Aplicación de diferentes técnicas analíticas para evaluar la contaminación fúngica de alimentos y superficies
Fungi represent a growing concern for our society as human health pathogens and as contaminants of foods, air and the interior surfaces of our homes. Thus, the implementation of different risk control strategies like cleaning and disinfection programmes for food production and commercialisation becomes mandatory. For these programmes it is important to establish critical limits and to apply an adequate system for assuring its surveillance and fulfilment. The selection of an adequate disinfectant agent to reduce or destroy ambient and surface micobiota and the application of techniques that allow us to evaluate the efficacy of the disinfection has to be taken into consideration. This sort of techniques present advantages as well as inconveniences and for every particular industry it must be stated which one achieves the best evaluation of surface contamination. Analysing fungi contamination can be a hard task and requires prolonged times for consecution of results which in return, limits the use of corrective actions.
On this study was developed an impedanciometric method for counting fungi. The culture medium that showed best responses to capacitance methods was the one containing: soy peptone and yeast extract (0.5%); gelatine (8%) and cloramphenicol (0,025%) adjusted to pH 5.5. This medium allowed spore count of the main fungi genera (Aspergillus, Cladosporium, Penicillium and Rhizopus) isolated in foods and surfaces of dehydrated-food producing facilities in concentrations between 102 to 106cfu/g. The time of analysis varied between 26 and 70 h depending on the dominant genera.
Moreover, different sampling techniques for surveillance were compared and fungi contamination was assessed, after applying surface cleaning and disinfection procedures in a dehydrated food manufacturing industry. Fungicide activity of four disinfectant solutions related to the dominant micobiota of these surfaces was evaluated. Critical limits were established as a function of the sampling techniques and analyses chosen. From the techniques used the one which yielded higher counts and permitted more accurate qualification of food surface acceptability was the direct spread of stainless steel discs which were previously adhered to the surfaces during one week. Impedance measures were of limited use as system of verification. The disinfectant agents that showed higher efficacy against the dominant micobiota in the processing facilities were: sodium hypochlorite (1000 mg/L of free chloride) and a 1% solution of a product containing aldehydes and quaternary ammonium.
Finally, the degree of surface contamination inside food commercialising installations was determined. The highest fungi counts were obtained using agar contact plates techniques, direct spread of stainless steel discs and swabbing of 100 cm2. Yeast were the dominant micobiota in the refrigerating commercialisation areas whereas for room temperature products fungi of the genera Penicillium and Cladosporium prevailed.
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Advisor:Hernández Herrero, Ma. Manuela; Rodríguez Jerez, José Juan
School:Universitat Autónoma de Barcelona
Source Type:Master's Thesis
Keywords:458 departament de ciències animals i dels aliments
Date of Publication:10/26/2007