一是干选法。用筛子使大豆通过震动筛把杂物分离出去。

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

二是湿选法。湿选是根掂大豆与泥沙等杂物比重不同的原理用水漂选。具体方法是将大豆倒入浸泡池内，加水后由于大豆中的杂物、浮豆、破口豆、霉烂豆、虫蛀豆等的比重小于水，因而漂浮在水面，然后用笊篱捞出来。但比重大于水的铁屑、石子、泥沙等杂物，仍与大豆同时沉淀在水里。

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

大豆组织中的蛋白质是一-种胶体大豆用水浸泡后，可使白质胶体吸收水分而膨胀，有利于把蛋白质提取出来。此外，大豆通过浸泡后，组织软化，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。大豆浸泡过度或浸泡不足都会影响豆制品的产品得率。浸泡适度可使蛋白质外的膜由硬变脆，在研磨时能充分粉碎，使蛋白质石磨大限度地游离出来。如浸泡过度，蛋白质外膜变软，不易磨碎，会影响成品得率；如浸泡不足，蛋白质外膜仍很坚硬。浸泡是否适度的办法是，把浸泡后的大豆掰成二瓣，如豆瓣内侧已基本呈平面，中心部化略呈浅凹面，则是漫泡适度；如豆瓣内侧完全呈平面，则浸泡过度；如豆瓣内侧尚有深的凹陷，为浸泡不足。浸泡程度也因季节不同而异。夏秋季节，气温铰高，漫泡宜不足，不宜过度；冬春季节，气温偏低，浸泡可稍过度。为使大豆均匀吸水，在浸泡期间，每隔2小时左右，应将大豆上下翻动一次。

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.

二是浸泡时间。大豆浸泡时间的长短，应根据气温、豆种、水质及成品等因素而定，但主要因素是温度，气温越低，大豆的浸泡时时间越长。一般在8小时左右。

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 值对浸泡的影响。大豆浸泡时间过长，由于微生物的繁殖，泡豆的水会变酸，特别在夏天，这种现象更容易发生。在酸性的条件下，大豆蛋白质容易变性败坏，进而影响产量和质量，严重时还会导致坏浆现象，不能制成豆制品。所以，在大豆浸泡后，应当先把水沥尽，然后再用清水冲洗，去除酸水，改变 pH 值。在夏天，除了用清水冲洗外，还需将大豆放在竹箕里将表皮擦碎，再次用清水冲洗，以便把含在表皮内的酸水或微生物冲洗干净，从而减少酸度和微生物对蛋白质的破坏。

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数量，顺序地进行。先浸泡，先成熟，先上磨；后浸泡，后成熟，后上磨。如果一次浸泡，同时成熟，分批上磨，或者是分批浸泡，分批成熟：，一次上磨，由于大豆组织的软化程度不同，都会影响大豆组织的粉碎解和蛋白质的溶出率。从大豆浸泡到磨碎，大致要经过一淘、二冼、三搽、四沥等过程。一淘就是浸泡时要定时搅拌；二洗，浸泡完毕要冲洗干净；三擦，就是把浸泡过的大豆用工具把表皮擦破，表皮内所含的微生物和酸水流出；四沥，即用水冲洗，把余水沥尽。

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.