Preservation process

Foodstuffs, especially bread, can be preserved against the growth of microorganisms such as mould growth and rope formation by adding to the foodstuffs an acid propionate salt.

The present invention relates to a method of inhibiting the growth of 
harmful micro-organisms, for instance, bacteria and fungi in foodstuffs 
and other organic material susceptible thereto. 
Microbiological deterioration of bread and bread products is well known. 
The wastage of bread due to moulds and bacterial organisms has been 
considerable. This is basically due to the speed of production, rapid 
cooling and the tendency to produce softer bread which gives rise to 
marginally higher moisture content in the bread. Additionally, moisture 
retention is enhanced by the current trends in the packaging of sliced 
wrapped bread. This in turn renders the bread susceptible to attack by 
moulds and bacteria. 
Various methods have hitherto been used to inhibit the growth of harmful 
micro-organisms. The primary consideration for the desired additive being 
that it attacks the micro-organism responsible without being toxic to 
human beings. Examples of additives used hitherto with varying degrees of 
success include the acetates and diacetates of sodium. Propionates of 
sodium and calcium have also been claimed and described in British Patent 
Specification Serial No. 488,560 (Ward Baking Company). Since the 
principal active constituent is believed to be the acid component, the use 
of fully neutralised salts results in the need for adding a larger amount 
of the salt than should be necessary based on the acid content of the 
salt. It has now been found that by using the acid salts, the desired 
level of inhibition activity can be achieved using a relatively smaller 
proportion of the acid salt. 
Accordingly, the present invention is a method of inhibiting the growth of 
harmful micro-organisms in footstuff susceptible thereto comprising 
incorporating therein an acid propionate salt in an amount of between 0.01 
and 1.0% by the dry weight of the foodstuff. 
According to a preferred embodiment, the present invention is a method of 
inhibiting rope formation and mould growth in bread comprising 
incorporating therein an acid propionate salt in an amount of between 0.01 
and 0.4% by the dry weight of the flour. The method of the present 
invention is particularly suitable for inhibiting rope formation and mould 
growth in enzyme leavened or chemically aerated bread. 
Other foodstuffs that may be treated according to the present invention 
include products such as cakes, pastry mixes, biscuits, flour, starches, 
precooked foods such as sausages and meat pies and baby foods. 
The acid propionate salts according to the present invention are the acid 
salts of propionic acid and at least one cation selected from ammonium, 
sodium, potassium, calcium and magnesium such that the ratio of acid to 
the cation in the salt is in the range of 2:1 to 4:1 on a chemical 
equivalent basis. Preferred acid salts are sodium dipropionate, ammonium 
dipropionate, potassium dipropionate, calcium tetrapropionate and 
magnesium tetrapropionate 
The acid propionates are suitably prepared by adding a full propionate salt 
to propionic acid and water. For example a 70% solution of sodium acid 
propionate may be prepared by adding sodium propionate to propionic acid 
in water. 
Alternatively a solution may be prepared by the addition of solutions of 
sodium hydroxide or carbonate to propionic acid. For example 95 pts. of 
42% w/w aqueous solution of sodium hydroxide was added to 148 pts. of 
stirred, cooled propionic acid to yield 243 pts. of a 70% solution of 
sodium dipropionate. 
The acid propionate salts are preferably added in an amount of between 0.01 
and 0.4% by the dry weight of the foodstuff treated, but not so as to 
contravene any legal restrictions on the use of preservatives in 
foodstuffs. 
The acid propionate salt may be added as a solid or as an aqueous solution 
to the ingredients before, during or after the mixing of the ingredients 
depending upon the foodstuff being treated. Furthermore, if the inhibitor 
is to be incorporated in the processing of bread, it is preferably added 
to the water used in making dough from flour rather than to the solid 
components of the bread mix in the bread making process. 
The acid propionate salts are more water soluble than the corresponding 
neutral propionates. This enables solutions to be prepared and used which 
are sufficiently concentrated to provide significant economic advantage 
over the solid neutral propionate salt or aqueous solutions of the neutral 
propionate salt. Solubilities of the calcium and sodium acid and neutral 
propionates in water are given below: 
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solubility at 20.degree. C 
sodium propionate 
99.5g/100g water 
sodium dipropionate 
233g/100g water 
solubility at 25.degree. C 
calcium propionate 
39g/100g water 
calcium tetrapropionate 
48g/100g water 
______________________________________ 
The invention is further illustrated with reference to the following 
Examples.

EXAMPLES 1-3 
Using a Chorleywood Breadmaking Process (C.B.P.) bread recipe, doughs were 
made up containing 6, 9 and 12 oz of 70% sodium dipropionate solution per 
sack of flour. In all cases, the mould inhibitors were added to the 
doughing water. Three dough pieces, moulded to the 4 piece shape, were 
produced from each dough and proved for a constant time of 47 min prior to 
baking. The average proof height, oven height, oven spring and loaf volume 
were determined. A small scale organoleptic test was carried out using a 
panel of 10 persons who were asked to rate loaves from the various 
treatments for odour on a scale from not evident = 0 to extremely evident 
= 5. The mould-free shelf life of the various breads was determined by 
cutting the loaves into five thick slices and exposing each cut surface to 
the atmosphere for 5 min to allow natural contamination with moulds to 
occur prior to wrapping. The number of mouldy cut surfaces was determined 
twice daily during storage at 27.degree. C (80.degree. F) and an 
approximate mould-free shelf life estimated. The results from this test 
are given in Table 1. 
By way of comparison with the above Examples 1-3, tests (a), (b) and (c) 
were carried out using bread with no inhibitor and with calcium propionate 
as inhibitor. The results are shown in Table 2. 
Table 1 
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Proof 
Oven 
Oven 
Loaf 
Average 
Approx. mould- 
Ht. ht. Spring 
vol. 
panel rating 
free shelf life 
Treatment (cm) 
(cm) 
(cm) 
(ml) 
for odour 
(days at 27.degree. C) 
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1. Na. acid prop. 6* oz/sack** 
10.75 
16.00 
5.25 
2870 
0.5 2.75 
2. Na. acid prop. 9* oz/sack** 
9.5 15.75 
6.25 
2863 
1.2 3.75 
3. Na. acid prop. 12* oz/sack** 
9.4 14.80 
5.40 
2807 
2.3 4.00 
__________________________________________________________________________ 
*weight of a 70% aqueous solution. 
*sack contained 280 lbs. of flour. 
Table 2 
__________________________________________________________________________ 
Proof 
Oven 
Oven 
Loaf 
Average 
Approx. mould- 
Ht. ht. Spring 
vol. 
panel rating 
free shelf life 
Treatment (cm) 
(cm) 
(cm) 
(ml) 
for odour 
(days at 270.degree. C) 
__________________________________________________________________________ 
(a) Untreated control 
11.0 
15.75 
4.75 
2909 
0.1 2.25 
(b) Solid Ca. prop. 9 oz/sack** 
10.0 
15.60 
5.60 
2844 
0.6 3.50 
(c) Solid Ca. prop. 14 oz/sack** 
9.75 
15.50 
5.75 
2812 
3.1 4.75 
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**sack contained 280 lbs. of flour. 
At all levels the inhibitors caused under-proof in the fixed proof time 
employed by the oven spring was increased over that of the untreated 
control. Loaf volume was reduced as the amount of inhibitor present 
increased. The reduction in volume using 14 oz/sack of calcium propionate 
was similar to that when 12 oz/sack of sodium dipropionate was used. 
EXAMPLES 4 - 9 
Additional experiments were carried out in a commercial bakery on three 
different occasions to compare the mould-free shelf life of sliced and 
bagged standard bread containing 70% sodium dipropionate solution. In each 
experiment the sodium dipropionate solution was part of the liquor used to 
make up the dough. Additional yeast was added to overcome any effects on 
loaf volume, i.e. 8 oz/sack for 7-9 oz/sack levels of both inhibitors and 
12 oz/sack for 12-14 oz/sack levels of both inhibitors. 
In each experiment, 22 sliced and bagged loaves per treatment were held in 
an incubator at 27.degree. C (80.degree. F) and examined at intervals for 
the numbers of loaves mouldy both on the outside and cut surfaces. Loaf 
volume measurements were carried out on four loaves per treatment. In the 
initial experiments, organoleptic tests were also carried out using a 
panel of 30 persons who were asked to rate the odour present in the 
various breads on a scale from not evident = 0 to extremely evident = 5. 
The results from these tests are summarised in Table 3. 
Again by way of comparison, Examples 4 - 9 were repeated but adding solid 
calcium propionate to the dry ingredients instead of the sodium 
dipropionate solution being added to the dough making liquor. The results 
are shown in Table 4. 
Table 3 
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No. of loaves out of 22 mouldy 
Approx. mould- 
Average loaf 
Average panel 
33/4 
4 43/4 
53/4 
63/4 
free shelf life 
Treatment specific volume 
rating for odour 
days 
days 
days 
days 
days 
(days at 27.degree. 
) 
__________________________________________________________________________ 
4. Na. acid prop. 9** oz/sack 
3.5 1.3 0(0) 
0(0) 
2(1) 
7(1) 
14(1) 
4.50 
5. Na. acid prop. 14** oz/sack 
3.5 1.8 0(0) 
0(0) 
0(0) 
2(0) 
9(0) 
5.25 
6. Na. acid prop. 7** oz/sack 
3.5 1.0 0(0) 
2(2) 
9(6) 
19(9) 
22(15) 
3.75 
7. Na. acid prop. 12** oz/sack 
3.5 1.4 0(0) 
0(0) 
16(7) 
19(13) 
22(14) 
4.25 
8. Na. acid prop. 7** oz/sack 
3.4 4(2) 
5(2) 
16(3) 
22(7) 
22(18) 
3.25 
9. Na. acid prop. 12** oz/sack 
3.5 0(0) 
0(2) 
6(8) 
19(10) 
19(15) 
4.00 
__________________________________________________________________________ 
(3.50) 
**Weight of 70% aqueous solution per sack weighing 280 lbs. 
Table 4 
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No. of loaves out of 22 mouldy 
Approx. mould- 
Average loaf 
Average panel 
33/4 
4 43/4 
53/4 
63/4 
free shelf life 
Treatment specific volume 
rating for odour 
days 
days 
days 
days 
days 
(days at 27.degree. 
) 
__________________________________________________________________________ 
d. Ca. prop. 9 oz/sack (280lb) 
3.4 1.2 0(0)* 
2(0) 
8(2) 
16(3) 
20(5) 
3.75 
e. Ca. prop. 14 oz/sack (280lb) 
3.5 1.5 0(0) 
0(0) 
0(0) 
5(0) 
12(1) 
5.00 
f. Ca. prop. 9 oz/sack (280lb) 
3.5 1.0 0(0) 
3(5) 
7(9) 
20(16) 
21(19) 
3.75 
g. Ca. prop. 14 oz/sack (280lb) 
3.5 1.7 0(0) 
0(0) 
8(4) 
15(11) 
18(15) 
4.50 
h. Ca. prop. 9 oz/sack (280lb) 
3.5 2(2) 
4(2) 
11(6) 
20(11) 
22(14) 
3.50 
i. Ca. prop. 14 oz/sack (280lb) 
3.6 0(0) 
0(0) 
6(0) 
12(1) 
16(3) 
4.25 
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*Figures in brackets show cut surfaces mouldy. 
The specific volume of the breads did not vary greatly in any of the tests, 
indicating that the additional yeast in the recipes was successful in 
maintaining volume. It is also clear from the data shown in Tables 1 and 2 
that the use of acid propionates results in an improved oven spring in 
comparison with the full neutral salts. 
The organoleptic panel was unable to detect any significant difference in 
odour between calcium propionate and 70% sodium dipropionate when used at 
similar levels in bread. It would appear that these two materials have a 
very similar odour threshold. 
The results from the storage tests suggest that at similar concentrations 
the 70% sodium dipropionate formulation is more effective than solid 
calcium propionate in extending mould-free shelf life.