Effect of a Cell‐Wall‐Degrading Enzyme Complex on Starch Recovery and Steeping Requirements of Sorghum and Maize

Abstract

The effect of a commercial cell‐wall‐degrading enzyme (CWDE) complex on the steeping time and starch yields of white regular sorghum (RSOR) compared with yellow maize (YMZ) was determined. An in vitro wet‐milling method standardized to test dosages of 0–120 fungal β‐glucanase units (FBG)/100 mL indicated that starch yields were significantly higher for YMZ than RSOR and increased proportionally as enzyme dosage increased. A factorial experiment with a level of confidence of P < 0.05 was performed to study the effect of CWDE addition to coarsely ground grains for 4 hr after 20 or 44 hr of SO2 steeping of whole grains. At both regular steep times, YMZ yielded significantly higher amounts of starch than RSOR. When steep times were compared, grains soaked for 48 hr produced 1.7% higher starch yields than counterparts treated for 24 hr. CWDE significantly increased starch yields and recoveries. Enzyme‐treated grains yielded 2.5% more starch than counterparts steeped regularly. For both grains, the best wet‐milling conditions to obtain the highest amount of starch were 48 hr of steeping and CWDE addition. Under these conditions, YMZ and RSOR yielded 66.9 and 66.6% starch, respectively. Starches obtained after the enzyme treatment at both steep times contained higher amounts of residual protein and ash compared with the untreated counterparts. Rapid viscoamylograph properties of YMZ and RSOR starches were not affected by the use of the CWDE nor the steep time. In comparison with RSOR starch, the YMZ starch initiated gelatinization at lower temperature, had less shear thinning and higher viscosity or setback at the end of cooling.

Enzymatic Milling Product Yield Comparison with Reduced Levels of Bromelain and Varying Levels of Sulfur Dioxide

“…This was also the first report to demonstrate that the use of a protease alone, without other enzymes or sulfur dioxide addition, was sufficient to reach starch yields equivalent to or exceeding that of the conventional sulfite wet-milling process (Johnston and Singh 2001;Johnston et al 2003). Other enzymesteeping processes have been developed that nominally decreased the required steeping time or to some extent improved starch recoveries (Hassanean and Abdel-Wahed 1986;Caransa et al 1988;Moheno-Perez et al 1999;Serna-Saldivar et al 2003). However, in these studies, enzymes were used in combination with high levels of SO 2 and no specific class of enzyme or enzymes responsible for improvements were identified.…”

Cell Wall Degrading Enzymes and Proteases Improve Starch Yields of Sorghum and Maize

“…In a previous experiment, Moheno-Perez et al [1] found that addition of a fiber-degrading enzyme complex to whole kernels did not improve starch yield, with the exception of regular sorghum. Recent studies [5][6][7][8] demonstrated that the use of proteases or cell-walldegrading enzymes added to coarsely ground maize or sorghum kernels significantly reduced steep times and improved prime starch yields [6,8]. Previous research [6] concluded that grains soaked for 20 h, coarsely ground and treated with Vizcozyme L ® for 4 h yielded starch similar to counterpart regularly steeped for 48 h without Vizcozyme L ® .…”

Effect of Sorghum Decortication and Use of Protease Before Liquefaction with Thermoresistant α‐Amylase on Efficiency of Bioethanol Production

“…Abrasive decortication operates on the principle of progressively rubbing off the kernel outer layers (Beta et al 2000). Recent wet-milling studies (Serna-Saldivar and Mezo-Villanueva 2003;Mezo-Villanueva and Serna-Saldivar 2004;Perez-Carrillo and Serna-Saldivar 2006) demonstrated that the use of protease or cell-wall-degrading enzymes added to coarsely ground maize or sorghum significantly reduced SO 2 steep times and improved prime starch yields. Higiro et al (2003) compared the quality and yield of starch extracted from roller-milled sorghum grits obtained after decortication and degermination.…”

“…The main advantages of this technology are higher ethanol yields and higher value of the coproducts . Recent wet-milling studies (Serna-Saldivar and Mezo-Villanueva 2003;Mezo-Villanueva and Serna-Saldivar 2004;Perez-Carrillo and Serna-Saldivar 2006) demonstrated that the use of protease or cell-wall-degrading enzymes added to coarsely ground maize or sorghum significantly reduced SO 2 steep times and improved prime starch yields. In a preceding work (Perez-Carrillo and Serna-Saldivar 2007), we observed an improvement in reducing sugars concentration when sorghum was mechanically decorticated and treated with a protease before starch liquefaction.…”