2009_Book_FoodChemistry

12.8 Dry Soups and Dry Sauces 603
pressure-stable stirred tank). Hydrolysis proceeds
at temperatures above 100 ◦ C and the appropriate
pressure with hydrochloric acid or sulfuric acid
(salt-free seasoning).
The hydrolysate is subsequently neutralized to
pH 5.8 with sodium or calcium carbonate or with
sodium hydroxide solution. In this process, the
pH range of 2.5–4 must be passed through as
quickly as possible to repress the formation of
pyrrolidone carboxylic acid from glutamic acid.
The hydroysate is filtered and the filtrate (seasoning)
stored. The filtration residue is washed with
water and refiltered, if necessary. The diluted filtrate
is evaporated and added to the seasoning obtained
in the first step.
The seasoning is subsequently stored; it is filtered
several times before filling. Apart from liquid
food seasoning, seasoning in paste and powder
form and mixtures for use in dry soups and
sauces are produced. These products are partly
bleached with activated carbon and the taste is
neutralized.
The compound 3-hydroxy-4,5-dimethyl-2(5H)-
furanone (HD2F, cf. 5.3.1.3) is responsible for
the intensive, typical seasoning aroma. The products
have a meat- or bouillon-like odor and taste.
It was found in 1978 that genotoxic compounds
are formed in hydrochloric acid hydrolysates of
protein-containing raw materials. Thus, 3-chloropropane-1,2-diol,
2-chloropropane-1,3-diol, 1,3-
dichloropropane-2-ol, 1,2-dichloropropane-3-ol,
and 3-chloropropane-1-ol have been identified as
secondary products of lipids in amounts of 0.1 to
>100 ppm in commercial protein hydrolysates
and products derived from them. In feeding
experiments on rats, these dichloro compounds
were found to be carcinogenic. The testing of
the monochloro compounds is still in progress.
The chlorinated glycerols, which are partly also
present as fatty acid esters, have half life periods
of several hundred days in the hydrolysates.
The N-(2,3-dihydroxypropyl) derivatives of the
amino acids serine and threonine as well as
3-aminopropane-1,2-diol have been detected as
aminolysis products.
Chlorinated steriods, e. g., 3-chloro-5-cholestene
(Formula 12.27a), 3-chloro-24-methyl-5,22-
cholestadiene (Formula 12.27b) and 3-chloro-24-
ethyl-5,22-cholestadiene (Formula 12.27c), have
been identified in the insoluble residue of the
corresponding products.
(12.27)
Moreover, there have been indications of
the presence of chlorinated Maillard compounds
in hydrochloric acid hydrolysates, e. g.,
5-(chloromethyl)furfural.
To avoid or minimize the unwanted compounds
mentioned above, the production process has
been or is being modified, e. g., in the form of
an additional alkali treatment of the hydrochloric
acid hydrolysate. Thus, concentrations of
<1 ppm of 3-chloro-1,2-propanediol were found
in the majority of samples tested in 1990, which
is clearly less than it was in previous years.
12.8 Dry Soups and Dry Sauces
Meat extract, hydrolysates of vegetable proteins,
and yeast autolysate are used to a large extent in
the production of dry soups amd dry sauces. For
this reason, these substances will be described
here. The industrial production of these products
for use in home and canteen kitchens has become
increasingly important in the past 20 years. In
particular, a special pretreatment of the raw
materials made possible the development of
products which, after quick rehydration, give
ready-to-consume complete meals (dry stews),
snacks between meals (dry soups, instant soups),
or sauces.
12.8.1 Main Components
Not only meat extracts, protein hydrolysates,
and yeast autolysates, but also glutamate, ribonucleotides
(inosinate/guanylate), and reaction