# Proteomics Analysis in Dairy Products: Cheese, a Review
## 9 Adulteration and Proteomics  
Over the past few years there is a growing consumers' movement regarding products' originality and their distinction from their counterfeit counterparts. Moreover, consumers are interested in the correlation of food products and history. An excellent example regarding history and cheese, is Feta and its ties with ancient Greece through unique traits and characteristics. [PERSON] and [PERSON] [188] tried to gather the full protein content of Feta cheese by employing exhaustive deep-proteome analyses using LC/MS-MS. They collected Feta samples from every Greek area that produces PDO labeled Feta cheese and reported the complete list of Feta cheese proteins. The analysis of Feta contains 489 distinct proteins and eventually this method can be used as an identification tool of the authentic Greek product [188]. Other studies tried to elucidate the caseins behavior through ripening of Feta cheese. [PERSON] et al. [29] stated that in Feta cheese as1-CN seemed to be further hydrolyzed; a decrease has been observed during ripening. The formation of as1-CN is important because it indicates that the N-terminus of as1-CN has been hydrolyzed during the ripening of Feta cheese. Para-\(\kappa\)-casein is the hydrophobic part of \(\kappa\)-casein and is a component of the paracasein matrix in cheese curd. Chymosin or renet are added to form the coagulum and the residuals of the enzymes have proteolytic action to the paracasein matrix, with \(\alpha\)1- and \(\beta\)-caseins being the most susceptible whereas \(\alpha\)s2- and para-\(\kappa\)-casein rather resistant to their action during cheese ripening. [PERSON] and [PERSON] [189] stated that the greatest part of para-\(\kappa\)-casein remained intact during ripening and storage of Feta with high residual chymosin activity, although other studies indicated the opposite [190, 191]. The positive aspect in their findings is that since para-\(\kappa\)-casein remains intact, it can be used for the quantification of the composition of mixtures of sheep and goat cheese milk and other adulterations, even though the para-\(\kappa\)-casein is similar but not identical in the two species. The latter characteristic was proved by cation-exchange HPLC. In particular, sheep and goat para-\(\kappa\)-casein were efficiently separated, and the changes of their chromatographic areas indicated that hydrolysis happened during the early stages of ripening. Thereafter, and in accordance to the evolution of free amino groups, para-\(\kappa\)-caseins remained stable [189]. One of the main consumers' concerns is the milk origin of the PDO cheeseses they are buying, which also is applied to Mozzarella di Bufala Campana. One of the cheese-making rules is that the milk must come from Mediterranean water buffalo raised in Italy. Caseins are fully incorporated in cheese and they can create a \"fingerprint\" useful for the identification of milk samples origin [10]. Mediterranean Italian buffalo is reared in Italy for centuries and is a pure breed without any crosses with animals from other countries, as being indicated by their casein polymorphism absence. The \(\beta\)-CN locus was found to be monomorphic [192] and \(\alpha\)s1-CN showed only two silent variants [193] in Mediterranean Italian buffalo while milk samples from Romanian, Canadian, Polish and Venezuelan WB displayed additional CN variants, such as \(\beta\)-CN A and \(\alpha\)s1-CN with eight internally deleted amino acid residues in positions 35-42 [192]. The new caseins variants have been detected in all the foreign countries, but not in the Mediterranean area, proving that WB herds in the Mediterranean area are pure without any crossbreeding, thus proving that the region of milk origin is significant for the PDO labeling in Mozzarella di Bufala Campana [10]. The above-mentioned traits of WB caseins allowed [PERSON] et al.