Sour dough bread

Lactic Acid B cteri. The lactic acid bacteria are ubiquitous in nature from plant surfaces to gastrointestinal tracts of many animals. These gram-positive facultative anaerobes convert carbohydrates (qv) to lactic acid and are used extensively in the food industry, for example, for the production of yogurt, cheese, sour dough bread, etc. The sour aromatic flavor imparted upon fermentation appears to be a desirable food trait. In addition, certain species produce a variety of antibiotics. 

Sour dough bread is made all over the world in both primitive and advanced societies. In primitive societies there is no alternative, but in advanced societies sour dough bread is made for its special flavour. Sour... 

Sour dough bread has a range of flavours that are not present in other bread also it keeps relatively well. The keeping properties, no doubt, originate from some of the products of the side-reactions that have taken place in the dough. There is no need to add propionic acid as a mould inhibitor as some is likely to be present naturally. Quite possibly, some of the substances produced by the fermentation would not be permitted as additives ... 

Types of Rye Bread. The usual descriptions are logical. Rye bread is bread made solely from rye flour, rye/wheat bread contains a minimum of 50% of rye flour while wheat/rye bread contains not less than 50% wheat flour with not less than 10% of rye flour. Some recipes for San Francisco sour dough bread have a proportion of rye flour. No doubt, originally, the prospectors used what ever was available. 

Some sour dough bread is made by using commercial yeast but with a proportion of genuine sour dough. Ordinary baker s yeast is at a disadvantage in rye sour dough because the low pH that is essential for rye bread is not the optimum pH for the yeast. 

Rye is grown mainly in the northeastern countries of Europe and in some locations in North America and Argentina.1 Rye is used mainly for human consumption and is the principal flour used in sour dough breads and in crisp bread. 

Marklinder, I., Haglund, A., and Johansson, L. 1996. Influences of lactic acid bacteria on technological, nutritional and sensory properties of barley sour dough bread. Food Qual. Pref. 7, 285-292. Marter, A.D. and Timmins, W.H. 1992. Small scale processing of sweetpotato in Sichuan province, People s Republic of China. J. Trop. Sci. 32, 241-250. 

It is worth mentioning a couple of special bread types produced by non-traditional fermentations. A well-known example is the San Francisco sour dough bread. This bread type accounts for more than 20% of the bread sales in the San Francisco Bay area (Sugihara, 1977). The sourdough fermentation is based on a highly specialised co-operation between the yeast Candida holmii and the lactic acid bacteria Lactobacillus sanfran-cisco (Sugihara, 1977). 

Rye Proteins. While rye is the only European cereal able to completely replace wheat in bread, rye protein is not as effective as wheat protein. One reason for this is that as much as 80% of the protein in a rye sour dough is soluble compared with 10% of soluble protein in a wheat dough. One factor that inhibits the formation of a gluten-like complex is the 4-7% of pentosans present, which bind water and raise the viscosity of the dough. The crumb structure is then formed from the pentosans in combination with the starch. 

Triticale flour has been extensively tested in Poland, a country where rye bread is traditional. The best results were obtained by using 90% triticale flour with 10% rye flour. The rye flour was made into a flour brew for 24 hours at 28-29°C. Half the triticale flour was made into a sour dough for 3 hours at 32°C followed by mixing with the rest of the ingredients plus 1.5% of salt on the flour weight. The bread was then scaled and proved for 30 min at 32°C followed by baking at 235-245°C. 

Traditional pitta bread is made by a sour dough process but it can be made using manufactured yeast. If the sour dough process is used a relatively large portion of sour dough (approximately 20%) is used, giving a more rapid fermentation than most sour dough products. 

There is a view that muffins originated in Wales. They were originally a sour dough flat bread. They seem to have disappeared from British life, except in a nursery rhyme. Presumably the original product had a short shelf life. The sort of product now sold as an English muffin has overcome some of these problems. The modem product is a disc shaped product about 7-10 cm in diameter and 2 cm high. 

The latter plays an important role with freeze-dried sour dough. The microorganisms cultivated on flour substrate already form a number of flavour constituents, which stick well to the flour matrix. The subsequent freeze drying preserves both, flavour and microorganisms. The resulting product saves time in the bakery and improves the quality of bread. 

Bread production has become increasingly industrialised. Moreover, consumer preference has altered towards loaves of good volume, ready-sliced for convenience and which stay soft for several days. At the same time, increased demand for speciality breads e.g. French baguette type, sour doughs etc.) has increased. 

Barber, B., Ortola, C., Barber, S., and Fernandez, F. 1992. Storage of packaged white bread. III. Effects of sour dough and addition of acids on bread characteristics. Z. Lebensm. Unters. Forsch 194, 442 149. 

Collar, C., Martinez-Anaya, M.A., and Benedito de Barber, C. 1994b. Interactive effects between microbial breadmaking starters and wheat flours on sour dough and bread quality. Rev. Esp. Cienc. Tecnol. Aliment. 34, 191-201. 

Kline, L., Sugihara, T.F., and McCready, L.B. 1970. Nature of the San Francisco sour dough French bread process. I. Mechanics of the process. Bakers Digest 44, 48-50. 

Rocken, W. and Voysey, P.A. 1995. Sour-dough fermentation in bread making. J. Appl. Bad. Symposium Suppl. 79, 38S-48S. 

Rosenquist, H. and Hansen, A. 1998. The antimicrobial effect of organic acids, sour dough and nisin against Bacillus subtilis and B. licheniformis isolated from wheat bread. J. Appl. Microbiol. 

Rye bread doughs may be acidified by acids such as lactic acid, acetic acid, citric acids or even hydrochloric acid (HCl). Dried sour doughs, which are not microbiologically active, are also used as acidifying agents. 

Yeast and lactic acid bacteria play important roles in the manufacture of bread. For wheat bread, yeast is today ascribed the major role, while for rye bread, which employs a sour dough, lactic acid bacteria as well as yeast are essential. 

A natural approach to avoid the use of additives in bread products may be reached by returning to the sour dough process using starter cultures. The use of selected strains with production of specific enzymes is the basis for production of the enzymes and dough conditioners directly in the sour dough. At present, two groups of enzymes are of particular interest in this respect amylases and proteases. 

Protease production. Often the question of the proteolytic activity of sour dough cultures is raised (Collar et al., 1990). Baking trials at our laboratory using high-proteolytic cultures did not significantly change the volume or structure of the bread compared with low-proteolytic cultures. 

Hansen and Lund, 1987). In rye bread, compounds such as alcohols, esters and carbonyls have been identified (Hansen et al., 1989). Choice of fermentation temperature, dough yield, flour quality and starter culture all influence the sensory properties of the final bread. Free amino acids formed during fermentation increase Maillard reaction products, thus intensifying the taste. Sensory analysis has shown that sour dough rye breadcrumbs had the most intense and bread-like flavour compared with chemically acidified doughs (Hansen et al., 1989). 

Hansen, A., Lund, B. and Lewis, M.J. (1989) Flavour of sour dough rye bread crumb. 

While the future of preserving bread by the addition of an organic acid seems secure, an alternative means for producing bread without the need for preservatives is receiving much interest in Britain. This is the use of the sour dough process. Although this process is popular on the continent and in parts of America for the production of rye bread, it has not been used in Britain except by small speciality bakers. In this process, dough... 

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