Note: Descriptions are shown in the official language in which they were submitted.
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Use of acid sodium polyphosphates to inhibit
germina-
tion of moulds and yeasts
The present invention relates to the novel use of acid
sodium polyphosphates to inhibit germination of moulds
and yeasts, the polyphosphates having a Pz05 content of
70 - 77~ by weight and an Na20 content of 20 - 27~ by
weight.
It is known that various condensed phosphates such as
glassy sodium polyphosphate, previously termed sodium
hexametaphosphate, sodium tripolyphosphate, sodium
tetrapolyphosphate and sodium metaphosphate in vitro
have an inhibitory action towards various bacterial
species, this action usually being more pronounced in
the case of Gram-posit~_ve bacteria than with Gram-
negative bacteria, since these can break down the
polyphosphates better vi« phosphorase. The mechanism of
action is not yet clearly explained, but it is assumed
that the polyphosphates, by complexing with metal ions
such as calcium and magnesium, interfere with various
enzymatic processes and damage the cell walls
(cf. Phosphates in Food Processing, Chapter 15 in T.E.
Furia, Handbook of Food Additives, 2nd Ed., CRC Press,
Cleveland USA, 1972, p. 621 - 631 and 738 - 742).
These phosphates which are permitted in the food
industry are "neutral" phosphates which, in aqueous
solution, have a pH between 6 and 8, P205 contents of
less than 70~ and NazO contents of greater than 30~.
Whereas phosphates of this type are very stable at room
temperature in neutral to weakly alkaline solution, at
elevated temperatures and in acidic solution they are
hydrolysed to the orthophosphates.
E.J. Griffith, in 1956, described novel acid sodium
phosphates which are prepared by fusing of monosodium
dihydrogen phosphate with phosphoric acid
(cf. US-P 2,774,672 and JACS 78, 1956, 3867 - 3870). By
adding phosphoric acid, PZOS contents of greater than
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70~ are obtained in the glassy or crystalline end
products. The corresponding products are sparingly
water-soluble, highly acidic and relatively stable in
aqueous solution. The acid polyphosphates are intended
to be used together with corresponding carbonates as
baking powder.
DE 43 05 105 - C1 further discloses that such acid
phosphates can also be used for the bacteriostatic
treatment of meat and poultry.
DE 41 28 124 - C2 discloses that such phosphates having
a Pz05 content of 73 - 77~ by weight can be added in the
production of cheese and prevent faulty fermentation
due to the formation of anaerobic bacteria without
preventing the ripening of the cheese.
In addition, it is disclosed that sodium ortho-
phosphate, sodium tripolyphosphates and also acid
sodium ultrametaphosphata_s in fermented milk (yoghurt)
have a stabilizing action on the Lactobacillus
bulgaricus or Streptococcus thermophilus cultures used
and promote bacterial growth (cf. CA 92(23:196522p)). No
action on moulds and yeasts has previously been
observed.
Surprisingly, it has now been found that acid sodium
polyphosphates having P205 contents of 70 - 77~ by
weight, NazO contents of 20 - 27~ by weight and H20
contents of 2 - 3~ by weight also act against moulds
and yeasts and can be used as agents against fungal
contamination in goods and food-processing equipment.
The reason why these acid polyphosphates which, like
other phosphates, also have a growth-promoting action
in the case of lactic acid bacteria, for example, and
only have an inhibitory action in the case of Listeria,
Salmonella and Clostridia bacteria, and also have a
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pronounced inhibitory action against moulds and yeasts,
is not yet known.
The compositions according to the invention are used as
dry powders or, preferably, as aqueous suspensions at
concentrations of up to 25~ by weight, in particular
1.0 to 5~ by weight, of phosphate.
The compositions should be present in the food to be
preserved in an amount of 0.1 - 1.0~ by weight.
For the preservation according to the invention, use
can be made of fruit and vegetable pickles, beer, milk
products, such as dessert puddings, mousse products,
products which comprise yoghurt and whey-based
beverages, which have a certain liquid content in which
the sparingly soluble acid phosphates dissolve slowly,
converting into low-polymeric phosphates which are
conventional in foods (orthophosphate, pyrophosphate,
metaphosphate).
However, it is also possible to add the composition as
a dry powder to products such as cereal, flour, noodle
products etc., in order to achieve preservation during
processing and storage. As experiments show, the mould
and yeast contamination can be decreased significantly
in this manner.
It is also possible to employ the compositions accord-
ing to the invention as cleaning or rinsing liquids for
piping and vessels in which foods are processed, con-
centrations of 1 - 50~ by weight being expedient.
In addition, it can be advantageous to mix the com-
positions according to the invention additionally with
the known neutral food phosphates or other known
bacteriostatics such as sorbates or nitrates and use
them conjointly.
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In particular, preference is given to buffering the
mixture with trisodium orthophosphate to pHs of 5.5 -
6.5, which avoids excessive acidification of the foods
to be treated.
The invention is described in more detail in the
examples below, without intending it to be restricted
thereto.
Example 1
Acid sodium polyphosphate
100 kg of monosodium phosphate (anhydride) and 36 1 of
83~ strength by weight phosphoric acid (= 60 kg)
(Na/P = 0.62) are homogenized and charged into a batch
chamber furnace preheated to 600°C. The mixture is
heated for about 60 minutes at a melting temperature of
400°C (bath temperature). The melt surface still shows
marked bubble formation by exiting water of condensa-
tion. The clear melt is then let off into a cold
casting mould. The material, on cooling, becomes
bubble-free and completely glass-clear transparent. The
material is then discharged from the casting mould,
broken, ground and kept in air-tight containers.
pH: 1.7 (5~ strength by weight solution)
Pz05 content: 77.0 by weight
NazO content: 20.55
3 0 Hz0 content : 2 . 4 5
Example 2
Sodium polyphosphate
50~ strength by weight sodium hydroxide solution and
83~ strength by weight phosphoric acid are continuously
passed via two metering pumps and separate lines into a
reaction vessel in a ratio of Na/P = 0.73. This forms a
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hot suspension of partially neutralized orthophosphoric
acid, which is then passed into a direct-heated chamber
furnace. The heating of the chamber furnace is
controlled via the exhaust air temperature and kept at
500°C. The suspension passes through the chamber
furnace, with condensation, at a mean residence time of
about 2 hours. The melt phosphate which is reacted to
completion is led off continuously at the end of the
furnace via an overflow channel into a water-cooled
cooling drum. The material solidifies there to form a
glass, is then broken and ground. It is charged into
air-tight containers, and. care must be taken to store
it dry.
pH: 1.9
P205 content: 73.0 by weight
Na20 content: 24.2
Hz0 content : 2 . 8
Solubility: 90 minutes (5~ strength by weight
solution stirred) completely
soluble
Loss on ignition: 2.0$ by weight
Raw materials used
1. Thermal phosphoric acid (83~ strength by weight)
Preparation by combustion of elemental phosphorus and
adsorption of the resulting phosphorus pentoxide in
phosphoric acid with continuous dilution to a defined
density by addition of dei.onized water.
Product data
Density (25°C) 1.664 g/ml
Pz05 60.1 by weight
As < 0.5 ppm typically: 0.1 ppm
F < 10 ppm
Heavy metals < 20 ppm
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Copper < 10 ppm
Zinc < 3 ppm
H3P03 < 0.1% by weight
Lead < 1 ppm
2. Sodium hydroxide solution (50% strength by weight)
Density 1.52 g/1
Content 50.0% by weight
Hg < 1 ppm
A1 < 10 ppm
Iron < 3 ppm
Chloride < 10 ppm
Potassium < 50 ppm
Arsenic < 0.3 ppm
The content of the sodium hydroxide solution is checked
per delivery by density determination and titration.
The remaining parameters are determined on random
samples from the trace element analysis by atomic
absorption.
A chamber furnace for preparing the product as des-
cribed in Example 2 includes the actual chamber furnace
made of refractory acid-resistant material with open-
ings for a gas burner, an outlet for the molten
polyphosphate and the exhaust gases and an inlet for
sodium polyphosphate and phosphoric acid or P205, in
addition a water-cooled cooling drum and grinders in
which the coarse and fine comminution of the product
takes place.
Example 3
Composition of the preservative solution
Sodium polyphosphate having a P205 content of 73% by
weight as described in Example 2 is dissolved or
suspended in water at concentrations of l, 2, 5, 10 and
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50~ and adjusted to a pH of approximately 6.5 or 5.5
with trisodium phosphate.
Example 4
Composition of the preservative powders
1 kg of sodium polyphosphate powder having a Pz05 con-
tent of 77~ by weight as described in Example 1 is
mixed dry with 0.6 kg of trisodium orthophosphate
powder and ground in a jet mill to a fineness of
<_ 50 um, preferably <_ 30 ~.un.
In this form, it is suitable as a preservative additive
for solid products.
Example 5
Action of a combination of acid polyphosphates on the
growth of yeasts
Test strain: Saccharomyces cerevisiae (DSM 1333)
The microorganisms were inoculated onto nutrient agar
medium (solid nutrient medium) from a spore suspension
(in sterile mains water). The inoculation was made to
give a titer of 105 spores/g or ml. The colony count
after the heat treatment was 103 per g or ml at time
point to. The colony count was determined on YGC agar
(Merck 116000) in the pour-plate method.
In the concentration series between 0.01 and 1~, the
following result was found for the abovementioned
microorganism:
The concentration of as little as 0.05 of the said
acid polyphosphates led to marked growth retardation of
Saccharomyces cerevisiae; complete inhibition of growth
occurred from a concentration of 0.3~.
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Example fi
Action of a combination of acid polyphosphates on
moulds
Test strain: Aspergillus niger
The microorganisms were inoculated onto nutrient agar
medium (solid nutrient medium) from a spore suspension
(in sterile mains water). The inoculation was made to
give a titer of 105 spores/g or ml. The colony count
after the heat treatment was 103 per g or ml at time
point to. The colony count was determined on YGC agar
(Merck 116000) in the pour-plate method.
A marked inhibition of growth was observed at concen-
trations of 0.1~ to 0.3~; growth was no longer observed
between 0.5~ and 1~.
Example 7
Correspondingly, further yeasts and moulds of the
species mentioned below were tested at a concentration
of 0.5~ and it was also found in this case that the
growth was completely inhibited:
Yeasts
Debaryomyces hansenii
Pichia anomala
Dekkera bruxellensis
Kluyveromyces polysporus
Torulaspora delbrueckii
Candida albicans
Moulds
Fusarium tabacinum
Fusarium monoliforme
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Fusarium culmorum
Aspergillus flavus
Eurotium
Mucor sp.
Example 8
Strong inhibition of growth was found at a concen
tration of 0.1~ and 0.30 of acid polyphosphates for the
following mould species
Penicillium candidum
Penicillium roquefortii
On the basis of the results described which were
achieved for the test microorganisms in nutrient agar
culture, it may be assumed that an inhibitory action on
the abovementioned microorganisms can also be achieved
in foods.
The use of the acid polyphosphates described is there-
fore particularly advantageous in those foods which, on
account of their pH, are a preferred medium in
particular for yeasts and moulds and thus subject to
rapid decay: e.g. fruit juices (orange juice), dietetic
jams, quark and quark preparations, fresh cheese and
fresh cheese preparations, cheese and cheese prepara-
tions, processed cheese and processed cheese prepara-
tions, yoghurt-based products.
In addition, the use of the acid polyphosphates
described is advantageous, for example, for cereals or
in the production of beer.
