Testing the corrosion resistance of stainless steels during the fermentation of probiotic drink

BACKGROUND: Over recent years, food producers have devoted much attention to the production of safe foods. Simultaneously, using advanced process technologies, it has been necessary to carefully select materials for use in process equipment. Milk and its products are exposed to metal surfaces from the time they are processed, through the various stages of handling and manufacture, to the packaging of the finished products for market. The selection of suitable materials for daily use in the dairy industry cannot be governed solely by their price and mechanical properties but must also take into consideration their influence on the quality of milk products. RESULTS: This paper presents the results of testing the corrosion resistance of three stainless steels during the fermentation of a specific probiotic drink, kefir. Experiments were conducted using preliminarily activated kefir grains as a starter culture. Corrosion resistance was studied using a gravimetric and two electrochemical methods. The two steels showing the best corrosion performance differed mainly in their Mo and Nb contents. CONCLUSION: The results indicated that Nb played the most protective role against corrosion during kefir fermentation, since the steel containing Nb but no Mo showed the lowest corrosion rate. (C) 2011 Society of Chemical Industry