WO2022032402A1

WO2022032402A1 - Antimicrobial composition that preserves the organoleptic conditions of fruit and vegetables

Info

Publication number: WO2022032402A1
Application number: PCT/CL2020/050089
Authority: WO
Inventors: Roberto MOSER
Original assignee: Moser Roberto
Priority date: 2020-08-10
Filing date: 2020-08-10
Publication date: 2022-02-17

Abstract

The invention relates to an antimicrobial composition that preserves the organoleptic conditions of vegetables, formed by mixing a solution of a polymer and a solution of a solid water-soluble solute, which, when the solvent evaporates, forms a gas-permeable polymer coating, with small precipitated particles of the solute, which are contained in a polymer mesh and react in the presence of moisture, regaining antimicrobial behaviour.

Description

DESCRIPTIVE MEMORY

The invention is an Antimicrobial Composition that preserves the organoleptic conditions of vegetables, formed by mixing a solution of a polymer and a solution of a solid solute that is soluble in water, which, when the solvent evaporates, forms a polymeric coating that is permeable to gases, with small precipitated solute particles contained in the polymeric mesh, which react in the presence of moisture, returning to have an antimicrobial behavior.

STATE OF THE ART

Agricultural products such as fruits, vegetables and vegetables remain alive after they are harvested. The challenge that arises then is to keep these vegetables in the best possible conditions so that when they are consumed they have the highest nutritional value. The long way that agricultural products take to reach the table means that many times they do not get it in the best desired conditions and in some cases they must be discarded. According to the Food and Agriculture Organization of the United Nations, 30 percent of food is wasted globally throughout the supply chain, contributing 8 percent of global greenhouse gas emissions. (Global AG Investing). At present, wax, fungicides, chemical products, fresh packages and plastic containers are presented as solutions to extend the shelf life of food, but their effectiveness is limited, in addition to the fact that there are a series of requirements imposed by the markets and the sanitary regulations of the different countries, which make it more difficult to satisfy them every day.

The path of plastic containers has led to the development of new materials characterized by combining the use of thermoplastic materials, which are easy to manufacture, with the introduction of other polymers or fillers of a different nature within the structure of the container wall, (WO201 1045455 ) PACKAGING FOR PERISHABLE PRODUCTS, to become a barrier to gases such as oxygen, carbon dioxide, water vapor and ethylene, among others, which in contact with vegetables alter their qualities, from changing their appearance to the appearance of pathogens harmful to health. Plastic containers that contain in their structure some type of material with the property of substantially reducing or eliminating the passage of these substances are called barrier. These can be divided into static and active. The former are materials that act as barriers to the passage of substances that are to be left out and that have a constant behavior over time. In the second case, these are materials that, in addition to acting as a barrier like the first, have incorporated additives with chemical activity that capture the substance to be stopped. Here the oxygen scavengers stand out, which allow extending the protection of the barrier against the passage of this. This lengthens the life of the barrier and therefore of the product to be preserved. (Patent EP0349440B1) An example of an oxygen scavenger additive is active nanocomposite materials based on nanoclays modified with cerium oxide or metallic cerium (WO 2013186416 A2).

A container is antimicrobial when it incorporates several active substances in it, so that they are effective in inhibiting or retarding microbial growth (altering or pathogenic). These substances can be incorporated directly into the containers, so that they are released in a controlled manner to the head space (volatile substances such as essential oils). Another option is to immobilize the active agents (eg bacteriocins) on the surface of the container, exerting their action through direct contact with the product. (Magazine: Food, Equipment and Technology).

An example of this is patent WO 2013149356 Al, which refers to containers that extend the shelf life of foods by incorporating an antifungal agent on their surface, particularly for berry containers. In general, the containers that contain antimicrobial elements on their inner face do not maintain the organoleptic characteristics of the products since these elements migrate to the surface of the food. This does not occur with antimicrobial elements contained in a polymeric matrix such as copper and/or its derivatives. These materials act as antimicrobial materials since when they react with moisture they oxidize, releasing Cu2+ ions which, when they reach the microorganisms, damage their cell walls, which has the effect of killing them. (Borkow and Gavia 2005). Materials capable of releasing sufficient Cu 2+ are then classified as antimicrobials. This behavior also occurs for metals such as silver, zinc and tin, and/or mixtures and salts of these elements, which classifies them the same as copper as an antimicrobial agent.

Inorganic biocidal agents are defined as compounds based on copper, silver, zinc, gold, bismuth, mercury, tin, antimony, cadmium, chromium, tantalum, iron, manganese and lead, their oxides, hydroxides, acetates, carbonates, chlorides, nitrates, phosphates, sulfates, sulfides, and mixtures thereof, presenting biocidal activities (WO 2015011630). The bactericidal and fungicidal action of the elements described above can be introduced into the polymer matrix at the time of manufacturing the sheets that make up these plastic containers, such as polypropylene, polyethylene, polyester resins, etc.

There are antimicrobial compositions that employ zeolite particles as a carrier for the antimicrobial metal ions. That is, when treating the zeolite with metal ion solutions, a cationic exchange is produced where ions are incorporated. antimicrobial metals in it acquiring the antimicrobial properties of these, which is called loading. This occurs in both naturally occurring and synthetic zeolites. In these cases where the antimicrobial properties are incorporated into another element, as is the case with zeolite, the microporous mineral used is called a support. The support or carrier material (B) corresponds to organic or inorganic materials, selected from zeolite, silicates, sepiolite and dolomite, wollastonite, mica, ceramic, carbon, activated carbon, clay, hydroxyapatite, kaolin, talc, calcium carbonate, stone pumice, natural or synthetic fibres, coconut fiber (WO 2015011630).

All this range of products and solutions described are a complement to cold treatments and refrigerated transport and must be removed or discarded from the products before consumption, with the consequent generation of waste, many of them non-recyclable, which becomes be a negative factor when evaluating them as alternatives.

We know that cold is the basic technology used to delay fruit ripening and reach the markets in optimal conditions. Controlled Atmosphere is used as a complementary technology to cold to extend the shelf life of fresh vegetables by reducing metabolic processes, retarding microbial growth and delaying the senescence process. This technology regulates the composition of the air in the container in order to slow down the metabolism of the fruit, which it does by modifying the composition of the air inside the container, Nitrogen (N), Oxygen (02), Carbon Dioxide (CO2) and Ethylene, a natural gas produced by fruits and vegetables during their metabolic process, and also controlling humidity and temperature. All this to achieve the optimal combination of the atmosphere of the container so that the metabolism of the fruit is slowed down. If the product is a carrier of pathogens, during the controlled atmosphere they are inhibited from multiplying, but once the atmosphere is controlled, they present a more aggressive behavior than normal, which shortens the time it remains in optimal conditions after the container is opened. . This technology is expensive, requires active monitoring and regulation of the composition of the atmosphere during the trip, in addition to having to carry out the logistics of recovering the equipment that is added to the containers.

There is a cheaper variant of Controlled Atmosphere which is Modified Atmosphere. This is also complementary to the cold and consists of putting an airtight polymeric membrane around the pallet that contains the boxes of fruit, modifying the atmosphere of this enclosed space by adding a predefined amount of CO2 and/or Nitrogen N2, this being defined at the beginning of the process. trip and marginally modified by the permeability of this membrane to let 02 enter, CO2 and ethylene leave. The margin of action is much smaller and it also has the problem that when the membrane is opened in the presence of pathogens, these will develop very quickly after opening the package, lasting less time in optimal conditions than without the modified atmosphere process.

There is a global trend to seek a solution to this problem through the application of natural coatings in the postharvest process that modify the respiration of the fruit, in addition to some other natural complement that has an antifungal effect. This coating and its antifungal supplements must be edible as they adhere to the surface of the fruit. This is a direct way of regulating breathing and it consists of applying a polymeric coating, which, given its characteristics of permeability to gases, modifies the passage of these, making it slower. We speak then of biodegradable natural biopolymeric coatings that can incorporate elements that have antimicrobial and antioxidant properties into their interior. Within these edible coatings we can highlight those that use the polymeric matrix of chitosan, cassava starch, oat starch, aloe vera, combinations of these such as corn starch and chitosan, or successive layers of chitosan, poly-L- lysine, alginate, pectin, with the addition of natural anti-fungal elements such as essential oils, and natural antioxidants. As you can see the number of combinations are many and each of them with its characteristics. In addition, the forms of application add another range of combinations, which can be immersion or spray, mostly, although there are manual applications for some fruits. Another characteristic that the fruits to which these coatings are applied must have is that they must be previously washed and dried.

DETAILED DESCRIPTION OF THE INVENTION

The objective of preserving the organoleptic conditions of the vegetables after harvesting without contaminating the fields with chemical products, without leaving traces of pesticides on the vegetables, without generating single-use plastic waste, that is, in harmony with life and with the environment is what is intended to achieve with this new invention. This is an Antimicrobial Composition that preserves the organoleptic conditions of vegetables, formed by a solution of a polymer and a solution of a solid solute, which is soluble in water and provides antimicrobial characteristics, which when the solvent evaporates forms a polymeric coating , which is permeable to gases, with small solute particles precipitated and contained in the polymeric mesh, which react in the presence of moisture, returning to have an antimicrobial behavior. The result is a polymer coating with small particles of precipitated solute inside. A necessary characteristic of the solute is that it be soluble in water, so the Precipitated particles, contained in this polymer coating, upon receiving the action of humidity, which is the necessary condition for the proliferation of pathogens, once again have antimicrobial properties. The permeability to gases and water vapor of the resulting polymeric coating is responsible for the humidity activating the solute particles, making them antimicrobial, in addition to modifying the respiration of the fruit, slowing down its metabolism in order to prolong its organoleptic characteristics until become consumed. The polymeric coating with antimicrobial properties will remain on the surface of the fruit until it is consumed by the end customer, so its composition must be edible. In the case of climacteric fruits, the polymeric coating, by slowing down their metabolism, will produce a delay in their ripening, but will always keep them protected from the action of pathogens due to the antimicrobial characteristics of the precipitated particles, throughout this longer period of storage. time in which the maturation is extended and that is exposed to the action of these. Then the complete effect produced by this Antimicrobial Composition when applied to fruit, vegetables or vegetables, is in a first stage the elimination of the pathogens that are on the surface of this by the action of the solutions that compose it, for later when the solvent evaporates, leaving a polymeric coating that reduces the metabolism of the fruit, prolonging its organoleptic properties for a longer period while protecting them from the action of pathogens through the action of the solute precipitated inside, which is activated when they give the humidity conditions that are the ones that allow pathogens to develop.

A characteristic of each polymeric matrix is that it can be permeated by some gases and water vapour, allowing it to be breathed through, as is the case with fruit that needs oxygen for its metabolism and exhales it as CO2, in addition to exhaling ethylene from its metabolic process. The permeability of the polymeric coating allows the precipitated particles to be reached by the activating element of its antimicrobial characteristic, which is humidity and whose activity is limited to the area where it is permeated, and which is the condition in which microorganisms develop and multiply. . That is, the precipitated particles of the ionic solute are a passive antimicrobial that is activated by the effect of humidity. The concentrations of each one of the components of the Antimicrobial Composition define the thickness of the coating, the size and the quantity of precipitated particles contained in it, which in turn will define the permeability of the polymeric coating to gases and humidity, which will be the key of the modification of the metabolism of the fruit.

Another factor that affects the coating is the form of application, which is basically by spraying and by immersion. The time it takes for the coating to dry It must be pre-established in order to have a specific antimicrobial effect without producing any negative effect on the surface of the fruit.

The action of this Antimicrobial Composition is not limited to post-harvest, since it can be applied in the field, both to the fruit and to the tree or plant that produces it, since it generates an effect of eliminating pathogens in their liquid state and then it maintains a passive protection over time. This is important in the case of some fruits that are not recommended to be washed in the postharvest process, to which the Antimicrobial Composition can be applied while the fruit is in the bush. In the case of grapes, it could be applied to the vine prior to the closing of the bunch, where botrytis develops mainly inside. Another aspect that should be highlighted is in the case of being applied to fruits with stems such as cherries and grapes, the polymeric coating will delay the dehydration process of these, so they will maintain their appearance of color and freshness for a longer time.

A practical example of this Antimicrobial Composition is the mixture of a polymeric aqueous solution of PVOH and an aqueous solution of Citric Acid, both in concentrations less than 5% p/p. The concentration of the acid defines how strong or active the solution is going to be in the elimination of surface pathogens, also taking into account how strong or weak the outer layer of the fruit on which it is applied is. The concentration of the polymer in the composition will define the thickness of the resulting film or coating on the fruit and its degree of permeability to gases that slow down its metabolism and maintain its organoleptic qualities for longer in fresh conditions.

In a practical test of the Antimicrobial Composition, carried out on 1,500 avocados with a high incidence of anthracnose, significant changes were seen in the incidence of the pathogen and a significant delay in the ripening of the fruit. After a cooling period, a mixture of a 3% w/w aqueous citric acid solution and a 2% w/w polyvinyl alcohol (PVOH) solution was applied to the fruit by spraying. As a result, this produced a coating of approximately 9 gr/m2, which was allowed to dry, and then the fruit was allowed to ripen under ambient conditions, where the temperature ranged between 14°C and 24°C. and maturation stages were reported daily. The incidence of anthracnose in the controls was 83.9% and where a visible difference could be seen in the result of the fruit with the Antimicrobial Composition, which showed a 59.3% incidence, which clearly shows the chart below. (Antimicrobial Composition is called PIRojo). Distribution of severity levels of Anthracnose in Avocados

The active antimicrobial effect is significant, recovering a healthy state from 16.1% of the fruit to 40.7%. That is to say, 29.3% of the infected avocados achieved healthy maturation, in a longer maturation time, without the activation of the anthracnose pathogen with which they were contaminated.

The delay of the maturation that could be observed, between the control and the fruit with the applied Antimicrobial Composition, were also significant. From an average maturation time of 13.6 days to an average of 20.2 days, which is 48.5% more than the control, as shown below.

Days of avocado consumption maturity evaluated

It is important to bear in mind that lengthening the maturation time implicitly gives pathogens more time to become active. Then the result of the application of the Antimicrobial Composition is double, since it rescued 29.3% of the infected avocados for a longer maturation period of 48.5%, under ambient conditions. The active protection eliminated the pathogens during the liquid state of the Antimicrobial Composition and then the polymeric coating acted as a retarder of ripening, while the fruit continued to be protected by the passive effect of the precipitated particles of citric acid in the coating.

This passive protection is the one shown in the following tables and which measured the result of applying a solution of sucrose and dextrose with anthracnose conidia on a slide where the Antimicrobial Composition had been applied and which had been allowed to dry completely, which it is the condition that the pathogens will find when they are deposited on the fruit with the applied coating, and the controls that are slides with the application only of the polymer solution of the composition. Results Anthracnose (Cg) Distribution % of the states of the conidia of each sample in each temporal observation.

Continuation

The effect of the precipitated particles of citric acid in the polymeric coating on the anthracnose conidia is appreciable, reaching a decrease in pathogen germination after 7 days from 97.3% of the control to one of 7, 3% of the Antimicrobial Composition. This very high incidence in the germination of the conidia occurs in optimal conditions of application that must be considered when choosing the application method, being the immersion method clearly advantageous with respect to the aspersion by generating an application pressure when submerging the fruit in the liquid.

This antimicrobial behavior is perfectly compatible with pre-harvest, both applied by spraying to the plant and only on the fruit, since it generates an environment that is not conducive to the appearance of pathogens. It should be considered that since the polymeric coating is soluble in water, it can be washed off the fruit by rain, so some form of less soluble polymer compatible with the characteristics of the Antimicrobial Combination could be defined.

Among the different possibilities that exist for solid solutes soluble in water to react in the presence of moisture, citric acid, sodium chloride and sodium bicarbonate stand out for their availability, as well as in the group of polymers, polyvinyl alcohol and methylcellulose, all accepted by the international offices that regulate these substances.

The concept implicit in this innovation is to use the antimicrobial characteristics of some water-soluble solid solutes that, once precipitated in the polymer mesh of the coating, react in the presence of moisture. This concept does not exclude its use in products that are not going to be for human consumption, such as freshly sawn wood, which is attacked by multiple pathogens, which can be eliminated with the application of this invention, without necessarily being edible the polymer with the resulting precipitate inside. An example of this is the solution of methylcellulose in water at 1% w/w with a solution of sodium hydroxide in water at a low concentration (less than 4%). It is applied by spraying on freshly sawn wood, where it eliminates the pathogens found on the surface and leaves a thin polymeric coating that allows the wood to continue breathing and with precipitated particles inside, which maintains its antimicrobial characteristics in the presence of humidity.

Claims

1.- Antimicrobial composition that preserves the organoleptic conditions of fruit, vegetables and vegetables, CHARACTERIZED because it comprises at least one solvent, at least one soluble polymer and at least one solute soluble in water and in the solvent of the composition.

2. Composition according to claim 1, CHARACTERIZED in that the solvent is water, ethyl alcohol, or a mixture of both.

3. Composition according to claim 1, CHARACTERIZED because the soluble polymer is polyvinyl acetate, polyvinyl alcohol, methylcellulose, ethylcellulose, hydroxypropylcellulose, hydroxypropylmethylcellulose, ethylmethylcellulose, carboxymethylcellulose, soy hemicellulose, polymers derived from alginate, agar, chitosan, of aloe vera, cassava starch, corn, quinoa, collagen, or a mixture of these, or a natural biopolymer of high molecular weight biodegradable soluble in water.

4. Composition according to claim 1, CHARACTERIZED because the solute soluble in water and in the solvent of the composition is citric acid, sodium bicarbonate, sodium chloride, citrate salts, sorbic acid, potassium sorbate, benzoic acid and its derivatives soluble in water, sodium sulfate and its water-soluble derivatives, sodium metabisulfite, potassium metabisulfite, calcium sulfite, calcium hydrogen sulfite, potassium hydrogen sulfite, natamycin, dimethyl dicarbonate, potassium nitrite, sodium nitrite, sodium propionate, potassium propionate, calcium propionate, boric acid, ascorbic acid and their water-soluble derivatives, or other water-soluble salts or solutes that have antimicrobial behavior when dissolved, or a mixture of these.

5. Composition according to claims 1 and 3, CHARACTERIZED in that the concentration of the polymer in weight/weight percentage is less than 7% with respect to the solvent.

6. Composition according to claims 1 and 4, CHARACTERIZED in that the concentration of the solute soluble in water is less than 5% in weight/weight percentage with respect to the solvent.

7. Composition according to claims 1, 5 and 6, CHARACTERIZED in that the solvent is alcohol, the polymer is nitrocellulose and the solid solute is citric acid.

8. Composition according to claims 1, 5 and 6, CHARACTERIZED in that the solvent is alcohol, the polymer is nitrocellulose and the solid solute is sodium hydroxide.

9. Composition according to claim 1, 3, 5 and 6, CHARACTERIZED in that the solvent is water and the solid solute is sodium hydroxide.

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