## 1 Introduction
### Related Work  
Taking into account the significance of the development of flexible and reliable agri-food traceability systems, several efforts have been presented in the scholarly literature in this direction. In brief, focusing on the recent literature for agri-food supply chains, indicative studies (without applying blockchain technology) include application of QR codes [41; 42; 43], RFID tags [44; 45], and also combination of QR codes with RFID technology [46; 47]. In [41], a traceability model was proposed for vegetables that utilizes QR codes as information carriers for identifying various aspects associated with cultivation, storage, processing and transportation, while web Service technology was used for exchanging information. Similarly, QR codes were applied in [42] and [43] for tracing a farm-to-fork  
Figure 1: An illustrative example of a fresh produce supply chain along with the information recorded in each stage within a block; products flow forward the food supply chain, while both forward and backward traceability can take place following the product in either top-down or bottom-up direction across the food supply chain, respectively. supply chain regarding vegetables and melons, respectively. In [44], RFID tags on products of a fruit warehouse and personal digital assistant devices were implemented. This semi-automatic traceability platform resulted in shorter time required as regards data analysis and management. In the same vein, [PERSON] et al. [45] used an RFID-based traceability system pertaining to live fish supply chain leading to valuable results for practical reference. RFID tags were also proposed in [46] in conjunction with QR codes for the design of a traceability system for wheat flour mills. QR codes were implemented to identify small packages of wheat flour, while RFID tags were used to record logistics information. This proposed system proved to be more efficient in terms of information queries than a system purely based on paper records. Both QR and RFID technologies were also implemented in [47] for tracing a prepackaged food supply chain together with XML to facilitate the sharing of information among different stakeholders. With the ledger technologies, such as blockchain, being more and more streamlined, several studies proposing cloud traceability systems started to gain ground [48; 49]. Cloud technologies can contribute to better real-time identifying, locating and tracking the status of products. This can facilitate the retrieval of useful data, analytics, storage and connectivity throughout the supply chain, which are significant aspects when it comes to traceability of perishable products so as to assure the required safety standards [50]. In short, [PERSON] et al. [48] proposed a Food Trading System with COnsortium blockchaini (FTSCON) so as to increase security and trust in transactions. Their results demonstrated that the proposed system can enhance merchants' profit. Finally, [PERSON] et al. [49] developed a blockchain focusing on supply chain system of agricultural products relying on a double chain architecture; a \"user information chain\" and a \"transaction chain\". This architecture proved to have the potential to considerably improve the trustworthiness of the platform and also the overall system's efficiency. More information about the implementation of blockchain for facilitating different functions of agricultural traceability systems can be found in recent review studies such as [29; 51; 52; 53]. In spite of the increasing interest in traceability systems regarding fresh produce, the available integrated IoT-based systems are scarce and at a relatively early stage of development.