Properties of alkaline wet milled corn starch: Effect of steeping temperature, steeping time and sodium hydroxide concentration

摘要

Steeping temperature, time and the concentration of NaOH (w/v) influenced a number of the properties of wet-milled corn starch. Overall, alkaline wet milling produced pure corn starch with 97 $pm$ 2.5% starch and less than 0.25% protein on a 14% MB. Nevertheless, processing conditions may have altered the amorphous region of the granule in ways hypothesized to influence starch crystallinity and thermal properties. Gelatinization temperatures were significantly higher than those for unmodified commercial corn starch, while enthalpy values were significantly lower. As steeping temperature, time, and NaOH concentration increased, distilled water binding capacity (DWBC) increased while Rapid Visco Analyzer (RVA) peak consistency decreased. The relative gel strength of the starch gels was affected by NaOH concentration, steeping temperature and steeping time, but trends were not clear. Freeze-thaw stability and the dynamic rheological properties of starch gels were not affected by the steeping conditions employed in this study.;Alkaline wet milling with a dynamic steeping temperature of 35-45$spcirc$C, steeping time ranging from 1 to 3 hours and sodium hydroxide concentration ranging from 0.30 to 0.70% (w/v) produced the highest starch yields (71.4%). Evaluation of the chemical and physical properties of corn starch revealed that starch isolated under these dynamic steeping conditions (for maximum starch yield) had high RVA peak consistency and DWBC was $sim$75% (14% MB). Starch gelatinization temperatures were significantly higher than those for commercial corn starch, but gelatinization enthalpies were lower. Dynamic steeping conditions used in this study did not affect freeze thaw stability nor the storage modulus (G$spprime)$ of starch gels (7.5%) stored at 4 $pm$ 2$spcirc$C for 14 days.;Processing by the SO$sb2$ procedure versus the standard alkaline wet milling process did not influence the starch yields from ten corn hybrids. Nevertheless, the physical properties of these starches were dependent on hybrid and the conditions used for starch isolation (SO$sb2$ versus NaOH).