Use of sourdough fermentation and pseudo-cereals and leguminous flours for the making of a functional bread enriched of γ-aminobutyric acid (GABA) Rossana Coda, Carlo Giuseppe Rizzello ⁎, Marco Gobbetti Department of Plant Protection and Applied Microbiology, University of Bari, 70126 Bari, Italy abstract article info Article history: Received 31 July 2009 Received in revised form 11 November 2009 Accepted 6 December 2009 Keywords: γ-Aminobutyric acid Sourdough Pseudo-cereal Bread Leguminous Lactobacillus plantarum C48 and Lactococcus lactis subsp. lactis PU1, previously selected for the biosynthesis of γ-aminobutyric acid (GABA), were used for sourdough fermentation of cereal, pseudo-cereal and leguminous flours. Chickpea, amaranth, quinoa and buckwheat were the flours most suitable to be enriched of GABA. The parameters of sourdough fermentation were optimized. Addition of 0.1 mM pyridoxal phosphate, dough yield of 160, inoculum of 5 × 10 7 CFU/g of starter bacteria and fermentation for 24 h at 30 °C were found to be the optimal conditions. A blend of buckwheat, amaranth, chickpea and quinoa flours (ratio 1:1:5.3:1) was selected and fermented with baker's yeast (non-conventional flour bread, NCB) or with Lb. plantarum C48 sourdough (non-conventional flour sourdough bread, NCSB) and compared to baker's yeast started wheat flour bread (WFB). NCSB had the highest concentration of free amino acids and GABA (ca. 4467 and 504 mg/kg, respectively). The concentration of phenolic compounds and antioxidant activity of NCSB bread was the highest, as well as the rate of in vitro starch hydrolysis was the lowest. Texture analysis showed that sourdough fermentation enhances several characteristics of NCSB with respect to NCB, thus approaching the features of WFB. Sensory analysis showed that sourdough fermentation allowed to get good palatability and overall taste appreciation. © 2009 Elsevier B.V. All rights reserved. 1. Introduction γ-Aminobutyric acid (GABA), a four-carbon non-protein amino acid, acts as the major inhibitory neurotransmitter of the central nervous system (Krnjevic, 1974). Other physiological functions of GABA are induction of anti-hypertensive, prevention of diabetes, diuretic and tranquilizer effects (Jakobs et al., 1993; Cohen et al., 2002; Komatsuzaki et al., 2005, Adeghate and Ponery, 2002; Hagiwara et al., 2004). As the consequence, GABA is extensively used in pharmaceutical preparations and functional foods such as gammalone, dairy products, gabaron tea and shochu (Nomura et al., 1999; Sawai et al., 2001; Yokoyama et al., 2002). Glutamate decarboxylase (GAD) is the enzyme which catalyses the conversion of L-glutamate (or its salts) onto GABA, through a single- step α-decarboxylation (Ueno et al., 2000; Battaglioli et al., 2003). The capacity of lactic acid bacteria to synthesize GABA was also investigated with the aim of producing functional fermented foods (Komatsuzaki et al., 2005, 2008; Siragusa et al., 2007; Rizzello et al., 2008a,b). Pickled vegetables, and fermented meats and fishes were enriched of GABA using selected lactic acid bacteria starters (Komatsuzaki et al., 2005). Several GABA-enriched cereal foods are also manufactured: rice germ soaked in water, germinated brown rice treated by high-pressure, and germinated wheat and red-mold rice containing Monascus fungus (Siragusa et al., 2007). Only one study considered the production of a sourdough wheat bread enriched of GABA (Rizzello et al., 2008a,b). Overall, sourdough lactic acid bacteria have a well known role in improving the sensory, texture, nutritional and shelf-life properties of cereal-based baked goods. As previously stated, sourdough fermentation improves nutritional aspects, texture and palatability of whole grain, fibre rich or gluten-free products (De Angelis et al., 2007); stabilizes or increases the level of various bioactive compounds; delays the starch bioavailability thus decreas- ing the glycemic index; and increases the mineral bioavailability (De Angelis et al., 2007). Beyond the potential of sourdough fermentation, the selection of cereal, pseudo-cereal and/or leguminous substrates based on their nutritional and healthy potential is also of key importance to get optimal technology, sensory and healthy proper- ties. For instance, the supplementation of wheat flour with high- protein-content legume flours (e.g., bean and chickpea flours) improves the nutritional quality of baked goods and satisfies the consumption of vegetarian people since legume flours are rich in lysine and have the potential to overcome protein-calorie malnutri- tion (Gómez et al., 2008). Based on the total grain production, chickpea (Cicer arietinum L.), an annual herbage plant, is the third most important grain legume in the world (FAO, 1994). Proteins of chickpea are considered a suitable source of dietary proteins due to their optimal balance between essential amino acids, high bioavail- ability and low level of anti-nutritional factors (Clemente et al., 1999). Pseudo-cereals such as buckwheat, amaranth and quinoa may have International Journal of Food Microbiology 137 (2010) 236–245 ⁎ Corresponding author. E-mail address: rizzello@agr.uniba.it (C.G. Rizzello). 0168-1605/$ – see front matter © 2009 Elsevier B.V. All rights reserved. doi:10.1016/j.ijfoodmicro.2009.12.010 Contents lists available at ScienceDirect International Journal of Food Microbiology journal homepage: www.elsevier.com/locate/ijfoodmicro