IL45824A - Sheet for preserving vegetable matter and method of production - Google Patents

Description

Sheet for Preserving Vegetable Matter and Method of Prod action Π"πχ**> y nni nonm ia loin -na?cft nyn» SUMMARY A sheet for preserving vegetable matter by controlling the humidity in a film- enveloped package packed with vegetable matter, consisting of the front and rear surfaces composed of fibers entangled with and bonded to each other in the form of crust and the inner portion where fibers are neither entangled with nor bonded to each other, and a method for producing the above.

The present invention relates to a sheet for preserving vegetable matter by controlling the humidity in a film-enveloped package used for storing or transporting vegetable matter and a method of production thereof. » The reasons for the decrease in the freshness of vegetable matter after picking thereof have been fully clarified in the past. Though, after picking, supply of nutrition is discontinued vegetable matter continues respiration and consumes nutriment within the body. As the result, water transpires and vegetable matter decays. The maximum period of s oring or ■6x> transporting vegetable matter should end before it starts decay. Λ The above period is relatively short, though it varies subject to the time of picking of vegetable matter -temperatures humidity, the gas composition o£ the atmos here and the like. The operation of vegetable dealers is restricted by the above limitation of time. It is indeed surprising to be able to adjust the life of vegetable matte so as to extend it by adjusting the respiration. In: adjusting the respiration, it is necessary to adjust conditions oiach as temperature e humidity and the gas composition in ho atmosphere. Humidity and the gas composition re ° particular importance at normal temperature. With respect to the gas composition, the freshness of vegetable matter is effectively maintained in case vegetable matter is sealed in a container so that the concentration of carbon dioxide emitted from - 2 - vegetable matter increases and oxygen is consumed, or in case, like the CA (controlled atmosphere) storage method, respiration is restricted artificially by increasing the concentration of carbon dioxide. However, if the concentration of carbon dioxide is too high, the normal respiration is hampered considerably and the so-called carbon dioxide defect arises. This remarkably reduces the commercial value of vegetable matter.

Therefore, the control o the gas composition in the - up to now -atmosphere has /been effected by the use of a film with sr relatively good air permeation such as polyethylene filn» as a packing material, by selecting the kind and thickness. of film taking into consideration the kind and the quanti y of vegetable matter to be preserved and th conditions of preservation;, or by providing pin holes or perforations in the film. ' .

A T^i Mtg--te-hm .-i-y-,--¾-he humidity range 'of approximately 85 to 90¾ is generally recognized as appropriate for v getable matter preserved in the film-covered package, Ά humid ty ' in excess of'90% is regarded as too hum d for preservat on. Again, if the humidity is below 85¾, water in the body of vegetable matter is compelled to transpire to an eicccsniyo . degree.

When the above-mentioned film is used, without any pin holes, as a packaging material, it may be possible to ; maintain ' the concentration of carbon dioxide at a desired level. However, since such film has no or little vapor permeation, the inside of the package is liable to become excessively humid and water droplets are formed on the J surface of the film. On the other hand, in case of a film with pin holes, it may operate satisfactorily when the " ' humidity of the atmosphere surrounding the package is appropriate for the preservation of vegetable matter. In rainy or dry seasons, however, the inside of the package becomes excessively humid or dry as the case may be, affecting the vegetable adversely. ; In order to eliminate the above defects in the use of a film for packaging, a method may be employed whereby a film without any pin holes is used together with a moisture absorbent material to prevent the inside of the package from becoming excessively humid. However, the use of conventional moisture absorbents generate an excessively dry state in the package, thereby quickening deterioration of the vegetable.

As mentioned above, not only the gas composition but also humidity βηο ΐά be adjusted to attain the purpose o£ maintaining the freshness of vegetable matter by controlling the respiration thereof. The present status of the vegetable such that it is packaging art is, frankly ,/ almost impossible to attain - 4 - simultaneous adjustment of the gas composition and humidity. ^ The inventor has succeeded in resolving the above problem by controlling the concentration of carbon dioxide gas in the package by means of a film envelope and simultaneously controlling the humidity in the package by the use of the sheet for preserving vegetable matter as explained below.. .

The present invention provides a sheet for preserving vegetable matter by controlling the humidity in a film-enveloped package packed with vegetable matter, consisting of a sheet mainly made of fibers obtained by loosening vegetable (a s will be explained) _ . , , , . pulp, /the front and rear surfaces of said sheet being composed of fibers entangled with .and bonded to each other a crusty skin in the form of crusi, the state of entanglement or bonding interior gradually decreasing towards the inside of the sheet, inhere there is no entanglement or bonding between the fibers, The present invention further provides a method for the production of the sheet for preserving vegetable matter, comprising the steps of loosening of vegetable pulp aed into fiber s and molding them into a felt-like sheet, spraying' an appropriate amount of water or a solution of preservative material onto a surface of the sheet, applying pressure thereon, administering a similar treatment to the other surface, and then heating and drying the sheet.

The term "vegetable matter" used herein covers broadly fruits, garden produce, flowers and other perishable vegetables. 45824/2 -5- The term "vegetable" is also used nterchangeably in the present specification.

The sheet of the present invention consists of vegetable fibers formed into an integral structure.

There is no substantial limitation to the kind of vegetable pulp used for the present invention. A typical vegetable pulp is wood pulp. Tests conducted by the inventor have demonstrated that the pulp of bagasse obtained from sugar canes can also be used satisfactorily for the present invention.

The manufacture of the sheet of the present invention employs loosened vegetable fibers. The loosening of vegetable pulp into fibers is attained by first forming a slurry of pulp by cooking the plant, drying the slurry and mechanically separating the dried pulp into individual fibers.

According to the present invention, loosened fibers are piled to a desired thickness to form a sheet in the form somewhat like fet or batting, the front and the rear surfaces thereof are sprayed with the appropriate amount of water or a solution of preservative material, and then both surfaces of the felt-like body are placed under a certain rotational pressure and the felt-like body dried to form an integral sheet. (The term "rotational pressure" - wherever used with present specification - indicates the pressure applied by the rotation of a roller upon a substance underneath it).

According to British Patent 1071191 there is already known an absorbent fiber material comprising a fluffy batt of fibers and containing an adhesive bonding material distributed through the fibers at least on the surface. -5a- The sheet of the present Invention 1s di fferent from the disclosure of sai d British patent in that the former does not use any adhesi ve bonding material and thus it Is obtained 1n a much simpler and less costly process .

Also* the British patent does not suggest the use of the absorbent fiber material for preserving vegetable matter In a fi lm-enveloped package, wherein a main feature of the present invention lies . - 6 - The present invention will be described below in further detail. Fibers carefully loosened by a milling machine such as a hammer mill are fed through a fan into a blow duct.

At the outlet of the duct is provided a moving screen belt for setting the fibers thereon. A suction box is provided behind the screen belt. By the coaction of the above means fibers are piled up to a desired height to form a felt-like sheet Water or a preservative is sprayed onto a surface of the sheet thus formed. To the sheet is then imparted a certain rotational pressure by means of a roller. As an example,, when the upper surface of the felt-like sheet has an area 2 of 900 cm and the sheet is 10 mm' thick, 1 - 30 g, more of preferably 3 ■ 5 g, of water or /a 10¾ or lower, preferably 5% solution of a preservative may be sprayed onto the upper surface of the sheet. The entire upper surface of the sheet is then placed under a rotational pressure of approximately 3R.-fc© o.1 to .5 kg/cm , 0.2 to 0.3 kg/cm .

SO--kg., more preferably approximately ¾fr-frt»a3D..J¾.. Thereupon, the rear surface of the sheet is also sprayed and placed. under pressure and the sheet is dried in an air-circulation box type drier at approximately 80 to 120°CS more preferably at 100 to 110°C and most preferably at about 105°C.

The felt-like sheet, before treatment, is a mere accumulation of short fibers. There is no entanglement between fibers forming the sheet. The sheet lacks in. form retentiveness . However, when the surfaces of the sheet are sprayed with water or a solution of a preservative and the wet layers in the sheet are compressed and dried, strong between hydrogen bonds are formed among the fibers, the fibers being connected /to each other. The felt-like sheet becom.es dense and hard, like bread crust.

In the above sheet, only the fibers in the wet portions are bonded to each other by a chemical reaction and become crust-like after drying. The remaining portion does not undergo any change and remains felt-like. Since the crustlike portions are formed on both surfaces of the sheet, said are partitioned portions inle a.ipJL£id by a felt-like portion in the middle of the sheet. The crust-like portions and the felt-like portion cannot be distinguished from each other discretely.

The state of entanglement in the outer surfaces gradually changes into a state where no entanglement exists in the interior of the sheet.

The sheet thus obtained has a remarkable hygroscopicity and moisture retention, far superior to the conventional moisture absorbents.

When fibers are formed into a felt-like sheet, which is then sprayed, compressed and dried, many capillary ttfees_&£fi conduits of fluid are / formed among the fibers in the crust-like portions. Therefore, when a drop of water is placed upon any spot in a crust -like portion, the water spreads very quickly into the spaces between the fibers and to the entire area of the portion.

When the crust-like portion becomes saturated by absorbing per colate s moisture or water, water precip J;«aJLe_s to the inner felt -like portion of the sheet. Since the inner portion is not compressed densely, unlike the crust-like portions, the air/fiber volume ratio in the inner portion is large. This enables the inner portion to retain a great amount of water as compared to the crust-like portions.

As long as the humidity in the film-enveloped package freater fll^r than the humidity in the inner portion of the sheet , the sheet absorbs moisture in the package. When, on the other hand, the humidity in the inner portion or the surface greater portions becomes substantially laxgsx than the humidity in the package, moisture will be emitted from the sheet into the package. The degree of the emission of moisture naturally ab sorption depends on various conditions such as the s-»e*ie« of water by the sheet and the gravity of water. The humidity in the package is controlled by the above mechanism.

When the sheet is formed as in the present invention, while the surface of the sheet facing the vegetable packed in the package performs the above function, the other crust-like portion mainly plays the role of retaining the form of the sheet besides performing the moisture-absorbing function.

As is understood from the above, the sheet of the present invention is most effective as a humidity controlling device in a film- enveloped package. An appropriate amount of the sheet should be placed in the package. The appropriate amount of the sheet varies depending upon the amount of respiration of vegetable matter in the package and other factors. Generally the amount ranges from 0.5 to 15 weight percent, and in case of tomatoes it may be 1 to 3 weight percent, and more preferably 1.5 weight percent.

When the sheet of the present invention is used in a package, the direct contact of the sheet with the vegetable should be avoided as much as possible. In case the sheet has absorbed a large amount of water, the vegetable may be adversely affected by £¾ε contact with the sheet. Therefore, it is desirable to provide an appropriate non-moisture-absorbing separator between the sheet and the vegetable.

As mentioned above, a solution of a preservative may be sprayed onto the surfaces of the felt-like sheet in one stage of the manufacture of the sheet of the present invention. The application of a preservative is often desirable in order to prevent the generation of bacteria inside the sheet along with the wetting of the sheet by impregnating the outer layers thereof with the preservative.

Claims (1)

1. 45824/2 -10- WHAT IS CLAIMED IS : ( 1 ) A sheet for preserving vegetable matter by controlling the humi dity in a film-enveloped package packed with vegetable matter as herein defined, consisting of a sheet made mainly of fibers obtained by loosening vegetable pulp (aff defined above) , the front and rear surfaces of said sheet being composed of fibers entangled with and bonded to each other without adhesi ve in the form of a crusty ski n , the degree of entanglement or bonding gradual ly decreasing towards the interior of the sheet, where there is no entanglement or bonding between the fibers. (2) A sheet for preserving vegetable matter in accordance with claim 1 , comprising further a preservati ve material impregnated in the front and rear surfaces thereof. (3) A package assembly for preserving vegetable matter wrapped wi th a plasti c fi lm having gas permeation , characteri zed by comprising therein a sheet for preserving ^vegetable matter in accordance wi th cl aim

1. (4) A package assembly in accordance with cl aim 3, characteri zed In that said sheet is placed therein 1n the amount 0.5 - 15 weight percent based upon the vegetable matter contained in said assembly. (5) A package assembly 1n accordance with claim 3, characterized in that a non-moisture absorbing separator is provided between said sheet and the vegetabl e matter contained in said assembly. - 11 - ( 6 ) A package assembly in accordance with claim 3 , characterized in that said sheet placed therein is impregnated with a preservative material on the front and rear surfaces thereof . (7) A package assembly in accordance with claim 6 , wherein a non-moisture absorbing separator is provided between said sheet and the vegetable matter contained in said assembly, ( 8 ) A method for the production of the sheet for preserving vegetable matter in accordance with claim 1, comprising the steps of loosening **trro fi.bcrs of vegetable pulp /¾nd molding them into a felt-like sheet, spraying an appropriate amount of water or an solution of preservative Λ material onto a surface of the sheet, applying pressure thereon, administering a similar treatment to the other surface, and then heating and drying the sheet.