Complex Coacervation and Overcharging during Interaction between Hydrophobic Zein and Hydrophilic Laponite in Aqueous Ethanol Solution.

In this paper, for the first time, we have reported the formation of complex coacervate during interaction between hydrophobic protein, zein, and hydrophilic nanoclay, Laponite, in a 60% v/v ethanol solution at pH 4. Dynamic light scattering and viscosity measurements revealed the formation of zein-Laponite complexes during the interaction between zein at fixed concentration, C Z = 1 mg/mL, and varying concentrations of Laponite, C L (7.8 × 10-4 - 0.25% w/v). Further investigation of the zein-Laponite complexes using turbidity and zeta potential data showed that these complexes could be demarcated in three different regions: Region I, below the charge neutralization region (C Z = 1 mg/mL, C L ≤ 0.00625% w/v) where soluble complexes was formed during interaction between oppositely charged zein and Laponite; Region II, the charge neutralization region (C Z = 1 mg/mL, 0.00625 < C L ≤ 0.05% w/v) where zein-Laponite complexes form neutral coacervates; and Region III, the interesting overcharged coacervates region (C Z = 1 mg/mL, C L > 0.05% w/v). Investigation of coacervates using a fluorescence imaging technique showed that the size of neutral coacervates in region II was large (mean size = 1223.7 nm) owing to aggregation as compared to the small size of coacervates (mean size = 464.7 nm) in region III owing to repulsion between overcharged coacervates. Differential scanning calorimeter, DSC, revealed the presence of an ample amount of bound water in region III. The presence of bound water was evident from the presence of an additional peak at 107 °C in region III apart from normal enthalpy of evaporation of water from coacervates.

Influence of alkali treatment on physicochemical, pasting, morphological and structural properties of mango kernel starches derived from Indian cultivars.

Present investigation was aimed to characterize the influence of alkali treatment on physicochemical, pasting, morphological and structural properties of mango kernel starches from three cultivars viz. Safeda, Chausa, Dussheri when treated with 0.1, 0.25 and 0.5% NaOH for 0, 5 and 10 days at 25 °C. Alkali treated starches have shown significant reduction (p < 0.05) in water binding capacity and amylose content whereas significant increase was observed in solubility and swelling power when compared with their native counterparts. Pasting properties of modified starches have shown significant changes from their respective native ones with highest reduction observed in Dussheri. Morphology was slightly affected by alkali treatment reflected as dents and grooves on the surface of starch granules. X-ray diffraction patterns were typically A-type, similar to native starches with decrease in crystallinities. IR spectra remained unaffected even after prolonged treatment. Thus, the time duration and concentration of alkali had played critical role in changing the physicochemical, pasting and morphological properties of mango kernel starches that could be potentially utilized for application in innovative products to enhance their textural and sensory attributes.