罐头为什么保质期这么长？防腐剂：这锅我不背

黄桃罐头、鲮鱼罐头、午餐肉罐头……记忆中从小吃到大的这些童年美食，甜蜜了许多时光。

然而随着生活水平的提高，人们对罐头食品的疑虑也变多了：罐头为什么会有长达数年的保质期？是否加了防腐剂？对健康有没有什么影响？

图源：视觉中国

其实，罐头只要没有包装破损或鼓包过期，在无菌的密封状态下是非常安全的，完全没有食品安全风险，可以放心食用哦！

罐头最初起源于欧洲，在战争中健康地养活了数百万军队。一起来了解罐头的故事吧。

During the mid-19th century, canned food became a status symbol among middle-class households in Europe, being something of a frivolous novelty.

在19世纪中叶，罐头食品作为一种令人着迷的新鲜事物，成为欧洲中产阶级家庭的地位象征。

Increasing mechanization of the canning process, coupled with a huge increase in urban populations across Europe, resulted in a rising demand for canned food. 

罐头加工技术的提高，加上城市人口的大幅增加，导致欧洲对罐头食品的需求不断增长。

A number of inventions and improvements followed, and by the 1860s smaller machine-made steel cans were possible, and the time to cook food in sealed cans had been reduced from around six hours to thirty minutes.

许多的发明和改进随之而来。到 1860 年代，小机器制造的钢罐也投入使用，而加工密封罐装食物的时间从大约六个小时减少到三十分钟。

家用的迪克西罐封口机 图源：维基百科

Demand for canned food skyrocketed during World War I, as military commanders sought vast quantities of cheap, high-calorie food to feed their millions of soldiers, which could be transported safely, survive trench conditions, and not spoil in transport. 

一战期间，罐头食品的需求量迅猛增加，因为军队长官们需要大量廉价又高热量的食物来养活数百万的士兵。这些食物还必须在战壕条件下生存，能够安全、不变质地运送到战场上。

In 1917, the French Army began issuing canned  French cuisine, such as  Beef Bourguignon and  french onion soup ，while the Italian Army experimented with canned ravioli and spaghetti bolognese. After the war, companies that had supplied military canned food sought to improve the quality of their goods for civilian sale.

1917年，法国军队开始派发罐装法国美食，如勃艮第牛肉和法国洋葱汤；意大利军队则尝试罐装馄饨和肉酱意大利面。战后，供应军用罐头食品的公司开始改进产品质量，试图销售给普通民众。

现代的大部分罐头使用压力罐技术，通过杀菌后排出空气，使罐内真空的方法来实现长时间保存食物的目的。由此我们可以知道，制作罐头的两个关键步骤就在于杀菌与密封。

To prevent the food from being spoiled before and during containment, a number of methods are used: pasteurisation, boiling (and other applications of high temperature over a period of time), refrigeration, freezing, drying, vacuum treatment, antimicrobial agents that are natural to the recipe of the foods being preserved, a sufficient dose of ionizing radiation, submersion in a strong saline solution, acid, base, osmotically extreme (for example very sugary) or other microbially-challenging environments.

为了防止食品在密封之前和密封期间变质，人们使用了许多方法：巴氏杀菌、煮沸（以及其它在单位时间内达到高温的手段）、冷藏、冷冻、干燥、真空处理、使用对保存食品配方天然的抗菌剂、足够剂量的电离辐射、将食物浸入强盐溶液中、或使用酸、碱渗透极端环境（例如非常含糖）或其他微生物难以生存的环境。

Other than sterilization, no method is perfectly dependable as a preservative. For example, the spores of the microorganism Clostridium botulinum (which causes botulism) can be eliminated only at temperatures above the boiling point of water.

除了灭菌之外，没有任何方法能像加防腐剂一样完全可靠。例如，微生物肉毒梭菌（引起肉毒杆菌中毒）的孢子只能在高于水沸点的温度下消除。

图源：Serious Eats

成功冷却后，罐头就制作完成啦！

图源：Countryside

编辑：商桢

实习生：张可意

来源：人民网 维基百科 Ohioline