acorn
Acorn is the fruit of an oak tree, which looks like a cocoon. It is also called Chestnut, Oak Chestnut, Soap Bucket, Acorn, Oak, Bucket, Oak Mu Zi, Oak Seed and Hemp Fruit. It has a hard shell, brownish red appearance, and the inner kernel is like peanut kernel. It is rich in starch, which is edible and can be used as raw material for sizing in textile industry.
Pi Rixiu, a poet in the Tang Dynasty, wrote a poem "The Oak Sighs", which reads: "In autumn, the acorns are ripe, and the hazel hills are scattered, and the yellow hair is awkward, and the morning frost is picked up. When it was moved, it began to be full, and the Japanese side filled the basket and steamed it several times, which was used as grain for three winters ... "As can be seen from the poem, at the end of the Tang Dynasty, acorns were already a kind of food for the people. In Europe, Asia, North Africa, the Middle East and North America, acorns have been exploited and utilized for more than 6,000 years. Acorn is an important food source for North American Indians. In the poor areas of Italy and Spain, acorns account for 25% of the local food, and are mostly used to produce bread, cakes and as a substitute for coffee. Nowadays, the utilization of acorns, especially acorn starch, is mainly concentrated in North Korea, and China and Japan also make more use of it.
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Nutritional value of acorns
Sun Simiao, a medical scientist, said, "Acorns are neither fruits nor cereals, but they are the most beneficial to people. It is the best thing for anyone who can't break the grain. If there is no gas, it will give gas, if it is tasteless, it will give taste, and it will help digestion and stop dysentery, making people extremely healthy. " According to Li Shizhen's Compendium of Materia Medica in Ming Dynasty, acorns are rich in trace elements, which have health-care effects on human body, such as astringency, spleen and stomach conditioning, detoxification and weight loss, and have high medicinal value.
Modern scientific research shows that the contents of various nutritional components in acorn kernel are as follows: starch 50% 70%, soluble sugar 2% 8%, tannin 0.26% 17.74%, protein 1. 17% 8.72%, oil1. Generally speaking, the nutritional value of acorn kernel is close to or slightly lower than that of corn, but slightly better than that of rice.
Amino acids: Among the 18 amino acids contained in acorn protein, the contents of essential amino acids such as phenylalanine and isoleucine which cannot be synthesized by human body are particularly rich. These amino acids can promote cell metabolism, stimulate the secretion of pituitary hormones and adrenal hormones, promote microcirculation and improve the vitality of the body. Cystine is the lowest amino acid in acorn, followed by tryptophan and methionine, but the relative contents of arginine and lysine, the restrictive amino acids of cereals, are higher than those of corn by 52% and 68% respectively.
Oils and fats: Acorn oil contains seven main fatty acids, of which unsaturated fatty acids and essential fatty acids account for 79% and 76% of the total fatty acids. For example, the fatty acid composition of Quercus mongolica acorn is mainly composed of sub (50.98%) and oleic acid (29.4 1%), which indicates that acorn oil is beneficial to lowering blood lipid, preventing thrombosis, preventing hypertension and cardiovascular diseases.
Trace elements: The contents of zinc and iron in acorns are slightly lower than those in corn and sorghum, but the contents of potassium, sodium, calcium, magnesium, cobalt and manganese are higher than those in corn and sorghum. In addition, acorns contain trace element vanadium, which is rarely contained in other organisms. Vanadium can control the concentration of brain acid in plasma and tissues, control the oxidation of phospholipids and the activity of COA- deacylase in human body. Obese people can achieve the effects of losing weight, reducing blood fat, caring skin and expelling toxins after eating for a long time, thus controlling and delaying human aging.
Other bioactive components: Acorn kernels contain polyphenols such as tannins, gallic acid, trans-gallic acid and flavonoids, all of which have high antioxidant activity.
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Classification of acorns
Oak, also known as oak, is a general name for Quercus plants in FAGACEAE. There are more than 300 kinds of oak trees in the world, and there are about 60 kinds in China. China is one of the main producing areas of acorns in the world. The famous oak trees in the north of China are Quercus liaotungensis and Quercus mongolica, Quercus cyclobalanopsis, Quercus alpine and Quercus spinosa in the south, and Quercus variabilis, Quercus acutissima, Quercus quercus and Quercus oak in the north and south. Acorns produced by different kinds of oak trees also have different shapes.
Shaanxi Province is a big province with acorn resources in China, with a total area of 30 million mu, covering 3 1 county of 7 cities in the province, accounting for about 50% of the total area of the country. Among them, Hanzhong, Shangluo and Ankang are the main cities in Qinba Mountain area, and the annual output of acorns can reach more than 6 million tons, accounting for about 1/3 of the whole country.
Here are some major oak varieties:
① Quercus liaotungensis: Quercus of FAGACEAE, a deciduous tree, mainly distributed in Heilongjiang, Jilin, Liaoning, Hebei, Henan, Shandong, Sichuan, Gansu and other provinces. Born on the hillside, it is often mixed with Populus davidiana, Betula platyphylla and Pinus tabulaeformis or a pure forest, which is cold-resistant. The shell bucket is cup-shaped, and the seeds contain starch, which can be used as wine and feed.
(2) Quercus acutissima: deciduous tree, up to 25 meters high, with dark gray bark. Tree species are excellent, like light and high temperature, and should grow in humid climate and fertile soil, so they are vulnerable to freezing injury. Shandong, Henan, Hebei, Liaoning, Jilin, Gansu, Jiangsu, Jiangxi and other provinces are all distributed. The shell bucket is cup-shaped and surrounds nuts1/2; The fruit is ovoid or oblong, with a diameter of 1.5 2 cm; The fruit navel is raised, and its seeds contain starch and fat (oil), which can be used for brewing wine and feed, and oil can be used to make soap; Baked gum can be extracted from shell bucket and bark; Wood is hard and wear-resistant, and can be used for machinery; Fruit can be used as medicine, astringent intestine to stop diarrhea and eliminate breast swelling; Bark and leaf decoction can treat acute bacillary dysentery.
(3) Quercus variabilis: deciduous trees, up to 25 meters high; The cork layer is developed, and the bark is deeply longitudinal and dark gray. Likes light, temperature, drought and cold. The shell bucket is bowl-shaped and contains more than 2/3 nuts; Nuts are spherical, about 1.5 cm in diameter, and the top circle is slightly concave. The main producing area is south of Liaoning Province, especially Shandong, Hunan, Hubei, Jiangxi, Yunnan, Zhejiang and other provinces. Born on the sunny hillside at an altitude of 300,800 meters. Cork is the raw material of cork industry, the shell contains tannin, and the fruit contains starch, which can be used for wine making.
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Method of purchasing acorns
When selecting acorns, we should choose acorns that are not moth-eaten, moldy, mature and complete in grain. Because acorns are generally purchased less at home and are commonly used in bulk processing, it is particularly important to conduct quality sampling to prevent adulteration, deterioration and illegal addition.
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Storage method of acorns
Acorns generally mature from the first ten days of September to the middle ten days of 10. When the shells turn brown and chestnut brown, they can be knocked down with a stick and collected from the ground. Before knocking, it is best to clean up the weeds, stones and clods under the tree.
Acorn is the most difficult seed to store. It is afraid of dryness, dampness, freezing and heat. If the freshly picked acorns are piled up in large piles, they will heat up and sprout every 1 2 days, and will turn black after a long time. In addition, acorns are prone to insects. After being picked back, they should be poured into a bucket or jar filled with cold water for about a day and night, so that the insects can float and be removed. You can also manually pick out the black acorns with wormholes. After taking out the acorns, spread them into a thin layer with a thickness of 5 6 cm, and let them dry naturally in the shade. When they are dry to 90% to 85% of the weight when they were just collected, cut the acorns with a knife to check. If the acorns are smooth and wrinkle-free, they are completely dry. If the rubber kernel has wrinkles, it is too dry to dry.
Common storage methods of acorns include the following three:
① Normal temperature method: If there are not many acorns collected, put them in a breathable bamboo basket or a wattle basket, put them in a shady and ventilated place, and cover them with some leaves for storage. Pay attention to the cold winter, timely increase the cover insulation, in case of freezing.
(2) Sand storage method: When more acorns are collected, you can choose a place in a house with dry land and air circulation or a straw shed. Sprinkle a little water on the ground first, spread wet sand with a thickness of 20-25cm, spread two or three acorns on the sand, and then spread a layer of sand with a thickness of two or three acorns. In this way, it is paved in turn until it is 60 to 70 cm high, even if it is paved. It is easy to get hot when paved too high, which leads to the mildew of acorns. Some people even mixed 1 acorn with 2 parts sand, piled it up to 50.70 cm, and stored it indoors at room temperature.
③ Trench storage method: First find a dry and shady place, and dig a trench 1 m wide and 35cm deep on sunny days. After digging the ditch, first spread a layer of sand with a thickness of15 20cm, then spread acorns with a thickness of 78cm, and then spread the sand with a thickness of 7cm, and then spread them in turn. When it is 45.50cm away from the ditch edge, make a small protruding sand pile on the ditch with sand. In order to ensure good ventilation in the ditch, we can bury 1 every 1 meter with 20 sorghum stalks, and the ventilation handles should be higher than the small sand pile by more than 30 cm. If the dug ditch is very long, in order to prevent the acorns from heating and mildew, and to prevent the diseased acorns from spreading diseases, the long ditch can be divided into 1.6 meters, and each section is separated by 25.30 cm sand. After the whole ditch is completed, a drainage ditch with a depth of 15 20 cm can be dug around the ditch to prevent rainwater from flowing into the ditch. If the temperature rises continuously in spring, in order to prevent acorns from sprouting, snow or ice can be spread on the ditch; In case of continuous low temperature in winter, you can cover the grass to keep warm.
(From "Nuts to Understand", contributed by Cheng Yan of China Agricultural Publishing House)
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