Why is Freezing an Effective Method of Preserving Food?

Dec 17, 2017 by

When attempting to keep food lasting longer on the shelves, and in people’s homes, determining what the most effective method of preservation is, is commonly questioned. Over time, and period of trial and error, freezing food seems to be the best option overall. While there are many other effective methods that have been carried out for centuries, in a commercial sense, freezing has seemed to work best.

How to Preserve Food – Methods and Techniques?

As food preservation is an ancient practice that has been done across all cultures, the methods and techniques are vast. Here are some common practices that many people still use.

  1. Drying:

Arguably the oldest method of food preservation, drying can ensure your food lasts much longer than fresh fare. Because this process reduces water activity, it prevents and delays bacterial growth from manifesting. Especially in warmer and sunnier climates, drying and dehydrating food is a practice used in compliance with the sun and nature, a process for removing moisture. Southern Italy is known for drying tomatoes, while India commonly dries chilies, mangos and spices. To do this yourself, you can start with herbs. Tie them together and hang them in a sunny spot, away from humidity. Fruits and vegetables require a clean, flat surface, as well as a dry and warm climate, as they will be needed to be in the sun for a few weeks. Electric dehydrating machines are now available as well, allowing anyone, anywhere to do this. Other foods that can be dried are meats, and grains such as rice, rye, barley, oats, maize, wheat and millet.

  1. Salting:

Common amongst meat and fish, salting is a form of the drying method used to preserve food. Since salt removes moisture through the process of osmosis, meat can be cured, which lowers its bacterial content and makes it adaptable for later use.

  1. Canning:

This process requires heat. You must first cook the food that’s meant to be preserved, and then seal it in sterile jars or cans. Developed by a French chemist to preserve food for Napoleon’s army, this is a very popular and effective method of food preservation, and can be used for fruits, vegetables, and meats.

  1. Pickling:

Pickling is very similar to the process of canning, however here you need the addition of salt and acid. Soaking your produce in a brine with salt is required. The produce will pickle for a period of time before being transferred into a jar of vinegar, where it will keep. Because pickling kick-starts the process of fermentation, pickled vegetables have boosted levels of vitamin B6, a healthy bonus to the process.

  1. Freezing:

Commonly used domestically and commercially, this method is the easiest and most frequently used. Freezing can change the texture of some fruits and vegetables, but it fairs well with meat and fish. Freezing allows us the flexibility of using our food whenever we need it, and ensuring nothing goes to waste. Almost anything can be frozen and thawed out later, as long as it is kept properly and sealed.

What are the Chemical Changes During Freezing?

Due to the natural process of chemical change that fruits and vegetables undergo, freezing them as soon after harvesting them as possible is best, as it maintains their peak ripeness, and ensures deterioration from bacteria hasn’t set in yet. When fruits and vegetables are frozen, their chemical compounds, or enzymes, can cause colour-loss and change, loss of nutrients, and flavour changes. In order to prevent this from happening, the enzymes must be inactivated to stop the reactions from occurring.

In order to inactivate the enzymes, vegetables must undergo a process called blanching. This process exposes the vegetables to boiling water or steam, and then moves them into an ice bath where they are cooled, preventing them from getting cooked. This process will inactivate the enzymes, as well as destroy any lingering microorganisms. Fruits need to undergo a different process, as blanching causes brown spots and the loss of vitamin C. They are coated with ascorbic acid, which is concentrated vitamin C, to ensure the reverse effects of their natural chemical changes.

Changes in Texture After Freezing?

Texture changes occur in frozen food because of the structural makeup of their cells. Most fruit and vegetables are made up of 90% water, which is held within their rigid cell walls, giving them support. When the produce is frozen, the water within the cells also freezes, causing the cell walls to rupture. Because of this, the texture is altered once thawed, as those rigid cell walls are no longer structurally intact, causing many types of fruits and vegetables to become quite mushy and watery. This is why produce with very high water content such as celery and lettuce, are rarely frozen. If these types of foods are frozen, they should be consumed before they are fully thawed, as a way to ensure some of their texture remains.

What Safety Measures Are Used During this Process?

When looking towards how the freezing process is regulated and standardized, metal detectors in the food industry have emerged as a more attractive and modern alternative to conventional X-ray inspection methods. Perks include similar or better performance but at a much less expensive cost. Metal detectors for the frozen food industry are excellent in detecting and eliminating threats of tramp metal contaminants in otherwise, good and sellable foods. With a fully equipped and integrated user interface, today’s industrial metal detectors electronically communicate data with the receiving coils of the detectors. Because of this electronic communication, the process is almost seamless and efficient, with recorded time/date stamps of detection, if present, a metal sample, and quality control tests.

When combining food conservancy methods like freezing, with highly efficient methods of metal detection, the frozen food industry is leading the way in providing a safe and effective approach to food preservation.

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