Feasibility Study on Detecting the Freshness of Chilled Pork Based on Functionalized MOFs Gas-Sensitive Materials Combined With Fluorescence Spectroscopy

Metal Organic Frameworks (MOFs) are a kind of inorganic coordination porous framework materials with high specific surface area, and diverse and flexible structures. It has great application prospects in volatile organic compounds adsorption, sensing, etc. The evaluation of freshness is of great importance to the development of the meat industry. When meat deteriorates, the volatile substances will be produced, which is sensitive to changes in the freshness of meat. Therefore, this study prepared a kind of MOFs composite film based on fluorescence spectra to indicate thefreshness of chilled pork. Then a PLS quantitative analysis model was established according to the response information of the membrane to deteriorating volatile compounds and the freshness index of corresponding pork samples (TVB-N value). It is proved to be a new technology for monitoring the quality deterioration of chilled meat. The main conclusions are as follows: with the ratio of zinc nitrate hexahydrate terephthalic acid= 2 : 1, and a concentration of 2 x 10(-3) mol center dot L-1 Rhodamine B is added, RhB@ MOF-5 is prepared and then characterized. According to the infrared spectra change of RhB@MOF-5 before and after adsorbing the stale smell of chilled pork, amines might be absorbed into it during meat deterioration. After wards, MOF composite film was prepared with the ratio of MOF : PVDF(w/w) = 4 : 5 according to the mixed matrix method. The storage experiment showed that MOFs composite films could stabilise and maintain the fluorescence intensity for at least 60 days in a 4 degrees C dark environment. In addition, the MOFs composite membrane combined with fluorescence sensing technology was used to adsorb and respond to volatile compounds during the entire deterioration period of chilled pork, and we observed the changes in its fluorescence properties. At the same time, three-dimensional fluorescence technology was used to observe that the intensity of MOF-5 and Rhodamine B correlation peaks were weakened after adsorption. It is because the Rhodamine B electron cloud changes caused by amines, resulting in fluorescence quenching. Collecting the surface fluorescence spectra at the excitation wavelength of 340 nm, the response information of two characteristic peaks with emission wavelengths of 435 and 550 nm and TVB-N value can be obtained simultaneously. A freshness index indication model of TVB-N was established by PLS combined with surface fluorescence spectraat the excitation wavelength of 340 nm. R-C(2), R-P(2), RMSEC and RMSEP were 0. 908, 0. 821, 3. 435 and 3. 647 mg center dot (100 g)(-1) respectively, showing the model's good prediction accuracy. The results showed that the functional MOFs composite films could be used to predict the freshness of chilled pork.