**6. Conclusions, Limitations, and Future Research Agenda**

Coordinating food supply chains is challenging and complex due to the perishable nature of the products and volatile yields of raw material production. Implementing sustainability standards in food supply chains is increasingly requested by customers but represents an additional challenge. The implementation of sustainability standards has so far mainly been examined at individual stages of supply chains (e.g., raw material production or manufacturer), without considering the holistic implementation of the standards [7]. However, sustainability standards should be introduced at all supply chain stages, from raw material producers to end retailers, to receive long-term sustainability. We used a single case study at all levels of a sustainable food supply chain to analyze the different GMs used to coordinate the implementation of sustainability standards throughout the whole supply chain. Thereby, we analyzed the effects of the used GMs and highlighted the intentions behind why certain GMs were applied. We show that the effective, holistic management of sustainability governance relies on different mechanisms at different supply chain stages. At the beginning of the supply chain, contracts are used to ensure economic sustainability, while information and knowledge sharing are specifically used to increase environmental and social sustainability. At the later stages of the supply chain, contracts and informal information sharing are used to increase economic sustainability, while social and environmental sustainability is ensured through certificates. Without the holistic management of the supply chain by the trading company, sustainability efforts at the individual stages would not be aligned. For example, the first stages of the supply chain would not seek to certify the cocoa, which would compromise the sustainability efforts of the downstream stages, which rely mainly on certificates. Therefore, we not only highlight the mechanisms used at the individual stages, but also emphasize the relevance of the trading company in its overarching coordinating function for the long-term enhancement of sustainability in the complete supply chain.

Even though the case study research was conducted carefully and with regard to several quality criteria, the results show several limitations, offering future research possibilities. While conducting a single case study enables the collection of very detailed data from each stage of the supply chain, it also limits the transferability and generalizability of the results. We placed a lot of emphasis on the representative character of the examined

supply chain, taking into account that the supply chain produces a common product (confectionaries) with usual ingredients (e.g., cocoa) and that each stage of the chain pursues activities to comply with economic, environmental and social sustainability standards. Additionally, the representative character of our research is fostered through the ability to comprehensively analyze each stage of the investigated supply chain, which makes it easier to transfer the results to other agricultural supply chains. However, Yin [40] states that case studies can be used to develop new theoretical constructs, but not to generalize their results to a broader 'population'. Therefore, we call for quantitative survey research to test our propositions and ensure their transferability to other supply chains. For example, it can be quantitatively discussed at what level in the supply chain certificates are the preferred mechanisms to enforce social and ecological standards. In addition, the role of contracts should be quantitatively investigated to examine whether they are also used in other supply chains to ensure economic and not social and ecological sustainability.

Next to a comprehensive quantitative analysis of governance mechanisms to enhance sustainability, we call for research that examines ways to measure the effects of governance mechanisms on the different sustainability dimensions. By being able to measure the effects of governance mechanisms, the effort/benefit ratio of the mechanisms can be better estimated and, accordingly, the sustainability goals can be achieved more efficiently.

Furthermore, it is remarkable that the sustainability efforts in the examined supply chain focus particularly on ecological and economical sustainability. The low consideration of social sustainability aspects is also a phenomenon that appears in the literature [55]. Future research should therefore focus more on the implementation of social sustainability goals in food supply chains through the specific usage of GMs.

In addition to the limitations, the current challenges mentioned during the interviews also result in future research needs. Especially in the logistics and production industry, price competition is very high, and there are hardly any industry-wide sustainability standards or certificates. We, therefore, call for the development of sustainability certificates that specifically address environmental and social sustainability in the manufacturing and logistics industry. Additionally, future research could investigate whether such industrywide certificates can reduce cost pressures in the industry.

Further, few information technology tools were used to support GMs in the supply chain considered. Future research should focus on integrating technologies, such as blockchain technology, artificial intelligence, or the Internet of Things to enhance sustainability in food supply chains. Blockchain technology can be used, for example, to create credible transparency regarding the compliance with social and environmental sustainability standards in supply chains in which partners do not trust each other [56]. Therefore, future research could explore how from raw material production to retailers, blockchain technology can be used to increase credible transparency in food supply chains. Further, Wang [57] shows, for example, how Internet of Things and data mining can be used to collect data in the food industry and analyze them to enhance the quality of products. The systematic collection and analysis of data could also be used for sustainability-related goals, e.g., to avoid food waste by detecting overstocks at an early stage.

When exploring the potential use of new technologies in the food industry, comparing other industries would be useful to transfer existing concepts (e.g., blockchain governance [58]) to food industry supply chains.

**Author Contributions:** Conceptualization, J.K., M.J. and R.L.; Data curation, J.K. and M.J.; Formal analysis, J.K. and M.J.; Investigation, J.K. and M.J.; Methodology, J.K. and M.J.; Project administration, J.K. and R.L.; Visualization, J.K.; Writing—original draft, J.K. and M.J.; Writing—review & editing, M.J. and R.L. All authors have read and agreed to the published version of the manuscript.

**Funding:** This research received no external funding.

**Data Availability Statement:** Not applicable.

**Conflicts of Interest:** The authors declare no conflict of interest.
