Influence of pretreatment methods and addition of fragrant plants on Gnetum gnemon var tenerum powder tea
DOI:
https://doi.org/10.31989/ffhd.v15i1.1504Abstract
Background: Enhancing the utility of fresh vegetables, such as Liang leaves, is commonly achieved through drying and powdering as functional ingredients and food. In a preliminary study, Liang leaves displayed similar color, appearance, and texture attributes to Japanese and Chinese teas, but the flavor of the Liang drink significantly diminished. This research highlights the potential of the highly sought-after gastronomic vegetable, Gnetum gnemon var tenerum, as Liang, a Thai indigenous vegetable, but there is still a shortfall of scientific documentation. This work introduced the antioxidants of Liang leaves to create a new health-impact drinking product.
Objective: The research aimed to study the improvement of antioxidant activity and flavor using pretreatments, including withering, steaming, rolling, and steamed-rolling, and following the addition of fragrant plants.
Method: Liang leaves were pretreated by withering, steaming, rolling, and steaming rolling before drying. Then, the best condition was selected to add fragrant plants.
Results: Withering gave the highest total polyphenol content at 26.95±0.47 mg GAE/g DW compared with the other treatments (p<0.05), while higher DPPH scavenging activity was noticed in the steaming-rolling treatment (p<0.05). However, sensory evaluation results were not significantly different (p>0.05) in each pretreated tea. Steaming-rolling was selected based on the high antioxidant activity for further fragrance improvement using the powder of Pandanus amaryllifolius Roxb leaves and Chrysanthemum indicum L flowers at various ratios. The highest sensory score was recorded in tea made from a mixture of Liang leaf powder, P. amaryllifolius leaf powder, and C. indicum flower powder at a ratio of 60:0:40. The TPC and DPPH scavenging activities of the mixed tea powders were tested, with results of 25.08±0.93 mg GAE/g DW and 11.70±0.26 mg GAE/g DW, respectively. In addition, this product could be a good source of TPC and antioxidant activity judged by ascorbic acid as 332.33±6.94 mg AE / g DW.
Conclusion: The steaming-rolling treatment of Liang powder had the highest antioxidant activity, and then adding Chrysanthemum indicum L flowers powder at a ratio of 60:40 improved flavor, total polyphenol content, and antioxidant activity. The Thai indigenous vegetable, Liang leaves powder, is aimed for a novo alternative drink promoting health benefits.
Keywords: Liang leaves, Tea, Pretreatment, Flavor, Antioxidant activity
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