Characterization of lactic acid bacteria strains on the basis of neutral volatile compounds produced in whey

Assessment of Different Levels of Blackcurrant Juice and Furcellaran on the Quality of Fermented Whey-Based Beverages Using Rheological and Mechanical Vibration Damping Techniques

In the current study, fermented whey-based beverage models with different levels of blackcurrant juice (0; 10; 20; 100% (w/w)) and furcellaran (0.25% and 0.50% (w/w)) were produced and evaluated. Physicochemical, rheological, mechanical vibration damping, and sensory analyses were performed. During fermentation (48 h), the values of pH, density, and total soluble solids decreased. On the other hand, the ethanol content during fermentation increased up to a final content in the range of 0.92-4.86% (v/v). The addition of furcellaran was effective in terms of sediment content decrease to a level of 0.25% (w/w). In general, the samples exhibited non-Newtonian pseudoplastic behaviour. The sensory analysis revealed that the sample with a composition of 20% (w/w) blackcurrant juice and 0.50% (w/w) furcellaran received the highest score.

Physical Characterization of a Novel Carrot Juice Whey-Enriched Beverage Fermented with Milk or Water Kefir Starter Cultures

The purpose of this work was to evaluate the selected physicochemical, rheological, and sensory properties of a new whey-enriched carrot juice beverage (carrot juice: whey ratios of 100:0; 95:5; 85:15; 75:25; 65:35) fermented with milk or water kefir starter cultures over a storage period of 21 days (at 4 ± 1 °C). In general, for all tested samples, the values of total soluble solids, pH, and density decreased with increasing storage time. In contrast, the values of ethanol, degree of fermentation, and total dissolved solids increased with the prolongation of the storage time. Furthermore, it was found that all the model samples exhibited pseudoplastic behavior. Based on the sensory analysis performed, samples containing 25% (w/w) whey were evaluated as the most acceptable. Last but not least, the present study can serve as a basis for optimizing the manufacturing technology of a novel fermented vegetable beverage enriched with whey.

Purification and Characterization of Novel Antihypertensive and Antioxidative Peptides From Whey Protein Fermentate: In Vitro, In Silico, and Molecular Interactions Studies

OBJECTIVE

The goal of this research was to purify and characterize the novel angiotensin-converting enzyme (ACE)-inhibitory and antioxidant peptides from fermented whey protein concentrate produced by Lactobacillus paracasei and Saccharomyces cerevisiae in a co-fermentation system.

METHOD

Whey protein fermented with lactic acid bacteria and yeast culture was analyzed for antioxidative, ACE inhibition, as well as anti-inflammatory activity followed by SDS-PAGE, isoelectric focusing, and 2-dimensional (2D) analysis. Anti-inflammatory activity of whey protein fermentate was also studied on the RAW 264.7 cell line. The bioactive peptides were separated from the whey protein fermentate using reverse-phase high-performance liquid chromatography (RP-HPLC) and reverse-phase liquid chromatography mass spectrometry (RPLC/MS), and thus identification and characterization of purified bioactive peptide was performed.

RESULTS

Whey protein fermentate samples' bioactivity was analyzed at specific time intervals at 12, 24, 36, and 48 hours at 37 °C for M11 and at 25 °C for WBS2A. The development settings (incubation time [12, 24, 36, and 48 hours) and inoculation rates [1.5%, 2.0%, and 2.5%]) were optimized for peptide synthesis via the o-phthaldialdehyde (OPA) method (proteolytic activity). Maximum proteolytic activity was observed at 37 °C for M11 (6.50 mg/mL) and at 25 °C for WBS2A (8.59 mg/mL) for 48 hours of incubation. Protein profiling was carried out using SDS-PAGE and 2D gel electrophoresis, in which Sodium dodecyl-sulfate (SDS) exhibited protein bands in the 10- to 55-kDa range, while 2D showed protein bands varying from 10 to 70 kDa. Every spot from 2D was digested by trypsin and identified by RPLC/MS. Protein fractionations (3- and 10-kDa permeates) were carried out employing RP-HPLC. Whey protein fermentate has anti-inflammatory action in RAW 264.7 macrophages that have been exposed to lipopolysaccharide. A molecular docking system was also used to investigate the interactions of peptides (AFLDSRTR, ILGAFIQIITFR) with human myeloperoxidase enzyme.

CONCLUSIONS

The antihypertensive and antioxidative peptides discovered from whey protein fermentate may be helpful in the design of pharmacologically active healthy ingredients in the upcoming years.

Yeast-driven whey biorefining to produce value-added aroma, flavor, and antioxidant compounds: technologies, challenges, and alternatives

Whey is a liquid residue generated during the production of cheese and yogurt. It has a pH between 3.9 and 5.6, and a high chemical oxygen demand (COD), from 60 to 80 g/L. Whey contains lactose, proteins, and minerals. Globally, approximately 50% of the whey generated is untreated and is released directly into the environment, which represents an environmental risk. To overcome whey management problems, conventional thermo-physical valorization treatments have been explored, which are complex, costly and energy-intensive. As an alternative, whey fermentation processes employing bacteria, fungi and yeast are economical and promising methods. Among them, yeast fermentation creates value-added products such as antimicrobials, biofuels, aromas, flavors, and antioxidants with no need for previous conditioning of the whey, such as hydrolysis of the lactose, prior to whey biorefining. The biorefining concept applied to whey is discussed using chemical and biological transformation pathways, showing their pluses and minuses, such as technical drawbacks. The main challenges and solutions for the production of fusel alcohols, specifically for 2-phenylethanol, are also discussed in this review.

Application of a Pivot Profile Variant Using CATA Questions in the Development of a Whey-Based Fermented Beverage

During the development of a food product, the application of rapid descriptive sensory methodologies is very useful to determine the influence of different variables on the sensory characteristics of the product under development. The Pivot profile (PP) and a variant of the technique that includes check-all-that-apply questions (PP + CATA) were used for the development of a milk drink fermented from demineralised sweet whey. Starting from a base formula of partially demineralised sweet whey and gelatin, nine samples were elaborated, to which various concentrations of commercial sucrose, modified cassava starch, and whole milk powder were added. Differences in sucrose content affected the sample texture and flavour and the modified starch was able to decrease the fluidity and increase the texture of creaminess and firmness, of the samples. The two applied sensory methodologies achieved good discrimination between the samples and very similar results, although the data analysis was clearly simplified in relation to the difficulty and time consumed in the PP + CATA variant.

A Multi-Omics Approach to Evaluate the Quality of Milk Whey Used in Ricotta Cheese Production

In the past, milk whey was only a by-product of cheese production, but currently, it has a high commercial value for use in the food industries. However, the regulation of whey management (i.e., storage and hygienic properties) has not been updated, and as a consequence, its microbiological quality is very challenging for food safety. The Next Generation Sequencing (NGS) technique was applied to several whey samples used for Ricotta production to evaluate the microbial community composition in depth using both RNA and DNA as templates for NGS library construction. Whey samples demonstrating a high microbial and aerobic spore load contained mostly Firmicutes; although variable, some samples contained a relevant amount of Gammaproteobacteria. Several lots of whey acquired as raw material for Ricotta production presented defective organoleptic properties. To define the volatile compounds in normal and defective whey samples, a headspace gas chromatography/mass spectrometry (GC/MS) analysis was conducted. The statistical analysis demonstrated that different microbial communities resulted from DNA or cDNA library sequencing, and distinguishable microbiota composed the communities contained in the organoleptic-defective whey samples.

Thermally-dried immobilized kefir on casein as starter culture in dried whey cheese production

The aim of the present study was to evaluate the use of thermally-dried immobilized kefir on casein as a starter culture for protein-enriched dried whey cheese. For comparison reasons, dried whey cheese with thermally-dried free kefir culture and with no starter culture were also produced. The effect of the nature of the culture, the ripening temperature and the ripening process on quality characteristics of the whey cheese was studied. The association of microbial groups during cheese maturation suggested repression of spoilage and protection from pathogens due to the thermally-dried kefir, as counts of coliforms, enterobacteria and staphylococci were significantly reduced in cheeses produced using thermally-dried kefir starter cultures. The effect of the starter culture on production of volatile compounds responsible for cheese flavor was also studied using the SPME GC/MS technique. Thermally-dried immobilized kefir starter culture resulted in an improved profile of aroma-related compounds. The preliminary sensory evaluation ascertained the soft, fine taste and the overall improved quality of cheese produced with the thermally-dried immobilized kefir. The potential of protein-based thermally-dried starter cultures in dairy products is finally highlighted and assessed.

Whey fermentation by thermophilic lactic acid bacteria: evolution of carbohydrates and protein content

Whey, a by-product of the cheese industry usually disposed as waste, is a source of biological and functional valuable proteins. The aim of this work was to evaluate the potentiality of three lactic acid bacteria strains to design a starter culture for developing functional whey-based drinks. Fermentations were performed at 37 and 42 degrees C for 24h in reconstituted whey powder (RW). Carbohydrates, organic acids and amino acids concentrations during fermentation were evaluated by RP-HPLC. Proteolytic activity was measured by the o-phthaldialdehyde test and hydrolysis of whey proteins was analyzed by Tricine SDS-PAGE. The studied strains grew well (2-3log cfu/ml) independently of the temperature used. Streptococcus thermophilus CRL 804 consumed 12% of the initial lactose concentration and produced the highest amount of lactic acid (45 mmol/l) at 24h. Lactobacillus delbrueckii subsp. bulgaricus CRL 454 was the most proteolytic (91 microg Leu/ml) strain and released the branched chain amino acids Leu and Val. In contrast, Lactobacillus acidophilus CRL 636 and S. thermophilus CRL 804 consumed most of the amino acids present in whey. The studied strains were able to degrade the major whey proteins, alpha-lactalbumin being degraded in a greater extent (2.2-3.4-fold) than beta-lactoglobulin. Two starter cultures were evaluated for their metabolic and proteolytic activities in RW. Both cultures acidified and reduced the lactose content in whey in a greater extent than the strains alone. The amino acid release was higher (86 microg/ml) for the starter SLb (strains CRL 804+CRL 454) than for SLa (strains CRL 804+CRL 636, 37 microg/ml). Regarding alpha-lactalbumin and beta-lactoglobulin degradation, no differences were observed as compared to the values obtained with the single cultures. The starter culture SLb showed high potential to be used for developing fermented whey-based beverages.

Relationships between sensorial characteristics and microbial dynamics in “Registered Designation of Origin” Salers cheese

Raw milk cheeses show a wide diversity of sensorial characteristics, largely determined by the microflora of raw milk. Microbial dynamics in Registered Designation of Origin (R.D.O.) Salers cheese was assessed by DNA and RNA SSCP analysis on nine cheeses. These cheeses showed considerable diversity both in microbial dynamics and sensorial characteristics. Relationships between the sensorial characteristics and the microbial dynamics were studied. A global consideration of bacterial dynamics demonstrated that other bacteria than lactic acid bacteria can play a role in the elaboration of sensorial characteristics. Indeed, high CG% Gram-positive bacteria can be involved. DNA data, as well as RNA data, appeared relevant to attempts to explain sensorial variance. Correlations between sensorial and microbial data were rather complex. Several microbial variables for DNA and RNA analyses, noted at different times of analysis, were correlated to each sensory variable. A global view of cheese microbial community proved to be insufficient in explaining the diversity of the sensorial qualities of R.D.O. Salers cheese.

PCR-DGGE fingerprints of microbial succession during a manufacture of traditional water buffalo mozzarella cheese

AIMS

To monitor the process and the starter effectiveness recording a series of fingerprints of the microbial diversity occurring at different steps of mozzarella cheese manufacture and to investigate the involvement of the natural starter to the achievement of the final product.

METHODS AND RESULTS

Samples of raw milk, natural whey culture (NWC) used as starter, curd after ripening and final product were collected during a mozzarella cheese manufacture. Total microbial DNA was directly extracted from the dairy samples as well as bulk colonies collected from the plates of appropriate culture media generally used for viable counts of mesophilic and thermophilic lactic acid bacteria (LAB) and used in polymerase chain reaction-denaturing gradient gel electrophoresis (PCR-DGGE) experiments. The analysis of the DGGE profiles showed a strong influence of the microflora of the NWC on the whole process because after the starter addition, the profile of all the dairy samples was identical to the one shown by the NWC. Simple indexes were calculated for the DGGE profiles to have an objective estimation of biodiversity and of technological importance of specific groups of organisms. LAB grown on Man Rogosa Sharp (MRS) and Rogosa agar at 30 degrees C showed high viable counts and the highest diversity in species indicating their importance in the cheese making, which had not been considered so far. Moreover, the NWC profiles were shown to be the most similar to the curd profile suggesting to be effective in manufacture.

CONCLUSIONS

The PCR-DGGE analysis showed that in premium quality manufacture the NWC used as starter had a strong influence on the microflora responsible for process development.

SIGNIFICANCE AND IMPACT OF THE STUDY

The molecular approach appeared to be valid as a tool to control process development, starter effectiveness and product identity as well as to rank cheese quality.

Relationships between flavoring capabilities, bacterial composition, and geographical origin of natural whey cultures used for traditional water-buffalo mozzarella cheese manufacture

Natural whey cultures (NWC) (n = 29) used for traditional water-buffalo Mozzarella cheese manufacture and arising from different geographical areas of production were characterized and grouped on the basis of their capability to develop neutral volatile compounds and according to their microbial diversity as revealed by molecular analysis. The flavoring properties of NWC were studied in dairy microcosms resembling the specific technological procedure used in the traditional water-buffalo Mozzarella cheese-making. Neutral volatile compounds were identified by high-resolution gas chromatography (HRGC)-mass spectrometry analysis while information on the microbial diversity occurring in the NWC was retrieved by PCR-denaturing gradient gel electrophoresis (DGGE) analysis of 16S rDNA after direct DNA extraction. Neoformation volatile substances (n = 27) were found; 23 were identified and some of them recognized as odor-conferring molecules. Eight different bands, referable to eight microbial species, were obtained by PCR-DGGE analysis of the NWC. Statistical analyses were applied to PCR-DGGE and HRGC data. Interestingly, the flavoring capabilities and the microbial diversity of the NWC proved to be closely linked and both related to the geographical origin of the NWC. These results suggested a possible use of the molecular characterization of the dairy products to support the traceability criteria of typical dairy products like water-buffalo Mozzarella cheese.