All the bamboo shoots on the mountain have been taken! Are spring bamboo shoots really this fresh?

Audit expert: Shi Jun

Doctor of Botany, well-known popular science writer

Plants are always the first to know the message of spring. They hear the call of the sun and rush to wake up from the fields. Toona sinensis, shepherd's purse, seaweed... Seasonal fresh vegetables also awaken our taste buds' memories of spring.

Bamboo shoots are the first delicacy in spring. Even the ancients never forgot about them and even listed them on a par with fish and turtle delicacies. Stir-frying, stewing, braising and boiling all have their own flavors. The dishes are delicious, but do you know why bamboo shoots are so delicious?

Source: Tuchong Creative

Where does the freshness of bamboo shoots come from?

Bamboo shoots have a crisp, tender and sweet taste, which is related to its ingredients. Bamboo shoots are mainly composed of water, protein, dietary fiber, carbohydrates, amino acids and minerals. According to statistics, bamboo shoots contain about 90% water, so they are crisp and refreshing to eat; there are up to 18 kinds of amino acids, with a content of about 8.216% to 28.025%. Different varieties of bamboo shoots vary greatly, and the amino acid content of golden bamboo is the richest.

Comparison of amino acid types and contents in bamboo shoots (unit: mg/kg)

Source: "Analysis of Nutritional Components of Bamboo Shoots of Phyllostachys pubescens", Wang Guoyu et al.

The secret of umami is hidden in amino acids. Let's look at the ingredient list of MSG. It is mainly divided into monosodium glutamate (sodium salt of glutamate). Therefore, umami is related to glutamate, and glutamate is the source of the umami of bamboo shoots. In addition, the umami of bamboo shoots is also related to aspartic acid. Take the bamboo shoots of Phyllostachys pubescens as an example. The aspartic acid content of this kind of bamboo shoots is about 3200mg/kg, and the glutamic acid content is about 2100mg/kg. The content of umami substances is higher than that of many aquatic products. No wonder bamboo shoots taste so delicious.

Source: a certain brand of MSG

Mushrooms, shrimps, crabs, etc. from the "umami family" all contain aspartic acid and glutamic acid.

Data source: Baidu Encyclopedia

Fresh bamboo shoots are wrapped in a tight outer layer. After peeling off the outer layer, the plump bamboo shoots are exposed, and you can also smell a burst of fragrance. Where does the "body fragrance" of bamboo shoots come from?

Source: Tuchong Creative

It turns out that bamboo shoots contain volatile aroma components, mainly aldehydes and aromatic compounds, which have a special aromatic smell and are also common in liquor and spices. Aldehydes in bamboo shoots include n-hexanal, and aromatic compounds are mainly cresol, 2-heptanol, etc.

Why do bamboo shoots age?

Bamboo shoots are the most delicious when they are just dug out. Unfortunately, from the moment they leave the soil, they inevitably age. Aging means that the soluble components in the shoots decrease, while the insoluble fiber and lignin content increases, which makes the quality of the bamboo shoots decline and the taste becomes rough. Why do bamboo shoots age?

Plants, like humans, respire and consume organic matter. After bamboo shoots are dug out, they have no energy to replenish, and their nutrients are constantly lost, and lignin is constantly precipitated, so they gradually become old.

We can also find that the roots of bamboo shoots are the first to become old and hard, so after leaving the bamboo shoots for a period of time, the lower half should be cut off before eating. This is because the formation of lignin starts from the root to the top, and many vegetables have this characteristic.

How to keep bamboo shoots fresh

The respiration of bamboo shoots accelerates the aging process, so in order to keep them fresh, their respiration must be reduced.

Low temperature, airtight refrigeration and preservation

Temperature is the main factor affecting respiration. Within a certain temperature range, the higher the temperature, the stronger the respiration, the more energy and organic matter consumed, and the faster the aging. Therefore, low temperature storage is necessary. So, what is the appropriate temperature? Studies have shown that the best storage temperature for fresh bamboo shoots is 2-4℃, which not only weakens respiration but also does not cause frostbite.

Refrigeration in supermarkets

Source: Tuchong Creative

In addition, the strength of respiration is directly proportional to the oxygen content. The higher the oxygen concentration, the stronger the respiration. This also explains why bamboo shoots age faster after being shelled, because the bamboo shoots receive more oxygen after being shelled, and their respiration intensity is about 1.4 times that of unshelled ones. According to this idea, we can also extend the storage time by wrapping the bamboo shoots with a layer of plastic wrap.

If CO2 and a large amount of N2 gas are added, the shelf life of fresh bamboo shoots can be extended to about 2 months, which is also a commonly used method for commercial preservation.

Quick freezing and refrigeration

If you want to preserve bamboo shoots for a longer period of time, such as half a year, you can use quick freezing. Quick freezing means that in a very short period of time (usually no more than 30 minutes), the core temperature of the object is quickly reduced to below -18°C and stored under low temperature conditions.

The freezer compartment of a refrigerator is usually around -18°C and is often used to store quick-frozen foods. Many people worry that quick freezing will affect the taste of food. In fact, the quick freezing process is very fast and causes little damage to cell tissues, thus preserving the color and aroma of the food well.

Quick-frozen bamboo shoots

Source: Huinong.com

Chemical preservation

The purpose of preservation can also be achieved by adding chemicals that inhibit respiration or reduce the activity of biological enzymes. This method is more common in commercial production, but it is rarely seen in life. In addition, it is recommended not to buy "three no" and "local method" products produced by various informal manufacturers to avoid health problems.

Among various chemical substances that can preserve freshness, vitamin C and citric acid are very good preservatives. Enzymes in bamboo shoots will undergo chemical reactions under the catalysis of peroxidase (POD) and polyphenol oxidase (PPO), causing them to turn brown. A certain concentration (usually 0.5%) of citric acid can reduce the activity of these two enzymes, reduce the browning reaction, and inhibit the aging of bamboo shoots.

Citric acid crystals source 丨 Wikipedia

In addition, some preservatives can be added, such as potassium sorbate, sodium benzoate, polylysine, etc. Don't be afraid of rot. When the amount used meets the standard, preservatives can inhibit the growth of harmful microorganisms, extend the shelf life of food, and are harmless to the human body. If the bamboo shoots are damaged when they are dug out, it is also a good idea to treat them with preservatives.

As I write this, my mind is already full of bamboo shoots, spring bamboo shoots with shredded pork, braised bamboo shoots with oil, bamboo shoots stewed with pork ribs... I'm so greedy, I want to have a good meal and eat the breath of spring into my stomach~