Enzymes — biological catalysts that drive specific chemical reactions — are both the chef's tools and the chef's adversaries. Controlling enzyme activity (through temperature, pH, salt concentration, or inhibitors) allows specific, directed transformations. Uncontrolled enzyme activity produces browning, bitterness, over-tenderisation, or flavour loss.
**Proteases (protein-cutting enzymes):** - Papain (papaya), bromelain (pineapple), actinidin (kiwi), ficin (fig) — all cut protein chains. Used for meat tenderisation. - Denatured by heat above 65°C — cooking inactivates proteases. - Caution: fresh pineapple in gelatin prevents setting (bromelain cuts the gelatin proteins) — use canned pineapple (heat-treated, bromelain deactivated) or heat the pineapple before use. **Amylases (starch-cutting enzymes):** - Present in wheat flour (diastatic malt adds amylase activity) — cut long starch chains into fermentable sugars. - The source of the sugars that fuel yeast fermentation in bread. **Polyphenol oxidase (browning enzymes):** - Activated on exposure to air (oxygen) after cell rupture — the cause of avocado, apple, and mushroom browning. - Inhibited by: acid (lime juice, lemon), salt, cold temperature, exclusion of oxygen (vacuum). **Lipoxygenase:** - Active in fresh flour — responsible for the "raw flour" flavour and also implicated in some off-flavours in minimally processed foods. Deactivated by heat.
Modernist Cuisine