The Impact of Incorporating Fresh and Dried Kenaf (Hibiscus Cannabinus L.) Leaves on the Physicochemical and Functional Properties of Value-Added Bread

Kenaf (Hibiscus cannabinus L.) is a rapidly growing plant highly regarded for its status as a fiber crop in Malaysia, alongside its rich bioactive compounds and pharmacological benefits. Despite its potential, many parts of the kenaf plant, including leaves, stalks, flowers, fruit, seeds, and roots, remain underutilized. This study explores the addition of fresh and dried kenaf leaves into bread to enhance its properties. The leaves were dried using two methods: an oven (at 180 °C for 1 h) and a dehydrator (at 65 °C for 16 h). A control bread without any kenaf leaves was also prepared. Initially, both fresh and dried leaves were assessed for color, vitamin C, total phenolic content (TPC), antioxidant activity, ash, and crude fiber contents. Subsequently, the bread's properties, including color, texture, TPC, antioxidant activity, ash, and crude fiber contents, were evaluated. Results showed significant differences in physicochemical and functional properties between fresh and dried kenaf leaves. Dried leaves exhibited darker coloration but had no significant differences in vitamin C and crude fiber contents compared to fresh leaves. Bread-containing dried kenaf leaves, whether oven-dried or dehydrator-dried, displayed darker colors with lower green saturation and higher yellow saturation. The incorporation of kenaf leaves increased bread hardness, gumminess, and chewiness while reducing cohesiveness, springiness, and resilience. Microscopic analysis confirmed consistent pore structures in all bread samples with evenly distributed kenaf leaf pieces. Bread with fresh and dehydrator-dried kenaf leaves showed higher TPC and antioxidant activities (16.8 and 16.0 mg GAE/g; 93.9% and 94.6%, respectively), followed by oven-dried (11.1 mg GAE/g; 87.3%), with the control bread having the lowest values (3.5 mg GAE/g; 65.8%). Significant variations were also observed in ash and crude fiber contents among breads with the inclusion of kenaf leaves and control. In conclusion, adding fresh kenaf leaves resulted in bread with superior physicochemical and functional properties.