303 Growth Study, Metabolite Development, and Organoleptic Profile of a Malt-Based Substrate Fermented by Lactic Acid Bacteria Lorenzo C. Peyer and Emanuele Zannini, School of Food and Nutritional Sciences, National University of Ireland, University College Cork, College Road, Cork, Ireland; Fritz Jacob, Research Center Weihenstephan for Brewing and Food Quality, Technische Universität München, Alte Akademie 3, 85354 Freising-Weihenstephan, Germany; and Elke K. Arendt, 1 School of Food and Nutritional Sciences, National University of Ireland, University College Cork ABSTRACT J. Am. Soc. Brew. Chem. 73(4):303-313, 2015 The objective of this study was to investigate the fermentation of bar- ley malt extract by four different lactic acid bacteria (LAB) species and to analyze the effect on biological, physicochemical, and organoleptic attrib- utes of the resulting beverages. Malt and wort were analyzed following the Methodensammlung der Mitteleuropäischen Analysenkommission (MEBAK). Sugars and organic acids were evaluated using HPLC, while aroma compounds and ageing indicators were quantified using a head- space GC-FID. Unhopped wort was able to support the growth of all LAB during the whole experiment time (120 hr), with a cell count increase up to 3.63 log orders. The strain-specific preferences for carbon and nitrogen sources led to significant differences in the accumulation of metabolic byproducts (i.e., organic acids and flavor-active compounds released in the medium). LAB fermentation lowered the amount of some Strecker- aldehydes (2- and 3-methylbutanal and 2-phenylacetaldehyde) carrying “malty” off-flavors and increased dairy-related aroma compounds such as diacetyl and acetoin (“buttery”). The fermented samples were sensorially distinct and described with “bready”, “yeasty”, “yogurty”, or “honey” attributes. In general, LAB fermentation conferred flavor complexity to wort. Forced ageing of the fermented samples led to a large increase of “staling” indicators but these samples improved organoleptic stability compared with the unfermented control. Keywords: Ageing, LAB, Lactic fermentation, Novel beverages, Sen- sory, Strecker-aldehydes During the last few decades, the accumulation of scientific evi- dence linking nutrition and well-being has progressively steered the choices of the modern consumer toward healthier and natural food alternatives (26,68). This trend compels food companies to continuously work on novel formulations or adapt older ones to new standards (17). The increase in “functionality” is a wide- spread and commercially attractive way to improve the potential health benefits of food products (66). Functional beverages, in particular, have recently been widely popularized in the form of flavored waters, fruit juices, energy drinks, and teas (72). Cereals carry beneficial functions in the form of dietary fiber (1) and phytochemicals (e.g., sterols and phenolic acids) (2). There- fore, they constitute an attractive substrate for the development of novel, nonalcoholic, and functional beverages. The production of cereal-based drinks is an interesting way to diversify the product portfolio for many breweries and to relieve them from any major economic losses due to the general decrease in beer consumption (77). The implementation of this technology does not normally require a radical change in the existing plant and can take ad- vantage of any overcapacities present (43). Because unprocessed cereal-based products are often consid- ered bland or unpleasant in flavor (14), fermentation is often ap- plied in order to improve the palatability (49,60). Lactic acid bac- teria (LAB) can be used to increase the flavor complexity of these substrates. This heterogeneous group of gram-positive LAB have a long history of use in food products, and several of them have been granted “generally recognized as safe” status by the Food and Drug Administration. The use of LAB to ferment wort is ap- plied to regulate the pH levels during the production of beer aimed to be manufactured according to the German purity law (47). LAB fermentation gives rise to a wide range of volatile and nonvolatile compounds (e.g., organic acids, alcohols, aldehydes, ketones, and carbonyl compounds) (54). Depending on the meta- bolic features of the starter culture, as well as the cereal substrate and the manufacturing processes involved, different strains of LAB may generate characteristic and contrasting end products (6). The knowledge of which organoleptic-active compounds are being released during wort fermentation can help in the tailored formulation of novel, specialty “sour beers” inspired by European styles such as the Belgian Lambic or the German Berliner Weisse, or from traditional fermented beverages (83). Malting of cereals helps to provide better conditions for sustaining LAB fermenta- tion due to the higher amount of assimilable nutrients (13) and contributes to the aroma profile of the substrate (46). Sensory evaluation plays an essential role in profiling the flavor attributes and assessing the final consumer acceptance of a novel product (11). Maintaining the smell and flavor quality from bot- tling throughout the shelf-life of the product during storage repre- sents an enormous challenge. Natural deterioration takes place due to chemical reactions, mechanical stress during transporta- tion, light influence, thermal stress caused by inadequate storage conditions, and oxidative processes (57). Over the course of the product shelf-life, cereal-based beverages commonly experience an accumulation of staling compounds and a decrease in positive organoleptic attributes (81). For these reasons, the understanding of the evolution of the flavor profile during ageing is essential for the commercial success of a product. Numerous studies and re- views have been carried out on the origins of flavor deterioration in beer (21,70,75,79) but only a few have been considered the same problem for LAB-fermented cereal-based beverages (43). The main aim of this work was to study the suitability of barley malt-based wort to build a base for novel nonalcoholic beverages fermented by LAB. Biological, physicochemical, and organolep- tic changes were periodically studied for species of Weissella cibaria, Lactobacillus brevis, L. reuteri, and L. plantarum and related to the strain-specific metabolism. The flavor profile of the fermented samples was compared before and after simulated age- ing with the aim of understanding the main chemical transfor- mations responsible for “staling”. EXPERIMENTAL Bacterial Cultures and Reagents The microorganisms used as inoculum in this study (Table I) be- long to the culture collection of the Cereal and Beverages Research 1 Corresponding author: Phone: +353 21 490 1449; Fax: +353 21 427 0213; E-mail: e.arendt@ucc.ie http://dx.doi.org/10.1094/ASBCJ-2015-0811-01 © 2015 American Society of Brewing Chemists, Inc.