Effect of the activity levels of the added proteolytic enzyme mixture on free amino acids in ripening Ossau-Iraty cheese

Formation of Free Amino Acids and Bioactive Peptides During the Ripening of Bulgarian White Brined Cheeses

Bioactive peptides and free amino acids obtained from Bulgarian goat, sheep and cow white brined cheeses, produced with same starter culture, during ripening were evaluated. The concentration of total free amino acids was increasing in all tested cheeses in the first 30 days of ripening. In the next 30 days in sheep cheeses, the concentration increased as recorded for most of the amino acids. Amino acids with highest levels detected throughout the whole ripening period in goat, sheep and cow cheese types were leucine, phenylalanine, arginine, valine and lysine. MALDI-TOF analysis of evaluated cheeses resulted in detection of production of bioactive peptide derivates from milk proteins: 51 peptides in cow, 31 peptides in sheep and 22 peptides in goat cheeses. Peptide αs1-CN (f35-40) was found only in cow cheese. In cow cheese, higher intensity was detected for αs1-CN (f1-9) and β-CN (f194-203 and f203-219) peptides. In goat cheese was recorded αs1-CN peptides, and there was a tendency to increase the peptides released from β-CN, with the highest intensity of fragments αs1-CN (f1-9 and f24-30) and β-CN (f194-209 and f203-219). In sheep cheese, the recorded primarily peptides were αs1-CN and peptides released from β-CN. Different bioactive peptides, derivate from casein, were detected as follows: 6 peptides were ACE inhibitory peptides, 3 peptides were αS1-casokinins, 1 peptide was caseinophopeptide, 1 peptide was immunopeptide. Twelve bioactive peptides were recorded to be derivates from β-casein: 1 peptide was ACE peptide, 4 peptides were caseino-phosphopeptides, 1 peptide was immunopeptide, 1 peptide β-casokinin, 1 antibacterial peptide and 4 multifunctional peptides. Of peptides released by proteolysis of αS2-CN was found 1 bioactive peptide with antimicrobial activity. On our best knowledge, this paper contributes new data about free amino acids and bioactive peptides in the connection between type of milk and period for cheese ripening in the Bulgarian goat, sheep and cow white brined cheeses.

The Good, the Bad, and the Ugly: Tales of Mold-Ripened Cheese

The history of cheese manufacture is a "natural history" in which animals, microorganisms, and the environment interact to yield human food. Part of the fascination with cheese, both scientifically and culturally, stems from its ability to assume amazingly diverse flavors as a result of seemingly small details in preparation. In this review, we trace the roots of cheesemaking and its development by a variety of human cultures over centuries. Traditional cheesemakers observed empirically that certain environments and processes produced the best cheeses, unwittingly selecting for microorganisms with the best biochemical properties for developing desirable aromas and textures. The focus of this review is on the role of fungi in cheese ripening, with a particular emphasis on the yeast-like fungus Geotrichum candidum. Conditions that encourage the growth of problematic fungi such as Mucor and Scopulariopsis as well as Arachnida (cheese mites), and how such contaminants might be avoided, are discussed. Bethlehem cheese, a pressed, uncooked, semihard, Saint-Nectaire-type cheese manufactured in the United Sates without commercial strains of bacteria or fungi, was used as a model for the study of stable microbial succession during ripening in a natural environment. The appearance of fungi during a 60-day ripening period was documented using light and scanning electron microscopy, and it was shown to be remarkably reproducible and parallel to the course of ripening of authentic Saint-Nectaire cheese in the Auvergne region of France. Geotrichum candidum, Mucor, and Trichothecium roseum predominate the microbiotas of both cheese types. Geotrichum in particular was shown to have high diversity in different traditional cheese ripening environments, suggesting that traditional manufacturing techniques selected for particular fungi. This and other studies suggest that strain diversity arises in relation to the lore and history of the regions from which these types of cheeses arose.

Complete genome sequence of Corynebacterium variabile DSM 44702 isolated from the surface of smear-ripened cheeses and insights into cheese ripening and flavor generation

Background

Corynebacterium variabile is part of the complex microflora on the surface of smear-ripened cheeses and contributes to the development of flavor and textural properties during cheese ripening. Still little is known about the metabolic processes and microbial interactions during the production of smear-ripened cheeses. Therefore, the gene repertoire contributing to the lifestyle of the cheese isolate C. variabile DSM 44702 was deduced from the complete genome sequence to get a better understanding of this industrial process.

Results

The chromosome of C. variabile DSM 44702 is composed of 3, 433, 007 bp and contains 3, 071 protein-coding regions. A comparative analysis of this gene repertoire with that of other corynebacteria detected 1, 534 predicted genes to be specific for the cheese isolate. These genes might contribute to distinct metabolic capabilities of C. variabile, as several of them are associated with metabolic functions in cheese habitats by playing roles in the utilization of alternative carbon and sulphur sources, in amino acid metabolism, and fatty acid degradation. Relevant C. variabile genes confer the capability to catabolize gluconate, lactate, propionate, taurine, and gamma-aminobutyric acid and to utilize external caseins. In addition, C. variabile is equipped with several siderophore biosynthesis gene clusters for iron acquisition and an exceptional repertoire of AraC-regulated iron uptake systems. Moreover, C. variabile can produce acetoin, butanediol, and methanethiol, which are important flavor compounds in smear-ripened cheeses.

Conclusions

The genome sequence of C. variabile provides detailed insights into the distinct metabolic features of this bacterium, implying a strong adaption to the iron-depleted cheese surface habitat. By combining in silico data obtained from the genome annotation with previous experimental knowledge, occasional observations on genes that are involved in the complex metabolic capacity of C. variabile were integrated into a global view on the lifestyle of this species.

A comparative study of several HPLC methods for determining free amino acid profiles in honey

A study of the viability of three derivatizing reagents for obtaining amino acid profiles in honey through high performance liquid chromatography (HPLC) is presented. A method using diode array detection based on a reaction with diethyl ethoxymethylene malonate (DEMM) and two other methods using fluorescence detection based on derivatization with fluorenylmethyl chloroformate (FMOC-Cl) and 6-aminoquinolyl-N-hydroxysuccinimidyl carbamate (AQC) have been developed. The three methods yield detection limits close to the ppb level, but vary in relation to other analytical characteristics. The use of methyl chloroformate derivatives allows the profile to be obtained with the greatest sensitivity within a short time frame. On applying such methods to honey samples of diverse botanical origin, we observe that the proline values obtained are always lower than those found using the official spectrophotometric method, thereby underlining the advisability of using HPLC methods to reduce uncertainty in these results.