Inactivation of lactococcal aromatic aminotransferase prevents the formation of floral aroma compounds from aromatic amino acids in semi-hard cheese
The enzymatic conversion of aromatic amino acids to aroma compounds plays a role in the formation of an undesirable floral aroma in Cheddar-like cheeses. In lactococci, the first step of aromatic amino acid degradation is a transamination, catalysed by an aromatic aminotransferase (AraT). We observe...
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Published in | International dairy journal Vol. 9; no. 12; pp. 877 - 885 |
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Main Authors | , , , , , |
Format | Journal Article |
Language | English |
Published |
Oxford
Elsevier Ltd
01.01.1999
Elsevier Science |
Subjects | |
Online Access | Get full text |
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Summary: | The enzymatic conversion of aromatic amino acids to aroma compounds plays a role in the formation of an undesirable floral aroma in Cheddar-like cheeses. In lactococci, the first step of aromatic amino acid degradation is a transamination, catalysed by an aromatic aminotransferase (AraT). We observed previously that in vitro,
araT inactivation prevented degradation of aromatic amino acids and decreased degradation of Met and Leu. In this study we evaluated the effect of
araT inactivation in
Lactococcus lactis on flavour development in St. Paulin-type cheese. The degradation of amino acids was monitored by using radiolabelled amino acids and the volatile compounds formed were analysed by GC-MS. The development of cheese odour was also evaluated by sniffing. We confirmed that the availability of an
α-ketoacid acceptor for transamination is the first limiting factor for amino acid conversion to aroma compounds in cheese. In the presence of
α-ketoglutarate,
araT inactivation greatly prevented formation of floral aroma compounds from aromatic amino acids while it did not affect the formation of volatile aroma compounds from branched-chain amino acids and methionine. However, the sensory analysis by sniffing did not reveal any significant effect of the gene inactivation although the odour of cheese made with the mutant tended to be less floral than that of cheese made with the wild type strain. |
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Bibliography: | Q02 2000003125 ObjectType-Article-2 SourceType-Scholarly Journals-1 ObjectType-Feature-1 content type line 23 |
ISSN: | 0958-6946 1879-0143 |
DOI: | 10.1016/S0958-6946(00)00009-1 |