genes involved in ethylene biosynthesis, perception and signaling (ACC synthase (MdACS), ACC oxidase (MdACO), ethylene receptors (MdETR and MdERS), constitutive triple mutant (MdCTR), and ethylene response factor (MdERF)). This project can provide the theory basis for how to reduce the fruit losses during truck transport and how to develop the injury-resistant varieties and cushioning packaging for fruits.

新鲜水果在运输、搬运时，无论采取何种运输方式、包装形式，振动、挤压、碰撞都不可避免，都会不同程度地对水果造成损伤。我国水果在流通运输过程中的损失高达30%以上。但迄今为止，水果制品在流通运输过程中的品质变化的机理仍不清晰。所以如何减少水果在流通运输过程中的损失，已成为水果加工、流通与贮藏研究中的一个重要课题。.本项目拟在前期水果运输振动及冲击特性解析等研究的基础上，首先调查与分析我国水果的卡车运输振动和冲击的状况和规律，建立运输振动、冲击的实验室模拟方法；其次，研究苹果的不同品种、收获时期、卡车运输过程中产生的振动及冲击等条件对苹果的物理及生理特性的影响及规律；最后，研究卡车运输振动和冲击等条件与苹果果实乙烯生物合成相关酶的基因表达的关联。本项目能为减少我国在卡车运输过程的水果损失、抗损伤果实品种的开发，以及流通过程中果实的缓冲包装设计提供重要的理论依据。

新鲜水果在运输过程中，挤压、碰撞等处理会不同程度地对水果组织造成损伤。因此，对运输过程中水果的品质变化规律及其机理解析等方面进行研究能够对减少水果损伤，抗损伤水果品种的开发、以及开发流通过程中缓冲包装方法提供更好的理论基础。本文主要研究卡车运输振动和冲击特性解析、模拟运输振动和冲击处理方法对苹果理化品质、以及与乙烯生物合成相关酶的基因表达的影响。.主要研究结果如下：①测定了苹果果实在实际运输过程中道路振动和冲击的加速度数据。结果表明，冲击加速度水平振动和要比冲击的要高很多。冲击加速度的大小和频率主要由具体路况决定。这些振动和冲击加速度的数据可为在实验室中进行振动和冲击的模拟提供很好的支持。②测定了不同振动时间对苹果硬度等理化特性的影响。结果表明，苹果在4℃的条件下要比20℃能更好的保持品质。在振动以及振动后的储藏过程中，苹果果实的理化特性均呈先升后降的趋势，振动9h，储藏12d果实的乙烯生成量、ACC含量、ACS活性、ACO活性变化显著，活性变化最大，之后显著降低。③测定了不同振动时间对苹果的乙烯生物合成相关酶的基因表达水平的影响。结果表明，乙烯生物合成相关酶的基因表达水平与果实的理化特性变化趋势相似，在振动8h，储藏8d后的果实MdACS1、MdACO1、MdCTR1、MdETR1、MdERS1基因表达水平达到最大值，之后显著降低。并且ACS活性变化水平明显高于ACO，MdACS1基因水平显著高于MdACO1，乙烯转导途经中MdCTR1基因相对表达水平较MdETR1、MdERS1基因表达显著。④测定了不同高度、不同接触面的冲击处理对苹果的硬度等理化特性的影响。结果表明，与振动处理比较，冲击对果实品质影响显著，冲击高度30cm的大理石材料对果实理化特性影响最为显著，超过30cm冲击高度的果实理化特性均下降。⑤测定了不同高度、不同接触面的冲击处理对苹果的乙烯生物合成途径相关酶的基因表达水平规律。结果表明，与振动处理比较，冲击对果实乙烯生物合成途径影响显著，30cm的高度是果实能承受的最大阈值，与乙烯生物代谢途径的相关MdACS1、MdACO1、MdCTR1、MdETR1、MdERS1基因相对表达丰度最显著，并且ACS活性变化水平明显高于ACO，MdACS1基因水平显著高于MdACO1，乙烯转导途经中MdCTR1基因相对表达水平较MdETR1、MdERS1基因表达显著。