An efficient athermal extraction process for green tea, subduing the inherent disadvantage of low yield has been proposed. This process attained 90% total polyphenolic compounds and 96% extractable solids comparable with the conventional hot extraction. The extraction followed two-stage kinetics. A mathematical model with a new approach describing the kinetics of the second stage and extending the predictability to the yield of total polyphenolic compounds inclusive of the instantaneous first stage was deduced from fundamental mass transfer kinetics. The experimental data fitted well with the model (R² 0.941–0.999; RMSE 0.055–0.336). The overall mass transfer coefficient increased from 0.112 to 0.207 min⁻¹ with a particle size reduction from 1.96 to 0.108 mm. The EC₅₀ of DPPH radical scavenging activities of both cold (6.20 μg/mL) and hot extract (5.45 μg/mL) favourably compared with Trolox® (5.20 μg/mL). The cold extracted tea possessed superior organoleptic quality, having a bearing in the ready-to-drink tea preparation.

Industrial relevance

Cold brewed green tea has been reported to be superior in organoleptic characteristics and possesses similar or superior bioactivity compared to hot brewed tea. Low yield of cold extraction is the most prominent limiting factor in its industrial adoption. The proposed athermal extraction process could overcome this drawback and make the cold extraction industrially viable while offering a superior product.

中文翻译：

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非热提取绿茶：多酚类化合物提取的优化及动力学

已经提出了一种有效的绿茶无热提取方法，该方法克服了产量低的固有缺点。与传统的热萃取相比，该方法可获得90％的总多酚化合物和96％的可萃取固体。提取遵循两阶段动力学。从基本的传质动力学推导了具有新方法的数学模型，该模型描述了第二阶段的动力学并将可预测性扩展到包括瞬时第一阶段在内的总多酚化合物的收率。实验数据与模型非常吻合（R ² 0.941–0.999； RMSE 0.055–0.336）。总传质系数从0.112增加到0.207min ^-1，粒径从1.96mm减小到0.108mm。EC ₅₀与Trolox®（5.20μg/ mL）相比，冷（6.20μg/ mL）和热提取物（5.45μg/ mL）的DPPH自由基清除活性均有利。冷提取茶具有出色的感官品质，对即饮茶制备有影响。

行业相关性

据报道，与热冲泡茶相比，冷冲泡绿茶具有更好的感官特性，并具有相似或更高的生物活性。冷提取的低产量是其工业应用中最突出的限制因素。拟议的无热提取工艺可以克服这一缺点，并在提供优质产品的同时使冷提取在工业上可行。