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24, chemin de Borde Rouge -Auzeville - CS52627 31326 Castanet Tolosan cedex - France

Last update: May 2021

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Polyphenols, Reactivity, Process (PRP)

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Team leader: Sylvain Guyot

Permanent team members:

Researchers  and engineers:  Kevin BilletSophie Guilois, Sylvain GuyotJean-Michel Le Quéré

Technicians and assistant engineers:  Angélique Boissière, Agnès Gacel, Gildas Le Bail, Nathalie Marnet, Hélène Sotin

Thesis defended recently:

Mariana Castillo-Fraire (2020), Mélanie Millet (2018)

Context and Objectives

The main objective of the PRP team is to understand the involvement of phenolic compounds, and in particular tannins, in the elaboration of foods and beverages.

Phenolic compounds are present in almost all plants and they contribute to the defense against their aggressors. In the current context of more agroecological agriculture, their presence in cultivated plants could increase in the next few years, either by selecting varieties richer in polyphenols likely to defend themselves better without pesticides or by increasing their content, in response to aggressions.

In foods of plant origin, their presence can, depending on the compounds, be an advantage (nutritional benefits, flavor, color ...), but also sometimes a disadvantage (anti-nutritional factors vis-à-vis proteins, excessive astringency, undesired color ...). The nutritional benefits of polyphenols are mainly attributed to their antioxidant and anti-inflammatory activities which act against cardiovascular diseases and cancers or to an action on the microbiota. Their anti-nutritional impact and astringency are linked to their interactions with proteins. Their sensory contribution is diverse: some compounds have a gustatory impact linked to their perception by bitterness receptors, while others are colored by the presence of chromophores in the initial molecule or in the products formed by oxidation. Finally, phenolics can also cause technological difficulties (insolubilization of proteins, formation of cloudiness, loss of protein properties).

Even if the cider apple, because of its richness in polyphenols, is still a privileged study model, we are now approaching other plant models that correspond to questions that are increasingly present in the context of food transitions. During the extraction of plant proteins from protein crops or oilseed cakes, polyphenols bind to the proteins and modify their properties (solubility, digestibility, expansion, emulsion). We need to understand which compounds are involved and what are their interaction and reactivity mechanisms with proteins (prior oxidation or not) in order to propose innovative technological solutions.

Keywords: polyphenols, tannins, polysaccharides, proteins, nitrogen compounds, fruits, oxidation, enzymes, reactivity, interactions

Research lines

In the context of agroecological and food transitions and the development of Organic Agriculture we assume that polyphenols will have a role to play as secondary metabolites involved in the natural resistance of plants to pests. Consequently, their greater variability in tomorrow's plant production will require good control of the fate of these polyphenols during processing and storage in order to elaborate quality products, both nutritional and organoleptic, as well as a better valorization of co-products.

Our research involves biochemistry, reaction chemistry, and physical chemistry and focuses on the fate of these phenolic compounds during processing, in particular, their oxidation and the consequences on the formation of new phenolic molecules that can positively or negatively impact the quality of products. The variability of the raw material (linked to the variety and to the production conditions, in particular, Organic Agriculture and low inputs), and the transformation processes (availability of oxygen, heating...) are among the factors that most influence the polyphenolic composition of the food.

At this stage, our ambition is based on our scientific expertise in phenolic compounds and their reactivity during processing, in particular with respect to oxidation phenomena. It can be broken down into three priority research topics:

→ Polyphenolic reactivity in cider fruit juice model
→ Polyphenolic reactivity and interactions with proteins
→ Polyphenols, co-products for innovative functionalities


Methods and Equipment

  • Techniques of sample preparation, biochemistry, and chemistry applied to extractive phenolic compounds and cell wall polysaccharides
  • Techniques for measuring enzymatic activity type and polyphenoloxidase polysaccharidase
  • Separation techniques polyphenols analytical scale , semi -preparative and preparative : HPLC , UPLC , GC , CPC, low pressure chromatography
  • Detection techniques and structural characterization of phenolic compounds with or without chromatographic coupling : UV-Visible spectrometry microplate , mass spectrometry, electron impact (GC coupling), ESI- Ion Trap , ESI- triple quadrupole ESI- QTOF)
  • Manufacturing techniques of apple juice and cider : Pilot hall equipped with washers, rasps , different presses, modules filtration and centrifugation , controlled variable volume fermenters* ( *material partly owned by the ECI but PRP accessible through Nova2cidre UMT)

Most of the analytical equipment is located in the analytical platform P2M2