Profile change of the volatile and non-volatile compounds in dried or baked laver by photooxidation

Abstract

Effects of light or dark storage condition on the profile changes of volatile and non-volatile compounds were evaluated in dried and baked laver for 60 days. Volatile and non-volatile compounds were analyzed using gas chromatography-mass selective detection and high-performance liquid chromatography-quadrupole-time of flight-mass spectrometry, respectively. Baked laver stored in light conditions for 60 days produced the most volatile compounds, whereas dried laver stored in the dark produced the least volatile compounds. Total 11 classes of volatile compounds were detected, including alkanes, alkenes, and ketones, with aldehydes being most abundant in dried laver stored under light. Metabolite analysis of non-volatile compounds led to the selection of 12 compounds with a higher variable importance projection (VIP) value of >1.0: 6 fatty acids (VIP 1.2-2.0), 2 flavanols (VIP 1.3-1.8), hydroxybenzoic acid (VIP 1.5), hydroxycinnamic acid (VIP 2.3), a phenolic acid ester (VIP 1.9), and phloroglucinol (VIP 1.2). Generally, levels of these compounds decreased more following storage in the light than under dark, irrespective of laver preparation. The content of linolenic acid was particularly affected by storage conditions, with light conditions causing a fourfold reduction in linolenic acid level compared with dark conditions, which could result in an increased formation of aldehydes. Gallic acid and sinapinic acid were detected in dried but not baked laver, as they are destroyed by heat treatment. Therefore, laver should be baked and stored in dark conditions to prevent the development of rancidity. PRACTICAL APPLICATION: Laver is one of the representative seaweeds, and the popularity among consumers increases. Although commercially available laver is prepared in dried or baked condition, scientific studies on the changes of metabolites, including volatile and non-volatile compounds during storage, are scarce. The results of this study can be applied to improve proper storage methods to maintain the quality of laver, which can be beneficial for consumers and food industry.

Keywords: laver; non-volatile compounds; photooxidation; volatile compounds.