Milk contact surfaces were observed by scanning electron microscopy (SEM) techniques for possible microbial attachment. Cultures of Pseudomonas fragi 4973, Staphylococcus aureus JAL, Streptococcus lactis C2, Streptococcus cremoris and Lactobacillus bulgaricus RR inoculated onto glass coverslips or stainless steel chips were examined. Stainless steel surfaces displayed many possible harborages for microbial colonization. SEM examination of P. fragi 4973 showed development of fibrous material, with numerous stick-like projections extending from the cell to the glass or stainless steel surface. These apparent attachment appendages became more pronounced as contact time increased. S. aureus, S. lactis, S. cremoris and L. bulgaricus did not display such fibrous material.
1Paper No. 11,299, Scientific Journal Series, Minnesota Agricultural Experiment Station, St. Paul, Minnesota 55108