**5.1 Importance of lipoxygenase inhibition for food industry**

Besides their physiological role, plant lipoxygenases are of significant importance to the food industry, since these enzymes have been implicated in the generation of the flavour and aroma in many plant products. For instance, they are responsible for the undesirable 'beany', 'green' and 'grassy' flavours produced during processing and storage of protein products derived from legume seeds (Fukushima, 1994; Robinson et al., 1995) and the development of the stale flavour in beer during storage (Kobayashi et al., 1993). Lipoxygenases also play an important role in the baking industry. They are quite effective as bleaching agents, increase mixing tolerance and improve dough rheology (Nicolas & Potus, 1994; Larreta-Garde, 1995; Cumbee et al., 1997; Borellib et al., 1999).

Freshly refined soybean oil is practically odourless and bland, but "green, grassy, fishy" offflavors may develop quickly if the oil is heated or stored under conditions that expose it to light and oxygen or by contamination with pro-oxidant metals such as copper and iron (Berk, 1992). "Beany" flavour is the principal inconvenience of traditional soymilk and its products (e.g., tofu) and is caused by some ketones and aldehydes, particularly hexanals and heptanals, produced through LOX catalyzed oxidation (Berk, 1992).

Fish lipids are susceptible to oxidation owing to the high levels of polyunsaturated fatty acids (PUFA), even in frozen storage, and this can affect the flavour, texture, taste, aroma and shelf life of fish (Ke & Ackman, 1976). Since the direct interaction between oxygen and highly unsaturated lipids is kinetically hindered (Kanner et al., 1987), the enzymatic initiation of oxidation by enzymes such as lipoxygenase, peroxidases and microsomal enzymes has been gaining favour.

Green tea glazing was shown to improve the storage quality of frozen bonito fillets (Lin & Lin, 2005). In addition, hot water tea extract was shown to suppress the pro-oxidant activities of the dark meat and skin of blue sprat (Seto et al., 2005). Banerjee (2006) proposes that the improvement in the shelf life of fish by green tea polyphenols is at least in part due to inhibition of LOX resulting in delaying oxidation of fish lipids and because of that impregnation of muscle fillets in tea extract by itself or in combination with other natural inhibitors may improve the shelf-life and storage quality of fish fillets.

Besides its function of oxidizing the polyunsaturated fatty acids (linoleic, linolenic and arachidonic), the enzyme may also catalyse the co-oxidation of carotenoids, resulting in the loss of natural colorants and essential nutrients (Robinson et al., 1995). LOX have been implicated in the generation of the flavour and aroma in many plant products, in the decolourisation of pigments and in the potential of compromising the anti-oxidant status (Casey, 1999). In pasta the involvement of LOX in colour loss is demonstrated by positive correlation between the decrease of β-carotene content after pastification and LOX activities in semolina. In addition to this, the hydroperoxidation and bleaching activities of LOX are highly correlated demonstrating that the bleaching might be ascribable to a co-oxidative action by LOX (Borrellia et al., 1999).

During pasta processing in which the maximal pigment degradation by LOX activity occurs (Borrellib et al., 1999), it is shown that externally added β-carotene can act as inhibitor of the LOX-catalysed linoleate hydroperoxidation and an inverse relation between the % of carotenoid loss and the initial carotenoid content in semolina from durum varieties, showing similar LOX activity, was found (Trono et al., 1999).

The complete characterisation of lipoxygenase from pea seeds (*Pisum sativum var. Telephone L.*) gives possibility to avoid destructive influence during food processing and storage (Szymanowska et al., 2009) by the action of this enzyme.
