Browsing by Subject "sitominen"

Aflatoxins are harmful compounds found in food and feed. The literature review of this thesis looked at aflatoxin M1 (AFM1) found in milk and its occurrence, significance and prevention methods using lactic acid bacteria (LAB). Furthermore, the assay methods of aflatoxins and the factors affecting the analysis were discussed. The aim of the experimental work was 1) to investigate the ability of five LAB strains to bind AFM1 in vitro and 2) to investigate how different matrixes affect the assay of AFM1 and to evaluate the feasibility of the selected ELISA kit for the study. In the first phase of the study the AFM1 concentrations of three different matrixes were analyzed using ELISA when known concentrations of the AFM1-standardsolution were added (0, 20 ja 40 ppt). In the second phase of the study the abilities of five LAB strains to bind AFM1 in UHT skimmed milk and MRS-broth were investigated. The bacterial suspensions were incubated at +32 °C for one hour, and the AFM1 concentration in the matrixes were 50, 15 and 10 ppt. The unbound AFM1 concentrations of the supernatants were analyzed from the samples using ELISA. The unbound AFM1 concentrations were converted to the proportional portion of the bound AFM1. In this study, statistically significant differences were observed in the abilities of the LAB to bind AFM1. The viable cells of strain B2 27 (Lb. plantarum-, pentosus- or paraplantarum) were the best binders of AFM1. They removed 43.7 % AFM1 in UHT skimmed milk, where the AFM1 concentration was 15 ppt. Unlike in previous studies viable cells bound AFM1 better than the heat-killed cells. The used ELISA kit was a sensitive method for analyzing low concentrations of AFM1, but at higher concentrations the assay results were inaccurate. The nonspecific interaction due to the components of the matrixes had to be taken into account when the results were reviewed. In the future, it may be possible to utilize the LAB strains, such as B2 27 for reducing AFM1 the concentration in milk and probably in other foodstuffs. There is a need to develop a practical application which can be used in the binding of AFM1 using lactic acid bacteria and thus reduce the bioavailability of AFM1.