"The extracted pectin has the potential for utilisation in the food industry as a binder and stabiliser in jams, jellies, beverages and fruit juices," wrote the researchers, from Kagoshima University and University of the Ryukyus.
The research, published in the journal Food Chemistry, taps into the growing trend for alternative and novel sources of pectin, highlighted by an increasing number of studies looking at extracting pectin from sources such as sugar beet, pumpkin and squash.
The functionality of pectin is dictated by the chemical fine structure, and the majority of the pectin used currently comes from citrus peel and apple pomace. Other sources of the ingredient have remained largely unexploited because of certain undesirable structural properties.
Lead author Yukihiro Tamaki reports that the fruit is regarded as a significant agricultural product in Okinawa, Japan, and expects C. depressa to be effectively utilised and exploited in the future.
One such use of the fruit could be as a pectin source, said the researchers, reporting a yield of 4.1 per cent from the endocarp (the hard inner layer surrounding the seeds inside the fruit). This yield was slightly higher than recorded yields of lemon (between three and four per cent) and grapefruit (3.3 to 4.5 per cent), they said.
Chemical analysis showed that galacturonic acid accounted for 89 per cent of the total sugar content of the pectin, while sugars such as xylose and glucose, which are often present in pectin from citrus sources, were not detected by the researchers.
Further analysis showed that the degree of methoxylation (DM) was 66.2 per cent, making the pectin a high methoxyl pectin and therefore suitable for use in jellies, jams, and confectionery uses.
The use of the pectin as a potential gelling agent was confirmed by adding sucrose (60 per cent) and citric acid to a solution of the pectin.
"The results were consistent with the physicochemical properties of commercial pectins (galacturonic acid less than 65 per cent, degree of methoxylation 30 to 75 per cent, degree of acetylation less than 5 per cent, neutral sugars less than 15 per cent, and molecular mass between 100,000 to 200,000), as reported in the literature," wrote the authors.
"More research is needed on extracted pectin from C. depressa for effective utilisation in the food, physiological and pharmaceutical industries," they concluded.
Researchers from Denmark and England recently highlighted the possibilities of this ingredient and proposed that 'designer' pectin will become increasingly common in the future (Trends in Food Science & Technology, Vol. 17, pp. 97-104).
The ingredient, with worldwide production estimated at 35,000 tonnes a year, is currently widely used as gelling agents in jams, confectionery, and bakery fillings, and stabilisers in yoghurts and milk drinks.
Source: Food Chemistry (Elsevier)
Published online ahead of print, 17 August 2007, doi: 10.1016/j.foodchem.2007.08.027
"Isolation and structural characterisation of pectin from endocarp of Citrus depressa"
Authors: Y. Tamaki, T. Konishi, M. Fukuta and M. Tako