Processing impacting starches, proteins and lipids

Underlying mechanisms how pelletign can influence nutritional value are multiple

Feed

• Pellet quality (fines)

• Particle size

• Molecular conformation - starch

Animal

• Feed intake

• Digestive functioning

Starch

Types of glucose polymers

• Amylopecting, highly branched

• Amylose, unbranched

Variability starch sources

• Amylopecting and amylose (20-30% amylose)

  • Alternating crystalline and amorphous regions (100-500 nm) and lamellae (9-11 nm)

Starch - variability starch sources

Size, shape, pores, crystalline type, crystalline amount, amylose content, amylopectine sidechain lenght

Starch gelatinisation

Swelling and rupture of starch granules, loss of crystallinity and changed molecular organization

Process of breaking odwn of intermolecular bonds of starch molecules in the presence of water and heat, allowing the hydrogen bonding sites (the hydroxyl hydrogen and oxygen) to engage more water

With higher moisture content, the structure is completely destroyed at a relativley low temperature

Water acts as a plasticizer. When water is scarce, the starch crystals are more stable, shigitng the gelatinisation zone to much higher tempartures and making the process less uniform

Gelatinisation temperature

• Excess water: 50-70 degrees

• <35 WATER: >100 degrees

• Ratio of 0.3 water: 1 starch as a prequirisute to initiate starch gelatinisation during heating

• Higher amylose, in general more reistant to gelatinisation

  • Starch molecules more available for a-amylase → starch digestion facilitated

Starch retrogradation

Cooling

• Gelatinized starch molecules re-associate into partially ordered structures )(recrystallization or retrogradation)

Resistant starch - types

1: physically inaccessible

2: native (resistant from origin)

3: retrograded, by processing

4: chemically modified

Starch granules contain

Amylopectin and amylose

Crystalline and amorphous regions

Gelatinisation (hydrothermal treatments, shear)

Swelling and rupture of starch granules, loss of crystallinity and changed molecular organization

hydration influences gelatinisation temperature

Recrystallization or retrogradtion (cooling)

re-association or starch moleules into partially ordered structures; resistant to digestion and fermentable

Starch gelatinisation - availbility of starch

Processing and nutritional value starch

Processing and starch gelatinisation

• pelleting small impact

• Extrusion larger impact

Gelatinisation and digestibility

• Starch gelatinisation facilitates digestion

  • Kinetics

  • Digestbility not evident in growing pigs

  • Digestibility potentially evident for low a-amylase animals

• Correlation SGD: Starch digeston in growing pigs is poor

Protein denaturation

Raw materials contain various proteins

Each proteins has a specific denaturation temperature

Amino acids

General structure

Side-chain variability

• Electric charge

• Hydrophobicity

• Polarity

Basic, hydrophilic, acidicP

Protein structure

Protein folding

Protein folding - type of bonds

Bonds and interactions within and between proteins impact thermal stability

Protein denaturation

Stability differs aong proteins

• Internal and external bonds and interactions

Factors impacitng denaturation

• Tmperature

• Moisture levels

• Salt, urea, acid or base

1. reversibile breakage H and VdW interactions

2. Irreversible breakage/formation covalent bodns

Changes intramoleucular interactiosn

Agglomeration and nutritional value

Variable impact of pelleting

Confounded with pelleting SBM protease inhibitors

Denaturation of proteins via processing seems not essential for digestion, at least in vitro

protease inhibitors decrease digestibility

• denaturation of ANF-proteins via processing is important for digestion

  • modifying proteins to increase nutritoinal value in ruminants

Protein aggregation

Denaturation changes intermolecular interactions

• disscociation subunits

• Reassociation of partially unfolded molecules (aggregation)

  • electrostatic interactions

  • hydrophobic interactions

  • new s-s bonds (also with pelleting)

• aggregates can be soluble or insoluble

structural proteins

cross=links between peptides for stability

• difficult to digest in native form

  • extensive treatment (heat, moisture)

Proteins

amono acids form internal and external interactions and bonds to give stability/functionality

stability linked to intensity of processing required to change protein conformation

protein denaturation - summary

hydrothermal treatments, shear, chemcial

hydration influences denaturaiton temperature

may inactive protease inhibitors

protein aggregation - summary

can follow denaturion, have specific properties

impacts digestibility

Processing impacting amino acids

maillard reaction

• a complex non-enzymatic browning process that occurs when amino acids (the building blocks of proteins) interact with reducing sugars under heat.

oxidation

breaking down amino acids for metabolic energy or modifying their structures through chemical reactions.

racemization

• time-dependent chemical process where living L-amino acids spontaneously convert into their mirror-image D-forms

Processing and lipids

isomerisation

hydrogenation

oxidation

cross-linking

lipids-protein complexes

• especially FFA and polar lipids with AA of proteins

lipid-starch complexes, not very common, well digested

processing and biochemistry summary

• changes in conformation

gelatinisation, retrogradation, denaturation, renaturation, isomerisation, oxidation

processing and biochemistry summary

• breaking bodns

gelatinisation, denaturation, caramelisation, maillard reaction

processing and biochemistry summary

• forming bonds

denaturation, cross-linking, aggregation, maillard reaction, hydrogenation, oxidation

processing and biochemistry summary

• changes in confomration, stereospecificty

racemization (isomerisation)

processing impacts nutritional value

factors temperature, hydration, shear/pressure

bond strenght and reactivity

distinguishing between mechanisms is dfifucult

• feed and animal

feed factors

• physical properties and unlocking nutrients

  • molecule conformation

    • anti-nutritional factors

animal factosr

• feed intake, selection and wastage

• digestive functioning and adaptations