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Immobilized cell technology has shown a significant promotional effect on the fermentation of alcoholic beverages such as beer, wine and cider. However, genetic, morphological and physiological alterations occurring in immobilized yeast cells impact on aroma formation during fermentation processes. The focus of this review is exploitation of existing knowledge on the biochemistry and the biological role of flavour production in yeast for the biotechnological production of aroma compounds of industrial importance, by means of immobilized yeast. Various types of carrier materials and immobilization methods proposed for application in beer, wine, fruit wine, cider and mead production are presented. Engineering aspects with special emphasis on immobilized cell bioreactor design, operation and scale-up potential are also discussed. Ultimately, examples of products with improved quality properties within the alcoholic beverages are addressed, together with identification and description of the future perspectives and scope for cell immobilization in fermentation processes.

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 lowcaffeine 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.