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Present in the chloroplasts and mitochondria of all parts of an apple, [32] PPO is the major enzyme responsible for enzymatic browning of apples. [36] Due to an increase in consumer demand for pre-prepared fruits and vegetables, a solution for enzymatic browning has been a targeted area of research and new product development. [ 37 ]
The crust of brioche bread, which is golden-brown due to the Maillard reaction. The second type of browning, non-enzymatic browning, is a process that also produces the brown pigmentation in foods but without the activity of enzymes. The two main forms of non-enzymatic browning are caramelization and the Maillard reaction.
Caramelization is an entirely different process from Maillard browning, though the results of the two processes are sometimes similar to the naked eye (and taste buds). Caramelization may sometimes cause browning in the same foods in which the Maillard reaction occurs, but the two processes are distinct.
Enzymatic browning affects the nutritional quality and appearance of fruits and produce. Over half of fruit losses are estimated to occur as a result of enzymatic browning, and tropical produce are particularly vulnerable to this reaction. [6]
An oxidative enzyme is an enzyme that catalyses an oxidation reaction. Two most common types of oxidative enzymes are peroxidases, which use hydrogen peroxide, and oxidases, which use molecular oxygen. [1] [2] They increase the rate at which ATP is produced aerobically. Oxidative enzymes are responsible for the browning of fruits like apples.
Browning is the process of partially cooking the surface of meat to develop its flavor through various browning reactions and give it a more attractive color. It is a common first step in cooking braised meats and stews .
When the water is vaporized it leaves the meat through pores in the surface of the meat. Another source of water vapor is the Maillard Reaction. This reaction is responsible for why meat, and many other food products, turn brown when cooked. This reaction only occurs at high temperatures. Water vapor is a byproduct of the Maillard reaction.
The amount of substrate needed to achieve a given rate of reaction is also important. This is given by the Michaelis–Menten constant (K m), which is the substrate concentration required for an enzyme to reach one-half its maximum reaction rate; generally, each enzyme has a characteristic K M for a given substrate.