Influence of microfiltration and adjunct culture on quality of Domiati cheese

The effects of microfiltration and pasteurization processes on proteolysis, lipolysis, and flavor development in Domiati cheese during 2 mo of pickling were studied. Cultures of starter lactic acid bacteria isolated from Egyptian dairy products were evaluated in experimental Domiati cheese for flavor development capabilities. In the first trial, raw skim milk was microfiltered and then the protein:fat ratio was standardized using pasteurized cream. Pasteurized milk with same protein:fat ratio was also used in the second trial. The chemical composition of cheeses seemed to be affected by milk treatment—microfiltration or pasteurization—rather than by the culture types. The moisture content was higher and the pH was lower in pasteurized milk cheeses than in microfiltered milk cheeses at d 1 of manufacture. Chemical composition of experimental cheeses was within the legal limits for Domiati cheese in Egypt. Proteolysis and lipolysis during cheese pickling were lower in microfiltered milk cheeses compared with pasteurized milk cheeses. Highly significant variations in free amino acids, free fatty acids, and sensory evaluation were found among the cultures used in Domiati cheesemaking. The cheese made using adjunct culture containing Lactobacillus delbrueckii ssp. lactis, Lactobacillus paracasei ssp. paracasei, Lactobacillus casei, Lactobacillus plantarum, and Enterococcus faecium received high scores in flavor acceptability. Cheeses made from microfiltered milk received a higher score in body and texture compared with cheeses made from pasteurized milk.     

Sensory quality of dairy products fortified with fish oil

Our objective was to evaluate the influence of fish oil fortification on the sensory quality of selected dairy products. Yoghurts, fresh, soft and processed cheeses, butter and cream were fortified at different levels. Sensory quality was evaluated using a scaling method and the threshold values of the fortification levels were established. Fortification of dairy products with long-chain polyunsaturated fatty acid (PUFA) omega-3 by fish oil addition appeared possible; however, the level of fortification was limited. The highest level of fortification was obtained for solid, high-fat dairy products (spreadable fresh cheese, butter and processed cheeses), especially when flavourings were present. Such dairy products maintained a constant sensory quality during 4 weeks of storage. One portion of butter, processed and spreadable fresh cheeses fortified at levels established in the study, might provide 180–360 mg of long-chain omega-3 PUFA, significantly elevating their average level in the diet.     

The occurrence and growth of yeasts in dairy products

Yeasts were isolated, identified and enumerated from 161 samples of retail dairy products. Highest yeast populations (up to 10⁶–10⁷ cells/g) were found in yogurt and cheese samples while lower counts occurred in samples of pasteurized milk, cream, butter and ice cream. Candida famata, Kluyveromyces marxianus, Candida diffluens and Rhodotorula glutinis were the most frequency isolated species. The growth of these and other species was demonstrated during the refrigerated storage of cream, butter and cheese samples and by their inoculation and incubation in milk and yogurt samples. The predominance and growth species was probably related to their production of protein and fat hydrolysing enzymes and the ability to grow at 5°C.     

Raw milk and raw milk cheeses as vehicles for infection by Verocytotoxin-producing Escherichia coli

Raw milk and raw milk cheeses can be a source of food-borne pathogens, including Verocytotoxin (Shiga toxin)-producing Escherichia coli (VTEC/STEC). Outbreaks of VTEC O157: H7 infections have been attributed to the consumption of raw milk and associated dairy products. Although the general prevalence of VTEC O157 in raw milk and raw milk cheeses is low, it can be higher for non-O157 VTEC. The clinical significance of many of these VTEC is unclear, although some are associated with disease. Studies show that E. coli O157 strains can survive the various stages of the cheesemaking process and that raw milk and raw milk cheeses remain a potential vehicle for VTEC infections.     

Effect of buttermilk made from creams with different heat treatment histories on properties of rennet gels and model cheeses

Although many studies have reported negative effects on cheese properties resulting from the use of buttermilk in cheese milk, the cause of these effects has not been determined. In this study, buttermilk was manufactured from raw cream and pasteurized cream, as well as from a cream derived from pasteurized whole milk. Skim milks with the same heat treatments were also manufactured to be used as controls. Compositional analysis of the buttermilks revealed a pH 4.6-insoluble protein content approximately 10% lower than that of the skim milk counterparts. Milk fat globule membrane (MFGM) proteins remained soluble at pH 4.6 in raw cream buttermilk; however, when heat was applied to cream or whole milk before butter making, MFGM proteins precipitated with the caseins. Rennet gel characterization showed that MFGM material in the buttermilks decreased the firmness and increased the set-to-cut time of rennet gels, but this effect was amplified when pasteurized cream buttermilk was added to cheese milk. The microstructure of gels was studied, and it was observed that gel appearance was very different when pasteurized cream buttermilk was used, as opposed to raw cream buttermilk. Model cheeses manufactured with buttermilks tended to have a higher moisture content than cheeses made with skim milks, explaining the higher yields obtained with buttermilk. Superior retention of MFGM particles was observed in model cheeses made from pasteurized cream buttermilk compared with raw cream buttermilk. The results from this study show that pasteurization of cream and of whole milk modifies the surface of MFGM particles, and this may explain why buttermilk has poor coagulation properties and therefore yields rennet gels with texture defects.     

A new magnetic resonance imaging approach for discriminating Sardinian sheep milk cheese made from heat-treated or raw milk

The evaluation of milk heat treatment on dairy products via reliable analytical methods is a challenging issue that involves both industrial and fundamental research. We describe a new magnetic resonance imaging (MRI) protocol for discriminating Sardinian sheep milk cheese originating from heat-treated or raw milk. Thirty-six samples (18 pecorino cheeses manufactured from heat-treated milk and 18 Fiore Sardo cheeses made from raw milk) were investigated by means of MRI and bi-exponential signal decay analysis. The protocol is capable of discerning cheeses by virtue of the different distribution of the transversal (T₂) relaxation time constant. Cheeses from heat-treated milk showed a significantly higher area fraction (≈70–80%), corresponding to the fast relaxing water protons (T₂ ≈ 9 ms), compared with raw milk cheeses, whereas the opposite was observed for the long T₂ (T₂ ≈ 35 ms) proton population. The MRI protocol described is rapid and nondestructive, and it provides statistically significant discrimination between ewe milk cheeses made from heat-treated and raw milk.     

Tetracycline antibiotics transfer from contaminated milk to dairy products and the effect of the skimming step and pasteurisation process on residue concentrations

The presence of antibiotics in raw milk and milk derivatives poses a threat to human health and can negatively affect the dairy industry. Therefore, the main object of this study was to investigate the transfer of oxytetracycline (OTC), tetracycline (TC), chlortetracycline (CTC) and doxycycline (DC) from raw, experimental milk contaminated with tetracyclines (TCs) to different dairy products: cream, butter, buttermilk, sour milk, whey, curd and cheese. Additionally the effect of the skimming process on TCs concentrations was tested, as well as the influence of low-temperature long-time pasteurisation. The analyses of TCs in milk and dairy products were performed by an LC-MS/MS method. In order to determine TCs residues in dairy products, an analytical method was developed with the same extraction step for all matrices. TCs molecules were inhomogenously distributed between the milk derivative fractions. The highest concentrations were determined in curd and cheese in the ranges 320–482 µg/kg and 280–561 µg/kg, respectively. Low levels of TCs in butter and whey were observed (11.8–41.2 µg/kg). TCs were found in sour milk (66.0–111 µg/kg), cream (85.0–115 µg/kg) and buttermilk (196–221 µg/kg) at much higher levels than in butter and whey, but lower than in curd and cheese. During the skimming process, the highest yield of cream was obtained after the raw milk was held at 2–8°C for 24 h. The differences in concentrations of TCs between whole milk and skimmed milk, expressed as percentages of recovery, were below 19% (recoveries in excess of 81%). The highest content was observed in milk and cream skimmed at 2–8°C. The degradation percentages for TCs during the pasteurisation process (63°C for 30 min) were below 19%.     

Probiotic potential and biochemical and technological properties of Lactococcus lactis ssp. lactis strains isolated from raw milk and kefir grains

Lactococcus lactis ssp. lactis is one of the most important starter bacteria used in dairy technology and it is of great economic importance because of its use in the production of dairy products, including cheese, butter, cream, and fermented milks. Numerous studies have evaluated the biochemical and probiotic properties of lactococci; however, limited studies on the probiotic characteristics of lactococci were conducted using strains originating from raw milk and dairy products. Characterizing the probiotic properties of strains isolated from raw milk and fermented milk products is important in terms of selecting starter culture strains for the production of functional dairy products. In this study, biochemical properties (including antibiotic sensitivity, lipolytic activity, amino acid decarboxylation, antioxidant activity) and probiotic properties (including antimicrobial activity, growth in the presence of bile salts, bile salts deconjugation, and hydrophobicity) of 14 Lactococcus lactis strains isolated from raw milk and kefir grains were investigated. Strains originating from kefir grains had better characteristics in terms of antimicrobial activity and bile salt deconjugation, whereas strains from raw milk had better hydrophobicity and antioxidant activity characteristics. None of the strains were able to grow in the presence of bile salt and did not show amino acid decarboxylation or lipolytic activities. Biochemical and probiotic properties of L. lactis strains varied depending on the strain and some of these strains could be used as functional cultures depending on their properties. However, these strains did not possess all of the properties required to meet the definition of a probiotic.     

Prevalence and diversity of histamine-forming Lactobacillus parabuchneri strains in raw milk and cheese – A case study

In the present case study, we investigated the causes of consistently elevated histamine content in raw milk cheeses from a Swiss cheese dairy. Screenings of milk samples from 67 farmers revealed that 19.1% of the raw milk samples were contaminated with histamine-forming bacteria. Lactobacillus parabuchneri was detected in 97.4% of contaminated milk samples. The population density of L. parabuchneri was almost always below the limit of quantification of the qPCR method used. Genotyping of 469 isolates provided detailed insight into the diversity of L. parabuchneri in contaminated milks and cheeses. The results of the trace-back study clearly demonstrated that several milk suppliers were responsible for the histamine problem at the cheese dairy under study. Systematic controls of milking systems allowed persistent contamination sources of L. parabuchneri at the farm level to be identified and eliminated and thereby to reduce the percentage of contaminated milks to 8.5% within the study period.     

High Pressure Treatment of Milk and Effects on Microbiological and Sensory Quality of Cheddar Cheese

The effect of cycled high pressure treatment of milk on the yield, sensory, and microbiological quality of Cheddar cheese was investigated. Cheddar cheeses were made from pasteurized, raw, or pressure treated milk according to traditional methods. Flavor scores from trained dairy judges were not different for pasteurized and pressurized milk cheeses (P≤0.05). Percent moisture and wet weight yields of pressure treated milk cheeses were higher than pasteurized or raw milk cheeses (P≤0.05). Microbiological quality of pressurized milk cheeses was comparable to pasteurized milk cheeses. Texture defects were present in pressurized milk cheeses and were attributed to excess moisture. High pressure treatment of milk shows promise as an alternative to heat pasteurization prior to cheesemaking.     

Microbiota characterization of a Belgian protected designation of origin cheese,Herve cheese,using metagenomic analysis

Herve cheese is a Belgian soft cheese with a washed rind, and is made from raw or pasteurized milk. The specific microbiota of this cheese has never previously been fully explored and the use of raw or pasteurized milk in addition to starters is assumed to affect the microbiota of the rind and the heart. The aim of the study was to analyze the bacterial microbiota of Herve cheese using classical microbiology and a metagenomic approach based on 16S ribosomal DNA pyrosequencing. Using classical microbiology, the total counts of bacteria were comparable for the 11 samples of tested raw and pasteurized milk cheeses, reaching almost 8 log cfu/g. Using the metagenomic approach, 207 different phylotypes were identified. The rind of both the raw and pasteurized milk cheeses was found to be highly diversified. However, 96.3 and 97.9% of the total microbiota of the raw milk and pasteurized cheese rind, respectively, were composed of species present in both types of cheese, such as Corynebacterium casei, Psychrobacter spp., Lactococcus lactis ssp. cremoris, Staphylococcus equorum, Vagococcus salmoninarum, and other species present at levels below 5%. Brevibacterium linens were present at low levels (0.5 and 1.6%, respectively) on the rind of both the raw and the pasteurized milk cheeses, even though this bacterium had been inoculated during the manufacturing process. Interestingly, Psychroflexus casei, also described as giving a red smear to Raclette-type cheese, was identified in small proportions in the composition of the rind of both the raw and pasteurized milk cheeses (0.17 and 0.5%, respectively). In the heart of the cheeses, the common species of bacteria reached more than 99%. The main species identified were Lactococcus lactis ssp. cremoris, Psychrobacter spp., and Staphylococcus equorum ssp. equorum. Interestingly, 93 phylotypes were present only in the raw milk cheeses and 29 only in the pasteurized milk cheeses, showing the high diversity of the microbiota. Corynebacterium casei and Enterococcus faecalis were more prevalent in the raw milk cheeses, whereas Psychrobacter celer was present in the pasteurized milk cheeses. However, this specific microbiota represented a low proportion of the cheese microbiota. This study demonstrated that Herve cheese microbiota is rich and that pasteurized milk cheeses are microbiologically very close to raw milk cheeses, probably due to the similar manufacturing process. The characterization of the microbiota of this particular protected designation of origin cheese was useful in enabling us to gain a better knowledge of the bacteria responsible for the character of this cheese.     

Verocytotoxin-producing Escherichia coli O157 in minced beef and dairy products in Italy

A total of 3879 samples of foodstuffs were examined for the presence of Verocytotoxin-producing Escherichia coli O157 (VTEC O157). The survey was conducted by 9 of the 10 Italian Veterinary Public Health Laboratories. Samples were collected between May 2000 and September 2001 in 14 regions and comprised 931 minced beef specimens and 2948 dairy products (DP) with less than 60 days of ripening. The DP included 657 pasteurised and 811 unpasteurised bovine DP, 477 pasteurised and 502 unpasteurised ovine DP, and 501 water-buffalo's milk mozzarella cheese. Samples were collected at retail level, from plants processing minced beef and dairy plants and from farms directly manufacturing cheeses. All the samples were tested using a sensitive procedure based on ISO/DIS 16654:1999 (later ISO 16654:2001), which includes an immunomagnetic separation step. A preliminary inter-laboratory trial was organised with artificially contaminated samples to assess the ability of all the participating laboratories to isolate E. coli O157 by the established procedure. VTEC O157 was isolated from four (0.43%) of the minced beef samples, collected in four different regions and during different months, but was not detected in any of the dairy products. E. coli O157 VT-eae+ was isolated from one raw cow's milk cheese. This survey provided national data on the presence of VTEC O157 in foodstuffs, demonstrating a low prevalence of the organism. The survey also encouraged updating of knowledge and procedures on VTEC O157 in laboratories with official responsibility for microbiological testing of foods of animal origin.     

Overview of Food Safety Hazards in the European Dairy Supply Chain

Monitoring of dairy products should preferably focus on the most relevant food safety hazards in the dairy supply chain. For this purpose, the possible presence of microbiological, chemical, and physical hazards as well as trends in the dairy supply chain that may affect their presence were assessed. A literature review was combined with available data from EFSA, RASFF, and the Dutch monitoring program on chemical hazards as well as expert information. This study revealed that microbiological hazards are encountered more frequently in dairy products than chemical and physical hazards. Listeria monocytogenes, Staphylococcus aureus, Salmonella, and human pathogenic Escherichia coli were identified as the most important microbiological hazards in dairy products. Soft and semisoft cheeses are most frequently associated with L. monocytogenes and S. aureus enterotoxins, whereas raw milk is most frequently associated with human pathogenic E. coli and Campylobacter spp., Cronobacter spp., and Salmonella spp. are the microbiological hazards of most concern in powdered infant formula. Based on literature, monitoring, and RASFF data, the most relevant chemical hazards in dairy products are aflatoxin M₁, dioxins, and dioxin‐like compounds and residues of veterinary drugs. Chemical hazards primarily occur at the dairy farm and may accumulate during further processing. The most relevant physical hazards are metal, glass, and plastic particles introduced during processing. Analysis of trends in the near future revealed that increased milk production is seen as most relevant in relation to food safety. Other trends affecting food safety are climate change and changes at the farm level, which aim to improve animal welfare and environmental sustainability.     

Chemical, physical, and sensory properties of dairy products enriched with conjugated linoleic acid

Recent studies have illustrated the effects of cis-9,trans-11 conjugated linoleic acid (CLA) on human health. Ruminant-derived meat, milk and dairy products are the predominant sources of cis-9,trans-11 CLA in the human diet. This study evaluated the processing properties, texture, storage characteristics, and organoleptic properties of UHT milk, Caerphilly cheese, and butter produced from a milk enriched to a level of cis-9,trans-11 CLA that has been shown to have biological effects in humans. Forty-nine early-lactation Holstein-British Friesian cows were fed total mixed rations containing 0 (control) or 45 g/kg (on dry matter basis) of a mixture (1:2 wt/wt) of fish oil and sunflower oil during two consecutive 7-d periods to produce a control and CLA-enhanced milk, respectively. Milk produced from cows fed the control and fish and sunflower oil diets contained 0.54 and 4.68 g of total CLA/100 g of fatty acids, respectively. Enrichment of CLA in raw milk from the fish and sunflower oil diet was also accompanied by substantial increases in trans C18:1 levels, lowered C18:0, cis-C18:1, and total saturated fatty acid concentrations, and small increases in n-3 polyunsatu-rated fatty acid content. The CLA-enriched milk was used for the manufacture of UHT milk, butter, and cheese. Both the CLA-enhanced butter and cheese were less firm than control products. Although the sensory profiles of the CLA-enriched milk, butter, and cheese differed from those of the control products with respect to some attributes, the overall impression and flavor did not differ. In conclusion, it is feasible to produce CLA-enriched dairy products with acceptable storage and sensory characteristics.     

Ripening of Cheddar cheese made from blends of raw and pasteurised milk

Cheddar cheeses were made from pasteurised milk (P), raw milk (R) or pasteurised milk to which 10 (PR10), 5 (PR5) or 1 (PR1) % of raw milk had been added. Non-starter lactic acid bacteria (NSLAB) were not detectable in P cheese in the first month of ripening, at which stage PR1, PR5, PR10 and R cheeses had 10⁴, 10⁵, 10⁶ and 10⁷ cfu NSLAB g⁻¹, respectively. After ripening for 4 months, the number of NSLAB was 1–2 log cycles lower in P cheese than in all other cheeses. Urea–polyacrylamide gel electrophoretograms of water-soluble and insoluble fractions of cheeses and reverse-phase HPLC chromatograms of 70% (v/v) ethanol-soluble as well as -insoluble fractions of WSF were essentially similar in all cheeses. The concentration of amino acids were pro rata the number of NSLAB and were the highest in R cheese and the lowest in P cheese throughout ripening. Free fatty acids and most of the fatty acid esters in 4-month old cheeses were higher in PR1, PR5, PR10 and R cheeses than in P cheese. Commercial graders awarded the highest flavour scores to 4-month-old PR1 cheeses and the lowest to P or R cheese. An expert panel of sensory assessors awarded increasingly higher scores for fruity/sweet and pungent aroma as the level of raw milk increased. The trend for aroma intensity and perceived maturity was R>PR10>PP5>PR1>P. The NSLAB from raw milk appeared to influence the ripening and quality of Cheddar cheese.     

Selection, application and monitoring of Lactobacillus paracasei strains as adjunct cultures in the production of Gouda-type cheeses

Raw milk cheeses have more intense flavours than cheeses made from pasteurized milk and harbour strains with potential adjunct properties. Two Lactobacillus paracasei strains, R-40926 and R-40937, were selected as potential adjunct cultures from a total of 734 isolates from good quality artisan raw milk Gouda-type cheeses on the basis of their prevalence in different cheese types and/or over several production batches, safety and technological parameters. Conventional culturing, isolation and identification and a combined PCR-DGGE approach using total cheese DNA extracts and DNA extracts obtained from culturable fractions were employed to monitor viability of the introduced adjuncts and their effect on the cheese microbiota. The control cheese made without adjuncts was dominated by members of the starter, i.e. Lactococcus lactis and Leuconostoc pseudomesenteroides. In the cheeses containing either R-40926 or R-40937, the respective adjuncts increased in number as ripening progressed indicating that both strains are well adapted to the cheese environment and can survive in a competitive environment in the presence of a commercial starter culture. Principal component analysis of cheese volatiles determined by steam distillation-extraction and gas chromatography-mass spectrometry could differentiate cheeses made with different concentrations of adjunct R-40926 from the control cheese, and these differences could be correlated to the proteolytic and lipolytic properties of this strain. Collectively, results from microbiological and metabolic analyses indicate that the screening procedure followed throughout this study was successful in delivering potential adjunct candidates to enrich or extend the flavour palette of artisan Gouda-type cheeses under more controlled conditions.     

Utilization of microfiltration or lactoperoxidase system or both for manufacture of Cheddar cheese from raw milk

The objective of the present study was to determine if application of microfiltration (MF) or raw milk lactoperoxidase system (LP) could reduce the risk of foodborne illness from Escherichia coli in raw milk cheeses, without adversely affecting the overall sensory acceptability of the cheeses. Escherichia coli K12 was added to raw milk to study its survival as a non-pathogenic surrogate organism for pathogenic E. coli. Five replications of 6 treatments of Cheddar cheese were manufactured. The 6 treatments included cheeses made from pasteurized milk (PM), raw milk (RM), raw milk inoculated with E. coli K12 (RME), raw milk inoculated with E. coli K12 + LP activation (RMELP), raw milk inoculated with E. coli K12 + MF (MFE), and raw milk inoculated with E. coli K12 + MF + LP activation (MFELP). The population of E. coli K12 was enumerated in the cheese milks, in whey/curds during cheese manufacture, and in final Cheddar cheeses during ripening. Application of LP, MF, and a combination of MF and LP led to an average percentage reduction of E. coli K12 counts in cheese milk by 72, 88, and 96%, respectively. However, E. coli K12 populations significantly increased during the manufacture of Cheddar cheese for the reasons not related to contamination. The number of E. coli K12, however, decreased by 1.5 to 2 log cycles during 120 d of ripening, irrespective of the treatments. The results suggest that MF with or without LP significantly lowers E. coli count in raw milk. Hence, if reactivation of E. coli during cheese making could be prevented, MF with or without LP would be an effective technique for reducing the counts of E. coli in raw milk cheeses. The cheeses were also analyzed for proteolysis, starter and nonstarter lactic acid bacteria (NSLAB), and sensory characteristics during ripening. The concentration of pH 4.6 soluble nitrogen at 120 d was greater in PM cheese compared with the other treatments. The level of 12% trichloroacetic acid-soluble nitrogen at 120 d was greater in RM, RME, and RMELP cheeses compared with PM, MFE, and MFELP cheeses. This could be related to the fact that cheeses made from raw milk with or without LP (RM, RME, and RMELP) had greater levels of NSLAB compared with PM, MFE, and MFELP cheeses. Cheeses at 60 d, as evaluated by 8 trained panelists, did not differ in bitterness, pastiness, or curdiness attributes. Cheeses at 120 d showed no differences in acid-taste, bitterness, or curdiness attributes. Sensory analysis at 60 d showed that PM and MFELP cheeses had greater overall sensory acceptability than RM and RME cheeses. The overall sensory acceptability of the cheeses at 120 d showed that PM, MFE, and MFELP cheeses were more acceptable than RM and RME cheeses.     

Occurrence of foodborne pathogens and characterization of Staphylococcus aureus in cheese produced on farm-dairies

The objective of this study was to address knowledge gaps identified in an earlier risk assessment of Staphylococcus aureus and raw milk cheese. A survey of fresh and short-time ripened cheeses produced on farm-dairies in Sweden was conducted to investigate the occurrence and levels of S. aureus, Listeria monocytogenes and Escherichia coli, to characterize S. aureus isolates with special emphasis on enterotoxin genes, antibiotic resistance, bio-typing and genetic variation, and to collect information related to production practices. In general, the hygienic quality of farm-dairy cheeses appeared to be of an acceptable microbiological quality, e.g. L. monocytogenes and staphylococcal enterotoxin were not detected in cheese samples. However, E. coli and enterotoxigenic S. aureus were frequently found in raw milk cheeses and sometimes at levels that are of concern, especially in fresh cheese. Interestingly, levels in raw milk fresh cheese were significantly lower when starter cultures were used. Up to five S. aureus colonies per cheese, if possible, were characterized and about 70% of isolates carried one or more enterotoxin genes, most common were sec and sea. The Ovine biotype (73%) was most common among isolates from goat milk cheese and the Human biotype (60%) from cow milk cheese. Of all isolates, 39% showed decreased susceptibility to penicillin, but the proportion of isolates from cows' cheese (66%) compared to isolates from goats' cheese (27%) was significantly higher. S. aureus isolates with different properties were detected in cheese from the same farm and, sometimes even the same cheese. Isolates with the same pulsed-field gel electrophoresis (PFGE)-pattern were detected on geographically distant dairies. This indicates that multiple sources and routes of contamination are important. To improve the safety of these products efforts to raise awareness of the importance of hygiene barriers and raw milk quality as well as improved process control can be suggested, e.g. use of starter cultures and monitoring of fermentation with a pH-meter. For future safety assessments, a better understanding of factors determining toxin production in these cheeses is needed.     

Effect of milk thermisation and farming system on cheese sensory profile and fatty acid composition

The effect of milk thermisation and farming system on the sensory profile and fatty acid (FA) composition of a traditional cheese under real production conditions was evaluated. Raschera Protected Designation of Origin (PDO) cheese, which is produced in North-West Italy, was chosen as a case study. Cheese samples were collected in summer and winter from dairy plants that processed raw milk (IR) or thermised milk (IT) collected from intensive farms, or raw milk (ER) collected from extensive farms. The sensory profile and FA composition of IR and IT cheese were similar. The ER summer cheeses had a lower cream odour, butter odour and aroma. They had a higher rennet, strong toasted, silage, barn, garlic, boiled vegetables, and smoked odours and aromas, a higher hazelnut odour, and tasted more bitter. The ER summer cheese also expressed a more favourable FA composition for human health, which allowed it to be distinguished among the other Raschera cheese.     

Correlation between multielement stable isotope ratio and geographical origin in Peretta cows' milk cheese

The aim of this study was to characterize the isotopic composition and protect “Peretta” cows’ milk cheese, a typical product of Sardinia, against other cheeses of the same appearance sold under the same name, but made of raw materials from northern Europe. The study was concerned with 3 types of cheese: those produced in local dairies from milk from free-grazing or pasture-grazing cows in Sardinia (local dairy product), cheeses made on an industrial scale from milk produced by intensive farming in Sardinia (factory cheese), and cheeses made with raw materials imported from other countries (imported product). To distinguish the Sardinian cheeses from the imported product, the stable isotope ratios ¹³C/¹²C, ¹⁵N/¹⁴N, D/H, ³⁴S/³²S, and ¹⁸O/¹⁶O were used. Determination of the isotopic data δ¹³C, δ¹⁵N, δ²H, and δ³⁴S was performed in the casein fraction, whereas δ¹⁸O and δ¹³C were determined in the glycerol fraction. Measurements were performed by isotope ratio mass spectrometry. A comparison between mean values of the isotope ratios by statistical analysis (ANOVA and Tukey's test) showed that the greatest difference between the 3 types of cheese (local dairy, factory, and imported products) was in the ¹³C/¹²C, ³⁴S/³²S, and ¹⁸O/¹⁶O isotope ratios. In the other parameters, either no differences (δ¹⁵N) or minimal differences (δ²H) were found. Evaluation of the data by multivariate statistical analysis (principal component analysis and hierarchical cluster analysis) revealed that the isotope characteristics of the factory products were similar to those of the cheeses produced from imported raw materials, whereas a difference was found between the local dairy-produced cheeses and the products in the other 2 categories.