The quality valuation of wheat is based on characteristics like yield, specific weight, protein content and protein quality. Until now, the starch properties are rarely considered as a quality criterion. In this study, we showed the influence of wheat cultivars (Triticum aestivum L.) and culture year on the intrinsic properties of starch, extracted from European wheat grown in the same conditions. For example, starch damage varied from 13.2 to 19.9 CDU in function of the cultivars and contribution of the B-type starch granules (<10μm) to the total volume ranged from 11.6% to 29.9%. Starch viscosity at 95°C, characterized with α-amylase inactivation by 2mM AgNO3 addition, varied from 276.5 to 351.5BU with the wheat cultivars. It is apparent from this study that starch properties were principally influenced by the wheat cultivar and slightly by the culture year. A good relationship between the pasting properties of whole flour and starch were finally established, showing the important role of starch in the whole flour viscosity. A thorough working knowledge of starch properties could lead to an appropriate selection of wheat cultivar, well-adapted to industrial end uses, without encountering processing or end-products quality problems and with most cost-competitive production.

The effects of genotype, harvest year and their interaction on the levels of arabinoxylans (AX), endoxylanases and endoxylanase inhibitors in wheat were studied using 14 varieties grown in three successive growing periods with diverse climatological conditions. Relations with more commonly evaluated wheat characteristics such as yield, thousand kernel weight, specific weight, protein level, Hagberg falling number (HFN) and α-amylase activity level were examined. Water extractable arabinoxylan (WE-AX) levels in wheat varied much more than total arabinoxylan (TOT-AX) levels. This variability was mainly genetically determined, but harvest year also had an important effect. Total endoxylanase activity levels varied more than a factor of 20 between the different wheat samples. Endogenous endoxylanases typically accounted for only 10–15% of this activity, while wheat-associated microbial endoxylanases accounted for the remaining 85–90%. However, when preharvest sprouting occurred, the contribution of endogenous endoxylanases could sometimes amount to over 40% of this total activity. Endogenous endoxylanase activity levels were mainly determined by the interaction of genotype and harvest year, while wheat-associated microbial endoxylanase activity levels were predominantly determined by genotype alone. Endogenous and microbial endoxylanase activity levels were strongly correlated, suggesting that wheat varieties which are susceptible to preharvest sprouting are often also susceptible to microbial contamination. The TAXI and XIP-type endoxylanase inhibitor levels varied by a factor of 8 and 1.8, respectively. They were mainly determined by genotype and were rather similar in the different growing periods.

Fungicide treatment had a significant impact on endoxylanase activity and XIP levels, but did not affect arabinoxylan (AX) and TAXI levels. The different response of TAXI and XIP type inhibitors to fungicide treatment is interesting. N-fertilisation did not affect AX levels, but significantly increased TAXI and XIP type inhibitor levels. Wheat-associated microbial endoxylanase activity levels were also affected by nitrogen supply, but levels of the endogenous enzyme did not change, except when sprouting occurred. The weather conditions before harvest had no influence on total AX (TOT-AX) and inhibitor levels, but had a large impact on both microbial and endogenous endoxylanase activity and water extractable AX (WE-AX) levels. Under most conditions, endoxylanase activity levels were related to those of α-amylases, liquefaction numbers (LN) and specific weights. WE-AX levels were often weakly but significantly correlated with endoxylanase activity levels, indicating that it is possible that part of the WE-AX in wheat originates from AX degradation by endoxylanases in the field. These results clearly indicate that agronomic circumstances significantly affect the levels of AX, endoxylanases and their inhibitors in wheat, and consequently could affect wheat quality.

C. Massaux1, J. Lenartz2, B. Bodson3, G. Sinnaeve2, A. Falisse3, P. Dardenne2, C. Deroanne1, M. Sindic1 1 Technologie des Industries agro-alimentaires, Faculté universitaire des Sciences agronomiques, 2 Passage des Déportés, B-5030 Gembloux, Belgique, Technoalim@fsagx.ac.be 2 Dpt Qualité des productions agricoles, Centre wallon de recherches agronomiques, 24 Chaussée de Namur, B-5030 Gembloux, Belgique, Dptqual@cra.wallonie.be 3 Phytotechnie des Régions tempérées, Faculté universitaire des Sciences agronomiques, 2 Passage des Déportés, B-5030 Gembloux, Belgique, Phytot@fsagx.ac.be

The influence of wheat variety, harvest year and harvest date on the levels of wheat kernel-associated endogenous and microbial endoxylanases and wheat endogenous endoxylanase inhibitors was investigated using ten winter wheat varieties grown in 2002 and 2003. Three of the varieties were harvested on five different dates in a 1 month period spanning the optimal harvest period. Introductory experiments indicated that endoxylanase activity was very heterogeneously distributed among the different wheat kernels, necessitating the use of relatively large amounts of kernels, i.e. 100 g, to obtain representative wholemeal samples. Apparent endoxylanase activities in these samples largely depended on variety and weather conditions prior to harvesting. In contrast, apparent endoxylanase inhibitor levels were less dependent on climatological circumstances and were mainly determined by genetic factors. The data derived from this study may contribute to explaining the differences observed in functionality between wheats. (c) 2006 Society of Chemical Industry

'Poster présenté aux 56M Journées Techniques des Industries Céréalières Oct. 2005 1 Département Qualité des productions agricoles, Centre Wallon de Recherches agronomiques Chaussée de Namur 24, B-5030 Gembloux, Belgique-Mail: lenartz@cra.wallonie.be e Unité de Technologie des Industries Agroalimentaires, Faculté universitaire des Sciences agronomiques de Gembloux Passage des Déportés 2, B-5030 Gembloux, Belgique l Unité de Phytotechnie des régions tempérées, Faculté universitaire des Sciences agronomiques de Gembloux Passage des Déportés 2, B-5030 Gembloux, Belgique Jonathan LENARTZ1, Carinne MASSAUX, Georges SINNAEVP, Marianne SINDI(2, Bernard BODSON3, André FALISSP, Claude DEROANNP, Pierre DARDENNP