生鲜牛乳主要品质指标与射频/微波介电谱关联机理解析

The nonhomogeneity and strong scattering characteristics of fresh milk are the important reasons that influence the precision and speed of milk quality detection. Our previous studies found that since the Radio-frequency (RF) or microwave (MW) has very small scattering intensity and large penetration depth in milk, the dielectric spectra has potential advantages in the rapid and accurate detection of milk quality. However, the influence rules and correlation mechanism between the partial quality indexes and the dielectric spectra of raw fresh milk are still need to be further studied. Open-ended coaxial probe technology will be used to study the correlative mechanism between milk’s qualities and dielectric spectra over the frequency range of 10MHz-4500MHz. The main objectives of this research are: ① to ascertain the influence rules of main physiochemical indexes and hygienic indexes on dielectric spectra of raw fresh milk, ② based on experimental data of large sample size, to extract the fingerprint features of dielectric spectra of qualified raw fresh milk, to study specificity and matching methods of dielectric spectra of some abnormal milk, and to develop qualitative discriminant models for identifying unqualified milk and quantitative prediction models of main quality indexes of qualified raw fresh milk based on dielectric spectra, and ③ to reveal the correlative mechanism between microscopic mechanism of dielectric behavior of particles in milk dispersion system and macroscopic rules of dielectric spectra by interfacial polarization theory such as Maxwell-Wagner in dielectric physics. This study will provide scientific basis for quality detection of milk based on RF and MW dielectric spectra, and help to enrich theories of dielectric polarization of nonhomogeneous liquid food in RF or MW electromagnetic field.

生鲜牛乳的非均质性和强散射特性是影响现代分析技术精确、快速检测牛乳品质的重要原因。申请人前期研究发现，射频/微波因在牛乳中极小的散射强度和较大的穿透深度使介电谱技术在牛乳品质快速、精确分析方面具有潜在优势，但目前对部分品质指标对介电谱影响规律和机制的认识还不够深入。本项目利用开口同轴探头技术研究10MHz～4500MHz范围内生鲜牛乳品质与介电谱关联机理。重点内容如下：①探明牛乳主要理化和卫生指标对介电谱的影响规律；②从大样本实验数据中提取合格牛乳介电谱指纹特征，分析几种异常乳介电谱的特异性及匹配方法，建立基于介电谱的牛乳品质定性判别模型和主要品质指标的定量预测模型；③利用电介质物理学Maxwell-Wagner等界面极化理论揭示牛乳分散系中粒子介电行为微观机制与介电谱宏观规律间关联机理。本研究可为牛乳品质射频/微波介电谱分析提供科学依据，有助于丰富非均质液态食品在电磁场中的介电极化理论。

项目以生鲜牛乳和多种异常乳（初乳、体细胞超标乳、掺杂乳等）为对象，以同轴探头技术（20～4500MHz）为主要研究手段，首次系统地研究了牛乳主要品质指标（蛋白质、脂肪、非脂乳固体、乳糖、盐分、水分等含量、体细胞数和菌落总数）对其介电谱的影响规律；研究了温度、贮藏时间、高压均质、掺杂对牛乳介电谱的影响规律。研究发现，牛乳的主要品质指标对其介电谱较为敏感，证明了介电谱技术能克服物料非均质特性，准确获取反映生鲜牛乳成分或内部结构的电磁信息。.基于介电谱技术结合化学计量学方法，通过大样本建立了生鲜牛乳卫生指标（体细胞数和菌落总数）定性判别方法以及常见牛乳掺杂（掺水、不同蛋白质掺杂、三聚氰胺、牛初乳掺杂牛常乳等）的定性识别方法；建立了生鲜牛乳品质指标（蛋白质、脂肪、乳糖、非脂乳固体、盐分、水分等含量、体细胞数和菌落总数）定量检测方法。结果表明，在生鲜牛乳卫生指标定性判别和牛乳掺杂检测方面，介电谱技术优于近红外光谱技术；介电谱技术在牛乳主要成分，如蛋白质、脂肪、非脂乳固体、盐分、水分等成分定量预测方面具有应用价值，特别是牛乳体细胞、菌落总数预测方面明显优于近红外光谱法。.以电介质物理学理论揭示了牛乳品质与介电参数的关联机理。研究首次发现，尽管牛乳的介电谱主要依赖于水分、盐分、频率和温度，但牛乳中一些极性大分子和非极性成分与其介电谱具有很好的相关性。原因在于这主要是由于这些组分在牛乳分散系中与水分子水化作用或与盐分的结合，影响牛乳中颗粒界面处的水分子、盐离子的介电行为（介电弛豫），进而影响牛乳介电谱。同时，这些组分颗粒通过阻碍盐离子或水分子的迁移或取向极化行为对介电谱形成贡献。研究首次发现，高压均质改变了牛乳分散系的内部结构，对其介电谱具有显著影响。.射频/微波电场中液态食品的介电特性和介电行为研究属于首次探索，研究成果为液态食品介电谱研究奠定理论基础，具有应用价值。

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