TECHNICAL FIELD
The present invention relates to a method for controlling the quality
of a product, which is suitable for use in a method for controlling the freshness
of food such as a gas replaced packaged food, and an oxygen detecting agent for
use in said method.
More particularly, the present invention relates to a method for controlling
the quality of a product typified by a method for controlling the freshness of food,
and an oxygen detecting agent for use in said method, in which, when a detecting
agent is applied directly or indirectly to a product typified by food, for example,
consumers or food transactors can very easily determine the freshness of the food
as a measure of merchandise choice and discrimination or the like, by taking advantage
of such a phenomenon that, after display of food or the like on a display shelf
in a supermarket or the like, when a predetermined quality preservation period corresponding
to the kind of the food or the like has elapsed, the detecting agent undergoes a
change in color.
BACKGROUND ART
Oxygen detecting agents have hitherto been extensively used, for example,
in the field of food, the field of printing ink, the field of electric appliances
and machinery and appliances, and the field of pharmaceutical preparations and medical
supplies, for example, for the determination of quality maintenance and quality
control of various products within packaging containers, for example, food products,
inks, electric appliances and machinery and appliances, and pharmaceutical preparations
and medical supplies.
For example, in the field of food products, the oxygen detecting agent
is mainly used for food products to be stored for a long period of time. Specifically,
for example, in order to prevent an oxidative deterioration of fats and oils and
vitamins contained in food, to prevent damage by vermin, to prevent a change in
color and gloss, and to prevent growth of fungi and bacteria, the oxygen detecting
agent is always enclosed together with a deoxidizer (an oxygen absorbing agent)
in a gas impermeable hermetically sealable packaging bag containing food therein.
In this case, the inside of the packaging bag is maintained in a substantially oxygen-free
state for a long period of time, and, independently of the kind of the food and
the like, the oxygen detecting agent detects a predetermined amount of oxygen which
enters the interior of the packaging bag from the ambient environment and uniformly
undergoes a change in color, and any oxygen detecting agent which undergoes a change
in color under different conditions, for example, depending upon the kind of food
have not been proposed in the art.
Specifically, in the prior art technique, food, a deoxidizer, and
an oxygen detecting agent are enclosed in a packaging bag. With the elapse of a
long-term preservation period of the food, oxygen enters, from the external environment,
the interior of the packaging bag, for example, through a hermetically sealed part
and pinholes formed in the packaging bag. This oxygen is adsorbed on or reacted
with the deoxidizer to reduce or remove oxygen within the packaging bag. For example,
upon a deterioration in performance of the deoxidizer, the concentration of oxygen
within the packaging bag is increased. The amount of oxygen present within the packaging
bag (that is, oxygen which has not been adsorbed on or reacted with the deoxidizer)
is confirmed based on whether or not the color of the oxygen detecting agent has
changed. This is used as a measure of visual determination of the freshness of the
food contained in the packaging bag (see, for example, Japanese Patent Laid-Open
Nos. 308342/2002, 342235/2000, 039429/2000, 276888/1999, and 190729/1999, and Japanese
Utility Model Laid-Open No. 85623/1993).
However, it should be noted that various food products are on the
market, and, in addition, the average number of days required from distribution
routes and time point of production of individual food products to time point of
eating of the food by consumers are also various, and the temperature (product temperature)
of the food during storage and transport or during display, and the form of display
of the food in retailing stage in supermarkets or the like are also various. Therefore,
the deoxidizer or the oxygen detecting agent is not always enclosed in all the food
products.
For example, ready-to-eat daily dishes are in many cases placed on
a food display shelf in a supermarket or the like in a short period, that is, for
about 2 to 3 days at room temperature (15 to 25°C) after the preparation thereof,
and are purchased and consumed by consumers in the two or three day period. In the
case of such food products that are sold on the premise that they are consumed in
a short period after the preparation thereof, neither the deoxidizer nor the oxygen
detecting agent is enclosed.
Further, regarding raw animal meat, if necessary, the deoxidizer and
the oxygen detecting agent are enclosed, and, for example, long-term storage in
a frozen state at such a temperature that does not substantially cause a deterioration
in quality (for example: about -40°C to -18°C), or chilled transport at that temperature
is conducted. Thereafter, the raw animal meat is divided into small parts (a few
hundred grams to a few kilograms) which are then individually packed (or otherwise,
in a breaking-down packaging process, the raw animal meat is previously divided
into small parts which are then individually packed). These small divided packs
are in many cases placed on a food display shelf (cabinet) in a supermarket or the
like for about 3 to 4 days at a temperature of about 5 to 6°C, and; in a few days
during which good freshness of the raw meat can be maintained, are purchased and
consumed by consumers. In the case of the raw animal meat, in the stage of display
on a food display shelf in a supermarket, neither the deoxidizer nor the oxygen
detecting agent is enclosed, probably because the raw animal meat is sold on the
premise that the raw animal meat is consumed in a short period.
When consumers buy products such as food placed on the display shelf
or the like,' most consumers choose the food product based on the price or quality
of the food. In this case; consumers grasp the quality of the food based on the
appearance of the food and, in addition, notations affixed to each product, such
as date of packing and the date of quality preservation period and use these data
as criteria for the choice of the food product.
Further, when consumer buys food products which are then stored in
a home refrigerator or the like and are eaten before the use-by date of the food
product, the consumer consumes the food products within the refrigerator in the
order of the nearest use-by date of the food product based on the appearance and
date of packing of the food product and the like.
Further, as with consumers, for example, persons responsible for controlling
merchandise or employees in retail stores collect individual data, for example,
the appearance of food products and, in addition, notations affixed to each food
product such as the date of packing and the date of quality preservation period
and use these data as criteria for exchange of the food product and disposal or
the like.
In such food control, for consumers and employee of retail stores
or the like, in confirming the quality of each food product, holding the food product
in his or her hand for reading, for example, stamped small letters or numerals indicating
the date of packing and the like is troublesome. In this case, if, for example,
whether or not the food product is still within the quality preservation period
can be visually determined in a simpler manner, for example, based on a change in
color of a label, then this can save labor for the choice of food product and is
convenient. In particular, that whether or not the food is within the quality preservation
period can be visually determined in a simple manner, for example, based on a change
in color of a label, is convenient for consumers, at the time of purchase of the
food product, as well as after the purchase of the food product. Specifically, after
the purchase of the food product, the consumer can store the food product in his
or her home refrigerator or the like and can make an optimal bill of fare so that
the food product which is near the use-by date can be fully consumed.
In the prior art, in the case of food products which are provided
on the premise that they are stored and controlled for a long period of time, for
example, confectionery, a deoxidizer and an oxygen detecting agent are sometime
enclosed in a food packaging container. On the other hand, however, in particular,
in food products which, after preparation, processing, cooking and the like, arrive
on the market based on the premise that they are consumed by consumers in a short
period, for example, raw animal meat, fish meat, read-to-eat daily dishes, fresh
fish and shellfish, fresh vegetables, fruits, dried fruits, Japanese-style confections
and western confectioneries, there has been no simple method for controlling the
freshness of the product.
Further, also in products other than food products, for example, in
the field of printing ink, the field of electric appliances and mamchinery and appliances,
and the field of pharmaceutical preparations and medical supplies, there has been
no simple method, for example, for determining quality preservation and for controlling
quality, which is effective for simple quality control and is particularly effective
for quality control for a short period of time of a few days to a few months.
For example, the above-described Japanese Patent Laid-Open No. 190729/1999
discloses a tape-like stick-on oxygen detecting agent. The tape-like stick-on oxygen
detecting agent includes a tape-like oxygen detecting agent (1). The tape-like oxygen
detecting agent (1) has been formed by attaching an oxygen detecting composition
by coating, printing or impregnation to a non-gas permeable and non-moisture permeable
tape-like base material. The tape-like stick-on oxygen detecting agent further includes
a plastic single-side adhesive tape (2) having, on its one side, at least a partly
transparent adhesive layer with a wider width than the agent (1). The whole oxygen
detecting composition attaching surface of the tape-like oxygen defecting agent
(1) is adhered via the single-side adhesive tape (2) substantially without air gap.
The claimed advantage of this oxygen detecting agent is that the oxygen detecting
agent rapidly causes a change in color.upon a change in the concentration of oxygen
within the packaging container and a reduction in the oxygen concentration can be
easily visually detected without time delay and, thus, the oxygen detecting agent
can be utilized for the quality control of deoxidized and packaged food products
and the like.
This publication, however, never suggests that, when the number of
kinds of products such as food of which the quality is to be controlled and there
are various different quality control conditions such as storage temperature and
packaging form (for example, vacuum or gas replacement hermetic packaging or air
permeable pack packaging) and quality preservation period, how the quality of food
or the like can be controlled satisfactorily and easily in relationship with the
kind of the food and the quality control conditions for the product.
An object of the present invention is to solve the above problems
of the prior art and to provide a method for controlling the quality of a product
typified by the control of the freshness of food, in which, when a detecting agent
is applied directly or indirectly to a product such as food, for example, consumers
or food transactors can very easily determine the freshness of the food as a measure
of choice and discrimination of food products or the like, by taking advantage of
such a phenomenon that, for example, after display of food on a display shelf in
a supermarket or the like, when a predetermined quality preservation period corresponding
to the kind of the food for quality control conditions for the food, has elapsed,
the detecting agent undergoes a change in color.
Another object of the present invention is to provide a novel oxygen
detecting agent, in which, when the oxygen detecting agent is applied directly or
indirectly to a product (merchandise) such as food, for example, consumers or food
transactors can very easily determine the freshness of food as a measure of choice
and discrimination of merchandise or the like, by taking advantage of such a phenomenon
that, after display of a product, for example, food, on a display shelf in a supermarket
or the like, when a predetermined quality preservation period corresponding to the
kind of the food has elapsed, a detecting agent undergoes a change in color, and
that is suitable for use in a method for controlling the quality of a product typified
by the above control of the freshness of food.
DISCLOSURE OF THE INVENTION
The method for controlling the quality of a product according to the
present invention is characterized in that a product and an oxygen detecting agent
having a predetermined sensitivity corresponding to the kind of the product and
quality control conditions for the product are provided in combination and the quality
of the product is controlled by taking advantage of such a phenomenon that, when
a predetermined (quality reservation) period of time corresponding to the kind of
the product and the quality control conditions for the product has elapsed, the
oxygen detecting agent undergoes a change in color as a result of the detection
of the concentration of oxygen, which has infiltrated the oxygen detecting agent,
by the oxygen detecting agent.
In the present invention, the combination of the product with the
oxygen detecting agent having a predetermined sensitivity corresponding to the kind
of the product and the quality control conditions for the product may be contained
within one gas-replaced hermetically sealable packaging bag not containing any deoxidant.
In this embodiment, the quality of the product can easily be controlled as follows.
Specifically, in such a state that a product and an oxygen detecting agent having
a predetermined sensitivity corresponding to the kind of the product and quality
control conditions for the product are placed in a packaging bag and any deoxidant
is not contained within the packaging bag, the air within the packaging bag is replaced
by gas. Thereafter, the packaging bag is kept in a hermetically sealed state. In
this case, the concentration of oxygen which infiltrates the interior of the packaging
bag from the exterior environment with the elapse of a predetermined period of time
corresponding to the kind of the product and quality control conditions for the
product is detected by the oxygen detecting agent, and, consequently, the oxygen
detecting agent undergoes a change in color.
In the present invention, preferably, the product is food and the
quality of the product to be controlled is freshness of the food.
In the present invention, preferably, the oxygen detecting agent comprises
an oxygen detecting agent body and a film that hermetically covers said body and
has a predetermined oxygen permeability and/or carbon dioxide permeability corresponding
to the kind of a product such as food and the quality control conditions for the
product, such as temperature and ambient gas.
Further, preferably, the oxygen detecting agent is provided in combination
with a color sample constructed integrally with or separately from the oxygen detecting
agent and indicates at least a color indicative of that the oxygen detecting agent
is in an initial state before oxidation, a color indicative of that the product
is in the end of use-by date or in such a state that frozen storage should be commenced,
and optionally a color indicative of that the product is in a state before use-by
date, together with the respective corresponding notations.
In the oxygen detecting agent according to the present invention,
preferably, the oxygen detecting agent body has been prepared by impregnating a
porous inorganic oxide with an oxygen detecting composition solution and optionally
drying the impregnated porous inorganic oxide.
In the present invention, preferably, the gas replacement is carried
out by repelling air within the packaging bag and introducing inert gas into the
packaging bag.
In the present invention, preferably, the oxygen detecting agent detects
oxygen and indicates the detection by taking advantage of a change in color of a
redox dye.
In the present invention, preferably, the food is one or at least
two articles of food selected from ready-to-eat daily dishes, Japanese unbaked sweets,
and western-style confectionary.
Further, in the present invention, preferably, the food is one or
at least two articles of food selected from animal meat and fish meat.
In the method for controlling the quality of a product according to
the present invention, after display of a product, for example, food, on a display
shelf in a supermarket or the like, the detecting agent undergoes a change in color,
for example, with the elapse of a predetermined quality preservation period determined
depending upon the kind of the product. Therefore, for example, a consumer or a
person responsible for handling food can very easily determine the freshness of
the food based on a change in color of the detecting agent. Thus, a method for controlling
the quality of a product typified by a method for controlling the freshness of food
can be provided which can be a measure of merchandise selection and discrimination
or the like.
Further, according to the present invention, there is provided an
oxygen detecting agent that is suitable for use in the method for controlling the
quality of a product, for example, the above method for controlling the freshness
of food, and can exhibit the above function.
BEST MODE FOR CARRYING OUT THE INVENTION
The method for controlling the quality of a product according to the
present invention and an oxygen detecting agent used therefor will be specifically
described by taking the method for controlling the freshness of food and an oxygen
detecting agent used therefor, which are particularly preferred embodiments of the
present invention, as an example.
In the method for controlling the freshness of food according to the
present invention (first invention), food and an oxygen detecting agent having a
predetermined sensitivity corresponding to the kind of the food, for example, whether
the food is (i) ready-to-eat daily dishes, Japanese unbaked sweets; western-style
confectionary or the like, or (ii) raw animal meat, fish meat or the like, and quality
control conditions for the food, for example, the temperature of the food during
storage and control of the food (storage temperature), the form of food packaging
(for example, vacuum or gas replacement hermetic packaging or air permeable pack
packaging), and quality preservation period of the food, are placed in combination,
and the oxygen detecting agent detects the concentration of oxygen which enters
(infiltrates) the oxygen detecting agent with elapse of a predetermined period determined
depending upon the kind of the food and quality control conditions for the product,
for example, the elapse of the quality preservation period, and consequently undergoes
a change of color, whereby the control of freshness of the food is carried out.
In the second method for controlling the freshness of food according
to the present invention (second invention), the combination of the food with the
oxygen detecting agent having a predetermined sensitivity corresponding to the kind
of the food and the quality control conditions for the food, for example, freshness,
may be placed within one gas-replaced packaging bag not containing any deoxidant.
In this embodiment, the control of freshness of the food can be carried out as follows.
Specifically, in such a state that food and an oxygen detecting agent having a predetermined
sensitivity corresponding to the kind of the food and freshness control conditions
for the food are placed in a packaging bag and any deoxidant is not contained within
the packaging bag, the air within the packaging bag is replaced by gas. Thereafter,
the packaging bag is kept in a hermetically sealed state. In this case, the concentration
of oxygen or carbon dioxide gas, particularly the concentration of oxygen, which
infiltrates the interior of the food packaging bag from the exterior environment
with the elapse of a predetermined period of time corresponding to, for example,
the kind of the food and freshness control conditions for the food is detected by
the oxygen detecting agent, and, consequently, the oxygen detecting agent undergoes
a change in color, whereby the control of freshness of the food can be carried out.
In the first and second inventions, after the food of which the freshness
is to be controlled is placed under conditions, which cause a deterioration in quality
of the food in a relatively short period of time, such as a food display shelf (cabinet)
in a supermarket, the oxygen detecting agent undergoes a change in color, for example,
due to the elapse of a predetermined quality preservation period, for example, for
indicating the expiration of the quality-preservation period. Therefore, for example,
a consumer/transactor of the product can easily grasp the quality, and, at the same
time, unlike reading of numerical value or character, there is no fear of misreading.
Therefore, the false recognition of quality hardly occurs.
<Oxygen detecting agent>
Preferably, the oxygen detecting agent used in both the method for
controlling the freshness of food in the first invention and the method for controlling
the freshness of food in the second invention comprises an oxygen detecting agent
body, which undergoes a change in color depending upon oxygen permeation (permeability)
and/or carbon dioxide permeability, preferably depending upon oxygen permeability,
and a film for hermetically covering the body (an oxygen permeability control film),
and the film has a predetermined oxygen permeability and/or a carbon dioxide permeability,
particularly oxygen permeability, depending upon the kind of a product such as food,
of which the quality is to be controlled, and quality control conditions, for example,
storage temperature and humidity, kind of replacement gas and gas replacement rate,
and the desired freshness of the food.
When the oxygen detecting agent is, for example, in a sheet or tape
form, an adhesive layer or a double face adhesive tape may be applied to any one
side of the oxygen detecting agent so that the oxygen detecting agent can easily
be adhered and fixed onto a desired counter face such as an inner face or an outer
face (surface) of a packaging bag. Further, when the oxygen detecting agent is in
a tablet form, the tablets may be placed in a transparent air permeable plastic
bag or the like.
Regarding the oxygen detecting agent body and the film (oxygen permeability
control film), the conventional ones may be used in proper combination by taking
into consideration the kind of the product and quality control conditions.
For example, the oxygen detecting agent body may be such that the
concentration of oxygen or the presence or absence of oxygen within or in the outside
of a packaging vessel for food or the like can be detected by detecting the concentration
of oxygen or the presence or absence of oxygen, which is passed or permeated through
the oxygen permeability control film, and, in particular, in gas replacement in
gas replacement packaging, deoxidation packaging or the like, for example, the fact
that oxygen has been satisfactorily removed or that the oxygen concentration is
the limitation value can be detected, and, for example, the concentration of oxygen
or the presence or absence-of oxygen can be indicated by taking advantage of a color
change, that is, a change in hue, tint or lightness.
From the viewpoints of preventing erroneous use of the oxygen detecting
agent and properly controlling the quality, preferably, the oxygen detecting agent
is placed in combination with a color sample constructed integrally with or separately
from the oxygen detecting agent and indicates at least a color indicative of that
the oxygen detecting agent is in an initial state before oxidation, a color indicative
of that the product is in the end of use-by date or in such a state that frozen
storage should be commenced, and optionally a color indicative of that the product
is in a state before use-by date, together with notations which explain the state
of each food corresponding to a color change of the oxygen detecting agent (for
example, blue of methylene blue) and no color change (for example, pink of methylene
blue), and the kind of food, of which the quality is to be controlled by the oxygen
detecting agent, or quality control conditions (for example, storage temperature
of the food, storage time, or packaging conditions, for example, for vacuum hermetic
sealing and gas replacement packaging).
Examples of the oxygen detecting agent body include tablet-like molded
products, those prepared by impregnating paper, thread, absorbent cotton, porous
resin, porous inorganic material, or porous inorganic oxide or other porous member
with an oxygen detecting composition solution and optionally subjecting the impregnation
product to drying or the like, those prepared by coating an oxygen detecting composition
onto the surface of paper or a film and optionally drying the coated paper or film,
or those prepared by printing the above composition.
In particular, in applications where lightfastness is required, for
example, an oxygen detecting agent for quality control of meat or the like which
is displayed on a display shelf which is bright for a few days, the use of a porous
member such as a porous inorganic oxide which will be described later is preferred
from the viewpoint of maintaining the color tone in a better state after the color
change of the oxygen detecting agent.
The oxygen detecting composition may be a conventional one. The oxygen
detecting composition, however, is preferably the so-called redox oxygen detecting
agent. The redox oxygen.detecting agent is typified by a combination of a specific
coloring matter such as methylene blue with a reducing agent for reducing the coloring
matter, such as glucose (see, for example, Japanese Patent Laid Open Nos. 39429/2000,
120493/1978, and 60349/1981). This oxygen detecting agent utilizes such a phenomenon
that, when oxygen is present, methylene blue per se is oxidized to develop blue
while, when oxygen is absent, the coloring matter which has developed blue is reduced
with a reducing agent such as glucose (oxygen, which has oxidized the coloring matter,
is deprived by glucose which per se is oxidized) and consequently becomes colorless.
In general, a coloring matter (for example, red coloring matter such as food red)
is incorporated so that, when methylene blue has become colorless (or a light pink
color), this can be very clearly learned.
Porous inorganic materials among the porous members include activated
carbon, charcoal, and bone black. Porous inorganic oxides include oxides of silicon
(Si), aluminum (Al), magnesium (Mg), calcium (Ca), zinc (Zn), barium (Ba), potassium
(K) and the like, mixtures of these oxides, and multiple oxides containing these
elements.
More specific examples of porous inorganic oxides include silica gel,
silica, zeolite, mordenite, bentonite, montmorillonite, (activated) alumina, magnesia,
titania, activated clay, clay, slag, bauxite, and porous glass beads.
Among these porous members, porous inorganic oxides are preferred.
Further, silica gel, alumina, zeolite, and mordenite are preferred; for example,
from the viewpoints of lightfastness, visibility of color tone change, and safety
of the oxygen detecting agent.
These porous members may be used solely or in a combination of two
or more of them.
Oxygen permeability control films (films) include, for example, transparent
films of polyethylene, polypropylene, polyester, polyamide, polycarbonate, cellulose
acetate, and cellophane. So far as these films are transparent, they may have been
stretched, or a metal or the like may have been provided, for example, by vapor
deposition on the surface thereof, or these films and the like may have been stacked
on top of each other in any combination.
Specifically, for example, conventional transparent films having various
oxygen permeabilities (and/or carbon dioxide permeabilities) exemplified by the
following (i) to (xi) may be used as the oxygen permeability control film (for example,
see "Shokuhin Hoso Binran (Food Packaging Encyclopedia)", p. 495, table 2, published
by Japan Packaging Insutitute):
- (i) : a laminated film of OPP (OPP: biaxially oriented polypropylene, thickness
20 µm/oriented HDPE (HDPE: high density polyethylene, thickness 45 µm)/LDPE (LDPE:
low density polyethylene, thickness 30 µm), having an oxygen transmission rate (oxygen
permeability) of 2000 ml/m2·24 hr·atm (temperature 30°C, wet) and a moisture
permeability of 1 g/m2·24 hr (40°C, 90% RH) ;
- (ii): a laminated film of OPP (OPP: biaxially oriented polypropylene, thickness
20 µm)/CPP (CPP: non-oriented polypropylene film, thickness 30 µm), having an oxygen
transmission rate of 2000 ml/m2·24 hr·atm (temperature 30°C, wet) and
a moisture permeability of 6 g/m2·24 hr (40°C, 90% RH) ;
- (iii): a laminated film of cellophane (thickness 20 µm)/LDPE (LDPE: low density
polyethylene, thickness 40 µm), having an oxygen transmission rate of 1000 ml/m2·24
hr·atm (temperature 30°C, wet) and a moisture permeability of 15 g/m2·24
hr (40°C, 90% RH) ;
- (iv): a laminated film of PVDC (PVDC: polyvinylidene chloride, thickness 3 µm)
coated ONylon (ONylon: oriented nylon: thickness 18 µm)/EVA (EVA: ethylene/vinyl
acetate copolymer resin, thickness 5D µm), having an oxygen transmission rate of
12 ml/m2·24 hr·atm (temperature 30°C, wet) and a moisture permeability
of 13 g/m2·24 hr (40°C, 90% RH) ;
- (v): a laminated film of PVDC (PVDC: polyvinylidene chloride, thickness 3 µm)
coated PET (thickness 15 µm) /CPP (non-oriented polypropylene film, thickness 50
µm), having an oxygen transmission rate of 12 ml/m2·24 hr-atm (temperature
30°C, wet) and a moisture permeability of 8 g/m2·24 hr (40°C, 90% RH)
;
- (vi): a laminated film of PVDC (polyvinylidene chloride, thickness 3 µm) coated
cellophane (thickness 23 µm)/LDPE (low density polyethylene), having an oxygen transmission
rate of 12 ml/m2·24 hr·atm (temperature 30°C, wet) and a moisture permeability
of 10 g/m2·24 hr (40°C, 90% RH) ;
- (vii): a laminated film of PVDC (polyvinylidene chloride, thickness 3 µm) coated
OPP (biaxially oriented polypropylene, thickness 23 µm)/LDPE (low density polyethylene,
thickness 40 µm), having an oxygen transmission rate of 12 ml/m2·24 hr-atm
(temperature 30°C, wet) and a moisture permeability of 5 g/m2·24 hr (40°C,
90% RH) ;
- (viii): a laminated film of PET (thickness 12 µm)/aluminum deposited LDPE (low
density polyethylene, thickness 30 µm), having an oxygen transmission rate of 10
ml/m2·24 hr·atm (temperature 30°C, wet) and a moisture permeability of
1 g/m2·24 hr (40°C, 90% RH) ;
- (ix): a laminated film of aluminum deposited PET (thickness 12 µm)/LDPE (low
density polyethylene, thickness 40 µm), having an oxygen transmission rate of 2
ml/m2·24 hr·atm (temperature 30°C, wet) and a moisture permeability of
1 g/m2·24 hr (40°C, 90% RH);
- (x) : a laminated film of PVDC (thickness 3 µm) coated oriented PVA (thickness
15 µm)/LDFB (low density polyethylene, thickness 70 µm), having an oxygen transmission
rate of 2 ml/m2·24 hr·atm (temperature 30°C, wet) and a moisture permeability
of 5 g/m2·24 hr (40°C, 90% RH); and
- (xi) : a laminated film of PVDC (thickness 12 µm) coated cellophane (thickness
32 µm) /ZDPE (low density polyethylene, thickness 40 µm), having an oxygen transmission
rate of 1.5 ml/m2·24 hr·atm (temperature 30°C, wet) and a moisture permeability
of 2.5 g/m2·24 hr (40°C, 90% RH).
Among the films which may be in a laminated form, the use of transparent
films having a low oxygen permeability (oxygen transmission rate) of 1.0 to 100
ml/m2·24 hr·atm (temperature 30°C, wet), preferably 1.0 to 40 ml/m2·24
hr·atm (temperature 30°C, wet), particularly preferably 1.0 to 15 ml/m2·24
hr·atm (temperature 30°C, wet) exemplified by the above (iv) to (xi) is effective,
for example, in controlling the freshness of food in a low sensitivity state by
applying an oxygen detecting agent to an outer face (pack outer face) in direct
contact with the atmospheric air in a raw animal meat or fish meat pack which will
be described later, or a small bag inner face for a raw meat pack (pack inner face)
through which oxygen or the atmospheric air can substantially freely go in and out.
Further, among these films, the use of transparent films particularly
having a high oxygen permeability of 500 to 3000 ml/m2·24 hr·atm (temperature
30°C, wet), preferably 800 to 2500 ml/m2·24 hr·atm (temperature 30°C,
wet), particularly preferably 1500 to 2300 ml/m2·24 hr·atm (temperature
30°C, wet) exemplified by the above (i) to (iii) is effective in controlling the
freshness of food or the like in a high sensitivity state by applying an oxygen
detecting agent to a hermetically sealable pack on its inner face (the infiltration
of oxygen therethrough being suppressed or prevented) in a ready-to-eat daily dish
or a gas replaced lunch box (pack) containing a ready-to-eat daily dish which will
be described later.
The kind of the film and the like may be properly selected, for example,
depending upon the kind of the food and packaging form.
(Control of freshness of food such as ready-to-eat daily dish or lunch
box (pack) containing ready-to-eat daily dish)
The present invention will be described in more detail with reference
to the following embodiments. As described above, for example, for food such as
ready-to-eat daily dishes or lunch boxes (packs) containing a ready-to-eat daily
dish, after the preparation thereof, they are displayed on food display shelves
in supermarkets or convenience stores or the like at room temperature (15 to 25°C)
to "room temperature - 5°C" for a short period of time of about 2 or 3 days and
are in many cases purchased and consumed by consumers in a few days.
For the ready-to-eat daily dishes or lunch boxes (packs) containing
a ready-to-eat daily dish, an example of a process from preparation to consumption
is as follows. For example, a ready-to-eat daily dish, rice and the like are packed,
for example, within a kitchen in food manufacturing facilities at room temperature
under the atmospheric pressure. An oxygen detecting agent is enclosed in the pack.
The air within the pack is replaced, for example, by inert gas, for example, a mixed
gas composed of nitrogen gas (Nz) and carbon dioxide (CO2) (for example,
N2/CO2 (mixing volume ratio) = 1/0.8 to 1/1.2). In such a
gas-replaced and hermetically sealed state that the concentration of oxygen gas
immediately after gas replacement is generally not more than 0.2% and, in many cases,
about 0.2 to 0.3%, the packs are distributed in a distribution process.
The inert gas is not limited to the above examples, and conventional
inert gases such as nitrogen gas, carbon dioxide, argon gas, and helium gas may
also be used. These inert gases may also be used in a combination of two or more
of them.
According to the construction of the present invention, after display
of the food on a display shelf or the like in a supermarket, on the second to third
day from the preparation of the packed food, that is, after the elapse of a predetermined
quality preservation period corresponding to the kind of the food where the concentration
of oxygen within the packs reaches, for example, about 1%, the oxygen detecting
agent enclosed in the packs (or applied to the inner wall of the packs) undergoes
a color change.
Thus, for example, consumers and food transactors can very easily
determine the freshness of the food and can utilize the above phenomenon as a measure
of merchandise choice and discrimination or the like.
For example, when the oxygen detecting agent body as one member constituting
the oxygen detecting agent is a red coloring matter-containing substrate impregnated
with methylene blue, as soon as the ambient concentration of oxygen increases and
reaches about 0,9 to 1.2% (for example, 1.0%), the color changes from red to blue.
Accordingly, when the object food is, for example, the above ready-to-eat
daily dish or lunch box containing a ready-to-eat daily dish, a film having an oxygen
transmission rate (oxygen permeability) of 1000 to 3000 ml/m2·24 hr·atm,
preferably 1500 to 2500 ml/m2·24 hr·atm, may be adopted as the film (oxygen
permeability control film) for hermetically covering the oxygen detecting agent
body.
Preferably, the oxygen permeability control film is resistant to (insoluble
in) water (cooking liquid), edible oils, alcohols and the like contained in the
food in the pack, and examples thereof include polypropylene (OP)/polyethylene (PE)
laminated films and polyester (PET)/polyethylene (PE) laminated films.
When the oxygen detecting agent body is hermetically covered with
the oxygen permeability control film having the above oxygen permeability, as soon
as the above number of days (for example, two to three days after the preparation
of the food) elapses under the above room temperature (for example, a temperature
around 15 to 25°C), for example, temperature within a ready-to-eat daily dish display
case in a supermarket, the oxygen detecting agent body can undergo a change in color
from red to blue. Therefore, the freshness of the ready-to-eat daily dish or the
lunch box containing a ready-to-eat daily dish (quality preservation period) can
be easily and reliably determined.
Other food of which the freshness can be controlled, particularly
under temperature conditions close to room temperature in a short period, as in
the ready-to-eat daily dish or lunch box containing a ready-to-eat daily dish includes
Japanese-style confectionary and western-style confectionary. Dried fruits, cereals
and the like may also be objects of the freshness control by setting proper conditions.
(Control of freshness of food such as raw animal meat)
When the object food is, for example, raw animal meat, the following
embodiment is often adopted. Specifically, an oxygen detecting agent is enclosed
in combination with divided raw animal meat packs in a hermetically sealable exterior
packaging bag, and, if necessary, a deoxidizer is also enclosed within the exterior
packaging bag. The air within the exterior packaging bag is replaced, for example,
by carbon dioxide (CO2) gas so that the concentration of oxygen gas immediately
after the gas replacement is generally not more than 0.05% and in most cases about
0.001 to 0.05%. In some cases, transport/storage is then carried out for several
tens of days (for example, 40 days) at about 0°C (embodiment A).
Further, for the raw animal meat, the following embodiment may also
be adopted. Specifically, an oxygen detecting agent is enclosed in combination with
divided raw animal meat packs in a hermetically sealable exterior packaging bag,
and, if necessary, a deoxidizer is also enclosed within the exterior packaging bag.
The inside of the exterior packaging bag is deaerated, and, in some cases, for example,
storage in a frozen state for a long period of time at such a temperature that does
not substantially cause a deterioration in quality (for example, about -40°C to
-18°C), or chilled transport at that temperature is carried out (embodiment B).
After transport and storage under such various conditions (embodiment
A or embodiment B), the hermetically sealed exterior packaging bag is opened and
removed, and the raw animal meat is displayed on a food display shelf (cabinet)
in a supermarket or the like. In this case, the oxygen detecting agent which has
been placed in combination with the divided pack comes into direct contact with
the atmospheric air and begins to absorb ambient oxygen (oxygen in the air). After
the elapse of the above predetermined number of days (for example, about 3 to 4
days at a temperature around 2 to 10°C), the oxygen detecting agent body can detect
that oxygen has been passed through and infiltrated the oxygen permeability control
film and the concentration of oxygen which has entered the interior (on the oxygen
detecting agent body side) has reached a predetermined value. The detection of the
oxygen concentration can be learned from a color change of the oxygen detecting
agent from red to blue. Thus, the freshness of the raw meat, that is, whether or
not the quality preservation period has expired, can be easily and reliably determined.
In this case, a film having an oxygen transmission rate (oxygen permeability)
of 1 to 50 ml/m2·24 hr·atm, preferably 5 to 20 ml/m2·24 hr·atm,
may be adopted as the film for hermetically covering the oxygen detecting agent
body (oxygen permeability control film).
Such oxygen permeability control films include polyethylene terephthalate
(PET)/polyacrylonitrile (PAN) laminated film, and vinyl chloride coated polyethylene
film (KNY/PE).
When the oxygen detecting agent body is hermetically covered with
a film having the above oxygen transmission rate, even in the case where, after
packaging of the raw animal meat, the oxygen detecting agent is already applied
to the outer surface of divided packs before transport and storage, or is enclosed
in air permeable divided packs, since the oxygen detecting agent is placed together
with the raw animal meat in the divided pack and, during transport and storage,
is further placed within an exterior packaging bag for transport and storage in
the low oxygen content state, the quality of the raw meat in the divided pack is
not substantially deteriorated. Therefore, during this period, the oxygen detecting
agent does not cause a color change, indicating that the raw meat is fresh.
In the present invention, however, when the exterior packaging bag
for maintaining the low oxygen content state is once opened and the oxygen detecting
agent is exposed to the atmospheric air, as the above number of days (3 to 4 days),
for example, at 2 to 10°C (for example, 6°C) elapse, the oxygen detecting agent
absorbs a predetermined amount of oxygen contained in the atmospheric air, resulting
in a color change of the oxygen detecting agent body from red to blue.
The color change conditions of the oxygen detecting agent can be varied
by varying the oxygen permeability and/or carbon dioxide gas permeability, particularly
oxygen permeability, of the film covering the oxygen detecting agent body (oxygen
permeability control film) to a predetermined value depending upon the kind of a
product of which the quality is to be controlled, such as food, and quality control
conditions such as temperature, humidity, the kind of replacement gas and gas replacement
rate, and freshness. This can realize the determination of the freshness of raw
animal meat (quality preservation period) in an easy and reliable manner.
Other articles of food of which the freshness can be controlled in
the same manner as the above raw animal meat include fishery products such as lobsters
or prawns or shrimps, crab, oyster, and fish (which are often collectively referred
to as "fish meat").
In the above description, preferred embodiments of the present invention
have been described by taking, as examples, the control of freshness of the ready-to-eat
daily dish or the lunch box containing a ready-to-eat daily dish using, as a film
for hermetically covering the oxygen detecting agent body (oxygen permeability control
film), a film having an oxygen transmission rate (oxygen permeability) of 1000 to
3000 ml/m2·24 hr·atm, preferably 1500 to 2500 ml/m2·24 hr·atm,
or the control of freshness of raw animal meat using, as an oxygen permeability
control film, a film having an oxygen transmission rate (oxygen permeability) of
1 to 50 ml/m2·24 hr·atm, preferably 5 to 20 ml/m2·24 hr·atm.
The present invention, however, is not limited to these embodiments only. For example,
the control of quality of various objects can be carried out under various conditions
by hermetically covering the oxygen detecting agent body with conventional films
having various oxygen permeabilities and/or carbon dioxide gas permeabilities (see,
for example, "Shokuhin Hoso Binran (Food Packaging Encyclopedia)", p. 495, Table
2).
As described above in detail, the method for controlling the quality
of a product according to the present invention typified by the method for controlling
the freshness of food can provide a method for controlling the quality of a product
typified by a method for controlling the freshness of a product (food) in which,
for example, consumers or product transactors (for example, food transactors) can
very easily determine quality such as freshness of the product (food) as a measure
of merchandise choice and discrimination or the like, by taking advantage of such
a phenomenon that, after display of a product, for example, food, on a display shelf
in a supermarket or the like, when a predetermined quality preservation period corresponding
to the kind of the product (for example, food) and the quality control conditions
for the product has elapsed, an oxygen detecting agent undergoes a change in color.
In the present invention, products as objects of which the quality
can be controlled are not limited to the above food only, and other products to
which the present invention can be applied include: articles of food which undergo
a deterioration in taste, odor, or flavor due to oxidation degradation or the like,
for example, rehydratable noodle, dried bread-like pieces of wheat gluten, spices,
or sweet stuff; articles of taste which undergo a deterioration in taste due to
oxidation degradation, for example, cigarettes; pharmaceutical preparations, particularly
pharmaceutical preparations in which the quality and efficacy of medicinal ingredients
greatly depending upon the storage period, temperature and the like, for example,
viable cells (for example, lactic acid bacteria and vaccine), blood products, crude
drug-containing pharmaceutical preparations; milky lotions and other cosmetic preparations
containing natural product-derived ingredients and the like in which the odor, color,
skin beautiful effect and the like are likely to be lost by oxidation degradation;
articles of which the quality and efficacy greatly depend upon storage period, temperature,
oxidation degradation and the like, for example, contact lenses and cleaning liquids
and preserving liquids for contact lenses; and components and merchandises in which
rust prevention and the like are required from the viewpoints of function retention,
appearance and the like, for example, clocks and watches and electronic components,
precision machines and instruments, accessories, and artistic handicrafts.
The method for controlling the quality of a product according to the
present invention can provide a method for controlling the quality of a product
typified by a method for controlling the freshness of food in which, for example,
consumers or food transactors can very easily determine the freshness of food as
a measure of merchandise choice and discrimination or the.like, by taking advantage
of such a phenomenon that, after display of a product, for example, food, on a display
shelf in a supermarket or the like, when a predetermined quality preservation period
corresponding to the kind of the food has elapsed, a detecting agent undergoes a
change in color.
In particular, immediately before the display of food, an oxygen detecting
agent having a specific oxygen permeability selected depending upon the kind of
the food and storage control conditions is applied, for example, to the inner face
of a packaging bag which has been subjected to gas replacement or the like for a
reduction in oxygen gas content (packaging bag on its inner face which is isolated
from the atmospheric air), for example, consumers or persons responsible for controlling
food in a supermarket or the like can simply grasp the freshness and the like of
the food and can reduce a fear of false recognition of the quality, without the
need to check a label attached to the food packaging bag, indicating the date of
packing, quality preservation period and the like.
Further, the present invention provides an oxygen detecting agent
that is suitable for use in a method for controlling the quality of a product, such
as the above method for controlling the freshness of food and can exhibit the above
function.
EXAMPLES
The following Examples further illustrate the present invention. However,
it should be noted that the present invention is not limited to these Examples only.
<Oxygen detecting agent for control of freshness of foods such as ready-to-eat
daily dish and lunch box containing ready-to-eat daily dish (a)>
- (i) Oxygen detecting agent body: one prepared by impregnating a substrate (a
carrier) with methylene blue or the like as a redox dye and supporting the methylene
blue or the like on the substrate.
- (ii) Oxygen permeability control film (film): a laminated transparent film of
polypropylene (OP)/polyethylene (PE) having an oxygen permeability (oxygen transmission
rate) of 2000 ml/m2·24 hr-atm.
- (iii) Preparation of oxygen detecting agent: An aqueous solution containing
glucose as a reducing agent, potassium hydroxide as an alkali metal compound, and
methylene blue as a redox dye to be reduced by the reducing agent, and optionally
food red as nonreducing coloring matter is supported on a hygroscopic thin sheet
carrier, and the sheet is then dried and is sealed in the above transparent film
(oxygen permeability control film).
- (iv) Dimension of oxygen detecting agent: 43 mm in length × 30 mm in width
× 0.5 mm in thickness.
<Oxygen detecting agent for control of freshness of foods such as ready-to-eat
daily dish and lunch box containing ready-to-eat daily dish (a-1)>
An oxygen detecting agent was prepared in the same manner as in oxygen
detecting agent (a), except that, in the step of preparation (iii) of the oxygen
detecting agent in the above <Oxygen detecting agent for control of freshness
of foods such as ready-to-eat daily dish and lunch box containing ready-to-eat daily
dish (a)>, silica gel was used instead of the "hygroscopic thin sheet carrier":
- (i) Oxygen detecting agent body: the same as in oxygen detecting agent (a) (i),
except for the substrate.
- (ii) Oxygen permeability control film (film): the same as in oxygen detecting
agent (a) (ii).
- (iii) Preparation of oxygen detecting agent: An aqueous solution containing
glucose as a reducing agent, potassium hydroxide as an alkali metal compound, and
methylene blue as a redox dye to be reduced by the reducing agent, and optionally
food red as nonreducing coloring matter is supported on silica gel, followed by
drying. Thereafter, the resultant granules/powder are sealed in the above transparent
film (oxygen permeability control film).
- (iv) Dimension of oxygen detecting agent: the same as in oxygen detecting agent
(a) (iv).
<Oxygen detecting agent for control of freshness of raw animal meat
(b)>
- (i) Oxygen detecting agent body: one prepared by impregnating a substrate with
methylene blue or the like as a redox dye.
- (ii) Oxygen permeability control film (film) : a laminated film of polyethylene
terephthalate (PET)/polyacrylonitrile (PAN) having an oxygen permeability (oxygen
transmission rate) of 10 ml/m2·24 hr·atm.
- (iii) Preparation of oxygen detecting agent: the same as in oxygen detecting
agent (a) (iii).
- (iv) Dimension of oxygen detecting agent: 43 mm in length x 30 mm in width x
0.5 mm in thickness.
<Oxygen detecting agent for control of freshness of raw animal meat
(b-1)>
An oxygen detecting agent was prepared in the same manner as in oxygen
detecting agent (b), except that, in the step of preparation (iii) of the oxygen
detecting agent in the above <Oxygen detecting agent for control of freshness
of raw animal meat (b)>, silica gel was used instead of the "hygroscopic thin
sheet carrier":
- (i) Oxygen detecting agent body: the same as in oxygen detecting agent (b) (i),
except for the substrate.
- (ii) Oxygen permeability control film (film): the same as in oxygen detecting
agent (b) (ii).
- (iii) Preparation of oxygen detecting agent: An aqueous solution containing
glucose as a reducing agent, potassium hydroxide as an alkali metal compound, and
methylene blue as a redox dye to be reduced by the reducing agent, and optionally
food red as nonreducing coloring matter is supported on silica gel, followed by
drying. Thereafter, the resultant granules/powder are sealed in the above transparent
film (oxygen permeability control film).
- (iv) Dimension of oxygen detecting agent: the same as in oxygen detecting agent
(b) (iv).
[Example 1]
(Control of freshness of foods such as ready-to-eat daily dish and lunch
box containing ready-to-eat daily dish)
A lunch box (polystyrene pack, thickness 100 µm, a commercially available
product) containing ready-to-eat daily dish was prepared at room temperature (20°C).
Thereafter, oxygen detecting agent (a) {prepared by hermetically sealing the oxygen
detecting agent body in an OP/PE laminated transparent film having an oxygen permeability
of 2000 ml/m2·24 hr·atml was placed in the pack. The air within the pack
was replaced by a mixed gas composed of nitrogen gas (N2) and carbon
dioxide (CO2) (for example: N2/CO2 (mixing volume
ratio) = 1.0/1.0), and the pack was hermetically sealed in a film (oxygen permeability:
10 ml/m2·24 hr·atm, thickness 80 µm, nylon (R)./polyethylene laminated
film, a commercially available product).
Two hr after the gas replacement within the pack, the concentration
of oxygen gas within the pack was measured with an oximeter (manufactured by Toray
Engineering Co., Ltd.). As a result, it was found that the oxygen gas concentration
was 0.2% and the color of the oxygen detecting agent was pink.
Sazbsequently, the above food was stored on a shelf having a brightness
of 1000 luxes at room temperature (20°C) in the same manner as in a display shelf
provided in a supermarket.
On the second day after the preparation of the lunch box containing
ready-to-eat daily dish, that is, after the expiration of the quality preservation
period of the lunch box containing ready-to-eat daily dish (two days after the preparation),
the concentration of oxygen within the pack reached 1.0%, and it was found that
the color of the oxygen detecting agent applied to the upper surface within the
pack (ceiling plane) changed from red to blue.
Based on this change in color, a consumer could very easily determine
the freshness of the food. In this stage, any abnormal appearance was not observed
in this food, and the food was still in an eatable state.
[Example 2]
(Control of freshness of food such as raw animal meat)
Raw beef (10 kg) was divided into 500 g parts that were each packed
(polystyrene pack body (thickness 100 µm)) to prepare 20 individual packs which
were then simply packaged using a film (a vinylidene chloride wrap film, a commercially
available product). Subsequently, oxygen detecting agent (b) {prepared by hermetically
covering an oxygen detecting agent body by a PET/PAN laminated transparent film
having an oxygen permeability of 10 ml/m2·24 hr·atm} was enclosed in
a wrapping packaging bag (oxygen permeability: 10 ml/m2·24 hr·atm, thickness
100 µm, nylon/polyethylene (PE) laminated film, a commercially available product)
in such a state that a combination of each divided pack (raw animal meat) with the
oxygen detecting agent (applied to the outer surface of the divided pack). If necessary,
a deoxidant was also enclosed in the wrapping packing bag. Thereafter, the air within
the wrapping packaging bag was replaced by carbon dioxide gas (CO2).
Immediately after the gas replacement, the concentration of oxygen gas within the
wrapping packaging bag was measured with an oximeter (manufactured by Toray Engineering
Co., Ltd.) and was found to be 0.01%.
Subsequently, the packed raw animal meat was stored in a dark refrigerator
at 0°C for 40 days, during which period the color of the oxygen detecting agent
remained unchanged and was pink.
Thereafter, the packed raw animal meat was taken out of the refrigerator,
and the wrapping packaging bag for the raw animal meat was cut and removed. The
raw animal meat, which was divided into individual packs and in which the oxygen
detecting agent was applied to the outer surface of the packs (the divided pack
in its outer surface in direct contact with indoor air), was maintained for three
days at the same temperature as the temperature within a food display shelf (cabinet)
in supermarkets or the like, that is, 6°C, under a brightness of 1000 luxes.
Immediately after display on the food display shelf (cabinet) at 6°C,
the color of the oxygen detecting agent applied to the outer surface of the individual
packed raw animal meat was pink..
On the third day after the initiation of holding of the divided packed
raw meat at the temperature within the food display cabinet, that is, 6°C, it was
found that the color of the oxygen detecting agent in direct contact with the air
changed to blue due to absorption of oxygen surrounding the oxygen detecting agent
(in the air).
On that day (the day on which color change of the oxygen detecting
agent to blue was observed), the packs of raw animal meat were opened for inspection
of odor, color, taste and the like of the meat contained within the packs. As a
result, any abnormal phenomenon was not observed.
Thereafter, this oxygen detecting agent. (b) was allowed to remain
applied to the outer surface of the packs, and the packs were placed side-by-side
on the food display shelf under the same brightness as described above, that is,
1000 luxes. As a result, a Lendency was observed that blue tone color of methylene
blue gradually faded and the color changed to a reddish color which a color tone
of food red contained in the oxygen detecting agent.
[Example 3]
(Control of freshness of food such as raw animal meat)
The procedure of Example 2 was repeated, except that oxygen detecting
agent (b-1) was used instead of oxygen detecting agent (b).
As a result, immediately after display on the food display shelf (cabinet)
at 6°C, the color of the oxygen detecting agent (b-1) applied to the outer surface
of the individual packed raw animal meat was pink.
On the third day after the initiation of holding of the divided packed
raw meat at the temperature within the food display cabinet, that is, 6°C, it was
found that the color of the oxygen detecting agent in direct contact with the air
changed to blue due to absorption of oxygen surrounding the oxygen detecting agent
(in the air).
On that day (the day on which color change of the oxygen detecting
agent to blue was observed), the packs of raw animal meat were opened for inspection
of odor, color, taste and the like of the meat contained within the packs. As a
result, any abnormal phenomenon was not observed.
Thereafter, this oxygen detecting agent (b-1) was allowed to remain
applied to the outer surface of the packs, and the packs were placed side-by-side
on the food display shelf under the same brightness as described above, that is,
1000 luxes. As a result, unlike Example 2 in which oxygen detecting agent (b) was
used, even on the fourth or fifth day after the start of the display, the blue tone
color of methylene blue substantially remained unfaded.