Study On The Mechanism Of Olive Polyphenols Affecting The Retronasal Aroma Release Of Virgin Olive Oil

Virgin olive oil has received widespread attention due to its unique taste and high nutritional value.Compared with orthonasal aroma,retronasal aroma evaluation can truly restore the release of aroma during food consumption,which is an emerging flavor evaluation index in recent years.Previous studies have shown that the interaction of food components such as polyphenols with oral salivary proteins can affect the release of food retronasal aroma,but the mechanism of polyphenols affecting the retronasal aroma of virgin olive oil is rarely reported.For this reason,based on the analysis of volatile aroma compounds,polyphenol types and content of virgin olive oil,the differences in the rthonasal and retronasal aroma releases of virgin olive oil were studied.The effects of polyphenols on the aroma release of virgin olive oil were investigated,and olive polyphenols with significant effects were screened.Moreover,the interaction between these polyphenols and salivary proteins was studied,and the mechanism of olive polyphenols affecting the retronasal aroma release of virgin olive oil was clarified.The main contents are as follows:Firstly,the qualitative analysis of polyphenols in virgin olive oil were performed.The results showed that a total of 27 polyphenols were identified and 13 polyphenol monomers were quantified.The content of schizoidoids was the highest(59.15%),followed by flavonoids(20.07%),phenolic alcohols(17.26%),phenolic acids(3.08%),and lignans(0.44%).Secondly,volatile aroma compounds in virgin olive oil were characterized and quantified.The results showed that a total of 29 volatile substances were identified,including 11 aldehydes,7 esters,6 alcohols,4 ketones,and 1 acid.The content of aldehydes(48.32%)was the highest,followed by esters(36.07%),alcohols(11.88%),ketones(3.61%)and acids(0.12%).In addition,by comparing the aroma release of the orthonasal and retronasal route,it was found that the amount of aroma released in each process of the retronasal route was significantly lower than that of the orthonasal route(p<0.05).The amount of retronasal aroma release depended on the number of swallows,and the aroma compounds were slowly released along with the swallowing process,indicating that the retronasal route had a delayed effect.The release of ketones in the retronasal route increased significantly with the increase of polyphenol content(p<0.05).The release of hexanal only increased in the first two stages of the retronasal route with the olive polyphenol content,while the retronasal aroma release of heptanal did not change significantly(p>0.05).Ester aroma compounds were significantly reduced in the last two stages of the retronasal route(p<0.05).The olive polyphenol content had a significant correlation with the release of aroma compounds by the retronasal route,which may be due to the interaction of polyphenols and saliva protein.Therefore,the interaction between olive polyphenols and salivary proteins was investigated.Finally,the interaction mechanism between tyrosol/hydroxytyrosol/oleuropein and mucin/α-amylase was examined by the fluorescence quenching spectroscopy,synchronous fluorescence spectroscopy,UV-Vis absorption spectroscopy,circular dichroism spectroscopy,Fourier transform infrared spectroscopy and molecular docking techniques.The results showed that the static quenching was the main quenching mode between mucin/α-amylase and tyrosol/hydroxytyrosol/oleuropein.Moreover,the van der Waals forces and hydrogen bonds were the main driving force of olive polyphenol-protein complexes.After binding to three olive polyphenols,the conformation of mucin was changed,but that of α-amylase was unchanged.In addition,molecular docking results showed that olive polyphenols had stronger binding effects to mucin or α-amylase than aroma compounds.Therefore,polyphenols have more competitive advantages in combination with saliva protein.Thus,the aroma compounds that bound to the saliva protein were released.As mentioned above,it was found that the amount of aroma released by the orthonasal route was significantly higher than that by the retronasal route.And olive polyphenols have different effects on the release of different kinds of aroma compounds in the retronasal route.The differences in aroma release through the retronasal route were caused by the interaction of polyphenols with saliva proteins.This subject provides a basis for the analysis of the retronasal aroma of virgin olive oil.