Effect of abiotic stress factors on polyphenolic content in the skin and flesh of pear by UPLC-PDA-Q/TOF-MS

Abstract Growing social interest in foods with high biological quality results in the need to look for possibilities of increasing the biological quality of food products. The aim of this research was an attempt to estimate the increase of polyphenolic compounds (by UPLC-PDA-MS/MS) in the flesh and skin of pear under the influence of stress elicitors such as UVC radiation, L-EMF, H-EMF and US with various exposure times. The applied stress factors differentiated the content of phenolic acids, flavan-3-ols and flavonols both in flesh and in skin. In all cases, pear skin demonstrated a decrease in the sum of polyphenolic compounds; however, when it comes to flavan-3-ols and procyanidins, the concentration of the compounds increased in two cases: after a 30-min exposure to L-EMF (+ 18%) and after a 5-min exposure to H-EMF (+ 20%). Following a 30-min flesh exposure to US, the determined sum of polyphenolic compounds was + 28% higher than in the control sample. It was observed that the level of flavan-3-ols and procyanidins in the flesh increased after a 60-min exposure to UVC radiation and low-frequency and high-frequency electromagnetic fields, and after a 20-min and 30-min exposure to ultrasounds. The presence of flavonols was only observed in pear skin. The research results show that it is possible to produce juice with a higher content of polyphenolic compounds, because juice is obtained mainly from the flesh; however, there is a need for further research to confirm the observed tendencies in the changes of polyphenolic compounds in fractions of pears.