Volatile compounds and odour characteristics of five edible seaweeds preserved by high pressure processing: Changes during refrigerated storage

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

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.

Modified Atmosphere Packaging (MAP) for Seaweed Conservation: Impact on Physicochemical Characteristics and Microbiological Activity

Conventional conservation techniques such as drying, salting or freezing do not allow for preserving the original characteristics of seaweeds. The present work aims to study the impact of minimal processing, in particular "Modified Atmosphere Packaging" (MAP), on the physicochemical characteristics and food safety of two seaweed species, "laver" (Porphyra umbilicalis) and "sea-lettuce" (Ulva lactuca), stored at 6 °C for 15 days. Different parameters were evaluated using analytical methods, namely the composition of headspace gases, color, texture, microorganisms, and volatile organic compounds (VOCs). The main findings of this study were that the MAP treatment was able to inhibit the respiration rate of minimally processed seaweeds, also preserving their color and texture. There was a remarkable reduction in the microbial load for P. umbilicalis treated under modified and vacuum atmospheres, and U. lactuca exhibited relatively steady values with no notable differences between the treatments and the control. Therefore, during the 15-day study period, both seaweeds met the requirements for food safety. GC-TOF-MS allowed to conclude that both MAP and vacuum treatments were more efficient in maintaining the odor characteristics of U. lactuca compared to P. umbilicalis with no significant differences throughout the storage days. Metabolic responses to diverse sources of abiotic stress seemed to account for most of the changes observed.

Anti-Melanogenesis and Photoprotective Effects of Ecklonia maxima Extract Containing Dieckol and Eckmaxol

Seaweeds are potential ingredients in the cosmeceutical industry. Our previous study demonstrates that the phlorotannin-enriched extract of Ecklonia maxima (EME-EA) containing dieckol and eckmaxol possesses strong anti-inflammatory activity and suggests the cosmeceutical potential of EME-EA. In order to evaluate the cosmeceutical potential of EME-EA, the anti-melanogenesis and photoprotective effects of EME-EA were investigated in this study. EME-EA remarkably inhibited mushroom tyrosinase and melanogenesis in alpha-melanocyte-stimulating hormone-stimulated B16F10 cells. In addition, EME-EA significantly suppressed UVB-induced HaCaT cell death that was consistent with inhibition of apoptosis and reduction in scavenging intracellular reactive oxygen species. Furthermore, EME-EA significantly inhibited collagen degradation and matrix metalloproteinases expression in UVB-irradiated HDF cells in a concentration-dependent manner. These results indicate that EME-EA possesses strong anti-melanogenesis and photoprotective activities and suggest EME-EA is an ideal ingredient in the pharmaceutical and cosmeceutical industries.

Characterisation of the volatile profile of microalgae and cyanobacteria using solid-phase microextraction followed by gas chromatography coupled to mass spectrometry

Microalgae and microalgae-derived ingredients are one of the top trends in the food industry. However, consumers’ acceptance and purchase intention of a product will be largely affected by odour and flavour. Surprisingly, the scientific literature present a very limited number of studies on the volatile composition of microalgae and cyanobacteria. In order to fill the gap, the main objective of the present study was to elucidate the volatile composition of seven microalgal and cyanobacterial strains from marine and freshwaters, with interest for the food industry while establishing its potential impact in odour. Among the seven selected strains, Arthrospira platensis showed the highest abundance and chemical diversity of volatile organic compounds (VOCs). Aldehydes, ketones, and alcohols were the families with the highest diversity of individual compounds, except in Arthrospira platensis and Scenedesmus almeriensis that showed a profile dominated by branched hydrocarbons. Marine strains presented a higher abundance of sulfur compounds than freshwater strains, while the ketones individual profile seemed to be more related to the taxonomical domain. The results of this study indicate that the VOCs composition is mainly driven by the individual strain although some volatile profile characteristics could be influenced by both environmental and taxonomical factors.

Impacts of novel blanching treatments combined with commercial drying methods on the physicochemical properties of Irish brown seaweed Alaria esculenta

Alaria esculenta is one of the most abundant edible brown seaweeds in Irelandandisconsidered an excellent source of nutrients, sought after by the food, nutraceutical and pharmaceutical industries. Seaweed is typically blanched and dried prior to consumption to enhance the end-product quality attributes and shelf life. Three blanching techniques were examined in this work; conventional hot water blanching, novel ultrasound blanching and microwave blanching. The L* and b*colour metrics were affected significantly (P < 0.01) by the processing methods. There were 76 volatile compounds detected in blanched and dehydrated Alaria esculenta. Freeze-dried samples after treatment with microwave alone (at 1000 W) and microwave (800 W) combined with ultrasound (at 50% amplitude) had the highest retention rate of volatile compounds (up to 98.61%). Regarding mineral content, drying methods significantly affected (P < 0.05) the content of Ca, Co, Cu and Fe, while blanching treatments significantly affected (P < 0.05) the content of Na, Cu, Fe and Mn.