A Detailed Guide to Sichuan Pepper Harvesting Techniques and Processing and Utilization Methods
Sichuan pepper has a fragrant aroma and is a spice unique to China, also known as dajiao, shujiao, and dianjiao. When ripe, the pericarp of Sichuan pepper turns red to purplish-red, densely covered with warty protruding oil glands. The flowering period is from March to May, and the fruiting period is from July to October. It is mainly produced in Sichuan, Shaanxi, Henan, Hebei, Shanxi, Yunnan and other provinces, among which the quality produced in Sichuan is better, and the yield produced in Hebei and Shanxi is higher.
1. The effects of Sichuan pepper
According to measurements, every 100g of dried Sichuan pepper contains 6.7g of protein, 8.9g of fat, 66.5g of carbohydrates, 28.7g of dietary fiber, 23μg of vitamin A, 140μg of carotene, 0.12mg of thiamine, 0.43mg of riboflavin, 1.6mg of niacin, 2.47mg of vitamin E, 639mg of calcium, 69mg of phosphorus, 204mg of potassium, 47.4mg of sodium, 111mg of magnesium, 8.4mg of iron, 1.9mg of zinc, 1.96μg of selenium, 1.02mg of copper, and 3.33mg of manganese. "Compendium of Materia Medica" records: "Sichuan pepper strengthens teeth, brightens eyes; taken over a long period, it improves complexion, resists aging, prolongs life, and invigorates the spirit." Sichuan pepper is pungent in taste and has the effects of aromatic stomach strengthening, warming the middle and dispelling cold, removing dampness and relieving pain, killing insects and detoxifying, relieving itching and removing fishy odors; it mainly treats vomiting, wind-cold-dampness arthralgia, toothache and other conditions; research has found that Sichuan pepper can dilate blood vessels, thereby playing a role in lowering blood pressure.
Sichuan pepper ranks first among the "thirteen spices" seasonings. It can remove the fishy and gamey odors of various meats, promote saliva secretion, and increase appetite; when stir-frying, put a few grains of Sichuan pepper into the hot oil in the wok, remove them after they turn black, and leave the oil for stir-frying, and the dish will be fragrant; heat Sichuan pepper, vegetable oil, and soy sauce, then pour over cold dressed dishes for a refreshing and delicious taste; when pickling shredded radish, adding Sichuan pepper gives an excellent flavor; if stored grain has been infested by insects, wrap several dozen grains of Sichuan pepper in cloth and put them in, and the insects will crawl away on their own or die; drinking Sichuan pepper water can expel parasites; placing several dozen fresh Sichuan peppers in a kitchen cabinet will keep ants from entering; placing some Sichuan pepper beside food and on meat will keep flies from biting; when deep-frying food, if the oil heats to the boiling point, it will overflow from the pot, but if a few grains of Sichuan pepper are added, the boiling oil will immediately subside; adding an appropriate amount of Sichuan pepper powder to oil or fat can prevent it from developing a rancid smell; if toothache is caused by hot or cold food, placing one grain of Sichuan pepper on the aching tooth will gradually make the pain disappear.
2. Harvesting of Sichuan pepper
The harvesting period of Sichuan pepper varies depending on the variety and site conditions. Generally, when the pericarp of Sichuan pepper appears purplish-red or pale red, the suture line of the pericarp protrudes, part of the pericarp has split open, the seeds are black and glossy, and a rich numbing aroma is released, this is the best harvesting period. If picked too early, the pericarp is thin, the color is dark, the oil content of the kernel is low, and the taste is poor; if picked too late, the fruit dry-cracks and the kernels fall out, affecting returns. Practice has shown that picking 10 days early will reduce the yield of Sichuan pepper by 10%-20%. In years with excessive rainfall, Sichuan pepper will split open and drop its kernels ahead of time, so it should be harvested promptly. After the fruits of some Sichuan pepper varieties mature, the pericarp easily splits open and the seeds scatter, so harvesting should be completed within 1 week after maturity to avoid unnecessary losses. For some varieties such as Dahongpao, because the fruit does not split open after maturity, the harvesting time can be appropriately delayed.
Sichuan pepper should be harvested in clear weather, avoiding rainy days, so as to prevent difficulty in drying and adverse effects on color and flavor that lead to reduced quality. The harvesting order should begin with Sichuan pepper from sunny, low-altitude orchards, and finally harvest Sichuan pepper from shaded, high-altitude orchards. For a single tree, first pick the outer parts and then the inner parts, first the lower parts and then the upper parts, and do not miss any. In the first leaf axil below a large cluster of Sichuan pepper, there is a plump bud; this bud is the fruiting bud for the next year and should not be removed. However, the first bud below the fruit cluster on a weak branch develops insufficiently, and only the second or third bud develops robustly. When picking, the first bud can be removed while retaining the second and third buds, which serves as a minor pruning. Leaf-cluster branches have no strong buds, only thin and weak buds, and can hardly form flower-bearing branches, so during picking most leaf-cluster branches should be appropriately removed, generally retaining only 1/3 of the leaf-cluster branches. Leaf-cluster branches in positions lacking branches should be appropriately retained to cultivate them into robust fruiting branches, fill the space, and expand the fruiting area.
3. Processing of Sichuan pepper
(1) Dried Sichuan pepper. After harvesting Sichuan pepper, first spread it out in the sun for 1 day, then put it into drying sieves and send it into a drying room for baking, with a loading thickness of 3cm-4cm. At the beginning of baking, the temperature of the drying room should be controlled at 50°C-60°C; after 2.5h, raise the temperature to 80°C, and bake for another 8h-10h. When the moisture content of the Sichuan pepper is less than 10%, it can be taken out. During baking, attention should be paid to moisture removal and turning the sieves. At first, remove moisture and turn the sieves once every 1h; afterward, as the moisture content of the Sichuan pepper decreases, the interval for moisture removal and turning the sieves can be appropriately extended. After the Sichuan pepper is dried, take it out together with the drying sieve, sieve out seeds, branches, leaves and other debris, and bag it according to standards to obtain the finished product. The bagged Sichuan pepper should be stored in a cool, dry place.
(2) Sichuan pepper powder. Put clean dried Sichuan pepper into a frying pan and stir-fry over low heat, stirring continuously while frying, or use a roasting machine to roast at 120°C-130°C for 6min-10min, take it out and let it cool naturally to room temperature, crush it with a grinder, pass it through an 80-mesh to 100-mesh sieve, quantitatively fill it into plastic film composite bags; finally seal the opening.
(3) Sichuan pepper oil. Use fresh Sichuan pepper as the raw material. Pour edible oil into a pot, heat it until it boils and the oil foam disperses, then stop heating. When the oil temperature drops to 120°C, add Sichuan pepper, with a ratio of rapeseed oil to Sichuan pepper of 1:0.5. Immediately cover and seal to reduce the volatilization of aromatic substances. After cooling, use a centrifuge at a speed of 2000r/min to centrifuge, remove fruit residue and other impurities, and finally bottle it.
(4) Sichuan pepper seed oil. Sichuan pepper seeds are rich in oil (27%-31%). As a by-product of Sichuan pepper production, they have abundant sources, low prices, and great development potential. After the Sichuan pepper seeds are cleaned, dehulled, and separated into kernels, the oil can be extracted by dry pressing and solvent extraction or by direct solvent extraction. The resulting crude oil, after refining and dewaxing, becomes a high-quality edible oil with a unique flavor, rich aroma, and a slight numbing spiciness. It can also be used as a raw material for refined salad oil and other high-grade edible oils. As a semi-drying oil, Sichuan pepper seed oil is an excellent industrial oil and can be used as a raw material for producing coatings, soap, sulfonated oil, lubricants, etc. It can also be used as a raw material for fine chemical products such as ore flotation agents, plastic plasticizers, and leather fatliquoring agents.
Sichuan pepper seed oil contains about 90% unsaturated fatty acids. In the refined oil, the linolenic acid content is as high as 36.2%, and the linoleic acid content reaches 33.7%. These unsaturated fatty acids have important functions for human growth and development, especially α-linolenic acid, which can play a role in anti-thrombosis and lowering blood lipids, promoting fat metabolism, and preventing tumorigenesis and inhibiting the metastasis of tumor cells. Methods such as urea inclusion or supercritical carbon dioxide extraction can be used to enrich or separate and purify the α-linolenic acid in Sichuan pepper seed oil, producing high-purity α-linolenic acid preparations with special medicinal value.
Sichuan pepper seed oil meal and defatted Sichuan pepper kernels contain 31%-48% protein and a small amount of minerals, with the rest mostly crude fiber. It is an excellent protein feed and can be utilized as a plant protein resource to produce Sichuan pepper edible protein similar to soybean protein and its products.