Sunday, August 23, 2009


Use of solvents for extraction of active ingredients or removal of undesirable substances is one of the most common practice in the food industry. Water is the chosen solvent if the substance to be extracted or leached out is soluble in it. Other wise organic and inorganic solvents are required and depending on the solubility characteristics of the extractable material, different solvents are selected. The solvent extraction process generally involves use commercial Hexane to get soluble fractions, separation of the extract and desolventization to recover the extracted materials. Edible oil industry started using solvent extraction technology since 1930s for recovering oils from pressed residues of oil seeds and other oil bearing sources containing less than 20% oil.

Commercial Hexane is made up of 52% n-Hexane, 16% Methyl Cyclopentane, 16% of 3-Methyl Pentane, 13% of 2-Methyl Pentane and 3% Cyclohexane. It is one of the cheapest organic solvents available, being a distillate of petroleum industry. It is estimated that about 60 million tons of edible oils are produced by Hexane extraction technology and the most abundantly produced extracted oil is soy oil. Concerns have been raised regarding the dangers posed by presence of Hexane in extracted residues as well as in the edible oil products and without adequately analyzing the hazard potential, the industry is being damned. It is true that exposure of humans to Hexane can cause excessive inhalation through the lung route and many ill effects have been reported. A 15 minutes exposure to 800 ppm of Hexane can cause acute respiratory and eye problems,nausea, vertigo, head ache and such exposures are associated with neuropathy and other toxicity problems.

What causes concern to the food industry is the unsubstantiated claims that Hexane residues present in extracted foods pose dangers to the consumers. However the Environmental Protection agency of the US found no ill effect even when the residue was up to 0.2%, at least to the test animals. Cotton seed flour and hops extract for which maximum limits have been prescribed must not contain more than 60 ppm and 25 ppm of hexane respectively. WHO has not prescribed any limits for this solvent in any foods. No toxicity trial has ever implicated Hexane in any serious health disorders when foods containing low levels of residues are consumed orally. In fact people working in gas stations and those staying near by are more vulnerable to Hexane toxicity through inhalation. Probably the processing plants using Hexane as a solvent will have to be weary about the pollution they can cause if Hexane losses are not minimized during handling of this highly volatile solvent which can be any where between 0.15% to 0.5%. According to one estimate, the soy processing plants belonging to one of the giants in the US are responsible for an annual emission of more than 1 million pounds of Hexane to the environment. Annual Hexane loss by the edible oil industry is reported to be about 0.3 million tons. Still it is to be recognized that the Hexane level in the atmosphere rarely exceeds 2 parts per billion (ppb) whereas Hexane beyond 20 ppb only is considered undesirable.

Consumer scare mongering practice is neither good nor desirable based on inadequate data or misinterpreted information and must be checked in the interests of the consumer who has no where to go for getting at the truth. It is almost eight decades since solvent extraction process was established as a safe process and no evidence exists to implicate this technology in any human disaster. Of course use of organic solvents in general is not some thing industry favors but till alternative viable options are available, one has to live with this. Emergence of Super Critical CO2 Extraction technology does provide an option but the cost considerations rule out its use for low cost food material like oil bearing food sources. Damning a technology like the solvent extraction process, which provides bulk of the edible oil, a vital food constituent in the diet of mankind, based on unsubstantiated information, deserves to be frowned upon.


Anonymous said...

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