Bread, fermentation

Patulin-producing strains are widespread as contaminants in food. Patulin has been found in mouldy bread, fermented sausage, commercial apple juice and animal food. The compound inhibits the growth of Gram-negative and Gram-positive bacteria however, it cannot be used as an antibiotic, for its has been shown that patulin is very toxic and teratogenic. The molecular basis for the toxicity is still unknown. 

Fermentation can be spontaneous or be induced by specifically added microorganisms. An everyday example of such an induced fermentation is the addition of baking yeast to flour to make bread or cakes. As with bread, fermentation can be done in a normal environment where many different microorganisms are present. A more sophisticated way is to exclude unwanted microorganisms by sterilization of the materials before adding a starter culture. 

During bread fermentation lactic and acetic acids, are formed, along with ethanol, esters, aldehydes, ke-... 

Nonetheless, toxic compounds, including biogenic amines (BAs) and ethyl carbamate, which are a potential risk to human health, may be synthesized by microorganisms present in the food. Ethyl carbamate is a genotoxic and carcinogenic molecule that may be present mainly in fermented beverages but also in bread, fermented milk products, and soy sauce. Wine is mostly at risk, since during the malolactic fermentation (MLF) different ethyl carbamate precursors such as citrulline, and to a lesser extent carbamoyl phosphate, are produced by yeasts or bacteria from proteins (Weber Sharypov, 2009). 

Urethane [51-79-6] (ethyl carbamate) occurs as a natural by-product in fermented products such as wine, Hquors, yogurt, beer, bread, oHves, cheeses, and soy sauces. Whereas urethane has a known cancer etiology in experimental animals, no such relationship has yet been proven in humans (108,109). Alcohol may act by blocking the metaboHsm of urethane, and thus exert a protective effect in humans consuming alcohoHc beverages (110). 

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. 

Lactic acid [50-21-5] (2-hydroxypropanoic acid), CH CHOHCOOH, is the most widely occurring hydroxycarboxylic acid and thus is the principal topic of this article. It was first discovered ia 1780 by the Swedish chemist Scheele. Lactic acid is a naturally occurring organic acid that can be produced by fermentation or chemical synthesis. It is present ia many foods both naturally or as a product of in situ microbial fermentation, as ia sauerkraut, yogurt, buttermilk, sourdough breads, and many other fermented foods. Lactic acid is also a principal metaboHc iatermediate ia most living organisms, from anaerobic prokaryotes to humans. 

Bakery Products. Sorbates are used in and/or on yeast-raised and chemically leavened bakery products. The internal use of sorbates in yeast-raised products at one-fourth the amount of calcium—sodium propionate that is normally added provides a shelf life equal to that of propionate without adversely affecting the yeast fermentation. Sorbates added at one-tenth the propionate level reduce the mix time by 30% (126). This internal treatment combined with an external spray of potassium sorbate can provide the same or an increased shelf life of pan breads, hamburger and hot-dog buns, English muffins, brown-and-serve roUs, and tortillas. The total sorbate useful in or on these baked goods ranges from 0.03 wt % for pan breads to 0.5 wt % for tortillas 0.2—0.3 wt % sorbic acid protects chemically leavened yellow and chocolate cakes (127). Emit-pie fillings and icings can be protected with 0.03—0.1 wt % sorbates. 

Milk and Milk Replacers. White pan bread was long made with about 3—4% nonfat dry milk (NEDM) in the United States, for reasons of enhanced nutrition, increased dough absorption, improved cmst color, fermentation buffering, and better flavor. Eor some years, however, sharply increased milk prices have led to a decline in its use in breadmaking. Many bakers have turned to the use of milk replacers to control the costs of their products, and these ingredients are now commonly utilized. Milk replacers were designed to dupHcate some of the functions and nutrition of milk. These blends may contain soy flour or cereals, with whey, buttermilk soHds, sodium or calcium caseinate, or NEDM. Milk replacers or NEDM used in bread dough amount to about 1—2%, based on flour. 

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