Plant Proteins Flashcards
What are the two proteins in the processing industry?
- concentrate: >50% protein
- isolate: >80% protein
Benefits of plant proteins to replace animal meat
- healthy (sometimes)
- sustainable and ensure long term food stability
Comparing protein content of the different grains
- Cereals (wheat 8-15% and oat 13%)
- Oilseeds (soybean 40% and flax 25%)
- Pulse grains (25-30%)
Amino acid composition and sequence
- The amino acid composition determines the nutritional quality
- sequence determines the physiochemical property of the protein.
nine essential AAs
- phenylalanine
- valine
- threonine
- ryptophan
- isoleucine
- methionine
- leucine
- histidine
- lysine
AAs additionally required by infants and growing children.
- Cysteine (or sulphur-containing amino acids),
- tyrosine (or aromatic amino acids)
- histidine
- arginine
conditionally essential AAs
not normally required in the diet, but must be supplied exogenously to specific populations that do not synthesize it in adequate amounts.
* arginine
* cysteine
* glycine
* glutamine
* histidine
* proline
* serine
* tyrosine
Functional groups in proteins:
- OH
- COOH
- NH2
- SH
- Alkyl groups
Major bonds in the protein tertiary structures.
- Hydrogen bond, (OH and OH; OH and COOH)
- Ionic interaction (NH3+ and COO-)
- Hydrophobic interaction (between alkyl groups)
- Di-sulfide bond (SH and SH)
Major bond in wheat protein
Di-sulfide bond (SH and SH) between cysteines
* helps produce gluten network in brad making
Major bond in tofu protein
ionic interactions (CaCl2)
What composes gluten in wheat?
- gliadin: intramolecular
- glutenin: networking
How does the gluten network form?
gentle kneeding (water +dough) causing interchain interaction between the glutenin molecules (quaternary)
AA acid profile of cereal proteins
- Lack in nutritionally important amino acids such as lysine, tryptophane, methionine.
- Generally high in aspartic acid, glutamic acid, proline, alanine and leucine.
- Lysine is high in oat and rye than any other cereals
- High lysine corn is available; high feed value.
AA profiel of oilseed proteins
- When compared to cereals, oilseeds are high in lysine (3-4%).
- Generally very high in aspartic acid, glutamic acid and arginine.
- Generally high in serine, proline, glycine, alanine and leucine.
- Low in tryptophane.
What lowers plant protein bioavailability?
Cross linked with phytic acid, tannins, lignins etc. making digestion and bioavailability lower
DIAAS
digestible indispensable amino acid score
* egg is golden standar
* ratio of the digestible amino acid content in the food (mg/g of protein) to the same amino acid in a reference pattern taken from age-specific amino acid requirements.
PDCAAS
protein digested corrected amino acid score
* evaluates a food’s protein quality. It compares amino acid composition to what our bodies require.
Protein classifications
basis of their extraction and solubility in water
* Albumin: water soluble, coagulated by heat.
* Globulin: water insoluble, soluble in dilute salt (0.5 M NaCl)
* Prolamin: soluble in 70% ethyl alcohol
* Glutelin: soluble in dilute acid (0.5 M acetic acid) or alkali
What belongs to albumins and globulins?
- Enzymes belong to this fraction
- Storage proteins of pulses, oilseeds, etc
- Concentrated in the aleurone cells, bran and germ/cotyledon
- Relatively high in lycine, methionine and tryptophan
What belongs to prolamins and glutelins?
- Storage proteins in cereals
- Limited to endosperm
- Lack in nutritionally important amino acids such as lysine, tryptophan, methionine (low feed/food quality).
Gliadin in wheat protein gluten
Do not contribute to elongation but are a part of stabilization and trapping CO2 (yeast using sugars) in compartments, holding it in, sealing it and preventing CO2 from leaking out.
* ~66%, w/w
* viscous
* sinlge unit with intra molecular disulfide bonds
glutenins in wheat protein
Joins glutenin chains by disulfide bonds forming network as it is kneaded; usually ~ 5 min is optimal kneading time for everything; chain extension occurs with the disulfide bonds which helps to form the network.
* ~33%, w/w
* elastic
* has subunits connected with inter molecular disulfide bonds
* multi-peptide unit
glutathione
Naturally present in wheat - small chain and takes place of high moelcular weight glutenin and can
terminate the chain extension. So interferes with network for ation in gluten
* Has cysteine unit and sulfide group
