engleski

In vitro digestibility of ultrasonically treated starch

Starches from two different botanical origin (wheat and potato) before and after sonication (ultrasound probe of 24 kHz frequency, nominal power of 400 W and propagation time of 15 minutes) were assessed for digestion in vitro. Their starch fractions were characterized as rapidly digestible starch (RDS), slowly digestible starch (SDS) and resistant starch (RS). Rheological parameters, pasting properties and particle size have been also determined. Previous studies have indicated that the granule size distribution and shape are considered important for the functional properties of the starch. Size of the starch granule also may affect digestibility within the meaning of relationship between surface area and starch volume. Our results have shown that ultrasound processing, as technique already commonly applied for food processing, (e.g. extraction, drying, homogenization) can induce changes in the physical properties (particle size, viscosity, pasting properties) of starches to obtain ingredients with improved physicochemical properties and the reactivity for tailor made foods. Rheological parameters showed that all suspensions exhibited non- newtonian (dilatant) character and increase of consistency coefficient of starch suspensions. Sonicated starches showed reduction in gelatinization temperatures. Such effects are caused due to the physical effects of high intensity ultrasound that relies on cavitation phenomenon.The interparticle collisions that arise during sonication are capable to foster striking changes in surface morphology, composition and reactivity. Starch with smaller granules (wheat) showed greater starch digestibility before sonication than starch with larger granules (potato). After sonication, increase in RDS and RS content was observed. This could be explained as a consequence of granule changes in surface morphology and aggregates formation induced by sonication.

In vitro digestibility; starch; sonication

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