Rumors debunked | The seaweed egg drop soup is green instead of purple. Did you buy defective seaweed?

Speaking of seaweed, does "seaweed egg drop soup" immediately come to mind? Since it is called seaweed, it should be purple, but careful people will find that the seaweed in the prepared seaweed soup is often green.

Did I buy fake laver? In fact, people still have some misunderstandings about laver. If you buy laver for the New Year, you must be careful.

01

The dried seaweed cannot be torn apart. Is it made of plastic?

No, it’s just the characteristic of seaweed!

I remember seeing a video that said that seaweed that cannot be torn apart by hand is fake seaweed and is made of plastic.

Image source: Video screenshot

In fact, the reason why seaweed is so "firm" is affected by the harvest period.

Studies have shown that although the harvesting period has no significant effect on the toughness of Porphyra haitanensis, its hardness and elasticity will increase as the harvesting period is delayed. [1]

That is to say, laver, which is rich in polysaccharides such as gelatin, will become smooth and tough after being harvested and dried. The later the laver is harvested, the firmer it is, the tougher it is, and the harder it is to tear. Therefore, it cannot be considered that laver is made of plastic.

02

What is the relationship between laver and seaweed?

The ingredients of seaweed are almost all "nori"!

Nori is a very popular snack, loved by both adults and children for its delicious taste and crispy texture.

But do you know what seaweed is made of? If you don't look at the ingredient list, many people would think that seaweed is just seaweed, what else can it be made of? However, if you look at the ingredient list, you will find that most seaweed is made of "seaweed".

In fact, nori is also a kind of laver. Laver is generally divided into two types, "laver with stripes" and "laver with tan". Most of the nori are made from laver with stripes, such as the one in the picture below.

Image source: E-commerce screenshot

Some people may ask: What does tan laver look like? It looks like the picture below. The laver that most families buy from supermarkets and vegetable markets looks like this. It is very common.

03

Why is the seaweed in the soup green?

It’s related to the changes in phycoerythrin!

The color of laver is the most likely part of it to cause rumors. Before cooking, laver is usually purple, or even black purple, but after cooking, many people will find that the laver turns green. People who don't know the truth will think that they have bought fake laver, but it is not.

The reason why nori is purple is because dried nori contains rich "phycoerythrin". Phycoerythrin is unstable and will decompose when exposed to heat. After decomposition, chlorophyll and lutein become the main coloring substances, and nori turns "from purple to green".

This color change is normal and there is no need to worry. However, on the other hand, if you find that the seaweed soup has turned purple, then you have bought problematic seaweed!

04

What nutritional properties does seaweed contain?

Nori is relatively rich in nutrients, including protein, vitamins, minerals, fat, dietary fiber, etc., among which the fat is mainly unsaturated fatty acids[2].

The iron content of dried laver is relatively high, at 54.9 mg/100 g [3]. To make a serving of laver egg drop soup, you need about 2 to 5 g of dried laver (the picture below shows 2 g of dried laver). If calculated based on 5 g, the amount of iron you can ingest is 2.7 mg, which is comparable to that in spinach.

Image source: Original image

In addition, the study also mentioned that seaweed has health benefits such as anti-aging and lowering blood lipids.

Some people say that dried laver is rich in dietary fiber. This is indeed true based on data—21.6g/100g[3], but considering that the amount eaten each time is relatively small, it is not a big advantage.

05

How to choose good seaweed?

This can be compared from the following two levels of description [4]:

High-quality seaweed:

① Appearance: shiny, thin, purple-brown or purple-red, free of impurities

② Smell: aromatic, soft texture

Substandard seaweed:

① Poor gloss, uneven thickness of flakes, red with green mixed in

② Smell: poor aroma and taste, many impurities, and mud.

Image source: Original image from Science Refutes Rumors

References:

[1]. Xuan Shifen, Zhu Yukang, Sun Nan, et al. Analysis of sensory quality and protein composition of Porphyra haitanensis at different harvesting periods[J]. Food Industry Science and Technology, 2020(14).

[2]. Zhang Quanbin, Zhao Tingting, Qi Huimin, et al. Overview of research on the nutritional value of laver [J]. Marine Science, 2005, 29(2): 69-72. DOI: 10.3969/j.issn.1000-3096.2005.02.014.

[3]. Yang Yuexin. Chinese Nutrition Composition Table 6th Edition. Volume 1[M]. Peking University Medical Press: Beijing, 2019.

[4]. Zhou Xiaoyan. Cooking Technology. China Textile Press. 1st edition. 2008.7

This article was first published on the "Science Rumor Refutation Platform"