Inhibition of normal and waxy corn starch retrogradation by sodium borohydride

Abstract

After gelatinization, starch is prone to retrograde during storage, and it is a notorious challenge to inhibit starch retrogradation in papermaking, textile, and construction fields. This work aimed to develop a new method for inhibiting the retrogradation of normal corn starch (CS) and waxy corn starch (WCS) by sodium borohydride (NaBH4). Differential scanning calorimetry analysis suggested that addition of 2.0% (at dry starch basis, w/w) NaBH4 can completely inhibit WCS retrogradation. X-ray diffraction results showed that, as the NaBH4 concentration increased, the crystallinity of CS and WCS gradually decreased. After seven days of storage at 4 °C, the relative crystallinity of CS and WCS with 2.0% NaBH4 decreased by 62.22% and 100%, respectively. Low field nuclear magnetic resonance analysis showed that the incorporation of NaBH4 remarkably affected the change of relaxation time(T2). The T2 changes in the gelatinized CS and WCS with 2.0% NaBH4 were much lower than gelatinized CS and WCS without NaBH4. The addition of NaBH4 led to a reduction in the hydrogen bonding of CS and WCS, which was confirmed by Fourier transform infrared spectroscopy (FTIR). It was concluded that the addition of 2.0% NaBH4 can significantly inhibit the retrogradation of CS and WCS.