PROTEINE ALIMENTARI

Francesco Bonomi

DeFENS - UNIMIDeFENS - UNIMI

FOOD SYSTEMS: CHALLENGES

COMPLEXITY

Intrinsic (raw materials of biological origin)

From processing (novel interactions)

HETEROGENEITY

Intrinsic (more than one ingredient!)

From processing (components differently affected)

PHYSICAL STATEPHYSICAL STATE

From frozen to piping hot

Plurality of phases

COMPONENTS OUGHT TO BE PRESENT,

EACH WITH A PROPER STRUCTURE

The case of proteins

FOOD PROTEINS: BEFORE

ABUNDANCE

Governed by genetics, epigenetics, and more…

STRUCTURE

Intrinsic (raw materials of biological origin)

From unseen/unexpected processing

FUNCTION

The good, the bad, the ugly: the case of enzymes

FOOD PROTEINS: DURINGIRREVERSIBILE COMPOSITIONAL AND RELATIONAL

CHANGES

- CHEMICAL OR ENZYMATIC MODIFICATION

- glycation & glycosylation

- oxidations- oxidations

- proteolysis

- NOVEL PROTEIN-PROTEIN COVALENT INTERACTION

- disulfide bridges

- transamination

FOOD PROTEINS: DURINGREVERSIBILE STRUCTURAL CHANGES INVOLVE

NON-COVALENT BONDS

TRANSIENT (REVERSIBLE) STRUCTURAL MODIFICATIONS

IRREVERSIBLE STRUCTURAL MODIFICATIONSIRREVERSIBLE STRUCTURAL MODIFICATIONS

Depending on the treatment nature and intensity,

and on the peculiar features of the system

native transiently modified

irreversibly unfolded

reversible irreversible

frac

tion

of th

e to

tal 0.8

1.0

Native species

Treatments of low intensity do not produce enough intermediate

PROTEINS STRUCTURAL CHANGES

time, arbitrary units

0 2 4 6 8 10

frac

tion

of th

e to

tal

0.0

0.2

0.4

0.6

0.8 Native species

intermediate

End product

frac

tion

of th

e to

tal 0.8

1.0 Native species

End

Treatments of high intensity do not allow accumulation of intermediates

PROTEINS STRUCTURAL CHANGES

time, arbitrary units

0 2 4 6 8 10

frac

tion

of th

e to

tal

0.0

0.2

0.4

0.6

0.8 End product

intermediate

1.0

Only treatments of appropriate intensity allow significant accumulation of the intermediate

PROTEINS STRUCTURAL CHANGES

time, arbitrary units

0 2 4 6 8 10

frac

tion

of th

e to

tal

0.0

0.2

0.4

0.6

0.8

Native species End product

intermediate

FOOD PROTEINS: CHALLENGES

Final products (food analyst/technologist)

much studied:

treatment “reporters”biological & sensory properties

Unfolding intermediates (the protein (bio)chemist)

poorly studied:

real “substrates”

dictate rate & extent of the various paths occurring during processing

relevant to process modeling & optimization

FOOD PROTEINS: DURING

CLASSES OF DENATURANTS (LOSS OF STRUCTURE!)

- Physical

- temperature (not “heat”!)

- pressure

- radiations

- Chemical

- pH

- solvent

- interfaces

- salts

FOOD PROTEINS: DURING

CLASSES OF DENATURANTS (LOSS OF STRUCTURE!)

- Physical

- temperature (not “heat”!)

- high pressure (> 2000 atm…)

- mechanical

- Chemical

- pH

- solvent

- interfaces

- salts

FOOD PROTEINS: DURING

DENATURANTS AT WORK

- Physical

- temperature (not “heat”!)

- pressure

COLLAGEN AND GELATIN: A PSEUDO REVERSIBLE SYSTEM

- radiations

- Chemical

- pH

- solvent

- interfaces

- salts

FOOD PROTEINS: DURING

DENATURANTS AT WORK

- Physical

- temperature (not “heat”!)

- pressure

COLLAGEN AND GELATIN: A PSEUDO REVERSIBLE SYSTEM

- radiations

- Chemical

- pH

- solvent

- interfaces

- salts

FOOD PROTEINS: DURING

DENATURANTS AT WORK

- Physical

- temperature (not “heat”!)

- pressure

COLLAGEN AND GELATIN: A PSEUDO REVERSIBLE SYSTEM

- radiations

- Chemical

- pH

- solvent

- interfaces

- salts

FOOD PROTEINS: DURING

CONTROLLED DENATURATION AT WORK

- Physical

- temperature (not “heat”!)

- high pressure

- mechanical- mechanical

- Chemical

- pH

- solvent

- interfaces

- salts

FOOD PROTEINS: DURING

CONTROLLED DENATURATION AT WORK

- Physical

- temperature (not “heat”!)

- high pressure

- mechanical

- Chemical

- pH

- solvent

- interfaces

- salts

FOOD PROTEINS: DURING

CONTROLLED DENATURATION AT WORK

- Physical

- temperature (not “heat”!)

- high pressure

- mechanical PASTAacqua

aggiunta impasto e denaturazione - mechanical

- Chemical

- pH

- solvent

- interfaces

- salts

PASTA

acqua rimossa per essiccazione

denaturazione proteine

impasto e formazione legami

cottura: assunzione di

acqua

FOOD PROTEINS: DURING

CONTROLLED DENATURATION AT WORK

- Physical

- temperature (not “heat”!)

- high pressure

- mechanicalSH

S-S

Proteine native

DENATURAZIONE E RETICOLAZIONE

- mechanical

- Chemical

- pH

- solvent

- interfaces

- salts

S-S

SH

S-S

Reticolo interproteico

Legami disolfuro:

intraproteina

interproteina

Legami idrofobici

intraproteina

interproteina

impasto e formazione

legami

cottura, passaggio di acqua da

proteine ad amidostaling, phase 1

PANE

cessione di acqua a proteine:

rammollimento

staling, phase 2

perdita complessiva di

acqua: raffermimento

FOOD PROTEINS: DURING

CONTROLLED DENATURATION AT WORK

- Physical

- temperature (not “heat”!)

- high pressure

- mechanical

proteina nativa: in nero le regioni

idrofobiche, in chiaro le regioni polari

denaturazione interfacciale diretta

goccia di grasso(non in scala)

- mechanical

- Chemical

- pH

- solvent

- interfaces, oil

- salts

interfacciale diretta(con idrocarburi o

solventi)denaturazione

meccanica

interazione di superficie

emulsione di grasso

in acqua

FOOD PROTEINS: DURING

CONTROLLED DENATURATION AT WORK

- Physical

- temperature (not “heat”!)

- high pressure

- mechanicalpunto nodale

lamella

- mechanical

- Chemical

- pH

- solvent

- interfaces, gas

- salts scorrimento dell'acqua verso i punti nodali

fuoriuscita di gasevaporazione

dell'acqua dalle lamelle

aria, anidride

carbonica

FOOD PROTEINS: DURING

CONTROLLED DENATURATION AT WORK

- Physical

- temperature (not “heat”!)

- high pressure

- mechanical- mechanical

- Chemical

- pH

- solvent

- interfaces, solid

- salts

FOOD PROTEINS: DURING

CONTROLLED DENATURATION AT WORK

- Physical

- temperature (not “heat”!)

- high pressure

- mechanical- mechanical

- Chemical

- pH

- solvent

- interfaces, solid

- salts

FOOD PROTEINS: DURING

CONTROLLED DENATURATION AT WORK

- Physical

- temperature (not “heat”!)

- high pressure

- mechanical- mechanical

- Chemical

- pH

- solvent

- interfaces, solid

- salts

FOOD PROTEINS: DURING

CONTROLLED DENATURATION AT WORK

- Physical

- temperature (not “heat”!)

- high pressure

- mechanical- mechanical

- Chemical

- pH

- solvent

- interfaces, solid

- salts

Controlling the polymers formation

Covalent and non-covalent aggregation mechanisms for chaotrope-treated BLG

From low tide…

… to ebb tide

OPTICAL SPECTROSCOPIES

Infrared spectroscopy

Circular dichroism

Structural features of food proteins

Circular dichroism

Intrinsic

Binding of ligands

Fluorescence

Intrinsic (reporter amino acids)

Extrinsic (binding of ligands/probes)

“MAGNETIC” SPECTROSCOPIES

NMR

homonuclear

Structural features of food proteins

homonuclear

heteronuclear

relaxometry (and the like)

imaging

EPR