Baking lipoxygenase

Long ago it was noticed that the baking quality of white flour improved with storage for 1-2 months. This effect occurred more rapidly if the flour was exposed to the air. During storage, initially the level of free fatty acids increases, presumably owing to lipolytic activity. Lipoxygenase activity then produces oxidised fatty acids as the proportion of linoleic and linolenic acids falls while the number of -S-S- bonds decreases. 

The importslnce of lipoxygenase increases when soybean flour is added to wheat flour to improve baking quality or when soybean flour is admixed in larger quantities to improve the protein nutritional quality. 

Wheat lipoxygenase and soybean lipoxygenase, catalyzing oxidation of fatty acids, generate oxidized reaction products that improve the dough-forming properties and baking performance of flour. A similar role is performed by polyphenol oxidase and peroxidase. 

Cooking fish decreases the rate of rancid development on storage. This effect is attributed to the destruction of lipoxygenase, formation of water-soluble antioxidants, and destruction of heme compounds. Baked fish developed lower free fatty acids and carbonyl values but higher TBA values than raw fish after storage at -18°C for 8 weeks (Table 11.24). The TBA and carbonyl values reached a maximum and then decreased after 6 weeks storage, apparently because of further decomposition of carbonyl compounds. However, these determinations did not necessarily reflect the degrees of flavor deterioration, which needed to be determined by sensory analyses. 

Starch processing and baking Alpha-amylase Amyloglucosidase Glucose isomerase Pullulanase Beta-amylase Proteases Lipoxygenases Phospholipase Pentosanase Dairy industry Rennet Proteases Chymosin Pepsin... 

The involvement of endogenous lipoxygenase in the baking of wheat flour is not clear. However, by addition of lipoxygenase-active soy flour, a significant improvement of the flour quality is achieved (cf. 15.4.1.4.3). 

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