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

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 T 2b relaxation time and increase in A 21 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.