Post-Tet banh chung: Stored improperly, even the tastiest cake turns into a "breeding ground for bacteria"

From the traditional practice of hanging cakes near wood stoves to modern freezing methods, each approach has its own principles. By properly packaging, preserving, and thawing, chung cake remains not only safe to eat but also retains its freshly boiled flavor.

Ways to preserve and use Chung cake after Tet

During Tet, many families maintain the tradition of wrapping a lot of banh chung to consume gradually. However, if not stored properly, the cakes can easily spoil, the rice can dry out, the filling can turn stale, or they can absorb odors from other foods in the refrigerator.

Post-boiling handling of sticky rice cakes according to folk experience

According to folk experience, after boiling and taking them out, the cakes are often rinsed with cold water to clean the outer leaves and remove any grease film and starch clinging to the surface.

Afterward, the cakes are arranged neatly and pressed with heavy weights to drain all excess water from both the cake and the leaves. Once completely cooled, they are stored in baskets or hung near the wood stove. This method helps the cakes keep for a long time, lasting through the end of the first lunar month.

Freezing and thawing methods introduced

In modern living conditions, many families no longer have wood stoves, making freezing a popular option. However, if preservation is neglected, the cakes can easily suffer from freezer burn, become dry and hard, with mushy meat filling and diminished flavor.

The first rule is to let the cake cool completely before placing it in the refrigerator. A warm cake creates condensation when exposed to a cold environment, leaving moisture on the surface that promotes the growth of bacteria and mold. Heat can also raise the temperature inside the freezer, affecting other foods.

For small families, it is advisable to cut the cake into serving-sized portions before freezing for convenience and to avoid thawing multiple times, which increases the risk of bacterial contamination.

Packaging plays a decisive role. In a frozen environment, dry air makes moisture in food evaporate easily, causing "freezer burn." Therefore, the cake needs to be tightly wrapped in multiple layers of cling film, pressed closely to limit air entry.

Then, place them into ziplock bags, airtight containers, or vacuum bags to minimize air exposure. This method not only limits moisture loss but also slows down the oxidation of fats in the meat filling—the cause of off-odors after prolonged storage.

The ideal temperature for freezing bánh chưng is around minus 18 degrees Celsius or lower. At this temperature, microbial activity is almost completely inhibited, and biochemical reactions in the food occur very slowly, helping the cake maintain its quality for several months.

A common mistake is frying the cake while it is still frozen solid or soaking it in hot water for quick thawing. The temperature difference causes the outer layer to heat up first while the core remains cold, potentially posing a risk of bacterial growth if the process is prolonged.

The safe way is to move the cake to the refrigerator compartment for 8–10 hours or overnight to defrost slowly. Afterwards, you can steam it, microwave it, or reboil it briefly so it heats evenly. If you want to fry it, make sure the cake is completely thawed so the exterior becomes golden and crispy while the interior remains soft and chewy.

Expert opinions on storage and freezing times

Although freezing banh chung is a tip widely shared among homemakers on social media, according to Assoc. Prof. Dr. Nguyen Van Hoan, former Director of the Rice Research Institute at Vietnam National University of Agriculture, for homemade foods, shelf life depends heavily on how each household stores them. In principle, however, the longer cooked food is kept, the more its nutritional value declines and the less its original flavor remains.

He said that banh chung is best consumed within about a week, depending on storage conditions. The cake should be kept in a cool, dry place; if the ambient temperature is too high, the filling inside can easily become watery, develop an odor, and grow mold.

After Tet, if there are still many cakes left, families can store them in the refrigerator compartment at 5–10°C. Do not store the cake in the freezer. When cutting the cake, only cut what you eat; wrap the rest tightly with cling film to prevent moisture loss, which makes the cake dry, hard, and less appetizing.

Regarding the habit of freezing banh chung for gradual consumption, Assoc. Prof. Dr. Nguyen Van Hoan believes this is an unsuitable preservation method for starch-rich foods. According to him, the freezing process can alter the starch structure in rice grains, affecting the cake's quality. Therefore, he advises against storing banh chung in the freezer, even though it may still taste delicious when re-steamed or fried.

He also noted that starchy foods such as banh chung or white rice should be thoroughly reheated before consumption to ensure flavor and food safety. Improper storage, thawing, and handling can increase the risk of food safety hazards.

Signs of spoiled cakes that need to be discarded

Meanwhile, Assoc. Prof. Dr. Nguyen Duy Thinh from the Institute of Biotechnology and Food Technology, Hanoi University of Science and Technology, noted that if cakes show signs such as becoming watery, smelling rancid, or having a slimy or moldy surface, they should not be re-boiled for consumption. At that point, bacteria have infiltrated and spoiled the food; attempting to consume it can lead to food poisoning and affect one's health.