The physicochemical properties of fruit powders and their residence time on stainless steel surfaces are associated with their ease of removal by brushing

Abstract

Dry cleaning activities such as brushing, scraping, and vacuuming have been widely used in low-moisture food production. However, the impact that product compositional differences and time between cleaning cycles have on the ease of food particulate removal is unclear. In our study, fruit powders were deposited on stainless-steel coupons, then removed using a hygienic brush. The residence time was defined as the duration between fruit powder deposition and attempted removal. Longer residence time resulted in elevated water activity (aw), which decreased the degree of removal for most fruit powders other than pumpkin powder and apple powder (sieve size: 2.36 mm). For instance, the aw of peach powder increased from 0.59 ± 0.01 on day 1 to 0.64 ± 0.01 on day 7, and residual powder after cleaning increased from 86.12 ± 1.73% to 93.26 ± 2.12% from day 1 to day 7. Peach powder and apple/pear/plum powder were the most difficult to remove, with average residual powder of 92.79 ± 4.97% and 58.41 ± 11.41%, respectively. Fruit powders that were more difficult to remove also exhibited higher cohesion and adhesion. For example, the cohesion and adhesion of peach powder at 76% relative humidity for 3 days were 4479.53 ± 681.86 N/m2 and 1347.53 ± 439.15 N/m2, respectively. By contrast, the cohesion and adhesion of pumpkin powder at 76% relative humidity for 3 days were only 102.34 ± 93.80 N/m2 and 90.64 ± 36.52 N/m2, respectively. These results suggested that aw could significantly influence the brush cleaning outcome in a manner that was dependent on the identity of the fruit powder.