Mineral elements occur in milk and dairy products as inorganic ions and salts, as well as part of organic molecules, such as proteins, fats, carbohydrates and nucleic acids. The chemical form of ...mineral elements is important because it determines their absorption in the intestine and their biological utilization. The mineral composition of milk is not constant because it depends on lactation phase, nutritional status of the animal, and environmental and genetic factors. The objective of this research is to point out the research results of chemical form, content and nutritional importance of individual mineral elements that are present in various milks and dairy products.
The characteristics of bacterial populations in raw milk at the time of processing has a significant influence on shelf-life, organoleptic quality, spoilage and yields of raw milk, processed milk as ...well as on the other dairy products. Unfortunately, cold and extended storage of raw milk, as a common practice in dairy sector today, favour the growth of psychrotrophic bacteria. Therefore, their count in the refrigerated milk is more than the ideal limit of 10 % of the mesophilic count. Psychrotrophic bacteria are generally able to form extracellular or intracellular thermo-resistant enzymes (proteases, lipases, phospolipases) which can contribute to milk and dairy products spoilage. In addition, besides exhibiting spoilage features, some species belonging to the psychrotrops are considered as emerging pathogens that carry innate resistance to antibiotics or produce toxins. In sense of quality, psychrotrophic bacteria have become major problem for today’s dairy industry as leading cause in spoilage of cold-storage milk and dairy products. This review article focuses on the impact of psychrotrops on quality problems associated with raw milk as well as on th final dairy products. Means of controlling the dominant psychrotrophic species responsible for undesirable activities in milk and dairy products were also discussed.
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.
Kefir grains represent the unique microbial community consisting of bacteria, yeasts, and sometimes filamentous moulds creating complex symbiotic community. The complexity of their physical and ...microbial structures is the reason that the kefir grains are still not unequivocally elucidated. Microbiota of kefir grains has been studied by many microbiological and molecular approaches. The development of metagenomics, based on the identification without cultivation, is opening new possibilities for identification of previously nonisolated and non-identified microbial species from the kefir grains. Considering recent studies, there are over 50 microbial species associated with kefir grains. The aim of this review is to summarise the microbiota composition of kefir grains. Moreover, because of technological and microbiological significance of the kefir grains, the paper provides an insight into the microbiological and molecular methods applied to study microbial biodiversity of kefir grains.
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.
•Non-standard sheep’s milk heat treatment for the production of yogurt was used.•Classical yogurt and probiotic yoghurt were produced.•The yogurts showed high content of nutritionally important whey ...proteins.•Both kinds of yoghurt presented acceptable sensory evaluation.
Classical and probiotic set yogurt were made using non-standard heat treatment of sheep’s milk at 60°C/5min. Physico-chemical properties, sensory characteristics, and the viability of bacteria that originated from cultures in classical and probiotic yogurt were analysed during 21days of storage at 4°C. For the production of yogurt, a standard yogurt culture and a probiotic strain Lactobacillus rhamnosus GG were used. At the end of storage time of the classical and probiotic yogurt the totals of non-denatured whey proteins were 92.31 and 91.03%. The viability of yogurt culture bacteria and Lactobacillus rhamnosus GG were higher than 106cfu/g. The total sensory score (maximum – 20) was 18.49 for the classical and 18.53 for the probiotic. In nutritional and functional terms it is possible to produce classical and probiotic sheep’s milk yogurt by using a non-standard temperature of heat treatment with a shelf life of 21days.
Brač cheese is a traditional Croatian cheese manufactured from the raw sheep milk. The aim of the research was to estimate the contribution of initial salt in moisture content to the composition, ...proteolysis, and texture of Brač cheese during ripening. Higher initial salt in moisture content significantly (P < 0.05) induced higher moisture loss as well as significantly higher (P < 0.05) increase in fat and salt content in Brač cheese. The experimental group of cheeses with higher initial salt in moisture content (1.71–2.10%) had a significantly (P < 0.05) higher amount of intact α s1 -casein and a lower value of WSN %TN and TCA-SN %TN in relation to the other two groups (0.90–1.30% and 1.31–1.70%). In contrast, higher initial salt in moisture content in Brač cheese significantly (P < 0.05) stimulated hydrolysis of β-casein. The texture evaluation showed that the cheeses tended to become significantly (P < 0.05) harder and shorter as initial salt in moisture content increased. The principal component analysis showed primary contribution of moisture and salt in moisture content to the formation of harder and less fracturable cheese during ripening while formation of short textured Brač cheese was a consequence of an increase in the values of secondary proteolysis.
•Salt content alters proteolytic and texture properties of Brač cheese during ripening.•The higher amount of intact αs1-casein was found in cheeses with higher salt content.•The higher salt content stimulates hydrolysis of β-casein during ripening of cheese.•The higher salt content contributes to a harder and less fracturable cheese texture.
Culture-independent molecular tools have been introduced into food microbiology during the last ten years. Most of them are based on the amplification of a bulk bacterial DNA extracted directly from ...a sample, the targeting of a selected gene, or a variable region of the selected gene. Many studies have explored indigenous lactic acid bacteria in dairy products by culture-independent molecular approaches. It is well known that indigenous microbiota significantly contribute to the uniqueness of artisanal cheeses. However, there is no molecular method that can provide complete qualitative and quantitative insight into the microbiota associated with a certain ecosystem. Therefore, a combination of molecular approaches should be applied to get a more objective picture of the microbiota. This paper aims to present the most widely used culture-independent molecular tools for identifying lactic acid bacteria in dairy products. Key words: culture-independent identification, molecular methods, lactic acid bacteria, dairy products
Osobine i svojstva mikrobnih populacija sirovog mlijeka u momentu prerade presudne su za pojavu kvarenja, vrijeme održivosti, organoleptičku kvalitetu i randman mlijeka i mliječnih proizvoda. ...Hlađenje i vremenski duža pohrana sirovog mlijeka na niskim temperaturama, uobičajena u današnjim uvjetima proizvodnje, pogoduje rastu psihrotrofnih bakterija. Zbog toga, broj tih bakterija u ohlađenom sirovom mlijeku u odnosu na broj mezofilnih aerobnih bakterija značajno je viši od njihovog idealnog omjera od 10 %. Većinu psihrotrofnih bakterija karakterizira sposobnost tvorbe ekstracelularnih i/ili intracelularnih termostabilnih enzima (proteaze, lipaze, fosfolipaze) koji mogu uzrokovati kvarenje mlijeka i mliječnih proizvoda. Određene vrste psihrotrofnih bakterija pokazuju i prirodnu otpornost na antibiotike i/ili mogu stvarati toksine te se istovremeno smatraju i uvjetno patogenim bakterijama. U smislu kvalitete sirovog mlijeka i mliječnih proizvoda psihrotrofne bakterije postale su ozbiljan problem s kojim se suočava današnja mljekarska industrija. Svrha ovog preglednog rada bila je opisati negativan utjecaj koji psihrotrofne bakterije imaju na kvalitetu sirovog mlijeka i gotovih mliječnih proizvoda. Također, u radu su opisane najznačajnije vrste, te značenje kontrole kojom se može umanjiti kontaminacija mlijeka i mliječnih proizvoda psihrotrofnim bakterijama.
The aim of this study was to investigate the effect of heat treatment of ovine milk at 60 °C/5 min and 90 °C/5 min (control group) on the compositional and sensory properties of set yoghurt (n = 40). ...The concentration of apparent casein and total whey protein were significantly higher while sensory properties (except consistency) were not significantly different from the yoghurts in control group (P < 0.05). The results showed that ovine set yoghurt produced by heat treatment at low temperature possessed higher amount of preserved inherent functional and nutritional properties of milk than yoghurt produced by heat treatment at high temperature.
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