Influence of frozen storage of goat milk, curd and precheese on brined cheese characteristics

Mleko i proizvodi od mleka malih preživara imaju veliki značaj u ekonomiji određenih zemalja. Bez obzira na značajan porast proizvodnje kozjeg mleka i proizvoda, kravlje mleko je i dalje dominantno na tržištu. Značajan porast proizvodnje kozjeg mleka svakako ukazuje na potrebu da se intenziviraju istraživanja u ovoj oblasti. Dostupnost proizvoda od kozjeg mleka je ograničena u zimskom periodu godine zbog sezonskog karaktera proizvodnje. U praksi su se pojavile razne mogućnosti da se ovo ograničenje prevaziđe. Smrzavanje kozjeg mleka, gruša ili grude je najjednostavniji način da se postigne prisustvo kozjih sireva na tržištu u toku cele godine. Smrzavanje, generalno, može imati negativan uticaj na sve prehrambene proizvode. Tri mehanizma su glavni uzročnici negativnog uticaja: mehanička oštećenja u proizvodu, koja nastaju uvećavanjem kristala leda; denaturacija i agregacija proteina, koja nastaje usled povećanja koncentracije elektrolita tokom smrzavanja; smanjenje sposobnosti reapsorbcije vode nakon odmrzavanja i pojava velike količine izdvojene tečnosti u odmrznutom proizvodu. Ciljevi ove doktorske disertacije su: ispitivanje i analiziranje sezonskih varijacija sastava i svojstava kozjeg mleka u toku različitih perioda laktacije, ispitivanje uticaja smrzavanja kozjeg mleka na reološke parametre sirišne koagulacije i ispitivanje kozjih sireva u salamuri proizvedenih nakon kratkotrajnog (7 dana) i dugotrajnog (60 dana) skladištenja kozjeg mleka, gruša i grude u smrznutom stanju. Navedeni ciljevi su sprovedeni kroz četiri serije ogleda. U prvoj seriji ogleda su ispitivane sezonske varijacije kozjeg mleka tokom četiri laktacije, kao i uticaj klimatskih faktora na fizičko-hemijska svojstva mleka...Milk and milk products of small ruminants have great importance in the economy of certain countries. Regardles of the significant growth of goat milk production, dominant presence of cow milk products is decreasing the competitivity of goat milk products on the market. Significant growth of goat milk production, certainly imply the need for intensive research in that area. Seasonal production of goat milk is the reason why goat product are not available in the winter. In practice there are several possibilities to overcome this limitation. The freezing of goat milk, curd or precheese is the simpliest way, which would make goat milk products available throughout the entire year. Freezing could have negative impact on food products in general. Three mechanisms are the main causes for this negative impact: mechanical breakdown of product structure, caused by large ice crystals; denaturation and aggregation of protein, which happens due to higher concentration of electrolytes durin freezing; lesser water holding capacity after thawing and occurrence of great amount of exudate. The aim of this doctoral dissertation is: to determine the seasonal variation of physicochemical characteristics of goat milk throughout the lactation, to determine the changes in coagulation properties caused by frozen storage of goat milk, as well to determine the possibility to produce the brined cheese from thawed goat milk, curd and precheese, after short-term (7 days) and long-term (60 days) frozen storage. The aim of this research is achived through four sets of experiments. In the first set of experiments, variations of goat milk characteristics throughout the lactation period are examined, as well as the influence of climatic condition parameters on goat milk characteristics..

Effect of pork to beef meat ratio on the physicochemical properties of frankfurters

This study was conducted to investigate the effects of raw material, pork and beef meat, ratio on the physicochemical characteristics of emulsion-type sausage. Five different frankfurter formulations were calculated as follows: B100 (40% beef meat); B75 (30% beef and 10% pork meat); B50 (20% beef and 20% pork meat); B25 (10% beef and 30% pork meat) and B0 (40% pork meat). Frankfurters made solely from beef meat (B100) showed significantly better emulsion stability than those made with pork meat (B0). The increase in the fat content also decreased gel strength, leading to lower values of hardness, cohesiveness, gumminess and chewiness. The optimal ratios between pork and beef meat to enhance the textural properties of frankfurters were B50 and B75. The lightness values (L*) increased with increasing pork meat content, while the redness values (a*) demonstrated the opposite trend. Protein, fat and total pigments displayed a positive relation, whereas water content exhibited a negative relation with a* values

MORPHOLOGICAL CHANGES OF STAPHYLOCOCCUS AUREUS AND SALMONELLA ENTERITIDIS UPON EXPOSURE TO THE EXTRACT OBTAINED FROM PLEUROTUS OSTREATUS MUSHROOM

In last decades, bacterial resistance to first choice antibiotics has been drastically increasing, therefore, the research of new antimicrobial substances is of great importance. This rising problem with bacterial resistance to existing antibiotics affects not only the health care institutes but also food plants. S. aureus and S. enteritidis pose a number of challenges to the food industry and cause foodborne illness in humans. In addition, due to their favourable elemental composition, oyster mushrooms (Pleurotus sp.) are a reservoir of bioactive compounds that give them remarkable antibacterial potential. P. ostreatus is of great economic importance and is the second most cultivated edible mushroom, therefore information about its possible targets on bacterial cells is of great importance for use as a dietary supplement or medicinal purposes. The results of the antibacterial assay showed that tested bacterial strains were susceptible to the methanol extract of P. ostreatus (PoME), while microbicidal activity was only detected against Gram-positive bacteria. Scanning electron microscopy (SEM) micrographs suggested that extract acted on cytoplasmic membrane of S. aureus, while the cell envelope of S. Enteritidis was the most likely target. Natural extracts may outperform individual bioactive compounds due to the synergistic interaction between the metabolites, which can enhance the effects of the individual components. Extracts rich in antibacterials are emerging as alternatives to synthetic antibiotics in the food and health sectors. Among these, crude mushroom extracts are particularly sought after for their diverse bioactive ingredients, as they can combat resistant strains of bacteria due to their different targets and modes of action. PoME can be used as an effective antimicrobial agent, suitable for applications aiming to eradicate foodborne pathogens, thus enhancing food safety.Book of abstract: From biotechnology to human and planetary health XIII congress of microbiologists of Serbia with international participation Mikromed regio 5, ums series 24: 4th – 6th april 2024, Mona Plaza hotel, Belgrade, Serbi

NOVEL BACTERIOPHAGE ISOLATION FROM BELGRADE WASTEWATERS

Anti-microbial drug resistance (AMR) is one of the global health threats caused by the misuse of drugs typically used to treat microbial infections in humans, animals and plants. AMR in nosocomial infections not only significantly hinders treatment and endangers the patients’ lives, but also elevates the costs of healthcare. Multiple research approaches have been initiated to combat AMR, and one promising method is bacteriophage therapy. Bacteriophages (phages) are viruses that naturally exploit bacteria as their hosts for replication and can cause cell lysis, which makes them promising candidates for treating the infections that do not respond to conventional antibiotic therapies. In this study, we screened wastewater samples from four different collectors in Belgrade urban area for bacteriophages active against clinically isolated strains of two biofilm-producing bacteria that readily persist in hospital environment - Klebsiella pneumoniae (6 strains) and Pseudomonas aeruginosa (2 strains). Wastewaters were screened for phage presence through phage enrichment process, in which bacteria were grown in a mixture of water samples and nutrient-rich broth. Obtained cultures were screened for antimicrobial activity against the respective host strains, and candidates were subjected to a first-round plaque assay to detect the phages. Finally, the activity of all the candidates was tested against all strains of the same species to gain the first insight into their host range. We discovered 20 potentially distinct bacteriophages active against K. pneumoniae strains and two potentially different candidates targeting P. aeruginosa. Notably, one phage exhibited activity against all tested K. pneumoniae strains, and four were active against 5 out of 6 tested strains. Among 22 candidates in total, five showed depolymerizing activity, indicating promise in combating biofilm formation. Currently, isolation of new phages, as well as purification and host range analysis is underway for several candidates targeting K. pneumoniae and two targeting P. aeruginosa strains.Book of abstract: From biotechnology to human and planetary health XIII congress of microbiologists of Serbia with international participation Mikromed regio 5, ums series 24: 4th – 6th april 2024, Mona Plaza hotel, Belgrade, Serbi

Uticaj ultrazvučnog tretmana na karakteristike čvrstog jogurta od kozijeg mleka tokom skladištenja

Possibility treatment of ultrasound appliance in the production of goat milk's set yoghurt was investigated. Before inoculation milk was subjected to ultrasound treatment at the frequency of 35 kHz and 200 W powers during 5 and 10 minutes. As control, samples of goat milk's set yoghurt were produced by conventional treatment. Viscosity and physicochemical properties of produced samples were investigated on the 1st, 7th, 14th and 21st day of storage. Based on analysis of the collected data, samples made from goat milk treated by ultrasound during 5 minutes had the highest viscosity, water holding capacity and the least syneresis.U radu je ispitivana mogućnost primene ultrazvučnog tretmana u proizvodnji čvrstog jogurta od kozijeg mleka. Mleko je pre inokulacije starter kulturom tretirano ultrazvukom frekvencije 35 kHz i snage 200 W u trajanju od 5 i 10 minuta. Kao kontrolni proizvedeni su uzorci čvrstog jogurta od kozijeg mleka standardnim tehnološkim postupkom. Ispitivanje viskoziteta i fizičko-hemijskih karakteristika proizvedenih uzoraka jogurta vršeno je 1, 7, 14 i 21- og dana skladištenja. Na osnovu dobijenih rezultata utvrđeno je da su najveće vrednosti viskoziteta, sposobnost vezivanja vode i najmanju sklonost ka sinerezisu, imali uzorci čvrstog jogurta proizvedeni od kozijeg mleka koje je tretirano ultrazvukom u trajanju od 5 minuta

E-commerce readiness and training needs of small-scale dairy processors in Serbia: Understanding barriers and knowledge gaps

The objective of this study was to identify the requirements needed for selling dairy products through e-commerce, as well as current gaps and challenges that exist for small scale dairy processors (SSDPs), and need to be addressed in order to comply with those requirements. A mixed method research design was used for training needs assessment. Qualitative (in-depth interview with 7 online platform representatives (OPRs)) and quantitative approach (survey questionnaire with 58 SSDPs) were conducted. Interview transcripts were coded and codes were grouped into seven themes. Hierarchical cluster analysis was applied to 146 answers from 58 SSDPs. They were divided into 4 clusters. Mean sums of responses between clusters were compared by Mann-Whitney U test. OPRs suggested that SSDPs should be provided with tools and resources to help them achieve food safety and quality targets, as well as practical knowledge and skills. They reported that it is crucial to find a solution for the cold chain transportation, for maintaining consistent product quality. Survey results showed that SSDPs use kitchen equipment (79.3%) and kitchen cleaning products (81.0%) for dairy processing. In total, 43.1% process raw milk and only 24.1% have product label on the package. Only members of cluster 3 and 4 sell their products online (73.7% and 90.0%, respectively), mostly using their own social media platforms (57.9% and 60.0%, respectively), transporting products to end buyers by themselves in hand refrigerators (47.4% and 70.0%, respectively). By analyzing the differences among clusters of SSDPs, trainings can be tailored to the characteristics and knowledge gaps of each group

BACTERIOPHAGES OF MULTIDRUG-RESISTANT NOSOCOMIAL PATHOGENS – BELGRADE EXPERIENCE

Antimicrobial resistance (AMR) arises when bacteria and other microbes stop responding to medications. AMR is now recognized as one of serious global health threats, repeatedly appearing in the World Health Organization’s (WHO) lists of urgent global health challenges, including the 2024 list. It is taking a fatal toll – nearly 5 million deaths globally per year are associated with AMR, encompassing 1.27 million directly attributed to AMR. The COVID-19 pandemic paved the way for aggravation of bacterial AMR – primarily due to enhancement in unspecific and unjustified prescription and use of broad-spectrum antibiotics, resulting in what is now recognized as „silent pandemic of AMR“. Bacteriophages (phages) are natural and specific predators of bacteria - viruses that can infect, replicate inside and lyse arguably any bacteria. Their therapeutic potential is being hastily evaluated through different approaches: in silico, in vitro, ex vivo and in vivo – in laboratory animals as well as in human case and clinical studies. Although the results are promising,bacteria rapidly develop resistance against phages, which why the isolation and research of new phages is needed. Our work is concentrated on three bacterial species for which critical priority by WHO has been declared – carbapenem- resistant Acinetobacter baumannii, Pseudomonas aeruginosa and Klebsiella pneumoniae. Twenty distinct pathogenic strains of A. baumannii, 6 K. pneumoniae and 6 P. aeruginosa were used as targets for bacteriophage isolation, and total of 14, 22 and 8 potentially distinct phages were collected, respectively. All strains were nosocomial isolates obtained from various tissues, including from terminally ill patients. Six phages were characterized in detail. In particular, phage vB_AbaM_ISTD was applied against A. baumannii in zebrafish embryo model of systemic infection, and demonstrated powerful therapeutic potential, eradicating the infection. Interestingly, its DNA was characterized with highly modified thymidine (amassing 1228 Da), making it the largest non-canonical deoxynucleoside reported so far.Book of abstract: From biotechnology to human and planetary health XIII congress of microbiologists of Serbia with international participation Mikromed regio 5, ums series 24: 4th – 6th april 2024, Mona Plaza hotel, Belgrade, Serbi

High Heat Treatment of Goat Cheese Milk. The Effect on Sensory Profile, Consumer Acceptance and Microstructure of Cheese

Goat cheeses from high heat treated milk (HHTM: 80◦C/5 min (E1) and 90◦C/5 min (E2)), could be regarded as new products, compared to their analogues made from commonly pasteurized milk (65◦C/30 min (C)). Descriptive analysis and consumer tests with a hedonic scale and JAR scale were part of the product development process. The use of scanning electron microscopy enabled deeper insight into the flavor and texture of the cheeses. In all cheese variants, goaty flavor was mildly pronounced. Young HHTM cheeses also had a pronounced whey and cooked/milky flavor. Consumers found such flavor ‘too intensive’. Unlike the control variant, HHTM cheeses were not described as ‘too hard’. Such improvement in texture was found to be a result of fine, highly branched microstructure, sustained over the course of ripening time and highly incorporated milk fat globules inside the cheese mass. Cluster analysis showed that the largest group of consumers (47.5%) preferred E2 cheese. Although consumers found that most of the cheeses were ‘too salty’, this excess did not decrease their overall acceptance. Neither microstructure analysis nor descriptive sensory analysis of goat white brined cheeses produced from high heat treated milk has been done before

Rheology and Microstructures of Rennet Gels from Differently Heated Goat Milk

Rennet coagulation of goat milk heated to 65 °C/30 min (Gc), 80 °C/5 min (G8) and 90 °C/5 min (G9) was studied. A rheometer equipped with a vane geometry tool was used to measure milk coagulation parameters and viscoelastic properties of rennet gels. Yield parameters: curd yield, laboratory curd yield and curd yield efficiency were measured and calculated. Scanning electron microscopy of rennet gels was conducted. Storage moduli (G’) of gels at the moment of cutting were 19.9 ± 1.71 Pa (Gc), 11.9 ± 1.96 Pa (G8) and 7.3 ± 1.46 Pa (G9). Aggregation rate and curd firmness decreased with the increase of milk heating temperature, while coagulation time did not change significantly. High heat treatment of goat milk had a significant effect on both laboratory curd yield and curd yield. However, laboratory curd yield (27.7 ± 1.84%) of the G9 treatment was unreasonably high compared to curd yield (15.4 ± 0.60%). The microstructure of G9 was notably different compared to Gc and G8, with a denser and more compact microstructure, smaller paracasein micelles and void spaces in a form of cracks indicating weaker cross links. The findings of this study might serve as the bases for the development of different cheese types produced from high-heat-treated goat milk

Influence of frozen storage of goat milk, curd and precheese on brined cheese characteristics

Mleko i proizvodi od mleka malih preživara imaju veliki značaj u ekonomiji određenih zemalja. Bez obzira na značajan porast proizvodnje kozjeg mleka i proizvoda, kravlje mleko je i dalje dominantno na tržištu. Značajan porast proizvodnje kozjeg mleka svakako ukazuje na potrebu da se intenziviraju istraživanja u ovoj oblasti. Dostupnost proizvoda od kozjeg mleka je ograničena u zimskom periodu godine zbog sezonskog karaktera proizvodnje. U praksi su se pojavile razne mogućnosti da se ovo ograničenje prevaziđe. Smrzavanje kozjeg mleka, gruša ili grude je najjednostavniji način da se postigne prisustvo kozjih sireva na tržištu u toku cele godine. Smrzavanje, generalno, može imati negativan uticaj na sve prehrambene proizvode. Tri mehanizma su glavni uzročnici negativnog uticaja: mehanička oštećenja u proizvodu, koja nastaju uvećavanjem kristala leda; denaturacija i agregacija proteina, koja nastaje usled povećanja koncentracije elektrolita tokom smrzavanja; smanjenje sposobnosti reapsorbcije vode nakon odmrzavanja i pojava velike količine izdvojene tečnosti u odmrznutom proizvodu. Ciljevi ove doktorske disertacije su: ispitivanje i analiziranje sezonskih varijacija sastava i svojstava kozjeg mleka u toku različitih perioda laktacije, ispitivanje uticaja smrzavanja kozjeg mleka na reološke parametre sirišne koagulacije i ispitivanje kozjih sireva u salamuri proizvedenih nakon kratkotrajnog (7 dana) i dugotrajnog (60 dana) skladištenja kozjeg mleka, gruša i grude u smrznutom stanju. Navedeni ciljevi su sprovedeni kroz četiri serije ogleda. U prvoj seriji ogleda su ispitivane sezonske varijacije kozjeg mleka tokom četiri laktacije, kao i uticaj klimatskih faktora na fizičko-hemijska svojstva mleka...Milk and milk products of small ruminants have great importance in the economy of certain countries. Regardles of the significant growth of goat milk production, dominant presence of cow milk products is decreasing the competitivity of goat milk products on the market. Significant growth of goat milk production, certainly imply the need for intensive research in that area. Seasonal production of goat milk is the reason why goat product are not available in the winter. In practice there are several possibilities to overcome this limitation. The freezing of goat milk, curd or precheese is the simpliest way, which would make goat milk products available throughout the entire year. Freezing could have negative impact on food products in general. Three mechanisms are the main causes for this negative impact: mechanical breakdown of product structure, caused by large ice crystals; denaturation and aggregation of protein, which happens due to higher concentration of electrolytes durin freezing; lesser water holding capacity after thawing and occurrence of great amount of exudate. The aim of this doctoral dissertation is: to determine the seasonal variation of physicochemical characteristics of goat milk throughout the lactation, to determine the changes in coagulation properties caused by frozen storage of goat milk, as well to determine the possibility to produce the brined cheese from thawed goat milk, curd and precheese, after short-term (7 days) and long-term (60 days) frozen storage. The aim of this research is achived through four sets of experiments. In the first set of experiments, variations of goat milk characteristics throughout the lactation period are examined, as well as the influence of climatic condition parameters on goat milk characteristics..