Abstract
Abstract The calcium oxalate content from two Amazonian amilaceous roots, Xanthosoma sagittifolium and Pachyrhizus tuberosus, before and after cooking were studied in the present work. Calcium oxalate raphides were observed by light microscopy in longitudinal sections from fresh tubers. The functional properties and physicochemical characteristics of isolated starches from both species were also investigated. Starches granules were observed with scanning electronic microscopy and presented a typical oval-circular shape, smooth surfaces and size ranging from 3.6 μm to 14 μm. Lower gel clarity, slightly high water-binding capacity, A-type starch structure and low values of crystallinity degree were determined in the isolated starches. High intensity bands related to vibrations of glucosidic bonds of polysaccharides were observed by infrared spectroscopy in both starches. Thermal degradation behavior data of the isolated starches reveled high initial decomposition temperatures. Thus, the studied cooked tubers presented low levels of calcium oxalates and are safe to be consumed as a boiled vegetable. Their isolated starches possess good functional characteristics to be applied as an ingredient to products in food industry.
Highlights
Cocoyam, taro, aerial yams and other tuberous roots are nutritive and relevant crops to several tropical countries in South America, Africa, Asia and Oceania (Londoño-Restrepo et al, 2018; Otegbayo et al, 2014)
A significant reduction of more than 85% in calcium oxalate content was found for both species after cooking
The isolated starches presented lower gel clarity and a slightly high water-binding capacity, which may be related to the internal arrangement and morphology of the starch granules
Summary
Taro, aerial yams and other tuberous roots are nutritive and relevant crops to several tropical countries in South America, Africa, Asia and Oceania (Londoño-Restrepo et al, 2018; Otegbayo et al, 2014). Researches about starch sources from untraditional tuberous roots has raised due to their functional properties and to the intense demand of carbohydrates in food and pharmaceutical industries (Londoño-Restrepo et al, 2014; Odeku, 2013). Starch properties, such as, shape and granules size, as well as its crystallinity pattern, water binding capacity and thermodegradation behavior, are important factors to be considered when applied into products (Jayakody et al, 2007)
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