When eating crayfish, why are my hands still greasy even though my gloves are not torn?

Audit expert: Gan Qiang

Lecturer at Beijing Institute of Technology, PhD in Applied Chemistry

It’s the season for eating crayfish again. Break open the shrimp head to reveal the tender white shrimp meat, with its tempting aroma and fiery red color. Thinking of this, tears can’t help but flow from the corners of my mouth...

Summer standard crayfish source 丨pixabay

However, after a hearty meal, your hands often become greasy, which makes you wonder why your hands are still greasy even though you are wearing gloves.

Why do gloves leak oil?

This starts with the material of disposable gloves. Most of the disposable gloves provided by merchants are made of PE (polyethylene, abbreviated as PE). Polyethylene is a high molecular compound, and the gaps between its molecules are very small, so oil molecules cannot pass through. However, disposable gloves are made up of polyethylene molecular chains. Each polyethylene molecular chain is like a cotton thread in a cloth. The cotton thread constitutes the cloth, and the polyethylene molecular chain constitutes the disposable gloves.

There are gaps between the cotton threads in the fabric, and there are also gaps between the polyethylene molecular chains. Affected by external factors, the stretching and elongation between the polyethylene molecular chains eventually lead to the stretching of the "fabric", and the gaps become larger, allowing oil molecules to pass through. In addition, there are lipophilic groups on the polyethylene molecules, which makes the polyethylene molecules more "loving" to be with oil than water. The oil molecules gradually blend into the gaps between the polyethylene molecules and eventually seep out to the other side of the disposable gloves. Of course, this process is relatively slow. So you have to hold the oily crayfish and eat it for a few minutes to ten minutes before you can feel it.

Source丨B station up master: This knowledge is so cold video screenshot

It is worth mentioning that PE products are also divided into low-density polyethylene and high-density polyethylene. As the name suggests, high-density polyethylene has a higher density and is more densely packed. Because the price is very cheap and it can save costs, many merchants provide PE gloves that are low-density polyethylene gloves, which are of course more prone to oil seepage.

Source丨B station up master: This knowledge is so cold video screenshot

So, water molecules are smaller than oil molecules, why do disposable gloves leak oil but not water? The reason is still because of the characteristics of polyethylene material. Polyethylene is an organic substance, and the oil used in daily life is also an organic substance. As the saying goes, birds of a feather flock together. Polyethylene molecules and oil molecules in crayfish are both non-polar molecules in chemistry. When the two meet, their inherent "genes" have already determined that they will be "attracted to each other". For polar molecules such as water, polyethylene and oil are naturally "not allergic" to water. Just like oil dripping into water is still oil, without the addition of a "third party", it will not reach a state of perfect harmony, so the gloves will seep oil but not water.

Source: Photographed by the author

In addition to the reasons for oil leakage mentioned above, the most direct reason is physical factors. As we all know, crayfish have many spines on their bodies. When eating crayfish, if you are not careful, your gloves will be scratched by the crayfish shell. After all, disposable gloves are also very thin.

After the gloves are damaged, not only will the grease in the food enter the gloves, but the seasonings and soup on the surface of the crayfish will also come into close contact with your hands. After eating, you will suck your fingers and instantly feel the gloves are lonely.

Why do we still need to wear disposable gloves?

Since wearing gloves when eating crayfish will leak oil and cannot keep our hands clean, should we just eat with our hands directly and lick our fingers after eating?
In fact, it is still recommended to wear gloves for two reasons. First, the oil in disposable gloves is only a small amount of penetration, and the effect is still better than not wearing gloves. Second, the purpose of wearing disposable gloves is also to prevent the bacteria on the hands and nails from being eaten. It is worth noting that when using disposable gloves, you should choose those produced by regular manufacturers. Poor-quality disposable gloves are likely to be made of recyclable waste, which not only further reduces the barrier properties of the gloves, but also poses the risk of harmful substances dissolving in oil and entering the human body.

How to solve the oil leakage problem?

First, change disposable gloves more frequently. Replace gloves in time when oil is not noticeable.

Second, wear more layers of gloves. If changing gloves frequently will interrupt the fun of eating crayfish, it is better to wear more layers of gloves before eating. Slow down the speed of oil penetration into the skin.

Even if your hands are full of oil, you can't resist the desire to eat crayfish. Source: pixabay

Third, wear food-grade PVC gloves. Disposable PVC gloves are made of polyvinyl chloride, and the molecular gap is smaller than that of PE gloves. The higher molecular density can effectively prevent oil penetration. However, it is worth noting that you should choose food-grade PVC gloves. PVC gloves that do not meet the standards may dissolve harmful substances, which will have adverse effects on health if accidentally ingested.

Fourth, wash your hands. For those who eat crayfish without gloves, peeling the shrimp with bare hands is the highest level of eating shrimp. Feeling the close contact between fingers and shrimp shells and shrimp meat, immersive peeling shrimp is really a great pleasure of eating crayfish. Of course, remember to wash your hands before eating, especially between your nails.