Amino acids may extend sweet potato starch's gelling possibilities

Tag : methyl cellulose(mc)
The nature of the amino acid was found to strongly influence theresulting properties of the amino acid, and perhaps allowing fortailored starches for different food applications, suggests theresearch in the Journal of Food Science .

Both lysine, a positively-charged amino acid, and lysine, asparticacid, a negatively charged amino acid, decreased the viscosity ofstarch paste made from orange-fleshed sweet potatoes

"The decrease in pasting viscosity shows that this starch wasmodified into a thinner pasting starch. The decrease of both thepasting time and the minimum viscosity for this starch couldtranslate into a faster cooking time and a product that is easierto cook," wrote the researchers from Louisiana State University.

The research appears to support the growing potential of sweet potato starch for use in various food applications as a thickener, an emulsionstabiliser, suspending agent, gelling agent, fibre source,mouthfeel improver, and fat replacer - all of which come under theumbrella of hydrocolloids . This market has grown significantly in the past 20 years inparallel to an increasingly complex food processing industry.

The food industry's most frequently used hydrocolloids include:agar, alginates, arabic, carrageenan, Carboxy Methyl Cellulose(CMC), gelatin, konjac flour, locust bean gum (LBG), MethylCellulose and hydroxypropyl Methyl Cellulose (MC/HPMC),microcrystalline cellulose (MCC), pectin, starch and Xanthan.

A potential new member of this team, if further research backs upthe promising early studies, could be sweet potato powder, suggestthe Louisiana State researchers.

Joan King and co-workers studied the effects of charged (asparticacid and lysine) and neutral (leucine and methionine) amino acidson the pasting and thermal characteristics of Beauregard sweetpotato starches

They report that starch from the orange-fleshed variety was easierto cook, had a lower potential for retrogradation, but was lessstable during heating than starches from the white-fleshed variety.

Moreover, this decrease in retrogradation was enhanced by asparticacid.

"This decrease in the retrogradation of the starch upon cooling maymake the starch more suitable for use in some products, such as bakery goods, that could be negatively affected by staling," they said.

Increasing the stability of the starch during cooking was achievedby lysine, as evidenced by a decrease in the breakdown value of theorange-fleshed sweet potato starch.

The neutral amino acids were found to have no significant effectson the characteristics of the starch, compared to control.

"This study showed that pasting properties of sweet potato starchescan be altered by the addition of amino acids," they concluded.

Cheap sourcing of a value-adding ingredient?

The researchers also indicate that cost may not be too much of alimiting factor for applying the starches to food.

"Approximately 600,000 tons of sweet potatoes are produced annuallyin the United States ," said the researchers. "Up to 33 per cent of the raw potato brought into processingfacilities can end up as waste… At present, there is notmuch use for this waste and it must be discarded, but much of thiswaste could be used to produce sweet potato starch in a verycost-effective manner and would also eliminate the unnecessarywaste of so many sweet potato pieces."

Clean label drivers

The market for potato starch is growing. According to Marketmanager Paul Sheldrake from Dutch potato co-operative Avebe, one ofthe key benefits is that the potato starch-derived ingredient canbe labelled as 'starch' rather than 'modified starch', meetingclean label requirements that are being put in place bymanufacturers and retailers.

This, he told FoodNavigator.com recently, is an important consumerdriver, as there is a general shift away from food additives andingredients that are seen to be of artificial origin.

Source: Journal of Food Science
Published online ahead of print, 13 May 2008, doi:10.1111/j.1750-3841.2008.00755.x
"Altering Pasting Characteristics of Sweet Potato Starches throughAmino Acid Additives"
Authors: S. Lockwood, J.M. King, D.R. Labonte