包装最重要的功能是对所有包装商品的品质保护，也就是说使商品在储存、运输和销售整个流通过程中，经过不同的环节，处于不同的环境，都不至损坏、散失、渗漏和变质。
The most important function of packaging is to protect the quality of all packaged goods. That is to say, during the whole circulation process of storage, transportation and sale, the goods will pass through different links and be in different environments without damage, loss, leakage and deterioration.
这就要求制袋过程中封口必须具有一定的强度和密封性能，能够承受一定重量内容物的压力，确保商品在流通过程中不开裂、泄漏，达到保护商品的目的。而制袋是交付用户前的最后一道生产工序，品质的控制更为重要。
This requires that the sealing process must have a certain strength and sealing performance, can withstand the pressure of a certain weight of content, ensure that goods do not crack and leak in the circulation process, to achieve the purpose of protecting goods. Bagging is the last production process before delivery to customers, and quality control is more important.