Patent Application
20180064143
The current method of packaging perishable produce, such as Strawberries, Blueberries and Cucumbers, is typified by the use of flexible packaging or semi rigid containers that have macro perforations. A macro perforation is a hole or slot cut into the packaging material forming the package, which ranges in size from roughly ⅛″ to ⅜″. The holes are sized to allow air exchange in a way that is intended to regulate humidity.
Excess moisture in the package can lead to mold conditions.
The inventor recognizes optimizing the atmosphere within a sealed package of produce though the laser micro perforation of the packaging film can extend the shelf life of the produce well beyond that expected in current or standard packaging. An optimization of oxygen influx though the micro perforations balanced against the produce's respiration rate is carried out to find a balance between anaerobic conditions and aerobic respiration rates that cause excess moisture.
Air exchange to the package is used to remove the excess moisture in the package, since it was noted that the excess moisture can otherwise lead to mold conditions. However, the inventor found that too much air flow into the package, e.g., air flow meant to remove excess moisture, allows the produce to respire at higher levels. This respiration can also lead to spoilage.
The present application describes techniques to optimize this packaging of produce.
in the drawings:
FIGS. 6A1, 6A2 and 6B show pulsing oxygen production to the package.
The inventor found that the holes on conventional packages do not control the atmosphere in the package optimally. Conventional packages have used large perforations in the package, e.g., macro perforations that have allowed an abundance of available oxygen inside the package. This oxygen abundance allows the produce inside the package to continue respiration unimpeded. The unimpeded respiration generates an excess of water vapor that eventually condenses and gives rise to mold growth as well as burn the produce's energy reserves. This is because the inventor found that too much air flow, even though intended to remove the humidity, actually causes respiration of the produce in the package adding to even more water.
Techniques to determine the numbers and sizes of perforations, preferably micro perforations, are disclosed for three different kinds of produce (strawberries, Blueberries, and Cucumbers). However, techniques are also described herein for setting the numbers and sizes of the perforations for other produce.
The amount of oxygen that a micro perforation allows into a package is determined by the number of perforations, size of the perforation(s) and the relative concentration of oxygen inside and outside of the package. The amount of oxygen allowed into the package is referred to herein as the Oxygen Transmission Rate (OTR).
Measurement of this amount of oxygen is carried out by isolating a perforation and measuring the rate of increase of oxygen level in a sealed vessel though that perforation.
The relationship of the rate of transmission to the size of the perforation is nearly linear within the range that was found by the inventor to be practical with a laser drilling technique, namely 50 to 150 um. This relationship is based on a 100 um diameter orifice equated to an OTR of 150 cc/day/atmosphere and has a linear slope of 2 cc/day/atm per additional 1 um in diameter.
Samples of three different kinds of produce 316 (strawberries, Blueberries, and Cucumbers) were prepared to test increasing levels of OTR in different configurations; including no perforations (near zero OTR), micro perforations and macro perforations (near infinite OTR). Micro perforations are defined as holes cut thru the film via drilling and are normally in size of 50-600 microns in diameter, Macro perforations are defined as hole(s) cut thru the film via vector and are normally in a range of 600 microns to 6 mm in diameter.
Systems of the present invention are usable with either micro perforations or macro perforations. However, a preferred embodiment uses a micro perforation between 50 and 600 μm, and more preferably between 100 and 150 μm.
To determine if the available oxygen is too low and causing anaerobic respiration to occur, either or both of two sampling techniques can be employed to sample for an anaerobic condition at 400. The first technique tests the air within the package with a common alcohol detector. The detector can be located over a small hole in the packaging film. The package is then compressed, exhausting internal air onto the actively sensing probe. The pin hole is sealed after the sample is taken. A reading is recorded, with a positive reading indicating anaerobic conditions as evidenced by the presence of alcohol. In that case, the package's OTR design is concluded to be too restrictive. The most restrictive packages became anaerobic first and less restrictive OTR package later.
An alternative detection of an anaerobic condition can also be determined by an odor of the air within the package. Off odors, stale or musty, are indicators of anaerobic conditions. Either or both indicators would determine end of shelf life. This can be done using manual smell or using an electronic nose.
The condition of too high of an OTR design leading to an aerobic condition is determined visually by inspecting for mold at 410. Higher respiration rates, caused by excess of oxygen, generate water vapor faster than the produce can reabsorb. The subsequent condensation on the produce's surface is available to microbiological growth, typically mold. The appearance of mold determines the end of shelf life. Visual means of detecting mold include direct observation and time lapse photography. In one embodiment, a sample is being observed with relative ease and end of shelf life could be correlated with a time stamp of the compiled video.
The two limiting factors of shelf life: on the one hand too small OTR leading to anaerobic conditions, and on the other hand, too high OTR leading to aerobic respiration can be graphed as shown in
In the low OTR end of the spectrum, anaerobic conditions occur progressively as they build up CO2 concentrations and lower O2 levels. These conditions hinder the produce's ability to carry out aerobic respiration and create an environment that favors anaerobic microbiological growth.
In the high OTR end of the spectrum, Aerobic respiration generates high levels of moisture and creates an environment favorable to mold growth and consume the produce's energy reserves. Moisture accumulates more slowly in progressively lower OTR packages but eventually reaches the level where mold will occur.
The optimum OTR level is determined by the last package to reach either of these conditions, anaerobic conditions or mold growth, for any given size. This is referred to herein as the convergence point.
Too small OTR, as on the left side of the chart, e.g., less than 480 ml/day/package/atm, can produce a shelf life which is relatively small. The right side of the chart, where the OTR level is higher, shows significant amounts of air recirculation, leading to aerobic respiration. For example, this can also reduce the shelf life when the OTR for example in this chart is greater than 720-1500 mL per day per package per atmosphere. The ideal point, that is the point of convergence, is the peak of the curve. However, anywhere within 20% of the peak of the curve is considered ideal for purposes of this application. According to this embodiment, the package OTR is maintained between 480 and 720 ml/day/package/atm.
Note also, that different curves are shown in
The curve in
As explained herein, optimum OTR can be based on a number of different parameters, including the product type, and the product weight. For a specific variety of produce, the relative OTR level of a package as set according to the present techniques is designed for a specified amount of weight of produce within the package. The OTR level is effective as optimal as long as it is kept in proportion to the weight of the produce. During our experiment it was determined that 300 g of blueberries sealed in a tray with four 100 um holes were found to be optimal. For a package containing 750 g of blueberries; ten 100 um perforations, six 150 um perforations or thirty 50 um perforations would provide the optimal OTR level. However, all different product sizes and product weights and package sizes can be handled in the same way using the techniques described above to create the graph of
A few examples are provided herein: For 300 g of strawberries, four 100 um holes is optimum.
For 400 g of cucumbers two 100 um holes is optimum.
Holes are determined by size and number taking into account package's film's natural OTR in addition to the holes that are formed. Each packaging film has an OTR. Oxygen that diffuses though the film contributes to the available oxygen within the package for respiration.
The OTR for non-perforated packages is first calculated. A number of perforations are adjusted downward to achieve the optimum level of OTR while taking into account the OTR of the non-perforated packaging film. For example a package made of film that has an OTR value of 150 cc/day/100 in2/atm and a surface area of 200 in2 would transmit 300 cc of oxygen per day per atmosphere without perforations. The number of perforations would have to be reduced by two 100 um perforations, one 150 um perforation or six 50 um perforations below the optimum discussed above, in order to compensate for the additional oxygen available through the package's film.
More generally, however, a number of perforations is selected which maintains, for a given package size, volume and contents, a balance between aerobic conditions and anaerobic conditions.
According to the present application, the location of the holes is also important. Holes should be placed where they are least likely to be blocked by stacking packages or where the produce will press against them and block them. For example, in one embodiment, the holes can be placed in the top of the package at locations where they will still receive air even when stacked with other packages.
According to another embodiment, the package bottom can be slightly domed with a high point in its center so that the top package 260 sits on top of the bottom package but touches only at the tangent point between the domed package and the top part with recesses in the tangent point 265 to allow air to be exchanged with in the domed area. This has the effect of allowing air flow into the packaging, even when the packages are stacked. This embodiment is shown in
Temperature of the package can also be critical for determining the shelf life of the product. In an embodiment, the storage temperature of the package and produce is preferably maintained at the recommended level for that particular variety of produce in the testing described above to find the optimum OTR level that can be carried out at the recommended temperature. The respiration rate of the produce is affected by the temperature and is generally increased at a higher temperature within a range that does not damage the produce's viability. An OTR level design for refrigerated conditions has been found by the inventor to be less effective for temperature outside of that range for long periods of time. The ability of the produce to re-establish optimal oxygen levels once reintroduced to the designed for temperature is possible depending on the length and extreme of deviation, typically acceptable is several days at room temperature before returning to refrigerated temperatures.
Moisture or humidity control within the package is also used according to an embodiment. The use of moisture or humidity control can increase the shelf life of a product. Therefore, there will be a completely different curve set for the humidity controlled package.
In one embodiment, a moisture control device 230 with moisture driven automatic opening valve is used inside the package. This moisture control device can be, for example, the device described in our co-pending application Ser. No. 15/359,373, filed Nov. 22, 2016 the entire contents of which are herewith incorporated by reference. This moisture control device for example can use a satchel of desiccant, covered with a valve that is automatically opened and closed by the amount of humidity in the package. Excess moisture can open the valve, causing the moisture in the package to be absorbed by the desiccant. When the humidity goes below the valve set level, the valve is again closed. This can have the effect of controlling the humidity inside the package.
A moisture control device can have the effect of extending the optimal OTR level into the higher end of the spectrum. As the limiting factor of mold growth is pushed back from the convergence point of what was optimal, the number of days before the convergence point is reached is extended. This extension of the convergence point translates into extended shelf life.
In an alternative embodiment, the moisture control valve 230 can be located between the inside and outside of the package, and automatically opened by high humidity in the package to automatically vent the package. This allows regulated desiccant absorption so that the rate of moisture generated by respiration is regulated by the OTR level of the package.
The desiccant pack that is designed to absorb generated moisture near this known rate to maintain a level of humidity that limits condensation and mold growth. The rate of moisture absorption is designed by the packet that holds the desiccant. The packet's film is made of a film with a known Water Vapor Transmission Rate (WVTR). Given the area of the film forming the packet and the WVTR of that film, the desiccant packet operates to absorb the proper amount of humidity. Too much absorption dehydrates the produce and causes the desiccant to become saturated prematurely. Too little absorption and the higher humidity would lead to condensation and mold growth. Hence, the vented dessicant package can be an additional way of maintaining shelf life of the produce.
Another way of reducing humidity is by using High water vapor transmitting film as the film cover 205. A film such as Nylon or Cellulose has a high water vapor transmission rate that allows excess humidity to transpire and lower the internal package's humidity level. The perforation pattern may be changed if using this type of film.
Another way of reducing humidity is by using an Enhanced water vapor transmitting film 499 as shown in
Another embodiment of
Likewise, anaerobic microbiological growth is killed off when exposed to higher levels of oxygen. Given that these two conditions are met, the produce would be ready to endure another brief, timed exposure to anaerobic conditions. The number of times that a variety of produce can endure this cycle of aerobic/anaerobic conditions can be determined through trial. The amount of sugar or energy burned though respiration is much lower than even the best OTR burn rate. This would also reduce the amount of moisture produced by respiration. The extension of shelf life and quality of the produce could be greatly increased. Two different embodiments of exposing the produce to higher levels of oxygen, in order to extend the time until cellular death, are disclosed herein.
A valve that opens at timed intervals can be used, as shown in
An other humidity swelling, similar to the valve disclosed in Our Provisional application number 62331372 can be controlled though a printed circuit 630 that generates heat in a Nylon laminate by the resistance in the circuit portion 632. The heat dries the nylon thus shrinking it, which in turn “pulls” a flap open.
Another embodiment shown in
Opportunities to control humidity and extend shelf life are disclosed as an embodiment. An optimum package design can be carried out with the humidity reduction techniques.
Other embodiments are contemplated. For example, while the above embodiments have described specific materials, other materials could be included.
Those of skill would further appreciate that these features can be carried out using different materials and different techniques and different shapes.
Also, the inventor(s) intend that only those claims which use the words “means for” are intended to be interpreted under 35 USC 112, sixth paragraph. Moreover, no limitations from the specification are intended to be read into any claims, unless those limitations are expressly included in the claims.
Where a specific numerical value is mentioned herein, it should be considered that the value may be increased or decreased by 20%, while still staying within the teachings of the present application, unless some different range is specifically mentioned. Where a specified logical sense is used, the opposite logical sense is also intended to be encompassed.
The previous description of the disclosed exemplary embodiments is provided to enable any person skilled in the art to make or use the present invention. Various modifications to these exemplary embodiments will be readily apparent to those skilled in the art, and the generic principles defined herein may be applied to other embodiments without departing from the spirit or scope of the invention. Thus, the present invention is not intended to be limited to the embodiments shown herein but is to be accorded the widest scope consistent with the principles and novel features disclosed herein.
This application claims priority from provisional application No. 62/384,562, filed Sep. 7, 2016, the entire contents of which are herewith incorporated by reference.
| Number | Date | Country | |
|---|---|---|---|
| 62384562 | Sep 2016 | US |
