Effects of Sulfur-Containing Amino Acids and High Hydrostatic Pressure on Structure and Gelation Properties of Sweet Potato Protein

Abstract

The structural modification and gelation properties of sweet potato protein (SPP) affected by sulfur-containing amino acids (L-cysteine or L-cystine) and high hydrostatic pressure (HHP) were investigated. Additives altered the denaturation temperature and reduced the denaturation enthalpy of SPP. Higher α-helical contents were observed in untreated or HHP-treated SPP with L-cysteine or L-cystine, while β-sheet and random coil structure unit were decreased. FTIR spectra showed a weak absorbance in HHP-treated SPP with L-cysteine and L-cystine. Storage modulus (G′) of untreated or HHP-treated SPP was enhanced by L-cysteine and L-cystine. Textural properties of SPP gels were improved by sulfur-containing amino acids and HHP, especially for L-cysteine. Decrease in T2b relaxation time and increase in A21 proportion peak area by low-field NMR suggested that water bound more closely to SPP molecules in the presence of L-cysteine and L-cystine, and more immobilized water fraction was trapped in SPP gel matrix.