Enzymatic modification of starches to improve their technological and functional properties

Abstract

In the last decade, porous polymers have attracted the attention of the food and non-food industries owing their great absorption capacity, which is dependent on the number and sizes of the pores. In this type of materials have been incorporated diverse polymers like starches after being subjected to physical, chemical or enzymatical treatments. The latter are considered the most promising due to the resulting materials are clean label polymers. However, up to now, the reported studies do not allow controlling the starch porosity. The objective of this doctoral thesis was the integral study of the production of porous starches by enzymatic treatment in order to modulate their structural and technological properties. With that purpose, native starches from different origin (corn, wheat, rice, potato and cassava) and diverse amylases (amyloglucosidase, alpha amylase, cyclodextrin-glycosyltransferase, branching enzyme) were used for producing porous starches, which were then characterized according to their structural and technological properties, as well as their in vitro digestibility. In addition, their viability as probiotic carriers was evaluated. The surface analysis of the starch granules, carried out by scanning electronic microscopy (SEM) indicated that the porosity of the starches could be modulated by either using enzymes with different hydrolytic activity, changing of enzymatic levels, or employing starches from diverse botanical origin. The amyloglucosidase led to porous starches with bigger pore sizes, and those were deeper in the case of cereal starches. Moreover, the control of starch porosity allowed changing the functionality of the starches, significantly affecting the water and oil holding capacities, the pasting and thermal properties and even their behavior during in vitro digestibility. Porous starches obtained from corn or rice after treated with alpha amylase were tested as probiotic carriers, yielding an increase of the thermal stability of Lactobacillus plantarum, especially after being coated with gelatinized starch. Additionally, the study carried out with the porous starches after being subjected to gelatinization opens new opportunities to obtain hydrogels with diverse structural and functional properties.