一是干選法。用篩子使大豆通過震動篩把雜物分離出去。

One is dry selection. Use a sieve to make the soybeans pass through a vibrating sieve to separate out the impurities.

二是濕選法。濕選是根掂大豆與泥沙等雜物比重不同的原理用水漂選。具體方法是將大豆倒入浸泡池內，加水后由于大豆中的雜物、浮豆、破口豆、霉爛豆、蟲蛀豆等的比重小于水，因而漂浮在水面，然后用笊籬撈出來。但比重大于水的鐵屑、石子、泥沙等雜物，仍與大豆同時沉淀在水里。

Second, wet separation. Wet separation is based on the principle of different proportion of soybean and sediment. The specific method is to pour the soybean into the soaking pool, and after adding water, because the proportion of impurities, floating beans, broken beans, moldy beans, and moth eaten beans in the soybean is less than that of water, they float on the water surface, and then they are fished out with a fence. However, iron filings, stones, sand and other debris with a specific gravity greater than that of water still precipitate in the water together with soybeans.

泡豆

Pickled bean

大豆組織中的蛋白質是一-種膠體大豆用水浸泡后，可使白質膠體吸收水分而膨脹，有利于把蛋白質提取出來。此外，大豆通過浸泡后，組織軟化，便于磨碎。

The protein in soybean tissue is a kind of colloid. After soaking in water, the colloid of white matter can absorb water and expand, which is helpful to extract protein. In addition, after soaking, soybean tissue softens and is easy to grind.

一是浸泡程度。大豆浸泡過度或浸泡不足都會影響豆制品的產品得率。浸泡適度可使蛋白質外的膜由硬變脆，在研磨時能充分粉碎，使蛋白質石磨大限度地游離出來。如浸泡過度，蛋白質外膜變軟，不易磨碎，會影響成品得率；如浸泡不足，蛋白質外膜仍很堅硬。浸泡是否適度的辦法是，把浸泡后的大豆掰成二瓣，如豆瓣內側已基本呈平面，中心部化略呈淺凹面，則是漫泡適度；如豆瓣內側完全呈平面，則浸泡過度；如豆瓣內側尚有深的凹陷，為浸泡不足。浸泡程度也因季節不同而異。夏秋季節，氣溫鉸高，漫泡宜不足，不宜過度；冬春季節，氣溫偏低，浸泡可稍過度。為使大豆均勻吸水，在浸泡期間，每隔2小時左右，應將大豆上下翻動一次。

One is the degree of immersion. Excessive or insufficient soybean soaking will affect the yield of soybean products. Appropriate immersion can make the outer membrane of protein from hard to brittle, which can be fully crushed when grinding, so that the protein stone can be largely free. If it is soaked too much, the outer membrane of protein will become soft and not easy to grind, which will affect the yield of finished product; if it is not soaked enough, the outer membrane of protein will still be very hard. The method to determine whether the soaking is appropriate is to break the soaked soybean into two pieces. If the inner side of the bean is basically flat, and the center is slightly concave, then the soaking is moderate; if the inner side of the bean is completely flat, then the soaking is excessive; if the inner side of the bean is still deep concave, then the soaking is insufficient. The degree of soaking also varies with seasons. In summer and autumn, when the temperature is high, it should be insufficient and not excessive; in winter and spring, when the temperature is low, it can be slightly excessive. In order to make soybean absorb water evenly, the soybean should be turned up and down every 2 hours during soaking.

二是浸泡時間。大豆浸泡時間的長短，應根據氣溫、豆種、水質及成品等因素而定，但主要因素是溫度，氣溫越低，大豆的浸泡時時間越長。一般在8小時左右。

The second is soaking time. The soaking time of soybean depends on temperature, seed, water quality and finished product, but the main factor is temperature. The lower the temperature is, the longer the soaking time is. It's usually about 8 hours.

三是pH 值對浸泡的影響。大豆浸泡時間過長，由于微生物的繁殖，泡豆的水會變酸，特別在夏天，這種現象更容易發生。在酸性的條件下，大豆蛋白質容易變性敗壞，進而影響產量和質量，嚴重時還會導致壞漿現象，不能制成豆制品。所以，在大豆浸泡后，應當先把水瀝盡，然后再用清水沖洗，去除酸水，改變 pH 值。在夏天，除了用清水沖洗外，還需將大豆放在竹箕里將表皮擦碎，再次用清水沖洗，以便把含在表皮內的酸水或微生物沖洗干凈，從而減少酸度和微生物對蛋白質的破壞。

The third is the effect of pH value on soaking. Soybean soaking time is too long, because of the propagation of microorganisms, the soaking water will become sour, especially in summer, this phenomenon is more likely to occur. Under acidic conditions, soybean protein is easy to denaturate, and then affect the yield and quality, even lead to bad pulp phenomenon, can not be made into soybean products. Therefore, after soybean soaking, the water should be drained first, and then washed with clean water to remove acid water and change the pH value. In summer, in addition to washing with clean water, it is also necessary to put the soybean in the bamboo dustpan to scrape the epidermis, and then wash with clean water again, so as to clean the acid water or microorganisms contained in the epidermis, so as to reduce the damage of acidity and microorganisms to protein.

四是浸泡程序。浸泡大豆要按上磨的數量，順序地進行。先浸泡，先成熟，先上磨；后浸泡，后成熟，后上磨。如果一次浸泡，同時成熟，分批上磨，或者是分批浸泡，分批成熟：，一次上磨，由于大豆組織的軟化程度不同，都會影響大豆組織的粉碎解和蛋白質的溶出率。從大豆浸泡到磨碎，大致要經過一淘、二冼、三搽、四瀝等過程。一淘就是浸泡時要定時攪拌；二洗，浸泡完畢要沖洗干凈；三擦，就是把浸泡過的大豆用工具把表皮擦破，表皮內所含的微生物和酸水流出；四瀝，即用水沖洗，把余水瀝盡。

The fourth is soaking procedure. Soaking soybean should be carried out in order according to the quantity of grinding. Soak first, mature first, grind first; soak later, mature later, grind later. If soaking in one time, ripening at the same time, grinding in batches, or soaking in batches, ripening in batches: grinding in one time, due to the different degree of softening of soybean tissue, it will affect the comminution of soybean tissue and the dissolution rate of protein. From soybean soaking to grinding, it generally goes through the process of one washing, two washing, three brushing and four leaching. The first washing is to stir regularly when soaking; the second washing is to wash thoroughly after soaking; the third wiping is to scrape the surface of soaked soybean with tools, and the microorganisms and acid water contained in the surface will flow out; the fourth leaching is to wash with water, and drain the remaining water.