Multi-stage block freeze-concentration of green tea (Camellia sinensis) extract

Tea is the third most consumed beverage in the world. It has bioactive compounds that provide health benefits; for that reason, concentrating this product is a good alternative for different industries. Block freeze-concentration is a technology with the potential to be used to concentrate food solutions, preserving functional compounds. The aim of this work was to study the effect of block freeze-concentration on the total solids content, catechin content, polyphenol content, antioxidant activity and sensorial profile of green tea. Green tea extract at a 4% (w/w) solid mass fraction was freeze-concentrated in three successive stages at −25 °C. The effects of some parameters were evaluated, such as the concentration index, solid recovery yield, and concentration efficiency. After three stages, the solution was concentrated from 4% (w/w) to 14.1% (w/w) with a distribution coefficient of 0.43 and a total concentration efficiency of 81.6%. The efficiency of concentration decreased with the number of stages. The levels of catechins and polyphenols were increased by 4.5- and 3.4-fold in the final liquid fraction, respectively. The antioxidant activity was preserved after three stages of freeze concentration. The physicochemical parameters were maintained: of the 27 sensory attributes evaluated, 18 of them were retained. The results demonstrated that block freeze-concentration is a useful technique for preserving and enhancing the bioactive compound content and the functional properties of green tea extracts. •Green tea extract was freeze-concentrated by the block technique.•The content of bioactive compounds was increased after the concentration.•The technique preserved the functional properties of the green tea extract.•The sensory attributes of the extract were preserved.