Impact of Preharvest Sprouting of Wheat (Triticum aestivum) in the Field on Starch, Protein, and Arabinoxylan Properties

Abstract

To obtain detailed knowledge on possible changes in the properties of starch, proteins, and arabinoxylan as a result of field preharvest sprouting (PHS), three wheat varieties were harvested at maturity and several weeks later when severe PHS had occurred. Falling number values of flour dropped from 306 to 147 s (Sahara), 382 to 155 s (Forum), and 371 to 230 s (Tobak). Blocking of α-amylase activity demonstrated that the decline in falling number and changes in RVA pasting and gelation properties were not caused by changes in intrinsic starch properties as a result of PHS. PHS had no influence on the SDS-extractability and molecular weight distribution of the proteins. For arabinoxylan, incipient breakdown was noticed, leading to a higher amount and average degree of polymerization of water extractable arabinoxylan. Results show that strategies to cope with severely PHS in wheat should focus on blocking enzyme activities.

Role of α‐Amylase in the Pasting Behavior of Wheat Flours Upon Storage

“…Silver nitrate strongly inhibits the α-amylase activity during the RVA test, no effect on other flour components are known today, but cannot be excluded definitely. [10] As expected, for freshly milled flour higher viscosities were found after AgNO 3 addition compared to the results with water as a solvent. Variations within the different flours were lower, as PV varied from 2414 to 2533 cP, TV from 1550 to 1610 cP, and FV from 2604 to 2756 cP.…”

“…With the addition of silver nitrate solution (Table ), a similar behaviour was identified, but changes were less pronounced and some remarkable differences were found. Silver nitrate strongly inhibits the α‐amylase activity during the RVA test, no effect on other flour components are known today, but cannot be excluded definitely . As expected, for freshly milled flour higher viscosities were found after AgNO 3 addition compared to the results with water as a solvent.…”

“…Better knowledge about the contribution of single flour components to these viscosity changes would be beneficial to use suitable flours and/or additives for bakery products with precise raw material requirements. At least the influence of one flour constituent, α‐amylase, can be isolated, by inhibition with 2 mM silver nitrate . Determination of both curves, with and without α‐amylase inhibition, and calculation of their differences offers the option to observe the impact of α‐amylase on pasting viscosities .…”

“…At least the influence of one flour constituent, α-amylase, can be isolated, by inhibition with 2 mM silver nitrate. [10] Determination of both curves, with and without α-amylase inhibition, and calculation of their differences offers the option to observe the impact of α-amylase on pasting viscosities. [11] Too high, but also too low α-amylase activities in wheat flour are resulting in insufficient baking quality.…”

Impact of Wheat (Triticum aestivum L.) Germination Process on Starch Properties for Application in Films

“…Amylases produced during germination break glycosidic linkages of starch to produce single sugars (maltose, glucose, and dextrin) . Moreover, according to Olaerts et al, wheat germination affects starch pasting properties; it reduces the binding capacity and swelling power of starch in water. Simsek et al also reported that wheat germination induces significant changes in the physiochemical properties of starch due to α‐amylase activities, which contributes to degradation of starch molecules.…”