[5-1130-P] Food Safety (5th)

[5-1130-P-20] Improvement of the Cleanability of Milk Soil on a Highly Smooth Surface of Stainless Steel Tubing

*Ikko Ihara¹, Homi Takato¹, John K Schueller², Gen Yoshida¹, Kazutaka Umetsu³, Hitomi Yamaguchi² (1. Kobe University(Japan), 2. University of Florida(United States of America), 3. Obihiro University of Agriculture and Veterinary Medicine(Japan))

Keywords:milk soil, surface roughness, cleanability

Stainless steel tubing is widely used for process equipment in milk processing industries. The presence of milk soils on internal surfaces of stainless steel tubing may cause deterioration in quality and food poisoning. Frequent cleaning of the equipment surface is needed to avoid contamination, however, it may cause an increase environmental impacts, linked to the consumption of water, detergent and energy. Surface roughness is one factor affecting the attachment and removal of food soils. EHEDG (European Hygienic Engineering & Design Group) recommends that large areas of food product contact surface should have a surface finish of 0.8 µm R_a. In this work, we studied cleanability of milk soil on a highly-smooth internal surface with 0.01 µm R_a of stainless tubing. The highly-smoothed stainless tube was prepared by magnetic abrasive finishing (MAF), which is an internal finishing process by the application of a magnetic field of permanent magnets. Three different levels of surface roughness of stainless steel tubings were tested to evaluate the cleanability of milk soil. On the deposition test, whole milk at 44°C was circulated in a tested loops connected with the tested stainless tubings. After the deposition process, deionized water at different temperatures was flushed into the tested loops to clean milk deposition on the internal surface of stainless steel tubings. To evaluate the cleanability of the milk deposition in the tubings, we measured amounts of milk residues and residual proteins on the internal surface of the tubings. The data showed that the smoother surface had a tendency to improve the cleanability of milk soil and milk protein at 45°C of cleaning solution. When the temperature is raised from 20 to 45°C, the cleanability of milk soil was improved. However, when the temperature was raised from 45 to 50°C, almost no change was observed. At 35, 45, and 50°C, smoothing of the surface showed a tendency to improve detachment of milk soil. The cleaning solution temperature affected the removal of milk soil. The relationship between surface roughness and detachment of milk soil was clearly observed, when the cleaning solution temperature was at 45°C.