| Solid-state fermentation is defined as the fermentation involving solids in the absence(or near absence) of free water, however, the substrate must possess enough moisture to support growth and metabolism of micro-organism. Zhenjiang aromatic vinegar is the typical representative of the solid-state fermentation. It is one of the most famous Chinese traditional vinegars. SSF is conducted by mixing alcohol mash with the wheat bran and rice hull in different pots or ponds. An unique cycle-inoculation style that the fermentation culture of the 7th day is used as seed(starter) for the next round of inoculation. Since no additional microbes are supplied during the fermentation process, the microbial community and quality of each fermentation circle are supposed to be comparatively stable. Therefore, the constituents of Zhenjiang aromatic vinegar are quite different from other vinegars, which characterized with a unique aroma and many interesting physiological properties. However, solid-state fermentation is very complex. It involves interactions between microbes and culture where solid, liquid and gaseous exits at the same time. Existing sensory analysis and physicochemical analysis methods cannot meet timely and accurate perception microorganisms in the fermentation culture(vinegar culture) growth and metabolism state. As a result, the quality of fermentation is different among different fermentation time even they have exactly the same technology and the same raw material. Therefore, it is very difficult to industrialization and mechanization of SSF process.In this study, taking Zhenjiang vinegar fermentation process as the research object, we using modern sensor technology, such as biosensing and non-destructive sensing, in-line sensing the physicochemical index of SSF, such as temperature, water, pH et al. Furthermore, dynamic sensing and simulation the spatial and temporal distribution of physicochemical index in the solid fermentation of Zhenjiang Vinegar is obtained through chemometrics and simulation analysis. Finally, the spatial and temporal distribution of physicochemical index in the solid fermentation of Zhenjiang Vinegar could be applied to optimize the turn-over process in solid fermentation. It also could be used to find the optimal operating conditions of vinegar fermentation process, and provide the basic data and theoretical analysis tool. Therefore, this research work can provide protection for the expansion of industrialization of Zhenjiang vinegar. The main reaearch rearch findings have been summarized as following:(1) The dynamic identification of fermentation stage. The aroma profile and the internal metabolic substances of the vinegar cultural are the key factors to identify the fermentation stages. Firstly, the olfaction visualization technique(OVT) was applied to get the aroma profile of vinegar cultural, the colorimetric sensors array of pigments have been created by printing the pigments on hydrophpbic nanoporous films. The basic principle of this technique is to utilize the color change induced by reaction between volatile materials and an array of chemical dyes upon ligand binding for chemical vapor detection and differentiation. A color change profile for each object can be obtained by differentiating the images of the sensor array before and after exposure to the volatile organic compounds(VOCs) of objects. The digital data representing the color change profiles were analyzed with the help of multivariate calibration. Secondly, near infrared spectroscopy(NIR) was applied to get the spectral information of vinegar cultural. Thirdly, the multiple information fusion technology was applied to identify the fermentation stage. In this work, principal component analysis(PCA) was used to reduce the dimensionality of numerical datasets. It can transform original variables into a few new variables, known as principal components(PCs). K-nearest neighbors,(KNN), least squares support vector machine(LS-SVM) and BP artificial neural network(BP-ANN)were used to rapidly identify the fermentation stage. Finally, the algorithm of BP-ANN was the optimum model. The highest classification rate was 91.25 when four the values of the PCs was 7.(2) The temperature was real-time monitored during SSF process, and the multi-dimensional temperature field was simulated by ANSYS software and finite element method(FEM) in this study. A real-time monitoring device was used to monitor the temperature in different fermentation stages and different fermentation layers. The on-line gathering temperature data were carried on the processing at the end of the fermentation experiment, and then the result is the temperature time graph. The temperature changes curves of the different fermentation stage were analyzed. According to the analysis results of temperature, the temperature field was simulated by ANSYS software and FEM.The result showed, along the axis the temperature change from the top to the bottom of the fermentation pot was first to rise and then to decline. The highest temperature and minimum temperature point reaches 6 ℃.The radial direction temperature change from axis to wall temperature gradually reduced. The highest temperature and minimum temperature point reaches 3 ℃.According to the rules of the temperature during SSF process, ANSYS software and FEM were used to simulate temperature multidimensional distributions of the vinegar cultural. The changes rules of the simulation temperature field were similar with the actual detection temperature during SSF. This method can replace the traditional and backward detection means. The results from calculation agree with the experimental results.(3) The hyperspectral imaging technique and chemometrics methods were used for rapid prediction of the main physical and chemical indicators(total acid content, moisture content, pH value and non-volatile acid content) of the vinegar cultural. The two dimension distribution images of these indicators were calculated in order to show the uniformity of the vinegar cultural. In this study, the physical and chemical indicators of the different season and fermentation time were detected by the chemical methods. Mean spectral were extracted fom the hyperspectral images to be correlated with the vinegar cultural using PLS, genetic algorithm PLS(GA-PLS), LS-SVM and BP-ANN. For total acid content and moisture content, the good results were obtained by GA-PLS with correction coefficient(rp) of 0.875 and 0.916, respectively. And for pH value, the good result was obtained by LS-SVM with correction coefficient(rp) of 0.932 and root mean square error of prediction(RMSEP) of 0.048. And for non-volatile acid content, the good result was obtained by BP-ANN with correction coefficient(rp) of 0.894 and root mean square error of prediction(RMSEP) of 0.495 mg/100 g. Finally, as component content, the gray value was stretched and pseudo-color processed to obtain the pseudo-color map of each component. In a word, the fermentation quality and conditions of the vinegar cultural were rapidly monitored by the study of this chapter, which provided the effective means for the next step intelligent operation.(4) The design of intelligent operation was put forward in this study. At present, the operation of the stirred vinegar cultural only solved the problem of the mechanization. To overcome the traditional operation method, the intelligent operation was investigated by multi-information fusion theory. PLC has become the most important industrial automation equipment in the field of industrial control, which supplies a safety and perfect solution for industrial automation. LabVIEW is a graphical software development environment which is introduced by National Instruments(NI). In this study, the PLC and LabVIEW were applied to design the control system of the machine of the stirred operation. The software of the system and the final assembly diagram were detailed described in this chapter. This design of the stirred operation was expected to make big strides forward from mechanization to the intelligence.This research offers a new idea to detect fermentation quality, and there is also of great significance in monitoring SSF process. It was meaningful for promoting the automation and intelligent in the development of double distilled vinegar culture machine. |
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