By Yoon Ja-young

The season for kimchi-making has arrived. In the past, people used to dig a hole in the ground to bury the crock to preserve the kimchi. Though there was no refrigerator, it remained tasty for the next year.

Kimchi refrigerators, which are manufactured only in Korea, aim at mimicking the conditions of a clay container buried in the ground. It requires a lot more delicate technology than a regular refrigerator.

A must-have item for Korean households

The history of the kimchi refrigerator dates back to 1995 when Winia Mando, a mid-tier company, launched "Dimchae," now the symbolic synonym for a kimchi refrigerator.

It sold 5,000 sets in the first year, and sales doubled to 10,000 the following year. It continued steep growth to reach 80,000 in 1997, 228,000 in 1998 and 530,000 in 1999. In late 1990s, housewives often set up a rotating fund among themselves to get one.

It has turned into a must-have item from a dream product of housewives. The whole industry sold 1.1 million kimchi refrigerators last year as the market grew into a 1.1 trillion won business. Over 14 million kimchi refrigerators were sold last year, and 81.3 percent of households have the item, while only 11 percent had it in 2000. Some households have two or three kimchi refrigerators.

Winia Mando opened up the market, but conglomerates like Samsung Electronics and LG Electronics joined the growing market as well as some smaller players. Now there are diverse products, with prices ranging from around 500,000 won up to 4 million won for a premium product. They can store over 100 heads of cabbages of kimchi.

Technology for the best fermentation

The taste of kimchi depends on the ingredients and method as well as the chemistry between the nutrients and enzymes. Kimchi becomes tasty kimchi as the sweet factor seeps from the Chinese cabbage in the fermentation process and the lactic acid increases. The pH is around 4.5 and the acidity level is between 0.6 and 0.8 percent.

As time goes by, however, crunchy kimchi becomes sour and the texture becomes soft and soggy as the lactic acid increases. The kimchi refrigerator aims at maintaining the acidity level at between 0.6 and 0.8 percent, and keeping a low and stable temperature is essential here. "In conventional refrigerators, the cooling system will work to lower the temperature of the freezer to, say, minus 25 degrees Celsius. It continues if the temperature reaches minus 18 degrees. Such a huge gap in temperature, however, will ruin the taste of kimchi," explained a representative for LG Electronics.

The core difference between a kimchi refrigerator and other refrigerators is that the former directly cools the storage room. The first models of kimchi refrigerators thus had a cooling pipe around the steel board that wrapped around the storage room.

"Conventional refrigerators have an indirect cooling system where cool air circulates. The temperature gap within the refrigerator room is as great as 10 degrees. As it pulls the air in the storage room to convert it into cool air, it also pulls the humidity out of the food. It suits the storage of western-styled food that is usually dry, but it isn't appropriate for kimchi and other Korean food that contains a lot of soup and juice," said a representative for Winia Mando.

Kimchi refrigerators, meanwhile, adopts direct cooling, just like the cold earth around the pottery that cools it directly. It maintains a constant temperature and maintains humidity.

While direct cooling is better for kimchi, some kimchi refrigerators adopt an indirect cooling system as it better suits storing diverse foods.

Now, technologies are being applied to enhance the taste, nutrition and healthfulness of the food. Kimchi refrigerators have fermentation technology applied to help useful lactic acid bacteria to grow and to increase amino acid and vitamin C.

They also have technology to get rid of odors. Using light from an LED lamp, Dimchae has the deodorization system that breaks down smell particles as well as harmful germs.

As they should delicately maintain the proper conditions, kimchi refrigerators have a lot more sensors than conventional fridges. Samsung Electronics, for instance, has a smart eco system where nine sensors work to track the temperature, humidity and the opening of the door.

They also offer diverse fermentation processes. LG Electronics' Quad, the latest model, keeps the taste of the kimchi for up to six months by effectively repressing the activity of Lactobacillus which makes kimchi sour. The storage room in the middle provides the temperature equal to a crock buried in the ground in the winter, while the upper section can ripen kimchi in just four days.

Expanding the market

When first introduced, the device was used only for storing and ripening kimchi. Now, households here use it for diverse purposes such as storing vegetables, fruit and fresh meat. Local manufacturers, hence, are considering exporting the product to other countries.

Kimchi refrigerators led to the development of other special refrigerators, such as a rice refrigerator, cosmetics refrigerator and wine refrigerator here.

It changed the lifestyle of Korean households as well. Thanks to the new device, people can make kimchi anytime of the year. It helped stabilize vegetables and other spice prices as it has become possible to make and store kimchi year round.