TRACEABILITY OF MOUNTAIN CHEESES: IDENTIFICATION AND CHARACTERIZATION OF BIOCHEMICAL MARKERS

Food traceability and knowledge of the relationship between production processing and food composition have become subjects of great interest during the last decade, due to the increasing demand for genuineness, high quality, and origin assurance of food. In the last few years several researchers have approached the problem of food authenticity and, in the dairy field, many papers dealing with the traceability of the origin of milk and cheese have been published. In particular, studies have been carried out to differentiate between highland cheeses, produced by animals feeding on pasture, and cheeses of lowland origin by examining the volatile compounds that can be transferred from forage into milk and cheese. Besides volatile compounds, extensively considered in literature as biochemical markers of origin, even non-volatile hydrocarbons molecules could be of interest to evaluate cheese traceability. Therefore this PhD thesis focused on the study of the composition of the non-volatile minor components of the neutral lipid fraction in mountain dairy products, obtained from animals feeding on pasture, and in milk and cheese samples produced from cows under intensive breeding, fed with concentrates and silages. These neutral components were separated, by silica gel column chromatography, from the whole lipid matrix and analyzed by GC/MS. The main compounds detected, in all the samples analyzed, belonged to the following chemical classes: n-alkanes, fatty acid ethyl esters, fatty acid methyl esters, saturated and unsaturated isoprenoid hydrocarbons, cholesteryl esters and phytyl esters. According to the aim of this work, i.e. the detection of possible markers of traceability, the attention was focussed on the compounds having a proved relationship with the feeding and not influenced by technological processes. Thus the isoprenoid hydrocarbon 1-phytene, 2-phytene and neophytadiene (phytenes) and the n-alkanes were selected for further evaluation. Phytenes molecules derived, through different biosynthetic pathways, from dietary phytol of chlorophyll by the action of rumen bacteria. Since n-alkanes are important components of vegetable matrix, they are abundant in plant cuticular waxes and they are inert in the digestive tract of ruminants. Milk and cheese samples of highland origin were characterized by higher amounts of these molecules than those of lowland origin. In order to provide a parameter able to differentiate the two groups of dairy products, independent on usual factors affecting the natural variability particularly of mountain pasture (botanical composition, phenological stage, meteorology conditions etc.), some ratios between n-alkanes and phytenes were tested. The ratio obtained between the sum of phytenes (1-phytene, 2-phytene and neophytadiene) and octadecane allowed a good discrimination according to the feeding system adopted. Since the hydrocarbon fraction of highland dairy products resulted particularly rich in n-alkanes and phytenes, it was investigated whether the concentration of these compounds in cheese could be affected by different types of mountain pasture. Two typical alpine dairy productions were studied: Asiago and Toma Piemontese. For both productions, the cheeses were obtained from milk of two groups of animals fed on different vegetation types: rich fescue (P) and poor fescue (M) for Asiago d’Allevo; red fescue (F) and alpine clover (T) for Toma Piemontese. The results allowed, throughout two years of experimentation, a different relationship between the concentration of some constituents of the hydrocarbon fraction, which was closely related to the different botanical composition of the vegetation types. In particular, the ratio 1-phytene/2-phytene allowed a good discrimination between the two groups of the Asiago cheese, while the ratio between nonacosane and heptacosane was more effective to differentiate the two groups of Toma Piemontese cheese. Moreover the fatty acid composition of Asiago and Toma Piemontese cheeses was studied. It was evaluated whether the fatty acids were able to differentiate the same cheese, but produced by feeding cows with a different pasture. The results obtained are an important starting point for the advancement of studies on the relationship between "pasture and cheese". Above all, the identification of reliable and repeatable markers to define mountain dairy products traceability could be useful for the development of typical mountain productions.