The meaty, smoky aromas of a juicy steak grilling on a BBQ are one of the most memorable and prevalent smells of summer. Steaks are typically “seared” during grilling by rapidly heating the surface. I’ve heard a lot chefs recommend searing a steak to improve its flavour by browning the surface; although, it is often claimed that searing also seals the meat against moisture loss . It doesn’t take extensive research to show that searing does indeed caramelize the surface—we have enjoyed tasty steaks with a crispy, crusty exterior at home and in restaurants. But does searing really help retain the meat juices? That’s a question not many can easily answer.
Past researchers have reported that the final internal temperature is extremely critical in affecting the tenderness and weight loss of meat . Furthermore, the retention of meat juices along with the shrinkage of collagen is believed to cause the tenderization effect of cooking meat for a long period of time at low temperatures . In fact, seared meat showed ~3.4% more weight loss compared to unseared meat . More importantly, a recent study has found that fattier meat retain their meat juices better than leaner cuts of meat, regardless of being seared . This is primarily because water loss occurs more rapidly than fat loss . Leaner meats contain more protein and less fat; therefore, leaner cuts will contain slightly more water on a per weight basis as water is a component of protein (but not fat) [4 ].
Cooked meats contain volatile compounds that are derived from lipid and water-soluble precursors. These compounds provide the roasted, boiled, fatty and characteristic meaty aromas associated with all cooked meats . Table 1 lists the different volatile compounds that are associated with various aromas.
Table 1 Linking various aromas to their sources 
Traditionally, food scientists and agricultural chemists were generally the ones answering questions such as whether searing meat to seal in juices is fact or fiction. However, the establishment of molecular gastronomy, which aims to allow us to cook better by understanding the chemical or physical reactions during cooking, has also contributed to providing answers to these types of questions . Thus molecular gastronomy has overhauled some “cooking rules” that seem right but are actually wrong, and have resolved that searing meats does not seal it against moisture loss .
So what does all this mean to the average cook? The chefs were right all long—quickly searing a steak will give it the aromatic carmelized flavours, while the short time on the grill will minimize its weight loss and retain its juiciness.
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 USDA. (2011, May 23). Water in Meat and Poultry [Online document]. Available: http://www.fsis.usda.gov/factsheets/Water_in_Meats/index.asp
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 T. Hervé, translated by J. Gladding, Kitchen Mysteries: Revealing the Science of Cooking. USA: Columbia University Press, 2010.