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Nutrition Semester 1 > BMS1064: Wk8 - Proteins > Flashcards

BMS1064: Wk8 - Proteins Flashcards

1
Q

What is the difference between wholegrain and white gain flour?

A

Wholegrain - includes bran, endosperm and germ
(more fibre, healthy fat, antioxidants minerals and vitamins)

White - endosperm only (carbs + protein)
- often fortified with B1, iron and Ca
- sometimes germ/bran is added

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2
Q

What is gluten?

A

A protein complex derived from cereals such as wheat, rye, barley and oat.

FOOD SCIENCE DEFINITION
Proteinaceous material prepared as a cohesive viscoelastic by-product derived from the isolation of starch from wheat flour.

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3
Q

What is Vital Wheat Gluten? What are some pros and cons?

A

Gluten sold as a dried state.

Produced industrially from wet wheat flour - controlled drying process. retains original functional properties of wheat gluten upon rehydration.

+ Cheap, functional properties
- Low biological value (e.g. low protein), link to coeliac disease

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4
Q

Gluten has high levels of the amino acid _______ which serves as an efficient source for the synthesis of other non-essential AAs.

A

Glutamine

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5
Q

Gluten proteins are largely ___________ so lipids bind to these parts of the protein.

The lipid content in gluten can affect its _____________ properties, quality (oxidation -> shortened shelf life) and _______.

A

Hydrophobic

Functional
Flavour

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6
Q

Describe the protein structure of gluten.

A

Glutenins and Gliadins associated through disulphide bonds, H-bonds and hydrophobic interactions.
Together they provide physical properties:
- Glutenin - elasticity
- Gliadin - viscosity and extensibility

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7
Q

How does one extract gluten from flour?

A

1) Mix the flour with water to form a dough or batter.

2) The dough is allowed to rest and fully hydrated to produce gluten protein agglomerates (mass/collection).

3) The agglomerates are separated from the starch by centrifugation in decanters.

4) The final stages are drying, grinding and sieving to obtain vital wheat gluten in powder form.

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8
Q

What are the functional and sensory properties of gluten?

A
  1. Solubility and water-holding capacity - increases product yield, softness and shelf-life.
  2. Viscoelasticity - allows gas retention and controlled expansion in aerated doughs
  3. Flavour
  4. Thermosetting - provides structural rigidity and bite characteristics
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9
Q

How can we modify gluten to increase water solubility for emulsion and foam stabilization? Give pros and cons for each.

A

A. DEAMIDATION with acid or alkali treatment
+ milk/meat replacements
- no functional properties in bread doughs due to loss of H-bonds (loss of viscoelastic properties)

B. ENZYMATIC HYDROLYSIS of peptide bonds
+ peptides can form bonds - good for doughs
- bitter taste due to release of small peptides

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10
Q

How can we modify gluten using physical treatments? What new properties does these give us?

A

A. TEXTURIZATION by extrusion - produces fibrous structure (simulates meat fibres)

B. HIGH PRESSURE (increasing pressure: liquid->solid)

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11
Q

Name some uses of gluten in food

A
  • FLOUR FORTIFICATION AND BAKERY PRODUCTS- increase protein, improving nutritional and technical quality
  • BREAKFAST CEREALS - binds vitamins and minerals, provides texture and strength
  • PASTA AND NOODLES - reduces cooking loss, increases resistance to breakage, improves heat tolerance
    -PROCESSED MEAT, POULTRY AND FISH PRODUCTS - improves palatability, used as binder to improve slicing characteristics and reduce cooking losses
    -VEGETARIAN FOOD AND MEAT/CHEESE ANALOGUES - binder, fibrous, texture, eating quality
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12
Q

Vital wheat gluten is approved by ______ and applies with the ____ regulations. ________ enrichment claims are banned for food products containing gluten.

A

US FDA

WHO

Protein

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13
Q

What is coeliac disease? treatment? current research?

A

Inflammation of the small intestine due to an inappropriate immune response to wheat gluten, affecting the absorption of water and nutrients.

Only treatment (at present) is a strict diet avoiding all products containing gluten.

Current research into oral enzyme supplements designed to accelerate gastrointestinal degradation of gluten. Studies also focused on reducing gliadin immunoreactivity.

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14
Q

Protein content in meat varies with :
1.
2.
3.

A
  1. Age
  2. Breed
  3. Cut of meat
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15
Q

What are the 3 meat protein classification?

A

STROMAL PROTEINS/CONNECTIVE TISSUES (10-15%)
- collagen, elastin, reticulin

MYOFIBRILLAR PROTEINS (55%)
- actin, myosin

SARCOPLASMIC PROTEINS (30%)
- water soluble proteins: haemoglobin, myoglobin

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16
Q

What are the 3 connective tissue layers?

A

Epimysium (covers muscles)

Perimysium (covers fascicles/muscle fibre bundles)

Endomysium (covers muscle fibres)

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17
Q

Describe the structure of muscle fibres.

A
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18
Q

Describe the structure and use of collagen.

A

Collagen is a connective tissue in meat. Can be degraded to gelatin at 65-80 degrees C (thermal denaturation)

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19
Q

Describe the structure of myosin

A
20
Q

Describe the structure of actin

A
21
Q

What does the degradation of the muscle filament Desmin through aging cause?

A

An increase in water holding capacity

22
Q

Enzymes and Pigments are added to meats. What are they called? What do they cause?

A

Enzyme: Caplain
- Tenderization, flavour contribution

Pigments: Myoglobin and haemoglobin
- Responsible for colour variations in meat
(varying myoglobin concs in meat lead to their different colours)

23
Q

What are the ligands of myoglobins and their colours?ciate

A
24
Q

What is the first stage that occurs after an animal is slaughered? How long does it last? Can meat be processed during this time? What temp is it usually stored at?

A

ACIDIFICATION
0.5-24 hours.
Meat may be processed.
Meat normally stored at 10 degrees C.

25
Q

When does Rigour ortis occur? What stages occur during this time? How long does it last? Can meat be processed?

A

Occurs after Acidification.

Includes Onset, then Resolution. Conditioning stage starts part-way through Resolution.

Lasts 0.25-6 days.

Meat should not be processed.

26
Q

Conditioning coninues after _____ _______. Meat can be ______ again.

A

Rigor Mortis
Processed

27
Q

What occurs in acidification?

A

❑ Animal dies, oxygen levels fall, respiration stops
❑ ATP is generated from glycogen: anaerobic glycolysis
❑ Lactic acid accumulates and the muscle acidifies
❑ pH drops to around 5.5

Acidification depends on the animal, stress, type of
muscle, storage temperature (e.g. occurs faster at higher temp).

28
Q

How does acidification change the muscle meat biologically?

A
  1. Muscle proteins denature as pH falls.
  2. Loss of biological activity: water holding capacity (water loss from muscle fibres) and
    solubility.
  3. Light scattering properties increase.
  4. Meat changes from dark and translucent to pale and
    opaque.
29
Q

The paleness of meat is due to what? The texture of the meat is due to what?

A

Paleness -> light scattering
Texture -> water holding capacity

30
Q

What does it mean if meat is particuarly pale and soft or dark and dry?

A

Pale Soft Exudatie (PSE) - Short term stress. pH very low at time of slaughter.

Dark Firm and Dry (DFD) - long term stress. pH very high - no glycogen at time of slaughter.

31
Q

What occurs in the onset stage of Rigor Mortis?

A

❑ Glycolysis is inhibited by lack of glycogen and pH
❑ ATP falls
❑ Muscle extensibility is lost (muscle becomes rigid)

32
Q

What happens in the resolution stage of rigor mortis?

A

❑ Tenderization starts: muscles soften as myofibrils become
fragmented.
❑ Rate of tenderization depends on species and temperature

33
Q

What occurs in the conditioning stage?

A

❑ Continuation of tenderization.
❑ Calpains: flavour
❑ Better results above freezing point.

34
Q

_____________ and ____________ affect how red the meat is. This is measured by a ____________. You can also measure colour using _______ _____ or _____________.

A

Haemoglobin & Myoglobin

Spectrophotometer

Colour cards or colorimeters

35
Q

What affects the tenderness of meat?

A

Pre-slaughter factors:
- breed, age, fat, species

Post-slaughter factors:
- pH and rigor mortis
- conditioning
- cooking (collagen)
- Processing (freezing/drying)
- Artificial tenderization (beating, marinating, enzymes such as papain)

36
Q

What is used as a flavour enhancer in meat?

What causes undesirable falvours?

A

Monosodium glutamate

Bacterial spoilage and rancid fat.

37
Q

Why do we need to analyse the total protein content in food?

A
  1. To establish the value of commodities for trading purposes.
  2. To calculate nutritional content of food
  3. To assess quality of food according to safety specifications.
  4. To evaluate authenticity of food to avoid economic adulteration
38
Q

What are the two main methods used to analyse protein content in food?

What are they based on?

A

Kjeldah method
Combustion method (Dumas)

Both methods are N-based - relying on N as a marker to estimate protein content.

39
Q

Describe the Kjeldah method

A
  1. DIGESTION to convert N to ammonium sulphate.
  2. NEUTRALISATION with alkali to convert ammonium sulphate to free ammonia.
  3. DISTILLATION of ammonia into boric acid.
  4. TITRATION of excess boric acid with alkali.
40
Q

Evaluate the Kjeldah method to analyse protein content in food.

A

+ Cheap, fast, most recognised
- Safety concerns - sulfuric acid used in digestion.
- Does not distinguish protein-based N from non-protein N (sellers may adulterate food with other N components to mimick high protein content)

41
Q

Describe the Combution (Dumas) method to analyse food protein content.

A

Samples combusted in furnace (800-950 degrees C) in presence of oxygen.
[H2O, CO2, SO2, NOx and N2 formed. CO2 and SO2 removed.]

Total N2 measured by gas chromatography.
N protein conversion factors used to calculate protein content.

42
Q

Evaluate the Combustion method to analyse protein content of food.

A

+ Simple, faster, cheaper and safer than Kjeldah procedure.
- Might cause overestimation
- Cannot distinguish between protein N and non-protein N

43
Q

Melamine is a chemical compound which can be found in milk. It is high in N and so can be mistaken for protein in food analysis. What does it cause?

A

Eye, skin and respiratory irritation/harm.
Chronic exposure -> cancer/reproductive damage.

44
Q

New protein analysis methods are needed to distinguish between protein and non-protein Nitrogen. What are some examples of new methods? What is an issue with these though?

A
  1. Antibody based -ELISA
  2. Chromatographic - High Performance Liquid Chromatography (HPLC)
  3. Electrophoretic - PAGE, CE
  4. Mass Spectrometric - MS

+ can distinuish between protein and non-protein N compounds.
- Not suitable to measure total protein content.

45
Q

Which of the new protein analysis methods are fast? Which are slow? Which have the highest resolution?

A

Fast:
+ Mass spectrometry
+ Capillary electrophoresis

Slow:
- ELISA
- HPLC

Highest resolution:
+ Mass spectrometry
+ Capillary electrophoresis

  • Cost -> for all

Nutrition Semester 1 (11 decks)

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