Pickering emulsions immobilized within hydrogel matrix with enhanced resistance against harsh processing conditions and sequential digestion

Abstract

Protein particles stabilized Pickering emulsions are unstable under harsh 15 processing conditions and vulnerable to premature lipid phase release during gastric digestion. 16The objective of this study is to encapsulate kafirin nanoparticles-stabilized Pickering emulsions 17 (KPE) within hydrogel matrix to develop orally administrated Pickering emulsions with 18 enhanced storage and sequential release properties. By premixing KPE and sodium alginate with 19 different volume ratios, emulsion hydrogels (EGs) with various emulsion fractions were 20 immobilized within the calcium ions crosslinked sodium alginate hydrogel matrix thereafter. 21Ultra small-angle x-ray scattering (USAXS)/ small-angle x-ray scattering (SAXS) analyses 22 suggested that encapsulation of KPE resulted in shrinkage in hydrogel network mesh size, and 23 the emulsion interface evolved from smooth to course one as volume ratio of sodium alginate to 24 KPE increased. When incubated under alkaline (i.e., pH=8.5) or high-temperature (i.e., 60 ℃) 25 conditions which were previously reported to cause severe structural collapse for KPE, the 26 coalescence and lipid phase release in EGs were largely inhibited. EGs were also found to be less 27 subjective to stimulated gastric digestion, while the collapse of EGs and thus the release of lipid 28 phase took place in simulated intestinal fluid. The volume fraction of alginate in EGs did not 29 affect the ultimate free fatty acid (FFA) release extent, but it had a negative correlation with the 30 bioaccessiblity of lipophilic nutraceutical. This study highlights the potential of designing 31 hydrogel carrier for the oral administration of Pickering emulsion with ease of preparation, 32 improved processing stability and controlled digestion profile. 33 KEYWORDS: Pickering emulsion; emulsion hydrogel; microstructure; stability; digestion 34 profile 35 3

Improved stability of (W1/O/W2) double emulsions based on dual gelation: Oleogels and hydrogels

“…This reason could also be used to explain why the oil globules encapsulated in Ca‐alginate hydrogel beads had better stability than the oil globules in the alginate‐double emulsion system. This result was in agreement with the previous study, which has reported that the coalescence of Pickering emulsions was largely inhibited through the encapsulation of Pickering emulsions in hydrogels (Xiao et al, ). It could be found that the retention efficiency exhibited a slightly decreasing trend with the increase of the alginate concentration.…”

“…This reason could also be used to explain why the oil globules encapsulated in Ca-alginate hydrogel beads had better stability than the oil globules in the alginate-double emulsion system. This result was in agreement with the previous study, which has reported that the coalescence of Pickering emulsions was largely inhibited through the encapsulation of Pickering emulsions in hydrogels (Xiao et al, 2017 For the double emulsions prepared using 0, 5, and 10% GMS, the oil globules on the edge of beads could be clearly observed, which were released from the beads with the external force. For the double emulsions prepared with 15% GMS, the absence of oil globules on the edge of the beads might occur due to the high rigidity of insoluble GMS crystals, which might fill in the openings between alginate chains and hinder the release.…”

“…At least 90 droplets were measured for the calculation. To assess the mean size and size distribution, volume averaged mean diameter ( D 43 ) and Span were calculated, according to previous researches, by the following equations: where, n is the total number of the measured droplets, d i is the diameter of each droplet, d10, d50, and d90 are the respective diameter below which 10, 50, and 90% of all measured droplets (van der Ark et al, ; Xiao et al, ).…”

“…It has been reported that the immobilization of (O/W) single emulsions within Ca-alginate hydrogels through the crosslinking process could prevent the coalescence of oil globules and improve the stability of emulsions (Chan, 2011;Xiao, Shi, Li, Pan, & Huang, 2017). Alginate, an edible natural polysaccharide isolated from brown seaweed, is a linear polymer made up of α-1,4-l-guluronic acid residues and β-1,4-d-mannuronic acid residues (Ching, Bansal, & Bhandari, 2017).…”

“…ter of each droplet, d10, d50, and d90 are the respective diameter below which 10, 50, and 90% of all measured droplets(van der Ark et al, 2017;Xiao et al, 2017). China) at 500 rpm for 24 hr, forming the stock solutions with different sodium alginate concentrations (varying from 0.5 to 3%, wt/vol).…”