用于污染黄曲霉毒素花生分选的荧光信号研究

为在加工前将黄曲霉毒素超限的带衣花生米从原料中剔除,参照已有的色选系统,提出一种依据黄曲霉毒素含量超限带衣花生米的专属荧光信号进行逐粒分选的技术构想。采用Cary Eclipse荧光分光光度计测定100粒外观具有代表性的带衣花生米表面的紫外-荧光规律,通过与免疫亲和层析净化荧光光度法(GB/T18979-2003)检测结果对比,判定了黄曲霉毒素超限带衣花生米的荧光光谱特征;通过绘制450/490、460/490荧光强度比值的箱线图,评估了表面荧光法判断黄曲霉毒素超限带衣花生米的准确率;在搭建的荧光成像系统上,对黄曲霉毒素超限带衣花生米进行了荧光成像。检测发现,在365 nm波长激发下,黄曲霉毒素超限带衣花生米在420~460 nm处有荧光峰;以450/490荧光强度比值为依据剔除超限值带衣花生米的判断准确率为81%;a.u.40的带衣花生米可在图像中呈现亮蓝荧光光斑。表明表面荧光信号可作为带衣花生米在线、无损、逐粒分选的专属光学信号,用于黄曲霉毒素超限带衣花生米的剔除。

Fluorescent signal characteristics for sorting of peanut contaminated by aflatoxion

Peanuts are especially susceptible to contamination of aspergillusflavus and aspergillusparasiticus, which can produce a kind of highly toxic substance, aflatoxin.The study about the separation technology of aflatoxin-infected peanuts before processing can effectively isolate the source of contamination by taking precautions instead of executing treatment on the contamination, thus being of great significance on guaranteeing food safety.For the purpose of effectively eliminating the red-skin peanuts with excessive aflatoxin levels from raw materials, one technology concept of one-by-one sorting method using the exclusive fluorescent signal of the red-skin peanuts with excessive aflatoxin levels was conceived here referring to the existing color sorting system.In this study, the fluorescence spectra of 100 red-skin peanut samples with representative appearance were determined using Cary Eclipse fluorescent spectrophotometer (at an excitation wavelength of 365 nm, an emission wavelength in the range of 400~600 nm and discharge voltage of 400 V).According to the fluorescence intensity distribution of samples at the wavelength of 450 nm, all these 100 red-skin peanut samples were divided into 8 groups.The aflatoxin content for each group of samples was determined using the standard method, GB/T 18972-2003 Determination aflatoxin content in food-Cleanup by immunoaffinity chromatography determination by high-performance liquid chromatography and fluorimeter.By comparing the surface fluorescence spectroscopy of the 8 groups with the obtained results from the standard method, the fluorescence spectroscopy characteristics of the the red-skin peanuts with excessive aflatoxin levels were primarily determined.The accuracy rate of discriminating the aflatoxin levels of red-skin peanuts using surface fluorescence was evaluated by means of drawing the box-plots of the fluorescence intensity ratio at 450 nm/490 nm and 460 nm/490 nm.Taking the colony laser fluorescence microscope as a platform, and using a laser beam expander that can enlarge the projection area of the excitation light to cover 2-3 peanuts, the fluorescence images of the red-skin peanuts with excessive aflatoxin levels were taken using a monochrome fluorescence image acquisition system, which was set up by putting a band-pass filter (460±5 nm) at the front of an industrial camera objective.The results of this study showed that there was a correlation between the determination of the aflatoxinlevels in red-skin peanuts by using fluorescent spectrophotometer at an excitation wavelength of 365 nm to detect the fluorescence intensity at 450 nm and the aflatoxin measurement using the standard method, which means that while the fluorescence intensity at 450 nm is greater than 30 a.u., the aflatoxincontent exceeded the national standard limit.Thus, the characteristic fluorescent signal of the excessive aflatoxin contamination can be intended as follows: the emission spectra generate fluorescence peaks at 420~460 nm and the fluorescence intensity at 450 nm was greater than 30a.u., while under an excitation wavelength of 365nm.According to the calculation based on the Whisker upper and lower limit, the overlapping ratio of the fluorescence intensity was at 450 nm and 490 nm is 19%, indicating that the discrimination accuracy rate of red-skin peanuts with excessive aflatoxin levels was 81%.Meanwhile, using the fluorescence image acquisition system, the monochrome images of the aflatoxin excessive peanuts were obtained, which displayed blue light spot for the contaminated peanuts once the surface fluorescence intensity was greater than 40a.u.Overall, the study indicates that the surface fluorescence signal can be the exclusive light signal of the red-skin peanuts for on-line, nondestructive and one-by-one sorting, for the purpose of eliminating the red-skin peanuts with excessive aflatoxin levels.