Relative Cleanability of Various Stainless Steel Finishes after Soiling with Inoculated Milk Solids

Summary A semiautomatic spray-washing device, which provided controlled rinsing and washing without brushing, was used to determine the relative cleanability of Type 302 stainless steel panels having a No. 2B, 3, 4, and 7 finish after soiling with skimmilk inoculated with Bacillus globigii spores. Using the Direct Surface Agar Plate test at the 1 and 5% level, no significant difference was observed among these finishes after the test areas were rinsed (T-2), rinsed and washed with alkaline detergent (T-3), and rinsed, washed, and sanitized (T-4). This study indicates that the less highly polished finishes can be cleaned bacteriologically to the same degree as the highly polished No. 7 surface when the same cleaning cycle is used. No significant difference in bacterial cleanability was observed among finishes at the 5% level with the Standard Swab Contact Test after T-3 and after T-4. With the Direct Agar Contact Plate, a significant difference was observed among No. 2B, 3, 4, and 7 finishes after T-2, T-3, and T-4. The recovery of bacterial cells by this test was less than that obtained in the DSAP and Swab Contact Tests and indicates the unreliability of this test. In all trials, the bacteria counts decreased markedly as the washing procedure was changed from a minimum rinse to a complete cycle of rinse-wash and sanitize.