Automatic milking systems in the Protected Designation of Origin Montasio cheese production chain: effects on milk and cheese quality.

Montasio cheese is a typical Italian semi-hard, semi-cooked cheese produced in northeastern Italy from unpasteurized (raw or thermised) cow milk. The Protected Designation of Origin label regulations for Montasio cheese require that local milk be used from twice-daily milking. The number of farms milking with automatic milking systems (AMS) has increased rapidly in the last few years in the Montasio production area. The objective of this study was to evaluate the effects of a variation in milking frequency, associated with the adoption of an automatic milking system, on milk quality and on the specific characteristics of Montasio cheese. Fourteen farms were chosen, all located in the Montasio production area, with an average herd size of 60 (Simmental, Holstein-Friesian, and Brown Swiss breeds). In 7 experimental farms, the cows were milked 3 times per day with an AMS, whereas in the other 7 control farms, cows were milked twice daily in conventional milking parlors (CMP). The study showed that the main components, the hygienic quality, and the cheese-making features of milk were not affected by the milking system adopted. In fact, the control and experimental milks did not reveal a statistically significant difference in fat, protein, and lactose contents; in the casein index; or in the HPLC profiles of casein and whey protein fractions. Milk from farms that used an AMS always showed somatic cell counts and total bacterial counts below the legal limits imposed by European Union regulations for raw milk. Finally, bulk milk clotting characteristics (clotting time, curd firmness, and time to curd firmness of 20mm) did not differ between milk from AMS and milk from CMP. Montasio cheese was made from milk collected from the 2 groups of farms milking either with AMS or with CMP. Three different cheese-making trials were performed during the year at different times. As expected, considering the results of the milk analysis, the moisture, fat, and protein contents of the experimental and control cheeses were comparable. The milking system was not seen to significantly affect the biochemical processes associated with ripening. In fact, all cheeses showed a normal proteolysis trend and a characteristic volatile compound profile during aging. Therefore, the milking system does not appear to modify the distinctive characteristics of this cheese that remain dependent on the area and methodology of production.

Characterization by solid-phase microextraction-gas chromatography of the volatile profile of protected designation of origin Montasio cheese during ripening.

Montasio is a typical protected designation of origin (PDO) Italian semi-hard and semi-cooked cheese produced in northeast Italy from raw or thermized cow's milk. The PDO label implies that the product has distinctive characteristics that are connected to traditional production methods. The aim of this work was to precisely characterize the volatile fraction of this Italian cheese. The volatile profile can be considered a fingerprint because the flavor of a cheese variety is the result of a specific balance between the volatile compounds produced during the ripening process. Analysis of the volatile profile of Montasio cheese was performed by solid-phase microextraction-gas chromatography. Six cheesemaking trials were performed, each in a different dairy located within the Montasio cheese production area. Cheeses were analyzed at 5 stages of ripening (60, 90, 170, 300, and 365 d). Only 11 compounds were identified and measured: 5 fatty acids, 3 alcohols, 2 ketones, and 1 ester. The limited number of volatile compounds measured in the headspace of the Montasio cheese is probably due to the specific making process of this cheese, which affects evolution of the microflora and the biochemical processes of ripening. The total volatile fraction profile progressively increased from 60 to 170 d, after which time it remained almost steady. The most important contributors were found to be ethanol, short-chain fatty acids (C(2) to C(6)), diacetyl, and ethyl hexanoate. Ethanol and short-chain fatty acids increased up to 170 d, diacetyl increased up to 300 d and then declined, and ethyl hexanoate increased until the final stage.

Dynamic high pressure-induced gelation in milk protein model systems.

The structure-functional properties of milk proteins are relevant in food formulation. Recently, there has been growing interest in dynamic high-pressure homogenization effects on the rheological-structural properties of food macromolecules and proteins. The aim of this work was to evaluate the effects of different homogenization pressures on rheological properties of milk protein model systems. For this purpose, sodium caseinate (SC) and whey protein concentrate (WPC) were dispersed at different concentrations (1, 2, and 4%), pasteurized, and then homogenized at 0, 18MPa (conventional pressure, CP), 100MPa (high pressure, HP), and 150MPa (HP+). Differences in viscosity were observed between WPC and casein dispersions according to concentration, heat treatment, and homogenization pressure. Mechanical spectra described the characteristic behavior of solutions except for the WPC 4% pasteurized sample, in which a network formed but was broken after homogenization. Dispersions with different ratios of WPC and SC were also made. In these systems, pasteurization alone did not determine network formation, whereas homogenization alone promoted cold gelation. A total concentration of at least 4% was required for homogenization-induced gelation in pasteurized and unpasteurized samples. Gels with higher elastic modulus (G') were obtained in more concentrated samples, and a bell-shaped behavior with the maximum value at HP was observed. The HP treatment produced stronger gels than the CP treatment. Similar G' values were obtained when different concentrations, pasteurization conditions, and homogenization pressures were combined. Therefore, by setting appropriate process conditions, systems or gels with tailored characteristics may be obtained from dispersions of milk proteins.

Effect of high-pressure homogenization on droplet size distribution and rheological properties of ice cream mixes.

The effect of different homogenization pressures (15/3 MPa and 97/3 MPa) on fat globule size and distribution as well as on structure-property relationships of ice cream mixes was investigated. Dynamic light scattering, steady shear, and dynamic rheological analyses were performed on mixes with different fat contents (5 and 8%) and different aging times (4 and 20 h). The homogenization of ice cream mixes determined a change from bimodal to monomodal particle size distributions and a reduction in the mean particle diameter. Mean fat globule diameters were reduced at higher pressure, but the homogenization effect on size reduction was less marked with the highest fat content. The rheological behavior of mixes was influenced by both the dispersed and the continuous phases. Higher fat contents caused greater viscosity and dynamic moduli. The lower homogenization pressure (15/3 MPa) mainly affected the dispersed phase and resulted in a more pronounced viscosity reduction in the higher fat content mixes. High-pressure homogenization (97/3 MPa) greatly enhanced the viscoelastic properties and the apparent viscosity. Rheological results indicated that unhomogenized and 15/3 MPa homogenized mixes behaved as weak gels. The 97/3 MPa treatment led to stronger gels, perhaps as the overall result of a network rearrangement or interpenetrating network formation, and the fat globules were found to behave as interactive fillers. High-pressure homogenization determined the apparent viscosity of 5% fat to be comparable to that of 8% fat unhomogenized mix.

Formation of biogenic amines in a typical semihard Italian cheese.

Given that the concentration of biogenic amines in cheeses depends on variety, age, and type of microflora, a study was undertaken to investigate the formation of these compounds during the ripening of a typical semihard Italian cheese. Tryptamine, phenylethylamine, putrescine, cadaverine, histamine, and tyramine contents were calculated in 30 samples of Montasio cheese characterized by different levels of proteolysis. Histamine and tyramine were the major amines. Tryptamine and phenylethylamine concentrations were very low at all ripening periods. Putrescine and cadaverine were present only in samples with anomalous fermentation processes. The relationship between the total amine content and the proteolytic maturation coefficient was calculated; however, even for higher levels of proteolysis, the biogenic amine content in Montasio cheese was below the level considered potentially toxic.

A rapid method for the quantitative determination of short-chain free volatile fatty acids from cheese.

The determination of free volatile fatty acids (FVFA) is of interest in the analysis of cheeses. As these compounds are components of taste and flavor, they give indications on metabolic reactions taking place during cheese ripening and can provide an evaluation of cheese defects and their causes. One of the most widely used methods for the determination of FVFA in cheese involves preliminary recovery from the matrix by steam distillation, followed by gas chromatography separation. Relatively high distillate volumes must be collected to achieve a quantitative yield of all the compounds of interest, so that, as a result, the solution is too diluted to achieve good instrumental sensitivity. In this paper, an alternative method for the determination of C2-C6 free carboxylic acids in cheeses involving the use of a Nukol capillary column and crotonic acid as internal standard is described. This method is quick and cheap, as the sample preparation is a simple extraction with water. The underivatized FVFA are then directly separated by gas chromatography. Using this method, all FVFA in cheeses can be quantified with good repeatability and excellent recovery.