Epoxidized soybean oil, better known by its acronym, ESBO, is a plasticizer

Plasticizer

Plasticizers or dispersants are additives that increase the plasticity or fluidity of the material to which they are added; these include plastics, cement, concrete, wallboard, and clay. Although the same compounds are often used for both plastics and concretes the desired effects and results are...

 used in polyvinyl chloride

Polyvinyl chloride

Polyvinyl chloride, commonly abbreviated PVC, is a thermoplastic polymer. It is a vinyl polymer constructed of repeating vinyl groups having one hydrogen replaced by chloride. Polyvinyl chloride is the third most widely produced plastic, after polyethylene and polypropylene. PVC is widely used in...

 (PVC) plastic

Plastic

A plastic material is any of a wide range of synthetic or semi-synthetic organic solids used in the manufacture of industrial products. Plastics are typically polymers of high molecular mass, and may contain other substances to improve performance and/or reduce production costs...

s. It serves as a plasticizer and as a scavenger for hydrochloric acid

Hydrochloric acid

Hydrochloric acid is a solution of hydrogen chloride in water, that is a highly corrosive, strong mineral acid with many industrial uses. It is found naturally in gastric acid....

 liberated from PVC when the PVC undergoes heat treatment.

A few EU surveys have shown fairly high levels of ESBO in foods, in which about 4% were above the current specific migration limit (SML) for ESBO of 60 mg/kg and about 15% of the samples were above 30 mg ESBO/kg food. High migration levels might lead to an intake that exceeds the existing Tolerable Daily Intake of 1 mg/kg body weight/day.

Manufacturing process

ESBO is manufactured from soybean oil through the process of epoxidation. The reason why vegetable oils are widely used as plasticizers is because the high numbers of carbon-carbon double bonds present in vegetable oils make them a good target for manipulation into some other useful products like in this case - from soybean oil into epoxidized soybean oil. The epoxide

Epoxide

An epoxide is a cyclic ether with three ring atoms. This ring approximately defines an equilateral triangle, which makes it highly strained. The strained ring makes epoxides more reactive than other ethers. Simple epoxides are named from the parent compound ethylene oxide or oxirane, such as in...

 group is more reactive than double bond, thus providing a more energetically favorable site for reaction and making the oil a good hydrochloric acid scavenger and plasticizer. Usually a peroxide

Peroxide

A peroxide is a compound containing an oxygen–oxygen single bond or the peroxide anion .The O−O group is called the peroxide group or peroxo group. In contrast to oxide ions, the oxygen atoms in the peroxide ion have an oxidation state of −1.The simplest stable peroxide is hydrogen peroxide...

 or a peracid is used to add an atom of oxygen and convert the -C=C- bond to an epoxide group.

Metal closures incorporate a ring-shaped gasket formed from a bead of liquid plastisol containing up to 40% ESBO which is moulded into the correct profile in the closure shell using a hot punch, then fused by passing through an oven at 200°C for 90 seconds. PVC starts to break down at this high temperature and releases hydrogen chloride. ESBO functions as a stabilizer to scavenge this hydrogen chloride to prevent the autocatalytic breakdown of the polymer. It also functions as a plasticizer.

Food safety alert

A Swiss survey done in June 2005 had shown that migration of ESBO into foods could reach up to 1,170 mg/kg.

Rapid Alert System in Food and Feed (RASFF) had also reported cases of food product rejection in EU for exceeding SML under EU Legislation (EC/2002/72).

Legislation

In Europe, plastics are regulated by the Commission Directive 2002/72/EC which consolidates Commission Directive 90/128/EEC and its seven amendments (Directives 92/39/EEC, 93/9/EEC, 95/3/EEC, 96/11/EEC, 1999/91/EC, 2001/62/EC and 2002/17/EC). These amendments mainly modified the lists of authorized substances such as monomers and additives.

Directive 2002/72/EC establishes a specific migration limit for ESBO of 60 mg/kg. However in the case of infant formula and follow-on formula as defined by Directive 91/321/EEC or products containing processed cereal-based foods and baby foods for infants and young children as defined by Directive 96/5/EC, the SML is lowered to 30 mg/kg. This is because babies have higher ratio of food consumption per body weight.

Uses

Food products that are stored in glass

Glass

Glass is an amorphous solid material. Glasses are typically brittle and optically transparent.The most familiar type of glass, used for centuries in windows and drinking vessels, is soda-lime glass, composed of about 75% silica plus Na2O, CaO, and several minor additives...

 jars with metal

Metal

A metal , is an element, compound, or alloy that is a good conductor of both electricity and heat. Metals are usually malleable and shiny, that is they reflect most of incident light...

 lids need a gasket

Gasket

thumb|sright|250px|Some seals and gaskets1. [[o-ring]]2. fiber [[Washer |washer]]3. paper gaskets4. [[cylinder head]] [[head gasket|gasket]]...

 to make a good seal and the gasket is usually made from PVC. It forms an airtight seal preventing microbiological

Microorganism

A microorganism or microbe is a microscopic organism that comprises either a single cell , cell clusters, or no cell at all...

 and other contamination

Contamination

Contamination is the presence of a minor and unwanted constituent in material, physical body, natural environment, at a workplace, etc.-Specifics:"Contamination" also has more specific meanings in science:...

. ESBO is one of the additives used in the PVC gasket. It serves as a plasticizer and a scavenger for hydrochloric acid released from PVC when the food product undergoes sterilization

Sterilization (microbiology)

Sterilization is a term referring to any process that eliminates or kills all forms of microbial life, including transmissible agents present on a surface, contained in a fluid, in medication, or in a compound such as biological culture media...

.

Toxicity

The tolerable daily intake (TDI) of ESBO defined by the Scientific Committee on Food (SCF) of the EU is 1 mg/kg body weight. This value is based on a toxicological assessment performed by the British Industrial Biological Research Association (BIBRA) in the late 1997. Repearted oral administration had been shown to affect the liver, kidney, testis and uterus. According to the conventional European rules for food packaging materials, the TDI became a basis for the SML of 60 mg/kg.