SUPPRESSION OF ETHYLENE PRODUCTION IN HARVESTED FRUIT AND OTHER PRODUCE USING CO2-INFUSED WATER

Abstract

Fruit ripens as a result of the production of ethylene. It is often desirable to slow the ripening process in order to extend the shelf life of fruit to be sold. One method of slowing the production of ethylene is to increase the concentration of CO.sub.2 in the ambient atmosphere. However, this can endanger humans working with the fruit. Instead, a method of supplying CO.sub.2 to harvested fruit in a way which does not increase the concentration of atmospheric CO.sub.2 is provided. Water is infused with CO.sub.2 and then sprayed onto the fruit. The invention can more generally be applied to other grocery produce so as to reduce spoilage of the produce.

Claims

1. A method of slowing ripening of harvested fruit, comprising: infusing CO.sub.2 gas into water so as to create CO.sub.2-infused water; spraying the harvested fruit with the CO.sub.2-infused water; and repeatedly spraying the harvested fruit with the CO.sub.2-infused water.

2. The method of claim 1 wherein infusing CO.sub.2 gas into water comprises using hollow carbon fibers.

3. The method of claim 2 wherein the hollow carbon fibers create bubbles of CO.sub.2 of about 0.2 ?m in diameter.

4. The method of claim 1 wherein repeatedly spraying the harvested fruit with the CO.sub.2-infused water is carried out with a period of 30 to 60 minutes, each spraying being for a duration of 5 to 10 seconds.

5. The method of claim 1 wherein infusing CO.sub.2 gas into water comprises infusing CO.sub.2 gas to a concentration of about 1.4 g/L of water.

6. The method of claim 1 wherein spraying the harvested fruit with the CO.sub.2-infused water comprises spraying the CO.sub.2-infused water in droplets of 50 to 150 ?m diameter.

7. The method of claim 1 wherein spraying the harvested fruit with the CO.sub.2-infused water comprises spraying the harvested fruit while the harvested fruit is on display for purchase by consumers.

8. A method of slowing spoilage of grocery produce, comprising: infusing CO.sub.2 gas into water so as to create CO.sub.2-infused water; spraying the grocery produce with the CO.sub.2-infused water; and repeatedly spraying the grocery produce with the CO.sub.2-infused water.

9. The method of claim 8 wherein infusing CO.sub.2 gas into water comprises using hollow carbon fibers.

10. The method of claim 9 wherein the hollow carbon fibers create bubbles of CO.sub.2 of about 0.2 ?m in diameter.

11. The method of claim 8 wherein repeatedly spraying the grocery produce with the CO.sub.2-infused water is carried out with a period of 30 to 60 minutes, each spraying being for a duration of 5 to 10 seconds.

12. The method of claim 8 wherein infusing CO.sub.2 gas into water comprises infusing CO.sub.2 gas to a concentration of about 1.4 g/L of water.

13. The method of claim 8 wherein spraying the grocery produce with the CO.sub.2-infused water comprises spraying the CO.sub.2-infused water in droplets of 50 to 150 ?m diameter.

Description

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0009] Broadly, CO.sub.2 gas is infused in water to produce CO.sub.2-infused water. The CO.sub.2-infused water is then applied to harvested fruit by spraying the CO.sub.2-infused water onto the harvested fruit.

[0010] According to one embodiment of the invention, water is infused with CO.sub.2 to create CO.sub.2-infused water. The CO.sub.2 is infused into the water in an amount that results in maximum concentration, about 1.4 g/L at room temperature.

[0011] The CO.sub.2 is preferably infused into the water using hollow carbon fibers. Hollow carbon fibers create very small bubbles, or nano bubbles, on the order of 0.2 ?m in diameter. The small surface area of the CO.sub.2 nano bubbles allows very quick and efficient gas adsorption into the water.

[0012] The CO.sub.2-infused water is then sprayed onto harvested fruit, preferably in the form of water droplets of size 50 to 150 ?m diameter. The CO.sub.2-infused water is preferably sprayed so as to cover substantially the entire harvested fruit so as to maximize diffusion of CO.sub.2 into the cells of the fruit, although less than entire coverage will still result in diffusion of CO.sub.2 into the cells of the fruit and a slowing of the ripening process. The spraying is preferably carried out repeatedly with a period of 30 to 60 minutes between sprayings, each for a duration of 5 to 10 seconds, although the period between spraying and the duration of individual sprayings will vary depending on the size of the harvested fruit. The spraying regimen is continued until the fruit is sold, although there will likely be pauses in the spraying regimen such as when consumers are present.

[0013] The invention is particularly advantageous if the fruit is sprayed with the CO.sub.2-infused water while on display for purchase by consumers in a retail store. In such an environment, it is very difficult to use increased atmospheric CO.sub.2 levels to diffuse CO.sub.2 into harvested fruit without endangering humans, at least to effective concentrations of CO.sub.2. By spraying fruit in a retail environment with CO.sub.2-infused water, ethylene production and hence ripening in the fruit can be slowed without endangering humans, thereby extending the shelf life of the fruit.

[0014] The invention has been described as using hollow carbon fibers to infuse the CO.sub.2 gas in the water. Alternatively, other CO.sub.2 infusion methods can be used, such as the use of air stones. But depending on the method of CO.sub.2 infusion used, large quantities of gas can be lost to the atmosphere as large bubbles of CO.sub.2 rise through the water before being adsorbed. The use of hollow carbon fibers and the resulting nano bubbles increases the amount of gas adsorbed by the water.

[0015] The invention has been described in which the spraying is done with CO.sub.2-infused water droplets of 50 to 150 ?m diameter. Other water droplet sizes may be used, but these are less efficient. If the water droplet is too small, then the water can drift in air currents and not all of it will reach the fruit, or the CO.sub.2 may leave the solution because there is too high a drop in pressure as the water passes through the nozzle of the sprayer, or both. If the water droplet is too large then the water droplet may not adhere to the harvested fruit because the water droplet bounces off or rolls off the fruit, and a film of CO.sub.2-infused water does not cover the fruit. In either case (too small droplets or too large droplets), transfer of CO.sub.2 into the harvested fruit through the surface of the fruit is less effective when spraying is carried out with the CO.sub.2-infused water. However, the invention is still advantageous in that CO.sub.2 will still enter the cells of the fruit and suppress the production of ethylene, and therefore slow the ripening process, while minimizing increasing the CO.sub.2 of the surrounding atmosphere, but will be less than ideal than use of water droplets of 50 to 150 ?m diameter.

[0016] The invention has been described as spraying the CO.sub.2-infused water so as to cover substantially the entire harvested fruit. This may not always be possible, due for example to positioning of the harvested fruit or to time constraints. In such a case the invention will still be advantageous in that CO.sub.2 will still enter the cells of the fruit and suppress the production of ethylene, and therefore slow the ripening process, while minimizing increasing the CO.sub.2 of the surrounding atmosphere, but will be less than ideal than full exposure of the harvested fruit to the CO.sub.2-infused water.

[0017] The invention has been described as spraying the CO.sub.2-infused water onto harvested fruit. Alternatively, the CO.sub.2-infused water may be sprayed onto other grocery produce to be sold, such as vegetables. This reduces the production of ethylene in this other grocery produce, which increases the shelf life of the grocery produce before spoilage occurs.

[0018] The embodiments presented are exemplary only and persons skilled in the art would appreciate that variations to the embodiments described above may be made without departing from the spirit of the invention. The scope of the invention is solely defined by the appended claims.