Contribution of okra extracts to the stability and rheology of oil-in-water emulsions

Three okra polysaccharide extracts were isolated and studied in terms of their composition and their capacity to affect the rheology and stability of emulsions. HBSS (hot buffer soluble solids, extracted at 70 °C, pH = 5.2) comprised of charged (zeta potential −21.5 mV) polysaccharides sizing between 5 kDa (d ∼ 3 nm) and 50 kDa (d ∼ 200 nm), and a population of very large molecules (MW >> 1.4 MDa). Upon addition in Tween 20-stabilized emulsions, HBSS caused flocculation and enhanced creaming at low concentrations (0.125%), while at higher concentrations (1.25%–2.50%) it drastically reduced creaming due to its increase of the continuous phase viscosity. CHSS (chelating agent soluble solids, extracted at 70 °C, pH = 5.2) comprised of distinct polysaccharide populations between 12 kDa (d ˜ 10 nm) and 70 kDa (d ∼ 80 nm), with a negative zeta potential (−14.3 mV) and a high (31%) protein content. Upon addition in Tween 20-stabilized emulsions, CHSS induced flocculation, shear-thinning rheology, and rapid creaming at concentrations above 0.5%. DASS (diluted alkali soluble solids, extracted at 0 °C) comprised of polymers 12 kDa (d ˜ 20 nm) and 70 kDa (d ∼ 130 nm), and had a low zeta potential (−6.2 mV). Adding small amounts (0.25%) of DASS in emulsions induced flocculation, development of shear-thinning rheology and fast creaming. At higher DASS concentrations (above 1.65%), viscosity increase of the aqueous phase delayed creaming.