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MFS Orientation > Module 9 > Flashcards

Module 9 Flashcards

1
Q

What is the meaning of ‘biotechnology’?

A
  • An umbrella term that covers a broad spectrum of tools and techniques, ranging from fermentation (bread, wine, cheese) to plant and animal breeding, cell and tissue culture, antibiotic production and genetic engineering.
  • The traits of every organism are encoded in its genetic material (DNA or RNA) which is organized into individual units called genes.
  • Genetic modification is achieved by changing the code or organization of the genetic material of an organism.
  • This includes, but is not limited to, moving a gene or genes from one organism to another (this is commonly called genetic engineering)”

Biotechnology is a term that began to be used in the 1980s and 90s, to describe the integrated use of biochemistry, microbiology and engineering sciences to utilize microorganisms and cultured animal and plant tissue cells and cell components in the production of desirable products.

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2
Q

What are the desirable products of biotechnology?

A
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3
Q

What is the basis of preservation of foods by fermentation?

A
  • Encouragement of growth and metabolism of alcohol and acid-producing microorganisms to supress the growth and metabolic activities of proteolytic and lipolytic spoilage-causing microorganisms.
  • This condition forms the basis of microbial antagonism
  • The antimicrobial agents the microbes produce act as antimicrobial agents
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4
Q

What is fermentation?

A
  • The breakdown of carbohydrates under anaerobic conditions
  • In reference to foods, they are those produced with the aid of microorganisms.

Most fermented foods are not genetically modified.

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5
Q

What are the benefits of fermentation?

A
  • Fermented foods can be more nutritious than the unfermented original material
    • For example, miso and tempeh have higher levels of B-vitamins than the soybeans that are used to produce those fermented foods.
  • Microbes also liberate nutrients from plants that are not normally digestible by humans.
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6
Q

What do acetic acid bacteria do?

A
  • Oxidize ethanol to acetic acid
  • Forms the basis for the production of vinegar
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7
Q

What are yeasts used to produce?

A
  • Used in the production of alcohol and bread
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8
Q

What are moulds used to produce?

A
  • Many foods in Asia as well as the production of well known cheeses like Roquefort, Brie, and Camembert.
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9
Q

What are the raw materials and products for LAB?

A
  • Raw materials: lactose and glucose
  • Product: lactic acid
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10
Q

What are the raw materials and products of yeasts?

A

Raw materials: glucose and other fermentable CHO
Products: ethanol

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11
Q

What are the raw materials and products of acetic acid bacteria?

A

Raw materials: ethanol
Products: acetic acid

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12
Q

What are the raw materials and products of microbial lipases?

A

Raw materials: lipids
Products: free fatty acids, aldehydes, ketones

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13
Q

What are the raw materials and products of microbial proteinases?

A

Raw materials: proteins
Products: polypeptides, peptides, free amino acids, amines (cause textural and flavour changes in food)

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14
Q

What are the raw materials and products of mould cellulases?

A

Raw materials: cellulose
Products: oligosaccharides, glucose

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15
Q

List the factors that are controlled in the production of fermented foods. [5]

A
  1. Starter cultures
  2. Formation of metabolites (e.g., acids, alcohols)
  3. Temperature
  4. Oxygen
  5. Salt
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16
Q

Describe the use of starter cultures.

A
  • Modern food fermentation (biotechnology) employs the use of microbial cultures specifically selected and maintained for the desirable trait(s): e.g. acid production; alcohol production; production of flavour compounds; production of specific enzymes; rate of growth.
  • In current food fermentation practices, the starter cultures are grown under specific conditions and the harvested cells are added in a specific proportion to the food to be fermented.
  • Cultures may be grown within the food processing plant or may be purchased as frozen or dehydrated cultures.
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17
Q

Why is temperature important in fermentation?

A
  • It is a key factor in ensuring the sequential development of desirable microorganisms during fermentation.
  • For example, the development of a typical sauerkraut flavour requires the proper succession of lactic acid bacteria starting with Leuconostoc meserenteroides (which requires cool temperatures of about 21°C) and followed in sequence by Lactobacillus cucumeris (32°C) and Lactobacillus pentoaceticus (37°C).
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18
Q

Why is salt important in food fermentation?

A
  • Salt favours growth of LAB but inhibits growth of spoilage and disease causing bacteria
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19
Q

Use the production of cheese as an example to demonstrate the technology of fermentation.

A
Note the milled curd is then salted, pressed, cured, ripened, and packaged for retail.
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20
Q

Which of the milk components are recovered in cheese?

A
  • Milk is composed of 88% water and approximately 3.3 g protein/100 g milk, with 2.7g being casein, the protein fraction involved in cheese curd formation.
  • The remainder of the protein (0.6g) is whey protein.
  • Milk fat partitions to the curd during cheesemaking.
  • Most cheeses are rich in protein, fat, calcium and phosphorus, but low in lactose content.
  • Individuals who are intolerant to lactose in foods can usually consume cheeses without experiencing gastrointestinal disturbances.
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21
Q

Describe the addition of starter culture in cheese making.

A
  • LAB is added at 1% (v/v) concentration to ensure the starter culture is present in much larger numbers than other microorganisms in the pasteurized milk.
  • This is done to ensure it becomes the dominant microbial population.
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22
Q

What are annatto and Beta-carotene used for in cheese making?

A

Colouring agent

Added after addition of starter culture

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23
Q

What is rennet used for in cheese making?

A
  • Once inoculated cheese becomes mildly acidic, rennet is added
  • The combination of acidic conditions and the enzyme rennet causes caseins in milk to coagulate and form a gel
  • The enzyme hydrolyzes a portion of the k-casein from the casein micelle, changing it from a calcium-stable to a calcium-sensitive state that leads to the formation of the coagulum with the aid of the lactic acid produced by the starter culture.
  • The whey is trapped within the 3D network created by the aggregating casein micelles and form a gel.

The commercial rennin preparation is known as “rennet”, which is obtained from the 4th stomach of the calf and contains rennin and other small amounts of other materials. Rennin (also called chymosin) is a pure enzyme.

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24
Q

What is the difference between rennet and rennin?

A
  • The commercial rennin preparation is known as “rennet”, which is obtained from the 4th stomach of the calf and contains rennin and other small amounts of other materials.
  • Rennin (also called chymosin) is a pure enzyme.

In cheese making, the enzyme hydrolyzes a portion of the k-casein from the casein micelle, changing the micelles from a calcium-stable to a calcium-sensitive state that leads to the formation of the coagulum with the aid of the lactic acid produced by the starter culture.

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25
Q

What is curd cutting?

A
  • The curd is cut into cubes to promote efficient removal of whey from the curd.
  • During this phase, the lactic acid culture continues to produce lactic acid which also aids in the expression of the whey from the casein curd by causing the aggregated micelles to aggregate even further.
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26
Q

Why is curd cooked? [2]

A

The cut curds are cooked at 38°C to (1) accelerate lactic acid production and (2) further expulse the whey from the curd.

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27
Q

What is matting and cheddaring?

A
  • The curd cubes settle and the whey is drained from the cheese vat.
  • Matting of the curd leads to the fusion of the curd pieces to form a rubbery slab.
  • This fusion is promoted by attractive interactions between the casein micelles along the curd edges.
  • During matting and cheddaring, the lactic acid bacteria continue to produce lactic acid which aids in curd fusion and shrinkage, leading to further expulsion of the whey.
  • Cheddaring involves cutting the matted curd into blocks, turning the blocks every 15 minutes, and piling the blocks on one another. This process allows the whey to be further squeezed from the curd.
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28
Q

Why is matted, cheddared curd milled and salted? [4]

A
  • to draw the whey out of the curd
  • to flavour the final cheese
  • to inhibit the growth of proteolytic and lipolytic spoilage-causing microorganisms that may be associated with the newly formed milk curd
  • to provide conditions favourable to the proteolytic action of the rennet and of the proteinases of the lactic acid starter culture during the ripening of the cheese
29
Q

Why is curd pressed after milling and salting?

A
  • The curd is pressed and hooped before curing. During curing, the curds knit together such that the curd junctions cannot be seen in a good quality Cheddar cheese.
  • If the curd has not completely knit together, the cheese will fracture along the junction lines.
  • Cheese in which the junctions are clearly visible tends to have a crumbly rather than a smooth texture.
  • During ripening, proteinases of the lactic acid bacteria and the rennet continue to hydrolyze the casein to produce peptides and free amino acids that contribute to the typical Cheddar cheese flavour.
30
Q

Describe the curing and ripening of cheese.

A
  • Complex changes occur within the ripening of cheese that leads to desirable flavours and textures of the cheese.
  • After the pressing step, the cheese is placed in a cool room for 3-4 days.
  • To prevent mould from growing on the surface of the cheese, the cheese is vacuum packed in flexible film or dipped in hot paraffin.
  • Curing and ripening take place at 2°C and 85% RH.
  • The ripening stage is continued for at least 60 days.
  • However, as you will note with different kinds of Cheddar cheese, ripening may be continued for 12 months or more if peak flavour and aroma are desired.
31
Q

Swiss cheese is characterized as a […] cheese.

A

hard-type

32
Q

Describe production of swiss cheese.

A
  • Begins like cheddar, except that a secondary starter culture Propionibacterium shermanii is added to the milk along with the LAB, which produces propionic acid (swiss taste), carbon dioxide (creates the holes), and proline (imparts sweet taste characteristic of Swiss)
33
Q

Blue-veined cheeses are […] cheeses. List the four types.

A

semi-soft
1. Blue
2. Stilton
3. Gorgonzola
4. Roquefort (from sheep’s milk)

The first 3 are from cow’s milk.

34
Q

Describe the production of blue-veined cheese.

A
  • The production procedure for the blue-veined cheeses is similar to that of Cheddar cheese except that the curd is inoculated with a mould, Penicillium roquefortii, which grows within the hooped curd producing the characteristic flavour and colour of the blue-veined cheeses.
  • After it is hooped and pressed, the cheese curd is pierced to provide channels for the oxygen, required for mould growth, to enter the cheese.
  • The blue colour is due to the mould spores that are formed during the growth of the mould along the lines where the cheese curd was pierced.
  • Penicillium roquefortii is an active producer of the enzyme lipase which breaks down the milk fat into free fatty acids, aldehydes and ketones that contribute to the sharp, distinctive flavour characteristic of the blue-veined cheeses.
34
Q

Describe the production of camembert.

A
  • The curd is produced through the use of a lactic fermentation much like that used for Cheddar cheese.
  • In this case, the surface of the pressed cheese curd is also inoculated with spores of Penicillium camembertii (or Penicillium candidum).
  • The vigorous growth of the mould leads to the formation of a layer of mycelia that forms the white, velvet-like coating on the outer layer of the cheese.
  • The mould is highly proteolytic and the mould proteinases diffuse into the cheese curd, hydrolyzing the casein into long-chain peptides which do not contribute much flavour to the cheese.
  • The hydrolysis of the casein leads to the formation of the creamy texture characteristic of a good quality Camembert cheese.
  • If the Penicillium culture is too proteolytic or if curing takes place too long, bitter-tasting short-chain peptides, free amino acids and ammonia are formed.
  • A good quality Camembert cheese has a mild flavour, is not bitter, and has a characteristic creamy texture.
  • With Camembert cheese, the mould should not contribute to the formation of mouldy flavour in the cheese; a mouldy flavour is considered a quality defect.
35
Q

What are GMOs?

A
  • Genetically modified organisms are plants, animals, or microorganisms in which the change to the heritable trait(s) of the organism by intentional manipulation.
  • Genetic modification may enable the host organism to:
    • yield the desired product (e.g., bovine chymosin produced by genetically modified bacteria), or,
    • possess the desired characteristic (e.g., tolerance to a specific herbicide in genetically modified canola plants, insect resistance in corn genetically modified to produce the insect toxin produced by Bacillus thuringensis, Bt; canola plants genetically modified to produce oil with specific compositional characteristics)
36
Q

What is recombinant chymosin?

A
  • Recent developments have enabled the transfer of the gene from calves that encodes for the enzyme chymosin to specific microorganisms selected for enzyme production.
  • The microorganisms are cultured in large fermenters and produce the chymosin which is then isolated, purified and sold to the dairy industry for cheese making.
  • Microbially produced bovine chymosin is an approved food additive in Canada.
  • Chymosin is the principle milk-clotting enzyme in bovine rennet extracts that have traditionally been used in cheese making.
37
Q

Describe genetically engineered starter cultures.

A
  • Research is also being conducted to improve the fermentative capabilities of lactic acid bacteria and other bacteria and moulds used in cheese making.
  • Some of that research involved genetic engineering where genes encoding for increased resistance to bacterial viruses (bacteriophage, a potentially serious problem in cheese making which can cause starter culture failure), improved enzymatic activity (lactose utilization; production of desirable proteinases involved in cheese ripening) are transferred into bacteria used as starter cultures.
  • Genetically improved starter cultures produced through genetic engineering must go through thorough testing and evaluation to demonstrate their safety prior to approval for their use in foods (they are classified as food additives).
38
Q

Describe packaging requirements for fermented foods.

A
  • In order to extend their shelf life, fermented foods require “additional” forms of preservation such as pasteurization and refrigeration.
  • Packaging also plays an important role as it should protect the food from re-contamination, oxidative reactions, etc.
39
Q

Which are two components that produce microbial antagonism seen in fermentation?

A

Acids and alcohols

40
Q

What is the relationship between the terms biotechnology, GMO and GE?

A

Biotechnology refers to a broad range of techniques of which GMO is one example. Within the term GMO is also more specifically the technique of GE.

41
Q

Growing bacterial cells to extract polysaccharides like xanthan gum is considered biotechnology.
True or False?

A

True.

42
Q

Using home canning methods such as making pickles by adding vinegar to cucumbers to lower the pH is considered biotechnology.
True or False?

A

False.

43
Q

Cross breeding cows to produce a cow with better milk yields is considered biotechnology.
True or False?

A

True.

44
Q

Putting genetic material from one species into another, such as the gene that makes the cow enzyme chymosin into bacterial cells is considered biotechnology.
True or False?

A

True.

45
Q

Salt is a factor in fermenting foods.
True or False?

A

True.

46
Q

Water content is a factor in fermenting foods.
True or False?

A

False.

47
Q

Oxygen is a factor in fermenting foods.
True or False?

A

True.

48
Q

Temperature is a factor in fermenting foods.
True or False?

A

True.

49
Q

Which fermented drink has an alcohol content that will prevent the growth of spoilage and disease microorganisms?

A

Vodka (20% alcohol)

Fortified wines with alcohol contents above 20% do not require further preservation treatments.

50
Q

What is the best definition of a genetically modified organism?

A

A living organism (plant, animal, microorganism) that has a trait that has been produced intentionally through manipulating genetic material (DNA).

51
Q

What are all the factors that result in the preservation of cheese over that of milk? [4]

A
  • Salting the milled cheese curd
  • Controlled growth of starter culture (temperature and volume)
  • Lactic acid produced by lactic acid bacteria
  • Absence of oxygen through vacuum sealing or wax dipping
52
Q

Sauerkraut

A

Lactic acid bacteria

53
Q

Vinegar

A

Acetic acid bacteria

54
Q

Beer

A

Yeast

55
Q

Miso

A

Mould

56
Q

Two bacterial cultures are used as the starter

A

Swiss

57
Q

Mould cultures are injected after pressing

A

Blue

58
Q

Proteinases diffuse from the surface inward softening the cheese

A

Camembert

59
Q

Cheese is coated in wax to prevent growth of aerobic microorganisms

A

Cheddar

60
Q

A starter used for Swiss, heat tolerant

A

Streptococcus thermophilus

61
Q

Causes slime rot in cabbages and a gum is extracted from it

A

Xanthamonas campestris

62
Q

Creates the white moldy crust on Camembert

A

Penicillium camembertii

63
Q

Produces proline which gives Swiss cheese its sweet flavour

A

Propionibacterium shermanii

64
Q

Streptococcus thermophilus

A

A starter used for Swiss, heat tolerant

65
Q

Xanthamonas campestris

A

Causes slime rot in cabbages and a gum is extracted from it

66
Q

Penicillium camembertii

A

Creates the white moldy crust on Camembert

67
Q

Propionibacterium shermanii

A

Produces proline which gives Swiss cheese its sweet flavour

MFS Orientation (13 decks)

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