Assimilation of cholesterol by yeast strains isolated from infant feces and Feta cheese

Eight yeast strains isolated from infant feces and the traditional Greek Feta cheese, selected for their probiotic properties, were tested along with a commercially available strain of Saccharomyces boulardii for their ability to remove cholesterol from a growth medium (yeast extract glucose peptone broth) supplemented with 0.3% Oxgall. The amount of cholesterol removed during 72 h of growth at 37 degrees C revealed significant variations among the yeast strains examined. Two isolates from infant feces, namely Saccharomyces cerevisiae KK1 and Isaatchenkia orientalis KK5.Y.1 and one isolate from Feta cheese, namely S. cerevisiae 832, along with the commercial strain S. boulardii, were able to remove cholesterol from the growth medium after 48 h of incubation at 37 degrees C. However, Saccharomyces strains proved to be able to remove cholesterol even after 24 h of growth at 37 degrees C. The cholesterol removed from the growth medium was not metabolically degraded but was rather assimilated into the yeast cells. The ability to assimilate cholesterol in vitro and to tolerate low pH levels, gastric juice, and bile indicate that S. cerevisiae 832, and especially S. cerevisiae KK1 and I. orientalis KK5.Y.1 (being more bile and gastric juice tolerant because of their human origin) may be promising candidate strains for use as probiotics.     

Some characteristics of Lactobacillus isolates from infant faeces

In this research, 21 strains of lactobacilli were isolated from newborn infant faeces. Lactobacillus rhamnosus (seven strains), L. paracasei ssp. paracasei (four strains), L. fermentum (four strains), L. buchneri (two strains), L. brevis (one strain), L. curvatus (one strain) and Lactobacillus sp. (two strains) isolated from infant faeces were analysed for acid production, antibiotics resistances, H₂S productions and antimicrobial activities.Inhibition activity of bacteriocins and/or bacteriocin-like substances of the lactobacilli against some food contaminants and pathogenic bacteria (Escherichia coli, Staphylococcus aureus ATCC 28213, S. aureus ATCC 2392, Yersinia enterocolitica and Bacillus cereus) were determined by the agar diffusion method.     

Production of probiotic Feta cheese using Propionibacterium freudenreichii subsp. shermanii as adjunct

Probiotic Feta cheese was produced using Propionibacterium freudenreichii subsp. shermanii as an adjunct since it has been shown to induce apoptosis of colon cancer cells in vitro and in vivo through the production of propionate and acetate. Microbiological and physicochemical analysis of the cheese was performed through the 60 d period of ripening. Counts of propionibacteria increased until day 7 and then remained constant until the end of ripening (approximately 9 log cfu g⁻¹). Moreover, throughout ripening the presence of P. freudenreichii subsp. shermanii LMG 16424^T was confirmed by 16S rRNA gene sequence analysis, while propionic acid was first detected on day 7 and reached a concentration of 52.1 mm on day 60. The ripened cheese containing P. freudenreichii subsp. shermanii was very well accepted by the sensory evaluation panellists. This is the first time that P. freudenreichii subsp. shermanii was studied as a probiotic adjunct in a white-brined cheese.     

Characterization of Lactobacillus isolates from infant faeces as dietary adjuncts

Lactobacillus paracasei subsp. paracasei (six strains), Lb. rhamnosus (six strains), Lb. acidophilus (two strains), Lb. gasseri (three strains) and Lb. reuteri (three strains) isolates from new-born infants were tested for their ability to grow and metabolize in milk and to resist specific conditions of the gastrointestinal tract. Many of the tested strains had desirable properties concerning their ability to withstand adverse conditions of the gastrointestinal tract, and produce carbonyl compounds. In general, strains of Lb. paracasei subsp.paracasei and Lb. rhamnosus were more resistant to low pH of the stomach than all the other strains. On the other hand, Lb. gasseri and Lb. reuteri strains did not acidify milk. Thus, Lb. paracasei subsp.paracasei , Lb. acidophilus and Lb. rhamnosus strains could be preferably used as starters to produce fermented milks with possibly interesting organoleptic properties, as well as dietary and possible therapeutic importance.     

Microflora of Feta cheese from four Greek manufacturers

The components of the microflora of four Feta cheeses, produced by different Greek manufacturers, were determined by culture dependent and independent techniques. Isolates from microbiological media were first grouped by Polymerase Chain Reaction-Denaturing Gradient Gel Electrophoresis (PCR-DGGE) and then representatives of each DGGE group were sequenced for identification purposes. DNA and RNA, extracted directly from the cheese, were subjected to PCR-DGGE. Moreover, Feta cheeses were subjected to FISH analysis in order to identify viable bacterial populations. The microbial ecology, as represented by the Lactic Acid Bacteria (LAB) and yeast populations, was different for the four cheeses. The main LAB species isolated were Lactobacillus plantarum, Lactobacillus brevis, Lactobacillus coryniformis and Lactobacillus fermentum. However, some inconsistencies were observed between the results obtained with the culture dependent and the culture independent approach. In the case of the yeasts, the results obtained by PCR-DGGE compared very well with those obtained by the conventional microbiological analysis and the main species found were Kluyveromyces lactis, Pichia fermentans and C. zeylanoides. FISH analysis highlighted viable but not culturable populations of Streptococcus thermophilus and Lactococcus spp. RAPD-PCR performed on the L. plantarum isolates revealed a cheese specific distribution and a temperature dependent clustering.     

Evaluation of iron‐fortified Feta cheese for physicochemical and sensory properties

Standardised cow's milk (fat 3 g/100 g) was used to manufacture Feta cheese fortified with 40, 60 and 80 mg of iron/kg cheese using ferrous sulphate (FeSO₄), ferric chloride (FeCl₃), ferric pyrophosphate (Fe₄ (P₂O₇)₃) and microencapsulated ferrous sulphate. Chemical composition and sensory characteristics of fortified cheeses were determined after 60 days of ripening, during which the iron content and thiobarbituric acid (TBA) values were measured. The metallic taste, colour, flavour, overall score and TBA values were statistically (P < 0.05) affected by the source and concentration of iron. The best quality was found in cheeses fortified with 40 mg/kg of microencapsulated ferrous sulphate.     

Migration of water-soluble nitrogenous compounds of Feta cheese from the cheese blocks into the brine

The migration of water-soluble nitrogenous compounds of Feta cheese from the cheese into brine was monitored over a 5-month period, and the nature of the compounds diffusing into the brine was investigated. Reversed-phase high-performance liquid chromatography analysis of the water extract of Feta cheese and of the brine showed that both contained serum proteins and various peptides; the chromatographic profiles changed with the age of the cheese. Also, differences between chromatograms of the water extract of the cheese and the brine at the same age were observed. It seems likely that the parameters driving the solubility of peptides in 120 g L⁻¹ trichloroacetic acid (size and hydrophobicity) also determine their potential for diffusion into the brine. Amino acids also migrate into the brine, with the hydrophobicity and shape of the side chain governing their diffusing ability.     

Role of salt in Iranian ultrafiltered Feta cheese: Some textural and physicochemical changes during ripening

The effect of NaCl (0–4%) on the ripening of Iranian ultrafiltered (UF)‐Feta cheese was assessed over 120 days of ripening at 4 °C. Whey percentage, whey salt, whey pH, cheese pH and textural properties of hardness and cohesiveness were monitored, and experimental modelling performed using response surface methodology. Texture, pH and whey percentage were significantly affected by NaCl and ripening. The maximum whey of 22% was recorded at the end of ripening period. Texture of this cheese becomes harder during ripening confirming cheese pH and whey percentage being the major determining factors. Cheese samples were more elastic than viscous with cohesiveness values of 0.6–0.9.     

Lactobacillus spp. with in vitro probiotic properties from human faeces and traditional fermented products

Lactobacillus strains from traditional African fermented milk products, as well as human intestinal isolates were identified and investigated in vitro for their technological and functional characteristics as potential new probiotic strains. To test survival under gastrointestinal conditions, first the protective effect of milk and the effects of medium composition, lysozyme, pepsin, and pH of the medium on bacterial viability were assessed in vitro using the Plackett-Burman statistical model and the commercially used L. johnsonii LA1 probiotic strain. The use of either an artificial gastric electrolyte solution or MRS did not play a significant role in the viability of the cultures, while lysozyme, acidic conditions (pH 2.5), pepsin and the presence of milk significantly influenced the survival of the strain. Therefore, these parameters were selected as important test variables in a model stomach passage survival trial. Five strains identified as L. plantarum and two identified as L. johnsonii showed good survival under simulated gastrointestinal conditions. These selected strains also showed antimicrobial activity, probably due to production of organic acids. All strains exhibited bile salt hydrolase activity, while only the L. plantarum strains showed beta-galactosidase activity.     

Proteolysis and textural properties of low‐fat ultrafiltered Feta cheese as influenced by maltodextrin

Maltodextrin was used as a fat replacer in low‐fat ultrafiltered cheese. Fat was replaced with 25% maltodextrin milk solution (w/w) in cheese at 15 and 50% (w/w). The chemical, rheological and sensory properties as well as the microstructure of the cheese samples were evaluated after storage for 2 months at 8 °C. Maltodextrin affected the chemical (pH, dry matter, fat, water‐soluble nitrogen to total nitrogen, nonprotein nitrogen to total nitrogen, total free amino acid) and rheological (mean relaxation time) properties, as well as the microstructure. In general, based on textural properties, sensory evaluation and economic aspects, the 50%‐fat‐reduced sample was selected as the best treatment.     

Evolution of microbial populations during traditional Feta cheese manufacture and ripening

In three different dairies (A, B and C) located in Peloponess region (Southern Greece), traditional Feta cheese trials took place February to March using mixtures of sheep's and goat's milk. Only small variations in the evolution of microbial groups were observed during the whole ripening period. The main groups, such as thermophilic cocci, mesophilic lactococci, thermophilic lactobacilli, nonstarter lactic acid bacteria (NSLAB), presumptive Leuconostoc, enterococci and micrococci, reached their highest levels during the first 16 days, and then declined approximately 1-2 log units until the end of ripening. The remaining groups investigated, comprising yeasts, coliforms and Escherichia coli, were highest at day 4. The yeasts remained constant, while coliforms and E. coli decreased sharply and were not detectable after 120 days of ripening. A number of 146 isolates (dairy A) taken from all stages of the manufacturing and ripening process were purified and studied. Lactobacillus plantarum (58/146) and isolates of related species Lactobacillus pentosus and Lactobacillus paraplantarum (16/146) were the most common microorganisms found during cheese ripening. Streptococcus thermophilus (23/146) and Lactobacillus delbrueckii subsp. bulgaricus (20/146) were detected in high levels up to 20 days, and then gradually reduced. Enterococcus faecium (29/146) was found in all manufacturing and ripening stages.     

Effects of Mentha longifolia L. essential oil on viability and cellular ultrastructure of Lactobacillus casei during ripening of probiotic Feta cheese

The effects of Mentha longifolia L. essential oil during ripening and storage probiotic Feta cheese were studied, in relation to viability and cellular ultrastructure of Lactobacillus casei. The addition of the essential oil in the concentrations from 0.0 to 0.03% was trialled: the 0.03% treatment resulted in the highest viability of L. casei and the lowest pH value compared with other treatments (P < 0.05). Electron microscopy showed that essential oil caused no harm to L. casei. This study demonstrated the favourable effects of M. longifolia on optimal maintenance of L. casei at the end of cheese storage period.     

Evolution of lipolysis during the ripening of traditional Feta cheese

Lipolysis was studied during ripening of traditional Feta cheese produced in two small dairies, A and B. The cheeses were made from a thermized mixture of ewes’/goats’ milk by using yoghurt as starter and artisanal rennet from lambs’ and kids’ abomasa (cheese A) or mixed artisanal rennet with calf rennet (cheese B).The acid degree value and the free fatty acids (FFA) contents in both cheeses increased sharply up to 18 d (pre-ripening period at 15 °C) and continued to increase throughout ripening. In both mature cheeses, acetic acid was found at high levels (13–18% of the total FFAs). However, except for this, all FFA contents differed significantly (P < 0.05) between the two cheeses throughout ripening. The levels of individual and total C2:0–C8:0, C10:0–C14:0 and C16:0–C18:2 fatty acids were significantly higher (P < 0.05) in cheese A than in cheese B. Presumably the difference, especially in the C2:0–C8:0 content, was due mainly to the type of the rennet used. Butyric acid was the dominant FFA in cheese A (20% of the total FFAs at 120 d), while the most abundant FFAs in cheese B were capric (18%) and lauric acid (18%). In general, the lipolysis degree of the two cheeses was higher than those reported for the industrially-made Feta cheese.In organoleptic evaluation, cheese A had a piquant taste that was attributed to its high content of butyric acid and showed a significantly (P < 0.05) higher total score than cheese B.     

Preparation and properties of probiotic cheese high in conjugated linoleic acid content

The development of probiotic Ras cheese rich in conjugated linoleic acid (CLA) was investigated using probiotic Lactobacillus casei and Lactobacillus acidophilus starters. The cheeses were assessed for composition, proteolysis, fatty acids and fat stability, and microbiology during 3 months of ripening. The cheese made with Lb. casei and Lb. acidophilus retained high counts of the probiotic strains (～log 8) throughout storage. Ripening changes followed the normal pattern of this type of cheese during ripening. Ras cheese made with Lb. casei and Lb. acidophilus contained the highest CLA content (0.84% after 3 months) as compared to control and cheese fat had acceptable oxidative stability.     

Effect of draining temperature on the biochemical characteristics of Feta cheese

Two different draining temperatures, 15 and 21°C were applied to five Feta cheese curds made with different starters, containing mesophilic or thermophilic strains or mixtures of them. After 20 h of draining, the pH of curds made with thermophilic starters ranged from 5.28 to 5.49. The draining temperature significantly affected (P<0.05) the pH and the total solids of the cheeses. The inclusion of whey proteins in the cheese curd due to the insufficient draining of cheeses at 15°C, resulted in higher water-soluble nitrogen (WSN), as % of total nitrogen content. Free amino acid contents were significantly affected (P<0.05) by the draining temperature and by the presence of thermophilic lactobacilli in the starter mixture. Draining temperature also significantly affected (P<0.05) residual α_s- and β-casein and the RP-HPLC profiles of the WSN. The C_2:0 to C_8:0 free fatty acids, hardness (kg) and fracturability (kg), as well as the total organoleptic scores, were significantly (P<0.05) higher in feta drained at 21°C.     

Influence of residual rennet and proteolysis on the exudation of whey from Feta cheese during storage

A change in the quantity of rennet added to the cheesemilk resulted in a corresponding change in the level of residual rennet in Feta cheese. Casein proteolysis and exudation of whey from Feta cheese during storage were proportional to the quantity of residual rennet in the cheese. It is likely that with proteolysis, the three-dimensional casein network becomes weaker and gradually disintegrates. The water-holding ability of the casein gels is thereby greatly reduced and moisture is released from the interstices of the casein gel. This free moisture and soluble material, including peptides and amino acids formed during proteolysis, are released as exudate during the storage of Feta cheese.     

Feta cheese texture: the effect of caprine and ovine milk concentration

Feta cheese was produced commercially with different caprine to ovine milk ratios. Milk fat concentrations, moisture and salt contents were similar for all the batches. However, the hardness and adhesive characteristics of the cheeses differed in relation to the milk ratio. The hardness of the cheese appeared to be correlated to increased goat milk content. Cryo-scanning electron microscopy (cryo-SEM) of the cheese samples showed that feta cheese with a higher proportion of caprine milk had a more compact and less porous appearance than feta produced from purely ovine milk. This difference in cheese structure helps to explain the difference in hardness between the samples.     

The influence of probiotic bacteria on the properties of Iranian white cheese

The viability of Bifidobacterium animalis (ATCC 25527) and Lactobacillus rhamnosus (ATCC 7469), study of interaction between probiotic and starter and their effect on the properties of Iranian white cheese were investigated during 60 days of ripening. The results indicated that probiotics did not exert any effect on the growth of commercial starters, but starters showed a synergistic effect on the growth of probiotics, and probiotics survived above the recommended level for the therapeutic minimum (10⁶–10⁷ cfu/g) after 60 days. Addition of probiotic adjunct did not alter the chemical composition except for moisture and protein. Also, the highest pH value was in probiotic cheeses without starter.     

Some properties of Civil cheese: a type of traditional Turkish cheese

Civil cheeses were purchased from urban vendors in the city centre of Erzurum, Turkey. The biogenic amine contents of the cheeses and their microbiological and chemical properties were determined. It was found out that biogenic amine concentrations of the samples were not exceeding the toxic doses‐values. Total aerobic mesophilic bacteria, lactic acid bacteria and Enterobacteriaceae spp. were investigated as microbial analyses in the samples while several chemical analyses were executed. Statistical analyses were carried out for the determination of the relationship between the chemical properties and the biogenic amine contents of samples, and the existence of microorganisms and biogenic amines.     

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.