透明保鲜膜包装以其方便、 经济、 卫生的特点被广泛应用于超市卖场及日常生活中, 却也给食品农产品的检测增加了难度, 所以急需一种能够隔透明薄膜无损检测农产品的方法。 叶绿素是影响黄瓜品质的重要因素之一, 该研究主要探讨了拉曼技术检测黄瓜品质时, 食品保鲜膜层数对叶绿素特征峰的影响, 并通过对菠菜、 油菜和芹菜对得出的结论进行验证。 采用点检测拉曼光谱系统, 采集无保鲜膜包装以及多层包装下黄瓜的拉曼光谱。 拉曼信号经Savitzky-Golay(SG) 5点平滑和自适应迭代惩罚最小二乘法扣除荧光背景, 探究不同层数(1~6层)的PE保鲜膜对黄瓜叶绿素特征峰的影响。 采集被保鲜膜覆盖的黄瓜的拉曼信号并处理, 即可建立叶绿素的特征峰(1 158和1 528 cm-1)减少值与保鲜膜层数之间的变化规律, 并对规律的预测效果进行评价。 随着保鲜膜层数的增加, 透明包装层数与黄瓜叶绿素特征峰强度之间呈现良好的线性相关关系。 提取出单层透明包装对叶绿素在1 158和1 528 cm-1处特征峰强度的降低值分别为81.4和103.1, 分别占未加保鲜膜时叶绿素特征峰强度值的7.98%和8.56%, 多组验证结果的相关系数达到0.95以上, 验证的相关系数达到0.94。 随着样品浓度增高, 线性递减效果越明显。 作为验证, 通过透明保鲜膜检测菠菜、 油菜和芹菜叶片中的叶绿素表明, 每加一层膜叶绿素在1 158和1 528 cm-1处的特征峰强度会比覆膜前分别降低7.9%～8.6%和8.1%～8.6%; 导致检测信号强度呈线性降低是由于保鲜膜使激发光分散不聚焦导致, 保鲜膜成分对检测结果无影响。 该研究为拉曼光谱隔透明包装检测拉曼光谱特征峰强度, 进而获得农产品品质信息提供了一种新的分析方法。

Now transparent plastic wrap packaging gains great popularity because of its characteristics like convenience, economy and sanitation and be widely used in supermarket stores and daily life, which increases difficulties in detecting food and agricultural products. Thus a rapid nondestructive detecting method to detect agricultural products covered with transparent film is urgently needed. Chlorophyll is one of the vital factors which affect cucumber quality. The research mainly makes a thorough inquiry in the influence of food plastic wrap(material and number of plies) to Raman characteristic peaks of chlorophyll in cucumber. In the research, point-to-point Raman detecting system is used to gather Raman spectrum of cucumber covered with no plastic wrap and several layers of plastic wrap. Fluorescence background of Raman spectrum of cucumber is deducted with Savitzky-Golay five-spot smoothing and adaptive iterative least square method to investigate the influence of PE plastic wrap (1 to 6 layers) to Raman characteristic peaks of chlorophyll in agricultural products like cucumber. One detecting spot is detected three times to get its average value after covering a layer of plastic wrap. And nine detecting spots is got from a cucumber sample. The Raman spectrum of cucumber covered with plastic wraps is gathered and processed. Then the prediction model between reduction value of Raman characteristic peaks of chlorophyll (in the position of 1 158 and 1 528 cm-1) and layers of plastic wrap can be built. And then predictive effect of the model can be evaluated. With the increase of layers of plastic wrap, linear relationship is clear between layers of transparent package and intensity of Raman characteristic peaks of chlorophyll in cucumber. And as a reliable validation method, unary linear regression is used to judge the degree of correlation between the reduction value and layers of transparent package. It can be extracted that the reduction value of intensity of Raman characteristic peaks of chlorophyll in 1 158 and 1 528 cm-1 respectively are 81.4 and 103.1 which occupy 7.98% and 8.56% of intensity of Raman characteristic peaks of chlorophyll in cucumber without plastic wrap. In addition, the correlation index of verification result of several groups are all more than 0.95. And the correlation index of the results when verifying the change rulealso researches 0.94. From the research we know thatin the detection of chlorophyll in cucumber, rape and celery, the reduction value of intensity of Raman characteristic peaks of chlorophyll will also occupies 7.9%～8.6% and 8.1%～8.6% of the intensity value after covering a layer of plastic wraprespectively. And with Chlorophyll concentration of samples increasing, the detection effects become obvious. It is assumed that the scattering to exciting laser by plastic wrap is the reason that makes the intensity of Raman characteristic peaks of chlorophyll decrease with a linear relationship. The Raman characteristic peaks of plastic make no effect to the detection results. And it can be speculated the intensity of Raman characteristic peaks of chlorophyll also decreases with a linear relationship in detecting agricultural products covered with PVC or PVDC wrap. Similar results also will be got when detecting chlorophyll in other agricultural products. The research provides a new method in detecting the quality of fruits and vegetables with transparent package.