Look: Look at the color of the flour. The color of flour is the basis of determining the grade of flour. High-grade flour, white and delicate in color, without mottled and chaff stars; Low-grade flour is inferior. Flour is creamy or yellowish because there are many combinations of durum wheat, and its gluten content is generally high.
The second smell: good flour smells like wheat, while flour stored at high temperature or for a long time will have an odor and sticky taste because of the aging of grain. Those with a keen sense of smell can smell the smell directly with a small amount of flour to distinguish the advantages and disadvantages; If you have a bad sense of smell, you can add hot water to the flour and stir it to smell it. If it smells like straw and wheat, it means that the processing time of flour is not long, the quality is good, and too many additives are not added. If you smell strong dust, it must be old or there are too many substances exceeding the standard.
Three products: put a little dry flour in your mouth by hand. If there is tartar phenomenon, it means that the flour has high sand content; If the taste is sour, it is judged that the acidity of flour is high. Made into cooked food to flavor, normal flour made into cooked food tastes like starch "fragrant" and tastes delicate. If the taste is not good, it means that the flour has a high sand content.
Four rubs: grab a handful of flour and rub it a little hard. If the flour is powdery and has no graininess, it will disperse and not agglomerate after being loosened by hand, so it can be judged that the water content of flour is moderate. If it is easy to agglomerate, agglomerate and stick after kneading by hand, it can be judged that the flour has high water content, and it is easy to get hot, moldy and go bad in the weather of soup. Good flour is also soft when twisted by hand, and it is problematic to feel too slippery.
"Sodium formaldehyde sulfoxylate", whose chemical name is sodium formaldehyde sulfoxylate, has strong non-original property at high temperature, which makes it bleaching. Its aqueous solution begins to decompose into harmful substances above 60℃ and into toxic gases such as formaldehyde, carbon dioxide and hydrogen sulfide below 120℃. These poisonous gases can cause headaches, fatigue and loss of appetite. People who have been exposed to formaldehyde for a long time will have tumors in the nasal cavity or nasopharynx, and the risk of cancer will increase significantly. Studies have shown that oral administration of 10 ~ 20ml formaldehyde and inhalation of several mouthfuls of hydrogen sulfide can lead to human death. "Hanging white block" is not a food additive, but is mainly used as a dye transfer agent in the printing and dyeing industry.