Supply chain management, product provenance and quality certification are among the first and most popular applications of blockchain technology, due to the inherent trust and inalterability provided by the blockchain technology. However, the proposed supply chain management systems based on blockchain and smart contract technology tend to be specific to the particular production and production process. In this paper we present a general-purpose approach for the agri-food supply-chain management, proposing a system that can be configured for most agri-food productions. The primary purpose is to provide a methodology to facilitate and make more efficient the development of such applications. It is based on general smart contracts and apps interacting with same smart contracts, which are configured, starting from the description of the specific system to be managed, given using json files. A case study on olive oil production is described, to show how our approach works.