Cheeses with blowing defect : problematics and preventable methods

Abstract: Blowing defect of cheeses refers to undesirable openness of the cheeses interior. It is a result of unwanted microbial metabolism. Production of hard- and semi-hard chesses require methods and/or preservatives to make sure that blowing defect is prevented. Most dairy industries have developed proper methods for this purpose, but it still remain a big problem for many cheese-producers. In this study problematics behind blowing defect was investigated. Preventing methods are compiled and the magnitude of the problem in the dairy industry was evaluated. Five Swedish large-scale dairy industries as well as two Italian tradition-al cheese producers have contributed with information about the importance of managing blowing defect at their factories. Cheeses frequently affected by blowing defect include brine-salted cheeses, cheeses ripened at hot temperatures and hard cheeses that are ripened for extensive periods. Low salt content, high levels of moisture content, water activity and pH as well as high initial amount of spores and/or somatic cell count favours spoilage. Swiss-type-, Dutch-type-, very hard Italian-type-, and Swedish Herrgård- and Grevé-type-cheeses are examples of cheeses susceptible for blowing defect. Pasteurization of cheese milk is the most common method for the prevention of spoilage bacteria. It inhibits non-sporulating microorganisms causing blowing defect; heterofermentative lactic acid bacteria, propionic acid bacteria, coliform bacteria and yeasts. However, it is not a guarantee for safe dairy products without spoilage organisms since thermoduric microorganisms and enzymes survives the process and sterilized milk is a good substrate for a lot of spoilage microorganisms. Endospores survive pasteurization and can germinate in the cheese during ripening if environmental conditions are favourable. Endospores are normally reduced by membrane filtration and/or bactofugation of the cheese milk. Sodium nitrate and lysozyme are common additives for the inhibition of spore-forming bacteria as well as other spoilage bacteria. More severe methods for the removal of spores exist, but they normally alter the cheese-making properties too much to be applied in the industry. Further development of processing techniques of cheese milk and research about combining different methods are needed to be investigated in order to ensure a cheese production without blowing defect, and without altering the cheese-making properties.