DYNAMIC MODIFIED ATMOSPHERE PACKAGING MATERIAL FOR FRESH HORTICULTURAL PRODUCTS

Abstract

The present invention relates to the use of a sheet for extending shelf-life of biological products, wherein the sheet comprises or consists of a thermoplastic composition with a hydrophobic polymer phase comprising at least one hydrophobic polymer; a hydrophilic polymer phase comprising at least one hydrophilic polymer; and optionally at least one compatibiliser.

Claims

1. A method for extending shelf-life of at least one biological product comprising: providing a sheet for packaging the at least one biological product; and dynamically modifying an atmosphere surrounding the at least one biological product in response to one or more of 1) the biological activity of the at least one biological product, 2) the storage temperature, and 3) the relative humidity in the direct surrounding of the at least one packaged biological product, thereby extending shelf-life of the at least one biological product, wherein the sheet comprises or consists of a thermoplastic composition with: a hydrophobic polymer phase having a water absorption capacity of at most 5 ml water per 100 g of the at least one hydrophobic polymer phase; a hydrophilic polymer phase having a water absorption capacity of at least 5 ml water per 100 g of the at least one hydrophilic polymer phase; and optionally at least one compatibiliser.

2. The method according to claim 1, further comprising maintaining a controlled atmosphere surrounding the at least one biological product, wherein the concentration of CO.sub.2 is kept between 0 and 10 vol. % and/or the concentration of O.sub.2 is kept between 0 and 10 vol. %.

3. The method according to claim 1, wherein the biological product contains at least 1, 5, 10, 20 or 40 wt. % living biological cells and/or is chosen from the group consisting of fruit, vegetable, and/or flower.

4. The method according to claim 1, wherein the at least one hydrophobic polymer phase has a water absorption capacity of at most 4, 3, 2, 1, 0.5, 0.4, 0.3, 0.2, or 0.1 ml water per 100 g of the at least one hydrophobic polymer phase and/or wherein the at least one hydrophobic polymer is chosen from the group consisting of fossil-based polymer, biopolymer, polyester, polyolefin, preferably polyethylene.

5. The method according to claim 1, wherein the at least one hydrophilic polymer phase has a water absorption capacity of at least 10, 20, 30, 40, or 50 ml water per 100 g of the at least one hydrophilic polymer and/or wherein the at least one hydrophilic polymer is a carbohydrate or a protein, preferably chosen from the group consisting of wheat gluten, chitosan, pullulan, pectin, myofibrillar protein, and starch, preferably thermoplastic starch.

6. The method according to claim 1, further comprising at least partially covering the at least one biological product with the sheet during a period having a temperature variation of at least 4° C. and/or a relative humidity variation of at least 4%, wherein preferably the temperature variation during the period is at least 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 20 or 25° C. and/or wherein the relative humidity variation during the period is at least 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 20, 25, 30, 35, 40, 45, or 50%.

7. The method according to claim 1, wherein the period during which the at least one biological product is packaged is at least 4, 6, 8, 10, 12, or 14 days and/or wherein the method is during transport.

8. The method according to claim 1, wherein the sheet at least partially defines an outer surface of a controlled atmosphere that at least partially surrounds the at least one biological product, preferably wherein the sheet defines between 1-100%, 1-80%, 1-60%, 1-40%, 1-20%, 20-100%, 40-100%, 60-100%, or 80-100% of said outer surface.

9. The method according to claim 1, wherein the sheet contains between 1-50, 1-25, 1-10, 40-80, or 50-90 wt. % of the hydrophilic polymer; and/or wherein the thickness of the sheet is between 1-50 μm, 5-40 μm, 5-30 μm, 40-70 μm, 50-100 μm, or 70-100 μm.

10. The method according to claim 1, wherein the sheet is an in at least one direction stretched sheet obtained by blowing, casting or stretching the thermoplastic composition in a machine direction and a transverse direction at elevated temperature and/or wherein the sheet has a layered morphology preferably with an internal layer comprising of the thermoplastic composition and/or one or two outer layer(s) comprising of thermoplastic composition, preferably hydrophobic polymer phase having a water absorption capacity of at most 5 ml water per 100 g of the at least one hydrophobic polymer phase, wherein preferably the at least one hydrophobic polymer is chosen from the group consisting of fossil-based polymer, biopolymer, polyester, polyolefin, and preferably polyethylene.

11. The method according to claim 1 wherein the thermoplastic composition comprises between 10-80 wt. % of the at least one hydrophobic polymer; between 10-80 wt. % of the hydrophilic polymer; and/or between 1-40 wt. % of the at least one compatibiliser.

12. The method according to claim 1, wherein the compatibiliser is a block or graft copolymer, nonreactive polymer containing polar groups or reactive functional polymer, preferably chosen from the group consisting of ethylene vinyl acetate copolymers, partially hydrolysed and saponified polyvinylacetate, polyolefins having at least 1 wt. % maleic anhydride grafted thereon, ethylene vinyl alcohol copolymers, ethylene acrylic acid copolymers, random terpolymers of ethylene, butylacrylate and maleic anhydride or mixtures thereof.

13. The method according to claim 1, wherein the thermoplastic composition further comprises a thermoplastic polyester, preferably poly(butylene terephthalate-co-adipate) in an amount of between 20-60 wt. %.

14. The method according to claim 1, further comprising extending and/or postponing a ripening process of the at least one biological product.

Description

BRIEF DESCRIPTION OF THE FIGURES

[0134] FIG. 1: CO.sub.2 and O.sub.2 concentration (vol. %) within three different packaging bags with Conference pears after 5 days at 8° C. (t1), or after 5 days at 8° C.+5 days at 18° C. (t2). Bag A: Macro-perforation bags; Bag B: Micro-perforation bags; Bag C: Starch based bags. Light grey: oxygen content (%), darker grey: carbon dioxide content (%). Standard deviation, (N=5).

[0135] FIG. 2: Oxygen concentrations were measured in packaging materials according to the disclosure and a reference material, on day 0, 2, 5, 7, and 9 upon packaging pears.

[0136] FIG. 3: Carbon dioxide concentrations were measured in packaging materials according to the disclosure and a reference material, on day 0, 2, 5, 7, and 9 upon packaging pears.

[0137] FIG. 4: Oxygen concentrations were measured in packaging materials according to the disclosure and a reference material, on day 0, 2, 5, 7, and 9 upon packaging mushrooms.

[0138] FIG. 5: Carbon dioxide concentrations were measured in packaging materials according to the disclosure and a reference material, on day 0, 2, 5, 7, and 9 upon packaging mushrooms.

[0139] FIG. 6: Photos showing mushroom quality after 5 days at 5 degrees Celsius and 4 days at 18 degrees Celsius, packaged in packaging materials according to the disclosure and a reference material.

EXAMPLE 1

[0140] Production of Starch/Polyethylene Film

[0141] Manufacturing of the hydrophilic/hydrophobic film is performed in 2 steps: [0142] 1. production of a thermoplastic composition with a hydrophilic polymer phase, a hydrophobic polymer phase and a compatibilizer [0143] 2. production of a film out of the thermoplastic composition

[0144] ad 1: A powder/fluid mixture comprising: [0145] 32.15% native potato starch (type Emsland Superior; 17% moisture content) (=hydrophilic polymer) [0146] 1.2% borax (type: Borax 10H2O GR Turkey obtainable from Brenntag) [0147] 1.2% fatty acid mixture (type Radiacid 0436, obtainable from Oleon) [0148] 0.6% glycerol mono stearate (type Radiasurf 7142 GMS, obtainable from Oleon) [0149] 0.24% sodium carbonate (type sodium carbonate anhydrous light Food (E500i) from Brenntag) [0150] 27.3% glycerol (type glycerine vegetable Pharm. (E422), obtainable from Brenntag) [0151] 32.76% LDPE (type Sabic LDPE 2008TN00) (=hydrophobic polymer) [0152] 4.55% compatibilizer (type Lotader 3410, obtainable from Arkema)

[0153] was compounded on a Berstorff ZE 40 A*38 D twin screw extruder equipped with a GALA LPU underwater pelletizer. Temperature profile along the barrel was: zone 1: 25° C.; zone 2: 60° C.; zone 3: 135° C.; zone 4: 160° C.; zone 5: 160° C.; zone 6: 160° C.; zone 7: 110° C.; zone 8: 95° C.; LPU: 120° C. Screw speed was 225 rpm. Total throughput was 26 kg/h. The compound was pelletized with help of the underwaterpelletizer (pellet size was about 4 mm) and dried to a moisture content of 3.7%.

[0154] Ad 2: Starch/LDPE compound was processed into a symmetrical 3 layer film with help of a BFA/Battenfeld coextrusion multilayer (max=5) film blowing machine. Machine consisted out of a Battenfeld UNI-Ex 1-45-25B (central layer) and a BFA 30-25 extruder (for both coating layers) attached to a Battenfeld BK 50/150-05 multi spiral mandrel die. Central layer consisted out of the pelletized material as described under Ad 1. Both coating layers consisted out of a dry blend of 60% Sabic LDPE 2404, 30% Sabic LLDPE 6318 and 10% Lotader 3410. Layer distribution was: coating/central layer/coating=25/50/25. Processing temperatures was about 130° C. for the central layer and 145° C. for both coating layers. Total throughput was 18 kg/h. Film thickness was about 55 micron. Stretch ratio in transverse direction is between 3 and 4. Stretch ratio in machine direction is between 8 and 9.

[0155] Pear Packaging Tests

[0156] The pear packaging tests were repeated two times: one time in 2016 and one time in 2017. In both cases, Dutch conference pears were used. These pears were first stored for a period of 6 months at low temperature (−0.5° C.) and under control atmosphere conditions, followed of 6 weeks of transport simulation (at −0.5° C. under atmospheric gas conditions). Both experiments showed clear advantage of the starch-based foils compared to the reference pears (non-packed or with macro-perforation) and/or packed in packaging with micro-perforation.

[0157] 1.sup.st Test:

[0158] Once the pears were packed, they were stored 5 days at 8° C. followed of 6 days at 18° C. The reference (ref) treatment consisted BOPP (biaxially oriented polypropylene) film with two macro-perforation (7 mm diameter, 19*21 cm). The micro-perforation treatment (bag 2) was made with bag of BOPP material (30 μm thick, 19*21 cm) with 8 micro-perforations per bag (100 μm diameter). The starch-based packaging (bag 3) was made of similar dimension: 19×21 cm (total film area: 800 cm.sup.2). All the bags were closed on day 0 with atmospheric gas (20.8% O2 and 0% CO2).

TABLE-US-00001 TABLE 1 Quality attributes of pears after unpacking Firmness (kg) Colour (1-4) ref 1.11 ± 0.07 3.44 ± 0.05 bag 2 1.56 ± 0.12 2.69 ± 0.04 bag 3 3.58 ± 0.36 2.63 ± 0.07

TABLE-US-00002 TABLE 2 Headspace composition of used packaging films Carbon Oxygen dioxide (%) (%) ref 20.4 0.44 bag 2 14.8 5.58 bag 3 1.4 5.73

[0159] In the bag 3 (starch-based film), the oxygen content was lower and the carbon dioxide content was limited to 5.73% (Table 2), which content did not cause any internal quality damages. Thanks to this modified atmospheric gas conditions, the pears packed in starch-based foil stayed firmer (3.58 kg versus 1.11 and 1.56 kg for reference film and micro-perforated film respectively) and remained more green(Table 1).

[0160] 2.sup.nd Test:

[0161] In pear packaging tests, fresh pears were packed in different sheets (bags) and stored for a period of 5 days at 8° C., or after 5 days at 8° C.+5 days at 18° C., in order to simulate real chain distribution conditions (increased temperature at the end of the storage time).

[0162] The three different packaging bags were (1) Control Macro, (2) BOPP Micro, and (3) starch/polyethylene film. Bags dimensions: 18 cm*22 cm. Macro: BOPP material with 2 macro-perforation of 7 mm diameter (hand-made). Micro: BOPP material with 2 laser micro-perforations of 100 μm diameter (micro-perforation made with Perfotec equipment. BOPP film (rol) were purchased by Van der Windt. Bags were hand made with a seal bar instrument.

[0163] The gas composition within the packaging and the product quality were measured over time (Checkmate 2 from Dansensor, Ringsted, DK). Gas was analysed by sampling approximately 10 mL of headspace volume and analysed with Checkmate 2 instrument. Sampling was made with a needle through a rubber septum to avoid leakage during and after measurement.

[0164] FIG. 1 depicts the gas composition in the headspace of different packages (bags) 5 days at 8° C., or after 5 days at 8° C.+5 days at 18° C.

[0165] Interestingly, the carbon dioxide concentration did not increase significantly in the starch/polyethylene—based packaging when the temperature increased from 8 to 18° C. The gas composition remains stable in the starch/polyethylene-based packaging, whereas in the BOPP packaging the carbon dioxide concentration more than doubled when the temperature increased by 10° C.

[0166] Table 3 shows that the firmness of the pears is better maintained in the starch-based bag (bag 3).

TABLE-US-00003 TABLE 3 Firmness (in kilogram) of pears packed in macro-perorated bag (bag 1), in micro-perforated bag (bag 2) and in starch-based bag (bag 3) on day 0, after 5 days at 8° C. and after 5 day at 8° C. followed by 5 days at 18° C. 5 days at 8° C. + day 0 5 days at 8° C. 5 days at 18° C. bag 1 5.1 ± 0.1 3.7 ± 0.2 1.01 ± 0.03 bag 2 5.1 ± 0.1 4.5 ± 0.2 2.9 ± 0.2 bag 3 5.1 ± 0.1 5.0 ± 0.2 4.1 ± 0.2

[0167] Application in Green Bananas

[0168] Nowadays green bananas are exported from South America to Europe in controlled atmosphere (CA) reefer containers or within MAP bags called Banavac. Banavac is a polyethylene bag with two micro-perforations. Using the respiration rate of the green banana, a modified atmosphere condition is created inside the bag. The low oxygen and high carbon dioxide levels inside the bag avoid the ripening process to occur during the shipping of the green banana. When green bananas are transported under CA conditions, the setting of the reefer container unit is fixed top 13.5° C., with 2-5% O.sub.2 and 2-5% CO.sub.2. The present starch based film can be used to pack green banana. When banana would be packed under more or less dry conditions, the oxygen and carbon dioxide content reach their optimal levels faster than within Banavac bag. After transport and prior ripening, an increasing of storage temperature (from 13,5 to 22° C.) will automatically raise up the relative humidity around the banana. This results in a higher permeability rate of the starch-based bag and so will allow higher exchange of oxygen and carbon dioxide between the bag headspace and the exterior. This allows the ripening process to start. It can be expected that no additional handling around the bag is needed between the end of the storage and the beginning of the ripening protocol. When green bananas are transported within banavac bag, an operator needs to open all the bags with a knife before starting the ripening process in order to allow the oxygen to enter the bag and remove the carbon dioxide. Using the starch based film, the cost for this extra handling can be reduced.

[0169] Permeability Tests

[0170] The oxygen and carbon dioxide transmission rates of the packaging materials were measured at two temperatures (22 and 8° C.) and two relative humidity (RH) levels (0% and 85%). For this, the packaging sheet was clamped between two pots: in the above pot, medical air (21% O.sub.2 and 0% CO.sub.2) was continuously flushed (100 mL/min); in the under pot, a gas mix of high level carbon dioxide and low oxygen content was flushed at the beginning of the test. In order to create stable relative humidity, the gas flushed in the top pot is first flushed through a bottle of dry silicate gel for the 0% relative humidity test or through a bottle of saturated potassium chloride solution for the measurement at 85% relative humidity. The gas content in the under pot was regularly measured using a Dansensor Checkmate 2 by sampling 10 mL of the air volume. The air pressure inside the under pot was also measured with pressure meter before and after each air sampling. The oxygen and carbon dioxide transmission rate of the sheet was then calculated by using a linear regression analysis of the oxygen and carbon dioxide (pure) volume over the time and corrected for a standard thickness of the foil sample of 100 μm. The oxygen and carbon dioxide content were first converted to volume of gas and corrected with the partial pressure difference measured before and after each gas measurement. The oxygen and carbon dioxide transmission rates are reported in the table below.

TABLE-US-00004 TABLE 4 Oxygen and carbon dioxed transmissions rates Oxygen Carbon dioxide Selectivity (ml O.sub.2/m.sup.2.day.bar.100 μm) (ml CO.sub.2/m.sup.2.day.bar.100 μm) (CTR/OTR) 23° C.− 23° C.− 8° C.− 23° C. 23° C.− 8° C.− 23° C. 23° C. 8° C.− 0% 85% 85% −0% 85% 85% −0% −85% 85% RH RH RH RH RH RH RH RH RH BOPP (without 330 330 90 800 800 500 2.4 2.4 5.5 perforation) starch/polyethylene 330 1650 1600 850 8100 4800 2.6 4.9 3 polymer-based film

[0171] Based on the measurements as shown, the hydrophilic/hydrophobic polymer-based sheet reacts to both storage conditions criteria: temperature and relative humidity, whereas the BOPP material reacts only, and in a lower rate, to the temperature criterium.

[0172] Based on these results, it can been concluded that: [0173] 1. the increase in concentration of carbon dioxide over time in the hydrophilic/hydrophobic polymer-based bags is much more limited than in the micro perforated BOPP bags. The final carbon dioxide content in the hydrophilic/hydrophobic polymer-based packaging was low enough to avoid any CO.sub.2 damage in the pear fruit; [0174] 2. the amount of oxygen is lower in the hydrophilic/hydrophobic polymer-based bags than in the micro perforated BOPP bags; [0175] 3. the decrease in firmness in the pears packed in the hydrophilic/hydrophobic polymer-based sheet is comparable or lower than in the micro perforated BOPP sheet after the warm 5 day period. Therefore the quality seems better. [0176] 4. the colour of pears packed in the hydrophilic/hydrophobic polymer-based sheet remains similar to the initial colour or remain greener than pears packed in the micro-perforated BOPP sheet or packed in macro-perforated BOPP sheet after the storage period.

[0177] This shows that the present hydrophilic/hydrophobic polymer-based packaging material [0178] 1) is a material that shows dynamic change in carbon dioxide permeability resulting from temperature and RH variations. This leads to a better balanced atmosphere in the package particularly when ambient conditions as temperature and RH change. This significant change of permeability of the material makes the package particularly useful to maintain quality of fresh products in chains with varying or uncontrolled ambient conditions. [0179] 2) can be adjusted in the composition of the sheet so as to adjust the permeability of the packaging sheet, thus fitting a wide range of fresh products. The optimal permeability/packaging for each product: different fresh products require different permeabilities (to cope with different metabolism rates) and thermally responsive permeabilities to meet the requirements of changing ambient conditions throughout the distribution chain.

EXAMPLE 2

[0180] Production of Starch/Polyethylene Film (2760 and 2761)

[0181] Manufacturing of the hydrophilic/hydrophobic film is performed in 2 steps: [0182] 3. production of a thermoplastic composition with a hydrophilic polymer phase, a hydrophobic polymer phase and a compatibilizer [0183] 4. production of a film out of the thermoplastic composition

[0184] ad 1-I: A powder/fluid mixture comprising:

[0185] 2760 (100717-008) [0186] 29.9% native potato starch (type PN Avebe; 19% moisture content) (=hydrophilic polymer) [0187] 1.12% borax (type: Borax 10H2O GR Turkey obtainable from Brenntag) [0188] 1.12% fatty acid mixture (type Radiacid 0436, obtainable from Oleon) [0189] 0.56% glycerol mono stearate (type Radiasurf 7142 GMS, obtainable from Oleon) [0190] 0.22% sodium carbonate (type sodium carbonate anhydrous light Food (E500i) from Brenntag) [0191] 22.0% glycerol (type glycerine vegetable Pharm. (E422), obtainable from Brenntag) [0192] 41.1% LDPE (type Sabic LDPE 2008TN00) (=hydrophobic polymer) [0193] 4.0% compatibilizer (type Lotader 3410, obtainable from Arkema)

[0194] was compounded on a Berstorff ZE 40 A*38 D twin screw extruder equipped with a GALA LPU underwater pelletizer. Temperature profile along the barrel was: zone 1: 25° C.; zone 2: 60° C.; zone 3: 135° C.; zone 4: 160° C.; zone 5: 160° C.; zone 6: 160° C.; zone 7: 110° C.; zone 8: 95° C.; LPU: 120° C. Screw speed was 225 rpm. Total throughput was 26 kg/h. The compound was pelletized with help of the underwaterpelletizer (pellet size was about 4 mm) and dried to a moisture content of 3.4%.

[0195] ad 1-II: A powder/fluid mixture comprising:

[0196] 2761 (100717-006) [0197] 38.97% native potato starch (type PN Avebe; 19% moisture content) (=hydrophilic polymer) [0198] 1.46% borax (type: Borax 10H2O GR Turkey obtainable from Brenntag) [0199] 1.46% fatty acid mixture (type Radiacid 0436, obtainable from Oleon) [0200] 0.73% glycerol mono stearate (type Radiasurf 7142 GMS, obtainable from Oleon) [0201] 0.29% sodium carbonate (type sodium carbonate anhydrous light Food (E500i) from Brenntag) [0202] 29.01% glycerol (type glycerine vegetable Pharm. (E422), obtainable from Brenntag) [0203] 22.83% LDPE (type Sabic LDPE 2008TN00) (=hydrophobic polymer) [0204] 5.26% compatibilizer (type Lotader 3410, obtainable from Arkema)

[0205] was compounded on a Berstorff ZE 40 A*38 D twin screw extruder equipped with a GALA LPU underwater pelletizer. Temperature profile along the barrel was: 30/90/150/160/160/160/110/95° C. in zones 1 till 8; Die temperature: 120° C. Screw speed was 225 rpm. Total throughput was 20 kg/h. The compound was pelletized with help of the underwaterpelletizer (pellet size was about 4 mm) and dried to a moisture content of 4.6%.

[0206] Ad 2: Starch/LDPE compound was processed into a symmetrical 3 layer film with help of a BFA/Battenfeld coextrusion multilayer (max=5) film blowing machine. Machine consisted out of a Battenfeld UNI-Ex 1-45-25B (central layer) and a BFA 30-25 extruder (for both coating layers) attached to a Battenfeld BK 50/150-05 multi spiral mandrel die. Central layer consisted out of the pelletized material as described under Ad 1. Both coating layers consisted out of a dry blend of 60% Sabic LDPE 2404, 30% Sabic LLDPE 6318 and 10% Lotader 3410. Layer distribution was: coating/central layer/coating=25/50/25. Processing temperatures were about 130° C. for the central layer and 145° C. for both coating layers. Total throughput was 9 kg/h. Film thickness was about 46 micron (2760) and 63 micron (2761). Stretch ratio in transverse direction is between 3 and 4. Stretch ratio in machine direction is between 8 and 9.

[0207] Material and Methods

[0208] a) Packaging Films

[0209] Further film materials according to the present disclosure (with the code 2760: referred as “starch film A” in the present document, and 2761: referred as “starch film B” in the present document) were tested with pears and mushrooms.

[0210] Both film were produced in 2017 by WFBR, their oxygen transmission rate, i.e. OTR properties were tested at 0 and 70% relative humidity and 23° C. The tables below show their OTR values.

TABLE-US-00005 OTR corrected at OTR 100 μm [mlO.sub.2/m.sup.2 .Math. day .Math. bar] [mlO.sub.2/m.sup.2 .Math. day .Math. bar] Samples Thickness (23° C., 0% RH, (23° C., 0% RH, code [μm] 100% O.sub.2) 100% O.sub.2) Starch 46.2 ± 2.0 826.3 ± 4.2 381.8 ± 18.3 film A Starch 63.2 ± 7.9  12.1 ± 1.0  7.60 ± 0.32 film B

TABLE-US-00006 OTR corrected at OTR 100 μm [mlO2/m.sup.2 .Math. day .Math. bar] [mlO2/m.sup.2 .Math. day .Math. bar] Samples Thickness (23° C., 70% RH, (23° C., 70% RH, code [μm] 100% O.sub.2) 100% O.sub.2) Starch 46.2 ± 20 2996.6 ± 65.5  1385.1 ± 89.6 film A Starch 63.1 ± 7.9 1721.6 ± 205.2 1079.9 ± 6.6  film B

[0211] The packaging treatments for the pears consisted of: [0212] Reference packaging: Polypropylene film (Van der Windt, 30 mm thick) with 4 micro perforation of 100 μm diameter. The dimension of the bags was 18*27 cm (970 cm.sup.2) [0213] Starch film A (code 2760): The dimension of the bags was 18*27 cm (970 cm.sup.2) [0214] Starch film B (code 2761): The dimension of the bags was 18*27 cm (970 cm.sup.2)

[0215] The bags, with 4 pears per bag, were sealed under atmospheric gas conditions (20.8% O.sub.2 and 0.1% CO.sub.2).

[0216] Bag with product were first stored for 5 days at 5° C. and 100% relative humidity. Then they were transferred to storage room at 18° C. and 60% relative humidity.

[0217] Concerning the test with mushroom product, the following packaging treatments were used: [0218] Reference packaging: Polypropylene film (Van der Windt, 30 mm thick) with 43 micro perforation of 100 μm diameter. The dimension of the bags was 18.5*27 cm (1000 cm.sup.2) [0219] Starch film 1 (code 2760): The dimension of the bags was 18.5*27 cm (1000 cm.sup.2) [0220] Starch film 2 (code 2761): The dimension of the bags was 18.5*27 cm (1000 cm.sup.2)

[0221] Bags were sealed with atmospheric gas condition (20.8% O.sub.2 and 0.1% CO.sub.2).

[0222] Bag with product were first stored for 5 days at 5° C. and 100% relative humidity. Then they were transferred to storage room at 18° C. and 60% relative humidity.

[0223] b) Products:

[0224] Pears can be considered as a fresh product with a relatively low respiration rate, mushroom is a fresh product presenting really high respiration activity.

[0225] Pear (conference) and mushroom were purchased at the local supermarket and stored at 5° C. for 24 hours.

[0226] Each bag consisted of 4 pears or one trays of mushroom (250g).

[0227] Results

[0228] a) Pear

[0229] Oxygen and carbon dioxide concentrations were measured on day 0, 2, 5, 7 and 9 (FIG. 2).

[0230] Both treatments made of starch film followed similar gas patterns. Oxygen decreased during the period of storage at 5° C. to reach a level lower than 1%. When pears were transferred to the shelf life room, oxygen content into the packaging headspace increased slightly to a content of 2-3%. This can be explained by the dynamic property of the packaging material. Under higher storage temperature, the middle layer of the film structure was able to absorb more water from its direct surrounding (Water vapour transmission rate of the PE outside layer is directly temperature dependant). This engender a significant increase the total permeability property of the complete packaging made of starch material.

[0231] Concerning the carbon dioxide content into the packaging (FIG. 3), storage at 5° C. allowed to monitor the CO.sub.2 content under 8% for all three packaging concepts. When transferring the bags to room temperature, the CO.sub.2 content increased drastically to around 20% for the reference packaging. Using the starch film, the CO.sub.2 content increased slightly but remained to an acceptable level after 4 days storage.

[0232] b) mushroom

[0233] Oxygen and carbon dioxide concentrations were measured on day 0, 2, 5, 7 and 9 (FIGS. 4 and 5).

[0234] Both starch packaging followed similar gas content pattern. The oxygen inside the bag was completely consumed within two days storage at 5° C. The carbon dioxide content inside these bags increased first to 14% on day 2 and later on decreased and stabilised to 9%. The higher CO.sub.2 content during the second days can be explained by the dynamic behaviour of the starch packaging. These packaging materials adjust their gas permeability to storage temperature and relative humidity. Higher is the relative humidity (inside and outside the bags), higher is the permeability to oxygen and carbon dioxide. At the beginning of the test, the starch material is still dry, and so is less permeable to CO.sub.2 and O.sub.2. This induced the peak of CO.sub.2 content inside the bag observed on day 2. After few days under high relative humidity, the packaging material is getting more permeable to gas and resulted to a lower CO.sub.2 content inside the bag headspace.

[0235] This phenomena is not observed for 02, as the oxygen was completely and directly consumed by the mushroom.

[0236] Concerning the quality of the mushroom at the end of the experiment (5 days at 5° C. followed by 4 days at 18° C.), packing inside the starch film allowed to keep the mushroom dry, firm and slow down the opening of the lamella under the mushroom head. At the contrary, packing into polypropylene bags with micro-perforations leaded to sliminess on the mushroom head, softening and brown discoloration of the complete mushroom tissue (FIG. 6).

[0237] On basis of these results, it can be seen that further improvement can be achieved by using a film that is somewhat less impermeable, since mushroom is a fresh product with an extremely high respiration rate activity. Accordingly, the thickness of the PE layer on both outer sides of the functional layer may be reduced, and/or the amount of starch composition in the functional middle layer may be increased. Using also thinner starch film material will also allow more gas exchanges.

[0238] To pack fresh products with a higher respiration rate such as mushroom, adjustments in the film material composition can be made. The following adjustments can make the film more permeable to oxygen and carbon dioxide: [0239] reducing the thickness of the PE outside layer(s); [0240] increasing the Starch/PE ratio in the functional middle layer; [0241] adjusting the starch structure (mono- or multi-branches structure) may also help to increase the permeability of the film.