From: mrou...@shaw.ca   
      
   On Monday, December 19, 2022 at 7:56:22 AM UTC-7, Martin Brown wrote:   
   > On 18/12/2022 01:00, RichD wrote:    
   >    
   > > How do they measure the calorie content of food items?   
   > Bomb calorimetry. Burn it in oxygen at constant volume which makes the    
   > reaction go very fast.    
      
   A bomb calorimeter uses a high pressure of oxygen, not to make the reaction go   
   fast, but to make sure the sample burns completely. This is extremely   
   important because you can't calculate the heat of reaction very accurately   
   otherwise. For analytes that    
   don't burn well, top-notch calorimetry labs will collect the ash and subject   
   it to further analysis so that they can correct for the presence of poorly (or   
   non-)combustible material in the sample. For example, there is a necessary   
   correction for samples    
   that are high in calcium carbonate because the heat causes the carbonate to   
   decompose into carbon dioxide and calcium oxide, which is an endothermic   
   process. This process is clearly not relevant to someone eating a high-calcium   
   food, so it has to be    
   corrected for. (Along with obvious high-calcium foods like dairy products,   
   this will be an issue for mechanically separated meat, which contains a lot of   
   tiny bits of bone. Enjoy your cheap hot dogs and chicken nuggets.) Ash from   
   such samples would    
   therefore be analyzed for calcium content so that the appropriate correction   
   could be made to the measured heat. Having said that, I'm not sure how many   
   food labs would be that careful.   
      
   Marc Roussel   
      
   --- SoupGate-Win32 v1.05   
    * Origin: you cannot sedate... all the things you hate (1:229/2)