Monday, August 12, 2013
Pavilion (Sheraton San Diego)
NSF International conducted a study to develop an alternate cleanability assay using ATP based systems for the certification of dishwasher performance. Two commercial ATP based systems (A and B) were used in the study. Ketchup, Ketchup+ E. coli and 7% Bovine Serum Albumin (BSA) were used as soiling agents. Soiling agents (1 mL) were uniformly applied on individual stainless steel and plastic coupons (surface types) and dried for about an hour before washing them in a commercial dishwasher. Reductions (%) of RLU were calculated against control coupons to determine the efficacy of the wash cycle on different surface types. A two-way ANOVA was conducted to test if there were any significant difference between surface types and soiling agents using system A. A one-way ANOVA was conducted to compare the two surface types for system B. The consistency/repeatability of the data of ATP systems was evaluated based on CV %. Greater than 99% reduction in RLU was observed for both surface types soiled with different soiling agents indicating that washing cycle was equally effective against all treatments, further confirmed by the results of two-way ANOVA (types of surfaces, P>0.28 and soiling agents, P>0.20). Similarly in system B, no significant differences in RLU was observed between the two surface types (P>0.06). System B was more consistent (CV=48.15%) than system A (CV=95.59%). Based on these observations, ATP based assay is not suitable for such applications because selection of suitable non-interfering soiling agent is critical and high variability of data produce unreliable acceptance criteria.