Access control in Multi-Organization Environment (MOE) is a critical issue. Several access control models need some improvements to be used in such environment where the behaviors of the users and the organizations may change during the collaboration. In similar environments, the use of trust management with an access control model is recommended. It is worth to mention that trust allow us to increase the security of the system, due to the fact it is dynamic, so it let us represent at runtime changes in the behavior of the players. In this paper, we aim to define trust of users and organizations in MOE. In these models, the initial valuation of the trust is crucial, in the sense that all the trust framework will depend on these initial values. In particular, in MOE these values should be computed using not only the experience of the users with an organization but also the experience of an organization with other organizations. However, the combination of these values normally is not an easy task. Therefore, in this paper we propose an algorithm that uses fuzzy logic to manage this information. In particular, this methodology allows us to extract the initial set of trust values of a MOE taking into account past experiences.