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Antimicrobial properties of different hop (Humulus lupulus) genotypes
Zala Kolenc, Tomaž Langerholc, Gregor Hostnik, Miha Ocvirk, Sara Štumpf, Maša Pintarič, Iztok Jože Košir, Andreja Čerenak, Alenka Garmut, Urban Bren, 2023, original scientific article

Abstract: The antimicrobial activity of hop extracts obtained from different hop genotypes were investigated against Staphylococcus aureus and Lactobacillus acidophilus. In this study the pure xanthohumol, purified β-acids rich fraction, as well as α-acids with β-acids rich fraction were used to test antimicrobial activity against Staphylococcus aureus and Lactobacillus acidophilus; whereby, the antimicrobial activity of different hop extracts against Lactobacillus acidophilus was studied for the first time. Microbial susceptibility to purified hydroacetonic extracts from different hop varieties was investigated by the broth microdilution assay to determine the minimum inhibitory concentration (MIC) and the minimum bactericidal concentration (MBC). The hop hydroacetonic extracts were more effective against Staphylococcus aureus than against Lactobacillus acidophilus. Strong inverse correlations of MIC and MBC values were obtained with xanthohumol, cohumulone, n+adhumulone, colupulone and n+adlupulone contents, suggesting that the identified chemical hop compounds are directly responsible for antimicrobial effects. Moreover, the effect of the growth medium strength on the MIC values of hop extracts against Staphylococcus aureus was systematically investigated for the first time. The current study also reveals the effect of different hop extracts on Staphylococcus aureus, which responds to their presence by lag phase extension and generation time prolongation.
Keywords: hop extract, xanthohumol, Staphylococcus aureus, Lactobacillus acidophilus, minimum inhibitory concentration, minimum bactericidal concentration
Published in DKUM: 09.05.2024; Views: 91; Downloads: 3
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Antioxidant activity of different hop (Humulus lupulus L.) genotypes
Zala Kolenc, Tamara Hribernik, Tomaž Langerholc, Maša Pintarič, Maja Prevolnik Povše, Urban Bren, 2023, original scientific article

Abstract: The antioxidant activity (AA) of hop extracts obtained from different hop genotypes (n = 14) was studied. For comparison, the purified β-acids-rich fraction and α-acids-with-β-acids-rich fraction were also used to test the antioxidative potential. The AA of purified hydroacetonic hop extracts was investigated using the Ferric Reducing Ability of Plasma (FRAP), Oxygen Radical Absorption Capacity (ORAC) and Intracellular Antioxidant (IA) methods. The FRAP values in different hop genotypes ranged between 63.5 and 101.6 μmol Trolox equivalent (TE)/g dry weight (DW), the ORAC values ranged between 1069 and 1910 μmol TE/g DW and IA potential values ranged between 52.7 and 118.0 mmol TE/g DW. Significant differences in AA between hop genotypes were observed with all three methods. AAs were determined using three different methods, which did not highly correlate with each other. We also did not find significant correlations between AA and different chemical components, which applies both to AA determined using individual methods as well as the total AA. Based on this fact, we assume that the synergistic or antagonistic effects between hop compounds have a more pronounced effect on AA than the presence and quantity of individual hop compounds.
Keywords: hop, antioxidant activity, FRAP, ORAC, intracellular antioxidative potential, genotypes
Published in DKUM: 20.03.2024; Views: 171; Downloads: 7
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Food risk analysis : Towards a better understanding of “hazard” and “risk” in EU food legislation
Ana-Andreea Cioca, Livija Tušar, Tomaž Langerholc, 2023, original scientific article

Abstract: For risk communication, it is important to understand the difference between “hazard” and “risk”. Definitions can be found in Codex Alimentarius and the European Union (EU) General Food Regulation (EC) No. 178/2002. The use of these terms as synonyms or their interchange is a recurrent issue in the area of food safety, despite awareness-raising messages sent by EFSA (European Food Safety Authority) and other interested entities. A quick screening of the EU’s food regulations revealed several inconsistencies. Hence, it was considered necessary to further investigate if regulations could act as a source for this problem. A software tool was developed to support the detection and listing of inconsistent translations of “hazard” and “risk” in certain EU food regulations. Subsequently, native-speaking experts working in food safety from each EU country were asked to provide their individual scientific opinion on the prepared list. All data were statistically analysed after applying numerical scores (1–5) describing different levels of consistency. Results showed that the most common problem was the interchange of “hazard” with “risk” and vice versa. This lack of consistency can create confusion that can further translate into misjudgments at food risk assessment and communication levels.
Keywords: risk analysis, risk communication, hazard, risk, food regulation, food safety
Published in DKUM: 12.03.2024; Views: 326; Downloads: 340
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The Influence of Chestnut Extract and Its Components on Antibacterial Activity against Staphylococcus aureus
Sara Štumpf, Gregor Hostnik, Tomaž Langerholc, Maša Pintarič, Zala Kolenc, Urban Bren, 2023, original scientific article

Abstract: Increasing antimicrobial resistance has caused a great interest in natural products as alternatives or potentiators of antibiotics. The objective of this study was to isolate individual tannins from crude chestnut extract as well as to determine the influence of both crude extracts (tannic acid extract, chestnut extract) and individual pure tannins (gallic acid, vescalin, vescalagin, castalin, castalagin) on the growth of Gram-positive Staphylococcus aureus bacteria. Their antibacterial activity was monitored by measuring the minimum inhibitory concentration (MIC) and minimum bactericidal concentration (MBC) as well as the duration of the lag phase, growth rate and generation time. The effect of growth medium strength on the MIC of different tannins was also investigated. Bacterial growth was followed spectrophotometrically, and MIC values were determined by the microdilution method. The MIC values of various isolated compounds allowed us to determine the bioactive compounds and their contribution to antimicrobial activity. It was found that MIC values increase with increasing growth medium strength and that the lag phase lengthens with increasing tannin concentrations, while the growth rates decrease. Comparing the results of the two studies, the antimicrobial activity of tannins against S. aureus was not as pronounced as in the case of E. coli, which may indicate that a different mechanism of action is responsible for the antimicrobial effects of tannins on Gram-positive than on Gram-negative bacteria, or that a different mechanism is more pronounced.
Keywords: tannins, antibacterial activity, MIC, MBC, Staphylococcus aureus, lag phase, generation time
Published in DKUM: 20.02.2024; Views: 254; Downloads: 57
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Application of Lactobacillus reuteri B1/1 (Limosilactobacillus reuteri) improves immunological profile of the non-carcinogenic porcine-derived enterocytes
Viera Karaffová, Jana Teleky, Maša Pintarič, Tomaž Langerholc, Dagmar Mudroňová, Erik Hudec, Zuzana Ševčíková, 2023, original scientific article

Abstract: In our previous studies, Lactobacillus reuteri B1/1, which was renamed Limosilactobacillus reuteri (L. reuteri), was able to modulate the production of pro-inflammatory cytokines and other components of the innate immune response in vitro and in vivo. In this study, we evaluated the effect of Lactobacillus reuteri B1/1 in two concentrations (1 x 10(7) and 1 x 10(9) CFU) on the metabolic activity, adherence ability and relative gene expression of pro-inflammatory interleukins (IL-1 beta, IL-6, IL-8, IL-18), lumican and olfactomedin 4 produced by non-carcinogenic porcine-derived enterocytes (CLAB). CLAB cells were cultured in a 12-well cell culture plate at a concentration of 4 x 10(5) cells/well in DMEM medium in a controlled humidified atmosphere for 48 h. A 1 mL volume of each probiotic bacterial suspension was added to the CLAB cells. Plates were incubated for 2 h and 4 h. Our results revealed that L. reuteri B1/1 was able to adhere to CLAB cells in sufficient numbers in both concentrations. In particular, the concentration of 109 L. reuteri B1/1 allowed to modulate the gene expression of pro-inflammatory cytokines, as well as to increase the metabolic activity of the cells. In addition, administration of L. reuteri B1/1 in both concentrations significantly stimulated gene expression for both proteins in the CLAB cell line after 4 h of incubation.
Keywords: Lactobacillus reuteri B1/1, CLAB cells, pro-inflammatory cytokine, metabolic activity
Published in DKUM: 20.02.2024; Views: 160; Downloads: 8
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Ocena kulture varnosti živil na osnovi znanja vedenja in odnosa zaposlenih v gostinstvu : magistrsko delo
Biserka Keramitchievska, 2024, master's thesis

Abstract: Slaba kultura varnosti hrane je vedno večji dejavnik tveganja za izbruhe bolezni, ki se prenašajo s hrano. Ocena kulture varnosti hrane je pomembno orodje za analizo znanja o varnosti hrane in vedenja zaposlenih pri delu z živili. Vzpostavitev pozitivne kulture varnosti hrane med zaposlenimi v gostinstvu zahteva zavzetost vodstva, odnos zaposlenih glede varnosti hrane, organizacijske in administrativne značilnosti prehranskega obrata, zavedanje o tveganju in upoštevanje izgorelosti zaposlenih. Namen magistrskega dela je bil s pregledom literature in z uporabo polstrukturiranega intervjuja oceniti kulturo varnosti hrane na osnovi znanja in odnosa zaposlenih v gostinstvu na vzorcu zaposlenih pri delu z živili v gostinski dejavnosti. V raziskavi je sodelovalo 11 zaposlenih v gostinstvu (dve ženski in devet moških). Vsi so imeli več kot osem let delovnih izkušenj. S pomočjo kvalitativne vsebinske analize smo pridobili tri teme: zagotavljanje varnosti hrane, dejavniki, ki vplivajo na kulturo varnosti hrane, in izzivi pri zagotavljanju pozitivne kulture varnosti hrane. Na podlagi pregleda strokovnih in znanstvenih objav ter polstrukturiranih intervjujev smo ugotovili, da je treba dvigniti raven kulture varnosti hrane v izbranih restavracijah in da se intervjuvanci načeloma zavedajo pomembnosti elementov zagotavljanja varnosti hrane, vendar se držijo pravil predvsem zaradi stalnega nadzora in groženj zniževanja plač. Glavni kuharji imajo visoko znanje o pravilih varnosti hrane, vendar imajo težave pri vodenju novozaposlenih in neizkušenih zaposlenih.
Keywords: varnost hrane, kultura varnosti hrane, tveganja, ocena kulture varnosti hrane
Published in DKUM: 30.01.2024; Views: 318; Downloads: 28
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Načrt trženja in možnosti vstopa nizko-alergenega a2-mleka na trg : magistrsko delo
Marina Lakatuš, 2023, master's thesis

Abstract: Nizko-alergeno A2-mleko predstavlja inovativno in zdravju prijazno alternativo za potrošnike z intoleranco na laktozo ali prebavnimi težavami. V magistrski nalogi smo se osredotočili najprej na načrt trženja in analizo možnosti vstopa nizko-alergenega A2-mleka kmetije Sinkovič na trg. Temeljito smo proučili analizo trga, identifikacijo ciljnih segmentov potrošnikov in prepoznavanje njihovih potreb, želja ter preferenc. Raziskovali smo tržne priložnosti in izzive, da identificiramo potencialne ciljne segmente, ki bi lahko imeli največjo naklonjenost in povpraševanje po nizko-alergenem A2-mleku. Na podlagi pridobljenih podatkov smo ugotovili, da bodo stroški marketinga znašali 2.174 € letno. Z analizo SWOT smo analizirali prednosti, slabosti, priložnosti in nevarnosti vstopa A2-mleka na trg. Poslovni model canvas je bil uporabljen kot orodje za lažje razumevanje različnih segmentov podjetja. Nadalje se je z oceno ekonomike ocenila ekonomičnost pridelave A2-mleka. Rezultati kažejo, da je pridelava A2-mleka ekonomsko upravičena, saj koeficient ekonomičnosti (KE) glede na izračune znaša 2,60.
Keywords: načrt trženja, A2-mleko, SWOT analiza, canvas.
Published in DKUM: 10.10.2023; Views: 368; Downloads: 36
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Implementation of food matrix effects into chemical food contaminant risk assessment
Ana-Andreea Cioca, Tomaž Langerholc, Livija Tušar, 2022, original scientific article

Abstract: Food risk assessment plays an important role in protecting public health worldwide. Stakeholders involved in food risk assessment, such as national authorities, agencies, non-governmental organisations (NGOs), industry and consumers, need to properly understand the terminology of food risk assessment effectively. In this respect, the first part of the EU-FORA work programme (WP1) aimed to provide insights into the actual translation of two essential terms used in food risk assessment. ‘Hazard’ and ‘risk’ were first identified and compared between the English version of various food regulations and their equivalents in the national legislation of EU Member States. The comparison and critical evaluation revealed several inconsistencies. These inconsistencies could lead to misinterpretations, followed by errors in conducting risk assessments or communicating risks. We recommend that consistency is restored and maintained so that the message is properly communicated. The second part of the work programme (WP2) was focused on a specific area within chemical risk assessment (CRA). In this context, special attention was given to the impact of the food matrix on the bioaccessibility and bioavailability of heavy metals and metalloids. After collection and careful selection of data from scientific journals, a database with information on the bioaccessibility and bioavailability of cadmium (Cd), lead (Pb), mercury (Hg) and arsenic (As) in different food matrices was created for future statistical analyses related to dietary exposure.
Keywords: hazard, risk, food regulation, chemical contaminants, bioavailability, bioaccessibility, food matrix
Published in DKUM: 18.09.2023; Views: 390; Downloads: 15
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Vpliv probiotikov na zdravljenje in ponovitve okužb sečil pri otrocih
Katarina Meštrović Popovič, 2023, doctoral dissertation

Abstract: Okužbe sečil (OS) v otroški dobi so pogoste in lahko vodijo v pozne zapleti. Pri skoraj tretjini otrok se lahko OS ponovijo in nekateri otroci potrebujejo antibiotično zaščitno. Namen naše raziskave je bil ugotoviti, ali imajo probiotiki ugoden učinek pri zdravljenju in preprečevanju OS pri otrocih, glede na mehanizem nastanka OS in značilnosti probiotikov. Podobnih večjih raziskav na tem področju nismo zasledili. Najprej smo predklinično testirali učinkovitost nekaterih probiotikov na Escherichio coli (E. coli), najpogostejšo povzročiteljico OS in občutljivost probiotikov na antibiotike. Večina probiotikov je pokazala za polovico manjši učinek na E. coli od antibiotikov. Najoptimalnejši probiotični sev, Lactobacillus plantarum PCS 26 (PCS 26), smo nato uporabili v pilotski, dvojno slepi, randomizirani, s placebom kontrolirani, prospektivni raziskavi, v kateri smo preverjali njegovo učinkovitost pri zdravljenju in preprečevanju OS pri otrocih. Raziskava je potekala l.2016 na Otroškem odd. Splošne bolnišnice Celje. Vključili smo 30 otrok z OS, ki so med zdravljenjem in nato še pol leta prejemali probiotk/placebo. Otroci, ki so ob antibiotiku prejemali probiotik, so potrebovali 1,5 dan krajši čas antibiotičnega zdravljenja in 2 dni manj hospitalizacije. Manj otrok s probiotikom je imelo ponovitev OS. Potrebne bodo študije na večjem, bolj homogenem vzorcu otrok, za potrditev rezultatov te pilotske študije.
Keywords: probiotiki, okuţbe sečil, antibiotiĉna zašĉita, otroci, uropatogena E. coli (UPEC), Lactobacillus plantarum.
Published in DKUM: 24.05.2023; Views: 612; Downloads: 70
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Vpliv ksilitola na strukturo in metabolizem črevesne mikrobiote v dinamičnem simulatorja črevesja : master's thesis
Špela Celcar, 2022, master's thesis

Abstract: Ksilitol je sladkorni alkohol, ki se uporablja kot sladilo v številnih živilskih produktih. V veliki meri so ga raziskovali zaradi njegovih učinkov v ustni votlini, raziskav o njegovem vplivu na človeško črevesno mikrobioto pa ni veliko. V tem magistrskem delu smo proučevali od odmerka odvisen učinek ksilitola (1, 3 in 5 g/L) na sestavo in metabolizem črevesne mikrobiote z uporabo dinamičnega črevesnega simulatorja mikrobiote debelega črevesa. Koncentracijo KVMK smo določili s HPLC sistemom s primerjavo retencijskega časa s standardi, amonij pa z Nesslerjevim reagentom. Absolutna kvantifikacija mikrobnih skupin je bila izvedena s qPCR. Statistična analiza rezultatov je pokazala, da dodatek ksilitola povzroči statistično značilne spremembe v številu bakterij Faecalibacterium, Roseburia, Bifidobacterium, Lactobacillus, Akkermansia in Blautia coccoides. Poleg tega se je metabolizem črevesne mikrobiote ob dodatku ksilitola statistično značilno spremenil, saj se je ob povečevanju koncentracije ksilitola koncentracija butirata povečala, koncentracija acetata in propionata pa zmanjšala v primerjavi s kontrolo. Poleg tega je statistična analiza pokazala statistično značilno negativno korelacijo med koncentracijo ksilitola in koncentracijo amonija. Koncentracijo KVMK je mogoče razlagati z mehanizmi navzkrižnega hranjenja med bakterijami. Na podlagi rezultatov lahko sklepamo, da ksilitol kaže prebiotične učinke na črevesno mikrobioto s povečanjem nastajanja koristnih metabolitov, zlasti butirata. Regulacija interakcije med ksilitolom, črevesno mikrobioto in metabolizmom potrebuje nadaljnje raziskave.
Keywords: simulator črevesja, ksilitol, črevesna mikrobiota, kratkoverižne maščobne kisline
Published in DKUM: 05.01.2023; Views: 419; Downloads: 52
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