Detection of the Inoculated Fermentation Process of Apo Pickle Based on a Colorimetric Sensor Array Method

Abstract

Apo pickle is a traditional Chinese fermented vegetable. However, the traditional fermentation process of Apo pickle is slow, easy to ruin, and cannot be judged with regard to time. To improve fermentation, LP-165 (L. Plantarum), which has a high salt tolerance, acidification, and growth capacity, was chosen as the starter culture. Meanwhile, a colorimetric sensor array (CSA) sensitive to pickle volatile compounds was developed to differentiate Apo pickles at varying degrees of fermentation. The color components were extracted from each dye in the color change profiles and were analyzed using principal component analysis (PCA) and linear discriminant analysis (LDA). The fermentation process of the Apo pickle was classified into four phases by LDA. The accuracy of backward substitution verification was 99% and the accuracy of cross validation was 92.7%. Furthermore, the partial least squares regression (PLSR) showed that data from the CSA were correlated with pH total acid, lactic acid, and volatile acids of the Apo pickle. These results illustrate that the CSA reacts quickly to inoculated Apo pickle and could be used to detect fermentation.

Study on the Characteristics of Vacuum-Bagged Fermentation of Apo Pickle and Visualization Array Analysis of the Fermentation Process

“…The acid content increased during the VBA fermentati process, and the brightness of the CSA color-difference maps of indicator points 2 and sensitive to pH change gradually increased, while the color of the color-difference ma of points 1, 5, and 8 sensitive to aldehydes changed at different fermentation times. Com pared with the different images obtained by Wang et al [14], the visual difference betwe the difference image obtained in different fermentation states in this study is more obv ous.…”

“…PH and TTA are two main parameters of pickle fermentation [22]. When pH drops to about 4, and TTA > 7 g/kg, Apo pickle is mature [14]. The PH of VBA and TBA decreased steadily throughout the fermentation, reaching about 4 on the 30th day (Figure 1A).…”

“…In this study, a simple CSA was prepared to react with VBA samples at different fermentation stages. Compared with CSA prepared by Wang et al [14], We added aldehyde-sensitive indicator points to improve the detection sensitivity of CSA. The CSA color-difference maps of VBA during fermentation are shown in Figure 7A.…”

“…It uses the idea that volatile organic compounds (VOC) cross-react with chemically reactive materials to cause color variations that can be used to detect sample status [11]. CSA technology is currently being utilized to identify the fermentation process of several foods that ferment, such as apple vinegar [12] and black tea [13], and it can also detect the fermentation process of Apo pickle [14]. By improving the indicator points in the array, the detection ability of CSA can be improved.…”