Method of packaging food

Abstract

The invention proposes a container further extending the shelf life of foods, particularly berries, by including an active agent having antifungal capability into the container surface so that when the fruit is packaged inside the container it is permanently exerted an antifungal effect over the surface, which is the place on the longer determinants occurs, but also contributing to preserve the general environment. Also it proposes a preparation process and its use.

Claims

1. A process for making a package of polyethylene terephtbalate (PET) with an antifungal agent incorporated into its surface, the method comprising: a) adding to a mixture of silicone in water, the antifungal agent in an amount less than or equal to 20% w/v and thereby forming a homogeneous solution as bath; and b) immersing in said bath extruded PET sheets and subsequently performing the steps of thermoforming and producing the final package.

2. The process of claim 1, wherein less than 15% w/v of the antifungal agent is added in the silicone solution in water.

3. The process of claim 2, wherein less than 10% w/v of the antifungal agent is added in the silicone solution in water.

4. The process of claim 1, wherein the extruded PET sheets, are immersed in a bath of silicone in water containing 18-20% w/v of antifungal.

5. The process of claim 1, wherein the antifungal is an antifungal against Botrytis cinerea.

6. The process of claim 1, wherein the antifungal agent is potassium sorbate.

7. The process of claim 1, wherein the extruded PET sheets are sheets of recycled PET.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) FIG. 1—Addition of the silicone solution in water, incorporating the antifungal agent to the packaging production line (A). RPET sheet extruded, receiving solution coating (B).

(2) FIG. 2—Shows SEM images of the PET+Antifungal B (potassium sorbate) film.

(3) FIG. 3—Potassium sorbate CMI for an initial concentration of B. cinerea of 105 cfu/mL.

(4) FIG. 4—WCC potassium sorbate to an initial concentration of B. cinerea of 103 cfu/mL.

(5) FIG. 5—Shows the result of the whole process (Coating and Thermoforming) at pilot level. Antifungal potassium sorbate.

(6) FIG. 6—Shows the Halo test in pilot-scale prototypes. Initial concentration of B. cinerea: 10.sup.5 cfu/mL. The plates were incubated for 5 days at 25° C. The assay was performed in duplicate, with 4 repetitions.

(7) FIG. 7—Sample test Halo—Coating. Initial concentration of B. cinerea: 10.sup.5 cfu/mL. The plates were incubated for 5 days at 25° C. The assay was performed in triplicate, with 3 repetitions.

(8) FIG. 8—View of blueberries in a moist chamber.

(9) FIG. 9—Cranberry fruit with Borryris cinerea mycelium.

DETAILED DESCRIPTION

(10) The present invention comes from the application of Polyethylene terephthalate (PET), 100% recyclable, known as RPET. It was chosen because it is the most widely used in more than 90% of the fruit industry for its features concerning cost, transparency and resistance. It is also a material that can be reused and recycled.

(11) The antifungal agent initially tested in this invention was potassium sorbate, due to its effectiveness against fungi especially Botrytis cinerea, because of its GRAS character (Generally Recognized As Safe) and for being used directly on foodstuff.

(12) The manufacturing process of the active antifungal packaging does not interfere with the elaboration process of conventional packaging. This invention uses a bath of water plus silicone, usually used by PET thermo forming enterprises in order to prevent the packaging from sticking together when being stacked. In the industrial process, once the extruded PET film is immersed in the silicone containing bath, then immediately the excess of solution is removed and the film rolled to later continue to the thermoforming and production process of the packaging.

(13) In order to produce the active container, the silicone bath was used to incorporate the antifungal agent (potassium sorbate) which is chemically soluble in water and silicone, forming a homogeneous solution (FIG. 1A)

(14) Thus, when the RPET film passes through the silicon bath it is also impregnated with an antifungal agent (FIG. 1B), that was “trapped” by the silicone deposited on the surface. FIG. 2 (image scanning electron microscopy, SEM) shows the presence of potassium the polymer surface.

(15) As the antifungal agent used withstands temperatures up to 270° C., the thermoforming process (±140° C.) does not affect its stability.

(16) Laboratory studies using liquid chromatography (HPLC) showed that about 0.1% of the antifungal agent added to the bath is adhered t the packaging (for a silicone bath containing between 18-20% w/v of antifungal agent in the silicone solution in water).

(17) Study of Minimum Inhibitory Concentration (MIC)

(18) Studies on the minimum inhibitory concentration of potassium sorbate against B. cinerea were performed using potato dextrose agar, containing 10 concentrations of the antifungal agent, ranging from 0.0 to 1.0% w/v (antifungal agent in silicone solution in water) for an initial concentration of B. cinerea of 10.sup.5 cfu/mL and from 0.0 to 0.2% w/v, for to an initial concentration of B. cinerea of 10.sup.3 cfu/mL. At the center of the plates 30 μL of a suspension containing 10.sup.5 to 10.sup.3 cfu/mL of spores of B. cinerea were incorporated, with 5 days of growth at 25° C. The plates were incubated at 25° C. for 5 days and then growth in various concentrations was observed.

(19) For a concentration of 10.sup.5 cfu/mL of B. cinerea, the minimum inhibitory concentration of potassium sorbate is between 0.38 and 0.40% w/v (FIG. 3). For 10.sup.3 cfu/mL (closest counting to that observed in the fruit export) minimum inhibitory concentration is between 0.07 and 0.10% w/v (FIG. 4).

(20) At a pilot scale packaging was produced with respective concentrations of antifungal agent: 0.0 (control), 10.0, 15.0 and 20.0% w/v (FIG. 5).

(21) Study of the Eco-Efficiency Active Package Against B. cinerea

(22) Studies on the efficiency of produced eco-active packaging against B. cinerea were based on the Halo Test, using potato dextrose agar. At the center of the plates 30 μL of a suspension containing 10.sup.5 cfu/mL of spores of B. cinerea were incorporated, with 5 days of growth at 25° C. and, at equidistant positions at the ends of the plate four packaging discs were placed with 1 cm diameter. The plates were incubated at 25° C. for 5 days and then growth of fungi in different concentrations of antifungal incorporated into the package was observed.

(23) Halo tests demonstrate the effectiveness of the films produced at different concentrations, against B. cinerea. Assays were performed in triplicate with three repetitions (FIG. 6).

(24) Sodium benzoate was studied as an alternative antifungal and also the mixture of potassium sorbate plus sodium benzoate (commercially prepared for direct use in food) to verify the cost/benefit for the preparation of the final packaging (FIG. 7). Assays were performed in triplicate, with 3 repetitions.

(25) Study of the Efficiency of Eco-Active Packaging Containing Blueberries.

(26) This test consisted in determining contamination postharvest fungus making a count of the total number of fruits in the wells in blueberry fruit for export from two producers from different regions in the country identified as A (Town of Panguipulli, Province of Valdivia, Los Ríos Region) and B (Town Collipulli Malleco Province, Araucanía Region). The treatments the fruit was subject of were two storage temperatures, 4 and 10° C., cold room with 85% humidity and two types of packaging, conventional (RPET) and active (RPET with addition of 20% potassium sorbate antifungal agent), with 11 repetitions (each consisting of a cup of 125 gr) and 5 evaluation dates (0, 7, 14, 21 and 28 days). The experimental design was completely randomized. When establishing the assay, the initial contamination of fruit was determined by visual observation of all fruit from 10 wells, as well as 400 fruits that were subject of favorable conditions for developing postharvest pathogen agents, i.e. moist chamber on plastic trays with humid paper towel and covered with plastic for 7 days (FIG. 8).

(27) Once finished the time of permanence in storage conditions for each evaluation date, the fruit was removed from the cold room and assessed in the phytopathology laboratory, making a count of the total number of fruits in the wells, and separating the number of fruits contaminated with Botrytis cinerea (FIG. 9), visually or with the aid of a stereomicroscope. Then the percentage of infection in each treatment was calculated. These values were statistically analyzed, transforming the data previously to √n+0.5. LSD test was used to separate the significance between means, considering p≦0.05.

(28) At the beginning of the assay no visual differences were observed concerning the health of fruits from both producers, but in cold room after 5 days a slight difference was observed, where producer A had 1.25% of contamination by B. cinerea and producer B a 3%.

(29) The results for the different dates of assessment according to the statistical analysis and the evaluated parameters are indicated in Table 1 which shows that for producer A (very healthy fruits) differences were found starting from the evaluation of 21 days of storage and temperature, not for the kind of packaging. While for producer B, from day 7 of storage, there was an effect of temperature on the contamination of fruits by the fungus. Differences were also found for the type of container at 21 and 28 days and interaction between the two factors in two evaluation dates.

(30) TABLE-US-00001 TABLE 1 Effect of different factors on contamination of Botrytis cinerea in blueberries from two producers, statistical analysis results. Producer A Producer B % of B. cinerea % of B. cinerea on different on different evaluation evaluation dates dates Parameter 4 1 8 4 1 8 Temperature S S * * * * * * Packaging S S S S S S * * Temperature* S S S S * S S * packaging NS = not statistically significant values according to LSD test P ≦ 0.05 ** = Statistically different values according to LSD test P ≦ 0.05

(31) In tables 2 and 3 results for Botrytis cinerea contamination by type of container for different sampling dates are shown. It is observed that the producer A had no effect of the type of packaging on contamination and that it was very low, not even 1% most of the time. For the fruit from producer B, who had larger contamination, a positive and promising effect of the packaging was observed, especially at 21 and 28 days of storage.

(32) TABLE-US-00002 TABLE 2 Percentage of contamination of blueberry fruits from producer A by B. cinerea in different packaging. Producer A % B. cinerea at different days of evaluation Packaging 7 14 21 28 Active 0.10* a 0.05* a 2.64* a 0.43* a Conventional 0.06 a  0.2 a  2.32 a  0.62 a 

(33) Values with different letters in each column are statistically different according to LSD test P≦0.05.

(34) TABLE-US-00003 TABLE 3 Percentage of contamination of blueberry fruits from producer B by B. cinerea in different packaging. Producer B % B. cinerea at different days of evaluation Packaging 7 14 21 28 Active 0.11* a 3.43* a 5.25* b 12.13* b Conventional 1.02 a  5.22 a  7.69 a  17.85 a 

(35) Values with different letters in each column are statistically different according to LSD test P≦0.05.

(36) The results concluded that the health of the fruit when the test set was crucial in the results obtained.

(37) The fruit from producer A developed very low percentages of infection by B. cinerea during the entire evaluation period, so that no differences between treatments were determined.

(38) It was found that the fruit from producer B had larger contamination by B. cinerea as well as a positive effect of the active packaging, by reducing contamination by fungus, especially on days 21 and 28 of storage.