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Basic Food Science > Food Chemistry > Flashcards

Food Chemistry Flashcards

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1
Q

What is water activity

A

Aw is the water activity is a term that relates to the ability of a microbe to grow in a particular environment

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2
Q

Moisture sorption isotherm

A

Moisture sorption isotherm is used to determine relationship between water content & water activity

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3
Q

Water-holding capacity

A

Water-holding capacity (WHC) results from the physical entrapment of water within a food matrix that restrict flow but no other physical properties of water

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4
Q

How are carbohydrates bonded

A

Glycosylic bonds

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5
Q

Retrogradation

A

Retrogradation is the crystallization of starch molecules such that they begin to separate from other molecules present in the product

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6
Q

How are digestible and non-digestible carbohydrates differentiated

A

Recognition

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7
Q

Is glucose an aldehyde or ketone

A

aldehyde

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8
Q

What are reducing sugars

A

Carbohydrates that are aldehydes are reducing sugars and can react with amino group of protein / amino acids i.e. Maillard reaction

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9
Q

Why are carbohydrates soluble

A

Prescence of oh group

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10
Q

What is tollens reagent used for

A

to identify reducing sugars/ aldehydes

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11
Q

What are lipids

A

Soluble in organic solvents but not water

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12
Q

3 main groups of lipids

A

triglycerides, sterols, phospholipids

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13
Q

Triglycerides

A

3 fatty acids side chain

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14
Q

Phospholipids

A

1 polar head with 2 fatty acid chains

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15
Q

Sterols

A

ring structure but does not contain fatty acids

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16
Q

What are Saturated fatty acids

A

They contain no c-c double bonds

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17
Q

What can lipids act as

A

antioxidants & pro-vitamins

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18
Q

What are trans fatty acids at room temperature

A

Solid

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19
Q

Saturated fatty acids are _ are room temperature

A

solid

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20
Q

Lipid hydrolysis

A

Lipid hydrolysis involves separation of a fatty acid from the glycerol backbone or phospholipid
I produces a free fatty acid & glycerol
If the free fatty acid is short-chained, it will be volatile and contribute to the odor of the food (Hydrolytic rancidity)

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21
Q

Lipid oxidation

A

Lipid oxidation is a reaction of lipids with oxygen that proceeds through a free radical mechanism
Free radical consist of carbon atom with an extra electron resulting from removal of hydrogen atom allowing oxygen to attach to the free electron resulting in lipid hydroperoxide
It can generate volatile compounds that have an off-flavor
Saturated fatty acids are unable to undergo lipid peroxidation due to lack of double bonds and they tend to be more stable

22
Q

What do antioxidants do

A

Antioxidants inhibit or retard oxidation through one or more mechanisms

23
Q

Why does trans fatty acids have better van der Waals interactions

A

Saturated fatty acids tend to have stronger van der Waals interactions with other saturated fatty acids because they can stack together and form a repeating structure, very similar to a crystalline structure

24
Q

Why dies cis fatty acids have weaker van der waals interactions

A

Cis double bonds form a kink in fatty acids which interfere with stacking & interactions causing weaker Van Der Walls interactions causing it to be liquid at room temperature

25
Q

What can phospholipids be used as

A

emulsifiers in food and water

26
Q

What are proteins

A

sequence of amino acids linked by peptide bonds

27
Q

Where does the hydrophilic side chain fold to

A

Hydrophilic side chain tend to be on the surface exposed to aqueous environment

28
Q

Where does the hydrophobic side chain fold to

A

Hydrophobic side chain fold towards the core of the protein

29
Q

What are enzymes

A

Proteins which catalyze chemical reactions

30
Q

What does blanching do to enzymes

A

Blanching can denature enzymes to prevent enzymatic reactions in fruits & vegetables

31
Q

What does heating do to enzymes

A

Heating will cause the enzyme to unfold and disrupt its structure (denaturation)

32
Q

Cellular compartmentation

A

Cellular compartmentation is to control enzyme reaction in plant & animal tissue

33
Q

What are enzymes affected by

A

It is affected by pH, moisture content of food, storage temperature, presence of oxygen & carbon dioxide & light

34
Q

What are alkaloids

A

Alkaloids are naturally occurring alkaline organic compounds which contain nitrogen atom(s) in their structures

35
Q

What do sequestrants or chelating agent do

A

Sequestrants or chelating agents bind metal ions preventing them from oxidizing fats

36
Q

To participate in crosslinking what is needed

A

Multivalent cations

37
Q

What are the properties of whey protein

A

Whey proteins are sensitive to heat and will unfold to expose their hydrophobic surfaces which will interact with each other to form a gel

38
Q

What are Cassin proteins

A

Cassin proteins are heat stable but will coagulate in acidic pH as casein proteins are negatively charged. In acidic pH, the proteins will become neutral & coagulate due to hydrophobic interaction

39
Q

How is a gel formed

A

A gel is formed when polymers interact and form cross link

40
Q

What is a sol

A

a sol is when a solid is dispersed in liquid

41
Q

what is a gel

A

a gel is when a solid is dispersed in liquid

42
Q

What is a emulsion

A

an emulsion is when liquid is dispersed in liquid

43
Q

What is a foam

A

a foam is when air is dispersed in liquid

44
Q

What is a colloidal system

A

Particles dispersed in a medium that are suspended that is large enough to scatter light.

45
Q

What do carbohydrates do in a colloidal system

A

They are hydrolysed and interact with water. When cooled it will form a gel or a vicious paste

46
Q

What does high HLB indicate

A

The emulsifier is more soluble in water in oil emulsion

47
Q

What does cartorenoid do

A

It will bound to protein to give food its pigment

48
Q

What happens in the Maillard reaction

A

pyrazine compounds is formed, It contributes to the roasted flavor & aroma of foods

49
Q

what is enzymatic browning catalysed by the enzyme polyphenol oxidase

A

This enzyme catalyses the oxidation and polymerisation of polyphenols present in fruits and vegetables

50
Q

Are naturally occurring pigments more or less shelf stable

A

Less shelf stable

51
Q

How is spoilage prevented

A

Antioxidants are added to oil to prevent spoilage
Oxidation is catalyzed by transition metals, adding sequestrants can retard oxidation
Additives that slow down or prevent growth of microorganisms are preservative

52
Q

What are natural additives

A

Additives derived from natural food sources

Basic Food Science (5 decks)

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