Cooking effects on chlorophyll profile of the main edible seaweeds

Abstract

Edible seaweeds are rich in chlorophyll pigments, although their modifications during cooking remain unknown. Consequently, the three most consumed seaweeds of different categories: Nori (Porphyra umbilicales), Sea Lettuce (Ulva sp.) and Kombu (Laminaria 2 ochroleuca) were subjected to two cooking processes, boiling and microwaving. The chemical reactions of the chlorophyll pigments were determined by HPLC-UV/Vis. Besidesthe main chlorophyll transformations already described in fruits and vegetables (pheophytinisation and decarboxymethylation), the cooking of seaweeds caused a high level of oxidative reactions. Statistically, Nori was the most resistant algae to heating, while Sea Lettuce was the most labile seaweed. We report the thermal stability of c series for the first time, which were significantly less stable than a series in Kombu. Differences after microwaving and boiling methods depend mainly on the seaweed class. In conclusion, the seaweed structure is the main factor that determines the influence of cooking on the chlorophyll profile.

Cooking effects on bioaccessibility of chlorophyll pigments of the main edible seaweeds

“…The only difference is the formation of pyropheophytin a that reaches higher values after the in vitro digestion of processed Nori (6%) than that for fresh dried Nori (3.4%, Chen et al, 2018a), as pyro-derivatives are favored during the cooking of this seaweed (Chen et al, 2018c). The similar stability of chlorophylls during the in vitro digestion of fresh and cooked Nori seaweeds ,is mainly due to the resistance of red seaweeds to the cooking process, where the chlorophyll profile is almost unalterable during the boiling and microwaving processing (Chen et al, 2018c). Similar results were also found in the assay of arsenic analysis of Nori seaweeds where arsenic chromatographic profile was the same before and after cooking procedure…”

“…The main characteristic of boiled and microwaved Sea Lettuce, which contains a and b series of chlorophyll, is the presence of low amounts of chlorophyll b (16%) and no chlorophyll a, in comparison with fresh dried Sea Lettuce (approx. 75% of chlorophylls, Chen et al, 2018c). In this sense, the main reaction associated with chlorophylls during the in vitro digestion is the substitution of the central magnesium by hydrogen (Ferruzzi et al, 2001) but in cooked green seaweeds the substrate of this reaction is limited to the low presence of chlorophyll b. Consequently, during the in vitro digestion of cooked Sea Lettuce, the reactions are strengthened over pheophorbides and pheophytins and not with chlorophylls as that during the in vitro digestion of fresh dried green seaweeds (Chen et al, 2018a).…”

“…The processing of brown seaweeds introduces smooth modifications in the chlorophyll profile (Chen et al, 2018c). Specifically, the cooking of Kombu seaweeds implies a slight decrease in the percentage of chlorophylls (10%) and the respective increase in the proportion of pheophorbides.…”

“…Interestingly, the recovery rate of chlorophylls from processed Nori after the in vitro digestion is similar to that from fresh dried Nori, around 75% (Chen et al, 2018a). The red seaweed is, in terms of chlorophyll metabolites, the more resistant to the cooking process (Chen et al, 2018c), nearly without any net degradation of chlorophylls or any modification in the chlorophyll profile during the processing (microwave or boiling). Consequently, as the seaweed is not affected by the cooking process, the recovery rate is the same after the in vitro digestion of fresh or processed Nori.…”

“…Truly, edible seaweeds are always consumed after cooking process to improve the palatability of the product (García-Sartal, Romarís-Hortas, Moreda-Piñeiro, Dominguez-Gonzalez, & Bermejo-Barrera, 2011). During cooking process, chlorophyll pigments in edible seaweeds were modified differently according to different species and cooking conditions (Chen, & Roca, 2018c). Pheophytinization, oxidation and decarboxymethylation reactions are the main reactions influencing the chlorophyll profile of cooked seaweeds, and the final chlorophyll composition in cooked Nori, Sea Lettuce and Kombu seaweeds depends of their own characteristic.…”