Mass spectrometry detection of fraudulent use of cow whey in water buffalo, sheep, or goat Italian ricotta cheese.

Ricotta cheese is a typical Italian product, made with whey from various species, including cow, buffalo, sheep, and goat. Ricotta cheese nominally manufactured from the last three species may be fraudulently produced using the comparatively cheaper cow whey. Exposing such food frauds requires a reliable analytical method. Despite the extensive similarities shared by whey proteins of the four species, a mass spectrometry-based analytical method was developed that exploits three species-specific peptides derived from ß-lactoglobulin and α-lactalbumin. This method can detect as little as 0.5% bovine whey in ricotta cheese from the other three species. Furthermore, a tight correlation was found (R(2)>0.99) between cow whey percentages and mass spectrometry measurements throughout the 1-50% range. Thus, this method can be used for forensic detection of ricotta cheese adulteration and, if properly validated, to provide quantitative evaluations.

Detection of fraudulent addition of bovine whey in water buffalo ricotta cheese by isoelectric focusing.

BACKGROUND: Prevention of food fraud in the dairy field is a difficult issue for researchers, industries and policy makers, both for commercial and health reasons. Currently, no analytical method allows detection of the addition of bovine whey to water buffalo ricotta, so this fraudulent practice cannot be prevented. The authors' aim was to develop such a method. RESULTS: The conditions for extraction and purification of denatured ricotta whey proteins, which are unfolded and coagulated by heating during the production process, were optimized. The optimal composition of the polyacrylamide gel (pH range, type and concentration of chemical separator) was first evaluated and then the best conditions to perform the separation by isoelectric focusing were established. The performance of the method (precision, selectivity, robustness, sensibility) was determined. CONCLUSIONS: The method was shown to be reliable and robust for detection of the presence of bovine whey added to water buffalo Ricotta at percentages above 5% (v/v). The results suggest that the differences observed between bovine and water buffalo electrophoretic profiles are due to bovine ß-lactoglobulin isoform A, which is never detected in water buffalo samples.

Fatty acid composition and δ13 C of bulk and individual fatty acids as marker for authenticating Italian PDO/PGI extra virgin olive oils by means of isotopic ratio mass spectrometry.

European Regulation (EEC) 2568/91 has been setting the minimum requirements in order to allow labeling of oil as extra virgin. These general requirements, are based on physical-chemical and organoleptic parameters directly linked to the freshness and quality of the product. Isotope ratio mass spectrometry (IRMS) was demonstrated to be a useful tool for the discrimination of the origin of unknown samples, because the obtained data are practically independent of the cultivar employed and the production technique. In this work, the evaluation of the composition of fatty acid methyl esters (FAME) alongside with the determination of stable isotope ratio of C in bulk oils and in main FAME constituents have been investigated as a tool to improve geographical discrimination of Italian Protected Designation of Origin/Protected Geographical Indication (PDO/PGI) samples. For this purpose, authentic PDO/PGI extra virgin olive oils were sampled at oil mills and grouped into different sets according to their areas of provenience. The use of principal component analysis and partial least squares discriminant analysis multivariate analysis techniques demonstrated that discrimination of olive oil samples can be done using geographical and pedoclimatic parameters predominantly by using δ(13) C results of bulk and individual fatty acids. Results showed that δ(13) C values are a more reliable marker of origin with respect to fatty acid composition.

Multi-detection of preservatives in cheeses by liquid chromatography-tandem mass spectrometry.

The incorrect use of preservatives in cheeses may compromise food safety and damage consumers. According to the law, more than one preservative may be contemporarily used in cheeses. So a method for their contemporary detection may be useful for both manufacturers and control agencies quality control. In this research a liquid chromatography-tandem mass spectrometric with electrospray ionization method for the multi-determination of seven preservatives (benzoic acid, citric acid, hexamethylenetetramine, lysozyme, natamycin, nisin and sorbic acid) in cheese was developed. The preservatives were contemporarily extracted from cheese by a single procedure, and analyzed by RP-LC/ESI-MS/MS (Ion Trap) in positive ionization mode, with single reaction monitoring (SRM) acquisition. Three sample types (hard, pasta filata and fresh cheese) were used for method evaluation. Recoveries were mostly higher than 90%; MDLs ranged from 0.02 to 0.26 mgkg(-1), and MQLs were included between 0.07 and 0.88 mgkg(-1). Due to matrix effect, quantitation was performed by referring to a matrix matched calibration curve, for each cheese typology. This method was also applied to commercial cheese samples, with good results. It appears fast, reliable and suitable for both screening and confirmation of the presence and quantitation of the preservatives in a single, multi-detection analysis.

Development of an RP-HPLC method for the simultaneous determination of benzoic acid, sorbic acid, natamycin and lysozyme in hard and pasta filata cheeses.

A single method, based on RP-HPLC with UV detection, was developed with the aim of simultaneously quantifying four preservatives in cheeses: benzoic acid, sorbic acid, natamycin and lysozyme. The preservatives were extracted from different cheeses by using the same procedure, and separated by a single RP-HPLC gradient elution showing good resolution, in a short time. Recoveries were always higher than 91%; MDLs ranged from 0.4 to 4.0µgg(-1), and MQLs were included between 1.3 and 13.3µgg(-1); RDS ranged from 1% to 7%. Quantitation was performed in reference to a matrix matched calibration curve. The method was also applied to real samples for the determination of the four preservatives, with satisfying results.

Peptidomic approach, based on liquid chromatography/electrospray ionization tandem mass spectrometry, for detecting sheep's milk in goat's and cow's cheeses.

A common fraud in the dairy field is the addition of sheep's milk to goat's cheeses, because it has a very similar taste to goat's milk, but is more available, and is commonly considered to have a better capacity to curdle. For similar reasons, and due to economic convenience, sheep's cheeses may also contain fraudulent cow's milk. In order to detect this fraud, an EU official method may be used, but it is only a qualitative method (presence/absence of cow's milk). A method able to quantify the presence of sheep's milk during cheese production in goat's and cow's cheeses was developed. The method is based on liquid chromatography/electrospray ionization tandem mass spectrometry (LC/ESI-MS/MS) analysis of peptides of a casein extract from the cheese. By a simple procedure, caseins are extracted from cheeses, solubilized, digested with plasmin, and subsequently analyzed by LC/ESI-MS/MS. A typical sheep's peptide produced by plasmin hydrolysis (m/z = 860) was accurately selected and analyzed to understand if, and by how much, a declared pure goat's cheese contains sheep's milk. By analyzing the same peptide it is also possible to detect if, and by how much, a declared pure sheep's milk contains, or not, cow's milk. The method was applied to several goat's and cow's cheese samples. Quantitation was performed with a calibration curve obtained by analyzing curd cheeses containing different percentages of sheep's milk. The method detection limit and method quantitation limit were evaluated. This method appears accurate and suitable for detecting up to 2% of sheep's milk in cheeses.