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The umami of vegetables

(tomato and tomato sauce)

Mr.Heston Blumenthal
Mr.Heston Blumenthal

Tomatoes contain high levels of the umami provider glutamic acid, and as the fruit ripens these levels increase (→umami rich foods section). There are many recipes that use bright red, ripe tomatoes to make a simple tomato sauce by adding onion and herbs to cooked tomatoes. Most of these recipes, however, involve removing the skin of the tomatoes with boiling water and removing the seeds.

However, Heston Blumenthal, owner and chef at the triple Michelin starred Fat Duck restaurant in the UK (read more about Heston at The New Frontiers of Taste event in UK ), began to question this practice of removing the seeds, and wrote an academic paper on the subject in conjunction with scientists at the food sciences faculty of Reading University in the UK. Here, we outline the results of his research.


Measuring glutamic acid levels in the outer and inner parts of the tomato

Sample:
Fourteen types of tomato including four types of salad tomato, six types of baby tomato, three types of plum tomato and one type of beef tomato were analysed. In all cases, the skins were removed in boiling water, the outer and inner (including seeds) portions were separated and each chopped up.

 

Analysis:
1) Levels of free amino acids, nucleotides etc. were measured.
2) Panellists carried out an appraisal of the taste and flavour profile of the outer and inner part of the tomatoes.

 

Levels of glutamic acid found in the outer and inner parts of the tomato Levels of glutamic acid found in the outer and inner parts of the tomato
Click to view diagram

 

Findings:
1) The above graph shows the results of the analysis of the umami substance glutamic acid. It is clear that the inner part of the tomato has higher levels of glutamic acid.
2) The panellists decided that the inner part of the tomato had a stronger umami aftertaste than the outer part (5% significant difference).

Tomato sauce is frequently served with meat or fish, which contain the umami providing nucleotide inosinic acid. Thus, the glutamic acid of the tomato combines with the inosinic acid to create a synergistic umami effect, heightening the umami taste sensation dramatically. In this context, it would appear to be even more important to include the inner part of the tomato in sauces. Thus, when making your own tomato sauce, be sure not to throw the seeds away, and make full use of them!


(*)J. Agric. Food Chem., 55 (14), 5776 -5780, 2007. Differences in Glutamic Acid and 5'-Ribonucleotide Contents between Flesh and Pulp of Tomatoes and the Relationship with Umami Taste 

Maria-Jose Oruna-Concha, Lisa Methven, Heston Blumenthal, Christopher Young, and Donald S. Mottram* Department of Food Biosciences, University of Reading, Whiteknights, Reading RG6 6AP, United Kingdom, and The Fat Duck Restaurant, Bray, Berkshire SL6 2AQ, United Kingdom


Mr Heston Blumenthal joined the BBC TV programme "Search of Perfection 2", in which he unlocked the secret to a umami-rich tomato sauce - leaving in the seeds of the tomato.