Improved adhesion of edible protein coatings to nuts by modifying surface morphology of nuts and coating technique

Whey protein coatings on peanuts are not effective, due to incomplete peanut-surface coverage, as well as some cracking and flaking of the coating. In order for whey-protein-based oxygen-barrier coatings to be effective in reducing oxidative rancidity of peanuts, good surface coverage and durable coating adhesion are necessary. Addition of sorbitan laurate in the coating solution to a concentration of 0.15% substantially improved the coating coverage to 95% on peanut. These results suggest that a concentration of surfactant above the c.m.c in the coating solution is required for formation of self-assembled structures of surfactant molecules on peanut surfaces, which significantly increases the hydrophilicity and coatability of peanut surfaces.; Mechanical roughening of peanut surfaces also improved whey protein coating efficiency on peanuts. Improved coating coverage was more consistent on mechanically-roughened freshly-blanched-and-roasted peanuts compared to the commercially-blanched-and-roasted peanuts, mainly due to the mechanically-roughened freshly-blanched-and-roasted peanuts was coated and accessed without change of peanut surface during the refrigeration before coating. The improved coating coverage on mechanically-roughened freshly-blanched-and-roasted peanuts may be the result of avoiding the re-formation of a waxy cuticle layer on peanut surfaces that occurs during storage.; Complete peanut surface coverage and strong adhesion are necessary for coatings to be effective in reducing oxidative rancidity of peanuts. Surfactant addition to the coating solution and mechanical roughening of peanuts were found to improve whey protein coating efficiency on peanuts coated with a bench-scale fluidized-bed coating system. Peanuts coated with the fluidized-bed coating system attained nearly complete coverage, and results were consistent and reproducible.; When fluidized-bed coating system was applied for peanut coating, a lower level of surfactant in the coating solution was required to attain complete coverage, compared to dip-coating and pan-coating of peanuts. Addition of surfactant to the coating solution was required for imparting good peanut coating durability. Fluidized-bed coating required a greater amount of coating solution applied compared to pan coating, due to the loss of coating solution to the fluidized-bed column wall. Fluidized-bed coating required a shorter processing time and provided better coating efficiency and durability, suggesting the fluidized-bed coating system is a viable alternative coating process for coating peanuts.