Decentralized food production, usage of high-quality, local raw material, compliance with traditional processing methods, and preservation of nutritional value are attributes of Intermediate Food Value Chains (ivc) and may significantly contribute to the agri-food sustainability transformation. As these practices typically come with an extra cost, the consumer should be aware and convinced of them so that a premium price can be paid. But the food chain is complex and such a proof is challenging: Raw material come from multiple sources, it undergoes complex processing, while the package-imprinted attributes presently display mainly nutritional attributes. The large number of intermediates in the food supply chain adds to the complexity and fraud possibilities, while each production line has its own characteristics. This creates a challenge in terms of transparency and trust, from the consumer perspective. Blockchain as an open, distributed ledger can record transactions in a verifiable and permanent way and it promises transparency in food chains [1]. In this work, we investigate whether Blockchain can be sustainably applied in the dairy ivc of H2020 FAIRCHAIN project, identifying four challenges and our working practices. The ivc focuses on Feta cheese production; Feta is the most known, traditional Greek product of designated origin (PDO). It is based only on sheep and goat milk, under defined percentages, processed in specific regions, with requirements of minimum maturation periods. The information offered to the consumer covers the nutritional aspects and is difficult to verify. Challenge #1, which data to register, so that they are quantitative and meaningful? Through the FAIRCHAIN co-creation process we have identified a set of high-level attributes (taste, origin, integrity) and associated them with quantitative operational parameters in the end-to-end process, such as milk temperatures and pH, microbiological checks, milk mixing and percentages, maturation duration, IoT readings. These carefully selected attributes create the ‘digital product passport’. Challenge #2, how to guarantee the correctness of the data? If erroneous data are inserted at the edge, the Blockchain cannot correct them. While this risk cannot be eliminated, it can be mitigated with data verification rules (such as acceptable data ranges of input data), regular checks, and anomaly detection [2-4]. Challenge #3, how to rationalize Blockchain transaction fees and allow for verification on behalf of the consumer? Not all info can be registered in the Blockchain due to the need for performance and the transaction fees. While technological choices (such as the consensus algorithms) can affect the performance, the data granularity is an open question. Anchoring mechanisms (from private to public Blockchains). Data verification is based on (Ethereum) smart contracts and visualized through simple mobile app (confronting digital divide aspects as presented in [5]).Challenge #4, how to facilitate the involvement of stakeholders and build an application ecosystem? The offering of open APIs (Application Programming Interfaces) paves the way for an ecosystem of applications involving external stakeholders (such as public authorities for food certifications). The platform is currently reaching a stable version and it is undergoing evaluation for identifying adoption challenges and quantifying the operational overhead