Influence and Interactions of Processing Conditions and Starter Culture on Formation of Acids, Volatile Compounds, and Amino Acids in Wheat Sourdoughs

Abstract

Cereal Chem. 81(5):598-610The aim of this work was to study the influence of process parameters and the starter culture on the characteristics of wheat sourdough by using response surface methodology. Influence of fermentation temperature (16-32°C), ash content of flour (0.6-1.8%), and fermentation time (6-20 hr) were considered as independent factors and their effects were studied in sourdough fermented with Lactobacillus plantarum, L. brevis, Saccharomyces cerevisiae, or with a combination of yeast and lactic acid bacteria. Formation of acidity, free amino acids, and volatile compounds were considered the main responses. A possibility to enhance formation of potential flavor compounds and precursors without excessive acidity formation in wheat sourdoughs was established. The total amount of amino acids increased by 25-50%, depending on the strain and fermentation conditions. The total amount of volatile compounds increased seven-to 100-fold, depending on the strain and fermentation conditions. Sourdough started with S. cerevisiae was an effective way to optimize the amount of volatile compounds without excessive acidity formation in appropriate processing conditions. Ash content of flour and fermentation time were the most significant factors to modify metabolic activity of wheat sourdoughs. Frequent interactions between the studied factors were observed on the formation of acidity, amino acids, and volatile compounds with most of the strains studied. Possibility to improve current industrial fermentation processes and control flavor attributes of breads by using optimized sourdough was established.Wheat sourdough is an ancient way to improve textural and sensory properties of wheat bread (Brummer et al 1984; MartinezAnaya 1996; Kulp and Lorenz 2003). The potential of wheat sourdough is based on fermentation processes in which main components of flour (starch and protein) are modified and partly degraded. Starch degraded to monosaccharides and disaccharides is partly used by lactic acid bacteria and yeast present in sourdough to produce acidity (Röcken et al 1992). Proteolysis during sourdough fermentation produces amino acids, which are well-known precursors in bread flavor formation (Schieberle 1990;Gobbetti et al 1995;Thiele et al 2002). Lactic acid bacteria and yeasts also produce volatile compounds that may affect bread flavor (RichardMolard 1979;Lund et al 1989; Hansen and Hansen 1994a,b;Maloney and Foy 2003).Wheat sourdough has a strong acidic flavor which is not appreciated by consumers in most countries. Extensive acidity formation thus limits the amount of sourdough that can be used in the actual bread dough and may cause bitter bread flavor (Salovaara and Valjakka 1987;Meignen et al 2001).The degree of proteolysis and the amount of acids and volatile compounds formed depend both on what kind of lactic acid bacteria and yeasts are present and on the process parameters of sourdough fermentation such as fermentation time and temperature, dough yield, ash content of flour, and the presence of oxygen. Ind...

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Bread Making of Durum Wheat With Chickpea Sourdough or Compressed Baker's Yeast

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