Lesson 9 Flashcards
preservation by biotechnology
Biotechnology
application of science and engineering in direct or indirect use of living organisms (or their parts) in their natural or modified forms
e.g. fementation (uses microorganisms, enzymes), plant and animal breeding, cell and tissue culture, genetic engineering
Food products obtained by biotechnology
- fermented beverages (e.g. wine, beer, sake)
- fermented dairy products (e.g. yogurt, specialty cheeses, cheddar cheese)
- fermented meat products (e.g. salami, bologna, prosciuto)
- traditional fermented foods (e.g. sauerkraut, soy sauce, tempeh, idli, yakult, miso)
Ingredients and additives obtained by biotechnology
- amino acids (e.g. methionine, glutamic acid)
- biopolymers (e.g. xanthan gum, alginates)
- enzymes (e.g. chymosin, rennin)
- vitamins (e.g. B-vitamins)
Food fermentation vs biotechnology
- fermentation: practiced in agriculture and food industries for 1000s years (e.g. yogurt production in India, bread in Egypt)
- biotechnology: new term that also includes the use of probiotics, genetically modified organisms for production of ingredients, etc.
2 preservation principles of biotechnology
- microbial antagonism: good MO suppresses growth and metabolic activities of spoilage-causing microflora
- good MO produces metabolites (e.g. antimicrobial compounds like acids and alcohols), the end products of fermentation
acids can lower pH of food (below 4.6), requiring additional methods for preservation
2 main benefits of fermentation
- increased nutritional value and availability (compared to starting material)
- adds variety to our food supply/diet
3 nutritional benefits of fermentation
- mould fermented foods can product B-vitamins
- microbial hydrolysis of cellulose materials (into glucose) that are indigestible by humans
- liberates nutrients from plants
Fermented products using lactic acid bacteria
- dill and sour pickles (from cucumbers)
- green and ripe olives (olives)
- sauerkraut (cabbage)
- coffee beans (coffee cherries)
- vanilla (vanilla beans)
- meat sausages/salami (meat)
- sour cream and yogurt (dairy)
- naturally occurring in olives and sauerkraut
- produces lactic acid from glucose and lactose
Fermented products using yeasts
- beer, ale, stout (malt)
- wine and vermouth (grapes)
- brandy (wines)
- saké (rice)
- bread (bread dough)
produces ethanol from glucose and other fermentable carbohydrates
Fermented products using mould
miso and soy sauce (soybeans)
5 factors affecting fermentation
- starter culture
- formation of metabolites
- temperature
- oxygen
- salt
Starter cultures
specifically selected microbial cultures with desireable traits for the particular fermentation (i.e. metabolism leads to desired products like acids, alcohol, flavor compounds)
provide an environment for the microorganism to become dominant
3 kinds of starter cultures
- as a pure culture (e.g. yeast in bread)
- from a previous batch of the fermented food containing that culture (e.g. sourdough or yogurt culture)
- part of the normal microflora (e.g. sauerkraut, olives)
Effect of temperature on starter cultures
starter cultures will only grow at their optimum temperature
2 kinds of oxygen requirements in fermentation
some fermenting MOs grow better under aerobic conditions, some grow better under anaerobic conditions, and some can tolerate both
e.g. baker’s yeast is both aerobic (increase mass) and anaerobic (ferments sugars faster)
Effect of salt in fermentation
e.g. lactic acid bacteria
adding salt to the fermenting product:
* favors growth of lactic acid-producing bacteria (becomes dominant faster)
* inhibits growth of spoilage/disease-causing MOs (synergistic effect between acid and salt)
lactic acid bacteria can tolerate high concentration of salt
6 steps of cheese making process
- pasteurization of raw milk
- addition of starter culture (e.g. lactobacillus bulgaricus, staphylococcus thermophilus)
- rennet: addition of enzymes (e.g. non-pathogenic E. coli), which breaks down proteins and works with the starter culture to coagulate milk
- curd formation: curd is separated from whey (liquid), then undergoes matting and cheddaring
- salting, pressing, and ripening
- packaging
simple forms of cheese are white and cheddar cheese! while others require secondary starter cultures
Cheddaring
in the cheese making process
cutting of the matted curd and piling of the blocks on top of one another
What aspects of cheese result in preservation?
longer shelf life compared to milk
- lower moisture content and water activity
- lactic acid bacteria creates acidic conditions (metabolites) and exhibits microbial antagonism
- salt lowers water activity and inhibits the growth of proteolytic microorganism (e.g. putrefactive bacteria that produces foul odor)
What aspects of cheese making result in different varieties of cheese?
- kind of milk (e.g. pasteurized or not, cow, goat, sheep)
- method for curd formation (e.g. acid, enzyme, or acid-heat coagulation)
- specific starter cultures, time, temperature of cooking (affects moisture content)
- washing, matting, pressure
- ripening time (affects pH or acidity)
Swiss cheese
a hard cheese
- starts as cheddar cheese through lactic acid bacteria fermentation
- propionic acid bacteria (Propionibacterium shermanii), a secondary starter culture, added, which metabolizes lactic acid into carbon dioxide, proline (sweet), and propionic acid (nutty)
Camembert and brie cheese
a soft cheese
- surface is sprayed with mist of mould mycelia spores (Penicillium camembertii or candidum), creating a white coating
- curds are not pressed, making it soft
- enzymes proteases breaks down proteins, producing small molecular weight peptides that contribute to soft and creamy texture
mould-ripened like blue cheese!
Blue veined cheese
a semi-soft cheese
- starts as cheddar cheese through lactic acid bacteria fermentation
- mould (Penicillium roquefortii) grows throughout the curd, which is needle-inoculated with mould, making channels for oxygen
- produces blue color and distinct flavors (sharp and peppery) with enzyme lipase, freeing up fatty acids, aldehydes, and ketones
blue cheese (U.S.), stilton (England), Gorgonzola (Italy) are from cow’s milk while roquefort (France) is from sheep’s milk
What are GMOs?
plants, animals, and MOs that undergo a change in their heritable trait(s) by intentional manipulation
- e.g. modern gene technologies: foreign piece of DNA is inserted into the genetic material of the host organisms
- GMO is an example of biotechnology and genetic engineering is a technique used in GMOs
How is genetic engineering used in cheese making?
- improve the starter cultures (improved resistance to viruses like bacterial phages and enzyme activity)
- produces the coagulating enzyme
and used for fermentation!
Pure form of enzymes extracted from calves
for cheese making
chymosin or rennin
or microbial rennets (rennin-like substitutes) or microbially produced chymosin
Recombinant chymosin
MOs genetically engineered to include the gene for producing the enzyme chymosin or rennin, which is originallyh from the stomach of calves/cows, lambs/sheeps, or goats
approved as a food additive that may be used as an enzyme
