Study of Protein Detection and Ultrastructure of Brazilian Rice Starch during Alkaline Extraction

Alkaline extraction of Brazilian rice starch was studied. UV/Vis and fluorescence spectroscopy were employed as an innovative way for protein detection during the extraction. Moreover, the results were compared to the traditional biuret colorimetric test. In parallel, the ultrastructure of starch was monitored by small angle X‐ray scattering (SAXS) during every extraction step. A progressive reduction of the granules organization was observed, which was also detected by the loss of birefringence under polarized light. The external integrity of starch granules after complete removal of proteins was maintained, as verified by scanning electron microscopy (SEM). The size of the granules, determined by the Mie scattering method varied between 3 and 8 µm.     

Starch Granule‐Associated Proteins and Polypeptides: A Review

This paper reviews current information regarding the (non‐gluten) proteins which are naturally located in and on starch granules, and which are termed starch granule associated proteins (SGAPs). At least ten major SGAPs can be extracted from most starches and have molecular weights in the range of approximately 5 to 149 kDa. A substantial number of these proteins are located at the starch granule surface, where their presence in association with that of other minor granule components (such as lipids), appears to significantly influence the overall properties of both starch granules and starchy products. The different extraction conditions which can be exploited to selectively remove SGAPs are detailed. Although some SGAPs may serve as supplementary storage proteins, the majority of SGAPs are believed to be starch biosynthetic enzymes, a proportion of which remain trapped within the growing granule structure. The identity and quantities of the biosynthetic enzymes varies with botanical source, genetic variety and even with time. Current knowledge regarding the identities, compositions, locations, properties and functions of several of the more common SGAPs (e.g. the ∼15 kDa friabilin/puroindoline proteins, the ∼30 kDa protein, and the ∼60 kDa starch granule‐bound starch synthase (SGBSS) protein) are reviewed in detail.     

Granule‐bound SSIIa Protein Content and its Relationship with Amylopectin Structure and Gelatinization Temperature of Rice Starch

Starch characteristics such as gelatinization properties determine the quality of various products of rice. The eating, cooking and processing qualities of rice are a function of the gelatinization of rice starch. The gelatinization temperature (GT) of rice is controlled by the starch synthase IIa (SSIIa) gene. In the present study, the amount of the starch‐associated SSIIa protein and its relationship with amylopectin structure and GT were investigated. The results indicated that the starch associated SSIIa protein content was positively correlated with GT and level of amylopectin chains with degree of polymerization 12‐24 (DP12‐24), and negatively correlated with the fraction of chains with DP6‐11 and short chain ratio (SCR), i.e. DP6‐11/DP12‐24 (P<0.001). GT was also negatively correlated with DP6‐11 SCR, and positively correlated with DP12‐24. The SSIIa protein content and amylopectin structure showed significant difference between the two SSIIa single nucleotide polymorphisms (SNPs, i.e. guanine‐cytosine/thymine‐thymine (GC/TT)) groups. Rice with GC and TT SNPs had average SSIIa protein contents of 1.076 and 0.681, respectively. Rice with the GC SNPs displayed a lower amount of chains with DP6‐11 and more chains with DP 12‐24 than those with TT SNPs. A mechanism is postulated to explain how SSIIa could determine the distribution of amylopectin side‐chains, which affects the gelatinization temperature of rice starch.     

Viscosity,Swelling and Starch Leaching During the Early Stages of Pasting of Normal and Waxy Rice Starch Suspensions Containing Different Milk Protein Ingredients

The effects of three milk protein ingredients, sodium caseinate (NaCAS), whey protein isolate (WPI) and skim milk powder (SMP), on the swelling and leaching behaviour of normal and waxy rice starch solutions, during the early stages of pasting, were investigated. It was found that the swelling onset temperature for both starches was increased by NaCAS and SMP but was not affected by WPI. Furthermore, onset temperature determined by the swelling measurements was lower than the onset temperature determined from viscosity measurements. However, the calculated viscometric onset temperature, using the Maron‐Pierce equation and the results of the swelling measurements, was found to be in very good agreement with the measured viscometric onset temperature. This study also showed that the quantity of leached polysaccharides during the early stages of starch pasting was very small, indicating that significant leaching of polysaccharides during pasting primarily occurs after the break‐up of the sheared starch granules.     

Chemical Composition and Structure of Granule Periphery and Envelope Remnant of Rice Starches as Revealed by Chemical Surface Gelatinization

In this work the contribution of molecular structures to the swelling behavior of rice starches was investigated. Rice starches with different amylose contents (0 ‐ 23.4 %) were gelatinized to various degrees (approximately 10, 20, and 50 %) with 13 M aqueous LiCl, and the surface‐gelatinized starch and ungelatinized remaining granules were separated and characterized. The native starches were heated at 85 or 95°C for 30 min in excess water, and the granule envelope remnants were recovered by centrifugation for further characterization. The remaining granules after surface removal exhibited a lower gelatinization temperature and enthalpy, and swelled to a greater extent upon heating than the native counterpart. The amylopectin molecules in granule envelope remnants obtained at 95°C had larger M_w (weight‐average molar mass) and R_z (z‐average gyration radius) than those in remnants obtained at 85°C. The chemical composition and structure of granule envelope remnants obtained at 85°C were different from those obtained at 95°C for the same rice starch cultivar. The results imply that starch periphery may not be responsible for maintaining starch granule integrity during gelatinization and swelling. It is proposed that the composition and structure of the granule envelope remnant that maintains granule integrity are not constant but dynamic. The formation of a semi‐permeable membrane‐like surface structure during gelatinization and swelling is proposed to be a result of molecule entanglement after gelatinization.     

Starch Structure and Digestibility of Rice High in Resistant Starch

Starch digestibility and starch structure of a high‐resistant starch (RS) rice (RS111) was compared to that of a wild rice type (R7954). RS111 exhibited high RS content and incomplete starch hydrolysis in both cooked rice and retrograded rice flour. High RS rice RS111 had a higher λ_max of absorbance and blue value of iodine‐binding starch complex and contained a higher percentage of intermediate chains of amylopectin than R/954. X‐ray diffraction pattern of RS isolated from cooked high RS rice displayed a mixture of B‐ and V‐type that was more resistant to starch hydrolysis by alpha‐amylase. Resistant starch in RS111 is composed mainly of linear amylose and some low‐molecular‐weight amylopectin.     

Starch Paste Stickiness is a Relevant Native Starch Selection Criterion for Wet‐end Paper Manufacturing

The correct choice of selection and quality criteria is critical for most starch applications. In this study, a set of different potato starches, selected for a large variation in natural phosphate content and final viscosity, was cationised and tested in a laboratory scale wet‐end paper manufacturing process. Analysis of further parameters expected to be critical for processing, including amylose content and starch granule size, was also performed. Since no significant correlation was found between any of these parameters and paper processing, further attempts were made to find structural or physico‐chemical explanations for the paper processing performance. Hence, several additional parameters of the starches were determined including amylopectin chain length pattern, phosphate substitution, molecular size distribution, pasting‐texture properties and fragility of the gelatinised granules. Among these parameters, the best correlation found to paper filler retention was stickiness of the starch as measured by texture analysis. The starches that performed best in the paper trials showed rapid granule bursts that could be readily estimated from the width of the pasting curve peaks. Light microscopy of non‐soluble remnant starch obtained after gelatinisation of starch under dilute conditions revealed a high proportion of broken granular structures. It is hypothesised that the degree of phosphorylation, together with a hitherto unknown molecular parameter that is related to starch granule fragility, determines starch paste stickiness, which in turn is an important parameter for wet‐end paper manufacturing.     

Starch granule-associated proteins of hull-less barley (Hordeum vulgare L.) from the Qinghai-Tibet Plateau in China

BACKGROUND: The starch granule‐associated proteins (SGAPs) are the minor components of the starch granules and a majority of them are believed to be starch biosynthetic enzymes. The Qinghai‐Tibet Plateau in China, one of the centres of origin of cultivated barley, is abundant in hull‐less barley resources which exhibit high polymorphism in SGAPs. RESULTS: The SGAPs of hull‐less barley from Qinghai‐Tibet Plateau were analysed by one‐dimensional (1‐D) SDS‐PAGE, 2‐D PAGE and ESI‐Q‐TOF MS/MS. In the 1‐D SDS‐PAGE gel, four proteins including a 80 kDa starch synthase, actin, actin 4 and ATP synthase β‐subunit were identified as novel SGAPs. A total of six different bands were identified as starch granule‐bound starch synthase I (GBSSI) and the segregation of the novel GBSSI bands in F₁ and F₂ seeds derived from yf127 × yf70 was in accordance with Mendel's law. In the 2‐D PAGE gel, 92 spots were identified as 42 protein species which could be classified into 15 functional groups. Thirteen protein species were identified as SGAPs for the first time and multiple spots were identified as GBSSI. CONCLUSION: This study revealed novel SGAPs in hull‐less barley from the Qinghai‐Tibet Plateau in China and these will be significant in further studies of starch biosynthesis in barley. Copyright © 2011 Society of Chemical Industry     

小麦籽粒硬度与淀粉粒蛋白关系的研究和应用

从小麦籽粒硬度与淀粉粒蛋白的相互关系的角度，详细介绍了国内外有关小麦硬度、小麦淀粉粒与蛋白质之间的相互作用、小麦籽粒硬度遗传控制、小麦淀粉粒表性特征对食品质构的影响等的最新研究成果，为客观评价小麦籽粒的硬度、了解小麦淀粉粒蛋白在面团形成过程中的功能，从而帮助育种工作者和谷物生产者更有效地为小麦加工利用提供理想水平的小麦原料、为小麦品质改良研究提供参考依据。     

Gelatinization and Pasting Properties of Waxy and Non‐waxy Rice Starches

Gelatinization and pasting properties of diverse rice types grown in two locations were examined by differential scanning calorimetry (DSC) and rotational rheometry, respectively. The data were compared to previously reported molecular starch properties for these samples: specifically, amylose content, starch molecular weight (M_w), and amylopectin side‐chain‐length distributions. Significant correlations were observed between amylose content, starch M_w, and the weight degree of polymerization of the long side chains of amylopectin F₁(DP_w) and many of the gelatinization and pasting properties measured. Higher amylose content corresponded with increased gelatinization onset (T_o) and peak temperatures (T_p), pasting onset and peak temperatures, and decreased peak and trough viscosity. Starch M_w correlated negatively with T_o, T_p, pasting onset, and peak temperature and positively with peak, trough, final, and breakdown viscosity. Amylopectin with DP_w 59‐78 of F₁(DP_w) correlated with increased T_o, T_p, pasting onset and peak temperature, and decreased peak, trough, final and breakdown viscosity. Pasting properties were also somewhat related to DP_w 21 of shorter side chains of amylopectin (F₂(DP_w)). Significant correlations between F₂(DP_w) and peak, final, and breakdown viscosity were observed (r = −0.447*, −0.391*, −0.388*, peak, final, and breakdown viscosity, respectively).     

Laboratory‐scale Dry/Wet‐Milling Process for the Extraction of Starch and Gluten from Wheat

A laboratory‐scale process is presented for the manufacture of starch and gluten from wheat. Main feature of this process is that whole wheat kernels are crushed dry between smooth rolls prior to wet disintegration in excess water in such way that gluten formation is prevented and fibres can be removed by sieving. Centrifugation of the endosperm suspension yields a dough which can be separated into starch and gluten using an established batter process. The results suggest that starch recovery is increased in comparison to a conventional wheat flour process without a concomitant decrease in protein recovery. Although starch purification was omitted, a total starch with a low protein content is obtained. On the other hand, the protein content of the gluten fraction is rather low due to difficulties in removing the starch. Despite this, the effect on dough mechanical properties by the addition of gluten obtained from wet‐milled wheat is comparable to the effect of gluten from flour.     

Digestibility and Pasting Properties of Rice Starch Heat‐Moisture Treated at the Melting Temperature (Tm )

Non‐waxy and waxy rice starches adjusted to 20% moisture (wet based, w.b.) were heated in a differential scanning calorimeter to determine the optimum parameters for producing slowly digestible starch (SDS). Starches heated to the temperature of melting (T_m) and held for 60 min in the calorimeter showed a slow digestibility compared to unheated samples. Digestibility decreased by 25 and 10%, respectively, for non‐waxy and waxy rice starches relative to non‐treated starches. Heat‐moisture treatment of waxy corn, non‐waxy corn and wheat starches at the T_m determined for non‐waxy rice starch did not result in significant decreases in digestibility. For waxy rice starches heat‐treated in microwave or conventional ovens at the T_m , there were slight but significant increases in digestibility of the treated starches compared to non‐treated starches at all incubation times. Digestibility was higher for starches heated for 30 min than for 60 min. Non‐waxy rice starches did not show any significant changes in digestibility. Heat‐moisture treatment at the T_m and the holding time of sample at that temperature in a differential scanning calorimeter were found to be significant to the formation of slowly digestible heat‐moisture treated starch.     

籼米中淀粉粒结合蛋白的分离鉴定及提取工艺优化

采用十二烷基硫酸钠（sodium dodecyl sulfate,SDS）缓冲体系分离提取碱洗籼米粉中的淀粉粒结合蛋白（starch granule-associated proteins,SGAPs）,经高效液相色谱-串联质谱法鉴定表明：碱洗得到上、中、下层籼米淀粉中的SGAPs均主要为淀粉合成酶I（granule-bound starch synthase I,GBSS I）,其他组分略有差别;其中以中层SGAPs含量最高,GBSS I达99.8%,谷蛋白质量分数仅为0.11%。采用响应面优化中层淀粉SGAPs的提取参数,得到最优条件为SDS添加量10.90%、煮沸时间4.10?min、MgSO4浓度0.90?mmol/L,此时SGAPs提取量为（1?028.61±0.05）μg/g。     

米糠4种蛋白质的提取与功能性质

按照Osbron法提取米糠中的清蛋白、球蛋白、醇蛋白、谷蛋白,并对4种蛋白进行功能性质评价。结果表明:米糠中清蛋白、球蛋白、醇蛋白、谷蛋白占米糠蛋白总量依次是56.93%、20.84%、3.167%、19.06%;等电点依次是pH4.0、4.0、5.0、4.6。4种蛋白的功能性质对比评价表明:清蛋白的持水性最大,醇蛋白的乳化性最高,清蛋白在等电点处的起泡性最差。SDS-PAGE凝胶电泳分析表明:清蛋白分子的亚基组成分子质量为95.43、76.51、52.85kD;球蛋白的亚基组成分子质量为103.12、76.51kD;醇蛋白的亚基组成分子质量为14.00kD;谷蛋白的亚基组成分子质量为36.29、20.00、14.00kD。     

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。     

Characterization of Physical Properties of Flour and Starch Obtained from Gamma‐Irradiated White Rice

Physical and structural characteristics of rice flour and starch obtained from gamma‐irradiated white rice were determined. Pasting viscosities of the rice flour and starch, analyzed by using a Rapid Visco Analyser, decreased continuously with the increase in irradiation dosage. Differential scanning calorimetry showed that gelatinization onset, peak and conclusion temperatures of rice flour and starch changed slightly but the enthalpy change decreased significantly with increase of irradiation dosage. All irradiated starch displayed an A‐type X‐ray diffraction pattern like the native starch. Gel permeation chromatography showed that the blue value ratio of the first peak (amylopectin) to the second one (amylose) decreased with the increase of the irradiation dosage. The weight‐average molecular weight (M_w) and gyration radius (R_z) of amylopectin analyzed by using HPSEC‐MALLS‐RI (high‐performance size‐exclusion chromatography equipped with multiangle laser‐light scattering and refractive index detector) decreased gradually from 1.48×10⁹ (M_w) and 384.1 nm (R_z) of native rice starch to 2.36×10⁸ (M_w) and 236.8 nm of 9 kGy‐irradiated starch. The branch chain‐length distribution of amylopectins determined by HPAEC‐ENZ‐PAD (high‐performance anion‐exchange chromatography with amyloglucosidase post‐column on‐line reactor and pulsed amperometric detector) showed that gamma irradiation had no significant effect on the amylopectin branch chains with 13≤DP≤24 and 37≤DP, but produced more branch chains with 6≤DP≤12 when the irradiation dosage was less than 9 kGy. It might be deduced that gamma irradiation caused the breakage of the amylopectin chains at the amorphous regions, but had little effects on the crystalline regions of starch granules, especially at low dosage irradiation.     

Effects of Granule Sizes on Physicochemical Properties of Cross‐linked and Acetylated Wheat Starches

Large and small wheat starch granules were used for cross‐linking and acetylation to determine effects of granule sizes on physicochemical properties of the modified starches. The native and cross‐linked starches from the small granules showed higher phosphorus contents than did those from the large granules. However, the level of phosphate substituents in the modified starches was not significantly different between the large and small granules under the same conditions. In contrast, the large granules had a higher reactivity with acetic anhydride than did the small granules. The phosphate group cross‐linked starch (CS), acetylated starch (AS) and acetylated cross‐linked starch (ACS) from the large granules had lower gelatinization temperatures and higher enthalpies than those from the small granules. The paste viscosities of the CSs from the large granules decreased rapidly, whereas those of the AS or ACS increased significantly as compared with those from the small granules. The pastes of cross‐linked starches from the small granules were more stable than those from the large granules, whereas the pastes of AS and ACS from the large and small granules had similar resistance to freeze‐thaw treatment. Scanning electron microscopy (SEM) also showed that the small granules were less damaged after modification than the large ones. Thus, the different granule sizes resulted in different physicochemical properties of starch after modification.     

Effect of high‐pressure microfluidization on the structure of cassava starch granule

Microfluidization has been applied to modify starch granules. The study was conducted to investigate the effect of microfluidization on the structure and thermal properties of cassava starch–water suspension (20% w/w). The means of optical microscopy, SEM, FTIR spectroscopy, XRD, and DSC were applied to analyze the changes in microstructure, crystallinity, and thermal property. Microscopy observations revealed that native starch granules were oval, round, and truncated in shape. After the microfluidization treatment, a bigger starch granule was partially gelatinized, and a gel‐like structure was formed on a granular surface. No significant difference in XRD patterns of the samples were observed and all samples exhibited A‐type allomorph. Crystallinity decreased with the pressure. Sample treated at 150 MPa contains 17.1% crystalline glucan polymer, lower than that of native granules which have crystallinity of about 25.8%. A lower crystallinity means poor order of crystalline glucan polymer structure in starch granules. The disruption of crystalline order within the granule was also observed by FTIR measurement. Thermal analysis using DSC indicated that the microfluidization treatment brought about a significant decrease of melting enthalpy. The gelatinization enthalpy was 12.0 and 3.0 J/g for the native sample and samples treated under the 150 MPa, respectively. The results indicate that high‐pressure microfluidization process induced the gelatinization of cassava starch, which is evaluated by a percentage of the degree of gelatinization, due to a pronounced decrease with increasing microfluidizing pressure.     

Extraction, denaturation and hydrophobic Properties of Rice Flour Proteins

ABSTRACT: Rice proteins were extracted from defatted rice flour. Turbidity measurement of supernatants revealed isoelectric points of albumin (pH 4.1), globulin (pH 4.3 and pH 7.9), and glutelin (pH 4.8), at which they were precipitated with 82.3 to 93.2% recovery efficiency. Prolamin did not aggregate and precipitate upon pH adjustment, but was precipitated by acetone. Denaturation temperatures (73.3, 78.9, and 82.2 °C) as well as enthalpy values (2.88, 3.14, and 3.79 J/g), of albumin, globulin, and glutelin were different. Prolamin did not show any thermographic denaturation peak. Heat-denaturation of globulin and glutelin resulted in progressive increases in their surface hydrophobicities. Measurement of surface hydrophobicity would be an effective parameter to evaluate rice protein denaturation.