WO2015048655A1

WO2015048655A1 - Container having a molded pulp base and vented plastic lid for maintaining crispiness of moisture- sensitive foods

Info

Publication number: WO2015048655A1
Application number: PCT/US2014/058066
Authority: WO
Inventors: Thomas George Hart; Yohanan Siskindovich; Lionel PEÑA
Original assignee: Sabert Corporation
Priority date: 2013-09-27
Filing date: 2014-09-29
Publication date: 2015-04-02

Abstract

A container having a molded pulp base and a vented plastic lid. The molded pulp is formed by pressing a mixture of pulp material and liquid against a mesh screen, thereby forming the molded pulp with a screened side and a pressed side. The base has a bottom and a base sidewall forming an interior volume. The base further includes an edge extending from an upper portion of the base sidewall. The molded pulp is oriented so that the screened side of the molded pulp faces the interior volume. The lid has a top and a lid sidewall forming an interior volume. The lid includes a number of vents in a portion where the lid top meets the lid sidewall. The lid further includes an edge extending from a lower portion of the lid sidewall such that the lid edge rests on the base edge when the container is closed.

Description

CONTAINER HAVING A MOLDED PULP BASE AND VENTED PLASTIC LID FOR MAINTAINING

CRISPINESS OF MOISTURE-SENSITIVE FOODS

CROSS-REFERENCE TO RELATED APPLICATION

5 This application claims the benefit of U.S. Provisional Patent

Application No. 61/883,932, filed on September 27, 2013, entitled "Vented Container For Maintaining Crispiness of Moisture-Sensitive Foods," which is hereby incorporated by reference in its entirety.

10 FIELD OF THE INVENTION

The disclosed embodiments relate to a container having a molded pulp base and a vented plastic lid for maintaining crispiness of moisture-sensitive foods.

15 BACKGROUND OF THE INVENTION

Food retailers, such as grocery stores and delicatessens, may store portions of prepared foods, including hot foods, in containers for display and sale to customers. Such containers may also be used for takeout/delivered foods. Certain foods, especially crispy fried foods, e.g., French fries and fried

20 chicken, are sensitive to moisture, in the sense that moisture tends to decrease the crispiness of the food and may render it soft and soggy. This results in the food having a visual appearance and texture which is unappealing to customers.

The problem of maintaining food crispiness is especially acute for hot

25 foods, e.g., foods displayed in a container under a heat lamp, because steam emanating from hot food will remain trapped in the container and will have the effect of softening the food. The steam may also condense on the interior surfaces of the container. This, in turn, may result in moisture accumulating within the container, especially on the inside of the container lid. The

30 accumulated moisture may drip directly onto the food or drip around the walls of the container into the base of the container where the food is positioned.

SUMMARY OF THE INVENTION

In one aspect, the disclosed invention provides a container having a 35 molded pulp base and a vented plastic lid. The molded pulp is formed by pressing a mixture of pulp material and liquid against a mesh screen, thereby forming the molded pulp with a screened side and a pressed side. The container includes a base formed of the molded pulp, the base having a bottom and a base sidewall forming an interior volume. The base further includes an edge extending from an upper portion of the base sidewall. The molded pulp is oriented so that the screened side of the molded pulp faces the interior volume. The container has a lid formed of plastic, which has a top and a lid sidewall forming an interior volume. The lid includes a number of vents in a portion where the lid top meets the lid sidewall. The lid further includes an edge extending from a lower portion of the lid sidewall. The lid edge rests on the base edge when the container is closed.

Embodiments of the disclosed invention may include one or more of the following features.

The base edge may form a peripheral channel which opens in a downward-facing direction, and the lid edge may have a horizontal portion which rests on the peripheral channel when the container is closed. The lid edge may include a vertical outer portion which contacts an outermost portion of the base edge when the container is closed. The vertical outer portion of the lid edge may have at least one protrusion which creates an interference or snap fit with the outermost portion of the base edge to secure the lid to the base.

The vents may be vertically-oriented rectangular slots. A ratio of the container volume in milliliters to a total vent area in mm² may be between about 1.1 and about 3.3. Alternatively, the ratio of the container volume in milliliters to a total vent area in mm² may be between about 1.3 and about 2.2. Alternatively, the ratio of the container volume in milliliters to a total vent area in mm² may be between about 1.5 and about 1.9.

On each side of the lid, the vents may be positioned in two regions, the regions being located on both ends of each side of the lid and having a length of approximately one third of a length of each side of the lid. Within each of these regions, the vents may be positioned in a half of the region which is closer to a center of each side of the lid.

The pulp material may include at least one of bagasse, bamboo, wheat straw, wood, switch grass, and miscanthus grass. The bottom of the base may include protrusions which extend into the interior of the container, the protrusions being spaced apart to form grooves. The protrusions may have a height of between about 0.1 and about 0.5 inches and may be spaced apart by a distance of about 0.08 to about 1.5 inches. Adjacent ones of the protrusions may be joined by periodically-spaced structures so that the grooves do not extend continuously around the entire container.

BRIEF DESCRIPTION OF THE DRAWINGS

The above and/or other aspects and advantages will become more apparent and more readily appreciated from the following detailed description of the disclosed embodiments taken in conjunction with the accompanying drawings of which:

Fig. 1 is a perspective view of an embodiment of a container having a molded pulp base and a vented plastic lid for maintaining crispiness of moisture-sensitive foods;

Fig. 2 is a side view of the container in a closed state;

Fig. 3 is a top view of the vented plastic lid;

Fig. 4 is a perspective view of the molded pulp base;

Fig. 5 is a top view of the molded pulp base;

Fig. 6 is a side view of the molded pulp base;

Fig. 7 A is a cross-section of the molded pulp base;

Fig. 7B is an enlarged view of a portion of the sidewall of the molded pulp base depicted in Fig. 7A;

Fig. 7C is a further enlarged view of the portion of the sidewall of the molded pulp base depicted in Fig. 7B;

Fig. 8A is a first enlarged cross-section view of the fit between the lid edge and the base edge when the container is closed; and

Fig. 8B is a second enlarged cross-section view, taken in a different location, of the fit between the lid edge and the base edge when the container is closed showing a protrusion which creates an interference or snap fit with the base edge to secure the lid to the base.

DETAILED DESCRIPTION

Fig. 1 depicts an embodiment of a container 100 having a molded pulp base 1 10 and a vented plastic lid 120 for maintaining crispiness and temperature of moisture-sensitive foods. Fig. 2 is a side view of the container .

100 in a closed state, and Fig. 3 is a top view of the vented plastic lid 120. The molded pulp base is discussed below in connection with Figs. 4-6, 7A-7C, 8A, and 8B. The embodiment depicted in Fig. 1 is a square 9" by 9" container having a capacity of about 2200 ml. One use of this type of container is to store freshly-prepared, hot, crispy foods, such as fried chicken, for display under a heat lamp in a delicatessen or grocery store setting.

The lid 120 may be formed of plastic, e.g., high density polyethylene (HDPE), polypropylene (PP), or polystyrene (PS), and may be clear, translucent or opaque. The lid 120 has a top 125 and a sidewall 130 forming an interior volume. The top 125 may be flat with a flat center portion 127 which steps in the inward direction by about 0.11 inches. Alternatively, the top 125 may have an inwardly or outwardly protruding dome-shaped center portion. Other shapes are also possible. The lid 120 also has an edge 135 which extends from a lower portion of the lid sidewall 130. The lid edge 135 mates with a corresponding edge of the base 1 10 to close the container using a plurality of latching protrusions 820, as discussed in further detail below (see, e.g., Figs. 8A and 8B). It is also possible to use a single, continuous latching protrusion.

The lid 120 has a number of vents 140, e.g., 16 vents, arranged around the lid 120 in a portion of the lid sidewall 130 where it meets the lid top 125. The vents 140 may extend at least partially onto the lid top 125. The vents 140 may be rectangular, with dimensions, e.g., of about 0.53 inches by about 0.18 inches, and may be oriented with the longer dimension extending in the vertical direction. The vents 140 may have a half-circle portion 142, e.g., a portion having a radius of about 0.09 inches, at the top and/or bottom of the vent. The vents 140 may be spaced apart, e.g., by a distance of about 0.32 inches.

In the embodiments depicted in Figs. 1-3, each side of the lid 120 has four vents 140 - two near each corner. As noted above, the vents 140 may be positioned so as to be in the outer approximately one third of the length of each side of the lid 120 (i.e., each side of the lid sidewall 130). Within the outer one third of the length of each side of the lid 120, considering these sections to be divided in half (i.e., each half being about one sixth of the length of the side edge), the vents 140 may be positioned in the half closer to the center of the side edge in certain embodiments. In other embodiments, the vents 140 may be positioned in the half of the outer third which is closer to the corner. In other embodiments, the vents 140 may be positioned so as to be in the outer approximately one fourth of the length of each side edge of the lid.

As noted above, the embodiment depicted Figs. 1-3 has a total of sixteen vents 140. These vents, in combination, provide a ventilation opening defining a particular total area, i.e., a "vent area," of the lid. For example, assuming a vent size of 0.127 in² (82mm²), sixteen vents will provide a total vent area of 1311 mm². Of course, various other individual vent sizes are also possible.

The total area of all of the vents combined is a significant parameter, because if the total vent area is too large, then the container may allow heat to escape too readily, may allow foreign matter to enter the container too readily, and may compromise the structural integrity of the lid. If the total vent area of all of the vents is too small, then the lid may not effectively vent moisture so as to avoid a deterioration of the crispiness of the food.

The total vent area is considered in relation to the volume of the container (i.e., the combined volume of the tray and lid), because containers of greater volume will have a greater volume of moist air to vent. In other words, for a specific container, there will be a particular volume of moist air to be vented through a particular total vent area. For example, if the volume of the container is 2184 ml and sixteen vent vents of 0.127 in² (82mm²) are used, then the ratio of container volume (ml) to total vent area (mm²) would be about 1.7 (see table below). A desired total vent area may be achieved by changing the number of vents or the size of the individual vents. The individual vents need not have the same area - vents of varying size may be used. For example, it may be desirable to gradually decrease the size of the vents as they approach the corners of the container.

The following table presents a calculated ratio of container volume to total vent area for an embodiment in which the container has a total interior volume of 2184 ml and each individual vent defines an area of 0.127 in² (82mm²).

164 2 13.33

246 3 8.89

328 4 6.66

410 5 5.33

492 6 4.44

574 7 3.81

655 8 3.33

737 9 2.96

819 10 2.67

901 11 2.42

983 12 2.22

1065 13 2.05

1147 14 1.90

1229 15 1.78

1311 16 1.67

1393 17 1.57

1475 18 1.48

1557 19 1.40

1639 20 1.33

1721 21 1.27

1803 22 1.21

1885 23 1.16

1966 24 1.11

2048 25 1.07

2130 26 1.03

2212 27 0.99

2294 28 0.95

2376 29 0.92

2458 30 0.89

2540 31 0.86

2622 32 0.83

As a result of the design, development, and testing process of the disclosed embodiments, the inventors have found that a ratio of the container volume in milliliters to a total vent area in mm² of between about 1.1 and about 3.3 maintains the freshness and crispiness of moisture-sensitive, crispy prepared foods and provides unexpectedly good results vis-a-vis conventional containers. This range has been found to reduce condensation within the container, which may make the food soggy, and to reduce the breakdown of volatile compounds which are produced in the cooking process and which are indicative of freshness. At the same time, this ratio range avoids over ventilation, which may lead to the prepared food getting cold too soon and other problems. Furthermore, the inventors have found that a ratio of the container volume in milliliters to a total vent area in mm² of between about 1.3 and about 2.2 is preferable. Moreover, a ratio of between about 1.5 and about 1.9 is more preferable. The parameters which may be used in assessing the effectiveness of a container in maintaining the freshness and crispiness of foods are discussed below in connection with certain comparison testing which was performed.

Fig. 4 shows an embodiment of the base 1 10 of the container 100, which is formed of molded pulp. Fig. 5 is a top view, and Fig. 6 is a side view of the base 10. The base 1 0 has a bottom 405 and a sloped sidewall 410 forming an interior volume. In this example, which is square in shape, the sidewall 410 is a four-sided structure. Other shapes for the container are also possible, such as, for example, round or rectangular. The base 110 has an edge 415 which extends from an upper portion of the base sidewall 410. The base edge 415 may form a peripheral channel which opens in a downward-facing direction (see, e.g., Fig. 7A, discussed below).

The base 1 10 may have protrusions 420 formed on a bottom surface thereof which extend upward into the interior of the container to form raised structures to keep the food elevated from the bottom surface 405 of the base 110. Alternatively, the protrusions may extend outward from the bottom of the base. In either case, the protrusions may be formed as concentric rows of a square-shaped pattern with space in between, thereby forming grooves 425 (which are depicted with concentric contour lines in the drawings of the present application solely for the purpose of illustration to show that these structures have depth), and thus a reservoir, in which liquid may accumulate.

For example, protrusions 420 extending into the interior of the container 100 may have a height of about 0.1 inches and may be arranged to form grooves 425 between the protrusions 420 of about 0.3 inches in width. The adjacent protrusions 420 may be joined by periodically-spaced structures 430 (see, e.g., Fig. 5), thereby ensuring that the grooves 425 do not extend continuously around the entire container. This arrangement of the protrusions 420 and periodically-spaced structures 430 helps to prevent sloshing of the liquid accumulated in the grooves 425 and also provides structural strength to the bottom 405 of the base 110.

The protrusions 420 help keep the food from coming into contact with moisture, liquid, and/or oils which may be present in the bottom 405 of the container. The liquid or oils may come from the food itself, i.e., may be food drippings, and/or may be the result of condensation of moisture on other inside surfaces of the container 100 which drips down into the base 110. Keeping the moisture and/or liquid separate from the food helps keep the food from getting soft and soggy and losing its crispiness.

Fig. 7A is a cross-section of the molded pulp base 110, which shows that the base 1 10 has an edge 415 (e.g., a rim), which curls over at its outermost edge. This helps to maintain the shape of the base 110 by forming a stiff edge. The cross-sectional view also shows the protrusions 420 on the flat bottom surface 405 of the base 1 0. In this example, the protrusions 420 extend from the bottom 405 of the base 110 and, hence, form grooves 425 on the bottom surface 405 of the base 1 10.

Fig. 7B is an enlarged view of a portion of the sidewall 410 of the molded pulp base 1 10 depicted in Fig. 7A, and Fig. 7C is a further enlarged view of the portion of the sidewall 410 of the molded pulp base 110 depicted in Fig. 7B.

The base 1 10 of the container 100 is formed of pulp which has undergone a pressing and molding process. The pulp may be formed of various fibrous materials, such as, for example, bagasse, bamboo, wheat straw, wood, switch grass, and miscanthus grass, and other natural fibrous material. The pulp is processed by pouring a suspension of pulp material and liquid (e.g., water) into a mold having a cavity with a number of holes and which is covered with a very fine mesh. The liquid is suctioned away, and the collected fibers on the mesh are pressed between two corresponding heated molds to squeeze out additional liquid. In further steps, additional pressing and heat processes may be applied to form and dry the final parts.

As shown in Figs. 7B and 7C, the pulp material which forms the base 110 has a rough, textured surface 710 facing the interior volume of the base. The rough surface 710 may be formed during the pulp material fabrication process. In that process, as noted above, liquid is pressed out of a liquid/pulp mixture by a pressing member which applies mechanical force to squeeze the mixture against the mesh screen. The resulting material is dried to form a stiff, fibrous material.

The side of the pulp material which was facing the mesh screen (i.e., rough surface 710) ends up with a rough surface texture, which faces the interior of the container, in this example (i.e., the top surface in Figs. 7B and 7C). This side of the pulp material (i.e., rough surface 710) may be referred to as the "screened side." The rough surface 710 of the screened side creates a greater surface area for liquids and oils from food to spread over and helps remove it from direct contact with the food. Furthermore, the pulp material is somewhat absorbent. Therefore, a portion of the liquids and oils will be absorbed by the base.

The opposite side of the pulp material 720 is the side which is pressed by the pressing member in the pulp material fabrication process. This side of the pulp material (i.e., outside surface 720) may be referred to as the "pressed side." The outside surface 720 of the pulp material may be smooth and may be laminated, e.g., with a polymer lamination. The application of lamination helps keep liquid and oils from seeping out of the container over time, thereby helping to prevent the appearance of unsightly wet spots on the outer surface of the container and also helping to prevent possible soiling of the customer's hands and staining of the customer's clothing. The laminated surface also helps to maintain heat within the container.

Figs. 8A and 8B show enlarged cross-section views of the fit between the lid edge 135 and the base edge 415 when the container is closed. The base edge 415 may form a peripheral channel which opens in a downward-facing direction. The lid edge 135 may have a horizontal portion 805 which rests on the peripheral channel (i.e., base edge 415) when the container is closed. The lid edge 135 may also have a vertical outer portion 810 which contacts an outermost portion 815 of the base edge when the container is closed.

As shown in Fig. 8B, the vertical outer portion 810 of the lid edge 135 has at least one protrusion 820 which creates an interference or snap fit with the outermost portion 815 of the base edge 415 to secure the lid 120 to the base 110. For example, the lid 120 may have several protrusions 820 positioned at intervals around its periphery, e.g., eight protrusions, with one on each side and at each corner of the container (see, e.g., Figs. 1 and 2). Alternatively, there may be a single protrusion which extends around the entire periphery of the container.

As noted above, one common use of the disclosed embodiments is to store freshly-prepared fried chicken for display under a heat lamp, e.g., in a delicatessen or grocery store setting. The testing described below has shown that the disclosed embodiments provide unexpectedly good results with respect to conventional container designs.

There are certain characteristics which are indicative of the crispiness and freshness of fried chicken. More specifically, the consumer's sensory experience of fried chicken is produced on two levels. The first is the textural level, which is determined by moisture content and called "crispy" in layperson's terms. The second is the olfactory level, which is determined by the production of certain volatile compounds in the cooking process which affect the consumer's senses of taste and smell. Thus, there are two important factors in producing the desirable sensory experience of crispy fried chicken: (i) the moisture level of the fried chicken; and (ii) the production of volatile compounds which give the fried chicken its distinctive flavor and aroma.

To evaluate the venting configurations disclosed herein, testing was performed to evaluate moisture and volatile compound levels in fried chicken stored in a container for a fixed period of time. Two containers were used in these tests: "Container A," which was a container with a pulp base and vented lid in accordance with the main embodiment described herein; and "Container B," which was a container of the same length and width (i.e., square, measuring 9" by 9"), but somewhat taller and thus having a volume of 2595 ml, compared to 2184 ml for Container A. Container B had a plastic base and a plastic lid with a single, 3/8" long "C"-shaped vent in one corner of the lid.

A moisture level test was done by standard moisture analysis through oven drying. The tests showed both Containers A and B retained a moisture level after 30 minutes approximately the same as when freshly fried chicken was placed in the respective containers.

The following is a discussion of the scientific basis for the test for volatile compounds relating to sensory characteristics. The consumer's olfactory experience occurs on three main levels: taste (i.e., gustation), odor (i.e., orthonasal perception), and aroma (i.e., retronasal perception). Chemical compounds, in particular, volatile compounds, are responsible for these sensory experiences. These compounds are also the primary indicators of rancidity, i.e., they are indicative of the degree to which a food substance decayed since "time zero." Time zero corresponds to the moment when the prepared food is considered to be at its "freshest," i.e., just prepared. In general, rancidity occurs due to either hydrolysis or oxidation of the bonds that hold together fatty acids, which causes new volatile compounds to be formed. These new volatile compounds are experienced by the consumer as "off flavors," i.e., the food no longer retains its "just cooked" taste.

One method for the measurement of rancidity is gas-liquid chromatography (GLC) analysis of volatiles, isolated by the dynamic headspace analysis. Over 130 volatile compounds exist in fried chicken. For the testing purposes, three compounds were considered that have been shown to be prevalent in fried chicken: t,t,-2,4-decadienal, 2-furanmethanol, 2,4-heptadienal. These compounds are created directly from frying and are not present until frying has occurred. Their creation is the result of hydrogen and oxygen molecule exchange between the lipids and carbohydrates of the chicken and the lipids which make up the frying oil. The presence of heat allows these reactions to take place. The methods used to test the disclosed embodiments were based on known procedures for extracting volatile compounds from fried chicken.

Two of the compounds, t,t,-2,4-decadienal, 2-furanmethanol, were considered because they are strong indicators of a fresh fried chicken taste. However, a third compound, 2,4-heptadienal, was chosen as the key indicator for the testing described herein because of its relatively delicate nature. In particular, due to autoxidizing nature of this compound, it can be used to detect small changes which might not have been detectable with the other two compounds, t,t,-2,4-decadienal and 2-furanmethanol, which are more stable.

The presence of 2,4-heptadienal is an indicator of freshness of the fried chicken and will degrade quickly in the presence of oxygen. Ambient air flow will cause the compound to breakdown and, therefore, it is a good indicator of air flow in packaging. The presence too much, or too little, oxygen will cause . the 2,4-heptadienal to break down or form new compounds (e.g., compounds which produce "off flavors) more rapidly. In either case, the presence of

2,4-heptadienal will decrease rapidly until it is no longer detected by the consumer. Therefore, it can be concluded that maintaining the proper amount of airflow has a direct effect on the survival of 2,4-heptadienal in the container and this, in turn, has a direct effect on the customer's perception of freshness of the food stored in the container.

The purpose of this study was to examine how well different types of take-out food containers could preserve the freshness in crispy food, in particular, fried chicken, both in terms of moisture level and volatile compounds. The time was 30 minutes in the enclosed container.

It was shown that the container with the molded pulp base and vented plastic lid, i.e., Container A, had a 20% (± 2%) greater ability to retain

2,4-heptadienal than the all plastic container with a single vent, i.e., Container B. It can be concluded from previous studies in 2,4-heptadienal and the rate of its oxidation that the ability of the container to retain the compound was a direct result of having the proper amount of airflow.

The testing discussed above showed that Container A, i.e., the container of the main disclosed embodiment, has unexpectedly good ability to keep fried chicken at its peak freshness. Further testing was performed to determine the effect of a pulp base versus a plastic base vis-a-vis the ability of the container to maintain the freshness of crispy foods, e.g., fried chicken.

Two containers were used in the second set of tests: "Container A," which, as discussed above, was a container with a pulp base and vented lid in accordance with the main embodiment described herein; and "Container C," which was a container of the same size and volume as Container A and having a plastic lid with vents in the same arrangement as Container A, but having a plastic base instead of a pulp base.

As noted above, the presence of 2,4-heptadienal is an indicator of freshness of the fried chicken. The presence of too much, or too little, oxygen will cause the compound to break down or form new compounds. Many of these compounds are responsible for the "off flavors associated with stale food.

The following conclusions were reached in this further testing: 1) a pulp (i.e., cellulose mixture) base retards oxidation of important volatile compounds better than a plastic base;

2) a pulp base is better at preventing sogginess than a plastic base; and

3) based on a comparison of results for a plastic base with bottom grooves versus a flat plastic base, it was concluded that the bottom grooves aid in retarding volatile compound oxidation.

With respect to the first conclusion, it is noted that the molded pulp base of Container A is made with a combination of cellulose and other elements. When the lipids, protein and carbohydrates from the raw breaded chicken interact with the lipids of edible oil (e.g., corn oil, vegetable oil, etc.) through the catalyst of heat, specific volatile compounds are formed. Studies have shown that cellulose can help prevent the oxidation of volatile oils. The testing showed that the pulp base packaging (i.e., Container A) had an average decrease in 2,4 Heptadienal of 10.9% compared to the control, whereas the plastic base packaging (i.e., Container C) had an average decrease of 17.49% compared to the control.

With respect to the second conclusion, it was shown through moisture analysis that a container with a plastic base (i.e., Container C) compared to a container with a pulp base (i.e., Container A), was not as effective in keeping moisture from pooling or condensing. While the moisture levels in the container with the pulp base declined to a drier state, the moisture levels in the container with the plastic base showed signed of water retention.

Crispiness of foods has been shown to be directly associated with moisture. A hypothesis behind these results is that plastic is hydrophobic and therefore allows water to pool. When steam from hot crispy food, e.g., fried chicken, contacts the plastic lid, it condenses and precipitates onto the food and the base of container, due to the hydrophobic nature of plastic. Since the plastic base is also hydrophobic, the hydrogen and oxygen molecules of the water have nowhere to be exchanged, and so begin to become re-absorbed in the crispy food, e.g., in the breading of the fried chicken, which is hydrophilic because it is a carbohydrate. However, in a container having a pulp base, which is partially composed of cellulose, water exchange can occur. Therefore, moisture that would have been absorbed by the food is instead absorbed by the packaging, which helps prevent the crispy food from becoming soggy. With respect to the third conclusion, the test results showed that a plastic base container with grooves (i.e., Container C) was 8.3% better at preventing oxidation than the plastic base with a flat bottom (i.e., Container B, discussed above). Furthermore, the flat-bottomed container had an average decrease of 23% for 2,4-heptadienal. As noted above, proper air flow is important to maintain the stability of volatile compounds, such as 2,4-heptadienal. The groves improve air flow by allowing channels of air to flow underneath the crispy food to help avoid the creation of an environment in which air cannot properly circulate in the interior of the container.

The conclusion drawn from these results is that a container having a molded pulp base with grooves (i.e., Container A) provides unexpectedly good results in preventing the breakdown of volatile compounds which are indicative of freshness. These results arise from, inter alia, the following two factors: (i) the use of pulp material to form the base; and (ii) the providing of grooves on the bottom of the container to raise the crispy food above the flat bottom of the container. With respect to the first factor, the pulp material, as noted above, contains cellulose, which helps prevent the oxidation of volatile compounds which make up edible oils. With respect to the second factor, the bottom grooves elevate the stored crispy food and help ensure proper airflow in the interior of the container. This, in turn, slows the rate of volatile compound oxidation and rancidity. Both of these factors work in conjunction to keep the crispy foods, e.g., fried chicken, in a state of freshness and crispiness.

Although example embodiments have been shown and described in this specification and figures, it would be appreciated by those skilled in the art that changes may be made to the illustrated and/or described example embodiments without departing from their principles and spirit.

Claims

What is claimed is:

1. A container having a molded pulp base and a vented plastic lid, the molded pulp being formed by pressing a mixture of pulp material and liquid against a mesh screen, thereby forming the molded pulp with a screened side and a pressed side, the container comprising:

a base formed of the molded pulp, the base having a bottom and a base sidewall forming an interior volume, the base further comprising an edge extending from an upper portion of the base sidewall, the molded pulp being oriented so that the screened side of the molded pulp faces the interior volume; and

a lid formed of the plastic, the lid having a top and a lid sidewall forming an interior volume, the lid comprising a plurality of vents in a portion where the lid top meets the lid sidewall, the lid further comprising an edge extending from a lower portion of the lid sidewall, wherein the lid edge rests on the base edge when the container is closed.

2. The container of claim 1 , wherein the base edge forms a peripheral channel which opens in a downward-facing direction, and the lid edge comprises a horizontal portion which rests on the peripheral channel when the container is closed.

3. The container of claim 2, wherein the lid edge comprises a vertical outer portion which contacts an outermost portion of the base edge when the container is closed.

4. The container of claim 3, wherein the vertical outer portion of the lid edge has at least one protrusion which creates an interference or snap fit with the outermost portion of the base edge to secure the lid to the base. 5. The container of claim 1 , wherein the vents are vertically-oriented rectangular slots.

6. The container of claim 5, wherein the rectangular slots have rounded ends.

7. The container of claim 1 , wherein a ratio of the container volume in milliliters to a total vent area in mm² is between about 1.1 and about 3.3.

8. The container of claim 1 , wherein a ratio of the container volume in milliliters to a total vent area in mm² is between about 1.3 and about 2.2.

9. The container of claim 1 , wherein a ratio of the container volume in milliliters to a total vent area in mm² is between about 1.5 and about 1.9. 10. The container of claim 1 , wherein, on each side of the lid, the vents are positioned in two regions, the regions being located on both ends of each side of the lid and having a length of approximately one third of a length of each side of the lid. 11. The container of claim 10, wherein within each of the regions, the vents are positioned in a half of the region which is closer to a center of each side of the lid.

12. The container of claim , wherein the pulp material comprises at least one of bagasse, bamboo, wheat straw, and wood, switch grass, and miscanthus grass.

13. The container of claim 1 , wherein the bottom of the base comprises protrusions which extend into the interior of the container, the protrusions being spaced apart to form grooves. 4. The container of claim 3, wherein the protrusions have a height of between about 0.1 and about 0.5 inches and are spaced apart by a distance of about 0.08 to about 1.5 inches.

15. The container of claim 13, wherein adjacent ones of the protrusions are joined by periodically-spaced structures so that the grooves do not extend continuously around the entire container.