March 6, 2018 Robin

What is Blanching and why is it Done?

Shot of a focused young factory working doing quality control in a vegetable processing plant

Blanching is one of the most important steps in the world of food processing. Blanching does several things:

  1. It inactivates enzymes
  2. It sets color
  3. It reduces volume by driving out intercellular air

Industrial processors routinely blanch vegetables prior to freezing and canning for quality reasons and even to ensure the production of safe foods. Recent work by the American Frozen Foods Institute (AFFI) has demonstrated that blanching of vegetables will kill potential food pathogens.

How many of you have sliced potatoes at home and left them out prior to final preparation? It began to turn brown, right? Browning reactions are enzymatic so using hot water or hot oil to heat the product to a temperature high enough to inactivate the enzymes will prevent browning. It will also help maintain product texture.  Blanching green vegetables helps set the color to a bright green that is highly desirable for potential consumers. And lastly, by reducing volume, products are more easily handled. Find a can that hold one pound of spinach and try to put one pound of fresh spinach in that can. It simply won’t work. Blanch the spinach in boiling water for a minute or so and you can easily fill the can.

In the fast food or restaurant industry, blanching is commonly done as a preliminary step to preparing French fries from fresh potatoes in the kitchen. The potatoes can be peeled and sliced into any shape and then blanched in hot water or hot oil. Hot water at temperatures greater than 190 – 195oF would be the preferred medium for ease of handling. After blanching, the sliced potatoes would be chilled in cold water and held under refrigeration until needed. The blanch step followed by chilling will ensure that the potatoes do not become brown and also accomplish one other thing; it will rinse starch from the potatoes, which can compromise oil quality and useable oil life. How long one blanches something and at what temperature will depend upon the product being blanched, its size and the loading of the blanching system. A thinly sliced potato will blanch more quickly than a wedge cut product. If your procedure calls for blanching one pound of product in boiling water for one minute, adding an extra half pound of potatoes to the basket being used would compromise the efficacy of the process.

So, the message is this; establish procedures that are effective, properly document them and train your people to follow those procedures as written.  If they deviate, the end result will be poor quality products.