What substance is the white powdery coating on grapes?

What is it:

Have you ever seen a white, powdery substance on grapes? Many people believe it is pesticides. This assumption, while incorrect, is valid due to the prevalence of using such chemicals in agriculture today. This substance is actually composed of several different materials. 

The first material, comprising most of the white substance, is harmless wax. The grape vine produces this wax while the grape is growing to help reduce the loss of moisture. This keeps the grape firm and prevents it from withering away. 

The second substance contained within the white powder is merely dust. Wax retains things that touch it as it is slightly sticky. Because of this, any dust or other small, fine particle that blows by in the wind and touches the grape has a chance to stick to the fruit. This physical property also includes living particles, which leads us to the final substance present within the white coating of a grape.

Yeast is a natural fungus. While some believe the plant produces this fungus to aid the growing process, it actually does not. The yeast is believed to be ambient within the air around the plant that gathers on the grape over time. If the thought of a fungus being on your grapes freaks you out, do not worry!

Interestingly enough, yeast is used in the process of making alcohol. This process, called fermentation, requires yeast to consume the glucose (sugar, essentially), present within grapes to turn it into wine. This process can take up to six months. After this process is completed, the alcohol is ready for consumption. Wine producing companies will also often age the wine in hopes of improving or modifying the taste. Some wines are aged for decades. These bottles are exorbitantly expensive.

When yeast absorbs and processes the glucose, it releases bubbles of carbon dioxide. This is one reason yeast is used in baking bread. When it absorbs the glucose present within the ingredients of the dough, the release carbon dioxide bubbles make the dough rise, giving us lighter dough with more volume. This is also where the “bubbles” present in bread come from. 

While pesticides may not comprise any bit of the visible, white material, it is likely still present. Because, of this, always wash grapes before consumption. This rule should also apply to all fruits, especially freshly bought ones. You never know who has touched the fruit before you, especially when bought from a supermarket where anyone can touch them.

Grapes in Culture:

Grapes are a near ubiquitous presence within our world today. They are a favored fruit and an ingredient in many types of alcohol and spirits. Their flavor pervades candy and medicine everywhere. Here are some products related to grapes you might enjoy:

Product
Visual
Where to Buy
The Grapes Of Wrath
Red Seedless Grapes Fresh Produce Fruit Per Pound
Hand Blown Italian Style Crystal Bordeaux Wine Glasses
GONGSHI 3 Tier Stackable Wine Rack

 

Many people believe that it is pesticide. It is true that in some regions maximum quantity of pesticides are sprayed on grapes. However, white powdery coating on grapes is not pesticide. It is yeast, a type of fungi. Originating as microscopic single cell organisms from grape vine, these cells reproduce in large numbers by splitting and budding, ultimately covering each grape. They survive by consuming glucose in grape and release carbon dioxide and alcohol as by-product, so to say. Both these products cause fermentation in the substance which contains glucose. This is the reason for using yeast in baking bread and cake. Tiny bubbles of effervescence caused by carbon dioxide that yeast releases after consuming glucose contained in wheat expand the dough making it lighter and full of small holes. As there is abundant glucose in grapes, yeast can convert it fully into alcohol within six months.

Additional reading:
Grape (Wikipedia)
Yeast (Wikipedia)

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