Application Of Electronic Nose On Discriminant Of Shrimp Freshness

As main aquaculture seafood in china, shrimp was welcomed and popular due to itstaste, nutrition and high medical value. However, the shrimp is easy to corruption for rich inprotein, high water content as well as active autolysis enzyme.In recent years, with the improvement of living standard, people’s pursuit wererequired from the quantity stage to qualitative stage, food safety was paid more attention.Shrimp freshness was a main index reflecting the shrimp quality and safety, so the freshnessdetection of shrimp became a very meaningful task. The traditional freshness determinationmethods were sensory identification, chemical, physical, and microbial appraisal and so on,these methods had shortcomings such as long experiment cycle, tedious steps, subjectivefactors. Shrimp was studied in this paper. The purpose of this paper was to establish fast,nondestructive and low in price technology to detect shrimp freshness.The main results were gotten as follows:1. The test results are consistent of shrimps in different storage conditions for thevolatile base nitrogen determination and sensory evaluation. The results showed that theshrimp stored at high temperature, its value of TVBN increased fast and the score ofsensory evaluation declined fast with storage, for the shrimp stored at low temperature thesituation is just the reverse.2. Collect the electronic nose output signal, the baseline and eigenvalue extractionmethod were determined according to the output signal.3. In the detection of shrimp under different storage conditions using electronic noseexperiment, the output signals of five sensors in the sensor array was increasing with theextension of storage time. The five sensors has a good response to nitrogenous and sulfurcompounds, alcohols and inflammable gas, respectively.4. The technology of headspace solid-phase microextraction gas chromatography-massspectrometry (HS-SPME-GC-MS) was used to analyze changes in the volatile compositionof shrimp stored at25℃. The shrimp sample showed that14kinds compounds aboutshrimp freshness were identified, including six kinds of sulfur compounds, two kinds ofnitrogen compounds, one kind of hydrocarbons, one kind of alcohols, one kind of ketonescompounds, three kinds of esters. the shrimp samples with different freshness showed a bigdifference in their volatile composition. Nitrogen compounds, sulfur compounds and indolewas increasing with storage time. Compared the change rule of output of each sensor ofelectronic nose with the detected results of volatile components, the two test results were better consistent. It has proved that the electronic nose could be tried to assess freshness ofshrimp.5、To detect the shrimp freshness sensor output signal in electronic nose,5℃storedconditions and mixed storage conditions discriminant model of shrimp freshness wasestablished, respectively. The date normalization method is determined by the modeldiscriminant accuracy. In principal components analysis, the principal componentsaccounted for85%of total variation, which can effectively used by fisher lineardiscriminant analysis. The recognition rate of the two models was respectively98.3%and86.3%.Principal component analysis-fisher linear discriminant model could determinationthe freshness of shrimp with high discriminant accuracy and stability．...