Manufacture Of Fermented Milk Research Articles

Effects of Ultra-High-Pressure Jet Processing on Casein Structure and Curdling Properties of Skimmed Bovine Milk

Ultra-high-pressure jet processing (UHPJ) is a new non-thermal processing technique that can be employed for the homogenization and the sterilization of dairy products. However, the effects on dairy products are unknown when using UHPJ for homogenization and sterilization. Thus, this study aimed to investigate the effects of UHPJ on the sensory and curdling properties of skimmed milk and the casein structure in skimmed milk. Skimmed bovine milk was treated with UHPJ using different pressures (100, 150, 200, 250, 300 MPa) and casein was extracted by isoelectric precipitation. Subsequently, the average particle size, Zeta potential, contents of free sulfhydryl and disulfide bonds, secondary structure, and surface micromorphology were all used as evaluation indicators to explore the effects of UHPJ on the structure of casein. The results showed that with an increase of pressure, the free sulfhydryl group content changed irregularly, while the disulfide bond content increased from 1.085 to 3.0944 μmol/g. The content of α-helix and random coil in the casein decreased, while the β-sheet content increased at 100, 150, 200 MPa pressure. However, treatment with higher pressures of 250 and 300 MPa had the opposite effect. The average particle size of the casein micelles first decreased to 167.47 nm and then increased up to 174.63 nm; the absolute value of Zeta potential decreased from 28.33 to 23.77 mV. Scanning electron microscopy analysis revealed that the casein micelles had fractured into flat, loose, porous structures under pressure instead of into large clusters. After being ultra-high-pressure jet-processed, the sensory properties of skimmed milk and its fermented curd were analyzed concurrently. The results demonstrated that UHPJ could alter the viscosity and color of skimmed milk, shortening curdling time from 4.5 h to 2.67 h, and that the texture of the curd fermented with this skimmed milk could be improved to varying degrees by changing the structure of casein. Thus, UHPJ has a promising application in the manufacture of fermented milk due to its ability to enhance the curdling efficiency of skimmed milk and improve the texture of fermented milk.

Capsular Exopolysaccharides from Two Streptococcus thermophilus Strains Differ in Their Moisture Sorption Behavior.

Streptococcus thermophilus is a species frequently used in the manufacture of fermented milk. Apart from acid production, some strains additionally synthesize exopolysaccharides (EPS) which contribute to texture improvement and syneresis reduction, both being attributable to the EPS's high water binding capacity. There are two different types of EPS that may be produced, namely free exopolysaccharides (fEPS) which are secreted into the medium, and capsular EPS (cEPS) which remain attached to the bacterial cell wall. This study aims to analyze their individual contribution to techno-functional properties of fermented milk by determining the moisture sorption behavior of isolated fEPS and cell-attached cEPS from two S. thermophilus strains separately: ST-1G, a producer of non-ropy fEPS and cEPS, and ST-2E, a producer of ropy fEPS and cEPS. Differences in moisture load and sorption kinetics, determined for the first time for microbial EPS, were related to structural and macromolecular properties. The observed data are discussed by using previously published data on the physical properties of stirred fermented milk produced with these two strains. ST-1G EPS showed a higher cEPS fraction, a higher moisture load and slower moisture desorption than EPS produced by ST-2E, thus contributing to lower syneresis in fermented milk. For ST-2E, higher gel viscosity was related to a higher intrinsic viscosity and molecular mass of the ropy fEPS. Both strains produced complex EPS or EPS mixtures with clearly different molecular structures.

Single and Co-Cultures of Proteolytic Lactic Acid Bacteria in the Manufacture of Fermented Milk with High ACE Inhibitory and Antioxidant Activities

In this study, single and co-cultures of proteolytic Lactobacillus delberueckii subsp. bulgaricus ORT2, Limosilactobacillus reuteri SRM2 and Lactococcus lactis subsp. lactis BRM3 isolated from different raw milk samples were applied as starter cultures to manufacture functional fermented milks. Peptide extracts from fermented milk samples were evaluated after fermentation and 7 days of cold storage for proteolytic, angiotensin-converting enzyme (ACE) inhibitory and antioxidant activity by different methods including 2, 2′-diphenyl-1-picrylhydrazyl (DPPH), ferric-reducing antioxidant power (FRAP), OH-radical scavenging, and total antioxidant (molybdate-reducing activity). The highest proteolysis was found in milk fermented by co-cultures of three strains. Fermentation with the mentioned bacteria increased ACE inhibitory and antioxidant activity of the final products which were dependent on peptide concentration. The crude peptide extract obtained from fermented milk with triple co-culture showed the highest ACE inhibitory activity (IC50 = 0.61 mg/mL) which was reduced after 7 days of cold storage (IC50 = 0.78 mg/mL). Similar concentration-dependent activities were found in antioxidant activity at different antioxidant assays. Overall, high proteolytic activity resulted in increased ACE inhibitory and antioxidant activities, but the highest activity was not necessarily found for the samples with the highest proteolytic activity. The results of this study suggest the potential of using co-cultures of L. delberueckii subsp. bulgaricus, L. reuteri and L. lactis subsp. Lactis to manufacture antihypertensive fermented milk.

Milk Fermentation by Lacticaseibacillus rhamnosus GG and Streptococcus thermophilus SY-102: Proteolytic Profile and ACE-Inhibitory Activity

Health benefits of probiotics and production of inhibitors of angiotensin converting enzyme (ACE) released during milk fermentation are well known. That is why in this investigation the proteolytic profile and ACE inhibitory capacity of peptide fractions from protein hydrolysis of milk during fermentation processes was analyzed. Milk fermentation was carried out inoculating 106 CFU of L. rhamnosus GG, S. thermophilus SY-102 and with both bacteria. The proteolytic profile was determined using: TNBS, SDS-PAGE and SEC-HPLC techniques. In vitro ACE inhibition capacity was measured. The pH of 4.5 was reached at 56 h when the milk was fermented with L. rhamnosus, at 12 h with S. thermophillus and at 41 h in the co-culture. Production of free amino groups corresponded with the profile of low molecular weight peptides observed by SDS-PAGE and SEC-HPLC. Co-culture fermentation showed both the highest concentration of low molecular weight peptides and the ACE inhibitory activity (>80%). Results indicated that the combination of lactic cultures could be useful in manufacture of fermented milk with an added value that goes beyond basic nutrition, such as the production of ACE-inhibitory peptides.

JProbiotic activity of lactic acid bacteria isolated from several commercial fermentation product in Medan, North Sumatera

Lactic Acid Bacteria (BAL) are bacteria that have been used to produce food, which is in the manufacture of fermented milk. In addition, LAB can also be used as a probiotic agent. This study was conducted to look at the resistance of antibiotics, acids and bile salts as a criterion as probiotics. Samples were taken from 6 commercial fermentation products containing BAL. The isolation results obtained all samples had a number of BAL 106 colonies so that according to the probiotic criteria with the highest number of colonies were Y samples. Test results on 6 types of antibiotics (gentamicin, amoxicillin, ofloxacin, erythromycin, cefotaxime, oxacillin) U samples were resistant to all antibiotics and then product Y. In the test of acid and bile salts, only U samples were taken as the most resistant to antibiotic samples. The test results found that U samples were resistant to acid and bile salts with 100% viability. Keywords: lactic acid bacteria; probiotics; antibiotics; fermented products.22,7.

Content of sugar, organic acids and ethanol in fermented milk beverages obtained with different types of kombucha inoculum

The aim of this study was to examine the influence of different types and concentration of kombucha inoculum on content of sugar, organic acids and ethanol in the fermented beverages produced from milk of 0.9% fat content. Three different kombucha inoculums, cultivated on black tea with addition of sucrose: standard inoculum - 10% (w/w) and 15% (w/w), concentrated by microfiltration- 10% (w/w) and 15% (w/w), and concentrated by evaporation - 1.5% (w/w) and 3.0% (w/w), were applied in the manufacture of fermented milk. Contents of lactose, galactose, glucose, fructose, organic acids, and ethanol in the kombuha fermented milk beverages were determined by the enzyme tests. It was found that the lactose content varied from 3.30 to 4.0 g/100g. All samples showed higher content glucose than fructose. The content of L-lactic acid in the samples ranged from 0.4 to 0.7 g/100g, while significantly lower level of D-lactic and acetic acid were determined in all samples of kombucha fermented milk (<0.06g/100g).

Production and separation of dipeptidyl peptidase IV from Lactococcus lactis: scale up for industrial production

Lactococcus lactis spp. lactis and Lactococcus lactis spp. cremoris are widely used in the manufacture of fermented milk. These strains were compared for production of Dipeptidyl Peptidase IV (DPP IV) enzyme in terms of enzyme activity, specific growth rates and productivity. Lactococcus lactis spp. lactis was produced in 3L bioreactor and scaled up to 30 and 150L stirred tank bioreactors, and the enzyme activities were found as 110, 110 and 122mUmL(-1), respectively. After 8h of production, separation steps were performed. While purification fold was 127 and yield was 2.69%, the molecular weight of the enzyme was estimated as 68kDa. Partially purified enzyme was enteric coated with capsules and a 95.5% of DPP IV enzyme passed into the artificial intestine. Results show that production of DPP IV enzyme by Lactococcus lactis spp. lactis strain in submerged culture is comparable with the productions by commercial strains, mostly Aspergillus, in solid state fermentations based on productivity.

Isolation and identification of high viscosity-producing lactic acid bacteria from a traditional fermented milk in Xinjiang and its role in fermentation process

Forty-four lactic acid bacteria (LAB) isolated from traditional Sayram ropy fermented milk (SRFM) in southern Xinjiang of China. Further two strains were selected based on their high viscosity-producing activity. Based on the API 50 CHL strip and 16S rDNA sequence analysis, strain MB 2-1 was a Gram-positive, rod-shaped Lactobacillus helveticus and strain MB 5-1 was identified as Streptococcus thermophilus. Both the two LAB strains were grown in the milk fermentations for pure and mixed cultures and were evaluated for their growth, acidification properties, EPS production, and ability to increase the apparent viscosity of fermented milk, respectively. L. helveticus MB 2-1 displayed a high increasing in viable cell counts and the acidifying capacity in pure cultures, whereas the relatively high EPS production and viscosity-producing capacity detected in pure culture with S. thermophilus MB 5-1 as starter culture. In addition, the mixed culture of the two strains showed a higher cell growth, EPS production, and high viscosity-producing capacity at 37 °C. Values of apparent viscosity were 4.03- and 2.41-fold higher in mixed culture than for pure cultures of L. helveticus MB 2-1 and S. thermophilus MB 5-1, respectively. There was a positive correlation between the viscosity and high molecular weight EPS production with pure and mixed cultures. Our data showed two strains combination, with high viscosity-producing and acidifying capacity, can be used in mixed cultures for the manufacture of fermented milk with improved functional properties.

Effect of inactivation of stress response regulators on the growth and survival of Streptococcus thermophilus Sfi39

Streptococcus thermophilus is an important dairy starter used for the manufacture of fermented milks and cheeses. As for many other lactic acid bacteria, its survival during propagation and preservation of starter cultures and its performance in dairy fermentations are significantly affected by its ability to cope with many environmental stresses. This, in turn, is dependent on the expression of a several genes, which is often controlled by negative response regulators, and has complex relationships with the control of metabolism. In this paper we describe the effect of growth phase, adaptation and inactivation of genes for stress response regulators ( hrcA, ctsR and rr01) on the growth, acid production and stress resistance and intracellular protein patterns in the yoghurt strain S. thermophilus Sfi39. Inactivation of stress response regulators significantly affected growth, acid production in milk and stress tolerance. Although mutants showed an increased resistance during the exponential phase compared to the wild type strain, the effect of the mutations was complex and in some cases mutants were unable to mount an acid- or heat-shock response after exposure to mild heat and acid stresses. Significant differences in intracellular protein patterns analyzed by SDS-PAGE and 2-DE/mass spectrometry were found as a function of growth phase, adaptation and mutation, but a detailed transcriptomic and proteomic study would be needed to provide a mechanistic interpretation of the effect of the mutations and to identify a strategy for the construction of food-grade mutants with improved growth and performances.

Characterization of bifidobacteria as starters in fermented milk containing raffinose family of oligosaccharides from lupin as prebiotic

The characterization of six bifidobacteria strains used as starters in the manufacture of fermented milk, containing the raffinose family of oligosaccharides (RFOs) as prebiotics, was carried out by applying in vitro methodologies. Selection criteria were the specific growth rate ( μ), generation time ( T g), titratable acidity in milk, and enzymatic activities. Strain growth and acidification rate were determined in milk with and without 2% RFOs. Different growth rates, acidification rates and enzymatic patterns were observed among tested bifidobacterial strains. Bifidobacteria with higher levels of α-galactosidase activity showed growth and acidification rate enhancement when RFOs were added compared with lactose as sole carbon source. Based on the results, Bifidobacterium lactis Bb-12 was selected for further investigation as it possessed the enzymes required to enhance growth and metabolic activity in the presence of RFOs from lupins.

Uses of mares’ milk in manufacture of fermented milks

Abstract Eight fermented milks (FM) were manufactured from mares’ milk by using: mares’ milk alone (FM1); a blend of mares’ milk and cows’ milk (FM2) or sheeps’ milk (FM3), at respective weight ratio of 70 to 30; mares’ milk fortified with sodium (Na)-caseinate (FM4) added at a level of 15 g kg −1 ; pectin (FM5) added at a level of 2.5 g kg −1 ; Na-caseinate and pectin (FM6); Na-caseinate, pectin and sucrose added at a level of 100 g kg −1 (FM7); or Na-caseinate, pectin and threonine added at a level of 0.8 g kg −1 (FM8). Lactobacillus delbrueckii subsp. bulgaricus and Streptococcus thermophilus were used as starter cultures (ca. 9.0 and 7.0 log cfu g −1 , respectively) by inoculating (10 g kg −1 ) the milk at 42°C. Fermentation was allowed until the pH reached 4.2 (190–380 min). Data of acidification rate were modelled with the Gompertz equation. The concentration of lactic acid in the fermented milks ranged from 100 to 135 m m ; it was highest in all FMs which contained Na-caseinate. The highest concentration of acetaldehyde (0.45 m m ) was found in FM8. Rheological measurements showed that FM7 had the highest consistency coefficient (k). There was a correlation between the sensory consistency scores and the consistency index obtained from the rheological measurements. The addition of sucrose, pectin and, especially, threonine were positively correlated with a rather good taste. FM1 had unacceptable apparent viscosity and received the lowest scores for appearance, consistency and taste.

Survival of salmonellae in bio‐yoghurt

Many yoghurt‐like products are sold with pH values of 4.5–4.6, and a potential pathogen, Salmonella infantis, was shown to survive for 10 days in typical commercial samples of ‘bio‐yoghurt’. Another servovar, Salmonella hadar, could not be detected after 48 h in similar products. The need to avoid contamination during the manufacture of fermented milks with pH values above those traditionally associated with yoghurt (~4.0) is stressed.

Food-derived bioactive peptides--opportunities for designing future foods.

Dietary proteins are known to carry a wide range of nutritional, functional and biological properties. Nutritionally, the proteins are a source of energy and amino acids, which are essential for growth and maintenance. Functionally, the proteins contribute to the physicochemical and sensory properties of various protein-rich foods. Furthermore, many dietary proteins possess specific biological properties which make these components potential ingredients of functional or health-promoting foods. Many of these properties are attributed to physiologically active peptides encrypted in protein molecules. Particularly rich sources of such peptides are milk and egg, but they are also found in meat of various kinds as well as many plants. These peptides are inactive within the sequence of parent protein and can be released during gastrointestinal digestion or food processing. Depending on the amino acid sequence, these peptides may exert a number of different activities in vivo, affecting, e.g., the cardiovascular, endocrine, immune and nervous systems in addition to nutrient utilization. There is increasing commercial interest in the production of bioactive peptides from various sources. Industrial-scale production of such peptides is, however, hampered by the lack of suitable technologies. Bioactive peptides can also be produced from milk proteins through fermentation of milk, by starters employed in the manufacture of fermented milks or cheese. In particular, antihypertensive peptides have been identified in fermented milk, whey and ripened cheese. A few of these peptides have been commercialised in the form of fermented milks. There is a need to develop technologies which retain or even enhance the activity of bioactive peptides in food systems. Also, it is essential to study the optimum utilization of such peptides during passage through the gastrointestinal tract.

Role of exopolysaccharides produced by Lactococcus lactis subsp. cremoris on the viscosity of fermented milks

Lactic acid bacteria strains that produce exopolysaccharide (EPS) are employed in the manufacture of fermented milk to improve its texture and viscosity. No clear correlation has been found between EPS concentration and the viscosity of the fermented milk. It is supposed that the molecular characteristics, i.e. radius of gyration and molar mass, of these biopolymers play a part. The subject of this study was to clarify whether the viscosifying properties of EPS in aqueous solution can be related to the viscosity of fermented milk products. Therefore, we aimed at relating the molecular characteristics of EPSs produced by several strains of Lactococcus lactis subsp. cremoris in milk at three incubation temperatures to the viscosity of the fermented products. For a given EPS concentration, a positive correlation between the EPS-viscosifying parameters (intrinsic viscosity, Kuhn segments length and thickening efficiency) and the Posthumus viscosity of fermented milks was found.

Studies on the Selection of Lactic Acid Bacteria for the Manufacture of Fermented Milk with High Desmutagenic Activity

Studies on the Selection of Lactic Acid Bacteria for the Manufacture of Fermented Milk with High Desmutagenic Activity

Preservation of Kefir Grains, a Comparative Study

The microflora of kefir grains of household origin was isolated and identified. At least two lactococci, two lactobacilli, two yeast and one mould were detected. Different methods for kefir grain preservation were studied. Metabolic activity of grains preserved frozen at −20 °C and −80 °C and grains stored at 4 °C was evaluated. Grains stored at −20 °C and −80 °C maintained their microflora and increased their weights at a rate comparable to that found with nonstored grains. Fermented milk obtained with the grains stored at −20 °C and −80 °C showed the same microflora, rheological behaviour, acidity and carbon dioxide content as fermented milk obtained with nonstored grains. Grains stored at 4 °C did not increase their weight and the product obtained did not have the acidity and viscosity of the standard product. Storage at −20 °C is a good method to preserve kefir grains for household manufacture of fermented milk.

5527505 Process for the manufacture of fermented milk

5527505 Process for the manufacture of fermented milk

Influence of mastitis on growth of starter organisms used for the manufacture of fermented milks.

The effect of milk containing increased somatic cells on the starter organisms Streptococcus thermophilus, Lactobacillus bulgaricus and L. acidophilus was examined. Increased somatic cell count resulted in stimulation of Str. thermophilus owing to increased proteolysis, but inhibition of L. acidophilus as a consequence of increased phagocytic activity of the polymorphonuclear leucocytes

Studies on the Quality of Fermented Milk

This paper deals with the improvement of the previously proposed procedure which was based on the application of symbiosis among lactic streptococci for the manufacture of fermented milk by Lact. bulgaricus.Mother starter for preparing curd was shown to be most suitable when Lact. bulgaricus strain was inoculated in Leichimanii medium and then transplanted to a skim milk solution and cultured for 24 hours at 37°C.The manufacture of fermented milk was shown to be most effective when the curd was prepared by mixing a 24 hour culture and a 48 hour culture in 1:1 ratio.