The yeast found in surface samples of the installations and equipment in our customer's factory (Bread and Viennese pastry production) turned out to be :\u00a0 Pichia anomala<\/strong>. In terms of nomenclature and taxonomy, this yeast was first described in 1894 by Hansen (Hansen, 1894). It has undergone numerous taxonomic changes and can be found in bibliographies under the names Hansenula anomala, Wickerhamomyces anomalus or Candida pelliculosa (NCBI international database).<\/p>\n They are asporogenous yeasts capable of growing under drastic environmental conditions such as low or high pH, very low humidity, high osmotic pressure and even anaerobic conditions (Fredlund et al., 2002). As a result of this extensive survival and growth capacity, Pichia anomala is one of the spoilage flora in dairy products, alcoholic beverages and bakery products (Bonjean et Guillaume, 2003).<\/p>\n In the bread and Viennese pastry sector, this yeast is therefore responsible for altering finished products by producing different types of metabolites such as ethyl acetate in very large quantities, but also ethyl propanoate, phenyl ethanol, 2-phenyl ethyl acetate, etc. These metabolites give off a strong solvent-like odour that can alter the organoleptic qualities of the food, leading to dissatisfaction among end customers and product recalls by the manufacturers concerned. This microorganism is classed as a germ that spoils bread-making products.<\/p>\n The Agence Nationale de S\u00e9curit\u00e9 Sanitaire de l'Alimentation, de l'Environnement et du Travail recently published an opinion (ANSES, Saisine n\u00b02012-SA-0003, July 2012) on the development and implementation of a \"guide to good hygiene practice and the application of HACCP principles for industries manufacturing biscuits and cakes and crisp and soft bread products intended directly for the end consumer\".<\/p>\n In this opinion, yeast Pichia anomala<\/em> is clearly identified as an indicator of process hygiene. This yeast must therefore be taken seriously, and its presence in high concentrations may be the sign of a failure or malfunction in the cleaning and disinfection protocol for equipment or surfaces in contact with food products. It should also be noted that there are currently no toxicological data on the molecules produced by this yeast. Toxicological assessments are currently being carried out in response to recommendations from ANSES, which will enable us to assess the real danger posed by the metabolites produced by this yeast. It is therefore essential to control the contamination of surfaces by this yeast and thus avoid the presence of metabolites in consumer products.<\/p>\n To take stock of the resistance and sensitivity of this yeast to the various disinfection processes (chemical, thermal, etc.), we will briefly review the existing data, bearing in mind that during the technical demonstration on your premises, steam was more than significantly effective. It should be pointed out that few scientific studies have dealt with the disinfection of this yeast, as Pichia anomala is reputed to be antifungal and to inhibit the growth of undesirable fungi such as Penicillium (Druvefors et al., 2005). In view of its growth capacity, any type of cleaning with a very or excessively large amount of water should be avoided, as this will contribute to the survival and persistence of Pichia anomala on surfaces.<\/p>\n For oxidising disinfectants such as hydrogen peroxide and peracetic acid, studies have shown the effectiveness of a hydrogen peroxide\/peracetic acid mixture at low concentrations (of the order of 6-8 %) in less than 15 min (APABIO<\/strong><\/span><\/a>manual spraying on surfaces after cleaning with a detergent. Industrial dry steam<\/strong><\/span><\/a>), achieving a logarithmic reduction greater than 4 (the minimum reduction required for yeast-killing efficacy) in clean or \"dirty\" conditions (Brougham, 1993). This type of oxidising molecule is also used for airborne surface disinfection, generating a hydrogen peroxide mist that disinfects all surfaces in contact with the air. This type of process has been shown to be effective against yeasts, achieving logarithmic reductions of over 4 log in less than 10 min at 20\u00b0C and less than 2 min at 40\u00b0C (APABIO\/AIRBIO<\/strong><\/span><\/a>).<\/p>\nSurvival and growth<\/h3>\n
Bread and Viennese pastries<\/h3>\n
Good hygiene practices<\/h2>\n
Cleaning<\/h2>\n
Disinfection<\/h2>\n
Dry steam<\/h3>\n