Oxygen, Ethylene and Carbon dioxide

scavenging techniques

ABHISHEK KATAGIPh.D. (Hort.)UHS13PGD57

Packaging materials have traditionally been chosen to avoid unwanted

interactions with food.

Food packaging exists to make our lives easier. We need packaging to

protect foods from the outside environment, for convenience and to

communicate information to consumers about the food inside the package.

Migration of packaging materials components into the product, absorption

of product components into the packaging material, high permeability to

moisture, vapors and gases, as well as to light, are undesired in most of the

common packaging systems, such as metal cans, glass bottles and jars and

most plastic and composite packages.

Introduction

New packaging systems are called active, smart or intelligent

packaging

“Active packaging includes components of packaging systems

that are capable of scavenging oxygen; absorbing carbon

dioxide/ releasing carbon dioxide, moisture, ethylene and

maintaining temperature control and/or compensating for

temperature changes”.

Maria, Portugal

To correct deficiencies that exist in passive packaging

To deliberately interact with the product and respond to changes.

Product quality, safety and preservation

Oxygen and ethylene scavengers, ethanol emitters, carbon dioxide generators and

absorbers,

Anti-microbial surfaces and time-temperature integrators

Optimum conditions to which a food is exposed, while passive packaging is used as

an effort to minimize the deleterious effects of a limited number of external variables

such oxygen, water and light

Active or smart packaging is designed to….

Selected examples of active packaging systems

Active packaging System mechanisms food Applications

Oxygen scavengers Iron based, Metal/acidNylon MXD6, Metal (e.g. platinum) catalystAscorbate/metallic saltsEnzyme based

Bread, cakes, cooked rice,biscuits, pizza, pasta,cheese, cured meats andfish, coffee, snack foods,dried foods and beverages

Carbon dioxidescavengers/emitters

Iron oxide/calcium hydroxideFerrous carbonate/metal halideCalcium oxide/activated charcoalAscorbate/sodium bicarbonate

Coffee, fresh meats and fish,nuts and other snack foodproducts and sponge cakes

Ethylene scavengers

Potassium permanganateActivated carbonActivated clays/zeolites

Fruit, vegetables and otherhorticultural products

Preservativereleasers

Organic acidsSilver zeoliteSpice and herb extractsBHA/BHT antioxidantsVitamin E antioxidantChlorine dioxide/sulphur dioxide

Cereals, meats, fish, bread,cheese, snack foods, fruitand vegetables

Ethanol emitters

Encapsulated ethanol Pizza crusts, cakes, bread,biscuits, fish and bakeryproducts

Moisture absorbers

PVA blanketActivated clays and mineralsSilica gel

Fish, meats, poultry, snackfoods, cereals, dried foods,sandwiches, fruit andvegetables

Flavour/odourabsorbers

Cellulose triacetate, Acetylated paperCitric acid, Ferrous salt/ascorbateActivated carbon/clays/zeolites

Fruit juices, fried snackfoods, fish, cereals, poultry,dairy products and fruit

Temperature controlpackaging

Non-woven plastics, Double-walled containers, Hydrofluorocarbon gasQuicklime/water, Ammonium nitrate/water, Calcium chloride/waterSuper corroding alloys/salt waterPotassium permanganate/glycerine

Ready meals, meats, fish,poultry and beverages

Cont..

Maria, Portugal

Oxygen scavengers (also referred to as oxygen absorbers) -- food product

quality by decreasing food metabolism, reducing oxidative rancidity, inhibiting

undesirable oxidation of labile pigments and vitamins, controlling enzymic

discoloration and inhibiting the growth of aerobic microorganisms.

Small sachets or self adhesive labels that are placed inside modified

atmosphere packs to help extend product life (notably cooked meats) and help

improve product appearance.

The reduction of oxygen inhibits aerobic organisms, especially mold, and

prevents oxidative rancidity.

Maria, Portugal

A scavenger in chemistry is a chemical substance added to a mixture in order to remove or inactivate impurities or unwanted reaction products

Table : Selected oxygen scavenger systems

Maria, Portugal

Cont…

Principles

Easily oxidizable --- remove O2 by means of a chemical reaction

In sachets made of a material highly permeable to air but it can also be

included in bottle closures or in the plastic film matrix

Use of scavengers led to faster reduction and to lower levels of residual

oxygen, as compared to nitrogen flushing.

These chemical systems often react with water supplied by the food to

produce a reactive hydrated metallic reducing agent that scavenges oxygen

within the food package and irreversibly converts it to a stable oxide.

The most common substances used are iron powder and ascorbic acid.

O2 scavenger several requirements:-

- Be safe and not produce toxic substances or odors

- Be handled easily

- Be compact in size and absorb a large amount of oxygen

- Have an appropriate rate of oxygen absorption, and

- Be economic.

The scavengers may be of self-reaction type or moisture dependent

Scavengers also differ in the reaction speed: from immediate action (0.5 to 1 day) to slow action (4 to 6 days); on the application :: particularly the moisture content of the food; and on the function :: i.e., oxygen scavenging only or dual function, such as absorbing or generating carbon dioxide, besides removing the oxygen.

oxygen scavengers --- capable of reducing oxygen levels to less than 0.01% which is much lower that the typical 0.3–3.0% residual oxygen levels achievable by modified atmosphere packaging (MAP).

The oxidation mechanism of iron powder can be expressed as follows:

The iron powder is separated from the food by keeping it in a small, highly

oxygen permeable sachet that is labelled ‘Do not eat’ and includes a diagram

illustrating this warning.

The main advantage of using such oxygen scavengers is that they are

capable of reducing oxygen levels to less than 0.01%

Oxygen scavengers can be used alone or in combination with MAP

Non-metallic scavengers include those that use organic reducing agents such

as ascorbic acid, ascorbate salts or catechol.

Enzymic oxygen scavenger systems using either glucose oxidase or ethanol

oxidase,

Day, USA

Selection of the oxygen scavenger, considerations :-

The nature of the food, such as size, shape and weight

The moisture content and water activity

The initial (residual) oxygen content in the package head-space

The amount of oxygen dissolved in the product

The maximum allowable oxygen intake to end product shelf-life

The packaging material permeability to oxygen.

EVOH as an oxygen barrier layer for prolonging the shelf-life of foods

plastic packaging systems (containing ethylene-vinyl alcohol copolymer (EVOH)

Oxygen absorber----Pizza

Table. Properties and types of FreshMaxTM and FreshPaxTM O2 scavengers.

Fig . AgelessTM formats available: sachet, pressure-sensitive label and card.

FreshPaxTM and FreshMaxTMOxygen scavenger Label

Figure. Crown oxygen scavenger from Darex (W.R.Grace).

• Oxygen scavenging sachets ---- disadvantage ---- accidental ingestion ----

hampered their commercial success, particularly in North America and Europe.

Soln: Development of oxygen scavenging adhesive labels (increased

safety)

Uses : Sliced cooked and cured meat and poultry products, which are

particularly sensitive to deleterious light and oxygen-induced colour changes

Coffee, pizzas, speciality bakery goods and dried food ingredients (Hirst,

1998).

Cakes, breads, biscuits, croissants, fresh pastas, cured fish, tea, powdered

milk, dried egg, spices, herbs, confectionery and snack food. (Day, 2001).

Self Adhesive Oxygen Absorbing labels

Nuts and many high-oil content, processed foods have saturated fats which can oxidize, creating an off-flavor and texture issues. Maintaining the fresh, out-of-the-oven consumer appeal and texture can be achievedduring extended shelf life using MultisorbÕsinnovative active packaging technology.

Powders, such as baby formulas and geriatric meal replacements, have traditionally relied on unhealthy trans-fats to maintain shelf life. Active packaging technology allows formula producers to maintain a desired shelf life while eliminating the use of trans-fats.

powderpowder

Organic foods made without preservativesAnd ---- loss of flavor, color, moisture and nutrients.

---extend shelf life and lengthen the distribution chain of goods without additives or preservatives, thus maintaining organic product integrity.

FreshCardTM

FreshMax¨ FreshPax

“Reduced Oxygen Packaging” means:

(i) The reduction of the amount of oxygen in a package by removing

oxygen; displacing oxygen and replacing it with another gas or

combination of gases; or otherwise controlling the oxygen content to a

level below that normally found in the surrounding, 21% oxygen

atmosphere

(ii) Food for which the hazards of Clostridium botulinum and Listeria

monocytogenes require control in the final packaged form

Principles

Ethylene is a plant hormone that accelerates the respiration rate and subsequent

senescence of horticultural products such as fruit, vegetables and flowers. Many of

the effects of ethylene are necessary (e.g. induction of flowering in pineapples and

colour development in citrus fruits, bananas and tomatoes) but in most

horticultural situations it is desirable to remove ethylene or to suppress its effects.

Ethylene is a very reactive compound that can be altered in many ways, such as

chemical cleavage and modification, absorption, adsorption, etc. This creates a

diversity of opportunities for commercial applications for the removal of ethylene

Ethylene

scavengers

There are a number of ethylene removal technologies available:

– Catalysts. Often based on platinum/alumina, these operate at elevated

temperature (> 200ºC) and catalytically oxidise ethylene to carbon dioxide and

water.

--- Use of photocatalytic oxidation of ethylene using titanium dioxide, which

can occur at room temperature

-- Stoichiometric oxidising agents. Mostly based on potassium permanganate,

which again oxidises ethylene and is itself reduced.

Sorbents: Sorption of the ethylene and are often based on high surface area

materials, including activated carbon, clays and zeolites.

Ethylene Blocking Technologies

1-Methylcyclopropene (1-MCP). 1-MCP is the most widely used

commercial volatile ethylene inhibitor, which blocks ethylene binding

sites.

Silver thiosulfate (STS). The use of this material is largely restricted to

cut flowers and it is sold commercially under the trade name Chrysal

AVB®.

Aminoethoxyvinylglycine (AVG). This material is sold commercially as

ReTain® and acts as a plant growth regulator by blocking the production

of ethylene in the plant tissue

Table : Selected ethylene scavenger systems

Commercial examples

Potassium permanganate-based scavengers:-

KMnO4 are available in sachets for packages or blankets for storage

chambers--- not incorporated into food

Immobilized in-- inert substrate such as alumina or silica gel-- 4 – 6%.

The performance and useful life of the scavengers depend on the substrate

surface area and the content in permanganate.

Potassium permanganate oxidises ethylene to acetate and ethanol and in the

process changes colour from purple to brown, and hence indicates its

remaining ethylene scavenging capacity

Ethylene Control, Inc. (USA) ---scavenging capacities: 5g, 9g and 28g,

respectively --- boxes up to 10 lb, 30 lb and 50 lb of produce (one single

sachet per box is considered enough for protection).

Air Repair from DeltaTrak, Inc. -- alumina beads impregnated with

potassium permanganate --- packets of 5g and 8g for boxes, tubes of 5 in.

for display cases and small coolers and 20 in tubes for walk-in coolers, as

well as blankets and bulk beads available by the pound.

Figure. Sachet of ethylene scavenger from Ethylene Control, Inc.

Activated carbon-based scavengers

Ethylene can be removed by a system using various metal catalysts on

activated carbon. This type of scavenger is more popular in Japan.

Examples:-

-- SendoMate from Mitsubishi, which is based on a palladium catalyst

-- Hatofresh System from Honshu Paper, which is based on activated

carbon impregnated with bromine-type inorganic chemicals

-- Neupalon from Sekisui Jushi (Japan)

Activated earth-based scavengers

--Finely dispersed clay embedded in polyethylene films or bags that are used for

fresh produce----clays, pumice, zeolites, coral, ceramics, sand, etc.

-- Adsorb the ethylene, they also open pores within the plastic layer---ethylene

will diffuse much more rapidly through open pore spaces within the plastic than

through the plastic itself, it should be expected that ethylene will diffuse out of

these bags faster than through pure polyethylene bags.

Commercial examples: Orega bag (Korea), Evert-Fresh Bags made of oya

clay dispersed within polyethylene film matrix (USA), FH from Thermo Co., and

many others.

Dual-action ethylene scavenger and moisture absorber ( Japan, Sekisui Jushi

Ltd.)

--- Neupalon™ sachets --- activated carbon, a metal catalyst and silica gel and are

capable of scavenging ethylene as well as acting as a moisture absorber

--- Equilibrium modified atmosphere is likely to develop within these bags

compared with common polyethylene bags, especially if the produce has a high

respiration rate.

[Improve produce shelf life and reduce headspace ethylene independently of any

ethylene absorption or adsorption]

Carbon dioxide generators and absorbers

Principles

Carbon dioxide generators --- packaging for fresh produce where an increased

concentration of CO2, combined with decreased O2 concentration, reduces the

respiration rate thus increasing the product shelf-life

-- Emitters is in the packaging of meat products where a high level of CO2 may

inhibit microbial growth.

--Commercial solutions commonly used are the incorporation of a one-way valve

and more recently, the inclusion of a CO2 absorbing sachet.

Removal of CO2 is needed, as in the case of

roasted ground coffee. Substantial quantities of CO2 are released on grinding

coffee, which must be removed from the package to avoid pressure build up

and bursting, in the case of flexible pouches.

A mixture of calcium oxide and activated charcoal -- coffee pouches to

scavenge carbon dioxide but dual-action oxygen and carbon dioxide

scavenger sachets and labels are more common and are commercially used

for canned and foil pouched coffees in Japan and the USA (Day, 2003;

Rooney, 1995)

Dual-action sachets and labels typically contain iron powder for scavenging

oxygen and calcium hydroxide, which scavenges carbon dioxide when it is

converted to calcium carbonate under sufficiently high humidity conditions

Commercial examples

Examples of generators or emitters include: Ageless G, Toppan C and

Vitalon GMA, although most of the carbon- and earth-activated based

ethylene absorbers also claim carbon dioxide absorption capacity.

Ageless G is a self-working type, based on ascorbic acid oxidation

mechanism, and absorbs oxygen and generates an equal volume of CO2.

Examples of absorbers include Ageless E, which also functions as oxygen

scavenger.

It is based on powdered iron and calcium hydroxide

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