Concerned consumer
I always use blue toilet paper because it matches my bathroom decor. However, a friend told me that I should only use white, because coloured paper is more damaging to the environment. My local supermarket sells a huge variety of colours with any number of patterned varieties too. Is it true that some varieties are more environmentally damaging? And if so, why? Is kitchen roll even worse than toilet paper?
鈥� If your friend means that the dyes are ecologically harmful, forget it. Chemically active groups on the dye molecules cling to the cellulose, which is why the colours don鈥檛 run and leave you fundamentally decorative after you apply them. The dyes are like a mousetrap that has caught a mouse: the mouse, in demonstrating its bite, has become harmless. Much as the trap is hard to reset, the dyes are hard to release from the paper.
Dyes are expensive, and toilet paper requires only traces, so even the most environmentally unaware manufacturer will prefer safe dyes that are simple to handle, and can be applied stingily, typically in parts per million. When the paper reaches the sewage works, the immobilised molecules soon succumb to bacteria, so they do not accumulate in the environment.
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If you doubt this, buy a job lot of toilet paper, fold wads of say 10 squares, each of a single colour, bury them separately in moist garden soil, and in a month or two exhume them and observe the result. In good soil you will do well even to detect your test pieces after the earthworms have done their work.
Much the same applies to kitchen paper, except that its strength while it is wet may mean it breaks down more slowly. Its persistence probably does more to provide bacteria with a durable home than harms the environment in any way.
Anyway, what about the bleaches necessary for producing white toilet paper? If you really want to be politically correct, go for garbage grey.
Jon Richfield
Somerset West, South Africa
鈥� Wood is brown. Unbleached paper is brown. White paper improves the contrast between text and background to aid reading, so most people prefer it. To make paper white, it is usually bleached with chlorine, which can form carcinogenic dioxins. The paper industry has substantially cut down the quantity of dioxin by-product it produces, and there are initiatives to eliminate it totally by using only hydrogen peroxide and ozone bleaches, which are somewhat more expensive.
Incidentally, what we consider brilliant white is actually slightly blue. Many papers therefore contain fluorescent whitening agents (FWAs), that re-emit UV light as blue light, plus some blue dye. You may have seen clothes and paper containing FWAs glowing under 鈥渂lack lights鈥�.
Brady Hauth
Salt Lake City, Utah, US
Pickled poser
I love pickles and chutneys. But I鈥檇 like to know what nutrition is conserved and what is lost when vegetables are prepared and preserved in this manner.
鈥� Pickles and chutneys were originally a means of preserving fruit and vegetables using a combination of heat processing to kill bacteria, fungi and yeasts, with added sugar, acid (in the form of vinegar) and salt acting as preservatives.
In some cases the raw fruit or vegetable is fermented for weeks or months in a brine containing lactobacillus bacteria, which produce the natural preservative lactic acid. Mango and cabbage can be preserved in this way. This also develops the texture and flavour of the fruit or vegetable.
Vitamins, minerals and nutrients are lost when the cooked or fermented plants are washed during processing. Unstable vitamins start to break down soon after harvesting, a process which is accelerated at high cooking temperatures and at the acidic pH typical for these types of product.
Some pickles and chutneys are prepared in oil rather than a sweet sauce, and there is generally less vitamin breakdown in the oily type because cooking is less severe. If we take mango as an example, the raw fruit contains about 40 milligrams of vitamin C per 100 grams of fruit, while oily mango chutney only contains about 1 milligram and in sweet chutney vitamin C is barely detectable.
Mark Wareing
Sedbergh, Cumbria, UK
鈥� Many pickles are lightly cooked, or even just blanched or fermented. But chutneys are nutritionally different, as they are cooked almost as aggressively as jam. Both are products of pre-refrigerator preservation technologies, but their preparation and storage cause nutrient loss in four main ways: leaching, heating, oxidation and degradation. The main losses are of soluble or unstable nutrients such as some vitamins, antioxidants and minerals.
Pickling fluid itself causes hardly any degradation. How much leaching occurs depends on how the pickles are cooked and stored in liquid. For instance, large chunks leach less than grated material, which has a larger surface area. Using pickle fluid in soups or stews is a tasty way to reduce this loss. Bulk nutrients such as starches and proteins are not much affected, and in fact processing may improve their digestibility.
In modern pickling mild preservatives prevent decay. Manufacturers also rely on opened containers being kept cold to slow degradation and decay. Darkness also protects light-sensitive vitamins such as A and C. To prevent oxidation, jars of preserves should be closed tightly and used soon after opening.
Pickles have an honourable nutritional history. As well as simply combating starvation, the likes of sauerkraut have prevented many a case of scurvy during northern winters.
Antony David
Cork, Ireland
This week鈥檚 question
Fasten seatbelts
I recently flew back from holiday on a large airliner. During the flight we encountered some severe turbulence. Food and drink went flying, overhead lockers opened, people were screaming and crying, and even the cabin crew were alarmed, crawling along the aisle to take refuge. The plane even seemed to fall vertically for about 5 seconds. How much danger were we in? It felt as if the plane was going to fall out the sky. Has that ever happened?
Brian Jackson
Birmingham, UK