Enrichment of sourdough bread with hazelnut skin, cross‐linked starch, or oxidized starch for improvement of nutritional quality

Abstract Health concerns led to a shift toward the consumption of high dietary fiber bread. Additionally, climate change and supply chain concerns have led to the investigation of new sources of fiber utilizing waste products or co‐products of various crops, such as hazelnuts. The utilization of hazelnut skin also presents a value‐adding opportunity for hazelnut producers and processors. This research aims to investigate hazelnut skin as a dietary fiber source and to enhance the nutritional quality of sourdough bread with cross‐linked and oxidized starches. The in vitro starch digestibility significantly (p < 0.05) decreased with the addition of hazelnut skin at 5% and 10%. Sourdough bread with cross‐linked or oxidized starch had significantly (p < 0.05) higher slowly digestible starch and resistant starch contents and significantly (p < 0.05) lower estimated glycemic index (eGI). The addition of hazelnut skin caused a gradual increase in the dietary fiber content of sourdough bread. Oxidized starch significantly (p < 0.05) increased the soluble and insoluble dietary fiber. This study demonstrated that the hazelnut and modified starches positively affected the nutritional composition of sourdough bread, and starch‐phenolic‐fiber interactions might take place in bread‐making. The benefits gained from the enrichment of fiber in sourdough bread with hazelnut skin can support this as a high value ingredient in baking. Practical Applications Reducing waste is essential for food processing industries across the supply chain. Companies utilizing hazelnuts that wish to increase sustainability and reduce their carbon footprint will need to show how their suppliers are reducing waste. Positive interactions were observed between hazelnut skin and modified starch that enhanced nutritional quality of sourdough bread. This study shows the benefits of waste reduction in the food industry and how we can turn waste products into highly functional dietary components.