Yiannis Kourkoutas
Democritus University of Thrace, Greece
Biography
Yiannis Kourkoutas is an Associate Professor, Head of the Laboratory of Applied Microbiology and Biotechnology at the Department of Molecular Biology and Genetics, Democritus University of Thrace, at Alexandroupolis, Greece. Ηe obtained his PhD from the University of Patras, Greece at 2002 and he continued his Post-doctoral research in the field of Biotechnology at the University of Ulster, UK at 2002 and 2005, and at the University of Patras at 2004-2007. He has published more than 80 papers in peer-reviewed journals, 14 chapters in books, >100 conference proceedings (>10 invited talks) and four patents (citations >1250; h-index: 17). He has served as Chairman in several conferences, as Lead Guest Editor and an Editorial Board Member in many special issues and reputed scientific journals, as Member of the steering and organizing committees of a high number of international conferences and as evaluator of research proposals in national and European calls. His current main research focus is on development of novel functional food products with health-promoting properties and on exploitation of agro-industrial wastes for production of high-added value products. He has participated in many research projects, coordinating most of them. His funds derive from National Grants, ΕU, and the Food/Agriculture Industry.
Abstract
Low alcohol wines (<10.5% vol) represent a new trend in the global wine market driven mostly by modern lifestyle and environmental awareness, as well as economic reasons. In winemaking, mololactic (ML) fermentation usually occurs naturally and leads to reduced acidity, microbial stability, and improved sensory characteristics, but does not always proceed favorably under the natural conditions of wine. Thus, simultaneous alcoholic and malolactic fermentation that can be accomplished by yeasts in association with ML bacteria is suggested. As the use of wet cultures is incompatible with the industrial and commercial needs, freeze-dried cultures are considered preferable due to the advantages related to longer preservation times, resistance to microbial contamination and easy-handling during storage. Based on scientific evidence that cell immobilization results in enhanced fermentation productivity, maintenance of cell viability, improvement of product quality, and offers the ability for cell recycling, the aim of the present study was to evaluate the effect of freeze-dried immobilized kefir culture in low-alcohol wine-making. Kefir is a microbial consortium of yeasts and lactic acid bacteria that has been successfully tested in alcoholic and ML fermentation of wine and cider, recently. In this vein, repeated batch fermentations using freezedried free or immobilized cells produced with no cryoprotective agents were conducted at a wide temperature range (5-30oC). All systems demonstrated high operational stability for a period longer than one year. Ethanol content ranged 5.9-10.5% (v/v) depending on fermentation temperature and malic acid conversion up to 67.3% was noted. Concentration of higher alcohols was low in all cases and a significant reduction was observed at 5oC, indicating the high quality of the products. The main volatiles were identified by HS-SPME GC/ MS analysis were esters, organic acids, alcohols, and carbonyl compounds. Application of Principal Component Analysis showed that the fermentation temperature rather than the nature of kefir culture had a significant effect. Noticeably, all wines were accepted by the sensory panel during the preliminary organoleptic evaluation.