Very interesting, I never realized that it takes more or less energy to heat one gram of water one degree, depending on the initial temperature. Wikipedia explains it quite well <http://en.wikipedia.org/wiki/Calorie>. I guess the conventional food calorie is the thermochemical calorie? Understanding the metric system seems to teach a lot about science on its own :-).
I think that people would be more likely to switch to joules for food energy if the calorie was more imperial (and thus worse) to begin with. For example, if a calorie was the amount of energy it took to heat one ounce of water one degree fahrenheit, it would have much more criticsm than its current definition. Regardless, joules really should be switched to. Years ago (I've lived in America most of my life) I saw kJ and Calories on a food package, and thought that kJ must be some old, deprecated measurement. It is quite the opposite :-). Cheers, Teran On Sat, Jan 31, 2009 at 06:06, Pat Naughtin <[email protected]> wrote: > On 2009/01/31, at 3:37 PM, David wrote: > > How long after the initial metrication would it take for food companies to > start using "joules/kilojoules" instead of "calories?" (They would use > kilojoules and not just joules, correct?) Even if people don't use > centimeters or kilograms in their daily lives they've at least heard of > them. But I don't think anyone outside of the scientific community has heard > of the "joule." > > So would calories stay or would those be changed as well? Do they use > joules/kilojoules on food packages in metric countries? > > Dear David, > In Australia, people who package foods are legally required to use > kilojoules for the energy content of the food. Further, they are required to > give a figure in kilojoules for a normal serving and for 100 grams of the > food. > Food nutrients have to be listed in a Nutrition Information Panel. The NIP > provides information on seven nutrients: energy (kilojoules), protein, total > fat, saturated fat, total carbohydrates, sugars and sodium. Cholesterol > content does not have to be listed unless a claim is made. You can get full > information, for the state of Victoria, which is typical, > from > http://www.betterhealth.vic.gov.au/bhcv2/bhcarticles.nsf/pages/Food_labels_explained?OpenDocument > There are two main problems with calories, Calories, gram-calories, > kilogram-calories, kilocalories, and kiloCalories etc. The first is that > these words are not supported internationally so that individual companies > might use different spellings for reasons best known to themselves. From the > six examples that I have given here a kiloCalorie is a million times larger > than a calorie because of the spelling. A second problem is that calories > vary from one temperature to another. A 20 °C calorie is not the same as a > 38 °C calorie for example. This problem with temperatures and calorie > measurements has been known since the 1860s or 1870s when the British > Association for the Advancement of Science decided to throw out all of the > different calories in favor of the joule that is always the same; the joule > has been the internatioally accepted unit for all forms of energy since > 1899. A joule is not much energy — you use a joule of energy when you pick > up a medium sized apple (1 newton) and place it on a shelf (1 metre high) — > so it is usual to talk about kilojoules of energy, or megajoules, or > gigajoules, … > By the way, the word, calorie, became popular in the USA after 1919 when Dr > Lulu Hunt-Peters wrote a book about the calorie content of food. Leaving > aside the issue of the garbled quantity (food energy) with the measuring > word, calorie, Dr Hunt-Peters defined a calorie as the amount of heat needed > to heat 4 pounds of water by 1 degree Fahrenheit. Sometime during the last > 90 years someone changed the spelling of Dr Hunt-Peter's calorie to Calorie > (a Calorie is 1000 times larger than a calorie). > With respect to timing, i.e. your question, 'How long does it take?' this > depends on how your government reacts to your nutritionists who will fight > tooth and nail to keep their old calorie words, even when they know about > their unreliability, because they have built up a strong mindset that > revolves around a set of conversion factors. They have memorised things like > 'how many calories there are in a slice of bread' and 'how many calories an > active woman needs each day' and they are loath to give up these habits. In > Australia, it took about 30 years for the dust to settle (1970 to 2000) but > there are still some out-liers. The success here was, I believe due to the > fact that all foods were labelled as I mentioned previously and the > nutritionists simply got worn down by the constant questions along the lines > of: 'you told me to eat xxx calories of bread but the packet is in > kilojoules, how do I know what to do?' > Cheers, > > Pat Naughtin > PO Box 305 Belmont 3216, > Geelong, Australia > Phone: 61 3 5241 2008 > Metric system consultant, writer, and speaker, Pat Naughtin, has helped > thousands of people and hundreds of companies upgrade to the modern metric > system smoothly, quickly, and so economically that they now save thousands > each year when buying, processing, or selling for their businesses. Pat > provides services and resources for many different trades, crafts, and > professions for commercial, industrial and government metrication leaders in > Asia, Europe, and in the USA. Pat's clients include the Australian > Government, Google, NASA, NIST, and the metric associations of Canada, the > UK, and the USA. See http://www.metricationmatters.com for more metrication > information, contact Pat at [email protected] or to get > the free 'Metrication matters' newsletter go > to: http://www.metricationmatters.com/newsletter to subscribe. >
