"More and more consumers leave many aspects of the preparation of daily meals to the food industry," wrote lead author William Willats from the University of Copenhagen. "This creates an increasing demand for functional ingredients with superior properties in the production of foodsand designer pectins are expected to play an important role in this future."
The ingredient, with worldwide production estimated at 35,000 tonnes a year, is currently widely used as gelling agents in jams, confectionary, and bakery fillings, and stabilisers in yoghurts and milk drinks.
The functionality of the pectin is dictated by the chemical fine structure, and the majority of the pectins used currently come from citrus peel and apple pomace. Other sources of the ingredient have remained largely unexploited because of certain undesirable structural properties.
But advances into the structure and functionality of pectins, said Willats and his co-authors Paul Knox from the University of Leeds and Dalgaard Mikkelsen from Danisco Biotechnology, could open the door to designer pectins from different sources with tailored functionalities.
"This can be achieved to some extent by the rational modification of extracted pectin by chemical or enzymatic treatment. A more ambitious goal is to modify pectin structure within plants before extraction," wrote the authors in the journal Trends in Food Science & Technology (Vol. 17, pp. 97-104).
The chemical and enzymatic modification of the pectins occurs after extraction from the plant, and the most industrially important pectinolytic enzymes coming from bacterial sources. This approach has enabled scientists to tailor the pectin according to the required functionality.
"This is illustrated by the recent development of specialised pectin for acidified milk drink stabilization," said the researchers. "A variety of pectins that had been digested with pectin methyl-esterases from plant, bacterial and fungal sources were tested with the aim for producing a pectin with the greatest stabilisation capacity at the lowest concentration. Lime pectin with long contiguous stretches of un-esterfied galacturonic acid residues was significantly more effective at preventing sediment than a range of other pectins."
Another area beginning to be explored is the transgenic approach which would allow scientists to manipulate the structure of the pectin in planta. By manipulating the expression of certain genes in specific plants, plant scientists should be able to control pectin functionalities and quality in the plants even before extraction begins, said the reviewers.
Moreover, progress has already been made with several studies reportedly showing that the activity of certain enzymes in the plants can be affected using an 'antisense' approach, while others have reported that it is possible to genetically modify the side chains of the pectins.
An example of study in this area in the European Framework V programme, EuroPectin, said Willats, which aimed to improve sugar beet pectin by manipulating genes.
"Sugar beet pulp is potentially an abundant and low cost source of pectin, but is rarely utilised because its high degree of acetylation adversely affects functionality. However, identification and characterisation of plant acetyl-transferases and esterases may in the future lead to production of pectin with improved functionality from transgenic sugar beet," they said.
The major non-technical challenge in this area however remains public concerns about food and ingredients from transgenic sources, especially in Europe and most notably in the UK.
Whether the future involves chemical and enzymatic approaches or the in planta GM approach, the recent advances could expand the source of pectins to a wider range of inexpensive, readily available and sustainable plants.
While predicting that better understanding of the pectins could lead to novel applications the authors could not predict where and how these applications may arise.
"Pectin producers now have the knowledge and technology to manipulate pectin at all stages of the production process and in the forthcoming years it is likely that pectin with new and improved functionalities will be produced," concluded the researchers.
"However, it will be important that these advances are carefully managed, and that pectin maintains its deserved reputation as a 'natural' product."