Effects of Different Storage Conditions on the Browning Degree, PPO Activity, and Content of Chemical Components in Fresh Lilium Bulbs (Liliumbrownii F.E.Brown var. viridulum Baker.)

Kanghong Zhao,Hongqi Xie,Zhengpeng Xiao,Jianguo Zeng

doi:10.3390/agriculture11020184

Abstract

Although Lilium brownii (L. brownii) bulbs are popular fresh vegetables, a series of quality problems still remain after harvest. In this study, fresh L. brownii bulbs were placed in the dark at 25, 4, and −20 °C and under light at 25 °C from 0 to 30 days; the chemical compositions were analyzed by ultraviolet spectrophotometry (UV) and high-performance liquid chromatography quadrupole time-of-flight mass spectrometry (HPLC-Q-TOF-MS). During the 30-day storage period, the browning degree increased over the storage time and with increasing temperature, but the contents of proteins and free amino acids decreased and were aggravated by light. The total polyphenol content increased until the 6th day at 25 °C (dark or light), but it did not significantly accumulate at −20 or 4 °C. The reducing sugar content showed a dynamic balance, but the total polysaccharide content decreased constantly in the four storage conditions. The polyphenol oxidase (PPO) activity increased with storage time and increasing temperature, while it was inhibited by light. The increase rates of malondialdehyde (MDA) content at −20 °C and light (25 °C) were higher than those at 4 and 25 °C. In addition, 12 secondary metabolites were identified, most of which accumulated during the storage period, for example, 1-O-feruloyl-3-O-β-D-glucopyranosylglycerol; 1,3-O-di-p-coumaroylglycerol; 1-O-feruloyl-3-O-p-coumaroylglycerol; and 1,2-O-diferuloylglycerol. The variations in nutrient levels had a low correlation with browning, but the variations in MDA, PPO, and secondary metabolite (phenolic acids) levels had a high correlation with browning. In conclusion, fresh L. brownii bulbs should be stored at a low temperature (4 °C) and in dark condition, and browning bulbs are excellent materials for secondary metabolite utilization.

Highlights

The genus Lilium has over 110 species in the world, of which 55 species are found in China [1]
The results show that the contents of phenolic acids in L. brownii bulbs increased rapidly when exposed to sunlight, which is similar to the results of French scholars on grapevine cutting [62]
The results showed that the contents of nutrients in fresh L. brownii bulbs decreased during the storage period, which was accelerated by light and a high temperature, and the appearance became worse

Summary

Introduction

The genus Lilium has over 110 species in the world, of which 55 species are found in China [1]. Lilium is an important traditional Chinese medicine and edible food, and it is widely used as a horticultural ornamental plant. Bulbs (L. brownii), with a long medicinal history and active ingredients (such as polyphenols, saponins, and polysaccharides) [4,5], has been shown to have anti-inflammatory, anti-tussive, hypoglycemic, antioxidant, immune-modulatory, and anti-tumor effects [6,7]. Apart from their bioactivities, L. brownii is mainly enjoyed by consumers for its edible properties. Polysaccharide, protein, amino acids, phospholipid, and starch (primary metabolites) are probably the most important parameters [8]

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