Writing in the journal LWT - Food Science and Technology, the researchers report that, while the spray-drying technique reduced the beta-carotene and vitamin C content of the tuber, the rheology (flow characteristics) were similar to pre-gelatinized starch solutions.
"Thus, spray dried sweet potato powders have a potential to enhance food systems as a thickener despite the need for increased nutrient retention," they wrote.
Thickeners, along with emulsion stabilisers, suspending agents, gelling agents, thickeners, fibre sources, mouthfeel improvers, fat replacers and processing aids all come under the umbrella of hydrocolloids. This market has grown signficantly in the past 20 years in parallel 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), Methyl Cellulose and hydroxypropyl Methyl Cellulose (MC/HPMC), microcrystalline cellulose (MCC), pectin, starch and Xanthan.
A potential new member of this team, if further research backs up the promising early studies, could be sweet potato powder, said the USDA researchers.
"Sweet potatoes are highly nutritious vegetables; however, sweet potato consumption is progressively declining especially in industrialized nations," they said. "One way to expand sweet potato consumption is to develop appealing processed products or alternative uses for sweet potato roots."
The researchers enhanced the spray drying of sweet potato puree using alpha-amylase treatment to reduce puree viscosity, and maltodextrin to facilitate drying.
J.A. Grabowski and co-workers report that spray drying - one of the most common techniques used in the food industry due to its low cost and ease of application - significantly reduced the beta-carotene and ascorbic acid contents.
When the researchers prepared slurries and compared them to solutions containing pregelatinized starch they found similar behavioural attributes.
"Sweet potato powders in solution behaved similarly to pre-gelatinized starch solutions but required higher concentrations for the same effects," said the researchers.
"Sweet potato powder may have the potential to act as a functional ingredient for enhancing natural colour and flavour and acting as a thickening ingredient like pre-gelatinized starches in food systems," they concluded.
Source: LWT - Food Science and Technology
Published on-line ahead of print, doi: 10.1016/j.lwt.2007.02.019
"Nutritional and rheological characterization of spray dried sweet potato powder"
Authors: J.A. Grabowski, V.-D. Truong and C.R. Daubert