Chapter 158 of "Shokugeki no Soma" is already online through Manga Stream. The current chapter continues the shokugeki between Ryo of Cutting Edge Research Society and Rentaro of Central Division.
Both chefs already forwarded their food for judging. Before any predictions and spoilers of the upcoming events, here's a brief recap.
Ryo and Rentaro have already forwarded their respective salmon menu to the judges. Both dishes earned high praises from the judges and even though it looks like they are tied, one judge points out the decisive difference on the presented dishes.
Although the decisive difference was not revealed yet, it was found out that Rentaro used the steam convection oven to its full advantage by adding olive oil at the bottom to preserve the moisture. Rentaro was quite confident about his dish with the use of thermal convection oven and olive oil but everyone was surprised when Ryo was declared the winner. Rentaro protested but was surprised with the high quality dish Ryo prepared.
The upcoming chapter will reveal the secret of Ryo's cooking and how he has evolved as a chef. It's most likely an explanation on the "green layer" in the recipe that has preserved the quality of the salmon while perfectly combining the extensive ingredients as well as on the special method in maintaining the quality of the salmon.
User Tomhap on Reddit confirms the skills in Ryo on his victory against Rentaro, "I don't think central is going to win. This chapter is going to be all about crushing central's way of thinking. Besides Kurokiba is one of the three best cooks from the cast of protagonists, he's not going to lose to some member of the survivor's purge that's not even in the elite 10."
User JonDou on Manga Helpers speculates that the green layer added could be kelp, "I'll vote for kelp. It's what is used to make dashi soup stock which is rich in umami taste. Dashi is made by putting dried kelp in water and bringing it to almost a boil, removes the kelp and add dried bonito flake, boil until the flakes sink and then strain. Kelp is edible and has a pleasant taste of the sea. Salmon's strong, fishy flavor could meld well with kelp and infuse the rice with the umami taste of salmon-dashi."