Pickering particles prepared from food waste

In this paper, we demonstrate the functionality and functionalisation of waste particles as an emulsifier for oil-in-water (o/w) and water-in-oil (w/o) emulsions. Ground coffee waste was chosen as a candidate waste material due to its naturally high content of lignin, a chemical component imparting emulsifying ability. The waste coffee particles readily stabilised o/w emulsions and following hydrothermal treatment adapted from the bioenergy field they also stabilised w/o emulsions. The hydrothermal treatment relocated the lignin component of the cell walls within the coffee particles onto the particle surface thereby increasing the surface hydrophobicity of the particles as demonstrated by an emulsion assay. Emulsion droplet sizes were comparable to those found in processed foods in the case of hydrophilic waste coffee particles stabilizing o/w emulsions. These emulsions were stable against coalescence for at least 12 weeks, flocculated but stable against coalescence in shear and stable to pasteurisation conditions (10 min at 80 °C). Emulsion droplet size was also insensitive to pH of the aqueous phase during preparation (pH 3–pH 9). Stable against coalescence, the water droplets in w/o emulsions prepared with hydrothermally treated waste coffee particles were considerably larger and microscopic examination showed evidence of arrested coalescence indicative of particle jamming at the surface of the emulsion droplets. Refinement of the hydrothermal treatment and broadening out to other lignin-rich plant or plant based food waste material are promising routes to bring closer the development of commercially relevant lignin based food Pickering particles applicable to emulsion based processed foods ranging from fat continuous spreads and fillings to salad dressings

Dynamic aroma release from complex food emulsions

In-vitro dynamic aroma release over oil-in-water (o/w) and water-in-oil-in-water (w/o/w) emulsions stabilised with Tween 20 or octenyl succinic anhydride (OSA) starch as a hydrophilic emulsifier and polyglycerol polyricinoleate (PGPR) as a hydrophobic emulsifier was investigated. The equal-molecular-weight hydrophilic aroma diacetyl (2,3-butanedione) or relatively-more-hydrophobic 3-pentanone was added to the emulsions prepared by high speed mixing, or membrane emulsification followed by thickened with xanthan gum removing droplet size distribution and creaming as variables affecting dynamic release. Results showed the differences of w/o/w emulsions in the dynamic release compared to o/w emulsions mainly depended on aroma hydrophobicity, emulsion type, emulsifier-aroma interactions and creaming. Xanthan led to a reduced headspace replenishment. Interfacially adsorbed OSA starch and xanthan-OSA starch interaction influenced diacetyl release over emulsions. OSA starch alone interacted with 3-pentanone. This study demonstrates the potential impact of emulsifying and thickening systems on aroma release systems and highlights that specific interactions may compromise product quality

In-vitro oral digestion of microfluidically produced monodispersed W/O/W food emulsions loaded with concentrated sucrose solution designed to enhance sweetness perception

Monodispersed W1/O/W2 emulsions consisting of sunflower oil droplets containing a single large internal droplet or numerous small internal droplets of concentrated sucrose solution were prepared by microfluidic emulsification. The external droplet interface was stabilized by waxy rice starch, which hydrolyzes during oral processing thereby releasing the encapsulated sucrose solution to the proximity of taste receptors imparting a higher sweetness perception compared to adding the same amount of sugar to the bulk phase. The sucrose release was tracked by adding NaCl to the internal phase as a conductivity tracer. Core/shell droplets containing 50 wt% sucrose and 1.5 wt% NaCl in the internal phase, 1.40–2.86 wt% polyglycerol polyricinoleate (PGPR) in the middle phase, and 4 wt% gelatinized waxy rice starch in the external phase were produced with 100% encapsulation efficiency and showed stability against coalescence for at least two months, because the gelatinized starch acted as a highly efficient Pickering stabilizer. The sucrose release from the inner droplets during in-vitro oral processing at 37 °C for 30 s with 50 U/mL α-amylase increased from 16% to 49% when the PGPR concentration in the oil phase was reduced from 2.86 wt% to 0.7 wt%. Core/shell droplets were less stable during storage when the surface-active molecularly dissolved octenyl succinic anhydride (OSA) modified starch was selected as stabilizer although the oil droplets were smaller due to the lower interfacial tension at the external interface. W1/O/W2 emulsion consisting of numerous internal droplets coalesced during storage in one day and released 91% of sucrose during in-vitro oral processing