An integrated approach to explore the microbial biodiversity of natural milk cultures for cheesemaking

The use of natural milk culture (NMC) represents a key factor in PDO Montasio cheeses, contributing to its distinctive sensory profile. The complex microbial ecosystem of NMCs is the result of heat treatment and incubation conditions, which can vary considerably among different production plants. In this study, the microbiota of NMCs collected from 10 PDO Montasio cheese dairies was investigated employing colony counts and metagenomic analysis. Furthermore, residual sugars, organic acids, and volatile profiles were quantitatively investigated. Results showed that Streptococcus thermophilus was the dominant species in all NMCs, and a subdominant population made of other streptococci and L. salivarius was also present. The incubation temperature appeared to be the main driver of biodiversity in NMCs. Metagenomics allowed us to evidence the presence of minor species involving safety (e.g., Staph. aureus) as well as possible functional aspects (Next Generation Probiotics). Statistical analysis based on residual sugars, organic acids, and volatiles' content allowed to correlate the presence of specific microbial groups with metabolites of great technological and sensory relevance, which can contribute to giving value to the artisanal production procedures of NMCs and clarify their role in the creation of the characteristics of PDO Montasio cheese.

1H-NMR Approach for the Discrimination of PDO Grana Padano Cheese from Non-PDO Cheeses

Protected Designation of Origin cheeses are products with high-quality standards that can claim higher prices on the market. For this reason, non-PDO cheeses with lower quality can be mislabeled as PDO or mixed with it for economic gain especially when the product is in a shredded form. Luckily, the production of PDO cheese is subjected to strict procedural specification rules that result in a product with a defined profile of its metabolites, which can be used for authentication purposes. In this study, an NMR metabolomic approach combined with multivariate analysis was implemented to build a classification model able to discriminate PDO Grana Padano cheese from a large dataset of competitors. The great advantage of the proposed approach is a simple sample preparation, obtaining a holistic overview of the analyzed samples. The untargeted approach highlighted a "typical profile" of Grana Padano samples, which could be used for protection purposes. In parallel, the targeted results allowed us to identify potential chemicals, such as lactate, some amino acids and lipids. These initial results could open the road to a potential new additional tool to check the authenticity of PDO cheeses in the future.

A Genotyping Method for Detecting Foreign Buffalo Material in Mozzarella di Bufala Campana Cheese Using Allele-Specific- and Single-Tube Heminested-Polymerase Chain Reaction

Mozzarella di Bufala Campana (MdBC) cheese is a Protected Designation of Origin (PDO) product that is important for the economy and cultural heritage of the Campania region. Food fraud can undermine consumers' trust in this dairy product and harm the livelihood of local producers. The current methods for detecting adulteration in MdBC cheese due to the use of buffalo material from foreign countries could exhibit limitations associated with the required use of expensive equipment, time-consuming procedures, and specialized personnel. To address these limits here, we propose a rapid, reliable, and cost-effective genotyping method that can detect foreign buffalo milk in a counterpart from the PDO area and in MdBC cheese, ensuring the quality and authenticity of the latter dairy product. This method is based on dedicated allele-specific and single-tube heminested polymerase chain reaction procedures. By using allele-specific primers that are designed to detect the nucleotide g.472G>C mutation of the CSN1S1B^bt allele, we distinguished an amplicon of 330 bp in the amplification product of DNA when extracted from milk and cheese, which is specific to the material originating from foreign countries. By spiking foreign milk samples with known amounts of the counterpart from the PDO area, the sensitivity of this assay was determined to be 0.01% v/v foreign to PDO milk. Based on a rough estimate of its simplicity, reliability, and cost, this method could be a valuable tool for identifying adulterated buffalo PDO dairy products.

The Impact of Different Inoculation Schemes on the Microbiota, Physicochemical and Sensory Characteristics of Greek Kopanisti Cheese throughout Production and Ripening

Kopanisti is a Greek PDO cheese, which is traditionally produced by the addition of an amount of over-mature Kopanisti, called Mana Kopanisti, to initiate cheese ripening. The aim of this study was the production of four types of Kopanisti cheese (A-D) using pasteurized cow milk, and a combination of the following starters/adjuncts in order to test their ability to be used in Kopanisti cheese production: A: Lactococcus lactis subsp. lactis and Lacticaseibacillus paracasei, B: L. lactis and Lc. paracasei/Mana Kopanisti, C: L. lactis and Lc. paracasei/Ligilactobacillus acidipiscis and Loigolactobacillus rennini, D: Lig. acidipiscis and Loig. rennini. Throughout production and ripening, classical microbiological, metataxonomics and physicochemical analyses were employed, while the final products (Day 35) were subjected to sensory analysis as well. Most interestingly, beta-diversity analysis of the metataxonomics data revealed the clusters constructed among the Kopanisti types based on the different inoculation schemes. On day 35, Kopanisti A-C types clustered together due to their similar 16S microbiota, while Kopanisti D was highly differentiated. On the contrary, ITS data clustered Kopanisti B and C together, while Kopanisti A and D were grouped seperately. Finally, based on the sensory evaluation, Kopanisti C appeared to have the most suitable bacteria cocktail for the Kopanisti cheese production. Therefore, not only were the conventional starters used, but also the Lig. acidipiscis and Loig. rennini strains could be used in a standardized Kopanisti cheese production that could lead to final products of high quality and safety.

Evaluating the Authenticity of the Raw-Milk Cheese Fontina (PDO) with Respect to Similar Cheeses

The implementation of quality assurance schemes for the assessment of PDO food authenticity is an issue involving manufacturers, traders, retailers and consumers. In this respect, reliable analytical methods are needed to integrate paper-trailing information. The feasibility of distinguishing the Italian Fontina PDO cheese from the generic Fontal cheese was preliminarily evaluated on a set of commercial samples by measuring selected parameters (pH, alkaline phosphatase activity, content of copper, volatiles, extent of proteolysis) related to the different manufacturing processes. The relative profile of free amino acids proved to be a promising tool. A new set of 41 samples of Fontina PDO cheese was collected at representative dairies within the recognized production area and analyzed for free amino acids. A chemometric model of Fontina PDO cheese was built based on the mean content and standard deviation of 15 free amino acids. On this basis, all of the PDO samples were correctly identified, whereas all of the Fontal cheeses were recognized as different cheeses.

Prediction of indicators of cow diet composition and authentication of feeding specifications of Protected Designation of Origin cheese using mid-infrared spectroscopy on milk

The ability of mid-infrared spectroscopy (MIR) to predict indicators (1) of diet composition in dairy herds and (2) for the authentication of the cow feeding restrictions included in the specification of 2 Protected Designation of Origin (PDO) cheeses (Cantal and Laguiole) was tested on 7,607 bulk milk spectra from 1,355 farms located in the Massif Central area of France. For each milk sample, the corresponding cow diet composition data were obtained through on-farm surveys. The cow diet compositions varied largely (i.e., from full grazing for extensive farming systems to corn silage-based diets, which are typical of more intensive farming systems). Partial least square regression and discriminant analysis were used to predict the proportion of different feedstuffs in the cows' diets and to authenticate the cow feeding restrictions for the PDO cheese specifications, respectively. The groups for the discriminant analysis were created by dividing the data set according to the threshold of a specific feedstuff. They were issued based on the specifications of the restriction of the PDO cheese. The pasture proportion in the cows' diets was predicted by MIR with an coefficient of determination in external validation (R²V) = 0.81 and a standard error of prediction of 11.7% dry matter. Pasture + hay, corn silage, conserved herbage, fermented forage, and total herbage proportion in the cows' diets were predicted with a R²V >0.61 and a standard error of prediction <14.8. The discrimination models for pasture presence, pasture ≥50%, and pasture ≥57% in the cows' diets achieved an accuracy and specificity ≥90%. A sensitivity and precision ≥85% were also observed for the pasture proportion discrimination models, but both of these indexes decreased at increasing thresholds from 0 to 50, and 57% pasture in the cows' diets. An accuracy ≥80% was also observed for pasture + hay ≥72%, herbage ≥50%, pasture + hay ≥25%, absence of fermented herbage, absence of corn silage, and corn silage ≤30% in the cows' diets, but for several models, either the sensitivity or precision was lower than the accuracy. Models built on the simultaneous respect of all the criteria of the feeding restrictions of PDO cheese specifications achieved an accuracy, specificity, sensitivity, and precision >90%. Both the regression and discriminant MIR models for bulk milk can provide useful indicators of cow diet composition and PDO cheese specifications to producers and consumers (farmers, dairy plants).

Assessing the authenticity of animal rennet using δ15N analysis of chymosin

Chymosin is a protease that curdles the milk casein. Animal rennet was the first discovered source of chymosin and its use is mandatory for the production of PDO cheeses such as Parmigiano Reggiano and Grana Padano. Of the alternatives, fermentation-produced chymosin is the most competitive because it functions in a similar way, but is much cheaper. Analytical tools are necessary in order to distinguish the 2 types of chymosin and verify the compulsory use of animal rennet in the production of PDO cheeses. In this work, a method to analyse ¹⁵N/¹⁴N in chymosin after extraction was developed. The δ¹⁵N values of animal rennet range from 5.7‰ to 8‰, whereas the δ¹⁵N values of fermentation-produced chymosin are significantly lower, ranging from -5.3‰ to 2.2‰. A threshold value of 5.7‰ was defined for authentic animal rennet. Addition of fermentation-produced chymosin to animal rennet, or its complete substitution, can be therefore detected.

Cheese: Food Perception and Food Choice

In light of the increasing interest in the economic and socio-political impact of the 'traditional food' trend, it is essential to understand the determinant factors that lead to traditional consumer choices. The standardization of sensory quality evaluation methods marks the pressing need for food product certification, particularly foods with specific sensory characteristics, such as those with a Protected Designation of Origin (PDO). Consumer perception of particular foods, especially for foods that are culturally and socially contingent, such as cheese, must be understood as both a psychophysical reflex and a learned social practice. Consumers create their own perceptions based on the overall intrinsic or extrinsic cheese characteristics, mainly sensory characteristics that reflect others' attributes. These characteristics are normally linked to the specific cheese manufacture process. Some patents propose the use of adapted cheesemaking equipment (EP1982582A2), suitable for the manufacture of small-scale cheeses, such as some PDO cheese. Thus, sensory evaluation of any kind of cheese is based, in the initial phase, on knowledge of the sensory methods for cheese evaluation and, in a second phase, on the familiarity of the cheese characteristics and verbalization of desirable and undesirable attributes. This paper presents a case study based on the traditional food product, Évora cheese, assembled with PDO cheeses, whose sensory and physicochemical quality attributes are essential in order to obtain this designation and ensure the genuine properties that characterize them, as well as ascertaining exactly how they are perceived and further accepted by the consumer.

Development of a Quantitative GC-MS Method for the Detection of Cyclopropane Fatty Acids in Cheese as New Molecular Markers for Parmigiano Reggiano Authentication

Cyclopropane fatty acids (CPFA), as lactobacillic acid and dihydrosterculic acid, are components of bacterial membranes and have been recently detected in milk and in dairy products from cows fed with corn silage. In this paper, a specific quantitative gas chromatography-mass spectrometry (GC-MS) method for the detection of CPFA in cheeses was developed, and the quality parameters of the method (limit of detection, limit of quantitation, and intralaboratory precision) were assessed. Limit of detection and quantitation of CPFA were, respectively, 60 and 200 mg/kg of cheese fat, and the intralaboratory precision, determined on three concentration levels, satisfied the Horwitz equation. This method was applied to 304 samples of PDO cheeses of certified origin, including Parmigiano Reggiano (Italy), Grana Padano (Italy), Fontina (Italy), Comté (France), and Gruyère (Switzerland). Results showed that CPFA were absent in all of the cheeses whose Production Specification Rules expressly forbid the use of silages (Parmigiano Reggiano, Fontina, Comté, and Gruyère). CPFA were instead present in variable concentrations (300-830 mg/kg of fat) in all of the samples of Grana Padano cheese (silages admitted). A mix of grated Parmigiano Reggiano and Grana Padano was also prepared, showing that the method is able to detect the counterfeiting of Parmigiano Reggiano with other cheeses up to 10-20% Grana Padano content. These results support the hypothesis that CPFA can be used as a marker of silage feedings for cheeses, and the data reported can be considered a first attempt to create a database for CPFA presence in PDO cheeses.