Pear ripeness and tissue type impact procyanidin-cell wall interactions

Area of Science:

• Food Science
• Plant Biochemistry

Background:

• Procyanidins are phenolic compounds found in fruits like pears.
• Fruit ripening involves complex biochemical changes affecting cell wall structure and composition.
• Understanding the interaction between procyanidins and cell walls is crucial for food quality and processing.

Purpose of the Study:

• To investigate the impact of pear ripening stages (ripe vs. overripe) on the association between procyanidins and cell wall material (CWM).
• To characterize the binding affinity and interaction mechanisms between procyanidins and CWM from different pear tissues.

Main Methods:

• Extraction of procyanidins and CWM from ripe and overripe pear tissues (flesh, parenchyma cells, stone cells, skin).
• Mid Infrared Spectroscopy (MIR) for discriminating cell wall-procyanidin complexes.
• UV-Vis spectrometry with Langmuir isotherm and Isothermal Titration Microcalorimetry (ITC) to characterize binding interactions.

Main Results:

• Procyanidin composition remained stable, but binding affinity to CWM varied by tissue (PC > FL > ST > SK).
• The proportion of bound procyanidins increased in overripe pears across all tissues.
• Maximal procyanidin saturation was observed in overripe flesh (FL) and stone cells (ST).
• ITC revealed hydrogen bonds and hydrophobic interactions in the association between overripe pear cell walls and procyanidins, particularly in parenchyma cells (PC).

Conclusions:

• Pear ripening significantly influences the association between procyanidins and cell wall material.
• Overripening enhances procyanidin binding to cell walls, altering fruit texture and potentially impacting phenolic compound bioavailability.
• The interaction involves hydrogen and hydrophobic forces, with tissue-specific differences in binding affinity.