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OpisThe aim of this study was to investigate the evolution of the volatile compounds (VOC) from milk to curd during mozzarella manufacturing, in connection with the technique used for curd acidification (traditional = natural whey starter fermentation; industrial = direct acidification by citric acid addition). Overall, 40 compounds were identified from the entire set of samples, belonging to different chemical classes. All compounds detected in milk were also found in the curd, but at much higher concentration. In addition, many other compounds formed during curd production. By comparison of the samples from the 2 acidification techniques, and analysing the scientific literature to explain the source of the volatile compounds, it was found that microbial activity played a main role in VOC formation. In fact, the curd obtained by natural whey starter fermentation showed the most complex profile, whereas that of the curd obtained by direct acidification was much simpler. The most important odour-active compounds that could contribute to flavour of the curd made by traditional technology were 3-methylbutanal, ethyl acetate and 2,3-butanedione, responsible for ethereal, fruity and buttery odour. For direct acidification they were 3-methylbutanal (at lower level), nonanal and decanal (herbal/fruity odour). The PCA analysis showed clear clusterization of the three types of samples: milks and direct acidified curds were rather close in the bi-plot graph, whereas traditional curds were spread all along the space. The research is currently in progress, for assessing the evolution of the volatile compounds during the next technological steps of mozzarella manufacturing.Cilj ovog rada bio je istražiti razvoj hlapivih mliječnih spojeva (VOC) u grušu tijekom proizvodnje sira Mozzarella, ovisno o načinu zakiseljavanja sirnog gruša (tradicionalno = prirodno zakiseljavanje sirutke starter kulturama; industrijski = direktno zakiseljavanje dodatkom limunske kiseline). Iz svih testiranih uzoraka identificirano je ukupno oko 40 spojeva različitog kemijskog sastava. Svi spojevi pronađeni u mlijeku bili su prisutni i u grušu, no u puno višim koncentracijama. Osim toga, u gruševima su bili prisutni i mnogi drugi spojevi. Usporedbom uzoraka zakiseljenih na 2 različita načina utvrđeno je kako je mikrobna aktivnost igrala presudnu ulogu u formiranju VOC. Točnije, gruš zakiseljen prirodnim putem (starter kulturom) imao je najsloženiji profil VOC, dok je gruš zakiseljen dodatkom limunske kiseline bio puno jednostavnijeg sastava. Spojevi koji su u prirodno zakiseljenom grušu najviše doprinosili formiranju okusa i mirisa bili su 3-metilbutanal, etil acetat i 2,3-butandion, a koji su inače nosioci mirisa po eteru, voću i maslacu. U slučaju gruša zakiseljenog dodatkom limunske kiseline, glavni nosioci okusa i mirisa bili su 3-metilbutanal (niska koncentracija), nonanal i dekanal (biljno/voćni miris). PCA analiza je pokazala da dolazi do klasterizacije tri uzorka - mlijeka i gruševa zakiseljenih dodatkom limunske kiseline, dok su prirodno zakiseljeni gruševi bili raspoređeni u širem području. U tijeku je istraživanje kojem je cilj odrediti razvoj hlapivih spojeva tijekom preostalih tehnoloških koraka u procesu proizvodnje sira Mozzarella.
  
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