FIELD OF THE INVENTION

[0001] This invention relates to a produce preserver. The preserver controls ethylene, given off by produce in a package, by chemically reacting with the ethylene thereby removing the ethylene from the package atmosphere. The preferred preserver comprises calcium hypochlorite or sodium hypochlorite, citric acid, and a water carrier such as a humectant salt with high water activity or oligosaccharide

compounds.

BACKGROUND OF THE INVENTION

[0002] Ethylene is a gas that is given off by fruits, vegetables and flowers during senescence. Ethylene promotes the ripening and spoilage of the plants. Plants synthesize ethylene. Ethylene is a natural plant growth hormone which has a detrimental impact, even at low concentrations, on the product quality and shelf life of many fruits and vegetables during storage and distribution. Ethylene is sometimes referred to as the ripening or death hormone because it induces fruit ripening and accelerates fruit softening and senescence (aging). Ethylene can also cause a range of postharvest physiological disorders such as russet spotting on lettuce and scald on apples. Although ethylene is produced by all plants, the principal sources of the low levels of ethylene in the atmosphere are climatic fruits (fruits that ripen after harvest and are characterized by an increase in respiration rate and burst of ethylene production as they ripen), damaged or rotten produce and exhaust gases. Low temperature storage reduces the formation of ethylene by lowering the respiration rate and metabolic rates of the produce. Controlled atmosphere storage with the use of low oxygen and high carbon dioxide concentrations will suppress respiration rates and render the produce less sensitive to the effects of ethylene. The best way to extend the shelf life is to reduce or eliminate the ethylene in the storage atmosphere.

[0003] Patent publications dealing with absorbing ethylene are listed as follows: US Patent No. 8,057,586 to Powers et al., dated November 15, 2011 ; EP2044844 to Nonnenmacher Klaus Prof Dipl-I, dated April 8, 2009; EP031 1454 to Allen Davies & Co Limited, dated April 12, 1989; US Patent No. 4,848,928 to Ausnit, dated July 18, 1989; EP1 1 06233 to Degussa, dated June 13, 2001 ; EP2 52 5173 to Whirlpool Co, dated November 21 , 2012; US Patent o. , 152,902 to Wood et al., dated April 10, 2012.

[0004] Packaging technologies designed to scavenge or absorb ethylene from the surrounding environment of packaged produce have been developed. The most widely used ethylene scavenging packaging technology today is in the form of a sachet containing potassium permanganate on an inert porous support such as alumina or silica gel at a level of about 5%. The ethylene is scavenged through an oxidation reaction with the potassium permanganate to form carbon dioxide and water.

Although these permanganate based ethylene absorbers are effective at removing ethylene, their use is limited as it is accompanied by undesirable effects. These include the possible migration of the potassium permanganate from the sachet onto the produce, lack of specificity to ethylene resulting in undesirable aromas being scalped and a general lack of enthusiasm for the use of sachets. Other types of sachet based ethylene scavenging technologies utilize activated carbon with a metal catalyst such as palladium which converts the ethylene to acetaldehyde. BRIEF SUMMARY OF THE INVENTION

[0005] This invention relates to an ethylene absorber comprising at least one member selected from the group consisting of calcium hypochlorite, sodium hypochlorite, potassium hypochlorite, magnesium hypochlorite; acid and a hygroscopic material, that easily absorbs and releases water, such as a humectant salt with sufficiently high water activity.

[0006] In another embodiment, the invention relates to a method of preserving produce comprising placing the produce in a sealed package with a sealed container that allows gaseous contact between the produce in the container and an ethylene absorber comprising at least one member selected from the group consisting of potassium hypochlorite, magnesium hypochlorite, calcium hypochlorite or sodium hypochlorite; an acid, and hygroscopic material as a water carrier and release substance.

DETAILED DESCRIPTION OF THE INVENTION

[0007] An ethylene absorber in accordance with the invention has numerous advantages over the prior art. The invention provides effective controls of ethylene in fruit, flower, and vegetable packages. The invention is relatively inexpensive and reacts rapidly enough to maintain low ethylene gas content in a fruit or other produce package. The absorber may be utilized as in the form of a patch or label on the inside of the package or as a sachet. The chemicals utilized in the ethylene absorber are generally safe and low-cost. The reactants absorbed by the instant absorber are safe for the user. In embodiments of thi s disclosure, the ethylene absorber will react irreversibly with ethylene and not release ethylene at a later time. The ethylene absorber extends the shelf life of fruit, vegetables and fl owers. These advantages and others will be apparent from the detailed description below.

[0008] Suitable reactive hypochlorite materials for the invention include calcium hypochlorite, sodium hypochlorite, potassium hypochlorite and magnesium

hypochlorite. The preferred reactive materials utilized in the invention ethylene absorber are calcium hypochlorite and sodium hypochlorite because they are very reactive and safe with food products. The hypochlorite materials are combined with an acid such as citric acid in a preferred embodiment and will react to form a

hypochlorous acid. The hypochlorous acid reacts with ethylene gas to form

chloroethanol. Generally the chlorocthanol is then absorbed by a reaction products absorber. The reaction of the hypochlorous acid is generally considered to require water to be present. A water carrier making water available for the reaction is generally considered necessary for the reaction to proceed. Typical hygroscopic water carrier materials are zinc chloride, sodium chloride, sugar a monosaccharide, a disaccharide, or an oligosaccharide. These carrier materials are hygroscopic (i.e. they attract and retain water), absorb significant amounts of water by weight by forming saturated solutions, and at the same time are able to release the water easily when placed in low relative humidity ( RH) environments thereby acting as humectants to form high water activity solutions. Common aggressive desiccant materials such as clays, zeolites, and molecular sieves are not suitable because even though they absorb significant amounts of water by weight, they restrict the water mobility and availability, do not release it easily and thus do not generate high water activity, resulting in low RH environments. Aggressive desiccants are not preferred because while they attract water, they do not make the water available for the other reactants. Preferred water carrier materials are calcium and zinc chloride as they will attract water quickly and then release it readily to provide sufficient moisture to the other reactants hence allowing the reaction to proceed.

[0009] Any acid that will react with the hypochlorite to produce the hypochlorous acid may be utilized in the invention. Suitable materials include carboxylic acid, oxalic acid, and carboxylic acids such as acetic acid, formic acid and benzoic acid. A preferred acid has been found to be citric acid as it is very effective, low in cost, safe and available in food grade.

[0010] The reaction products may be absorbed onto any suitable substrate that has efficient absorption of the reaction products. Suitable materials are activated carbon, silica gel, Chabazite, molecular sieve, and activated alumina. Activated carbon and silica gel are preferred for their ability to absorb and hold large quantities of reaction products for the weight of the material.

[001 1] The hypochlorite and acid may be utilized in any combination that will react to rapidly and effectively remove ethylene. Generally, the sodium hypochlorite is in about a 10 to 15% chlorine solution. The calcium hypochlorite is dry. The quantities utilized, when used with citric acid, are typically between about equal quantities of citric acid and the sodium hypochlorite solution and up to about three times the amount by weight of hypochlorite solution as the citric acid.

[0012] In accordance with an aspect of the invention a method and material for the irreversible absorption of ethylene are described. The preferred calcium hypochlorite or sodium hypochlorite and acid such as citric acid will react to form hypochlorous acid. Hypochlorous acid will readily react with ethylene gas to form chlorocthanol. Activated carbon is added to the ethylene absorber formulation to absorb the reaction products which are primarily chloroethanol. Other absorbents such as zeolites and molecular sieves also can be used to absorb the ethylene reaction products.

[0013] The ethylene reactive material in accordance with an aspect of the invention may be placed in any suitable container in the package of vegetables, fruit, or flowers. Vegetables, fruit, and flowers will be referred to herein as produce. Typically the ethylene absorbent material is placed into a container that provides gaseous communication with the packaged produce that is intended to be protected by the absorpti on of ethylene. The produce package itself wou ld be a typical packaging material that provides substantial protection from flow of water vapor and oxygen into the package. Typical package materials are nylon, polyesters, polycarbonates, and polyolefin such as polyethylene. The container for the ethylene reactive material of the invention would be a capsule, patch, sachet, or any other container suitable for placing into a package of produce. The container for the ethylene absorber would have at least one side that is in gaseous communication with the contents of the package. Sachets formed of microporous material such as Tyvek® and other spun bonded or stretched microporous material are known for use in sachets for food and medicine packaging. The absorbent also may be placed in a label or patch that would be adhesively placed on the inside of the container where it would not be loose with the produce. The formation of sachets, patches and labels is known in the art.

[0014] The fol lowing exampl es are il lustrative and not exh au sti ve of ways of practicing the invention. Parts and percentages are by weight unless otherwise indicated. The moisture source is 2.5 g of water on blotter paper that is placed into the pouch. In actual use, with produce, water would not be necessary as the produce would provide sufficient water.

[0015] Example 1

.4 grams calcium hypochlorite

.4 grams citric acid

.4 grams anhydrous calcium chloride

[0016] The above blend was mixed together and placed in a 15 liter pouch containing 100 ppm of ethylene gas in air with a 2.5 gram moisture source. This formulation reduced the ethylene content at room temperature from 100 ppm to 1 .0 ppm within 7 days. The analysis was conducted by gas chromatography.

[0017] Example 2

.2 grams calcium hypochlorite

.2 grams citric acid

.2 grams anhydrous calcium chloride

[0018] The above blend was mixed together and placed in a 1 5 liter pouch containing 100 ppm of ethylene gas in air with 2.5 gram moisture source. This formulation reduced the ethylene content at room temperature from 100 ppm to 50 ppm within 10 days. The analysis was conducted by gas chromatography.

[0019] Example 3

1.0 grams sodium hypochlorite solution (1 0-15% chlorine)

2.4 grams silica gel, B type .4 grams citric acid

.4 grams anhydrous calcium chloride

[0020] The above blend was mixed together and placed in a 15 liter pouch containing 100 ppm of ethylene gas in air with 2.5 gram moisture source. This formulation reduced the ethylene content at room temperature from 100 ppm to 3 ppm within 10 days. The analysis was conducted by gas chromatography.

[0021] Example 4

.4 grams calcium hypochlorite

.4 grams citric acid

.4 grams anhydrous calcium chloride

[0022] The above blend was mixed together and placed in a 15 liter pouch containing 100 ppm of ethylene gas in air with 2.5 gram moisture source. This formulation reduced the ethylene content from 100 ppm to 1 1 ppm within 2 days at 10· C. The analysis was conducted by gas chromatography.

[0023] Example 5

.8 grams calcium hypochlorite

.8 grams citric acid

.8 grams anhydrous calcium chloride

[0024] The above blend was mixed together and placed in a 15 liter pouch containing

100 ppm of ethylene gas in air with 2.5 gram moisture source. This formulation reduced the ethylene content from 100 ppm to 2 ppm within 2 days at 10· C. The analysi was conducted by gas chromatography.

[0025] Example 6

1.0 grams sodium hypochlorite solution (1 0- 1 5% chlorine)

2.4 grams silica gel, B type

.4 grams citric acid

.4 grams anhydrous calcium chloride

[0026] The above blend was mixed together and placed in a 15 liter pouch containing 100 ppm of ethylene gas in air with 2.5 gram moisture source. This formulation reduced the ethylene content from 1 00 ppm to less than 1 ppm within 2 days at 10· C. The analysis was conducted by gas chromatography.

[0027] Example 7

2.0 grams sodium hypochlorite solution (10-15% chlori ne)

4.8 grams silica gel, B type

.8 grams citric acid

.8 grams anhydrous calcium chloride

[0028] The above blend was mixed together and placed in a 15 l iter pouch containing 100 ppm of ethylene gas in air with 2.5 gram moisture source. This formulation reduced the ethylene content from 100 ppm to less than 1 ppm within 2 days at 10· C. The analysis was conducted by gas chromatography.

[0029] Example 8 .4 grams calcium hypochlorite

.4 grams citric acid

.4 grams anhydrous calcium chloride

3.0 grams St. Cloud 1 4 X 50 chabazite dried at 120· C for 18 hours

[0030] The above blend was mixed together and placed in a 15 liter pouch containing 1 00 ppm of ethylene gas in air with 2.5 gram moisture source. This formulation reduced the ethylene content from 100 ppm to 10 ppm within 2 days at 10· C. The analysis was conducted by gas chromatography.

[0031] Example 9

.4 grams calcium hypochlorite

.4 grams citric acid

.4 grams anhydrous calcium chloride

4.0 grams activated alumina UOP D201 7 X 12

[0032] The above blend was mixed together and placed in a 15 liter pouch containing 1 00 ppm of ethylene gas in air with 2.5 gram moisture source. This formulation reduced the ethylene content from 100 ppm to 1 1 ppm within 2 days at lO ^' C. The analysis was conducted by gas chromatography.

[0033] Example 10

.4 grams calcium hypochlorite

.4 grams citric acid

.4 grams anhydrous calcium chloride

2.0 grams silica gel, type B [0034] The above blend was mixed together and placed in a 1 5 liter pouch containing 100 ppm of ethylene gas in air with 2.5 gram moisture source. This formulation reduced the ethylene content from 100 ppm to less than 1 ppm within 2 days at 10· C. The analysis was conducted by gas chromatography.

[0035] Example 1 1

.4 grams calcium hypochlorite

.4 grams citric acid

.4 grams anhydrous calcium chloride

.5 grams 1 3X molecular sieve

[0036] The above blend was mixed together and placed in a 15 liter pouch containing

100 ppm of ethylene gas in air with 2.5 gram moisture source. This formulation reduced the ethylene content from 100 ppm to 2 ppm within 2 days at 10· C. The analysis was conducted by gas chromatography.

[0037] Example 12

.4 grams calcium hypochlorite

.4 grams citric acid

.4 grams anhydrous calcium chloride

.5 grams 1 3X molecular sieve

[0038] The abov e blend was mixed together and placed in a 15 liter pouch containing 100 ppm of ethylene gas in air with 2.5 gram moisture source. This formulation reduced the ethylene content from 00 ppm to 10 ppm within 2 days at 10· C. The analysis was conducted by gas chromatography.

[0039] Example 13

.4 grams calcium hypochlorite

.4 grams citric acid

.4 grams anhydrous calcium chloride

.5 grams St. Cloud 14 X 50 chabazite dried at 120· C for 18 hours

[0040] The above blend was mixed together and placed in a 1 5 liter pouch containing 100 ppm of ethylene gas in air with 2.5 gram moisture source. This formulation reduced the ethylene content from 100 ppm to 2 ppm within 2 days at 10· C. The analysis was conducted by gas chromatography.

DISCUSSION OF EXAMPLES

[0041 ] It was determined that the primary reaction product of ethylene gas and the hypochlorous acid is chloroethanol. The hypochlorous acid is formed by the reaction of the calcium hypochlorite or sodium hypochlorite and an acid such as citric acid. Absorbents were added to the reaction blend to absorb these reaction products. The absorbents tested were activated carbon, silica gel, chabazite, 13X molecular sieve and activated alumina.

[0042] The Examples ail illustrate the effectiveness of the invention materials for removing ethylene from the atmosphere of a package in a rapid and irreversible manner.