Malanga starch modified by annealing: Partial characterization and application as wall material in the protection of hibiscus extract

Abstract

The hibiscus extract was encapsulated in thermally modified malanga starch (annealing) with the objective of enhancing the protective capacity of the bioactive compounds. Annealing malanga starch was conducted in a 1:9 ratio (starch/water) at temperatures of 67 °C and 70 °C for a period of 48 h. The bioactive compounds and antioxidant activity of the hibiscus extracts were quantified. The physicochemical characterization of native malanga starch (NMS) and starches modified by annealing at 67 °C (SA-67) and 70 °C (SA-70) showed amylose increased by 11.86 %, 13.20 %, and 13.06 %, respectively. The peak temperature (Tp) showed values of 77.76 °C for NMS, 82.57 °C for SA-67, and 83.86 °C for SA-70. As the temperature modification increased, the values of humidity, water activity, and gelatinization enthalpy decreased in the starches. The modifications made by NMS annealing showed that the microcapsules obtained favored the total retention of anthocyanins, with values ranging from 37.93 % (NMS encapsulates) to 54.37 % (SA-70 microcapsules). SA-70 encapsulates exhibited better protective capacity for bioactive compounds than SA-67 ones across an 8-week storage period. Scanning electron microscopy revealed that the modification at 70 °C changes the shape of the starch granule, promoting changes on the surface structure of SA-67 and SA-70 encapsulates compared to NMS encapsulates. These physicochemical changes due to modification by annealing could influence NMS ability to retain anthocyanins when used as a wall material and the stability of microencapsulated bioactive compounds during storage.