Idea
There are thousands of recipes for liquid marinades. Many ingredients are used in them. Most frequently it is a mixture of salty ingredients, acid ingredients, oil, herbs and spices. For red meat, it is recommended it to marinate it at least overnight and not more than 24 hours. While the meat is marinated, it should be placed in a fridge. What is the reasoning behind this and what effects individual ingredients have?
Salt
Salt has multiple effects. It tenderizes the meat, makes it juicier, and helps to increase absorption of flavors from herbs and spices.
The process of immersing a meat in water containing large amounts of salt is called brining. Brining has two initial effects. First, salt disrupts the structure of the muscle filaments. A 3% salt solution (30 grams per liter) dissolves parts of the protein structure that supports the contracting filaments. 5.5% solution (55 grams per liter) partly dissolves the filaments themselves. Second, the interaction of salt and proteins result in a greater water-holding capacity in the muscle cells, which then absorb water from the brine. The inward movement of salt and water and disruption of the muscle filaments into the meat also increase its absorption of aromatic molecules from any herbs and spices in the brine. The meat’s weight increases by 10% or more. When cooked, the meat still looses around 20% of its weight in moisture, but this loss is counterbalanced by the brine absorbed, so the moisture loss is effectively cut in half. In addition, the dissolved muscle filaments can’t coagulate into normally dense aggregates, so the cooked meat seems more tender.
Soy sauce is often used instead of table salt in marinade recipes. It has normally a salt content between 14%–18%.
Acid ingredients
Acid ingredients in marinades weaken muscle tissue and increase the ability to retain moisture. They are also added to balance the saltiness. Examples of acid ingredients: wine, beer, fruit juices, vinegar, mustard and yogurt.
Meat tenderizers
Meat tenderizers are enzymes, which break protein molecules into smaller molecules. Tenderizers penetrate into the meat even more slowly than acids, a few millimeters per day. Most of the tenderizing chemical reactions occur while the meat is cooked. The result of this method of preparation is mealy surface and unaffected interior. Meat should not be immersed in a tenderizer for more than 30 minutes. Otherwise, the surface becomes too mealy. Papaya, pineapple, fig, kiwi and ginger contain meat tenderizing enzymes.
Oil
Most of the flavor molecules dissolve much better in oil than in water. Oil also releases the flavor molecules slower than water. Oil thus prevents them from escaping while the meat is cooked and helps to keep the flavor molecules in the meet until it is chewed. Because meat is 75% water, oil should be added to the marinade any time when herbs and spices are added. Melted butter and fats have similar effect.
Oils encourage growth of deadly bacteria Clostridium botulinum, whose spores can survive brief boiling and germinate when protected from the air. Most herbs and spices do not provide enough nutrients for botulism bacteria to grow on, but garlic does. Refrigerator temperatures prevent bacterial growth.
Timing
Marinades penetrate slowly into the meat. It takes about 15 minutes to seep in 1 millimeter into the read meat and approximately 1 hour to penetrate 2 millimeters. Afterward, the penetration is even slower. Therefore, most of the recipes advise to marinate red meat overnight (if no tenderizers are present). Thicker slices of meat need to be marinated longer in order for marinade to distribute over the whole volume.
Fish meat consists of more delicate proteins. All chemical processes described above take place faster than in red meat. Fish should not be in a marinade longer than several hours.
References
- McGee on Food and Cooking: An Encyclopedia of Kitchen Science, History and Culture by Halod McGee.
- Cook & Chemist by Eke Marien & Jan Groenewold (www.cookandchemist.com).