Chilling-related browning of ‘Wonhwang’ pear cortex is associated with the alteration of minerals and metabolism

Abstract

‘Wonhwang’ pear (Pyrus pyrifolia Nakai) is affected by a wide range of physiological disorders, especially internal browning (cortex browning) during long-term cold storage and subsequent shelf life. Postharvest fruit quality and metabolic changes of many Asian pears (P. pyrifolia) are well characterized, but little is known about the minerals and metabolites associated with internal browning induction and development in ‘Wonhwang’ pear during cold storage. The present study compares minerals and metabolites in cortex tissue of healthy fruit as well as symptomatic (browned) and sound tissues from fruit with internal browning that developed during long-term cold storage. P, K, Ca, sorbitol, shikimic acid, palmitic acid (C16:0), linoleic acid (C18:2), α-linolenic acid (C18:3), methionine, 1-hexenol, and (Z)-3-hexenal were lower in browned tissue than in healthy and sound tissues. In contrast, levels of glucose, fructose, fumaric acid, valine, leucine, isoleucine, lysine, phenolic compounds, lignoceric acid (C24:0), ethyl esters, and some volatile aldehydes were highest in browned tissue, compared with the other tissues. Many ethyl esters, aromatic amino acids, branched-chain amino acids, phenolic compounds, soluble solids content, fructose, and glucose were associated with internal browning. Furthermore, “tryptophan metabolism”, “arginine biosynthesis”, “alanine, aspartate, and glutamate metabolism”, “α-linolenic acid metabolism”, and “glycine, serine, and threonine metabolism” were the processes most impacted by internal browning. Overall, the largest metabolic differences appeared between damaged and asymptomatic cortex as several metabolic processes were influenced by internal browning.