| T. lepturus had delicious taste, rich nutrients which was well enjoyed by people.Because of the difference in geographic locations and hydrology，T. lepturus from differentplaces had different quality. Methods was used to identify T. lepturus of different placecould Impove commercial value and maintain national product of geographical indication.The factors affecting the quality of fresh T. lepturus from the aspects of biochemicalreactions、microbial proliferation and the function of enzyme in storage. The denaturationof proteins and fat oxidation made the components and concentration of sample would bedifferent over time. At the same time, smells of T. lepturus changed significantly duringstorage. It’s importand to evaluate the freshness of T. lepturus.一、 The identification of T. lepturus producing Area based on MultiplefingerprintFingerprint analysis was accepted and widely used in Chinese medicine origin andassess the medicine quality. However, there was a little applied on the identification ofaquatic products. Hence, T. lepturus samples collected in five different places were studiedinfrared spectral (MIR and NIR) and high performance liquid chromatography(HPLC).The characteristic components in complex sample were extracted and detected.1. Fingerprint of T. lepturus by FTIR（1）IR-fingerprint of raw material of T. lepturus: A validated Fourier transforminfrared spectroscopy (FTIR) spectrum method developed for the study of T. lepturussamples collected in five different places. Results fingerprints of T. lepturus in fivedifferent places contained13major common peaks. Absorption bands and strength had noobvious difference. The samples from the same region could be clustered together.Absorption bands and strength had quite different in second derivative IR spectra. Basedon the dissimilarity, we could identify the areas of T. lepturus.（2）IR-fingerprint of ethanol extracts of T. lepturus: In the experiment, avalidated FTIR spectrum method had been developed for the study T. lepturus’sethanol extract collected in five different places. Results fingerprints of T. lepturus infive different places contained14major common peaks. Discrimination function fordistinguishing different producing areas of T. lepturus were developed. Theaccuracy of the function could reach87.3%. Principal component analysis（PCA）was performed in the spectra region between1800cm-1and400cm-1. Through twoand3D diagram,satisfactory results can be obtained. The results were are consistentwith different geographic locations and hydrology. The contrast of second FTIRderivative spectroscopy further illustrate Chemical composition and quantity of T.lepturus in different places.In a conlusion, FTIR spectroscopy combined with principal component analysis and second FTIR derivative spectroscopy provides a subjective、quick andcomprehensive tool for the identification of T. lepturus.2. Study on fast diserimination of T. lepturus using NIRA new method for the fast diserimination of T. lepturus collected from different placesby means of near infrared spectroscopy(NIR) was developed. The experiment adopted T.lepturus from five places which we bought in aquatic fishery company and the market. Thenear infrared spectral data were collected from the samples and were preprocessed throughfirst derivation and vector normalization. In the spectra region between8500cm-1and4000cm-1, cluster analysis and discriminant analysis were performed. A factorization algorithmwas used to make discriminant analysis on the sample. A spectral library was established.With the qualitative identification, unknown samples were tested. The result showed that T.lepturus samples of different places could be classified correetly.3. HPLC-fingerprint of T. lepturusIn this paper, T. lepturus samples collected in five different places were studied todevelop a method of discriminating the fingerprint of T. lepturus by HPLC. Through theoptimization of chromatographic conditions and system suitability test, HPLC-fingerprintof T. lepturus in five different places was established respectively, and the first establishedT. lepturus reference fingerprint of different places. Results fingerprints of T. lepturus infive different places contained13major common peaks. At the same time,7characteristicpeaks were identified. Through comparing the relative retention time and relative peak areaof characteristic peaks, we find relative retention time of T. lepturus from five differentplaces has no obvious difference, but relative peak area has big differences.HPLC-fingerprint combined with cluster analysis could evaluate the places of T. lepturuseffectively. This method provides a reference for the origin of T. lepturus.二、Freshness of Zhoushan T. lepturus based on Multiple fingerprintSensory evaluation is subjective and the physicochemical index is too cumbersome.Objective、convenient and accurate methods were needed in detecting quality of T. lepturus.Combine with the physicochemical index, the storage quality would be studied withFTIR、NIR and enose technology in this experiment. Internal quality of T. lepturussamples obtained by FTIR and NIR. Enose technology showed the external changes. Theseresults show that the two methods could detect the freshness of T. lepturus.The storing,processing and transportation of aquatic product could be controlled and detected quickly.1. Freshness quality study of T. lepturus by FTIRIn this work, the study on the storage quality of T. lepturus was carried out usingFTIR. At4℃, cluster analysis based on conventional FTIR of T. lepturus in differentstorage time showed that samples of0～1d,2～5d,6～8d gathered as a class respectively,0～1d in the early stages of fresh,2～5d in the transition period，obvious deteriorationfrom the sixth day. At0℃, cluster analysis was applied to second derivative spectroscopy of T. lepturus, the samples of0～3d and4～7d clustered into one class respectively,8dseparately clustered into a class and were far away from0～7d, apparent quality changeshowed at the eighth day. The result of cluster analysis was consistent with total volatilebasic nitrogen (TVBN) analysis. Discriminant analysis further proved the effectiveness ofFTIR spectroscopy on the quality of identification. Infrared spectroscopy data combinedwith TVBN analysis suggested that the similarity between sample and fresh T. lepturus lessthan0.45initially speculated that the sample deteriorated.2. Freshness evaluation of T. lepturus based on NIRThe study on the freshness evaluation of T. lepturus was carried out by near-infraredspectroscopy, a rapid evaluation method of T. lepturus freshness based on near-infraredspectroscopy was established. The raw spectra of T. lepturus at4℃and0℃waspreprocessed by the first derivative and Vector normalization. To judge freshness of T.lepturus comprehensively, cluster analysis about near-infrared spectrum combined withsensory evaluation and TVBN was applied. Through data preprocessing and modeloptimizing，model based on partial least squares(PLS) algorithm was developed tocorrelate the spectra and the TVBN values. The result of cluster analysis was consistentwith total sensory evaluation and TVBN analysis. At the same time，shelf life extendedwith the lower temperature. The correlation coefficients (R2) and root mean square errorsof cross-validation (RMSECV) of the established model were98.19and1.95. The relativeerror on the prediction of the unknown sample were less than5%. It is a rapid, exact andreliable method to detect the freshness of T. lepturus.3. Freshness evaluation of T. lepturus based on electronic noseThe changes in volatile aroma and odor response of T. lepturus during differenttemperatures were characterized by electronic nose in this paper. Compared with TVBNanalysis, a rapid evaluation method of T. lepturus freshness based on electronic nose wasestablished. Smells of T. lepturus stored at4℃and0℃, respectively changed significantlyduring storage. Nitrogen oxides, sulfides, organic sulfides and aromatic components werethe underlying source of the T. lepturus quality deterioration. T. lepturus with differentdegree of freshness could be distinguished by both PCA and linear discriminant analysis(LDA). The detection of electronic nose was basically consistent with the TVBN analysis.In PLS analysis, R2between TVBN and electronic nose data in4℃and0℃is0.9887and0.9978, respectively.Results from this study suggested that electronic nose techniquesmight be utilized as a rapid measure of evaluating the freshness of T. lepturus. |
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