基于动力学模型的高油大豆储藏期间品质指标变化规律

    Changes in quality indicators of high oil soybean during storage based on kinetic model

    • 摘要: 为了解高油大豆储藏过程中品质指标的变化规律,为高油大豆的科学储藏及储藏期间的品质变化预测提供理论依据,选取河南与内蒙古产地的高油大豆为研究对象,调节至不同含水率13.00%和15.00%后分别在25℃和35℃条件下密闭储藏180 d,每隔30 d取样一次,对其品质指标进行测定分析,并进一步对其电导率和丙二醛(Malonaldehyde, MDA)两项指标的变化趋势进行动力学分析。结果表明,随储藏时间的延长,两种高油大豆中过氧化氢酶(Catalase, CAT)、过氧化物酶(Peroxidase, POD)及多酚氧化酶(Polyphenol oxidase, PPO)活性均呈下降趋势,电导率和MDA含量均呈上升趋势,且含水率和储藏温度越高,变化幅度越大。不同指标的相关性分析结果表明,储藏时间与两种高油大豆的品质指标的变化均有显著或极显著相关性,储藏时间与河南大豆的MDA和PPO相关系数分别为0.82和−0.90,与内蒙大豆的MDA和PPO相关系数分别为0.81和−0.92。初始含水率与两种大豆的CAT活性呈极显著负相关,相关性系数分别为−0.63和−0.74;储藏温度与两种大豆电导率的变化存在较强相关性,相关性系数分别为0.60和0.59。不同储藏温度下两种高油大豆的电导率和MDA含量的变化均符合零级动力学模型,两项指标在储藏过程中的变化均属于需能反应,零级动力学反应系数随大豆初始含水率和储藏温度的升高而增大,同时具有较高粗脂肪含量的河南大豆的电导率和MDA的零级动力学活化能均高于内蒙古大豆,并且在相同含水率条件下,MDA的活化能均小于电导率的活化能,表明高油大豆储藏过程中,温度、水分和粗脂肪含量越高,电导率和MDA含量变化越快,且MDA含量较电导率更易发生变化。因此在高油大豆储藏过程中,要根据大豆的脂肪含量,严格控制储藏时的温度和水分,尤其高含水率的大豆要严格控制温度条件,以延缓其品质劣变,同时在高油大豆储藏过程MDA含量较其他指标更易发生变化,可作为其储藏期间品质变化的早期预测参考指标。

       

      Abstract: In order to understand the changes of quality indexes and provide new insights for the scientific storage and the predictionof quality change of high oil soybean during storage. In the present study, a biochemical investigation was carried out to determine the quality indicators of high-oil soybeans during seed storage. Two kinds of high-oil soybeans were collected from the Henan and Inner Mongolia of China. Different moisture (13.00%±0.20% and 15.00%±0.20%) were then adjusted and stored the seeds at 25℃ and 35℃ for 180 days. The quality indexes of high-oil soybeans were determined and analyzed every 30 days during storage. Some parameters were evaluated, including the malondialdehyde (MDA) content, electrical conductivity, and enzyme activities of catalase (CAT), as well as the peroxidase (POD) and polyphenol oxidase (PPO). A correlation analysis was also carried out between the physiological and biochemical indexes. A kinetic model was selected for the change trends analysis of electrical conductivity and MDA. The results showed that the activities of CAT, POD, and PPO decreased with the increase in storage time, whereas the electrical conductivity and MDA content increased significantly in the two kinds of high-oil soybeans. And the change range of them increased with the increasing of the initial moisture content and the storage temperature. The correlation analysis showed that the storage time presented a significant or extremely significant correlation with the physical and chemical indexes of the two high-oil soybeans. The correlation coefficients between the storage time with the MDA and PPO were 0.82 and -0.90, 0.81 and -0.92, in the Henan and Inner Mongolia soybeans, respectively. The initial water content was significantly negatively correlated with the CAT activity of the two soybeans. The correlation coefficients were -0.63 and -0.74, respectively, indicating no strong correlation with the indicators. At the same time, there was a positive correlation between the storage temperature and the electrical conductivity in the two soybeans, where the correlation coefficients were 0.66 and 0.61, respectively. Furthermore, the kinetic analysis showed that the zero-order kinetic model better fitted for both electrical conductivity and MDA of the two high-oil soybeans at different storage temperatures. The two indexes were attributed to the energy demand reaction during storage (ΔG>0). The zero-order kinetic response coefficient also increased with the increase of initial moisture content and storage temperature of soybeans. Moreover, there was a higher content of crude fat in the zero-order kinetic activation energy of MDA and the electrical conductivity in the Henan soybean, compared with the Inner Mongolia one. Consequently, the higher temperature, initial moisture content, and crude fat content accelerated the electrical conductivity and MDA during storage, leading to the faster quality deterioration of the high-oil soybean. Therefore, a strict control of the temperature and initial moisture content during storage can be expected to maintain the fat content of seeds for the less quality deterioration of high-oil soybean. In particular with the high initial moisture content, the temperature conditions should be strictly regulated for the storage safety of the soybeans. Meanwhile, MDA content of high-oil soybean was more likely to change during storage than other indexes, which could be used as an early reference index for the quality change prediction.

       

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