Modification of cassava starch by acetylation and pulsed electric field technology: Analysis of physical and functional properties

Abstract

A dual pulsed electric field (PEF)-acetylation method to modify cassava starch was optimized. Also, the independent effect of each method on the functional properties of the starch was investigated. A PEF pre-treatment of 40 J/g (9.48 kV/cm) increased the acetylation degree by 47%. The dually modified starches presented the highest water solubility index (39.3%), a decrease of gelatinization enthalpy (5.4 J/g d.b.) and temperature (60.8 °C), and a better tolerance to refrigerated storage. A reduction of ordered structures was evidenced by FTIR. The PEF-modified starch also showed changes in its rheological profile, increments of the hydration properties and decreased retrogradation in comparison to the native sample, suggesting the potential of this physical method to modify starches. This work studied for the first time the effect of dual modifications by PEF and acetylation performed sequentially and not simultaneously. The results showed that the proposed scheme was efficient to improve the acetylation process. Industrial relevance: Starch is widely used in the food industry to modify texture, water retention and film making properties of products. Yet, because native starches rarely meet all the specific requirements for certain applications, physical and chemical modifications are applied to improve their functional properties. Acetylation is one of the most common chemical modifications for food uses. However, the pursue to minimize costs and environmental impact has motivated the search for complementary treatments to reduce the use of reagents and processing times. In the present study, a novel PEF-assisted acetylation process is proposed in which applying the physical and chemical treatments independently showed to be efficient to improve the acetylation process. This work scheme could enable the use of a common PEF system to assist different starch chemical modifications, offering a more versatile alternative for its industrial implementation.