Barbaros Özer

Survival of Lactobacillus acidophilus LA-5 and Bifidobacterium bifidum BB-02 in white-brined cheese

The viability of probiotic cultures used as adjunct cultures including Bifidobacterium bifidum BB-02 and Lactobacillus acidophilus LA-5 in white-brined cheese was investigated. The microbiological and biochemical properties of cheeses were assessed throughout 90 days of storage. Two inoculum rates for probiotic starters (2.5% and 5.0%, v/v, corresponding to (1.0–1.3)×109 cfu/g and (2.0–2.1)×109 cfu/g, respectively) were compared with the control cheese. Results obtained showed that a higher inoculum rate resulted in faster proteolysis. The cheese inoculated with 5% probiotic strains had higher water-soluble nitrogen, non-protein nitrogen, proteose-peptone nitrogen and tyrosine values than the other experimental cheeses. At the end of storage, the cheese supplemented with 5% probiotic culture had a ripening coefficient of 28.3%, followed by 2.5% probiotic strains containing the sample being 24.9%, and the control being 23.6%, respectively. It was also found that the colony counts of both probiotic microorganisms declined during storage. After 90 days of storage, the number of probiotic colonies were still around the threshold for a minimum probiotic effect (106 cfu/g).

Gelation Properties of Milk Concentrated by Different Techniques

The rheological properties of three different concentrated yoghurts (∼23% total solids, pH 4.0) and a standard yoghurt (∼16% total solids, pH 4.3) were determined during incubation and storage. The high solids yoghurts were manufactured from milks concentrated by ultrafiltration (UF) to 9% protein, by reverse osmosis (RO) to ∼6.8% protein and by direct reconstitution of full-fat milk powder to ∼6.4% protein; the standard product contained ∼4.3% protein. Development of the gel structures during incubation was monitored discontinuously using a stress-controlled oscillatory dynamic rheometer. The complex modulus (G∗) and loss tangent (tanδ) were measured as functions of amplitude (torque range 10-3–10-2 mNm at 0.25 Hz). In the RO- and direct reconstitution yoghurts, a typical pattern of gelation was observed, with the initial viscous nature of the milk being modified by rapid development of a gel structure and, finally, a ‘stationary phase’ with respect to rheological changes. However, the complex modulus (G∗) of the higher protein system (UF-milk) continued to increase with time, i.e., further development of the gel structure occurred during storage. The relative rates of gel development were dependent on protein content.

Effects of lactoperoxidase and hydrogen peroxide on rheological properties of yoghurt

The effects of activation of the lactoperoxidase (LPO) system by H2O2-NaSCN and hydrogen peroxide (H2O2) on the accessibility of sulphydryl groups (SH) in skimmed milk, and on the dynamic rheological properties of the resulting yoghurt were investigated. Four different concentrations of each reagent (20-80 mg H2O2-NaSCN/kg milk and 100-400 mg H2O2/kg milk) were compared. Clear negative correlations were noted between the accessibility of SH groups and both LPO activation rate and H2O2 concentration. Also the native PAGE pattern of the heat-treated samples showed that with increase in the H2O2-NaSCN and H2O2 concentrations, the level of interaction between beta-lactoglobulin (beta-lg) and kappa-casein (kappa-CN) decreased. The complex modulus (G*) of skimmed milk yoghurts declined gradually with the decrease in the concentration of accessible SH groups accordingly. Tan delta values of yoghurt samples were found to be different from the control, but close to each other, indicating that protein interaction forces taking place in the formation of gel networks of treated yoghurts were different from the control.

Effects of different fermentation parameters on quality characteristics of kefir.

The main objective of the study was to determine the effects of different fermentation parameters on kefir quality. Kefir samples were produced using kefir grains or natural kefir starter culture, and fermentation was carried out under normal or modified atmosphere (10% CO(2)) conditions. The microbiological (lactobacilli, lactococci, Lactobacillus acidophilus, Bifidobacterium spp., and yeasts), chemical (pH, lactic acid, total solids, protein, ethanol, exopolysaccharide contents), rheological, and sensory properties of kefir samples were investigated during a 21-d storage period. The use of different fermentation parameters or the choice of grain versus natural kefir starter culture did not significantly affect the content of microorganisms. Lactobacilli, lactococci, and yeast contents of kefir samples varied between 9.21 and 9.28, 9.23 and 9.29, and 4.71 and 5.53 log cfu/mL, respectively, on d 1 of storage. Contents of L. acidophilus and Bifidobacterium spp. were between 5.78 and 6.43 and between 3.19 and 6.14 log cfu/mL, respectively, during 21 d of storage. During the storage period, pH, lactic acid (%), total solids (%), protein (%), acetaldehyde, and ethanol contents of kefir samples ranged from 4.29 to 4.53, from 0.81 to 0.95%, from 7.81 to 8.21%, from 3.09 to 3.48%, from 3.8 to 23.6 mg/L, and from 76.5 to 5,147 mg/L, respectively. The exopolysaccharide contents of the samples decreased during 21 d of cold storage; the samples fermented under modified atmosphere had relatively higher exopolysaccharide contents, indicating higher potential therapeutic properties. The kefir samples exhibited non-Newtonian pseudoplastic flow behavior according to the power law model. According to the sensory results, kefir produced from natural kefir starter culture under CO(2) atmosphere had the highest overall evaluation score at d 1.

Recent Advances in Dairy Packaging

The type of packaging material for dairy products is of critical importance because of its impact on quality, safety, cost, and marketing of the commodities to consumers. Recently, interest has shifted towards novel applications such as smart or intelligent packaging, modified atmosphere and active packaging, and sustainability. This article reviews recent applications and trends in the packaging of dairy products such as evaporated, sweetened condensed, and powdered milks, ice cream, butter, acidified dairy products, and cheeses.

Identification and characterisation of lactic acid bacteria isolated from traditional Urfa cheese

In this study, characterisation of dominant strains of lactic flora in traditional Urfa cheese made from sheeps milk was performed using biochemical, phenotypic and genotypic methods. According to the results obtained, the percentage distributions of the lactic acid bacteria isolated were as follows: 48.95% Enterococcus spp., 40.55% Lactococcus spp., 9.10% Lactobacillus spp., 0.69% Streptococcus spp. and 0.69% Leuconostoc spp. The majority of lactococcal isolates showed an atypical phenotype of growing in the presence of 6.5% NaCl. Acidification and bacteriocin production were also determined for each isolate. Four strains showed bacteriocin activity.

Production of a whey-based functional beverage supplemented with soy isoflavones and phytosterols

Reconstituted whey beverages were prepared from whey powder by adding either soy isoflavones or phytosterols as functional compounds (at levels of 0%, 0.25%, 0.50% or 1.0% w/v) and probiotic bacteria (Lactobacillus acidophilus LA-5 or Lactobacillus casei LBC-81). The addition of nutraceuticals did not change the basic composition of the products. However, a time-dependent increase in sedimentation/phase separation and acidity of fermented functional beverages was observed. Samples supplemented with phytosterols were more preferred by the panel group than the samples supplemented with isoflavones, and no considerable differences were noted between the control and phytosterol-added samples in terms of overall perception.

NATURAL ANTI-MICROBIAL SYSTEMS | Lactoperoxidase and Lactoferrin

The preservation of raw milk by activating natural antimicrobial systems of milk offers practical advantages in regions where storage and transportation of raw milk under cold chain is not practical. The lactoperoxidase system and lactoferrin are the major antimicrobial systems of milk. These antimicrobial proteins inhibit not only the growth of undesired bacteria in milk but also they may affect the functionality of milk components. This chapter deals with the mode of action of lactoperoxidase system and lactoferrin in milk and their effects on milk products.

CHEESE | Microflora of White-Brined Cheeses

The conversion of milk into cheese and storage of the product in brine have been practiced around the world for thousands of years. These processes provide a practical means for preserving milk nutrients in a form that can be stored safely for extended periods of time at high temperatures. The microflora of the white-brined cheeses shows variations depending on the ripening conditions. This article deals with the microbiology of white-brined cheeses, including starter and nonstarter lactic acid bacteria and contaminants.