how meat biota is influenced to encourage fermentation biota and discourage spoilage biota (and pathogens) in sausage making
Write a one to two page summary of the following learning objectives:
Understand:
- that foods were being fermented since the dawn of mankind
- how meat biota is influenced to encourage fermentation biota and discourage spoilage biota (and pathogens) in sausage making
- the unique properties of fish sauce fermentations
- the basics of pickle or sauerkraut fermentations
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This is module 8 covering some of the basics of non-dairy fermented foods and microbiology.
There is strong evidence that people were fermenting beverages in Babylon circa 5000 BC, ancient Egypt circa 3150 BC, pre-Hispanic Mexico circa 2000 BC, and Sudan area in Africa circa 1500 BC. There is also evidence of leavened bread in ancient Egypt circa 1500 BC. The importance of fermentation was the preservation of food and the reduction in likely foodborne illness. For example the wealthy in populated areas of Europe during middle ages never drank the water, they only drank beer and wine.
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Similar to fermented milks discussed in the last module, lactic acid bacteria are used to ferment the small levels of carbohydrates in meats to produce lactic acid. Naturally present Micrococcus can work, but more often a Pediococcus culture is added. In some cases glucose is added to the meat to enhance the fermentation.
Here is a typical flow chart for a salami type dried, fermented sausage. Ground meats are mixed with spices, curing salts, and salt. Then starter cultures are added. Since fermentation is carried out at ambient temperatures, the goal is to rapidly acidify the meat to prevent pathogen growth. Once enough acid is produced, the sausage may be smoked for flavor and then dried to a low moisture content. The dried the sausage is packaged, warehoused and then finally shipped.
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The sausage biota is the same as the meat source. The microorganisms listed are for beef biota. Since most sausage is ground, the biota is fully distributed. Pediococcus has been added to the list since it will be added as a starter culture. Salt in the spice mix will inhibit some of the non-lactic acid bacteria biota from growing. During fermentation the haloteolerant Micrococcus and Pediococcus rapidly ferment sugars into lactic acid.
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Sausage pathogens are also the same as the meat source. For example, the number one hazard in beef sausage is E. coli O157:H7. During fermentation the pH of the meat drops, but not to a level to inhibit E. coli. Starter culture competitive inhibition will make it harder for E. coli growth, but not eliminate it. If the sausage is smoked, then heat may contribute to the destruction of E. coli, but only a full cooking lethality will eliminate it. Finally, drying can also minimize E. coli, but it is known that E. coli can survive drying for periods of time. Since it is not clear that destruction of E. coli will occur, the USDA mandates manufacturers to demonstrate that their specific process results in a 5 log kill of E. coli O157:H7.
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There are literally thousands of fermented foods known to man. A summary can be found in the WIKI encyclopedia at the link shown. We’ll take a look at just a few different fermented foods in the next few slides.
Fermented fish sauces are an Asian staple. Salt is added to uneviscerated fish at approximately 30-35%. The traditional method placed the salted fish in a sealed pot buried in the ground for 6 months. During this time the halophilic fish biota primarily streptococci, micrococci, and staphylococci liquefy the fish (bones and all) with the help from proteases from Bacillus. The main reason that few pathogens survive is 30-35% salt.
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Most breads are made using standard bread yeast, Saccharomyces cerevisiae, seen here colored in light blue. However, there are many traditional breads that either use wild yeast or use a mother culture that has been perpetuated for decades to centuries.
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San Francisco sourdough bread is one example of a historic fermented bread. The culture has been perpetuated for hundreds of years. It has been extensively studied. The culture is commensal. A yeast Saccharomyces exigus and bacteria Lactobacillus sanfrancisco both work together to make the characteristic sourdough bread. The Saccharomyces breaks down flour (starch) into maltose while the Lactobacillus can only use maltose to ferment into lactic acid. The result is a sour dough with an excess of maltose. During baking the maltose contributes to a very crisp crust.
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Two common fermented vegetables are cabbage and cucumbers. Cabbage ferments into sauerkraut and cucumbers into pickles. This fermentation is traditionally performed by the resident lactic acid bacteria that are present on the normal biota of the cabbage or cucumbers. Similar to the sausage fermentations, salt is added to inhibit the remaining normal biota. Unlike meats, water is added to help form a brine. The lactic acid bacteria then ferment the vegetable sugars into lactic acid acidifying the brine. The acid adds flavor and inhibits C. botulinum and a few other pathogens. Commercially, sauerkraut or pickles are jarred and pasteurized to kill off vegetative pathogens and the fermentation biota.
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Soy sauce and miso have been a traditional Asian sauce since the 1600’s. Traditionally, soybeans were soaked, cooked, mashed and then formed into balls. The balls of starch were then allowed to be infected by molds for some 30 days. The mold infected balls were called Koji. The main mold was Aspergillus oryzae. It produces proteases, amylases, and lipases that hydrolyze their respective substrates into sugars. After 30 days the balls were crocked with water and salt at 10% for up to a year. The starch brine is called moromi. Fermentation is mostly due to Pediococcus cerevisiae, Lactobacillus delbruekii, and salt-tolerant Saccharomyces rouxii. The end product is a paste called miso. If miso is filtered, the juice is soy sauce. Naturally, a commercial process is a little cleaner. In addition, many soy sauces now contain wheat in addition to soybeans.
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As mentioned earlier, there are thousands of fermented foods. Some of the other more popular food include Wine (fermented grapes and fruit juices), Cider (fermented apples and fruit juices), Whiskey (fermented then distilled barley, wheat, corn and rye), Arrack & Sake (fermented rice), Pulque and Mezcal (fermented and distilled agave), Vodka (fermented and distilled potatoes), Vinegar (fermented rice, wine or cider). Vinegar is an interesting fermentation. First a yeast such as Saccharomyces cerevisiae ferments sugars into ethanol, then Acetobacter aceti converts the alcohol to acetic acid.
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