Writing in Food Chemistry, Danish researchers reported that rhamnogalacturonan I extracted in large quantities from potato pulp waste could provide a new generation of food ingredients and functional hydrocolloids. They said that until now undegraded RG I has only been extracted in small amounts, which has limited the application possibilities for the ingredient.
The Danish team noted that potato pulp “is an underutilized material produced in large quantities by potato starch factories,” which they believe could be put to use as a new source of pectin like fibres. They explained that their new research has developed a new large-scale extraction process which will provide large quantities of readily available, undegraded rhamnogalacturonan I (RG I) from potato pulp.
“The main advantage of the method described in this paper is that RG I is extracted in what we expect is its native, intact form,” said the researchers, led by Peter Ulvskov from University of Copenhagen, Denmark.
“None of its functional properties are lost and it may be more amenable for further modifications and tailoring to suit specific desired pectic properties such as stabilizing and gelling capabilities, and as viscosity aid, to name a few,” they explained.
Ulvskov and his team explained that potato pulp is produced in large quantity as a by-product of the potato starch industry. They said that in Europe alone around one million tons of potato pulp are produced every year – of which only a minimal amount is utilised.
However, they said that around 30% of industrial potato pulp has is made up of dietary fibres which could be used to obtain novel ingredients with structures and functional properties that complement other plant-derived fibres currently commercially available on the food ingredients market.
Previous research has shown that potato fibre is especially rich in rhamnogalacturonan I, however such native RG I cannot be isolated from pectins obtained by traditional industrial extraction procedures as they are often performed at low pH – causing degradation of RG I side chains “and inevitably causing degradation of the native RG I molecule.”
It has been suggested that the functional properties of lab extracted RG I can be tailored to meet specific needs in food formulations through removing or preserving of particular side chains, however the researchers noted that such knowledge is of little use without a way to extract RG I on a larger scale.
“RG I in its native form has to our knowledge only been isolated in laboratory scale ... In order to obtain RG I in its native form – i.e. with a full complement of side chains – a gentle extraction process needs to be established,” said Ulvskov and his team.
The researchers said that the procedure for large-scale extraction of unmodified RG I from industrial potato waste included the enzymatic starch removal using purified Termamyl, enzymatic RG I solubilization using a highly purified polygalacturonase, and finally purification using depth filtration and ultrafiltration.
They added that the extracted RG I has a high molecular weight and a monosaccharide composition comparable to RG I extracted by laboratory analytical extraction procedures.
“The large amount of RG I available by the presented method allows for thorough structure-function analyses and tailoring of RG I to specific functionalities,” they explained.
“We need in particular to understand the in vitro self assembly properties of RG I reported here so that next generation food ingredients and functional hydrocolloids can be designed using native RG I as the raw material,” they concluded.
Published online ahead of print, doi: 10.1016/j.foodchem.2011.09.106
“Large-scale extraction of rhamnogalacturonan I from industrial potato waste”
Authors: I. Byg, J. Diaz, L.H. Øgendal, J. Harholt, B. Jørgensen, et al