拉曼光譜法應用於乳製品之檢測

拉曼光譜法是以探測光波光子與物質分子之非彈性碰撞所產生振動能階為原理的分析方法，此方法可用於液態和固態樣品做定性與半定量分析。本研究目的是利用雷射光源為785 nm的拉曼光譜儀來檢測鮮乳、保久乳、奶粉與奶精粉樣品，並研究其拉曼光譜圖之光譜變化，來探討各乳製品之可能成分官能基造成的拉曼特徵峰，以辨別鮮乳、還原乳與保久乳以及奶粉與奶精粉之差別、檢測牛乳之乳脂率與探討辨別奶茶中鮮乳與奶精的方法。結果顯示，鮮乳、還原乳與保久乳於波數範圍960至1180 cm-1之間的拉曼光譜圖有差異，可將此區間的拉曼訊號強度以主成分分析法辨別三者；而於奶粉和奶精粉之拉曼光譜圖中，發現奶粉之特徵峰顯示於波數352和1000 cm-1處，而奶精粉之特徵峰則是於476和926 cm-1處，這些特徵峰之顯示與否可用來分辨奶粉及奶精粉。牛乳之拉曼乳脂特徵峰則發現顯示於波數1264、1300、1440、1654和1746 cm-1處，利用不同乳脂率與這些特徵峰的訊號強度之線性關係建立乳脂檢量線，可檢測牛乳之乳脂量。此外，於紅茶中添加鮮乳或奶精水的結果顯示，紅茶之拉曼訊號強烈，會遮蔽區分鮮乳與奶精之特徵峰，但於1300、1440與1654 cm-1處可觀察出油脂特徵峰。綜上所述拉曼光譜法有潛力成為快速檢驗乳製品之方法，其最大優點是樣品不需經過繁瑣的前處理，能節省時間和成本。關鍵字：拉曼光譜法、鮮乳、保久乳、還原乳、奶粉、奶精

關鍵字

拉曼光譜法；鮮乳；保久乳；還原乳；奶粉；奶精

並列摘要

Raman spectrometry is an analytical method based on the principle of detecting the vibrational energy levels generated by inelastic collisions between light-wave photons and matter molecules. This method can be used for qualitative and semi-quantitative analysis of liquid and solid samples. The objectives of this study were to analyze the dairy samples including fresh milk, sterilized milk, milk powder and creamer powder using a Raman spectrometer with a 785 nm laser, to understand the changes of spectra from the Raman spectrograms to further discuss the characteristic peaks resulting from the possible functional groups of the components in the samples in order to distinguish fresh milk from sterilized milk and reconstituted milk and milk powder from creamer powder, to determine the milk fat percentage in milk samples, and to discuss the way to distinguish fresh milk and creamer in milk tea. The results of the Raman spectrograms at wavenumber ranged from 960 to 1180 cm-1 show differences among fresh milk, sterilized milk and reconstituted milk. The intensities of these Raman signals after analyzed using principal component analysis can be used to distinguish the three. On the other hand, the characteristic peaks in Raman spectrograms of milk powder are found at wavenumber 352 and 1000 cm-1, while those for creamer powder are found at 476 and 926 cm-1. The appearance of these characteristic peaks can be used to distinguish milk powder from creamer. Additionally, the characteristic peaks for milk fat are found at wavenumber 1264, 1300, 1440, 1654 and 1746 cm-1, and the linear relationship of their intensities and different concentrations of milk fat can be used to construct standard curves of milk fat to detect the milk fat % in milk. Moreover, the Raman spectrograms of black tea show strong signals, which can mask the characteristic peaks used to differentiate fresh milk and creamer when mixed with black tea but not the lipid characteristic peaks at wavenumber 1300, 1440 and 1654 cm-1. In summary, Raman spectrometry has a potential to become a method of rapid inspection for dairy products without tedious sample preparation to save time and cost, which is its greatest advantage. Keywords: Raman spectrometry, fresh milk, sterilized milk, reconstituted milk, milk powder, creamer