Natural food and beverage flavour enhancers - Natural Food Additives, Ingredients and Flavourings - page 85

Brevibacterium fl avum - all gram-positive coryneform bacterium (Sano 2009).
The glutamic acid is then crystallised by acidifi cation and converted into
monosodium glutamate by washing the crystallised material with sodium
hydroxide. Impurities are removed by passing through active carbon fi lters and
fi nally the MSG solution is heated to re-crystallise it before packing. MSG
produced by fermentation in this way is classifi ed as natural by the European
Union; however it still requires an E number listing and, hence, natural sources of
glutamate are commercially signifi cant for the production of clean label products.
There remains controversy over the use of MSG in food. It has been evaluated
by both the Joint FAO/WHO Expert Committee on Food Additives (JECFA) and
by European Commission's Scientifi c Committee for Food (SCF). Both
committees established the Acceptable Daily Intake (ADI) to be 'not specifi ed' on
the basis of the data available and the fact that there is a large intake of glutamate
in a normal diet (COT 2006).
There are two main arguments put forward against MSG - the fi rst against the
glutamate and the second against the sodium. Regarding the glutamate, the view
of the UK's Committee on Toxicity (COT) is that there is unlikely to be a hazard
at normal dose levels. Glutamate is a neuroactive compound and can cross the
blood-brain barrier and placenta; however, it is present in normal blood and brain,
and the brain levels are well controlled by active physiological regulation (COT
2006). In fact levels in the brain are normally higher than in the plasma
(10 000-12 000 μmol/L as opposed to 50-100 μmol/L), and much higher than in
the extracellular fl uid (0.5-2 μmol/L). Glutamate passes from the brain to the
blood, but not the other way round due to excitatory amino acid transporters that
move glutamate against the electrochemical gradient, not allowing net glutamate
entry into the brain (Hawkins 2009). Neurotoxic effects have been seen in animal
studies but only at very high doses. The sodium argument is that use of MSG can
increase the sodium level in the diet and hence could potentially contribute to
hypertension. This latter argument is realistic; however, as the use of glutamate
enhances fl avour and potentially salt taste perception, then it should be possible to
control the total levels of sodium in food products to acceptable or low levels.
Perhaps a pragmatic point to note is that, as glutamate works so well in synergy
with 5-nucleotides (see Section 4.2.2), it makes sense to search for natural sources
of glutamate and 5′-nucleotides to use in combination in order to achieve a greater
umami intensity at lower levels of sodium and glutamate than could be achieved
if MSG were used in isolation.

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Hydrolysed vegetable proteins
Hydrolysed vegetable protein (HVP) is a type of process fl avouring that has been
used for many years to give meat-like fl avour to food products. The hydrolysis of
the protein leads to high levels of free glutamic acid. There are two possible types
of HVP manufacture, either acid- or enzyme-hydrolysed vegetable protein. The
former uses hydrochloric acid and temperatures of 100-130°C. At one time this
process led, in some cases, to the formation of a potential carcinogenic compound,
3-chloropropane-1,2-diol (MCPD) (Nagodawithana 1992), which resulted in the