The current study was undertaken to provide solutions to optimize the unsaponifiable antioxidants content of bread. We report a complete description of changes in wheat carotenoids and vitamin E content from grain to bread and highlight the most important processing steps affecting their level in wheat bread. Major carotenoids losses occurred during kneading. A close correlation (r(2) = 0.97; P = 0.05) was found between carotenoid pigment losses and lipoxygenase (LOX) activity, both parameters depending on wheat genotype. The use of wheat species exhibiting high carotenoid contents and low LOX activity was shown to preserve significant carotenoid level in the bread. No relation was found between vitamin E losses during doughmaking and LOX activity. In addition, moderate kneading resulted in higher vitamin E retention in comparison with carotenoids (12% and 66% losses, respectively). It is concluded that carotenoids are more susceptible to oxidation by endogenous lipoxygenase than vitamin E during breadmaking. This study showed that bread nutritional quality, in terms of antioxidant content, could be improved by selecting suitable cereal genotypes, if this potential is preserved by milling and baking processes.

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Cereal Chem. 75(1):85-93The effect of mixing has been tested on the extractable activities of lipoxygenase, peroxidase, and catalase from dough after 2, 5, and 20 min of mixing, and 30 min of rest period after 20 min of mixing. Different mixing conditions have been studied including temperature, atmosphere, speed, amount of water added to the dough, buffer solutions between pH 3.6 and 7.5 added to the dough, and different additives (linoleic acid, guaiacol, hydrogen peroxide, ascorbic acid, cysteine, yeast, and sodium chloride). In all the mixing conditions tested, the dough peroxidase activity remains equivalent to the initial flour activity, whereas losses in lipoxygenase and catalase activities largely varied according to mixing conditions. The results show that a self-destruction mechanism as well as physicochemical denaturation are responsible for these losses. Lipoxygenase losses seem mainly associated with the former mechanism, whereas catalase losses are highly increased in acidic conditions (physicochemical denaturation). Therefore, the relative impact of the three oxidoreducing enzymes may be largely modulated by mixing conditions.

Cereal Chem. 76(2):213-218 The behavior of different exogenous enzymes (soybean lipoxygenase [SLOX], horseradish peroxidase [HPOD], catalase from bovine liver [BCAT], and glucose oxidase [GOX] from Aspergillus niger) added to dough was studied during mixing. The effect of adding these exogenous oxidoreductases on the activity of three oxidative enzymes present in wheat flour (lipoxygenase [WLOX], peroxidase [WPOD], and catalase [WCAT]) was examined.Proper assay conditions were established to differentiate between added WLOX, WPOD, and WCAT and the corresponding activities present in wheat flour. For doughs with added SLOX, an immediate loss of extractable SLOX (≈40%) was observed which remained constant during further mixing. When compared with the control dough, addition of SLOX decreased the losses in WLOX and WCAT activities, whereas WPOD activity was unaffected. With doughs supplemented by HPOD, an immediate loss of 20% in the HPOD activity was observed which did not change after 20 min of mixing. Compared with control dough, addition of HPOD did not affect the behavior

Flours differing in water content of 10% (F10), 12% (F12), and 14% (F14) were stored for 16 weeks at 22, 32, and 45°C. The major changes in lipids concerned the free fatty acids (increase) and the triglycerides (decrease). In all cases, the changes increased with increasing storage temperature and water content. After 16 weeks of storage, the losses in lipoxygenase (LOX) activity increased with increasing flour moisture and storage temperature from 10% for F10 at 22°C to 100% for F14 at 45°C. At the end of storage at 22 and 32°C, the bread volumes decreased by 10 and 25%, respectively, with no statistical differences (P < 0.05) between the samples. At 45°C, the volume losses were equal to 35, 46, and 61% for the F10, F12, and F14 samples, respectively. In the same time, the flour oxidative ability (oxygen uptake during dough mixing) increased for the F10 and F12 samples with increasing storage temperature, whereas it decreased for the F14 samples stored at 45°C. Therefore, provided the residual LOX activity is sufficient (omission of the F14 samples stored at 45°C), the flour oxidative ability increased during storage and is positively correlated to its oxidable PUFA content.