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FOOD2000 > Grains > Flashcards

Grains Flashcards

1
Q

Why do we need to measure the quality of grains?

A

Rice: Because different consumers require different types.

Wheat because it is used in so many food products.

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2
Q

Gelatinisation temperature

A

Temperature in cooking in which starch crystals begin to break down and allow water into the grain. non-reversible process. Key property of Amylopectin in Grain.

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3
Q

What are the main quality features for rice?

A

Determined mostly by starch
Amylose affects the stickiness and firmness of the cooked grain.
Amylopectin structure affects the gelatinisation temperature

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4
Q

What are the main quality features for wheat?

A

Protein content

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5
Q

Which feature of amylose leads to the increased intensity of blue and why?

A

Bonding with Iodine.

The greater the length of amylose chain helix leads to a greater intensity of blue.
Amylose is a chain of glucose molecules linked by alpha 1-4 bonds.

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6
Q

What part of the Differential Scanning Calorimeter (DSC) endotherm gives the value of GT and why?

A

The apex of the curve is the measure of gelatinisation Temperature- cooking can happen after the starch unravels- after the apex.
Area under the curve is the energy required to melt the starch.

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7
Q

When starch is cooled, what are the two processes that occur and what does this tell us in terms of the macromolecules?

A

Aggregation and Retrogradation (realign to form firmer texture- hardening of the gel).
Syneresis- excluding water

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8
Q

What are the direct features of the RVA curve? What are the derived ones? What do these tell us about the grain?

A

Pasting temperature
Peak viscosity- tell us the highest viscosity during heating- balance between swelling and rigidity assos. final product quality

Trough viscosity- measuring of weakening and disruption of granules due to heating and shearing.

Final Viscosity- ability to form viscous past or gel after cooking and cooling– product texture.

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9
Q

Which are the major grains

A

Rice, wheat, Maize and Barley –> get diverse range of products

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10
Q

Minor grains

A

oats, Buckwheat, sorghum, rye, spelt, quinoa, teff

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11
Q

What is the most important thing for wheat products

A

protein content. breads, pasta, cakes and biscuits have all different protein content

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12
Q

End us of Barley

A

Beer- barley grains are germinated in the process of malting.

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13
Q

Starch structure differs on several organisational levels. what are the organisational levels of Starch?

A
  1. Amylose (long chain- no branches) and amylopectin (huge, short chains with lots of branching)- has crystaline lamella (short chains that all line up) and amorphous lamella (bits with nothing).
  2. Blocklets- amylose surrounds multiple amylopectins (bond together though the cystaline lamella)
  3. semi-crystalline rings formed by lined up blocklets
  4. Granules
  5. compound granules (oats and rice)
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14
Q

How can starch structure be varied

A
  1. sizes of granules
  2. dif ratios of A and B granules in wheat, barley, rye
  3. different number of compound granules (oats and rice)
  4. deeper levels of structure
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15
Q

What are starch molecules made up of

A

chains of glucose molecules. 6 C.

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16
Q

Alpha 1-4 glucose linkages lead to

A

straight chains

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17
Q

Alpha 1-4 glucose linkages lead to

A

branchpoints

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18
Q 
Amylose 
structure 
bonds 
max MW
effect on structure
A

long straight chain
alpha 1-4 linkages
10^5
hardness, stickiness and retrogradation

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19
Q

Are amylose chains necessary to the formation of a starch granule.

A

No

amylopectin is essential.

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20
Q

Amylopectin

A

highly branched molecule
alpha 1-4 and alpha 1-6 bonds
10^8 9much bigger then amylose)
responsible for Tg, GT and swelling

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21
Q

What is the result of a mixture of long and short amylopectin chains in a distribution

A

Results in increased weakness
decreased strength
Decreases temperature to melt
cook at lower temperatures.

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22
Q

Glass Transition, Tg

A

first stage of melting.
reversible
used to make crunchy and crispy foods

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23
Q

Glass Transition, Tg

A

first stage of melting.
reversible
used to make crunchy and crispy foods
function of chain lengths

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24
Q

which is reversible Tg or GT

A

Tg

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25
Q

why is Tg reversible

A

because it involves the melting of starch- which can then reset. Recrystallises.

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26
Q

Gelatinisation Temperature, GT

A

Second stage of melting
irreversible
indicates cooking time

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27
Q

what will cause a lower cooking time. long or short chain lengths

A

A distribution of long and short (the greater short) will result in weaker clusters-> shorter cooking time.

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28
Q

what causes different chain lengths

A

Different enzymes.

a lack of starch synthaseIIa would result in less enzymatic activity–> shorter chains

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29
Q

function of Starch syntheses

A

Make chains longer. Each synthase makes a certain chain length

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30
Q

Function of starch branching enzymes

A

create branches by moving a part of the chain and reattaching it somewhere else

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31
Q

function of debranching enzymes

A

Trims

32
Q

What does a mutation in SSIIa (rice) result in

A

more short chains in cluster –> softer texture and lower GT

shorter cooking time

33
Q

What does a mutation in SSIIa (rice) result in (natural modification)

A

more short chains in cluster –> softer texture and lower GT

shorter cooking time

34
Q

Result of silencing SSIIa in wheat (done by genetic modification)

A

Loss of short and second set of long

low GT and poor bread qualities

35
Q

The natural mutation to BEIIb in rice and wheat results in

A 
Leads to loss of long chains, much less diverse CLD. 
high GT (long cook time- unfavourable) , cooks very very hard, no swelling
high RS, low GI -- taste terrible.
36
Q

Three ways to change the properties of starch

A
  1. chemical modification

2. genetic modification 3. change to the physical properties

37
Q

Chemical modification techniques examples

A

lots of different

  1. Acid modification- acid cuts the starch molecules into smaller size –> less viscosity, wet starch upon leaving to be cooled, opaque gel shall be obtained.
  2. distarch phosphate by POCL3- creates bond between starch molecules –> makes the gel tougher and more resistant to heat and shear.
38
Q

What, in the gut of humans, digests starch

A

salivary amylase

39
Q

Why can we only digest starch and not other CHO like cellulose, callose, etc?

A

Starch is made up of alpha 1-4 and alpha 1-6 bonds which can be digested by salivary amylase. The other CHO are beta bonded and we lack the enzyme required to break the beta bonds.

40
Q

What are proteins

A

made up from 20 Amino acids

made up of an amino acid a carboxyl group and an R group (characterises the AA)

41
Q

Draw a protein

A

amino group–alpha C (– R group)– carboxyl group

42
Q

Levels of structure of a protein

A

primary structure- sequence of a chain of amino acids
secondary structure- hydrogen bonding of the prptide backbone causes the AA to fold into a repeating pattern
tertiary structure- 3 dimensional folding pattern due to side chain interactions
quaternary- protein consisting of more then one amino acid chain

43
Q

What are the 9 essential AA

A

His, ILe, Leu, Lys, Met, Phe, Thr, Trp, Val.

44
Q

what determines the ‘quality of the protein’

A

the amino acids in the protein

45
Q

What are good sources of Histidine

A

Soy protein, eggs, parmesan, sesame, peanuts

46
Q

What are good sources of Isoleucine

A

Eggs, soy protein and tofu, whitefish, pork and parmesan

47
Q

Leucine

A

eggs, soy protein, whitefish, parmesan, sesame

48
Q

What are good sources of Lysine

A

Eggs, Soy proteins, whitefish, parmesan and smelts

49
Q

What are good sources of Methionine

A

Eggs, whitefish, sesame, mustard seeds, peanuts

50
Q

What are good sources of Cysteine

A

Eggs, soy proteins, sesame, mustard seeds, peanuts

51
Q

What are good sources of Phenylalanine

A

Eggs, Soy proteins, peanuts, sesame and whitefish

52
Q

What are good sources of Tyrosine

A

Soy proteins, eggs, parmesan, peanuts, sesame

53
Q

What are good sources of Tryptophan

A

soy protein, sesame, eggs, winged beans, chia seeds

54
Q

What are good sources of valine

A

eggs, soy protein, parmesan, sesame and beef

55
Q

What are good sources of valine

A

eggs, soy protein, parmesan, sesame and beef

56
Q

proteins in a storage grain are called

A

storage proteins

57
Q

AA in cereal proteins are generally low in

A

lysine

58
Q

What are the four classes of storage proteins in cereal grains

A
  1. Albumins
  2. Globulins
  3. Prolamin
  4. Glutelins
    These classes in all cereal grains, but go under differnt names
59
Q

Lysine content is highest in the grain?

A

Rye
high levels of albumins and globulins
(prolamins= secalins)

60
Q

Main proteins in Barley

A

prolamins and gluteins

fermantable sugars are higher with low protein

61
Q

Which is the highest protein cereal

A

Oats

most nutritionally balanced

62
Q

main protein in wheat

A

Gluten (glutenin +gliadin (prolamin))

63
Q

How is gluten formed

A

when two classes of water-insoluble proteins in wheat flour (glutenin and gliadin ) are hydrated with water and mixed (kneading)

only dough can contain gluten

64
Q

How is gluten formed

A

when two classes of water-insoluble proteins in wheat flour (glutenin and gliadin ) are hydrated with water and mixed (kneading)

only dough can contain gluten

65
Q

What properties does gluten give bread

A

its viscoelastic properties by forming a network

66
Q

what is the major storage protein of the rice grain

A

Glutelin (oryzenin)

67
Q

what is the importance of proteins in rice

A

they stop it from breaking. broken rice is not good- strach falls out the broken end and forms a glue over the cooked rice.

68
Q

what colour is a rice high in protein

A

yellow

69
Q

Retrogradation

A

The hardening of rice after it has been cooked then put in the fridge. Proteins help strengthen the network that forms on cooking and cooling.

70
Q

where are storage proteins found in grains

A

in the endosperm.

71
Q

What is the definition of whole grain? Think of two examples of different whole grain foods

A

Whole grain foods still have the bran layer surrounding the white endosperm.

72
Q

In terms of resistant starch or dietary fibre, what is the nutritional problem with the definition of whole grain?

A

Whole grain doesn’t lead to fermentation in the gut- therefore don’t get the benefits. (bran is detached from the grain)

73
Q

What is the benefit of fermenting starch in our large intestine?

A

produces short chain fatty acids, like butyrate that does a lot of good. (e.g. decreased AP, altered gut microbiota)

74
Q

How many types of resistant starch are there?

A

There are 5 types.

75
Q

What other carbohydrates do we eat that we need to ferment? Why do we need to ferment them?

A

cellulose, arabinoxylans, beta glucans, and callose. They have beta bonds, so we can’t digest them.

76
Q

What is the major problem with storing whole grain foods?

A

short shelf life due to the fatty acids oxidising into volatile compounds. The bran contains high levels of FA. volatile compounds can have an unpleasant aroma

77
Q

What type of compounds lead to rancid aromas? What is the chemical source of those compounds?

A

Oxidation of fatty acids leads to aldehydes and ketones that are volatile and have unpleasant aromas.

FOOD2000 (5 decks)

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