Cheese flavour formation by amino acid catabolism

doi:10.1016/S0958-6946(01)00049-8

International Dairy Journal

Volume 11, Issues 4–7, 11 July 2001, Pages 185-201

https://doi.org/10.1016/S0958-6946(01)00049-8 Get rights and content

Abstract

Amino acid catabolism is a major process for flavour formation in cheese. The ability of lactic acid bacteria (LAB) and other cheese micro-organisms to degrade amino acids to aroma compounds is highly strain dependent. Generally, amino acid catabolism proceeds by 2 different pathways. The first one, mainly observed for methionine, is initiated by elimination reaction and leads to major sulphur aroma compounds. The second pathway is generally initiated by a transamination reaction and is the main pathway for degradation of all amino acids by LAB. The resulting α-keto acids are then degraded to various aroma compounds via 1 or 2 additional steps. The lactococcal enzymes initiating both pathways have been well characterised, and their importance in the formation of aroma compounds has been demonstrated by using isogenic strains lacking each enzyme. From the new knowledge several applications have been successfully developed, especially for intensifying or diversifying cheese flavour by controlling amino acid transamination.

Introduction

Accelerating or diversifying flavour development in cheese is of major economical interest since final flavour of cheeses partly determines consumer choice and because flavour development is a time consuming and expensive process that is still not well mastered. Flavour formation occurs during cheese ripening. It is a complex process in which three major catabolic pathways are involved: glycolysis, lipolysis and proteolysis. Proteolysis was supposed to be rate limiting in the maturation of many cheeses, especially in semi-hard cheeses, and hence has been the focus of most research on the acceleration of ripening. However, recent results show that enhancing the free amino acid release by intensifying peptidolysis by lactic acid bacteria or adding free amino acids did not affect aroma formation in cheese (Christensen, Johnson, & Steele, 1995; Wallace & Fox, 1997), suggesting that the rate-limiting factor was not the release of free amino acids but the conversion of amino acids to aroma compounds.

Therefore, over the past five years, several research groups have focused on amino acid catabolism by cheese micro-organisms, especially by lactic acid bacteria and Brevibacterium linens, which is used as surface flora in many cheeses. These studies have provided new insights into amino acid catabolism, which offer new prospects for controlling aroma formation in cheese at the level of amino acid catabolism. In this review, firstly we will examine the importance of amino acid catabolism in flavour formation in cheese and the ability of cheese micro-organisms to generate aroma compounds from amino acids. Then we will review new knowledge on the enzymes and metabolic pathways involved in the conversion of amino acids to aroma compounds in cheese micro-organisms and we will finish by looking at some examples of controlling aroma formation in cheese at the level of amino acid catabolism.

Section snippets

Cheese aroma compounds resulting from amino acid degradation

Many studies have used GC/MS to analyse the aroma of cheeses. However this method measures all the volatile compounds while only a small fraction of volatiles are odour-active. In order to identify the odour-important compounds in cheese, analytical methods that combine gas chromatography and olfactometry have been developed. Recently, by using these methods the potent odorants of various cheeses have been identified (Table 1). Aroma profiles of Cheddar (Christensen & Reineccius, 1995; Milo &

Ability of cheese micro-organisms to produce aroma compounds from amino acids

A number of different LAB and other cheese micro-organisms have been evaluated for their ability to degrade amino acids to aroma compounds. The ability has been determined by incubating resting cells or cellular extracts in cheese models or in synthetic media containing casein or free amino acids and analysing products formed either by GC/MS or by HPLC. Many cheese micro-organisms, including lactic acid bacteria (LAB), coryneform bacteria, yeasts and Geotrichum candidum, are capable of

Catabolic pathways involved in amino acid conversion to aroma compounds

The enzymatic reactions involved in amino acid conversion to aroma compounds by cheese micro-organisms remain only partially characterised. They had been partly studied in yeast, Brevibacterium linens and some LAB but, over the past five years, knowledge was detailed especially in L. lactis and in some other LAB, and several enzymes involved in these reactions have been biochemically and genetically characterised. Regulation of gene expression has also been partially studied.

Generally, amino

Intensification and diversification of cheese aroma formation by controlling amino acid catabolism

New knowledge on amino acid catabolism by cheese micro-organisms has offered new insights into controlling aroma formation at the level of amino acid catabolism. Especially, control at the level of the transamination and elimination reactions has been evaluated to intensify or diversify aroma formation in semihard cheese.

Conclusion

Controlling amino acid catabolism by cheese micro-organisms appears to be a promising way to control aroma formation in cheese. Indeed, amino acid catabolism leads to different compounds with various aromas, which are major aroma compounds in most cheeses. Moreover, we have seen that intensifying amino acid catabolism results in a clear enhancement of cheese aroma.

While numerous enzymatic and non-enzymatic reactions are involved in the conversion of amino acids to aroma compounds, only a few of

Acknowledgements

The authors would like to thank their colleagues Anne Thierry, Pascal Bonnarme, Carmen Pelaez, Jean Banks and Alan Williams for communicating results prior to publication. We also thank A.-M. Wall (INRA Translation Unit, Jouy-en-Josas, France) for revising the English version of the manuscript and J.-C. Gripon for critical reading of the manuscript.

The work on amino acid catabolism conducted in our laboratory was supported in part by the EC FAIR contract CT97-3173 and TMR grant ERB 4001

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Cheese flavour formation by amino acid catabolism

Abstract

Introduction

Section snippets

Cheese aroma compounds resulting from amino acid degradation

Ability of cheese micro-organisms to produce aroma compounds from amino acids

Catabolic pathways involved in amino acid conversion to aroma compounds

Intensification and diversification of cheese aroma formation by controlling amino acid catabolism

Conclusion

Acknowledgements

International Dairy Journal

International Dairy Journal

Journal of Dairy Science

Lebensmittel-Wissenschaft und-Technologie

Enzyme Microbiological Technology

International Dairy Journal

International Dairy Journal

International Dairy Journal

The Journal of Biological Chemistry

Journal of Dairy Science

Cell

Journal of Dairy Science

Journal of Dairy Science

Lebensmittel Wissenschaft und Technologie

The Journal of Biological Chemistry

International Dairy Journal

FEMS Microbiology Letters

Gene

Gene

International Dairy Journal

Journal of Dairy Science

Journal of Dairy Science

Maltigenes. Journal of Dairy Science

Journal of Dairy Sciences

Lebensmittel Wissenschaft und Technologie

Journal of Biological Chemistry

International Dairy Journal

Archives of Biochemistry and Biophysics

FEMS Microbiology Letters

Methods in Enzymology

Biochimica et Biophysica Acta

Purification and characterization of cystathionine β-lyase from Lactococcus lactis subsp. cremoris B78 and its possible role in flavor development in cheese

Applied and Environmental Microbiology

Perfume and flavor chemicals (aroma chemicals)

Production of volatile compounds related to the flavor of foods from the Strecker degradation of dl-methionine

Journal of the Science of Food and Agriculture

Amino acid degradation by anaerobic bacteria

Annual Review of Biochemistry

Production of sulfur flavors by ten strains of Geotrichum candidum

Applied and Environmental Microbiology

NAD+-dependent d-2-hydroxyisocaproate dehydrogenase of Lactobacillus delbrueckii subsp. bulgaricus. Gene cloning and enzyme characterization

European Journal of Biochemistry

The flavor of Swiss cheese

Production de composés soufrés volatils par des Micrococcaceae et des bactéries corynéformes d’origine fromagère

Le Lait

Low-redundancy sequencing of the entire Lactococcus lactis IL1403 genome

Antonie Van Leeuwenhoek

Purification and characterization of cystathionine γ-lyase from Lactococus lactis subsp. cremoris SK11Possible role in flavor compound formation during cheese maturation

Applied and Environmental Microbiology

Aroma extract dilution analysis of aged Cheddar cheese

Journal of Food Science

Isolation and characterization of the l-methionine-γ-demethiolase from Brevibacterium linens NCDO 739

Science des Aliments

Concept matching technique for assessing importance of volatile compounds for Cheddar cheese aroma

Journal of Food Science

Role of BkdR, a transcriptional activator of the sigL-dependent isoleucine and valine degradation pathway in Bacillus subtilis

Journal of Bacteriology

Génétique moléculaire des lactate-déshydrogénases des bactéries lactiques

Le Lait

Conversion of methionine to thiols by Lactococci, Lactobacilli, and Brevibacteria

Applied and Environmental Microbiology

Purification and characterization of l-methionine γ-lyase from Brevibacterium linens BL2

Applied and Environmental Microbiology

The catabolism of branched-chain amino acids occurs via 2-oxoacid dehydrogenase in Saccharomyces cerevisiae

Journal of Genetic Microbiology

NAD⁺-dependent d-2-hydroxyisocaproate dehydrogenase of Lactobacillus delbrueckii subsp. bulgaricus. Gene cloning and enzyme characterization