Functional analysis of unfermented and fermented citrus peels and physical properties of citrus peel-added doughs for bread making.

Several studies have indicated citrus peels (CP) contain specific methoxy flavones, e.g. nobiletin and tangeretin, which have been shown to prevent numerous diseases. However, research reports regarding their application as food additive in healthy baked products is scarce. In our study, both unfermented (UF) and fermented (F) citrus peels were processed under different dry hot-air temperatures to make four citrus peel powders , UF-100 °C,UF-150 °C, F-100 °C, F-150 °C, respectively. The analysis of the basic components and nutraceuticals as well as antioxidant activity were conducted. Various percentages of CP were added to dough and toast bread for physical property and sensory evaluations. The results indicated the contents of crude proteins (3.3-4.3 mg/g) and fibers (10.9-14.9 %) among the four samples were similar. The UF extracts showed better antioxidant activities than F extracts. HPLC analysis indicated the contents of hesperidine, nobiletin and tangeretin in CP extracts were UF-150 °C > UF-100 °C. Farinograph analysis indicated a linear relation between CP powder content and the parameters of the physical properties of dough. A high percentage of fibrous CP powder in dough increases the water adsorption capacity of the dough, resulting in a decrease in its stability The sensory evaluation results indicated a greater acceptability of UF-added toast bread relative to the F-added one. Among these, according to the statistical anaylsis, the UF-150 °C 4 % and UF-100 °C 6 % groups were the best and F-150 °C 2 % group was the poorest in overall acceptability.