Textural and microstructural properties of urfa cheese (a white-brined Turkish cheese)

The texture and microstructure of white-brined cheeses similar to urfa (a traditional Turkish cheese) were studied. One batch of cheeses was made in the traditional manner and one batch was made from ultrafiltered (UF) milk. Samples from each batch were either ripened in brine after production or scalded in whey for 3 min at 90°C prior to ripening. The results showed only marginal differences in the ripening profiles of both batches of unscalded cheeses, but scalding slowed down the extent of proteolysis in both batches. The scalded cheeses had a firmer texture than the unscalded ones, and the unscalded UF cheese had a more 'springy' body than the unscalded traditional cheese. Overall, scalding resulted in a more homogeneous structure, but the unscalded UF cheese had a close texture that resembled the scalded samples. It was concluded that, with respect to texture and structure, cheeses made with UF milk do not need to be scalded after production.     

Some properties of urfa cheese (a traditional white-brined Turkish cheese) produced from bovine and ovine milks

In this study, the basic composition and ripening profile of traditional urfa cheese made from ovine and bovine milks were investigated. While cheese made from ovine milk had higher total solids, fat-in-dry matter and total nitrogen, the titratable acidity, salt-in-dry matter, pH, total mesophilic colony count and total yeasts and moulds counts were found to be close to each other. During storage, whilst the total solids content of cheese produced from ovine milk gradually decreased, the variation in the total solids content of cheese made from bovine milk was found to be insignificant. The salt penetration into the cheeses was rapid during the first two weeks of ripening, and it continued to diffuse into the samples throughout storage. Proteolysis developed faster in the cheese made from ovine milk than in cheese of bovine milk. The former sample had higher water soluble nitrogen, nonprotein nitrogen, phosphotungustic acid soluble nitrogen, Proteose-peptone nitrogen and tyrosine levels throughout storage, and the ripening index was higher as well.     

Characterization of Italian cheeses ripened under nonconventional conditions

Four Italian cheeses (Casciotta di Urbino, Barricato San Martino, Vento d’Estate, and Ubriaco di Raboso) nonconventionally ripened under different plant materials (walnut leaves, herbs, hay, and wine by-products, respectively) were compared for compositional, microbiological, biochemical, and volatile profile characteristics. Mean values for gross composition were rather similar. Because primary starters were not used for manufacture, the endogenous lactic acid bacteria were mainly present (7.0 to 9.0 log₁₀ cfu/g). Except for Lactobacillus paracasei and Leuconostoc mesenteroides, which were commonly identified in 3 cheeses, Lactococcus lactis, Enterococcus sanguinicola, Lactobacillus brevis, Enterococcus durans/Enterococcus faecium, Lactobacillus plantarum, and Weissella cibaria/Weissella confusa were variously found in the 4 cheeses. Random amplification of polymorphic DNA-PCR analysis showed the biodiversity among the strains, and the species of lactobacilli were in part grouped according to their origin. As shown by the principal component analysis of reverse-phase fast protein liquid chromatography data for the pH 4.6-soluble fractions and by the determination of free AA, the secondary proteolysis of Barricato San Martino and Vento d’Estate mainly differed from the other 2 cheeses. Purge-and-trap and solid-phase microextraction were coupled with gas chromatography-mass spectrometry to determine volatile compounds. Vento d’Estate showed the highest levels of almost all chemical classes, and Casciotta di Urbino was characterized by a very low level of volatile components. Esters, ketones, and terpenes were the chemical classes that mainly differentiated the cheeses. Several volatile compounds seemed to be released directly from the plant materials used for ripening, especially terpenes for Vento d’Estate cheese. The lowest level of volatile free fatty acids was found in Casciotta d’Urbino, in which rennet paste was not used during manufacture. The highest concentration of free fatty acids, especially butyric and caproic acids, was found in Vento d’Estate cheese.     

Characterisation of proteolysis profile of Argentinean sheep cheeses made by two different production methods

BACKGROUND: In this work the proteolysis profiles of Argentinean sheep cheeses made by two different production methods were studied in order to develop products with typical and defined features. Cheeses with a starter of Streptococcus thermophilus, curd cut to corn grain size, washed and heated to 43 °C (S cheeses) and cheeses with a mixed starter of Streptococcus thermophilus, Lactobacillus helveticus and Lactobacillus bulgaricus, curd cut to rice grain size, unwashed and heated to 47 °C (L cheeses) were manufactured. The cheeses were ripened at 12 °C and 80% relative humidity for 180 days and samples were taken throughout this period. RESULTS: Gross composition and primary proteolysis were similar for both types of cheeses. Streptococci counts diminished from 10⁹ to 10⁷ colony‐forming units g^?1 during ripening in both S and L cheeses. Lactobacilli counts in L cheeses decreased during ripening and disappeared at 180 days. L cheeses had significantly lower pH values and showed higher peptidolysis than S cheeses. Triangle sensory evaluation indicated important differences between the two types of cheeses. CONCLUSION: S cheeses had a low proteolysis level and a soft flavour, making them appropriate for consumption after a short ripening time. L cheeses had a higher proteolysis level and more intense sensory characteristics, making them appropriate for consumption after a longer ripening time. Copyright © 2009 Society of Chemical Industry     

Factors affecting Penicillium roquefortii (Penicillium glaucum) in internally mould ripened cheeses: implications for pre‐packed blue cheeses

The amount and vivid colour of blue veins of internally mould ripened cheeses are desirable quality characteristics. It is therefore important that there is a sufficient amount of veining and that it maintains its blue appearance to be appealing to consumers therefore leading to maximised sales potential and profit for the manufacturing company. Optimum in vitro growth mimicking the conditions typically found in pre‐packed blue cheeses, and using lactose as the sole carbon source, was facilitated by a gas mixture of 5% oxygen/0% carbon dioxide/balance nitrogen). The work undertaken in this study determined that the factors for optimum in vitro growth of Penicillium roquefortii (strain PRB6) were: a temperature of 20 ± 1 °C, pH of 6.0 ± 0.1, and a relative humidity of 70 ± 0.1%. Further in vitro studies have also shown that the increasing ‘in‐pack’ carbon dioxide concentration not only depresses the growth of P. roquefortii but also affects immature conidiospore pigmentation (no effect has been seen on mature conidiospore pigmentation). The implications of this study suggest that the majority of pre‐packed internally mould ripened blue cheeses on sale in supermarkets are packaged in inappropriate materials. For some cheeses (e.g. the Roquefort‐type cheeses) this is not an issue since these are packed in a much more mature state and some loss of veining colour is not appreciably noticeable.     

Survey of benzoic acid in cheeses: contribution to the estimation of an admissible maximum limit

Benzoic acid and its salts are commonly used additives in the food industry. Their use is not allowed in dairy products even though they can be found naturally. In this work, 100 cheese samples were tested to establish the maximum concentration that can be considered as “natural” and, therefore, permitted in cheeses. Analyses were carried out by a validated ion chromatography method and “positive” samples were confirmed by two other HPLC methods. Benzoic acid concentrations higher than the method LOQ (8.8?mg?kg^?1) were found in 18 samples, ranging from 11.3 to 28.7?mg?kg^?1, with a mean value of 20.5?mg?kg^?1. Taking into account the distribution of benzoic acid concentrations observed in “positive” samples, it is plausible to estimate a maximum admissible limit of 40.0?mg?kg^?1 for benzoic acid in cheese. Below this value, samples can be considered “compliant”.     

Identification of ACE-inhibitory peptides in different Spanish cheeses by tandem mass spectrometry

Different Spanish cheeses (Cabrales, Idiazábal, Roncal, Manchego, Mahón and a goat's milk cheese), made with diverse technologies and milk from different species, were studied for their angiotensin converting enzyme (ACE)-inhibitory activity. Among the water-soluble extract WSE<1000-Da of the different samples, Cabrales cheese was the most active with an inhibitory activity of 76.1%. On the contrary, Mahón cheese showed the lowest ACE-inhibitory index (56.6%). In order to identify the peptides involved in this activity, the WSE<1000-Da were analyzed by HPLC-MS/MS and off-line MS/MS. A total of 41 major peptides were identified in the different cheeses. Most of them derived from β-and α_s1-casein. Several of these peptides were selected on the basis of the presence of proline as the C-terminal amino acid, and they were chemically synthesized. All peptides showed moderate or low ACE-inhibitory activity. Peptide DKIHP [β-CN f(47–51)], a sequence detected in all samples except Mahón cheese, showed the highest inhibitory activity with an IC₅₀ value of 113.1 μM.     

Effect of ohmic treatment on quality characteristic of meat: A review

Ohmic cooking, a well-known electro-heating technique, provides an alternative method for cooking meat products due to its ability for rapid heat generation. Ohmic heating uses the resistance of meat products to convert the electric energy into heat. The rate of heat generation depends on the voltage gradient applied and the electrical conductivity of the meat product. The advantages of ohmic cooking over conventional heating include shorter processing times, higher yields, and less power consumption while still maintaining the colour and nutritional value of meat products. In recent years, ohmic cooking has increasingly drawn interest from the meat industry as a method to ensure the quality and the safety of meat products. The present paper reviews the effects of ohmic cooking on the physical, chemical, sensory, and microbiological quality characteristics and toxicological properties of meat and meat products.     

Viability of Salmonella enterica subsp. enterica during the preparation and cold storage of Egyptian soft cheeses and ice-cream

Changes occurring in the viability of Salmonella enterica subsp. enterica during the preparation and cold storage of Domiati cheese, Kariesh cheese and ice-cream were examined. A significant decrease in numbers was observed after whey drainage during the manufacture of Domiati cheese, but Salmonella remained viable for 13 weeks in cheeses prepared from milks with between 60 and 100 g/L NaCl; the viability declined in Domiati cheese made from highly salted milk during the later stages of storage. The method of coagulation used in the preparation of Kariesh cheese affected the survival time of the pathogen, and it varied from 2 to 3 weeks in cheeses made with a slow-acid coagulation method to 4–5 weeks for an acid-rennet coagulation method. This difference was attributed to the higher salt-in-moisture levels and lower pH values of Kariesh cheese prepared by the slow-acid coagulation method. A slight decrease in the numbers of Salmonella resulted from ageing ice-cream mix for 24 h at 0°C, but a greater reduction was evident after one day of frozen storage at −20°C. The pathogen survived further frozen storage for four months without any substantial change in numbers.     

Microbiological quality of retail cheeses made from raw, thermized or pasteurized milk in the UK

Two studies of retail fresh, ripened and semi-hard cheeses made from raw, thermized or pasteurized milk were undertaken in the UK during 2004 and 2005 to determine the microbiological quality of these products. Using microbiological criteria in European Commission Recommendations 2004/24/EC and 2005/175/EC, 2% of both raw, thermized (37/1819 samples) and pasteurized (51/2618 samples) milk cheeses were of unsatisfactory quality. Raw or thermized milk cheeses were of unsatisfactory quality due to levels of Staphylococcus aureus at 10(4)cfu g(-1), Escherichia coli at 10(5)cfu g(-1), and/or Listeria monocytogenes at 10(2)cfu g(-1), whereas pasteurized milk cheeses were of unsatisfactory quality due to S. aureus at 10(3)cfu g(-1) and/or E. coli at 10(3)cfu g(-1). Salmonella was not detected in any samples. Cheeses were of unsatisfactory quality more frequently when sampled from premises rated as having little or no confidence in management and control systems, and stored/displayed at above 8 degrees C. Raw or thermized milk cheeses were also more likely to be of unsatisfactory quality when they were unripened types, and pasteurized milk cheeses when they were: semi-hard types; from specialist cheese shops or delicatessens; cut to order. These results emphasize the need for applying and maintaining good hygiene practices throughout the food chain to prevent contamination and/or bacterial growth. Labelling of cheeses with clear information on whether the cheese was prepared from raw milk also requires improvement.     

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.     

Microbial succession of Debaryomyces hansenii strains during the production of Danish surfaced-ripened cheeses

Surface-ripened cheeses of the Danbo type were analyzed for the presence of yeasts with special emphasis on Debaryomyces hansenii. Samples were taken from pasteurized milk, brine, and inoculation slurries and from cheese surfaces during ripening at a Danish dairy. D. hansenii was found to be the dominant yeast species throughout the ripening period, whereas other yeast species such as Trichosporon spp., Rhodotorula spp., and Candida spp. were found in minor concentrations during early stages of cheese ripening. Mitochondrial DNA RFLP was used to show that several strains of D. hansenii were present from the onset of ripening. Thereafter, a microbial succession among the strains took place during the ripening. After 3 d of ripening, only one strain was found. This particular strain was found to be dominant in 16 additional batches of surface-ripened cheeses. We investigated the cause of the observed microbial succession by determining the variation in strains with regard to their ability to grow on lactate and at different pH and NaCl concentrations. The strains were shown to vary in their ability to grow on lactate. In a full factorial design at three levels with factor levels close to the actual levels on the cheese surface, differences in pH and NaCl tolerances were observed. The dominant strain was found to be better adapted than other strains to the environmental conditions existing in surface-ripened cheeses during production [e.g., lactate as the main carbon source, pH 5.5 to 6.0 and NaCl concentrations of 7 to 10% (wt/vol)].     

Controlled production of Camembert-type cheeses. Part I: Microbiological and physicochemical evolutions

A holistic approach of a mould cheese ripening is presented. The objective was to establish relationships between the different microbiological and biochemical changes during cheese ripening. Model cheeses were prepared from pasteurized milk inoculated with Kluyveromyces lactis, Geotrichum candidum, Penicillium camemberti and Brevibacterium linens under aseptic conditions. Two cheese-making trials with efficient control of environmental parameters were carried out and showed similar ripening characteristics. K. lactis grew rapidly between days 1 and 6 (generation time around 48 h). G. candidum grew exponentially between days 4 and 10 (generation time around 4.6 d). Brevi. linens also grew exponentially but after day 6 when Pen. camemberti mycelium began developing and the pH of the rind was close to 7. Its exponential growth presented 3 phases in relation to carbon and nitrogen substrate availability. Concentrations of Pen. camemberti mycelium were not followed by viable cell count but they were evaluated visually. The viable microorganism concentrations were well correlated with the carbon substrate concentrations in the core and in the rind. The lactose concentrations were negligible after 10 d ripening, and changes in lactate quantities were correlated with fungi flora. The pH of the inner part depended on NH3. Surface pH was significantly related to NH3 concentration and to fungi growth. The acid-soluble nitrogen (ASN) and non-protein nitrogen (NPN) indexes and NH3 concentrations of the rind were low until day 6, and then increased rapidly to follow the fungi concentrations until day 45. The ASN and NPN indexes and NH3 concentrations in the core were lower than in the rind and they showed the same evolution. G. candidum and Pen. camemberti populations have a major effect on proteolysis; nevertheless, K. lactis and Brevi. linens cell lysis also had an impact on proteolysis. Viable cell counts of K. lactis, G. candidum, Pen. camemberti and Brevi. linens were correlated with the environmental conditions, with proteolytic products and with carbon substrate assimilation. NH3 diffusion from surface to the cheese core during ripening was highly suspected. Interaction phenomena between microorganisms are discussed.     

Diversity of lactic acid bacteria in two Flemish artisan raw milk Gouda-type cheeses

PCR-denaturing gradient gel electrophoresis (PCR-DGGE) was used to study the diversity of lactic acid bacteria (LAB) in two Flemish artisan raw milk Gouda-type cheeses. In parallel, conventional culturing was performed. Isolates were identified using (GTG)(5)-PCR and sequence analysis of 16S rRNA and pheS genes. Discriminant analysis revealed some differences in overall LAB diversity between the two batches and between the two cheeses. Within each batch, the diversity of 8- and 12-week-old cheeses was relatively similar. Conventional isolation mainly revealed the presence of Lactobacillus paracasei, Lactobacillus plantarum, Lactobacillus brevis, Lactobacillus rhamnosus and Pediococcus pentosaceus. PCR-DGGE revealed the presence of three species of which no isolates were recovered, i.e. Enterococcus faecalis, Lactobacillus parabuchneri and Lactobacillus gallinarum. Conversely, not all isolated bacteria were detected by PCR-DGGE. We recommend the integrated use of culture-dependent and -independent approaches to maximally encompass the taxonomic spectrum of LAB occurring in Gouda-type and other cheeses.     

Characterization of lactic acid bacteria isolated from raw cows’ milk cheeses currently produced in Galicia (NW Spain)

Twenty cheeses belonging to the four Protected Designations of Origin manufactured in Galicia (NW Spain) (6 Arzúa-Ulloa, 4 Tetilla, 6 Cebreiro and 4 San Simón da Costa) were selected from a total of 60 cheeses on basis of their (typical) sensorial profiles. A total of 218 lactic acid bacteria (LAB) isolates were obtained from the predominant microflora of the selected cheeses and were identified as Lactococci (98 isolates), Leuconostocs (56), Mesophilic Lactobacilli (54), Pediococci (8) and Enterococci (2). Eighty-four of the isolates produced mainly malty, spicy or sulfide flavours in pasteurised whole milk, and were not characterized further. Some good producers of diacetyl-acetoin in milk (>100 mg/L) were found among a total of 129 LAB selected, although the isolates were generally less acidifying and less proteolytic than many of those obtained 10-15 years ago. The results suggest that the microflora in cheese-making environments have undergone changes, with the most evident difference being the practical absence of Enterococcal strains among the current isolates.     

Changes of composition and free fatty acid contents of Urfa cheeses (a white-brined Turkish cheese) during ripening: Effects of heat treatments and starter cultures

The influences of heat treatments (at 65 °C for 20 min or 72 °C for 5 min) applied to the milk and addition of mesophilic or thermophilic starter cultures, prior to cheese-making, on the composition and free fatty acid contents of Urfa cheeses were evaluated throughout the ripening period. Sensory evaluation of cheese samples was also performed on 90th day. The basic composition of ripened cheese samples was not significantly affected by the heat treatments and starter cultures. Heat treatments adversely affected the lipolysis and sensory properties of Urfa cheeses, particularly at 72 °C. The FFA contents of cheeses made from mesophilic and thermophilic cultures were similar. Cheese made from raw milk had a higher level of lipolysis than the cheeses made from milk inoculated with mesophilic or thermophilic lactic starters (p < 0.05).     

Microbiological and chemical characterization of honeys from central Argentina

The characterization of some honey samples from southern Córdoba (Argentina) was carried out on the basis of their microbiological (Clostridium, fungi and yeasts), physical (colour) and chemical (carbohydrates, HMF, water and free acidity) analysis. The results showed that honeys produced in this region are of good quality. HMF content and free acidity values were mostly low, indicating honey freshness. Most of the samples contained less than 20% water. Glucose and fructose accounted for more than 60% of the weight. The amount of yeast and fungi found in the honey samples was less than 1 × 10² CFU/g. Low quantities of vegetative cells and spores of Clostridia were found in some honey samples. A standardization and a rationalization of beekeeping techniques throughout southern Córdoba may further improve honey quality, and ensure it over the years.     

Invited review: Hispanic-style cheeses and their association with Listeria monocytogenes

The rise in consumption of Hispanic-style cheeses (HSC), due in large part to the increasing Hispanic population in the United States, has not been met with advances in food safety sufficient to prevent the numerous outbreaks and recalls due to Listeria monocytogenes. Hispanic-style cheeses are typically high moisture and have low salt content and low acidity from being subjected to little to no ripening. These conditions necessitate refrigeration to maintain safety and quality, as the majority of traditional extrinsic preservation methods are either ineffective or disrupt the mild sensory attributes of HSC. Unfortunately, the cold-growth of L. monocytogenes presents significant problems from post-pasteurization contamination or insufficient pasteurization. In this review, we discuss the factors affecting listerial contamination and growth in HSC, and present current knowledge of L. monocytogenes incidence in manufacturing settings and commercial prevalence. Furthermore, we differentiate HSC types by processing methods to aid with interpretation of works involving nonstandardized varieties and, finally, summarize research on intervention methods for eliminating listerial contaminants in HSC.