Athermal extraction of green tea: Optimisation and kinetics of extraction of polyphenolic compounds

• Published in: Innovative food science & emerging technologies 2018-12, Vol.50, p.207-216
• Main Authors: Murugesh, C.S., Rastogi, Navin K., Subramanian, R.
• Format: Article
• Language: English
• Subjects: Catechins; Cold extraction; Green tea; Mathematical model; Particle size; Polyphenols
• ISSN: 1466-8564; 1878-5522
• DOI: 10.1016/j.ifset.2018.06.005

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. 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. •Optimisation of cold extraction improved the yield to match hot extraction yield.•Cold extracted solids displayed superior chemical and organoleptic qualities.•A mathematical model was proposed for two stage extraction kinetics of green tea.•Particle size has major influence on total polyphenols and solids yield.•The proposed process makes cold extraction industrially more viable.