## 1 Introduction
Because of the short cooking time and high temperature, the content of bioactive substances in the cooked broccoli was higher than that resulting from other cooking methods. The total phenol content and pigment of articbakes, green beans, cauliflower, and carrots were studied under different cooking methods (boiling, sous-vide cooking, and water-immersion cooking). The preservation degree of phenolic content, carotenoid, and chlorophyll of all the tested vegetables by sous-vide cooking was higher than that by boiling [15]. [PERSON] et al. [16] observed the impact on the content of carotenoids and chlorophyll of six kinds of vegetables under high-pressure (HP) and high-pressure and high-temperature (HPHT) treatments. In terms of chlorophyll, there was no increase or degradation in HP treatment at 20 \({}^{\circ}\)C. HPHT treatment (70 \({}^{\circ}\)C and 117 \({}^{\circ}\)C) degraded both types of chlorophyll, but chlorophyll a was less stable at 70 \({}^{\circ}\)C than chlorophyll b. One possible reason is that chlorophyll a is converted to pheophytin more easily than chlorophyll b or that chlorophyll b is more stable during thermal treatment than chlorophyll a [17]. [PERSON] et al. [18] studied the effects of traditional cooking methods (blanching, steaming, boiling, and baking) on the color, texture, and bioactive nutrient content of _U. pinnatifida_ (_U. pinnatifida_), and the results showed that blanching and boiling were more beneficial than other cooking methods in maintaining the quality of _U. pinnatifida_. In addition, [PERSON] et al. [19] further investigated the effects of domestic cooking methods (air frying (AF), microwave, and high-temperature and -pressure (HTP) cooking) on the quality, nutrient content, and bioactive substances of _U. pinnatifida_, and the results showed that of the three processing methods, microwave cooking had a more favorable effect in maintaining the quality of _U. pinnatifida_. [PERSON] et al. [20] reported on the effects of blanching, freezing, and fermentation on the physicochemical, microbiological, and organoleptic quality of sugar kelp (_Saccharina latissima_). The results showed that the simplest cooking processes, such as blanching and freezing, could preserve the quality of the kelp and extend its short shelf life. [PERSON] et al. [21] studied the effect of temperature and cooking time on the physicochemical properties and sensory potential of aqueous extracts of seaweed from _Palmaria palmata_ and _Saccharina longicruvis_. They found that the aqueous extract preserved the nutrients in the crude seaweed and that the effect of temperature and cooking time depended on the composition and the seaweed. Cooking methods and other processing methods might have an effect on seaweed quality, but studies on the differences in processing characteristics and bioactive components of _L. japonica_ are incomplete. Domestic cooking methods such as blanching, steaming, boiling, and baking are the most common methods of seaweed processing and are suitable for home cooking and are preferred by consumers. Therefore, in order to fill this research gap, the aim of this study was to assess the effects of four domestic cooking methods (blanching, steaming, boiling, and baking) on the processing characteristics, phloroglucinol, pigments, structure, and flavor component of the _L. japonica_. In addition, we also observed and analyzed the microstructural changes of kelp treated by different processing methods through SEM to reveal the effect of cooking methods on the texture of kelp from a microscopic perspective. In this study, the best cooking method to maximize the retention of active substances and to improve the processing characteristics of the product was investigated.