https://doi.org/10.17113/ftb.60.03.22.7474

Enzymatic Treatment of Spent Green Tea Leaves and Their Use in High-Fiber Cookie Production

Ngoc Doan Trang Nguyen^1,2, Thi Thuy Huong Phan^1,2, Thi Thu Tra Tran^1,2, Nu Minh Nguyet Ton^1,2, Dinh Le Tam Vo^1,2 and Van Viet Man Le^1,2*

¹Department of Food Technology, Ho Chi Minh City University of Technology (HCMUT), 268 Ly Thuong Kiet Street, District 10, Ho Chi Minh City, Vietnam

²Vietnam National University, Ho Chi Minh City (VNU-HCM), Linh Trung Ward, Thu Duc District, Ho Chi Minh City, Vietnam

Article history:

Received: 21 August 2021

Accepted: 11 May 2022

Keywords:

antioxidant; cookies; dietary fiber; enzymatic treatment; spent green tea leaves

Summary:

Research background. By-products of food industry have been studied as high fiber and antioxidant ingredients for healthy food products, because of their economic and environmental benefits. However, the soluble dietary fiber (SDF) content of these materials is usually lower than the recommended value that is claimed to bring great health effects. Enzymatic treatment could be an efficient method for modifying insoluble and soluble dietary fiber contents of these materials. The purpose of this study was to investigate the effects of enzymatic treatment conditions on SDF, insoluble dietary fiber (IDF), total dietary fiber (TDF) proportions of spent green tea leaves (STL) and evaluate the quality of dough and cookies, when different levels of untreated and treated STL were added to the recipe.

Experimental approach. The contents of SDF, IDF and TDF of STL powder was evaluated after STL was treated by cellulase preparation with enzyme loadings ranged from 0 to 25 U/g and treatment times ranged from 0 to 2 h. Wheat flour was replaced by untreated and treated STL powder at 0, 10, 20, 30 and 40 % in cookie formulation. Textural properties of dough, proximate composition, physical properties and overall acceptability of cookies were analysed.

Results and conclusions. The appropriate condition of enzymatic treatment was enzyme loading of 20 U/g and biocatalytic time of 1.5 h, under which the SDF content of STL increased by 144.5 % in comparison with that of the control sample. The addition of STL led to the rise in dough hardness. Increase in STL level also enhanced fiber content, antioxidant activity and hardness of cookies but reduced their overall acceptability. Moreover, the enzymatic treatment of STL improved the SDF to TDF ratio of cookies, which relates to health benefits, and their textural property. Untreated and treated STL added cookies at 20 % received the overall acceptance.

Novelty and scientific contribution. For the first time, enzymatic treatment of STL was performed to improve its SDF to TDF ratio. The treated STL is a new promising high fiber and antioxidant ingredient for cookies making.