The Gloss of Edible Coatings as Affected by Surfactants, Lipids, Relative Humidity, and Time

Water‐based whey protein isolate (WPI) coatings had the same gloss as shellac and zein coatings cast from ethanol solutions and water‐based tapioca dextrin and hydroxypropyl methylcellulose (HPMC) coatings. For lipid dispersion coatings, the particle size of the dispersed phased influenced gloss values. WPI coatings had stable gloss values at 52%, 75%, and 95% relative humidity (RH). At 95% RH, shellac and zein coatings “blushed,” and both dextrin and HPMC coatings became tacky. WPI and shellac films maintained a high gloss after 7.6 mo of storage at 23 °C and 75% RH and had higher gloss than whey protein concentrate (WPC) and HPMC coatings. The type and level of surfactant added to WPI coatings greatly influenced gloss.