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.
In recent years there has been an increasing trend in research of sheep and goat udder morphology, not only from the view of its suitability for machine milking, but also in terms of milk yield and ...mammary gland health. More precisely, herds consisting of high-yielding sheep and goats as a result of long-term and one-sided selection to increase milk yield, have been characterised by distortion of the udder morphology caused by increasing the pressure of udder weight on its suspensory system. Along with the deteriorated milking traits, which is negatively reflected on the udder health, some udder morphology traits are often emphasized as factor of production longevity of dairy sheep and goats. Since the intention of farmers and breeders nowadays is to increase the milk yield of sheep and goats while maintaining desirable udder morphology and udder health, the aim of this paper is to give a detailed overview of the current knowledge about the relationship of morphological udder traits with milk yield, and the health of the mammary gland of sheep and goats. External measures of udder size (circumference, width and depth of the udder) are strongly correlated with milk production in sheep and goats. The morphological udder traits determining its suitability for machine milking (such as teat position and teat angle, udder depth, teat size, cistern height) are related to the mammary gland health in sheep and goats. Thus, the incidence of mastitis is noticeably higher in the udders of unsuitable shape for machine milking (deep and hung udders, unfavourable position of teats, etc.). Consequently, the morphological udder traits that affect the milkability of sheep and goats are indirectly related to milk yield.
The optimal concentration of urea in cow's milk is known and is often used to assess the balance of energy and protein in diets. While in goat (and sheep) milk it is not controled nor defined. Main ...determinants of urea formation in milk are the amount of crude protein intake and the ratio betwwen protein and energy proportion in diet. Goat diet with excessive amount of crude protein and energy unbalanced diet cause the excess of nitrogenous substances in rumen along with release of ammonia and rise in concentration of urea in blood and milk, which adversely affects the production, milk coagulation propreties, environmental pollution and reproductive capabilities of goats. However, besides diet, there are other factors that influence milk urea concentration: breed, stage of lactation, parity, season, body mass, litter size, production and chemical composition of milk. Numerous studies conducted on cow milk included the influence of sources of variability listed above, while there are only few studies available for goat milk due to its less economic importance, seasonal polyesterity and different way of breeding and keeping goats. The aim of this paper is to comparatively and critically combine the previous research results on the importance of determining the milk urea concentration as well as on individual sources of variability of urea concentration in goat milk.
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.
The aim of this work was to evaluate the influence of cheese milk standardization on chemical composition, fat and protein recovery, yield and sensory properties of Croatian soft Protected ...Geographical Indication (PGI) Lički škripavac cheese. Standardization of milk to the casein/fat ratio of 0.7 was carried out by adding skimmed milk powder (SMP) to cheese milk and by skimming part of the milk fat. Results showed that losses of fat by whey were significantly (
< 0.05) lower after Lički škripavac cheese produced from standardized milk by skimming part of the milk fat. Standardization of cheese milk by addition of SMP caused higher losses of protein (
< 0.05) and total solids (
< 0.0001) by whey. Both methods of cheese milk standardization caused a significant (
< 0.01) decrease in milk fat and fat in dry matter content in cheese. In contrast, standardization of cheese milk caused a significant (
< 0.01) increase in protein content in cheese milk. Moisture in non-fat substance (MNFS) significantly (
< 0.05) decreased. Optimization of the casein/fat ratio did not cause a significant increase in fat recovery, but protein recovery significantly increased (
< 0.01). Addition of SMP to cheese milk significantly (
< 0.01) increased actual and adjusted cheese yield. The addition of SMP led to a noticeably higher (
= 0.10) sensory score of Lički škripavac cheese.
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.
Starting from the assumption that the climatic conditions determine the quantity and quality of available forage on the pastures which is the largest source of nutrients of meal of sheep reared in ...coastal and island of Croatia, the aim of this research was to determine the seasonal variations of milk production and quality of Pag and Istrian sheep during three consecutive years – lactations (2012 – 2014) with extremely hot weather conditions. Regular monthly milking controls (using the AT4 method) included 30 flocks of Pag sheep and 19 flocks of Istrian sheep. In total, 29674 daily test records were collected in Pag sheep, and in Istrian sheep 12304 daily test records including the daily milk yield, the chemical composition of milk (content of milk fat, protein, lactose and dry matter) and number of somatic cells in milk. Significant (P<0.001) effect of the year on the daily milk yield of Istrian sheep was found, while unexpectedly, the average daily milk yield of Pag sheep, although predominantly kept in semi-extensive production system, has been uneven between the studied years (P>0.05). Significant variations of the daily milk yield of Pag sheep (P<0.001) and Istrian sheep (P<0.01) due to the season were established, as well as significant (P<0.001) seasonal variations of the content of all analysed milk constituents of Pag and Istrian sheep. Significant (P<0.001) phenotypic correlations were found between the daily milk yield and contents of all analysed components of Pag and Istra sheep milk.
The objective of this study is to describe the diversity of indigenous cultivable community of the lactobacilli associated with the production of traditional Istrian cheese and to get a collection of ...well characterized strains. Raw milk and cheese samples were collected from three different farms in Istria during ripening. A total of 212 mesophilic and thermophilic Lactobacillus isolates as well as bulk colonies (consortia) were investigated using culture-dependent approach combining phenotyping and genotyping. Biochemical fingerprinting with PhenePlate-LB system preliminary grouped 212 isolates in 16 distinct PhP types. Only one representative isolate from each PhP cluster was further analyzed by genotyping for a reliable identification at the genus and species level by employing PCR techniques and sequencing of 16S rRNA genes. Sequence analysis of 16S rRNA revealed the presence of Lactobacillus plantarum, Lactobacillus brevis, Lactobacillus casei, Lactobacillus paracasei and Lactobacillus rhamnosus. Lactobacilli were screened for possible resistance against seven selected antibiotics: ampicillin, tetracycline, penicillin, rifampin, clindamycin, erythromycin and vancomycin. Although there was no clear pattern of antimicrobial susceptibility to most tested antibiotics, all representative isolates were resistant to vancomycin. The analysis of bulk colonies by denaturing gradient gel electrophoresis (DGGE) identified Lactobacillus plantarum and Lactobacillus brevis as predominant members of Lactobacillus population. Pediococcus pentosaceus, Pediococcus acidilactici, Streptococcus sp. and Leuconostoc mesenteroides were also detected as part of the analysed consortia. The prevalence of identified species and community members of lactobacilli agrees with other studies of raw milk cheese and represents a useful base for further selection. Key words: Istrian cheese, lactobacilli, PCR, PCR-DGGE, sequencing
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
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