NUFS 100 > Topic 2 > Flashcards

Topic 2 Flashcards

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1
Q

Where are food products derived from?

A

The agri-food system

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2
Q

What is the origin of most food commodities?

A

biological origin; they will be composed of plant or animal cells

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3
Q

What are food preservation and processing techniques directed by?

A

A food’s composition; constituents and their properties influence the characteristics of food products

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4
Q

What is food a mixture of?

A

CHO, protein, water, fat and miscellaneous atoms

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5
Q

What complex organic molecules does food contain?

A

C, H, N, O
- additional elements exist in the cellular structures such as salts, free ions, simple organic compounds

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6
Q

What 5 major categories of distinctly different chemical compounds describe food composition?

A
  1. lipids
  2. CHO
  3. protein
  4. water
  5. minerals/ash
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7
Q

How is proximate composition expressed?

A

As per cent composition

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8
Q

What two categories are not included in proximate composition?

A

CO2 and alcohol

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9
Q

What are 4 ways proximate composition of food is used in the food industry?

A
  1. implications for storage and shelf-life
  2. foods and beverages must conform to their legal definitions
  3. directs processing parameters (ex. butterfat content in milk)
  4. determine energy value of foods (caloric content)
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10
Q

How is proximate composition of food and feed determined?

A

Proximate analysis

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11
Q

How is proximate analysis expressed?

A

Always as “wt percentages”
- wet basis/ “as is”
- dry basis

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12
Q

What are the energy values of CHO, protein and fat?

A

CHO = 4 Kcal/g
Protein = 4 Kcal/g
Fat = 9 Kcal/g

*used for determine the energy value of foods based on proximate analysis

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13
Q

What is the energy value of 10g of fat?

A

10x9 = 90kcal

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14
Q

What is the energy value of 24g of protein?

A

24x4 = 96kcal

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15
Q

Is proximate composition the same as nutrient analysis?

A

No! But proximate composition can be calculated from nutrient analysis

ex. 7g of fat in a 21g cheese stick. Percent proximate composition of fat is 33.3

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16
Q

What are CHO a source of in the diet?

A

Energy and fibre

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17
Q

How are CHOs classified?

A

The number and type of molecules contained
1. Simple CHO
- monosaccharides
- disaccharides
2. Complex CHO
- oligosaccharides
- polysaccharides

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18
Q

What are 3 examples of monosaccharides?

A

glucose, fructose, galactose

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19
Q

What are 3 examples of disaccharides?

A
  1. sucrose = glucose + fructose
  2. lactose = glucose + galactose
  3. maltose = glucose + glucose
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20
Q

What do simple CHO vary in?

A

their properties such as sweetness, solubility, and rate of fermentation by microbes

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21
Q

What is 6 different fxns of sugars in foods?

A
  • provide sweetness and enhance flavour
  • crystallization which leads to characteristic products
  • provide body and mouthfeel (viscosity)
  • attract and hold water (hygroscopic)
  • source of food for yeast and bacteria (fermentation)
  • browning rxns
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22
Q

What are the 2 browning reactions?

A
  1. Maillard rxn
  2. Caramelization
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23
Q

What is caramelization?

A

sugar decomposition at high temperature creates brown polymers
- desirable in taste and appearance

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24
Q

What is the maillard rxn?

A

reducing sugar and amino acids react with dry heat resulting in browning accompanied by a change of flavor

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25
Why are complex CHO (polysaccharides) added to food?
polysaccharides = large chains of oligosaccharides like starch, cellulose, pectins, gums, hydrocoloids - increase dietary fibre - thicken foods - form gels - bind water - stabilize proteins
26
What are starches formed by?
Starches are a polysaccharide. Formed by two types of molecules with different properties 1. Amylose = linear chains (gel formation) 2. Amylopectin = branched chains (viscosity)
27
Cellulose
*polysaccharide - major component of plant cell walls
28
Pectin
*polysaccharide - fxns as an intercellular cement in fruits and veg - used as a gelling agent in food
29
What are dietary fibres?
CHOs not digested by humans
30
What is high fructose corn syrup?
A CHO food chemistry development derived from glucose hydrolyzed from corn starch
31
Why is high fructose corn syrup popular as a food ingredient?
inexpensive, easy to store, easy to incorporate
32
What is high fructose corn syrup listed as in Canada in the ingredient list?
glucose-fructose
33
What is the shape and fxn of protein determined by?
sequence of aa
34
What causes protein denaturation?
small changes such as a change in pH or heating
35
What are the 4 types of protein structures?
primary, secondary, tertiary, and quaternary
36
Does denaturation affect the primary structure of proteins?
no
37
What are the 4 fxns of proteins in food?
1. emulsifiers/ foaming agents - amphiphilic properties (polar and nonpolar sides) 2. colour - via the Maillard rxn 3. control texture - thickening agents - binding agents for products to hold shape - gelling agents 4. flavour generation - specific aa can contribute to food flavour, particularly a 'savoury' taste
38
Where do proteins precipitate at?
Their isoelectric point aka the pH at which there is no net charge on the protein
39
How are proteins denatured?
by bringing them to their isoelectric point
40
What are the two types of lipids in food?
Fats: solid at room temp Oils: liquid at room temp
41
What are the structure and composition of lipids in food?
- mainly triglycerides
42
What determines fat properties?
The structure of the fatty acids esterified to glycerol - length of 4-28 C atoms - saturated vs unsaturated - cis vs trans
43
What are the 5 fxns of lipids in food?
1. nutrient - source of essential fatty acids - caloric density and provide satiety 2. flavours and fat-soluble vitamins 3. contribute to texture and mouthfeel 4. heat transfer medium 5. emulsifiers - bind immiscible food components - think of natural pb (none) vs kraft pb
44
Why is heat transfer through a lipid more effective than water?
Only can get water to 100 degrees before vaporizing; oil can get much hotter.
45
What are 2 undesired rxns in lipids?
1. Hydrolytic rancidity: FFA are liberated when fat and water interact; ffa are volatile 2. Oxidative rancidity: a biochemical rxn btw fats and O2 where - long chain FA are degraded - shorted chain FA are released which are odorous
46
When are fats a source of 'off-flavours'?
- when degradation occurs (oxidation and rancidity) - antioxidants are food additives used to prevent oxidation
47
What is the focus of most processing and preservation techniques?
Water reduction or removal
48
Why is water removed during processing and preservation?
1. to inhibit microbial growth 2. prevent chemical rxns
49
What are 3 ways that water is removed from foods?
1. freezing 2. drying 3. addition of salt or sugar
50
What is the preservation approach of thermal processing (canning, pasteurization)?
- water content is not altered but high heat destroys microorganisms
51
What are the functions of water in foods?
1. flavours, vitamins, minerals may be dissolved in water 2. moisture provides lubrication for mastication and swallowing of foods 3. influences texture of fruits and veg and tenderness of meat 4. facilitates heat transfer through foods during processing 5. facilitate microbial growth 6. facilitates freeze concentration
52
Is all water in a food available for microbial growth and chemical reactions?
No! only some water is "free" - water may be tied up by chemical constituents
53
What is water activity (aw)?
- a dimensionless ratio to describe water availability in foods - aw close to 0 = little moisture available - aw close to 1 = a lot of moisture available
54
What does a higher aw indicate?
higher amount of free water to interact with microorganisms and take part in chemical and deteriorative rxns
55
What is the minimum aw for the growth of bacteria, yeasts, and molds?
bacteria = 0.85 yeasts = 0.65/0.80 molds = 0.65
56
Free water
can be extracted easily from foods by squeezing, cutting, or pressing
57
Bound water
- cannot be extracted easily - is not free to act as a solvent for salts and sugars - can be frozen only at very low temps - as the vapour pressure is negligible, the molecules cannot escape as vapour
58
How do food scientists use water activity stability maps?
Predict rxns in foods based on a food's water activity - each food has its own map
59
How is aw reduced in foods?
- addition of salts and sugars to tie up moisture - concentration, evaporation and dehydration processes
60
What are the two expressions of water in foods?
1. moisture content - describes the amount of water in proportion to the amount of the food product 2. water activity - activity of water aka ability to support microbial growth and chemical rxns
61
Do vitamins and minerals contribute to the energy content of foods?
no
62
In proximate analysis, how are vitamins and minerals represented?
ash at trace level
63
What are good sources of vitamins and minerals?
fresh and minimally processed foods - may be added to processed and refined foods
64
What are vitamins?
- chemical compounds in our food - need tiny amounts to regulate chemical rxns in bodies
65
What are vitamins divided into?
1. Fat soluble - A, D, E, K 2. Water soluble - B, C
66
What are the two 'types' of minerals?
1. macrominerals 2. trace minerals
67
What do minerals do?
- assist in the body's chemical rxns - help form body structures - important for energy transfer
68
Does food composition change when food is processed?
- Macronutrients are preserved - water may be removed or tied up - Micronutrient contents may be altered
69
What is fortification?
The process of adding back micronutrients to processed foods
70
What is food chemistry used to describe?
The chemical composition of food products - decisions of how foods are processed to extend their shelf-life, maintain quality, minimize spoilage and ensure safety are based on food composition
NUFS 100
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