Spotting Frozen Curd in PDO Buffalo Mozzarella Cheese Through Insights on Its Supramolecular Structure Acquired by 1H TD-NMR Relaxation Experiments

Abstract

The addition of frozen curd (FC) during the production process of “Mozzarella di Bufala Campana”, an Italian cheese with Protected Designation of Origin (PDO), is a common fraud not involving modifications of the chemical composition in the final product. Its detection cannot thus be easily obtained by common analytical methods, which are targeted at changes in concentrations of diagnostic chemical species. In this work, the possibility of spotting this fraud by focusing on the modifications of the supramolecular structure of the food matrix, detected by time domain nuclear magnetic resonance (TD-NMR) experiments, was investigated. Cheese samples were manufactured in triplicate, according to the PDO disciplinary of production, except for using variable amounts of FC (i.e., 0, 15, 30, and 50% w/w). Relaxation data were analysed through different approaches: (i) Discrete multi-exponential fitting, (ii) continuous Laplace inverse fitting, and (iii) chemometrics approach. The strategy that lead to best detection results was the chemometrics analysis of raw Carr-Purcell-Meiboom-Gill (CPMG) decays, allowing to discriminate between compliant and adulterated samples, with as low as 15% of FC addition. The strategy is based on the use of machine learning for projection on latent structures of raw CPMG data and classification tasks for fraud detection, using quadratic discriminant analysis. By coupling TD-NMR raw decays with machine learning, this work opens the way to set up a system for detecting common food frauds modifying the matrix structure, for which no official authentication methods are yet available.

Assessment of cheese frauds, and relevant detection methods: A systematic review

“… ( Mafra et al, 2007 ) Italy Buffalo Mozzarella Adding frozen curd (FC) TD-NMR experiments coupled with machine learning can be successfully used to detect common FFs. ( Mengucci et al, 2021 ) Italy Caprine and ovine Fraudulent addition of bovine milk A real-time PCR test was developed for detecting cow’s milk in caprine and ovine cheeses based on two target genes. Most of the 30 caprines and 51 ovine cheese samples were adulterated.…”

“…In this method, the proton relaxation (transversal relaxation, T2) is monitored and provides information about the mobility of the nuclei, also unique information about bound water, free water, and an exchange between these two states ( Qu & Jin, 2022 ). Mengucci et al (2021) investigated the adulteration of Mozzarella di Bufala Campana, an Italian cheese with frozen curd that during the production process is known as a frequent fraud, and can’t be easily recognized by general analyzing methods, mainly because they focus on chemical composition. Using this newly improved technique, dehydration of caseins in cheese samples that were affected by frozen and refrigerated storage could be detected.…”

“…In this experiment, researchers made four groups of samples from “Mozzarella di Bufala Campana” containing 0, 15, 30, and 50 % FC. They concluded that TD-NMR coupled with machine learning can be useful for fraud identification, especially when the structural level is altered and not the chemical composition ( Mengucci et al, 2021 ). After all, due to its advantages like simple and fast measurement procedures and instrumental stability, this method has been investigated in the past few years and declared to be a useful method for controlling food quality and identifying fraud.…”

Near‐infrared spectroscopy: A possible routine analysis to detect the use of frozen curds in the production of Buffalo Mozzarella cheese

“…More recently, the method studied by Mengucci et al . (2021) based on time‐domain nuclear magnetic resonance (TD‐NMR) experiments coupled with chemometrics has been considered a starting point for the development of a new detection system. According to these authors, this method is indeed appropriate in case of adulterations with changes occurring at the structural level.…”

The multivariate effect of chemical and oxidative characteristics of Buffalo Mozzarella cheese produced with different contents of frozen curd

“…2021; Mengucci et al . 2021), but there are no studies focused on oxidation changes due to the addition of frozen milk or curd. The oxidative stability of milk and dairy products, in addition to contrasting lipid and protein oxidation, has great importance for human nutrition, also contributing to body defences against oxidation (Citta et al .…”