Bakterije i kvasci, a ponekad i filamentozne plijesni u kefirnim zrnima žive u složenom simbiotskom odnosu koji kefirna zrna čini jedinstvenom mikrobnom zajednicom u prirodi. Složenost i kompleksnost ...njihove fizičke i mikrobne strukture razlogom su što su kefirna zrna još uvijek mikrobiološki nedovoljno i nepotpuno istražena. U istraživanju mikrobnog sastava kefirnih zrna koriste se različiti mikrobiološki i molekularni pristupi. Razvojem metagenomike, bazirane na identifikaciji bez kultivacije, otvaraju se nove mogućnosti identifikacije do sada još neidentificiranih mikrobnih vrsta sadržanih u kefirnom zrnu. Do sada je identificirano preko 50 vrsta mikroorganizama prisutnih u kefirnom zrnu. U radu su prikazane do danas identificirane mikrobne vrste sadržane u kefirnim zrnima različitog podrijetla. Također, radi tehnološkog i mikrobiološkog značenja koja imaju kefirna zrna sama po sebi, u radu su detaljnije prikazani molekularni eksperimentalni pristupi koji se koriste u istraživanju njihove mikrobne bioraznolikosti.
Probiotic bacteria have beneficial effects in prevention and treatment of different diseases. The results of preventive and therapeutic effect of probiotic bacteria on diarrhea during last ten years ...are shown in this paper. The greatest preventive and therapeutic effect of probiotic bacteria was identified for acute diarrhea in children caused by rotaviruses. Significant, but slightly lower effect of probiotic bacteria was proved for antibiotic associated diarrhea. Positive effect in prevention of traveller’s diarrhea and radiation-induced diarrhea is not significant. Preventive and therapeutic effect on diarrhea is not dependent on the way of probiotic bacteria consumption, by fermented milk, capsule or oral rehydration solution.
Mineralni elementi se u mlijeku i mliječnim proizvodima nalaze u obliku anorganskih iona i soli, ili kao dio organskih molekula kao što su bjelančevine, masti, ugljikohidrati i nukleinske kiseline. ...Kemijska forma u kojoj su mineralni elementi prisutni je vrlo važna jer o njoj ovisi apsorpcija u želucu i time njihovo biološko iskorištenje. Mineralni sastav mlijeka nije konstantan i ovisi o stadiju laktacije, hranidbenom statusu životinje, okolišnim uvjetima i genetskim čimbenicima. Cilj ovog rada je prikazati dosadašnje rezultate istraživanja koncentracija, kemijske forme i prehrambene važnosti pojedinih mineralnih elemenata koji su prisutni u različitim vrstama mlijeka i mliječnih proizvoda.
The generally accepted concept of the necessity of producing safe foods has indirectly influenced the decision to replace chemical preservatives
with natural ones. Bacteriocins, and in particular ...those synthesized by
lactic acid bacteria (LAB) in the food industry, are considered to be their effective replacement. In controlling the growth of microbial pathogens and/or the occurrence of pathogenic bacteria in food, with the
permitted nisin and pediocin, a significant antibacterial effect has been shown for most LAB bacteriocins. However, the use of purified bacteriocins as bio preservatives in cheese production is limited. To inhibit the growth of bacteria L. monocytogenes, S. aureus and C. tyrobutyricum in cheese, bacteriocinogenic LAB strains contained in primary, adjunct or protective culture are much more acceptable in cheese production.
Opće prihvaćen koncept o nužnosti proizvodnje zdrave i sigurne hrane neizravno je utjecao na odluku da se i kemijski konzervansi zamijene prirodnim. Bakteriocini, a osobito oni koje sintetiziraju bakterije mliječne kiseline (BMK) u prehrambenoj se industriji smatraju njihovom učinkovitim zamjenom. U kontroli rasta mikrobnih uzročnika kvarenja i/ili pojavnosti patogenih bakterija u hrani, uz dopušteni nizin i pediocin i za većinu je do sada opisanih i pročišćenih bakteriocina BMK utvrđen značajan antibakterijski učinak. Međutim, primjena pročišćenih bakteriocina kao biokonzervansa u proizvodnji sira je limitirana. Za inhibiciju rasta bakterija L. monocytogenes, S. aureus i C. tyrobutyricum u siru, znatno su prihvatljiviji bakteriocinogeni sojevi BMK sadržani u primarnoj, dopunskoj ili protektivnoj kulturi od pročišćenih bakteriocina.
Participation in proficiency testing is not only an obligation for all analytical laboratories which tend to be credible, but also an opportunity to check how the results agree with the reference or ...assign value. The Reference Laboratory for Milk and Dairy Products of the Dairy Science Department, Faculty of Agriculture University of Zagreb, is itself incorporated in the proficiency testing organized by dairy laboratories from Germany, Italy, France, Switzerland and Slovenia. The aim is to find out its own accuracy and reliability in particular milk and dairy products analyses. On the basis of seven years experience of participating in proficiency testing, five years ago the Reference Laboratory started organizing its own proficiency testing for dairy laboratories in Croatia, Bosnia and Herzegovina and Macedonia for milk components such as milk fat, protein, lactose and somatic cells count. The results of the analyses have been statistically analyzed and, on the basis of Z-score, the successful measurements have been estimated. The aim of this paper is to demonstrate the organisation and data processing of proficiency testing for milk fat, protein, lactose and somatic cells count in milk for the involved dairy laboratories.
The aim of this paper was to determine the changes in viscosity of stirred yoghurt from producer A (n = 20) and producer B (n = 20) throughout 21 days of storage. The content of fat, dry matter, ...non-fat dry matter, lactic acid, pH and viscosity of stirred yoghurt were determined on the 0, 7th, 14th and the 21st day of storage of the product at the temperature of 4 °C. Considerable change in viscosity of stirred yoghurt (p < 0,05) throughout the maintenance period was determined on the 0 and the 21st day for both yoghurts. The viscosity of the stirred yoghurt from producer A was increased from 0,324Pa s on the 0 day to 1,912 Pa s on the 21st day. At the same time the viscosity of the stirred yoghurt from producer B was increased from 0,208 Pa s on the 0 day to 0,883 Pa s on the 21st day. In comparison with producer A, a considerably higher quantity of non-fat dry matter and higher quantities of lactic acid (p<0,05) in the stirred yoghurt from producer B resulted in a more stable gel structure throughout the whole research period.
Advances in milk chemistry analytics are in a continuous development for more than one century. Recently, more sophisticated analytical methods became available for a routine performance in the ...laboratory. On the other hand, some of the methods routinely performed in the laboratory became available for the analyses performed at farm level. Overall, the amount and the resolution of data acquired on daily bases today, enables timely monitoring in the dairy production process. Determining the individual components of milk and dairy products in the laboratory can be accomplished using reference methods, or by using routine methods, which are calibrated using the results of the reference methods. Advanced laboratory analysis of milk and dairy products include sophisticated analytical techniques and equipment such as centrifugation, electrophoresis, chromatography, electron microscopy, dynamic light scattering, neutron and X-ray scattering, rheology, mass spectrometry and proteomic approach, all summarized in this review. Additionally, a synopsis of the methods available in laboratory analytical approach of milk components (protein, fat, lactose, minerals and vitamins) and recent on-farm analytical methods using sensor technology is provided.
Molekularne metode za izravnu identifikaciju koriste se u mikrobiologiji hrane desetak godina. Većinom se temelje na amplifikaciji ukupne bakterijske DNA izolirane neposredno iz uzorka, a cilj je ...amplifikacije određeni gen ili varijabilna regija toga gena. Takvi su molekularni pristupi primijenjeni u mnogim studijama identifikacije prirodne populacije bakterija mliječne kisline u mliječnim proizvodima. Također je poznato da autohtona mikrobna populacija bitno pridonosi specifičnostima okusa i mirisa tradicionalnih sireva. Međutim, ne postoji molekularna metoda koja omogućava potpun kvalitativan i kvantitativan uvid u mikrobnu populaciju bilo kojega ekosustava. Zato je potrebno primijeniti kombinirane molekularne pristupe da bi se dobio objektivniji rezultat. Svrha je ovoga rada prikazati najčešće primjenjivane molekularne metode za izravnu identifikaciju bakterija mliječne kiseline u mliječnim proizvodima.
Probiotičke bakterije pozitivno djeluju u prevenciji i terapiji različitih bolesti. U radu su prikazani rezultati istraživanja utjecaja probiotičkih bakterija u prevenciji i terapiji dijareje ...provedenih posljednjih desetak godina. Najveći preventivni i terapijski učinak probiotičkih bakterija utvrđen je za akutnu dijareju u djece uzrokovanu rotavirusima. Značajan, ali nešto manji učinak probiotičkih bakterija dokazan je kod dijareje kao posljedice uzimanja antibiotika. Pozitivan učinak probiotičkih bakterija u prevenciji putničke dijareje i dijareje kao posljedice terapije zračenjem nije značajan. Preventivni i terapijski učinak na dijareju neovisan je o načinu uzimanja probiotičkih bakterija, fermentiranim mlijekom, kapsulom ili oralnom rehidratacijskom otopinom.
The consumption of raw milk from vending machine in Croatia has increased in recent years. However, its health safety is insufficiently investigated and controlled. The objective of this study was to ...investigate the suitability of raw milk consumption, from 28 vending machines from 3 counties in Croatia during one-year research period, based on the physicochemical and hygiene quality. Also, the simulation of psychrothrophic bacteria growth has been conducted in order to determine its optimal storage time because of their unfavorable effect on the milk quality. The physicochemical composition of milk samples (n=320) was determined by the infrared spectrometry (chemical composition) and cryoscopic method (freezing point), while hygiene quality was estimated with a total bacterial count (TBC) and a somatic cell count (SCC). Microbiological analyses included determining the presence of Enterococcus spp., Pseudomonas spp. and the pathogenic species. Satisfactory quality of raw milk was established in 95% (chemical quality) and 70% unadulterated samples (without added water). The prescribed hygiene quality was met by 36.6% (TBC) and 71.9% (SCC) samples. Of total 320 samples, the presence of bacteria in genus Enterococcus spp. and Pseudomonas spp. was confirmed in 93.4% and 96.9% samples, respectively, and bacteria Escherichia coli, Staphylococcus aureus, Lysteria monocytogenes was confirmed in 32.2%, 27.5% and 3.8% samples. The finding of Salmonella spp. and Yersinia enterocolitica was negative. At the end of the study improvement of the microbiological quality of raw milk from vending machines was established. The results indicate the need for systematic control and obligate thermal treatment of raw milk before consumption.
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