Research On Feed Additives Based On Terahertz Time-domain Spectroscopy

The spectral characteristics of two kinds of biological feed additives which are respectively probiotics and vitamins were studied by terahertz time-domain spectroscopy(THz-TDs)technology in this paper.Based on the analysis of spectral data,some mechanisms were revealed about composition and structure of biological feed additives.Meanwhile,physical model were also established combined with statistical analysis of spectral data,the purpose is to discuss and identify the feasibility of the nondestructive detection method from terahertz time-domain spectroscopy.The main content includes:First,three kinds of bacillus which are respectively bacillus licheniformis,bacillus subtilis and bacillus coagulans were detected by Transmission type terahertz spectrum system.The frequency-domain spectrum,spectra of refractive index and absorption coefficient were obtained and analyzed.The result shows that each probiotic has tiny characteristic absorption peaks which is not obvious,different probiotics have different spectral characteristics which is because of the complex composition and structure of probiotic.Specifically,the probitics is composed of cells of which the content is cell wall,cell membrane,and cell nucleus,and different kinds of protein,lipid and carbohydrate in molecule level,the types and content of molecule is different in each kind of probitic and collective vibration mode of different macromolecule is also different too and the superposition of these vibration modes lead to specific THz spectra.And then,five kinds of vitamins which are respectively vitamin A,vitamin B1,vitamin B2,vitamin B6,vitamin B12 were detected with THz-TDS.The result shows that vitamin A and B12 have characteristic absorption peak which can be used as a fingerprint identification of samples,however the other three kinds of vitamins are not.Theoretically the vitamin are pure macromolecule which has single structure and should have characteristic absorption peak,for example,it is found that most of the vitamin has absorption peak terahertz test of food and medicine[1].But the vitamins are not pure in feed additives,so the possibility of nonexistence of characteristic absorption peak is very high.Same as probiotics,different kinds of vitamins behave differently in time delay,intensity of absorption and refraction index.Based on the analysis in molecule level,differences are connected with different molecular structure of vitamins,whichlead to the difference in the light scattering and absorption degree during the interaction between THz wave and matter.Third,three kinds of bacteria and five kinds of vitamins were mixed with different proportions and detected with terahertz time-domain spectroscopy.The laws of the change of spectra with the mixture ratio of different biological feed additives were obtained.Particularly,In order to realize the identification of different biological feed additives,this paper establishes the cluster analysis model and partial least squares regression analysis model,the relationship between terahertz spectra of samples and the category were established through the two statistical mathematical model,the category of unknown sample can be got by spectrum data,thereby,unknown samples will be realized the recognition and identification.