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

Abstract

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.