1. (2023高二下·奉贤月考)  完形填空

Unwrapping your shopping to find you have bought mouldy (发霉的) bread, rotten fruit and sour milk could soon become a thing of the past, thanks to the range of emerging 'active packaging' technologies. While traditional packaging simply 1  a barrier that protects food, active packaging can do a lot more. Some materials 2  with the product to improve it in some way, or provide better information on the state it is in. 3 , they may absorb oxygen inside a wrapper to help prevent food spoilage or show whether potentially dangerous foods like red meat and chicken have been stored at unsafe temperatures. 

One of the new breed of packaging technologies that have just gone on the market in France is a ‘time temperature indicator'. Stores where the product has already been introduced report that far fewer consumers are returning 4 food. The indicator is basically a label that 5 the temperature a package has been kept at and for how long. The label has a dark ring around a lighter circle. The central ring contains a chemical which polymerises (聚合), changing colour as it does so from 6 to dark. If the package stays cool, the reaction is slow, but increasing the temperature speeds up the polymerization. When the inner circle darkens, it means the product is no longer 7 fresh.

Smart packaging can also control the 8 of the atmosphere inside a container. For instance, the make-up of oxygen (O2) and carbon dioxide (CO2) within packaged vegetables will influence their freshness. This can be hard to control in a sealed package, since vegetables 9 more oxygen and give off more carbon dioxide as the package gets warmer. A firm in California is trying to solve the problem with a wrapper it calls ‘Intelimer' which changes its permeability (渗透) as the temperature changes in a way that keeps different produces at their best O2/CO2 10 .

Decay can also be 11 by controlling the environment inside a package with an ‘oxygen scavenger'(清除剂). 12 , this is achieved by placing a small bag filled with iron powder in the package — any oxygen in the package is consumed by the iron as it oxidises. However, consumers don't 13 finding small bags marked ‘Don't eat in their food', so a company in New Jersey is making a wrap that itself consumes oxygen. The 14 includes an inner layer of an oxidisable polymer (聚合物) that traps oxygen in the same way as iron.

It is predicted that between 20 and 40 per cent of all food packaging will soon be 15 .