The purpose of this study was to compare the performance of the Detex RESI-CLEAN swab test to two other hygiene monitoring products intended for similar use including the Celsis snapshot ATP bioluminescence test and the Biotrace® Protect™ protein detection test. Hygiene monitoring tests are used to determine the general cleanliness of a surface. A surface with food residues supports microbial growth including food pathogens.
Principles of the RESI-CLEAN Test:
Pre-wetted swabs detect glucose and lactose, which are present in a wide range of food residues. These substances, when mixed with a buffer solution containing a color indicator will activate specific lyophilized enzymes. This activity generates an enzymatic reaction resulting in the solution forming a visible green color. The darker the green color, the more food residues (glucose and lactose) that are present on the sampling surface.
The food matrices that were tested included 14 foods typically encountered in fast-food restaurants: cooked ground beef, cooked poultry, lettuce, tomato, pickle, sandwich bun, cooked egg, milkshake, pie, salad dressing, ketchup, french fries, non-diet soda, ham and Canadian bacon. Triplicate samples of each matrix (10 g each) were stomached with 90 mL of deionized water for 2 minutes. This is a 10x dilution. Ten-fold serial dilutions were then prepared in deionized water, the last dilution being 100,000x. A stainless steel surface was thoroughly cleaned and 10 x 10 cm area delineated. For each sample, 0.1 mL of solution was evenly spread on a delineated 100-cm2 area and allowed to dry. Areas were swabbed according to each test manufacturer’s instructions and the results interpreted.
When testing dried surfaces, the Detex RESI-CLEAN swab test was superior or equivalent to ATP and protein tests for cola, bun, cooked egg, ketchup, french fries, apple pie, salad dressing and milk shake. ATP was preferable for lettuce, cooked beef, grilled chicken, pickles and tomato. The only foods not detected by Detex RESI-CLEAN were the cooked meats and pickles. The protein test was insensitive towards all foods tested on surfaces except bun and milk shake (all others were either precautionary or not detected). The ATP test did not detect cola, cooked egg, Canadian bacon or salad dressing. Further testing with raw beef and lemon demonstrated that Detex RESI-CLEAN could detect these food matrices.