Cocoa bean fingerprinting via correlation networks

Abstract

Cocoa products have a remarkable chemical and sensory complexity. However, in contrast to other fermentation processes in the food industry, cocoa bean fermentation is left essentially uncontrolled and is devoid of standardization. Questions of food authenticity and food quality are hence particularly challenging for cocoa. Here we provide an illustration how network science can support food fingerprinting and food authenticity research. Using a large dataset of 140 cocoa samples comprising three cocoa fermentation/processing stages and eight countries, we obtain correlation networks between the cocoa samples by computing measures of pairwise correlation from their liquid chromatography-mass spectrometry (LC-MS) profiles. We find that the topology of correlation networks derived from untargeted LC-MS profiles is indicative of the fermentation and processing stage as well as the origin country of cocoa samples. Progressively increasing the correlation threshold firstly reveals network clusters based on processing stage and later country-based clusters. We present both, qualitative and quantitative evidence through network visualization, network statistics and concepts from machine learning. In our view, this network-based approach for classifying mass spectrometry data has broad applicability beyond cocoa.

Children of Nature: Thoughts on Targeted and Untargeted Analytical Approaches to Decipher Polyphenol Reactivity in Food Processing and Metabolism

“…31 Correlation networks allow identification of constituents potentially related to a given property of the sample. 32 ■ CHEMICAL REACTIVITY IN FOOD PROCESSING Polyphenols are highly reactive chemical entities. They can be easily oxidized to form stabilized radical intermediates that consequently yield quinone structures.…”

“…Here, to obtain meaningful information, normalization and scaling routines and the amount of data fed into the algorithm constitutes the most important parameter to consider in practice . Correlation networks allow identification of constituents potentially related to a given property of the sample …”

Authentication of Cocoa Products Based on Profiling and Fingerprinting Approaches: Assessment of Geographical, Varietal, Agricultural and Processing Features

“…This technique, combined mainly with PCA, has been used to distinguish the geographic origin [ 50 , 51 , 52 , 53 ] as well as product quality [ 54 ] or cocoa genotype [ 50 ]. Similarly, LC-MS is extensively used for obtaining characteristic fingerprints that, after being treated with the appropriate chemometric methodology, enable the discrimination of products based on geographical origin, fermentation stage or cultivar [ 55 , 56 , 57 , 58 ]. Apart from these more common applications, an untargeted LC-MS approach was also established for determining the adulteration of cocoa powder with chicory and carob and soy flours [ 59 ].…”

Biogenic Solution Map Based on the Definition of the Metabolic Correlation Distance between 4-Dimensional Fingerprints

“…Alternatively, correlations among fingerprints of the same species can be visualized by networking, wherein nodes representing fingerprints are connected if their similarities are on top ranking. 20 The connections do not quantitatively reflect correlations. Thus, the number of connections, as well as the cluster coefficient of networking, is heavily dependent on the preset parameters of the networking algorithm.…”

“…However, simply answering compliance or non-compliance between a test and reference materials is sometimes insufficient. Alternatively, correlations among fingerprints of the same species can be visualized by networking, wherein nodes representing fingerprints are connected if their similarities are on top ranking . The connections do not quantitatively reflect correlations.…”