The Impact of Eggplant Peel Fortification as a Potential Source of Dietary Fibers and Phytochemicals on the Rheological Properties and Quality of Pan Bread

Eggplant peels (EPP) are the primary byproduct of eggplant, which is mainly produced by food manufacturers and restaurants and contains substantial quantities of bioactive compounds. This study aimed to assess the impact of using EPP as a dietary supplement for wheat flour to enhance its phytochemical and dietary fiber content. The study examined the effects of fortifying EPP at four different levels (2.5%, 5%, 7.5%, and 10%) on the phenolic content, antioxidant activity, and rheological characteristics, baking quality, staling rate, texture, microstructure, and sensory qualities of the pan bread. According to the chemical profile analysis, EPP is a special source of phenolic compounds and dietary fiber. The peel of eggplant contained 48.76% total dietary fiber (11.04% soluble and 37.72% insoluble dietary fiber) compared to 2.89% total dietary fiber for wheat flour. Eleven phenolic compounds were identified in EPP. Chlorogenic acid was the abundant compound (311.77 μg/g), followed by chrysin (75.08 μg/g) and ferulic acid (29.95 μg/g). Water absorption of wheat flour (57.6%) increased gradually with increasing the EPP level to reach 64.2% for wheat flour containing 10% EPP. Specific volume of pan bread samples reduced as the concentration of EPP increased. The total color difference (∆E) exhibited a significant increase as the level of replacement increased. The hardness of fortified bread samples increased gradually with increasing addition levels of EPP. Cohesiveness recorded the highest value in EPP 10%, whereas EPP 2.5 and 5% bread samples recorded the lowest value. In general, the addition of EPP in pan bread affected how consumers evaluated the product. However, consumers still showed acceptance towards all processed products. Microstructure results reveal that the cell structure of bread containing 2.5 and 5% EPP was similar to the control sample. During a 72-hour of room temperature storage, eggplant peels showed significant effects in delaying the staling of baked pan bread. It can be concluded that EPP could be considered a functional ingredient in the food sector and added to either functional or enriched fiber foods.