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3 (1-10)
NaslovMolekularna identifikacija kvasaca iz svježeg mlijeka i tradicionalno proizvedenog svježeg sira / Manuela Zadravec, Vesna Jaki Tkalec, Sanja Furmeg, Maja Kiš, Mario Mitak, Tomislav Mikuš.
Materijalni opisIlustr., graf. prikazi.
Način izrade datotekeizvorno digitalna građa
Vrstačlanak
OpisKvasci su česti zagađivači mliječnih proizvoda, međutim, koriste se i kao starter kulture za poboljšavanje svojstava finalnog proizvoda. Njihova prisutnost u povećanom broju može prouzročiti nepoželjne promjene mliječnih proizvoda, kao što su neugodan miris, okus i izgled. Klasična identifikacija kvasaca na temelju morfoloških i biokemijskih svojstava spora je i nepouzdana. Cilj rada bio je identificirati kvasce iz 30 uzoraka mlijeka i svježeg sira te ustvrditi pripadaju li izolirani kvasci u poželjne ili nepoželjne vrste, odnosno predstavljaju li potencijalni rizik po zdravlje ljudi. Izolirani kvasci identificirani su sekvenciranjem D1/D2 regije gena 28 S rRNK. Dobivenim sekvencama ustvrđeno je da izolirani kvasci pripadaju vrstama: Kluyveromyces marxianus, Candida tropicalis, Trichosporon coremiiforme, Rhodotorula mucilaginosa, Trichosporon ovoides, Pichia kudriavzevii, Issatchenkia orientalis, koje se smatraju kvascima zagađenja te Debaryomyces hansenii vrsti koja se može koristiti i kao starter kultura. S obzirom da kvasci nisu termorezistentni mikroorganizmi, trebali bi biti uklonjeni tijekom pasterizacije, no u tradicionalnom načinu proizvodnje sira mlijeko se termički ne obrađuje, stoga je povećan rizik od pojavnosti kvasaca u finalnom proizvodu. Izolirane se vrste vrlo često nalaze i u okolišu i/ili na ljudima, odnosno životinjama. Stoga se nameće zaključak kako se glavnina kontaminacije kvascima događa kao posljedica neadekvatne higijenske prakse.Yeasts are a common contaminant of dairy products, but they can also be used as a starter culture to improve the characteristics of the final product. Their presence in an increased number causes undesirable changes in dairy products, such as an unpleasant appearance, acrid smell and foul taste. The classical identification of yeasts based on morphological and biochemical properties is slow and unreliable. The aim of this study was to identify isolated yeasts from 30 dairy products, and to determine if they belong to desired or undesirable species. Isolated yeasts were identified by sequencing the D1/D2 domain of the gene 28S rRNA. The obtained sequences determined that the isolated yeasts belong to the species: Kluyveromyces marxianus, Candida tropicalis, Trichosporon coremiiforme, Rhodotorula mucilaginosa, Trichosporon ovoides, Pichia kudriavzevii, Issatchenkia orientalis, which are considered contaminants, and Debaryomyces hansenii, a species that can be used as a starter culture. Since yeasts are not thermoresistant microorganisms, they should be removed during pasteurization. However, milk is not heat-treated in traditional cheese-making production, thus increasing the risk of yeast in the final product. These isolated species are very often found in the environment and/or on humans and animals therefore, it can be concluded that the majority of yeast contamination occurs as a result of inadequate hygiene.
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NaslovNalaz patogenih bakterija u sirovom mlijeku i mliječnim proizvodima s posebnim osvrtom na vrstu Yersinia enterocolitica / Vesna Jaki Tkalec, Sanja Furmeg, Maja Kiš, Jadranka Sokolović, Miroslav Benić, Luka Cvetnić, Željko Pavlinec, Silvio Špičić, Željko Cvetnić.
Materijalni opisGraf. prikazi.
Način izrade datotekeizvorno digitalna građa
Vrstačlanak
OpisU sjeverozapadnoj Hrvatskoj meki svježi sir se tradicionalno proizvodi po nepisanoj recepturi od sirovog kravljeg mlijeka. Mlijeko predstavlja idealan supstrat za rast i razmnožavanje brojnih mikroorganizama, mnogih uzročnika zoonoza tako i vrste Y. enterocolitica. Tijekom naših istraživanja pretraženo je 159 uzoraka, od toga 109 uzoraka sirovog kravljeg mlijeka i 50 uzoraka svježeg kravljeg sira i vrhnja. Y. enterocolitica izdvojena je iz 2 (1,8 %) uzorka sirovog mlijeka. Od 50 uzoraka mliječnih proizvoda (sir i vrhnje) u 16 (32 %) dokazana je E.coli, u 12 (24 %) uzoraka S. aureus te u 1 (2 %) uzoraka L. innocua. Osim njih u 15 (13,8 %) uzoraka sirovog mlijeka i 24 (48 %) uzoraka svježeg sira i vrhnja izdvojene su enterobakterije, a biokemijski su identificirane vrste: S. marcescens, S. liquefaciens, M. morganii, C. freundii i C. braakii. Bakterije iz roda Salmonella i L. monocytogenes nisu dokazane u istraživanim uzorcima. Nakon provedene biokemijske identifikacije, dva soja identificirana kao vrsta Y. enterocolitica pretraženi su na molekularnoj razini, molekularnom pretragom dobiven je potvrdni rezultat samo kod jednog uzorka, što je usporedivo s rezultatima drugim istraživanja. Zbog zahtjevne identifikacije bakterijske vrste Y. enterocolitica, kombiniranom primjenom uzgojnih i molekularnih metoda dobiju se pouzdaniji i brži rezultati identifikacije. Sirovo mlijeko i vrhnje od sirovog mlijeka izvor su patogenih mikroorganizama (E. coli i S. aureus) i drugih enterobakterija, a našim istraživanjem dokazali smo i patogenu bakterijsku vrstu Y. enterocolitica koja predstavlja potencijalni rizik za zdravlje potrošača i u Republici Hrvatskoj. Y. enterocolitica je znatno otporna na procese u proizvodnji hrane (dezinfekcija, niski pH, salinitet, preživljavanje u hladnijim uvjetima) te u budućnosti zaslužuje veću pažnju i nadzor u proizvodnji hrane.In northwestern Croatia, soft fresh cheese is produced using traditional, unwritten recipes of raw cow milk. Milk is an ideal substrate for the growth and reproduction of numerous microorganisms, many zoonotic agents and the species Y. enterocolitica. In this study, 159 samples were tested: 109 samples of raw cow milk and 50 samples of fresh cow cheese and cream. Y. enterocolitica was detected in 2 (1.8%) samples of raw milk. E. coli was detected in 16 (32%) of 50 samples of dairy products (cheese and cream). S. aureus was detected in 12 (24%) samples and L. innocua in 1 (2%) sample. Additionally, 15 (13.8%) samples of raw milk and 24 (48%) samples of fresh cheese and cream also harboured enterobacteria, identified biochemically as: S. marcescens, S. liquefaciens, M. morganii, C. freundii and C. braakii. Salmonella and L. monocytogenes were detected in any of the samples. After the biochemical identification, two strains identified as Y. enterocolitica were examined at the molecular level, and the molecular test confirmed the result in only one sample, which is comparable to the results of other studies. Due to the demanding identification of the bacterial species Y. enterocolitica, the combined application of breeding and molecular methods produces more reliable and faster identification results. Raw milk and crude milk cream are a source of pathogenic microorganisms (E. coli and S. aureus) and other enterobacteria, while this study also found the presence of the pathogenic bacterial species Y. enterocolitica, presenting a potential consumer health risk in the Republic of Croatia. Y. enterocolitica is considerably resistant to food production processes (disinfection, low pH, salinity, survival in cold conditions) and deserves greater attention and supervision in food production in the future.
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NaslovThe effect of thermal processing on the reduction of deoxynivalenol and zearalenone cereal content / Jelka Pleadin, Jurislav Babić, Ana Vulić, Nina Kudumija, Krunoslav Aladić, Maja Kiš, Vesna Jaki Tkalec, Mario Škrivanko, Marica Lolić, Drago Šubarić.
Materijalni opisGraf. prikazi.
Način izrade datotekeizvorno digitalna građa
Vrstačlanak
OpisFusarium mycotoxins deoxynivalenol (DON) and zearalenone (ZEN) often contaminate cereals and cereal by-products. Certain thermal processing methods used in the food industry show promising results in terms of reduction of cereal contamination with mycotoxins. In order to establish the degree of DON and ZEN reduction in naturally contaminated cereals (maize, wheat and oat), this study investigated the effects of cooking, roasting and extrusion cooking, performed at different temperatures (100 – 220 °C) and for a different length of time (10 – 30 min) on these mycotoxins concentrations. Before and after the treatment, cereal samples were analysed for DON and ZEN concentrations using enzyme-linked immunosorbent assay (ELISA). In comparison to cooking, which achieved only a negligible mean mycotoxin reduction (of up to 8% for DON and 11% for ZEN), roasting and extrusion cooking resulted in a significantly more pronounced mycotoxin reduction (of up to 40% for DON & 46% for ZEN and of up to 75% for DON & 80% for ZEN, respectively) (p <0.05). The results show similar effects of thermal processing on all of the studied cereals (p >0.05), suggesting that extrusion cooking can be considered as an effective thermal method capable of reducing mycotoxin content in cereals.
rrep
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3 (1-10)