JPS5813406B2 - lettuce leaves - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method of packaging lettuce in a film having an oxygen permeability that meets the lettuce's requirements for oxygen and a carbon dioxide permeability that meets the lettuce's requirements for excluding carbon dioxide.

It is known that the shelf life of lettuce can be extended by suppressing the atmosphere surrounding the lettuce.

Thus, the shelf life of lettuce has been extended by packaging the lettuce in materials such as polystyrene or polyethylene at low temperatures.

Known techniques for packaging lettuce in polyethylene include U.S. Pat. No. 3,450 to Badran et al.
No. 543, for example.

Some of the disadvantages of known techniques for packaging lettuce in polyethylene are as follows.

■) The tendency of lettuce to attack by anaerobes producing alcohols, aldehydes and acids.

2) The lettuce requires precisely controlled refrigeration.

3) Accumulation of harmful carbon dioxide inside the packaging.

Attempts to overcome carbon dioxide build-up by including quicklime, charcoal or potassium permanganate in the packaging are difficult and expensive, and pose health risks.

Prior art attempts to overcome this have included punching holes in the packaging film, which has resulted in dehydration of the lettuce as well as cross-infection with bacteria and mold.

Lettuce is generally transported from the field to a central distribution point.

Lettuce is usually wrapped in film for hygienic purposes somewhere between the central distribution point and the store shelves.

During this time, unwrapped lettuce mixes with the lettuce, causing mold and bacteria to spread between the lettuces.

During transport, the sticky outer leaves are left on the lettuce and act as a host for various infectious diseases that are spread.

After the lettuce is transported from the field where it was grown to a display store or a housewife's kitchen, the outer leaves are removed and thrown away.

Some of the problems with packaging lettuce in polystyrene are 1) the film's low tensile strength resulting in wrap tearing; 2) the membrane is not flexible and excludes air, which is desirable for lettuce packaging. There is no adhesion to the surface.

Immediately after the lettuce is picked, it is packaged in a polyvinyl chloride film with high tensile strength, good adhesion and a high ratio of carbon dioxide permeability to oxygen permeability.

It is advisable to remove and discard the darkened outer leaves prior to packaging.

They are a source of infection and significantly increase the cost of shipping.

Also, by removing them allows the housewife to visually inspect the fresh inner leaves of the lettuce inside the protective packaging.

It is also desirable to wash the lettuce with a disinfectant after removing the outer leaves by other methods.

Next, it will be explained in detail.

In order to extend its shelf life and make it possible to store it at high temperatures, lettuce can be packaged with various permeable films, which have a ratio of carbon dioxide permeability to oxygen permeability of at least 3, 0, gas permeability expressed in cubic centimeters per 100 square inches per liter atmosphere per 24 hours, at least 2
000 oxygen permeability. Wrapping the lettuce in a gas permeable non-porous polyvinyl film having a carbon dioxide permeability of at least 10,000 (about 304 g/m2) It is also best achieved by

As a practical matter, the oxygen permeability of polysalt ratio vinyl film does not exceed 4000, and the carbon dioxide permeability is 25000.
not exceed.

A film is sealed around the lettuce so that no gas can enter or leave the package other than through the film.

The lettuce is then stored in this packaged state.

The shelf life of lettuce packaged in this manner is increased and the lettuce can be stored at higher temperatures than unpackaged lettuce.

This packaging also protects the lettuce against temperature fluctuations during transportation.

Therefore, more time can be spent on transportation, and letanu can be displayed for a longer time in the market.

As a practical matter, a film having a permeability ratio of carbon dioxide to oxygen of about 4 to 10 is desirable.

Carbon dioxide accumulates below 4, which is undesirable;
0 or more is difficult to reach due to the transmission properties of the film.

The desired oxygen permeability is about 2250 to 4000 (about 10
0 to 176 g/m2).

Desired carbon dioxide permeability is about 12,500 to 2,500
0 (approximately 380 to 608 g/m2).

Lettuce is particularly susceptible to damage due to the presence of carbon dioxide.

The present invention is directed to packaging lettuce with a film that is highly permeable to carbon dioxide so that carbon dioxide can freely escape from the packaging.

Because of the increased transmission properties of plasticized polyvinyl chloride film, this film is a desirable packaging film.

The presence of plasticizer increases the permeability of the membrane and the permeability ratio of the membrane.

The plasticized film has the necessary tensile strength, transparency, and water permeability, and can also contain other materials such as anti-fog agents.

Preferred films have a thickness of about 0.75 mil to about 1.35 mil.

Desirable film vapor permeability is from about 6 to about 25 @ (about 90 to 400 g/r2) at 100 square inches per mil at about 38C (below 100 degrees) per 24 hours.
It is.

This moisture permeability allows sufficient moisture to escape, yet retains enough moisture within the package to keep the lettuce from drying out.

A preferred method of packaging lettuce includes individually wrapping each lettuce in a plastic film having the permeability properties described above.

It is then heat sealed to prevent the passage of air into the package other than through the film.

This method protects the lettuce so packaged from mold or other infections during shipment and extends the time the lettuce remains fresh.

It is desirable that lettuce be transported in the same packaging to the store where housewives come for purchase.

In addition to extending the ripening period and preventing infection, the packaging provides an attractive item to place on the sales shelf.

It is desirable that the film be transparent so that housewives can visually inspect the contents.

The film allows the lettuce to remain bright and fresh while it is on the shelves in the store for long periods of time.

Lettuce may be treated with a microbicide wash, such as a chlorination solution, before packaging.

Films that have been successfully used in the practice of this invention are films made from plasticized polyvinyl chloride.

The term polyvinyl chloride includes copolymers of vinyl chloride and other monomers.

For example, polyvinyl chloride refers to a copolymer of vinyl chloride and vinyl acetate or a mixture of the two homopolymers.

Monomers for making other copolymers of polyvinyl chloride that can be used are C1 to C8 alkyl esters of alpha-unsaturated fatty acids having 3 to 5 carbon atoms in the acid molecule.

Examples of alkyl esters include methyl, ethyl, and octyl esters of acrylic acid as well as methacrylic acid.

This copolymer and homopolymer blend provides a satisfactory film for the packaging of lettuce.

Approximately 2 parts by weight of plasticizer per 100 parts of Nylpolymer resin
Present in a proportion of 0 to 60 parts.

A preferred plasticizer used in the formulation is adibate di(2-
ethylhexyl) and di(2-ethylhexyl) phthalate.

Other plasticizers used are acetyl tributyl citrate, epoxidized soybean oil, and butyl phthalate.
Glycote, diisobutyl adipate, diphenyl (2-ethylhexyl) phosphate, butyl benzyl phthalate and the like, as well as mixtures thereof.

The concentration of total plasticizer in polyvinyl film is generally about 20 to 100 parts by weight of plasticizer per 100 parts by weight of vinyl film.
60, preferably at least 30 parts.

Higher levels of plasticizer result in higher permeability and are desirable.

Other additives to the film composition are the usual stabilizing agents for polyvinyl chloride films, such as triphenyl phosphate, nonylphenol, lauric acid and other fatty acid salts, cadmium, calcium, and zinc, and mixtures thereof. Contains agents.

Antifog agents may also be present.

Anti-fogging agents and anti-adhesive agents are water-soluble polyols partial esters of aliphatic monocarboxylic acids (partial ester 1
) and polyalkoxylated derivatives of the above partial esters (designated Partial Ester 2).

Partial Ester 1 is a partial ester (such as a monoester) of a water-soluble 02-6 polyol containing at least two alcohol groups.

At least one of such alcohol groups will not react with an acid to form an ester, and further at least one of such alcohol groups will react with an acid to form an ester.

The polyol component of this partial ester n glycerol;
Ethylene: globylene or other 02-4 glycols; trimethylolpropane, nlubitol and the like.

The acid component may be any 012-1 acid such as lauric acid, oleic acid, stearic acid, palmitic acid and similar acids.
8 fatty acid monocarboxylic acids may also be used.

Partial ester 2 is a polyalkoxylated derivative of a partial ester of an aqueous C2-6 polyol containing at least two alcohol groups.

At least one of such alcohol groups is not reacted with an acid to form an ester, and at least one of such alcohol groups is reacted with an acid to form an ester.

The polyol component of this partial ester is glycerol;
ethylene, propylene or other C2-4 glycols; trimethylolpropane: sorbitol: rubitan and the like.

The acid component may be any C12-18 aliphatic monocarboxylic acid such as lauric acid, palmitic acid, oleic acid, stearic acid, and the like.

The alkoxylate groups of the partial ester 2 are each
It has about 2 to 3 carbon atoms per repeating alkoxyl unit.

The number of alkoxylate groups is about 3-30 per molecule of alkoxylated partial ester.

Examples include polyoxyethylene sorbitan monooleate, polyoxypropylene propylene glycol monooleate, polyoxybutylene trimethylol propane monooleate, and the corresponding stearates, lactates, normitates, and the like.

Partial esters as described above having 5 to 25 alkoxylate groups in the molecule are generally preferred.

Best results are generally obtained with polyoxyethylene rubitan monooleate having about 200 oxyethylene groups in the molecule.

Both partial esters must be present in the composition to impart fog-free properties to the vinyl film.

From the viewpoint of severe anti-fogging properties of films, we have found that adding approximately 2 parts by weight of each ester to 100 parts of vinyl polymer resin provides good anti-fogging properties to films or sheets made from the above-mentioned resins. discovered.

However, if we include a relatively high proportion of common plasticizers in the membrane formulation in order to obtain greater gas diffusion through the film, we may be able to adjust the membrane formulation to maintain the anti-stick properties of the film at a high level. I think it is better to add more than 2 parts of partial ester 1 and at least 3 parts.

Food coloring may be included to establish the desired color.

Generally, vinyl polymer resins, plasticizers, etc. are heated and/or
or highly sheared and blended.

If heated during blending, the temperature is sufficient to properly penetrate the vinyl resin with the plasticizer and the reagents described above.

The blend thus obtained is formed into a film or sheet by extrusion, stretching, blowing or any other convenient method.

Although the thickness of the film or sheet can be varied as desired, useful thicknesses for wrapping lettuce are about 0.5 mm.
1 mil to 2 mils, preferably about 0.75 mils to 1.3 mils
It was found to be 5 mils.

Thicknesses greater than 2 mils may require additional plasticizer to reach the desired gas permeability.

Next, Rutgers (Ru
tgers) Seymour Gilbert of Canine Science
was obtained using the method developed by Professor urGiltert.

The data collection method was published in January 1969 by Packaging Engineering (P.
ackage Ehgineering), pages 66 to 69, in an article written by him.

Oxygen permeability and carbon dioxide permeability are expressed in cubic centimeters per 100 square inches per 24 hours at 1 atm.

Moisture permeability is given in Durhams per 100 square inches per 24 hours at approximately 38C (100F) (90 parts relative humidity).

Gas permeability data were obtained at 24°C.

In general, in the detailed description and claims, as well as in the following examples, all quantities and percentages are by weight unless otherwise specified.

Example 1 A group of lettuce was picked and its outer leaves were removed.

It was encapsulated using a polyvinyl chloride membrane with added plasticizer.

The film had a thickness of O, 75 mils, a moisture permeability of 20, an oxygen permeability of 2250, a carbon dioxide permeability of 12500, and a ratio of carbon dioxide permeability to oxygen permeability of 6.3.

The film was heat sealed to exclude any non-air diffusing through it.

After the package is transported to its final destination, it is heated to approximately 23C (73°
(below).

The total time for all transportation and storage is 17 days.

Some of the packages were opened at the end of the storage period.

The lettuce bulbs were fresh. No mold or its growth was observed.

The results were revisited using films with oxygen permeability of 2,000 to 2,500 and carbon dioxide permeability of 10,000 to 15,000.

Lettuce bulbs picked at the same time were completely rotten on the 17th day when they were stored without packaging.

Example 2 The series of films used had a thickness of 0.75 mil, a carbon dioxide permeability that varied significantly and was less than 10000, an oxygen permeability that varied significantly and was less than 2000, and The lettuce packaging procedure described above was repeated, except that the carbon dioxide permeability ratio was significantly different, being at least 3.

At the end of the 17th day, all the lettuce had an unpleasant odor.

Something completely corrupted me.

Furthermore, the further the film was moved away from the desired area, the more severe the damage was.

Next, embodiments of the present invention will be listed.

(1) The film size is approximately 2250 to 4000 (approximately 100 to 4000)
1769/m2) and a carbon dioxide permeability of about 12,500 to 25,000 (about 380 to 608/m2). 1.35 mil.

(3) The moisture permeability of the film is 1 at approximately 38C (100'F)
6 to about 25 grams per 24 hours (about 90 to 400 I/m2) per 100 square inches per mil.

(4) The method of paragraph (1) above, wherein the film has a ratio of carbon dioxide permeability to oxygen permeability of about 4 to 10.

(5) The method according to the claims, wherein the lettuce is treated with an antimicrobial agent before packaging.

(6) The method according to the preceding paragraph (5), wherein the antimicrobial agent is chlorine.

Claims (1)

[Claims] 1 (A) Removing outer leaves from lettuce; [F]
The oxygen permeability is at least about 2000 (approximately 44 g/r2) and the carbon dioxide permeability is at least about 2000 (expressed as gas permeability in cubic centimeters per 100 square inches at 1 atmosphere per 24 hours). Approximately 10,000 (
Wrapping the lettuce in a polyvinyl chloride film having a uniform gas permeability of about 304 g/r2) and a ratio of carbon dioxide permeability to oxygen permeability of at least 3.0. (c) sealing the film so wrapped around the lettuce; a method for packaging lettuce immediately after harvesting;