Effect of soaking and autoclaving treatments on structure, properties and resistant starch (RS3) content of edible tapioca pearls

In the present study, the effect of different soaking and autoclaving treatments on structure, properties and resistant starch (RS3) content of edible tapioca pearls were investigated. Before and after treatments, the structural changes in the tapioca samples were observed using Fourier transform infrared (FT-IR), near infrared (NIR) and Raman spectroscopy, and pasting properties were investigated with the help of rapid visco analyser (RVA). The results showed that all soaking and autoclaving treatments increased RS3 content of the tapioca pearls. Autoclaving treatments showed highest increase in the RS3 content of tapioca pearls than soaking treatments. Findings of FT-IR studies showed that elevated RS3 content of tapioca pearls after soaking and autoclaving treatments may be due to decrease in intra and intermolecular hydrogen bonds, and/or increase in the crystallinity of tapioca pearls starch. In addition, FT-IR investigations confirmed that bands at 2928 and 2856 cm-¹ were characteristically sensitive to soaking and autoclaving treatments. Results of NIR spectral analysis demonstrated that soaking and autoclaving treatments may increases structural changes in the skeletal mode of tapioca starch. Raman spectroscopic studies further confirmed that increase in the RS3 content of tapioca pearls samples after soaking treatments might be due to the increase in amylose content. In addition, Raman spectroscopic studies further highlighted that the autoclaving treatments brought complete structural modification in the tapioca starch. Pasting properties of untreated tapioca pearls samples were found to decline with treatments. Studied Tapioca pearls sample lost almost all pasting property parameters after autoclaving treatments. In conclusion, autoclaving treatments were good to increase RS3 content of tapioca pearls than soaking treatment, but they had adverse impact on pasting property and structural integrity of tapioca pearls starch. On contrary to this, soaking treatments preserve pasting property parameters as well as moderately increased the RS3 content of tapioca pearls.