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Starch properties, endogenous amylase activity, and ethanol production of corn kernels with different planting dates and drying conditions.

机译：不同种植日期和干燥条件下玉米籽粒的淀粉特性，内源淀粉酶活性和乙醇产量。

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摘要

This study was conducted with aim to understand how planting dates and drying conditions affected starch properties and dry-grind ethanol production of corn kernels. Three corn varieties with planting dates between 4 April and 11 June during 2007-2009 growing seasons as the treatments were used in this study. The maximum grain yield and kernel starch content were obtained with corn planted between late April and mid-May; both decreased when planting was delayed to late May and June. Later planting dates resulted in larger proportions of short amylopectin branch-chains for one of the studied varieties, less amylose contents of starch, lower starch gelatinization and pasting temperatures, and greater peak viscosity of starch paste for both corn varieties. While these changes may impact the quality and yield of starch, they might not be of sufficient magnitude to impose major problems in processing of products containing starch.;Starches isolated from corn kernels planted on a late date (11 June) were hydrolyzed at comparable rates as those planted on early dates (late April and mid-May) using a raw starch hydrolyzing enzyme. Consequently, kernels planted in late May and in June gave similar ethanol yields (on kernel dry weight basis) as those planted on earlier dates. The results showed that the planting date of corn did not affect the ethanol yield on the basis of kernel weight. The grain yield, however, decreased with late planting dates, and thus, reduced the ethanol yield on the basis of unit planting area (g ethanol/hectare of planted area).;Freshly harvested kernels of three commercial corn hybrids were dried at low (10ºC), ambient (25ºC), intermediate (45 and 65ºC), and high (85ºC) air temperatures to 14% moisture content to assess how kernel drying temperatures impacted functional properties of starch and ethanol yield of the kernels. The air drying temperature at 10°C increased starch gelatinization temperature and enthalpy change and reduced the swelling power of starch compared with the control (25°C). This can be attributed to that the drying temperature at 10°C was close to the optimum temperature of starch crystallization (4°C) and, thus, enhanced starch crystallinity. The intermediate air drying temperatures (45°C and 65°C) increased starch gelatinization temperature and enthalpy change and narrowed the gelatinization temperature range of starch compared with the control. These results suggested that starch molecules annealed during the drying at 45°C and 65°C and perfected the crystalline structure of starch. The drying temperature of 85°C partially gelatinized the starch granules during the drying and reduced their crystallinity. Consequently, starch isolated from kernels dried at 85°C exhibited higher gelatinization temperature and reduced swelling power of starch compared with the control.;Changes in the starch structure reduced the granule susceptibility to the enzyme hydrolysis and, thus, decreased the ethanol yield of ground kernels dried at the intermediate (45°C and 65°C) and high (85°C) air temperatures. Kernels dried at 85°C produced the least yield of ethanol, which might be resulted from the most severe reduction in the starch swelling power that inhibited enzyme penetration into the starch granule in addition to the loss of the endogenous enzyme activity of kernels during drying at 85°C.;Kernels dried at temperatures up to 65°C air temperatures displayed similar levels of endogenous amylase activity, whereas those dried at ≥85°C contained partially reduced amylase activity as indicated by the reduced amount of reducing sugars produced in the ground kernel suspensions incubated at 40°C for 20h. Among the endogenous amylases, beta-amylase was most heat-labile and showed reduced activity after the kernel was dried at 45°C. Pullulanase and isoamylase showed reduced enzyme activity in kernels after the drying at 85°C. The alpha-amylase was relatively stable up to 85°C but significantly lost its activity after drying at 105 and 125°C air temperatures.
机译：进行这项研究的目的是了解种植日期和干燥条件如何影响玉米粒的淀粉特性和干磨乙醇的生产。在本研究中使用了三种玉米品种，在2007-2009年生长季节期间的播种日期为4月4日至6月11日。 4月下旬至5月中旬播种的玉米获得了最大的谷物产量和籽粒淀粉含量。当播种推迟到5月底和6月时，两者均下降。较晚的播种日期导致两个研究品种之一的较大支链淀粉的短支链淀粉比例更高，淀粉的直链淀粉含量较少，淀粉糊化和糊化温度较低，淀粉糊的峰值粘度较高。尽管这些变化可能会影响淀粉的质量和产量，但它们的幅度可能不足以对含淀粉产品的加工造成重大问题。从后期种植的玉米粒中分离出的淀粉（6月11日）以相当的速率水解如在早期（4月下旬和5月中旬）使用原始淀粉水解酶种植的那些。因此，5月下旬和6月播种的籽粒乙醇产量（以籽粒干重计）与早期播种的乙醇产量相似。结果表明，基于粒重，玉米的播种期不影响乙醇产量。然而，谷物产量随着播种期的推迟而降低，因此，以单位播种面积（g乙醇/公顷种植面积）为基础，降低了乙醇的产量。；将三个商业玉米杂交种的新收获籽粒在较低的温度下干燥（ 10ºC），环境温度（25ºC），中间温度（45和65ºC）和高温（85ºC）到14％的水分含量，以评估谷粒干燥温度如何影响淀粉的功能特性和谷粒的乙醇产量。与对照（25℃）相比，在10℃下的空气干燥温度提高了淀粉糊化温度和焓变并降低了淀粉的溶胀能力。这可以归因于在10℃下的干燥温度接近淀粉结晶的最佳温度（4℃），并因此增强了淀粉的结晶度。与对照相比，中间空气干燥温度（45°C和65°C）增加了淀粉糊化温度和焓变，并缩小了淀粉糊化温度范围。这些结果表明淀粉分子在45℃和65℃下的干燥过程中退火并完善了淀粉的晶体结构。 85℃的干燥温度在干燥过程中使淀粉颗粒部分胶凝并降低了其结晶度。因此，与对照相比，从籽粒中分离出的淀粉在85°C干燥时表现出更高的糊化温度和降低的淀粉溶胀能力。淀粉结构的变化降低了颗粒对酶水解的敏感性，因此降低了地面乙醇的产量玉米粒在中间温度（45°C和65°C）和高温（85°C）下干燥。在85°C下干燥的籽粒产生的乙醇产量最少，这可能是由于淀粉溶胀力的最严重降低所致，这种淀粉溶胀能抑制酶在淀粉颗粒中的渗透，此外，在80℃下干燥期间仁的内源酶活性降低。 85°C;在高达65°C的空气温度下干燥的籽粒显示出相似水平的内源淀粉酶活性，而在≥85°C的温度下干燥的那些籽粒则具有部分降低的淀粉酶活性，这表明在地面上产生的还原糖减少核悬浮液在40°C下孵育20h。在内源性淀粉酶中，β-淀粉酶最不耐热，在将果仁在45°C下干燥后，其活性降低。在85°C干燥后，支链淀粉酶和异淀粉酶在籽粒中显示出降低的酶活性。该α-淀粉酶在高达85°C的温度下相对稳定，但在105和125°C的空气温度下干燥后，其活性明显下降。

著录项

  • 作者

    Medic, Jelena.;

  • 作者单位

    Iowa State University.;

  • 授予单位 Iowa State University.;
  • 学科 Agriculture Food Science and Technology.
  • 学位 Ph.D.
  • 年度 2011
  • 页码 175 p.
  • 总页数 175
  • 原文格式 PDF
  • 正文语种 eng
  • 中图分类
  • 关键词

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