# Modifications structurales des viandes au cours des transformations et conséquences sur la bioaccessibilité des solutions digestives au sein de l'aliment

Thierry Astruc

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Thierry Astruc. Modifications structurales des viandes au cours des transformations et conséquences sur la bioaccessibilité des solutions digestives au sein de l'aliment. Metaseminaire CEPIA-modaltub-2013, Mar 2013, Paris, France. 24 p. hal-01601299

HAL Id: hal-01601299

https://hal.science/hal-01601299v1

Submitted on 6 Jun 2020

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Modifications structurales des viandes au cours des
transformations et conséquences sur la bioaccessibilité des
solutions digestives au sein de l'aliment.

Thierry Astruc

Unité « Qualité des Produits Animaux » INRA de Clermont-Ferrand-Theix

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Muscle (meat) composition

75% water

19% proteins

3% lipids

& glucides, µnutriments ...

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Yellow: Muscle fibre

Red: connective tissue

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Intracellular proteins (90 %)

45 % essential aminoacids

Connective tissue (Extracellular Matrix ;10 %)

Poor Nutritional value

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What is the effect of the structural organization on the bioaccessibility of digestive enzymes to myofibrillar protein of raw and processed meat ???

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Material and Methods

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# Experimental Design

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ST

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IS

<figure><img src="image_25.png" /><figcaption>Charolais cow, 7 years old</figcaption></figure>

Pepsin 125 U/mg proteins in pH 1.8 glycine buffer, trypsin (150 U/mg proteins) and chymotrypsin (0.1 U/mg proteins) in a pH 8 glycine buffer

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# Results

## Effects of process on meat structure

(Meat storage & cooking)

## Effects of process on digestive solution bio-accessibility

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Postmortem changes during meat storage

<figure><img src="image_37.png" /><figcaption>12days postmortem (D12)</figcaption></figure>

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For each condition, measurement on
30 images, about 3000 cells

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Cooking (ST muscle)

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45 min heating
60 °C

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Fibers area

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Extracellular spaces

Heating shrinks the muscle fibers and increase the extracellular spaces

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Cooking effect on connective tissue (ST D1, 60°C)

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collagen

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laminin

Sirius red staining

Muscle fibers : yellow

Collagen : red

Immunohistofluorescence

exposure time

X 4 /raw muscle

Partial heat denaturation of proteins of the extracellular matrix that remain visible and well localized

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Technological treatments affect meat microstructure

- Extracellular matrix desorganisation
(ageing, marination, cooking)

- Increase in extracellular spaces (cooking)

Which consequences on

- digestive enzyme accessibility ?

- meat digestion ?

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Pepsin digestion of raw ST muscle

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Formation of a clearer « digestive halo » in the sample periphery

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Effect of enzymatic digestion on muscle fibers structure and ultrastructure

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Enlargement of postmortem
proteolysis break

Cooperative phenomenon?
pepsin digestion of 60°C heated ST muscle

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Swelling of the muscle fibers in the halo. Cumulative effect of low pH and pepsine digestion of extracellular matrix

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pepsin

+trypsin

+chymotrypsin

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Peptides from digestion

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Bioaccessibility and digestion depends on process (raw>60°C>90°C)
# Peptides in the digestion solution

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more aggressive is the process, lower is the digestion

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<figure><img src="image_91.png" /><figcaption>MALDI-TOF mass spectra of ST muscle after pepsin digestion (same profile for IS muscle)</figcaption></figure>

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The same peptides are released whatever the technological process
Pepsin digested raw & marinated ST muscle

<figure><img src="image_95.png" /><figcaption>Immunohistofluorescence of laminin</figcaption></figure>

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Lost of laminin antigenicity in the halo
→ alteration of ECM by the pepsin solution

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Pepsin digested raw ST muscle

Double labelling of collagen (green) and myosin (red)

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Decrease of myosin antigenicity in cells of the halo, suggesting a pepsin penetration in the intracellular compartment.

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Pepsin digested heated 60°C ST muscle

Double lebelling of collagen (green) and myosin (red)

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Large swelling of cells and decrease of myosin antigenicity in the halo

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Pepsin digested sample of marinated ST muscle

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Pepsin is detected in the halo but seems to be more located in the connective tissue

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bright spots only visible in the halo of digestion

Cy3

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Anti-rabbit

Anti-pepsin
From rabbit

pepsin

Low pepsin content

initially ?
extraction in the washing baths?
# Conclusions

## Postmortem time

D12>D1 : endogen proteolysis increased the digestive enzyme accessibility and digestion process

## Process

change the tissue structure.

But decrease

- digestive accessibility of enzymes (halo)

- level of digestion (OD 280 nm)

Swelling of cells in the halo → Access more difficult ?

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Changes in molecular structure of proteins → Recognition of cleavage sites of enzymes ?

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Perspectives

Improvement of the pepsin labelling

Labellisation of trypsin & chymotrypsin

Identification of the peptides found in the digestion solution

Chewing effect ?

Peristaltic contractions ?

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Fundings
ANR project
« pronutrial »

Conférence FSDH (New Zealand)

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Chapitre d'ouvrage FSDH (soumis)

Échanges avec M. Boland et L. Kaur
(Riddet Institute)

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Programme Hubert Curien (2013-2014)

Astruc, Santé-Loutellier, Kaur, Boland