Quality of Gluten-Free Bread Formulations Baked in Different Ovens

The objective of this study was to determine the effects of different tigernut flour/rice flour ratios (0:100, 5:95, 10:90, 15:85, 20:80, and 25:75) on quality of gluten-free bread formulations baked in infrared–microwave combination and conventional ovens. The degrees of the starch gelatinization of breads baked in different ovens were also compared. Conventionally baked breads prepared with tigernut flour/rice flour ratio of 10:90 and the infrared–microwave combination-baked breads prepared with tigernut/rice flour ratio of 20:80 had the most acceptable firmness and specific volume values. These breads had also similar color. Tigernut flour had significantly higher gelatinization temperatures and lower gelatinization enthalpy (ΔH_g) values than rice flour (p?≤?0.05). As rice flour was replaced with tigernut flour, lower ΔH_g values were observed in dough samples. Breads baked in both conventional and combination oven had sufficient starch gelatinization degrees ranging from 91% to 94% and from 84% to 85%, respectively.     

聚焦光束反射分析仪测定淀粉糊化过程中糊化度的变化

利用聚焦光束反射分析仪(FBRM)分析了玉米淀粉、马铃薯淀粉和木薯淀粉在糊化过程中颗粒总数的变化,实现了淀粉颗粒变化的"动态"监测,并提出用颗粒总数的变化量/颗粒的初始总数来表示糊化度,简化了以往测量糊化度的方法。结果表明:FBRM测得的玉米淀粉颗粒总数呈先增加后减小的趋势,在70℃时下降幅度最大;马铃薯淀粉颗粒总数一直减小,在70℃时下降幅度最大;木薯淀粉颗粒总数也一直减小,但在65℃时下降幅度最大。FBRM测得玉米淀粉在70℃糊化度达到最大值60.05%,马铃薯淀粉在70℃糊化度达到最大值38.83%,木薯淀粉在65℃糊化度达到最大值54.66%;当温度达到75℃时,玉米淀粉,马铃薯淀粉和木薯淀粉总的糊化度分别为93.55%、90.19%和85.85%,它们都没有达到100%。     

稻米淀粉期化进程研究

对不同初始粒径的稻米淀粉的糊化进程进行了研究。结果表明,淀粉的糊化具有上升,平缓和回落三个除段,在糊化温度以下（60℃）,淀粉颗粒仅存在吸水膨胀,糊化度曲线平坦,糊化温度以上,随加热温度和的升高,淀粉的糊化速度和糊化程度迅速增高,明显开成糊化过程的三阶段,较小的初始粒径会加快糊化进程,增大回落程度,但对糊化程度影响不大,加热温度对糊化特性的影响较淀粉的初始粒径大。     

不同糊化度的籼米淀粉在贮藏过程中结晶性和抗性淀粉的变化

本文以籼米淀粉为原料,经完全和部分糊化后,在25℃、4℃和-18℃贮藏过程中分别测定其结晶性和抗性淀粉的变化,结果表明：完全糊化淀粉在25℃、4℃和-18℃贮藏过程中,结晶度从0%分别增至7.98%,12.53%和11.77%,相应的抗性淀粉含量分别为4.1%,8.6%,6.5%,与0d相比,增加了2.7%,7.2%,5.1%;部分糊化淀粉的结晶度从11.14%分别增至19.11%,24.45%和22.89%,相应的抗性淀粉含量分别为13.8%,17.8%,15.8%,与0d相比,增加了5.7%,9.7%,7.1%。部分和完全糊化的淀粉相比,在相同的贮藏温度下,部分糊化淀粉结晶速率较快,抗性淀粉和慢消化淀粉的含量较多;与-18℃和25℃贮藏温度相比,4℃结晶速率较快,更易形成抗性淀粉。     

抗性淀粉糊化特性的研究

采用差示扫描量热分析技术(DSC)对不同原淀粉及各抗性淀粉样品的糊化温度及热焓值进行了测试.DSC扫描曲线表明:抗性淀粉的DSC吸热曲线完全不同于原淀粉的吸热曲线,原淀粉只在70℃左右有一个较小的吸热峰,而抗性淀粉在150℃左右有一个较大的吸热峰,热焓值在30J/g左右;由不同来源淀粉制成的抗性淀粉样品之间其糊化特性没有显著差别.     

小麦总淀粉、A-淀粉及B-淀粉的热损伤与其糊化度、糊化特性的关系

为了探索热处理温度和水分对淀粉损伤及损伤后淀粉糊特性的影响,揭示小麦淀粉的热损伤程度与糊化度、糊黏度特性之间的关系,以市售面粉分离的总淀粉、A-淀粉和B-淀粉为原料,经30～90 ℃的温度处理后,测定其在高、低水分下的破损淀粉含量、糊化度及糊化特性的变化。结果表明：低水分下,淀粉损伤、糊化度和淀粉糊性质随热处理温度变化不明显;高水分含量下,随着热处理温度的升高,破损淀粉含量和糊化度呈明显上升趋势,热损伤程度与糊化度之间呈显著正相关（P＜0.05）,糊化温度略有增加,主要的黏度参数显著下降,损伤淀粉与峰值黏度之间呈显著负相关（P＜0.05）。     

淀粉糊化度测量方法研究进展

淀粉糊化度(Degree of Starch Gelatinization,DSG)不仅影响含淀粉类食品的物理和感官特性,而且还影响其消化特性和营养特性,如何准确、快速、简便地检测DSG已经成为食品工业界亟待解决的热点问题。本文在国内外相关研究的基础之上,综述了DSG测量方法的原理及准确性,并将几种常用方法的准确性进行了比较。经过系统比较分析,发现利用酶法测定DSG是当前较为合适的测定方法,但其还存在测定程序繁琐、耗时等问题。因此,还需要进一步优化和改进酶法,使其能够成为DSG快速、准确、广谱的测定方法。     

A Note on the Gelatinization of Starch

A number of explanations for the melting behavior of starch in excess and limited water have been offered, none of which appears to be totally satisfactory. Most explanations do not account for the fact that gelatinization starts at the hilum and proceeds to the exterior of the granule. In limited water, starch gives two melting peaks with the differential scanning calorimeter. This has been explained on the basis of the granule limiting water to the crystallites. However, it was found that amylopectin crystallized from soluble material also gave a two-peak melting pattern in low water very similar to that found with total starch. Thus, the granule structure is not responsible for the two-peak melting of starch.     

稻米淀粉的糊化动力学研究

采用一级反应模型对不同类型稻米淀粉的糊化特性和糊化动力学进行了研究，结果表明：不同类型稻米淀粉的糊化特性有较大差异。淀粉的糊化能耗主要用于淀粉晶体的熔解，颗粒的膨胀和直链淀粉分子从淀粉颗粒中的脱离。其中以晶体崩解速度最大，所需能耗最小；其次为颗粒膨胀能，直链淀粉溶出的速度最小，所需能耗最大。不同来源淀粉的膨胀速度和直链淀粉溶解速度，糊化能及其分配也有所差异，以籼稻的润胀能较小，其次依次为粳稻和糯稻；籼稻直链淀粉脱离淀粉颗粒（淀粉糊上清液BV值）所需能耗最大，其次为粳稻。3种稻米淀粉的酶解能耗差异不大，以糯稻淀粉较难以水解。     

Effect of Degree of Starch Gelatinization on Quality Attributes of Fried Tortilla Chips

ABSTRACT: The effect of degree of starch gelatinization on the quality attributes of tortilla chips was studied. Three different samples were prepared: control (45% of starch gelatinized before frying), freeze-dried (5% of starch gelatinized before frying), and steamed-baked tortilla chips (87% starch gelatinized before frying). Compared to the control chips, the steamed-baked tortillas produced chips with lower oil content. They shrunk the most and showed a high degree of puffiness and lower crunchiness. Their texture was harder and not very crunchy. The majority of the oil in these chips was located at the surface. The freeze-dried tortilla yielded chips with high oil content. The texture was soft, and the porosity was very low, providing unacceptable characteristics in tortilla chips.     

Starch Gelatinization in the Presence of Emulsifiers. A Morphological Study of Wheat Starch

Wheat starch was heated in the presence of emulsifiers (sodium dodecyl sulphate, SDS, sodium stearoyl-lactylate, SSL, and glycerol-monostearate, GMS) and samples were viewed in the scanning electron microscope after heating at different temperatures. It was found that the typical morphological changes occurring when the large wheat starch granules are heated occurred at lower temperatures in the presence of SDS, and at higher temperatures in the presence of GMS or SSL compared to the control without any added emulsifier. Gel volumes changed in the same way, and the amount of amylose leached from the granules decreased in the presence of emulsifiers.     

淀粉纳米颗粒在不同增塑剂中的糊化与流变特性研究

本文以蜡质玉米淀粉为原料,经普鲁兰酶酶解脱支,短直链淀粉重结晶制取淀粉纳米颗粒(SNPs)。采用差示扫描量热仪(DSC)和动态流变仪,探究了不同浓度SNPs在甘油、山梨糖醇、葡萄糖水溶液中的热特性、回生特性以及流变特性的变化规律。DSC测试表明,添加山梨糖醇、葡萄糖和甘油溶液(其与水比例为1:1)后,SNPs的起始糊化温度分别增加了10.85℃、10.96℃和15.02℃,SNPs的终止糊化温度分别增加了9.29℃、9.17℃、12.40℃。回生结果表明,增塑剂会抑制SNPs的回生。随着浓度增加,SNPs在增塑剂体系中储能模量明显增加,且损耗模量大于储能模量,凝胶性增强。20%SNPs在山梨糖醇溶液和甘油溶液中的储能模量是10 Pa·s左右,而在葡萄糖溶液中大于1000 Pa·s,在葡萄糖溶液中损耗模量在100~500 Pa·s,说明SNPs葡萄糖水溶液具有更强的凝胶性。本文为SNPs在不同增塑剂中制备可降解膜提供理论依据。     

A Pulsed NMR Study of Some Aspects of Starch Gelatinization

Spin-spin relaxation times of protons in starch suspensions are reported. Values were found to change markedly upon gelatinization. This behaviour is attributed to an increase in the mobility and hydration of polymer chains. It is suggested that the change in relaxation time reflects the properties of a small number of protons in the system and that the bulk of the water is not bound in any fundamental sense.     

高直链玉米淀粉的糊化特性研究

目的研究水浴加热、微波加热和高压加热方法对高直链玉米淀粉糊化性能的影响,为高直链淀粉的进一步开发和应用提供理论基础。方法以高直链玉米淀粉为原料,在过量水分存在条件下,分别采用水浴加热、微波加热和高压加热制备高直链玉米淀粉糊,分别研究不同温度和微波功率下,高直链玉米淀粉糊碘兰值和酶解力随糊化时间增加的变化规律。结果水浴加热、微波加热和高压加热糊化过程中高直链玉米淀粉的碘兰值和酶解力均随时间的延长呈上升趋势,微波加热高直链玉米淀粉糊的碘兰值和酶解力低于高压加热但高于水浴加热,微波加热淀粉的糊化速度大于水浴加热和高压加热。结论高压加热淀粉糊化效果好,淀粉的糊化程度高,是使高直链淀粉完全糊化的较好方法。     

Evaluation of the Degree of Starch Gelatinization by a New Enzymatic Method

In this work, a new enzymatic method is proposed to evaluate the degree of starch gelatinization in starchy food and feed. The procedure developed is based on the fact that the gelatinization process enhances the chemical reactivity of inert starch granules towards amylolytic enzymes. Aqueous suspensions of maize starch were treated at different temperatures to obtain different degrees of gelatinization, from 25 °C (control without gelatinization) until 95 °C. Heated samples were then incubated with a glucoamylase. The enzymatic activity was measured by the glucose released during the digestion time by using a standard glucose oxidase method. The initial velocity value of the enzymatic reaction (V_i) was selected as the parameter to quantify the degree of starch gelatinization (DG). Changes in granule morphology and the starch available for hydrolysis were evaluated by photomicrographs. The new method was standardized and compared with DSC and viscosity measurements in order to check its efficiency, considering the DG observed by photomicrographs. A good agreement was observed between the DG calculated by V_i and by DSC (correlation coefficient r = 0, 97), thus V_i reflect the degree of starch gelatinization as well as DSC. These results show that the developed enzymatic procedure is an effective method to evaluate the DG in starchy foods and feeds.     

Image Analysis of Gluten-free Breads Prepared with Chestnut and Rice Flour and Baked in Different Ovens

In this study, the effects of chestnut flour and xanthan–guar gum blend–emulsifier DATEM mixture addition on macro- and microstructure of rice breads baked in conventional and infrared–microwave combination ovens were investigated by using the images obtained by a scanner and scanning electron microscopy (SEM). Pore area fraction, pore size distribution, and roundness values of pores were determined. The highest pore area fraction values were obtained in breads prepared by replacement of 46 % of rice flour with chestnut flour containing xanthan–guar gum blend–DATEM mixture and baked in an infrared–microwave combination oven. On the other hand, rice breads containing no additives or chestnut flour had the lowest pore area fraction values. Infrared–microwave combination baking increased both pore area fraction values and total number of pores. Infrared–microwave combination baking caused approximately 23–28 % increase in number of the small pores (0–5 mm²) in rice breads and 71 % increase in number of the large pores (>10 mm²) in chestnut–rice breads. The fiber content and larger starch granules of chestnut flour contributed towards the stabilization of gas bubbles resulting in better crumb structure. More homogenous pore distributions were observed when additives and an infrared–microwave combination oven were used. When microstructure of gluten-free breads was investigated, it was seen that starch granules in chestnut–rice breads baked in an infrared–microwave combination oven did not disintegrate completely.     

Gelatinization of Starch and Modified Starch

Gelatinization temperatures of starch and hydroxyethyl starch was determined using Differential Scanning Calorimetry (DSC), hot stage microscopy and viscography. The gelatinization temperature based on peak temperature of DSC is incorrect. Viscograph overestimates the gelatinization temperature. Hot stage microscopy based on visual observation gives the correct gelatinization temperature. DSC gives the heat of gelatinization which is helpful in estimating heat requirement during cooking of starch. Hydroxyethylation of starch reduces gelatinization temperature and heat of gelatinization for starch.     

加工对饲料蛋白质体外消化率和糊化度的影响

采用胃蛋白酶-胰蛋白酶两步法和β-淀粉酶法分别测定饲料蛋白质体外消化率和淀粉糊化度,探讨了粉碎、调质和制粒对二者的影响.试验结果表明:饲料调质前的蛋白质体外消化率与粉碎粒度呈显著负相关(P＜0.01),而淀粉糊化度受粒度影响很小;调质使蛋白质体外消化率和淀粉糊化度增加9%～12%和11%～15%,二者的增加值与粒度也呈负相关;制粒使蛋白质体外消化率和淀粉糊化度进一步增加2%～3%和3%～5%.对于蛋白质体外消化率,原料性质和粉碎贡献率为82%～83%,调质为13%～15%,制粒为3%～4%;对于淀粉糊化度,原料性质和粉碎贡献率为52%～56%,调质为30%～38%,制粒为10%～14%.     

Cold Gelatinization of Starch

The cold gelatinization of starch and the subsequent leaching with water has been studied by a spectrophotometric difference method. It has been proved that the gel formation can only take place if amylose has first leached out of the starch granules and that amylopectin is the predominant gel forming component of starch.