Grass pea ( Lathyrus sativus L.) is a leguminous plant, the green parts of which are already used for animal feed.
Because of its high nutritional value, the authors of the new study from the Agricultural University in Krakow, Poland, say the plant could become a new raw material for the food industry.
Indeed, some work has already been done on its use in frozen and canned foods, and its potential as an ingredient in bread production.
The main raw material for starch production is corn, and there is also growing interest in starch from wheat, which is a by-product with gluten.
However the team from Krakow noted that the search is on for renewable raw materials because of environmental issues.
(Crop harvests where seriously affected last year by inclement weather, and the emerging biofuels industry is causing competition for raw materials).
In addition, given the trend towards clean labels in the food industry, formulators are keen to discover alternatives to ingredients that have to be listed as additives on food labels, but which can be signalled as natural food components instead.
For this reason, they set out to compare the rheological properties of grass pea starch starches to those of corn and wheat starch, and its susceptibility to retrogradation.
Two varieties of grass pea are registered as growing in Poland: Derek, which has a small seed, and Krab, which has a medium seed.
The plant is also cultivated in Asia, Africa, and Southern Europe.
The team looked at their gelatinisation properties, pasting properties, flow and viscoelastic behaviour, and retrogradation.
They found that the temperatures required for phase transition on pasting for both grass pea starches were lower than those needed for corn, but higher than those needed for wheat.
Pasting temperature was seen to be significantly lower for the grass pea than for the cereals, and there was higher paste viscosity than for wheat starch.
"Grass pea starches exhibit much higher values of storage and loss moduli during heating of starch suspensions," the researchers also reported.
The rheological properties of grass pea starches were, therefore, seen to differ from those of other cereal starches, and the researchers said this may be due to the varied amounts of non-starch components, like proteins and lipids.
However they added that its special features "may be exploited in food technology as an alternative for use of chemically modified starch."
"Grass pea starch may be an alternative for chemically modified starches, and as a source of resistant starch, because of high amylose content and the resulting retrogradation susceptibility," wrote the researchers.
They noted, however, that while the Derek and Krab grass pea varieties had similar amylose contents to each other, they were actually less than the levels in Canadian varieties (although this may have been due to measurement methods).
The Polish varieties were also seen to have larger starch grain size (average diameter 34 micro m) than the Canadian variety (26.8 micro metres) - larger, too, than wheat and corn starch granules.
Source: Journal of Food Engineering (online ahead of print) DOI: 10.1016/j.jfoodeng.2008.03.018 "Grass pea (Lathyrus sativus L.) starch as an alternative for cereal starches.
Rheological properties and retrogradation susceptibility."
Authors: Jaroslaw Korus, Marius Witczack, Leslaw Juszczack, Rafal Ziobro