Effects of ethanol washing on off-flavours removal and protein functionalities of pea protein concentrate
Jia Xin Tan, Chek-Chuan Tan, Jorry Dharmawan, Susanna Su Jan Leong
Abstract
The potential of ethanol washing at concentrations ranging from 15% (v/v) to 75% (v/v) in removing off-flavours in pea protein concentrate (PPC) and its effects on protein functionalities were investigated. Increasing concentrations of ethanol enhanced the removal of 1-hexanol. Higher ethanol concentrations, i.e., 50% (v/v) and 75% (v/v) effectively removed other volatile compounds contributing to off-flavours such as 1-octanol, 3-hexen-1-ol, 1-nonanol and trans-2-hexenal. Differential scanning calorimetry and protein solubility studies showed that higher ethanol concentration induced more protein denaturation as evidenced by the lower enthalpy change and protein solubility of the treated samples, where insoluble protein aggregates formed were hypothesized to be linked by hydrogen bonding. Ethanol treatment of PPC also increased its water holding capacity and reduced oil holding capacity. Ethanol concentration deployed significantly influenced gelling behaviour, where at lower concentrations of ethanol used for washing, i.e., 15 and 25% (v/v), the PPC gel strength increased compared to untreated samples. However, washing PPC at higher ethanol concentrations, i.e., 50 and 75% (v/v), reduced the PPC gel strength, where the higher extent of insoluble aggregates induced by higher ethanol concentration could weaken the gel network. In conclusion, PPC treated with high ethanol concentrations reduced majority of volatile compounds contributing to off-flavour, but significant protein structural changes which could influence product development performance were also observed.