Foodstuff freshness keeping agents

Foodstuff freshness keeping agent comprising a particulate composition which contains a salt of manganese (II), iron (II), cobalt (II) or nickel (II), an alkali compound and a sulfite or a deliquescent substance, and optionally ascorbic acid or its salt, thereby to absorb oxygen in the interior of package of foodstuffs and/or generate therein carbon dioxide gas.

This invention relates to a foodstuff freshness keeping agent, and more 
particularly to a foodstuff freshness keeping agent which when placed in a 
package of foodstuff are capable of therein absorbing oxygen and/or 
generating carbon dioxide gas thereby inhibiting deterioration of the 
foodstuff. 
Almost all kinds of foodstuffs are susceptible of deterioration due to 
oxidation by the ambient oxygen, and vegetables are likely to be wilted up 
by the respiratory action which takes place during storage. The ambient 
oxygen may proliferate microorganisms and vitalize insects. 
To preserve foodstuffs by inhibiting quality deterioration thereof due to 
oxidation, there have been known techniques of vacuum or gas substitution 
packaging, addition of an antioxidant, antiseptic or any other like 
additives, and incorporation of a deoxgenating agent in foodstuff packages 
for eliminating oxygen therein. 
Package interiors are evacuated, according to the vacuum or gas 
substitution packaging method, for preserving foodstuffs therein. Nitrogen 
or carbon dioxide gas is sealed in the evacuated package interiors 
according to the latter method. These methods have the disadvantage that 
an exact selection of combinations of articles to be packaged, gas 
substitution rate and packaging material is required to achieve the 
intended results. Selection of favorable conditions for the methods 
demands a tremendous amount of time and data, and use of a high-efficiency 
packaging machine and a highly gas-impervious packaging material is called 
for in addition. The vacuum packaging method can only be used for 
particular foodstuffs because packages are likely to be deformed in the 
negatively pressurized interior of packages. 
Addition of an antioxidant, antiseptic or any other like additives to 
foodstuffs, which has been extensively adopted for the purpose of 
preservation, has the disadvantage that a technically sufficient amount of 
additives is prohibited by various statutes and regulations concerning the 
foodstuff additives. An increased number of additives have recently been 
totally prohibited from application to foodstuffs in the light of bad 
influences on the human body. 
The method for eliminating oxygen in foodstuff packages by action of a 
deoxygenating agent has been proposed in a number of modes in these days. 
Oxygen is absorbed, in one of the modes of the method, by adding water to a 
mixture of glucose and glucose oxidase. The deoxygenating agent requires 
addition of water from outside thereof for its action, and therefore can 
not be effectively used for low-water content foodstuffs although it may 
effectively perform an oxygen-absorbing reaction in use with the 
foodstuffs containing a great amount of water. 
Another mode of the oxygen eliminating method has been known in which 
foodstuffs are packaged in a material of a polyester/metal 
foil/surlyn/palladium/Surlyn (trade mark of ionomer by Du Pont Co.) 
laminated structure by gas substitution with a mixture gas of hydrogen and 
nitrogen whereby oxygen remaining in the package is reacted with the 
hydrogen under the catalytic action of palladium in the laminated 
structure to permit elimination of oxygen. Specifically, oxygen remaining 
in about 2% in the interior of the package after having been 
gas-substituted in a gas flash manner is reacted with hydrogen into water 
under the catalytic action of palladium at a normal temperature. The 
drawbacks of this method have obviously resided in requiring use of the 
special laminated structure material provided with expensive palladium as 
a lamina, and burdensome operation of gas substitution with a hydrogen and 
nitrogen mixture gas. An improved method is disclosed in U.S. Pat. No. 
3,419,400 in which the hydrogen gas with which the package interior is 
gas-substituted is replaced by a hydride of magnesium, lithium or other 
like metal which can generate hydrogen upon reaction with water. The 
disclosed method still requires use of expensive palladium and was not 
found in use for low-water content foodstuffs to permit hydrogen to be 
generated in an amount enough to warrant a practical application to 
preserve such types of foodstuffs. 
A deoxygenating composition has been known which majorly consists of sodium 
hydrosulfite and calcium hydroxide, and upon addition of a catalyst, water 
and activated charcoal performs an oxygen absorbing reaction expressed in 
the following formula: 
EQU Na.sub.2 S.sub.2 O.sub.4 +Ca(OH).sub.2 +O.sub.2 .fwdarw.Na.sub.2 SO.sub.4 
+CaSO.sub.3 +H.sub.2 O 
Although being capable of eliminating oxygen in a relatively high 
efficiency, the deoxygenating composition requires addition of water from 
outside thereof as a catalyst for such a reaction. Moreover, heat and 
sulfite gas generated upon the reaction undesirably has an adverse effect 
on quality and taste of the foodstuffs thus preserved. 
A further example of the known deoxygenating compositions is disclosed in 
U.S. Pat. No. 2,825,651 which is an intimate mixture of a sulfite and a 
compound capable of releasing metallic ions which are reactive towards 
said sulfite. 
One object of the invention is to provide a foodstuff freshness keeping 
agent which can be applied to all kinds of foodstuffs at a low cost and in 
a facilitated manner. 
Another object of the invention to provide a foodstuff freshness keeping 
agent which are capable of reacting on and absorbing oxygen without 
requiring addition of hydrogen gas or water from outside. 
There is provided according to the invention a foodstuff freshness keeping 
agent comprising a particulate composition essentially consisting of a 
sulfate or a chloride of manganese(II), iron(II), cobalt(II) or 
nickel(II), an alkali compound selected from the group of hydroxide, 
carbonate and bicarbonate, and a sulfite and deliquescent substance. 
A sulfate or a chloride or manganese(II), iron(II), cobalt(II) or 
nickel(II) herein contained may be substituted in part by ascorbic acid or 
its salt. 
Preferably, the composition further comprises powder of iron or other metal 
added therein which presents an enhanced absorbability of oxygen. 
Also preferably, the composition contains a carbonate or a bicarbonate as 
an alkali compound so that it can not only absorb oxygen, but generate 
carbon dioxide gas at the same time. 
Examples of the sulfate and chloride to be contained in the composition of 
the invention are manganese(II) sulfate, iron(II) sulfate, cobalt(II) 
sulfate, nickel(II) sulfate, manganese(II) chloride, iron(II) chloride, 
cobalt(II) chloride, and nickel(II) chloride. Either a hydrate or an 
anhydrous form thereof may be used. Hydrates of iron(II) sulfate, iron(II) 
chloride and manganese(II) sulfate are preferred to the rest of the above 
examples. 
Typical examples of ascorbic acid and its salt are L-ascorbic acid, sodium 
L-ascorbate, D-iso-ascorbic acid, and sodium D-iso-ascorbate. 
The alkali compound to be contained in the composition may be a hydroxide 
such as sodium hydroxide, potassium hydroxide, magnesium hydroxide, 
calcium hydroxide zinc hydroxide and aluminum hydroxide, a carbonate such 
as sodium carbonate, and a bicarbonate such as sodium bicarbonate. When a 
carbonate and/or a bicarbonate are contained in the freshness keeping 
agent, the composition will not only absorb oxygen but generate carbon 
dioxide gas. Calcium hydroxide, sodium carbonate and sodium bicarbonate 
are preferred to the rest of the above examples. 
Favorable examples of the sulfite to be contained in the composition of the 
invention are sodium sulfite, potassium sulfite, calcium sulfite, zinc 
sulfite, barium sulfite, and manganese sulfite, which may all be anhydrous 
or hydrated. Sodium sulfite 7-hydrate Na.sub.2 SO.sub.3.7H.sub.2 O is most 
favorable. 
Use of calcium chloride and magnesium chloride is favorable as a 
deliquescent substance herein above in the light of degree of 
deliquescency, safety and handling. 
It is preferred that activated zeolite, bentonite, activated clay, 
activated alumina or any other like adsorbent be added in order to retain 
water required for the reaction. Any of these adsorbents impart a 
deodorant ability to the freshness keeping agent. When the composition 
includes a deliquescent substance, the adsorbents can serve to adjust a 
degree of deliquescency of that substance. 
There is no specific limitation imposed on ratios of the above stated 
components in the composition, but the latter can be optionally selected 
in dependence on kind of foodstuffs to be packaged. The following 
component ratios are generally favorable. When ascorbic acid or its salt 
is not used, 20 to 100 by weight parts of alkali compound, 5 to 50 by 
weight parts of sulfite or deliquescent substance or mixtures thereof, 0 
to 10 by weight parts of adsorbent, and 0 to 70 by weight parts of iron 
powder are combined therewith all relative to 100 by weight parts of the 
sulfate or chloride of iron(II), etc. When ascorbic acid or its salt is 
used in combination, 200 to 500 by weight parts of the ascorbic acid or 
its salt is added relative to 100 by weight parts of the sulfate or 
chloride of iron(II), etc. as typically used, and relative to 100 by 
weight of parts a mixture of the two components used are 60 to 250 by 
weight parts of alkali compound, 20 to 80 by weight parts of sodium 
sulfite or deliquescent substance, 30 to 80 by weight parts of adsorbent 
and 0 to 80 by weight parts of iron powder. 
An oxygen-absorbing reaction of the foodstuff freshness keeping agent of 
the invention will be described. Water required for the oxygen-absorbing 
reaction need not be supplied from outside. Water is generated by reaction 
of the sulfite and the sulfate or chloride as typically used, or water 
retained in the package by the deliquescent substance may be used to this 
end. In a typical composition containing iron(II) sulfate and sodium 
sulfite, for example, water is released by the following reaction: 
EQU FeSO.sub.4.7H.sub.2 O+Na.sub.2 SO.sub.3.7H.sub.2 O.fwdarw.FeSO.sub.3 
+Na.sub.2 SO.sub.4 +14H.sub.2 O 
A deliquescent substance, when contained in the composition, serves to 
adsorb water naturally existing in the interior atmosphere of package 
and/or generated by the above noted reaction, thus suppressing diffusion 
of water, and further to retain an excess of water, preventing the 
packaged foodstuffs, particularly dried foodstuffs, from being wetted. 
The sulfite and the deliquescent substance may be used alternatively, or 
both in combination as above suggested. No limitation is imposed on a 
ratio between the two when used in combination, but preferably, 0.25 to 6 
by weight parts of the deliquescent substance are to be added relative to 
1 by weight part of the sulfite. 
Using water supplied as above stated, the sulfate or chloride and the 
alkali compound react with each other and thereby absorb oxygen in the 
package, which reaction may be expressed by way of example in the 
following reaction formula: where a deliquescent substance is used; 
EQU 2FeSO.sub.4 +2Ca(OH).sub.2 +H.sub.2 O+1/2O.sub.2 .fwdarw.2Fe(OH).sub.3 
+2CaSO.sub.4 
and where a sulfite is used; 
EQU 2FeSO.sub.4 +2Ca(OH).sub.2 +Na.sub.2 SO.sub.3 +H.sub.2 O+O.sub.2 
.fwdarw.2Fe(OH).sub.3 +2CaSO.sub.4 +Na.sub.2 SO.sub.4 
where a carbonate or a bicarbonate is used instead of hydroxide, generation 
of carbon dioxide gas as well as absorption of oxygen takes place in a 
manner as expressed by way of example in the following reaction formula: 
EQU 2FeSO.sub.4 +4NaHCO.sub.3 +H.sub.2 O+1/2O.sub.2 .fwdarw.2Fe(OH).sub.3 
+2Na.sub.2 SO.sub.4 +4CO.sub.2 
Hydroxide, bicarbonate and carbonate may be used in combination, without 
any limitation on a ratio therebetween. 
Compositions containing iron powder can absorb oxygen by the virtue of 
reaction of the iron powder under the existance of alkali as follows: 
EQU 4Fe+3O.sub.2 +6H.sub.2 O.fwdarw.4Fe(OH).sub.3 
Ascorbic acid or its salt serves to absorb oxygen in a manner which may be 
expressed by way of example as follows: 
##STR1## 
While the typical examples of components are designated in the foregoing 
reaction formulae with reference to which the various reactions of the 
compositions of the invention have been described, any other kinds of the 
related components can as well perform similar reactions. 
The freshness keeping agent of the invention is constituted by a 
particulate composition of the above described components. In use, a 
foodstuff freshness keeping agent of the invention is encased in an air- 
and water-pervious receptacle to be kept from direct contact with 
foodstuffs in a package. For example, the particulate composition is 
encased in a pouch made of a laminated film of paper and perforated 
polyethylene film. The word "perforated" herein used is intented to mean 
that packaging material is porous so as to be pervious to gas and water. 
The encased composition is packed in a package together with a foodstuff. 
Thus, the foodstuff freshness keeping agent functions to absorb oxygen in 
the interior of the foodstuff package and/or generate carbon dioxide gas, 
thereby permitting a long-time storage of the foodstuffs with inhibiting 
oxidation and discoloration, and proliferation of microorganisms therein. 
When the composition is applied to vegetables or like foodstuffs, their 
respiratory action is thereby inhibited, thus permitting a long-time 
storage of the vegetables or the like with freshness kept. 
It is thus apparent that foodstuffs to which the foodstuff freshness 
keeping agent of this invention can be applied include war meat, cattle or 
fish, and vegetable and fruit, as well as bread, cake, ham, cheese, butter 
and any other like processed foodstuffs. 
Table 1 below shows typical examples of the compositions of the foodstuff 
freshness keeping agent of the invention. 
TABLE 1 
__________________________________________________________________________ 
Foodstuff freshness keeping agent 
Component 
1 
2 
3 
4 
5 
6 
7 
8 
9 
10 
11 
12 
13 
14 
15 
16 
17 
18 
19 
20 
21 
22 
23 
24 
25 
26 
27 
__________________________________________________________________________ 
28 
Fe SO.sub.4.7H.sub.2 O 
65 8 
8 
65 
65 11 
11 
65 65 
40 
40 
40 
40 
40 
40 
7 
7 
6 
6 
50 
50 
50 
50 
50 50 
MnSO.sub.4.7H.sub.2 O 
75 75 75 
L-ascorbic acid 
24 21 20 
18 
Sodium 24 21 20 
18 
L-ascorbate 
Ca(OH).sub.2 
15 
15 
24 
24 15 
15 15 
15 10 10 10 20 
20 
4 
4 
4 
NaHCO.sub.3 25 21 
21 25 25 25 25 18 
18 
12 
12 
12 
12 12 12 
Na.sub.2 CO.sub.3.10H.sub.2 O 
21 
21 18 
18 12 12 12 
Na.sub.2 SO.sub.3.7H.sub.2 O 
7 
7 
24 
24 
7 7 
7 
7 
7 
7 7 
7 20 
20 
7 7 
7 7 
CaCl.sub.2.2H.sub.2 O 
10 
10 
8 
8 
10 
10 
10 10 
10 
10 
10 9 10 
10 10 10 
Activated 
2 
2 
20 
20 
2 
2 
2 
18 
18 
2 
2 
2 
2 
2 
2 
2 
2 
2 17 
17 
15 
15 
2 
2 
2 
2 2 2 
charcoal 
Iron powder 26 
26 
26 
26 
26 
26 16 
16 
15 
15 
__________________________________________________________________________ 
Some of the agents shown in Table 1 were subjected to tests for the purpose 
of evaluating capability of elimination of oxygen and of generation of 
carbon dioxide gas. In the tests, 5.0 g samples of each of the agents were 
sealed respectively, together with 400 cc of air, in a 150 mm by 200 mm 
pouch made of a laminate of vinylidene chloride-coated polypropylene film 
(22.mu.) and polyethylene film (50.mu.). Variation of concentrations of 
oxygen and carbon dioxide gas in the pouch with the lapse of time was 
measured by gas chromatography. The results are shown in Table 2. 
TABLE 2 
__________________________________________________________________________ 
Gas concen- 
Foodstuff freshness keeping agent used 
tration (%) 
1 2 3 4 5 10 13 15 16 19 23 25 27 28 
__________________________________________________________________________ 
0.sub.2 
7.8 9.8 7.9 7.6 8.3 7.4 7.7 7.6 10.8 
8.7 7.9 
7.9 8.3 
7.6 
6 hours after 
CO.sub.2 
&lt;0.1 &lt;0.1 
&lt;0.1 
&lt;0.1 
8.0 &lt;0.1 
&lt;0.1 
&lt;0.1 
5.7 
&lt;0.1 7.6 
8.0 7.6 
8.1 
O.sub.2 
2.1 4.3 2.4 2.3 3.8 2.1 2.6 2.5 5.2 
2.6 2.8 
2.4 2.7 
2.2 
12 hours after 
CO.sub.2 
&lt;0.1 &lt;0.1 
&lt;0.1 
&lt;0.1 
11.2 &lt;0.1 
&lt;0.1 
&lt;0.1 
9.7 
&lt;0.1 11.6 
12.6 
11.0 
12.3 
O.sub.2 
&lt;0.1 1.8 &lt;0.1 
1.2 1.5 0.5 1.1 1.1 2.0 
1.1 1.2 
1.0 1.4 
1.1 
18 hours after 
CO.sub.2 
&lt;0.1 &lt;0.1 
&lt;0.1 
&lt;0.1 
0.8 &lt;0.1 
&lt;0.1 
&lt;0.1 
17.4 
&lt;0.1 18.3 
18.8 
17.9 
18.6 
O.sub.2 
&lt;0.1 0.1 &lt;0.1 
&lt;0.1 
&lt;0.1 &lt;0.1 
&lt;0.1 
&lt;0.1 
0.5 
&lt;0.1 0.1 
&lt;0.1 
0.1 
0.1 
24 hours after 
CO.sub.2 
&lt;0.1 &lt;0.1 
&lt;0.1 
&lt;0.1 
20.2 &lt;0.1 
&lt;0.1 
&lt;0.1 
20.1 
&lt;0.1 21.2 
20.3 
21.0 
20.7 
__________________________________________________________________________ 
As shown in Table 2, all the freshness keeping agents could reduce the 
oxygen concentrations in the pouches to less than 1% after the lapse of 24 
hours. Freshness keeping agents Nos. 5, 16, 23, 25, 27, and 28 which each 
contain NaHCO.sub.3 or Na.sub.2 CO.sub.3.10H.sub.2 O were found to 
increase the corresponding concentration of carbon dioxide gas to about 
20% after the lapse of 24 hours.

Examples will be given below where freshness keeping agents of the 
invention were applied in genuine foodstuff packages. 
EXAMPLE 1 
Use was made of freshness keeping agents of compositions shown in Table 3 
below. 
TABLE 3 
______________________________________ 
Freshness keeping agent 
Components 29 30 31 32 
______________________________________ 
Iron(II) sulfate (FeSO.sub.4.7H.sub.2 O) 
3.7 -- 3.3 3.5 
Manganese(II) sulfate (MnSO.sub.4.7H.sub.2 O) 
-- 3.8 -- -- 
Calcium hydroxide (Ca(OH).sub.2) 
0.8 0.8 -- 0.8 
Sodium bicarbonate (NaHCO.sub.3) 
-- -- 1.2 -- 
Sodium sulfite (Na.sub.2 SO.sub.3.7H.sub.2 O) 
0.4 0.4 0.4 -- 
Calcium chloride (CaCl.sub.2.2H.sub.2 O) 
-- -- -- 0.6 
Activated charcoal 0.1 0.1 0.1 0.1 
______________________________________ 
Freshness keeping agents of 5 g of the above compositions were each charged 
in a 50 mm by 60 mm pouch made of a laminate of Japanese paper (40 
g/m.sup.2), perforated polyethylene film (15.mu.), special non-woven 
fabric (19 g/m.sup.2) and perforated polyethylene film (30.mu.). The 
special non-woven fabric in the laminate is formed by a mesh web of 
filaments provided by cutting a flat oriented film. The same special 
non-woven fabric was used in other Examples below. 
Each of the charged pouches was packaged together with a about 300 g loaf 
of bread in a vinylidene chloride-coated oriented polypropylene film 
(22.mu.)/polypropylene film (40.mu.) bag (150 mm.times.200 mm), where 
generation of mold fungi was observed and variation of concentrations of 
oxygen and carbon dioxide was measured with the lapse of time at a 
temperature of 250.degree. C. The results are shown in Table 4. 
TABLE 4 
__________________________________________________________________________ 
Item interior gas concentration (%) 
generation of fungi* 
Lapse of time 
1 day 
7 days 
14 days 
28 days 
1 day 
7 days 
14 days 
28 days 
__________________________________________________________________________ 
O.sub.2 
0.05 
0.01 
0.01 
0.01 
Agent 29 - - - - 
CO.sub.2 
0.00 
0.00 
0.00 
0.00 
O.sub.2 
0.11 
0.01 
0.01 
0.01 
Agent 30 - - - - 
CO.sub.2 
0.00 
0.00 
0.00 
0.00 
O.sub.2 
0.10 
0.01 
0.01 
0.01 
Agent 31 - - - - 
CO.sub.2 
20.7 
20.7 
20.9 
20.8 
O.sub.2 
0.03 
0.01 
0.01 
0.01 
Agent 32 - - - - 
CO.sub.2 
0.00 
0.00 
0.00 
0.00 
O.sub.2 
19.7 
17.6 
-- -- 
Blank** - + + + 
CO.sub.2 
1.20 
13.2 
-- -- 
N.sub.2 gas 100% 
O.sub.2 
0.40 
0.77 
1.27 
2.10 
- - + + 
substitution 
CO.sub.2 
0.01 
1.02 
2.02 
6.76 
__________________________________________________________________________ 
*+ . . . fungi generated; - . . . fungi not generated 
**package holding air without any freshness keeping agent 
As apparent from Table 4, mold fungi were not observed to be generated in 
the packages according to the invention until after 28 days at a 
temperature of 25.degree. C. In contradistinction to the favorable 
results, generation of mold fungi was observed in the gas packaging 
(N.sub.2 substituted) and Blank (air holding) after the lapse of 14 and 7 
days, respectively, thus obviously presenting incapability of keeping 
freshness of the loaf of bread. It was found that the cellular structure 
of bread packaged with the agents 29, 30 and 32 where oxygen was merely 
absorbed had been in part collapsed to result in an unsatisfactory 
appearance. The bread loaf packaged with the agent 31 where carbon dioxide 
gas was substituted for absorbed oxygen was found to remain in a 
substantially same appearance as when the loaf had been packaged. 
EXAMPLE 2 
Use was made of freshness agents of compositions shown in Table 5. 
TABLE 5 
______________________________________ 
Freshness keeping agent 
Components 29 31 33 34 
______________________________________ 
Iron(II) sulfate (FeSO.sub.4.7H.sub.2 O) 
3.7 3.3 2.4 2.0 
Calcium hydroxide (Ca(OH).sub.2) 
0.8 -- 0.6 -- 
Sodium bicarbonate (NaHCO.sub.3) 
-- 1.2 -- 1.2 
Sodium sulfate (Na.sub.2 SO.sub.3.7H.sub.2 O) 
0.4 0.4 0.4 0.5 
Activated charcoal (C) 
0.1 0.1 0.1 0.1 
Iron powder (Fe) -- -- 1.5 1.3 
______________________________________ 
Freshness keeping agent samples of 5 g of the above compositions were each 
charged in a 50 mm by 60 mm pouch made of a laminate of glassine paper (30 
g/m.sup.2), perforated polyethylene film (15.mu.), reinforcement (19 
g/m.sup.2) and perforated ethylene-vinyl acetate copolymer film (40.mu.). 
Each of the charged pouches was packaged together with a 100 mm by 170 mm 
by 60 mm piece of sponge-cake in a 200 mm by 350 mm bag made of laminate 
of vinylidene chloride-coated oriented polypropylene film (22.mu.) and 
polyethylene film (40.mu.), where generation of mold fungi was observed 
and variation of concentrations of oxygen and carbon dioxide gas was 
measured with the lapse of time at a temperature of 25.degree. C. The 
results are shown in Table 6. 
TABLE 6 
__________________________________________________________________________ 
Appearance, 
Item Interior gas concentration (%) 
Generation of fungi* taste, etc. 
Lapse of time 
1 day 
7 days 
14 days 
28 days 
35 days 
1 day 
7 days 
14 days 
28 days 
35 days 
35 
__________________________________________________________________________ 
days 
O.sub.2 
0.07 
0.08 
0.06 
0.01 0.01 cake slightly 
Agent 29 - - - - - deformed 
CO.sub.2 
0.00 
0.00 
0.00 
0.00 0.00 good taste 
O.sub.2 
0.10 
0.09 
0.05 
0.02 0.01 good in 
Agent 31 - - - - - appearance and 
CO.sub.2 
20.1 
19.9 
20.0 
20.0 20.1 taste 
O.sub.2 
0.02 
0.01 
0.01 
0.01 0.01 
Agent 33 - - - - - cake slightly 
CO.sub.2 
0.00 
0.00 
0.00 
0.00 0.00 deformed 
O.sub.2 
0.09 
0.02 
0.01 
0.01 0.01 good in 
Agent 34 - - - - - appearance and 
CO.sub.2 
20.8 
20.9 
20.7 
20.7 20.7 taste 
O.sub.2 
19.8 
18.0 
16.5 
16.2 -- 
Blank - + + + + inedible 
CO.sub.2 
1.00 
12.6 
16.7 
29.2 -- 
O.sub.2 
0.05 
0.42 
0.40 
0.40 0.40 
N.sub.2 gas 100% - - - + + inedible 
substitution 
CO.sub.2 
0.01 
0.12 
0.92 
2.94 3.56 
O.sub.2 
0.70 
0.62 
0.61 
0.57 0.64 change in taste 
CO.sub.2 gas 100% - - - - - (with sour 
substitution 
CO.sub.2 
99.0 
98.6 
98.1 
95.2 92.6 taste and 
__________________________________________________________________________ 
odor) 
*+ . . . mold fungi generated; - . . . mold fungi not generated 
As apparent from Table 6, freshness keeping agents 29, 31, 33 and 34 were 
found to be as satisfactory in antifungal capability as the carbon dioxide 
gas 100% substituted packaging, and to preserve good taste in 
contradistinction to the CO.sub.2 gas substituted packaging which admitted 
of problems of generation of sour taste and odor. It was noted that 
freshness keeping agents 31 or 34, among others, which is capable of 
generating carbon dioxide gas was favorable in application to sponge-cake 
in that the food product could be therby kept free of collapse of the 
cellular structure and deformation of the appearance. 
EXAMPLE 3 
Use was made of freshness keeping agents of compositions shown in Table 7. 
TABLE 7 
______________________________________ 
Freshness keeping agent 
Components 29 35 36 37 38 
______________________________________ 
Iron (II) sulfate 
(FeSO.sub.4.7H.sub.2 O) 
3.7 3.5 3.3 2.4 2.1 
Calcium hydroxide 
(Ca(OH).sub.2) 0.8 0.8 0.8 0.6 0.5 
Sodium Sulfite (NaSO.sub.3.7H.sub.2 O) 
0.4 -- 0.4 0.4 0.4 
Calcium chloride 
(CaCl.sub.2.2H.sub.2 O) 
-- 0.6 0.5 -- 0.5 
Activated charcoal 
0.1 0.1 0.1 0.1 0.1 
Iron powder -- -- -- 1.3 1.4 
______________________________________ 
Freshness keeping agent samples of 5 g of the above compositions were each 
charged in a same manner as in Example 2. 
The charged agents were hermetically packaged together with 200 g of peanut 
butter in two kinds of bags A made of a laminate of vinylidene 
chloride-coated oriented polypropylene film (22.mu.) and polypropylene 
film (22.mu.) and polyethylene film (40.mu.) and B made of a laminate of 
polyamide film (15.mu.) and polyethylene (40.mu.), both having a size of 
150 mm by 200 mm, where oxidation of fat contained in the peanut butter 
were measured in terms of peroxide value with the lapse of time at a 
temperature of 25.degree. C. The results are shown in Table 8. 
TABLE 8 
__________________________________________________________________________ 
Interior 
Item oxygen concentration (%) 
Peroxide value (meq./kg) 
Lapse of time 
1 day 
30 days 
60 days 
90 days 
1 day 
30 days 
60 days 
90 days 
__________________________________________________________________________ 
Packaging material 
Agent 29 0.02 
0.01 
0.01 
0.01 
16 16 17 17 
Agent 35 0.03 
0.01 
0.01 
0.01 
16 16 16 17 
Agent 36 0.02 
0.01 
0.01 
0.01 
16 17 17 17 
Agent 37 0.04 
0.01 
0.01 
0.01 
16 16 16 16 
Agent 38 0.03 
0.01 
0.01 
0.01 
16 17 17 17 
Blank 20.1 
10.0 
8.92 
8.11 
16 35 40 49 
N.sub.2 gas 100% 
substitution 
0.41 
0.50 
0.77 
0.76 
16 19 22 26 
Packaging material 
B 
Agent 29 0.05 
0.04 
0.04 
0.05 
16 18 18 19 
Agent 35 0.06 
0.05 
0.05 
0.05 
16 19 19 18 
Agent 36 0.04 
0.04 
0.04 
0.04 
16 18 18 19 
Agent 37 0.07 
0.06 
0.05 
0.05 
16 19 20 20 
Agent 38 0.05 
0.05 
0.04 
0.04 
16 18 18 18 
Blank 20.2 
12.4 
9.7 9.4 16 41 47 57 
N.sub.2 gas 100% 
substitution 
0.60 
2.71 
3.92 
5.68 
16 25 28 36 
__________________________________________________________________________ 
As apparent from Table 8, almost no increase of the peroxide value was 
detected in case of the freshness keeping agent after the lapse of about 3 
months, presenting an enhanced preserving capability in comparison with 
the N.sub.2 gas substituted packaging. It should be noted that the 
difference of packaging material had a smaller effect on the packages 
holding the agents of the invention than on the N.sub.2 gas substituted 
packaging, so that the former can present a satisfactory preserving effect 
when held in packaging material of a relatively low gas-barrier. 
EXAMPLE 4 
Use was made of freshness keeping agents of compositions shown in Table 9. 
TABLE 9 
______________________________________ 
Freshness keeping agent 
Components 29 31 34 39 40 
______________________________________ 
Iron (II) sulfate 
(FeSO.sub.4.7H.sub.2 O) 
3.7 3.3 2.0 3.2 2.7 
Calcium hydroxide 
(Ca(OH).sub.2) 
0.8 -- -- 0.3 -- 
Sodium bicarbonate 
(NaHCO.sub.3) -- 1.2 1.2 0.8 0.6 
Sodium carbonate 
(Na.sub.2 CO.sub.3.10H.sub.2 O) 
-- -- -- -- 0.6 
Sodium sulfite 
(NaSO.sub.3.7H.sub.2 O) 
0.4 0.4 0.5 -- 0.4 
Calcium chloride 
(CaCl.sub.2.2H.sub.2 O) 
-- -- -- 0.6 0.5 
Activated charcoal 
0.1 0.1 0.1 0.1 0.1 
Iron powder -- -- 1.3 -- -- 
______________________________________ 
Freshness keeping agent samples of 5 g of the above compositions were each 
charged in a pouch in a similar manner as in Example 2. Each of the 
charged pouches was packaged together with five astringent persimmons in a 
200 mm by 300 mm bag made of polyethylene film (60.mu.), with the openings 
hermetically closed by an adhesive cellophane tape, and the conditions of 
de-astringent and softness of the persimmons were evaluated with the lapse 
of time at a temperature of 25.degree. C. Further, freshness keeping 
agents of the above compositions were each packaged together with two 
astringent persimmons in a box-like receptacle provided by vacuum molding 
a polyethylene sheet (200.mu.), with the opening hermetically closed with 
a lid member of polyethylene film (40.mu.), where the conditions of 
de-astringent and softness of the persimmons were evaluated with the lapse 
of time at a temperature of 25.degree. C. The results are shown in Table 
10. 
TABLE 10 
__________________________________________________________________________ 
Lapse of Time 
1 day 4 days 10 days 15 days 
Gas con- Gas con- 
centration 
Astrin- 
Hard- 
centration 
Astrin- 
Hard- 
Astrin- 
Hard- 
Astrin- 
Hard- 
Item (%)* gency** 
ness*** 
(%)* gency** 
ness*** 
gency** 
ness*** 
gency** 
ness*** 
__________________________________________________________________________ 
Packag- 
ing mate- 
rial: Bag 
Agent 29 
3.8 + o 8.6 + o + o + o 
18.0 12.5 
Agent 31 
4.2 + o 10.1 - o - o - o 
38.2 24.2 
Agent 34 
3.9 + o 9.3 - o - o - o 
41.0 24.9 
Agent 39 
5.1 + o 10.7 - o - o - o 
37.6 26.0 
Agent 40 
5.0 + o 11.0 - o - o - o 
38.5 25.0 
Blank 
6.6 + o 7.8 + o + .DELTA. 
+ x 
12.5 10.1 
Co.sub.2 gas 
5.5 + o 12.9 - o - .DELTA. 
- x 
charge 
58.6 5.8 
Packag- 
ing mate- 
rial: Box- 
like re- 
ceptacle 
Agent 29 
2.9 + o 3.8 + o + o - o 
25.5 18.0 
Agent 31 
3.4 + o 5.2 - o - o - o 
42.6 30.0 
Agent 34 
3.0 + o 4.1 - o - o - o 
47.6 30.9 
Agent 39 
4.1 + o 4.6 - o - o - o 
47.7 32.6 
Agent 40 
4.0 + o 5.1 - o - o - o 
46.0 29.5 
Blank 
5.8 + o 10.0 + o + x - x 
13.7 13.2 
CO.sub.2 gas 
0.9 + o 5.7 - o - .DELTA. 
- x 
substitu- 
76.0 7.6 
tion 
__________________________________________________________________________ 
*Concentration of oxygen and carbon dioxide gas are indicated in the uppe 
and the lower lines, respectively. 
**+ astringent; - . . . non astringent 
***o . . . hard; .DELTA. . . . comparatively soft; x . . . soft 
It should be noted in Table 10 that the freshness keeping agents are 
effective in inhibiting persimmon and the like fruit from being softened. 
As apparent from Table 10, the agents 31, 34, 39 and 40 capable of 
generating carbon dioxide gas thereby remove astringent taste of the 
persimmons. It has been known that carbon dioxide gas de-astringe 
persimmon, but the freshness keeping agents could serve to not only 
de-astringe but inhibit softening of persimmons. 
EXAMPLE 5 
Use was made of freshness keeping agents of compositions shown in Table 11. 
TABLE 11 
______________________________________ 
Freshness keeping agent 
Components 29 31 41 42 43 
______________________________________ 
Iron (II) sulfate 
(FeSO.sub.4.7H.sub.2 O) 
3.7 3.3 0.4 0.6 0.3 
Sodium L-ascorbate 
-- -- 1.2 1.1 0.9 
Calcium hydroxide 
(Ca(OH).sub.2) 
0.8 -- 1.2 -- -- 
Sodium bicarbonate 
(NaHCO.sub.3) -- 1.2 -- 1.1 0.9 
Sodium carbonate 
(Na.sub.2 CO.sub.3.10H.sub.2 O) 
-- -- -- 1.1 0.9 
Sodium sulfite 
(Na.sub.2 SO.sub.3.7H.sub.2 O) 
0.4 0.4 1.2 -- -- 
Activated charcoal 
0.1 0.1 1.0 0.9 0.8 
Iron powder -- -- -- -- 0.8 
Calcium chloride 
(CaCl.sub.2.2H.sub.2 O) 
-- -- -- 0.4 0.5 
______________________________________ 
Freshness keeping agents of 5 g of the above compositions were each charged 
in a pouch in a similar manner as in Example 2. The charged pouch and 200 
g of a beef block were placed in a tray provided by vacuum molding a 
laminated sheet of cast polyamide (50.mu.) and cast polypropylene 
(500.mu.) and then hermetically covered with a laminated film of 
vinylidene chloride-coated oriented polypropylene (20.mu.) and cast 
polypropylene (50.mu.). Quality of the packaged raw beef while stored at a 
temperature of 3.degree. C. was evaluated with the lapse of time. The 
results are shown in Table 12. 
TABLE 12 
__________________________________________________________________________ 
Lapse of time 
One week two weeks three weeks four weeks 
Number of Number of Number of Number of 
vital vital vital vital 
Item bacteria* 
Edibility** 
bacteria* 
Edibility** 
bacteria 
Edibility** 
bacteria 
Edibility** 
__________________________________________________________________________ 
Agent 29 2.5 .times. 10.sup.3 
o 1.7 .times. 10.sup.4 
o 4.0 .times. 10.sup.4 
o 5.6 .times. 10.sup.4 
o 
Agent 31 1.2 .times. 10.sup.3 
o 3.6 .times. 10.sup.3 
o 3.7 .times. 10.sup.3 
o 4.5 .times. 10.sup.4 
o 
Agent 41 5.7 .times. 10.sup.3 
o 1.0 .times. 10.sup.4 
o 3.2 .times. 10.sup.4 
o 6.2 .times. 10.sup.4 
o 
Agent 42 1.4 .times. 10.sup.3 
o 7.2 .times. 10.sup.3 
o 7.3 .times. 10.sup.3 
o 8.9 .times. 10.sup.3 
o 
Agent 43 1.1 .times. 10.sup.3 
o 5.2 .times. 10.sup.3 
o 5.6 .times. 10.sup.3 
o 7.6 .times. 10.sup.3 
o 
Blank 1.7 .times. 10.sup.5 
o 3.6 .times. 10.sup.6 
.DELTA. 
9.2 .times. 10.sup.7 
x 1.3 .times. 10.sup.8 
x 
CO.sub.2 /N.sub.2 = 80/20 
9.2 .times. 10.sup.3 
o 4.2 .times. 10.sup.5 
o 9.0 .times. 10.sup.5 
.DELTA. 
2.6 .times. 10.sup.6 
x 
N.sub.2 /CO.sub.2 = 80/20 
1.5 .times. 10.sup.4 
o 1.6 .times. 10.sup.6 
.DELTA. 
4.6 .times. 10.sup.7 
x 8.9 .times. 10.sup.7 
x 
__________________________________________________________________________ 
*number of vital bacteria present in 1 g of raw beef 
**o . . . good; .DELTA. . . . slight putrid smell; x . . . putrefied 
As apparent from Table 12, the beef blocks packaged with the compositions 
of the invention were not modified at all after storage of four weeks. 
EXAMPLE 6 
Freshness keeping agent samples of 5 g of compositions 1,3,8, and 21 shown 
in Table 1 above were charged in a pouch in a similar manner as in Example 
2. The pouch thus charged and 10 bundles of leek each wrapped with a 
perforated polyethylene film (40.mu.) were placed in a cardboard box which 
was then closed. While the leek thus packaged was stored at a temperature 
of 20.degree. C., wilting and decay of leek were observed with the lapse 
of time. The results are shown in Table 13 where numbers of the leek 
bundles which were wilted and decayed are designated by the corresponding 
numbers. 
TABLE 13 
______________________________________ 
Lapse of time 
1 day 3 days 5 days 7 days 
wilt- de- de- de- wilt- 
de- 
Item ing cay wilting 
cay wilting 
cay ing cay 
______________________________________ 
Agent 1 
0 0 0 0 0 0 0 0 
Agent 3 
0 0 0 0 0 0 0 0 
Agent 8 
0 0 0 0 0 0 0 0 
Agent 21 
0 0 0 0 0 0 0 0 
Blank 0 0 2 1 5 3 8 5 
N.sub.2 gas 
holding 
0 0 0 0 1 1 3 2 
______________________________________ 
As apparent from Table 13, the freshness keeping agents of the invention 
were found effective in protecting vegetables against being wilted and 
decayed.