Efficiency Assessment of Natural Biopolymers as Encapsulants of Green Tea (Camellia sinensis L.) Bioactive Compounds by Spray Drying

In this study a bottom-up approach of designing functional ingredients from green tea extract is proposed by a systematic investigation of 12 different natural biopolymers and their efficiency as carrier materials of green tea bioactive compounds by spray drying at low temperature (130 °C). Screening of carriers revealed that inulin and whey proteins provide the highest product yields (67.04 and 65.18 %, respectively) and, accompanied with pectin, also the highest total polyphenols (67.5–82.2 %) and flavan-3-ols (93.7–75.9 %) loading capacity. Up to 162 mg/g of (−)−epigallocatechin gallate (EGCG) was achieved, while low-caffeine contents (<5 mg/g) indicated the potential of obtaining low-caffeine functional ingredients. Employing alginate, carageenan and gums (acacia gum and xanthan) enabled the best colour preservation and highest chlorophyll content. Reconstituted green tea microencapsulates comprising modified starch, inulin or carageenan exhibited the lowest bitterness and astringency and the highest green tea flavour intensity as the most favourable sensory properties. An artificial neural network (ANN) designed based on the experimentally obtained results revealed hydrocolloid gums as the best encapsulants for achieving good physical properties, high EGCG contents and prolonged dissolution/release profiles while pectin, inulin and modified starch as the optimal ones in terms of the product yields, loading capacities and sensory properties. This indicates that a formulation comprising a combination of all of those biopolymers would provide potentially functional ingredients with encapsulated green tea phytochemicals, retained colour and improved sensory properties.