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Ragusano is a raw milk pasta-filata cheese produced in the southeastern region of Sicily at farmhouse level using natural rennet and traditional wooden tools. The cheese manufacturing process involves two rounds of cooking, stretching of the overnight-ripened curd, moulding, brining and aging. Slight differences in the manufacturing process among producers lead to different flavor and texture of the final product. In an attempt to define the key steps of the process that lead to a safe cheese, we monitored the production of PDO Ragusano cheese in five farms. During each of three subsequent days, two blocks of Ragusano were produced per farm, for an overall count of thirty blocks of cheese. Chemical and microbiological analysis were performed on milk, production intermediates and different sections (sub-rind, intermediate, and core) of cheese aged for 2, 3 and 4 months. Results point to the importance of the second cooking of the curd as a key step in establishing the necessary conditions for a fast acidification. In fact, in the only farm where this step takes place for 10 minutes only (as opposed to an average length of 150 minutes), acidification of the curd appears to be noticeably slower, with a concomitant higher susceptibility to contamination. Manufacturing conditions proved to be very effective in causing death of the small number of Staphylococcus aureus cells found as contaminants of raw milk. No contaminations by Listeria monocytogenes, Salmonellae and Escherichia coli were detected at any stage of the process. On the other hand, after 2 months from manufacturing already, cheeses showed water activity levels which are hardly compatible with growth of the above mentioned pathogens, and which decreased further with subsequent aging. Our results show that the cheese-making technology of Ragusano guarantees high levels of microbiological safety as long as good practices are mantained throughout the entire process. The high temperatures used for cooking and stretching the curd, fast acidification, low aw values and high salt content contribute to make Ragusano a hostile environment for the growth of pathogens. [ABSTRACT FROM AUTHOR]

Raw milk from 13 cows fed TMR supplemented with native pasture and from 13 cows fed only TMR on one farm was collected separately 4 times with an interval of 15 d between collections. Two blocks (14 kg each) of cheese were made from each milk. The objective was to determine the influence of consumption of native plants in Sicilian pastures on the aroma compounds present in Ragusano cheese. Milk from cows that consumed native pasture plants produced cheeses with more odor-active compounds. In 4-mo-old cheese made from milk of pasture-fed cows, 27 odor-active compounds were identified, whereas only 13 were detected in cheese made from milk of total mixed ration-fed cows. The pasture cheeses were much more rich in odor-active aldehyde, ester, and terpenoid compounds than cheeses from cows fed only total mixed ration. A total of 8 unique aroma-active compounds (i.e., not reported in other cheeses evaluated by gas chromatography olfactory) were detected in Ragusano cheese made from milk from cows consuming native Sicilian pasture plants. These compounds were 2 aldehydes ([E,E]-2,4-octadienal and dodecanal), 2 esters (geranyl acetate and [E]-methyl jasmonate), 1 sulfur compound (methionol), and 3 terpenoid compounds (1-carvone, L(-) carvone, and citronellol). Geranyl acetate and (E)-methyl jasmonate were particularly interesting because these compounds are released from fresh plants as they are being damaged and are part of a possible plant defense mechanism against damage from insects. Most of the odor-active compounds that were unique in Ragusano cheese from pasture-fed cows appeared to be compounds created by oxidation processes in the plants that may have occurred during foraging and ingestion by the cow. Some odor-active compounds were consistently present in pasture cheeses that were not detected in the total mixed ration cheeses or in the 14 species of pasture plants analyzed. Either these compounds were present in other plants not analyzed, created in the rum... [ABSTRACT FROM AUTHOR]