Physicochemical Properties and In Vitro Starch Digestibility of Cooked Rice from Commercially Available Cultivars in Canada

The influence of amylose content, cooking, and storage on starch structure, thermal behaviors, pasting properties, and rapidly digestible starch (RDS), slowly digestible starch (SDS), and resistant starch (RS) in different commercial rice cultivars was investigated. Long grain rice with high‐amylose content had a higher gelatinization temperature and a lower gelatinization enthalpy than the other rice cultivars with intermediate amylose content (Arborio and Calrose) and waxy type (glutinous). The intensity ratio of 1047/1022 cm^–1 determined by Fourier Transform Infrared (FT‐IR), which indicated the ordered structure in starch granules, was the highest in glutinous and the lowest in long grain. Results from Rapid ViscoAnalyser (RVA) showed that the rice cultivar with higher amylose content had lower peak viscosity and breakdown, but higher pasting temperature, setback, and final viscosity. The RDS content was 28.1, 38.6, 41.5, and 57.5% in long grain, Arborio, Calrose, and glutinous rice, respectively, which was inversely related to amylose content. However, the SDS and RS contents were positively correlated with amylose content. During storage of cooked rice, long grain showed a continuous increase in pasting viscosity, while glutinous exhibited the sharp cold‐water swelling peak. The retrogradation rate was greater in rice cultivars with high amylose content. The ratio of 1047/1022 cm^–1 was substantially decreased by cooking and then increased during storage of cooked rice due to the crystalline structure, newly formed by retrogradation. Storage of cooked rice decreased RDS content and increased SDS content in all rice cultivars. However, no increase in RS content during storage was observed. The enthalpy for retrogradation and the intensity ratio 1047/1022 cm^–1 during storage were correlated negatively with RDS and positively with SDS (P ≤ 0.01).     

Molecular and Gelatinization Properties of Rice Starches from IR24 and Sinandomeng Cultivars

The differences in pasting properties involving gelatinization and retrogradation of rice starches from IR24 and Sinandomeng cultivars during heating‐cooling processes were investigated using a Rapid Visco Analyser (RVA)and a dynamic rheometer. The results were discussed in relation to the molecular structure, actual amylose content (AC), and concentration of the starches. Generally, both starches possessed a comparable AC (≈11 wt%), amylose average chain length (CL), iodine absorption properties, and dynamic rheological parameters on heating to 95°C at 10 wt% and on cooling to 10°C at higher concentrations. In contrast to Sinandomeng, IR24 amylose had a greater proportion of high molecular weight species and number‐average degree of polymerization (DP_n). IR24 amylopectin possessed a lower DP_n and greater CL, exterior CL (ECL), and interior CL (ICL). Comparing the results of RVA analysis and dynamic rheology, the gelatinization properties and higher retrogradation tendencies of IR24 starch can be related to the structural properties and depend on starch concentration. In addition, the exponent n of starch concentration for storage moduli at 25°C (G′₂₅ ∝ Cⁿ) increased linearly with increasing AC.     

Structural Characteristics,Properties, and In Vitro Digestibility of Rice

Using rice samples derived from normal rice cultivars and endosperm starch mutant, we investigated key factors contributing to the enzyme digestibility of steamed rice grains. The chemical composition of polished rice grains, structural features of endosperm starch, and enzyme digestibility of steamed rice grains were examined. The protein content of polished rice grains was 4.6–9.1%, amylose content was 4–27%, the DP_n of purified amylose was 900–1,600, the amylopectin short/long chain ratio was 1.2–5.9, and the enzyme digestibilities of steamed polished rice grains were 0.9–12.6 °Brix. Amylose content and RVA parameters (viscosity, breakdown, and setback) correlated significantly with enzyme digestibility of steamed rice grains. Multiple regression formulas were constructed to predict digestibility of steamed rice grain as a function of the molecular characteristics of the starch. When both amylose content and the short/long chain amylopectin ratio were used as predictor variables, they accounted for >80% of the observed variance in digestibility of steamed rice grains. Multiple regression revealed that the more digestible rice samples had starch with a lower amylose content and more short‐chain amylopectin. Reassociation of amylose‐lipid complex and recrystallization of amylopectin in the stored steamed rice grains was monitored by differential scanning calorimetry (DSC), and the observed retrogradation properties were related to the structural characteristics of starch and to the enzyme digestibility of steamed rice grains.     

Molecular Structure and Some Physicochemical Properties of Buckwheat Starches

The molecular structure and pasting properties of starches from eight buckwheat cultivars were examined. Rapid viscograms showed that buckwheat starches had similar pasting properties among cultivars. The actual amylose content was 16–18%, which was lower than the apparent amylose content (26–27%), due to the high iodine affinity (IA) of amylopectin (2.21–2.48 g/100 g). Amylopectins resembled each other in average chain‐length (23–24) and chain‐length distributions. The long‐chains fraction (LC) was abundant (12–13% by weight) in all the amylopectins, which was consistent with high IA values. The amyloses were also similar among the cultivars in number‐average DP 1,020–1,380 with 3.1–4.3 chains per molecule. The molar‐based distribution indicated that all the amyloses comprised two molecular species differing in molecular size, although the weight‐based distribution showed a single species. A comparison of molecular structures of buckwheat starches to cereal starches indicated buckwheat amylopectins had a larger amount of LC, and their distributions of amylose and short chains of amylopectin on molar basis were similar to those of wheat and barley starches.     

Structure,Physicochemical Properties,and In Vitro Starch Digestibility of Yellow Pea Flour Modified with Different Organic Acids

The objective of this study was to produce a pea flour ingredient with higher slowly digestible (SDS) and resistant (RS) starch fractions for functional food applications. Heat‐moisture treated flour (HMTF) in the presence of citric, gallic, or vanillic acids and esterified flour (EF) with citric acid were prepared and analyzed for structure and functionality using in vitro starch digestibility, differential scanning calorimetry, Rapid Visco Analyzer, swelling factor (SF), amylose leaching (AML), optical microscopy, and Fourier transform infrared (FT‐IR) spectroscopy. Significant (P < 0.05) increases in SDS and RS content of HMTF and EF were observed. Whereas the granule integrity and the birefringence were not affected by modification, the degree of crystalline order, which was determined by FT‐IR 1,047/1,022 cm⁻¹ peak ratio, was decreased. Gelatinization enthalpies of modified flour were lower than that of native flour, whereas the gelatinization endotherms of HMTF were shifted to higher temperatures and those of EF to lower temperatures. Pasting properties were also affected greatly by both treatments. HMTF demonstrated reduced SF and AML, whereas EF had reduced SF and increased AML. Further, the extent of changes in the structure and functionality of HMTF depended on the type of acid utilized. Overall, heat‐moisture treatment with an organic acid and esterification were effective modifications to produce a pea flour ingredient with enhanced SDS and RS content.     

Granule Size Distribution and Chemical Composition of Starches from 12 Soft Wheat Cultivars

Granule size distribution of wheat starch is an important characteristic that can influence its chemical composition, which in turn may affect its functionality. The granule size distribution and chemical composition of soft wheat starches were characterized and compared and relationships among those properties were identified. Thirty-four starch samples from 12 soft wheat cultivars grown in the eastern half of the United States were examined. Granule size distribution was characterized using a laser light-scattering technique. Amylose and phospholipid contents were determined using colorimetric procedures. A clear trimodal distribution of granule sizes was shown by 26 out of 34 starch samples: small granules with diameters <2.8 μm, midsize granules with diameters of 2.8–9.9 μm, and large granules with diameters >9.9 μm. Volume% distribution of granules within the three size classes had ranges of 9.7–15.2% (small), 13.4–27.9% (medium), and 57.9–76.9% (large). Highly significant differences were seen among the cultivars for volume% of granules within the ranges of 9.9–18.5 μm and 18.5–42.8 μm. Cultivar specific surface area means also differed. The environment affected granule size distribution, with some cultivars exhibiting more variation than others. Pioneer 2555 was the least variable, whereas Pioneer 2550 and Geneva were the most variable cultivars. Mean total amylose (TAM), apparent amylose (AAM), and lysophospholipid (LPL) values varied significantly among cultivars. TAM was positively correlated with the volume% of granules of 9.9–18.5 μm. LPL was negatively correlated with mean starch granule diameter and positively correlated with specific surface area of granules, indicating smaller granules tended to have higher lipid contents. Results suggest that significant differences exist in granule size distribution of soft wheat starches and affect starch chemical composition. Data also suggest it is possible that lipid is preferentially associated with the biosynthesis of small starch granules.     

Properties of Starches from Several Low‐Amylose Rice Cultivars

The starch properties of five low‐amylose rice cultivars, Yawarakomachi, Soft 158, Hanabusa, Aya, and Snow Pearl, were compared with those of two normal amylose rice cultivars, Nipponbare and Hinohikari. There were no large differences in the distributions of the amylopectin chain length determined by high‐performance anion‐exchange chromatography, and the starch gelatinization properties determined by differential scanning calorimetry, between normal and low‐amylose rice cultivars. Results obtained using rapid viscosity analysis indicated that low‐amylose rice starches had lower peak viscosity, breakdown, and setback values than normal amylose rice starches. Starch granules from low‐amylose rice cultivars had a higher susceptibility to glucoamylase than those from normal amylose rice cultivars. The results of this study showed some differences between normal and low‐amylose rice starches in pasting properties and enzymatic digestibility.     

Molecular Structure and Some Physicochemical Properties of High‐Amylose Barley Starches

The molecular structure and some physicochemical properties of starches from two high‐amylose cultivars of barley, high‐amylose Glacier A (HAG‐A) and N (HAG‐N), were examined and compared with those of a normal cultivar, Normal Glacier (NG). The true amylose contents of HAG‐A, HAG‐N, and NG were 41.0, 33.4, and 23.0%, respectively. Iodine affinities before and after defatting of starch, and thermograms of differential scanning calorimetry, indicated that HAG‐A and HAG‐N starches had a higher proportion of amylose‐lipid complex than did NG starch. The amylopectins from HAG‐A and HAG‐N were similar to NG amylopectin in average chain length (18–19), β‐amylolysis limit (β‐AL 56–57%), number‐average degrees of polymerization (DP_n 6,000–7,500) and chain length distribution. Very long chains (1–2%) were found in amylopectins from all cultivars. HAG‐A amylopectin had a larger amount of phosphorus (214 ppm) than the others. The amyloses from HAG‐A and HAG‐N resembled NG amylose in DP_n (950–1,080) and β‐AL (70–74%). However, HAG‐A and HAG‐N had a larger number of chains per molecule (NC 2.4–2.7) than NG amylose (1.8) and contained the branched amylose with a higher NC (9.5–10.6) than that of NG amylose (5.8), although molar fractions of the branched amylose (15–20%) were similar.     

Impact of Buckwheat Flavonoids on In Vitro Starch Digestibility and Noodle‐Making Properties

The effects of various buckwheat materials (buckwheat flour [BF], dietary fiber extract [DE], flavonoids extract [FE], and rutin‐enhanced flavonoids extract [REFE]) on starch digestibility and noodle‐making properties were evaluated. When FE and REFE were incorporated into noodles, the amount of rapidly digestible starch and the predicted glycemic index (pGI) were reduced. However, BF and DE did not significantly decrease the pGI value of noodles. When assessing noodle properties, hardness was increased with increasing content of buckwheat materials, whereas other texture parameters were not significantly affected by buckwheat addition. All noodles were similar in regard to water absorption and swelling index, but cooking loss was slightly increased in FE and REFE noodles. FE and REFE demonstrated higher flavonoid stability during noodle making and, additionally, were more effective at reducing starch digestibility than BF and DE. REFE, specifically, does not generate quercetin (the cause of a bitter taste), and, therefore, REFE was effective in suppressing the hydrolysis of starch in the noodles, lowering the pGI.     

不同中薯系列马铃薯淀粉组成与理化性质的差异分析

为分析不同品种马铃薯淀粉组成与理化性质的差异,本研究以15个不同品种中薯系列马铃薯为原料提取淀粉,并对其组成和理化性质进行了检测及相关性分析。光学显微镜和扫描电镜结果表明,马铃薯淀粉颗粒的粒径分布范围广,颗粒形貌存在差异,小颗粒多为卵圆形,大颗粒多为椭圆形、拉长形以及不规则形。不同马铃薯淀粉的理化性质存在显著差异,其溶解度、膨润力范围分别为25.92%~28.74%,4.90~6.26 g·g^-1;糊化初始温度(T_o)、峰值温度(T_p)、终止温度(T_c)、糊化焓值(ΔH)范围分别为61.44~65.55℃、64.49~68.69℃、67.87~72.54℃、7.21~13.49 J·g^-1;峰值黏度、衰减值、回生值范围分别为2 499.3~3 220.4、514.0~2 218.4、401.0~884.1 BU。相关性分析结果表明,马铃薯淀粉中磷含量与峰谷黏度呈显著正相关,与溶解度呈显著负相关;平均粒径D[4,3]与短程有序参数1 045/1 022 cm^-1 和1 022/995 cm^-1均呈显著正相关;T_o与峰值黏度呈显著负相关;糊化温度与峰值黏度和崩解值均呈显著负相关,与峰谷黏度、最终黏度和回生值均呈显著正相关。本研究结果可为中薯系列马铃薯淀粉在食品加工中的应用提供科学依据。     

Effect of Rice Starch-Lipid Complexes on In Vitro Digestibility,Complexing Index,and Viscosity

Effects of nonwaxy (21% amylose, 79% amylopectin) and waxy (100% amylopectin) rice starch-lipid complexes on the rate of in vitro digestibility were determined. Long-chain (≥C:18) saturated emulsifiers reduced digestibility more than short-chain (<C:18) saturated and unsaturated emulsifiers when complexed with nonwaxy and waxy rice starch. The largest decrease in digestibility (33%) was achieved with Polyaldo 10-1-2 (100% C18:0 with decaglyceryl monostearate modification) for nonwaxy rice. Waxy rice starch did not complex with most of the emulsifiers, in contrast to nonwaxy rice starch. Most of the emulsifiers that reduced digestibility by 10% or less were composed of unsaturated monoglycerides, including some acetylated and succinylated monoglycerides. The fluid behavior of nonwaxy rice starch-emulsifier solutions was more pseudoplastic than waxy rice starch-emulsifier solutions. The consistency index varied with emulsifiers. The nonwaxy rice starchemulsifier solutions and some of those prepared using waxy rice starch would be suitable for semisolid food applications. The waxy rice starchemulsifier solutions with low consistency (0.4–0.7) and high-flow behavior (0.7–0.8) indices would be suitable for beverage applications.     

Differences in Carbohydrate Composition and Digestion In Vitro of Selected Barley Cultivars as Influenced by Pearling and Cooking

Among common cereals, barley is a low glycemic index food. In an attempt to better understand this character, the nutritional properties of glycemic carbohydrates and dietary fiber concentrations of nine cultivars were evaluated. The cultivars were selected based on botanical variations and commercial value to investigate the impact of pearling and cooking on nutritional properties. Each cultivar was pearled into four fractions ranging from hull removal only to hull, bran, germ, and crease removal. The study showed that botanical class and degree of pearling significantly affect the carbohydrate composition and digestion indices of barley. Waxy starch cultivars had less total starch and more rapidly digestible starch (RDS), rapidly available glucose (RAG), and β‐glucan than the other nonwaxy cultivars. Regardless of the barley type, the less pearled kernels had significantly lower total starch and higher total low molecular weight sugars, insoluble, and total fiber. However, β‐glucan content was fairly comparable in the whole grain and pearled fractions. Cooking had a significant effect on nutritional properties of Celebrity and AC Klinck cultivars. The only consistent significant difference between raw and cooked barley was resistant starch (RS), which increased after cooking regardless of cultivar or fraction. The study showed that barley cultivar and carbohydrate composition significantly affected starch digestion with some cultivar fractions holding a promise for the development of low glycemic index foods.     

Physicochemical Properties and Molecular Structures of Starches from Millet (Pennisetum typhoides) and Sorghum (Sorghum bicolor L. Moench) Cultivars in Nigeria

Some physicochemical properties and molecular structures of starches from millet (Pennisetum typhoides, Doro and Gero) and sorghum (Sorghum bicolor, red and white) in Nigeria were examined. Starch granules of millet and sorghum were 3–14 μm and 4–26 μm in diameter, respectively. Millet cultivars had similar peak viscosities (204–205 RVU) on pasting, while sorghum showed similar minimum viscosities (155–156 RVU). The actual amylose content (%) calculated from iodine affinity (IA, g/100 g) was 20.1 and 21.4 for sorghum and 21.3 for millet. The IA of amylopectin was high (1.27–1.42) and its average chain lengths were 20–21 with β‐amylolysis limit of 56%. Amylopectins showed a polymodal molecular weight distribution on a molar basis. The distributions differed among the samples with a higher amount of larger molecules in Doro and red sorghum. Weight‐ and molar‐based distributions of debranched amylopectins on HPSEC were polymodal with weight‐based distribution showing presence of long chains. Peak DP values for A+B₁ and B₂+B₃ chain fractions were 13–16 and 42–43, respectively. The (A+B₁)/(B₂+B₃) ratio on molar basis (9.0–11.5) was similar to maize and rice amylopectins. Peak DP on molar‐based distribution for white sorghum and millet amyloses were similar (490–540) and the DP_n range was narrow (1,060–1,300), but weight‐based distribution profiles differed. The average chain lengths were 260–270 with 3.9–4.8 chains per molecule.     

不同类型日粮奶牛体外消化性能与甲烷产生量比较

为控制动物甲烷排放提供参考依据,以奶牛为瘤胃液供体动物,采用体外消化法进行了日粮类型对CH4产生量及其与消化性能关系的研究。结果表明,日粮精粗比均为40∶60的条件下,粗料为玉米秸秆青贮日粮的CH4产生量、消化单位干物质（DM）的CH4产生量、单位消化能量的CH4产生量比粗料为干玉米秸秆日粮分别减少了30%、37%、32%,差异显著（P〈0.05）;粗料均为玉米秸秆青贮的条件下,精粗比60∶40日粮的CH4产生量、消化单位DM的CH4产生量、单位消化能量的CH4产生量比精粗比40∶60日粮分别减少了21%、23%、23%,差异显著（P〈0.05）。玉米秸秆经过青贮处理或适当增加日粮中精料比例可以显著减少甲烷的产生,同时可以提高干物质消化率和消化能比例。     

Changes in Retrogradation Properties of Rice Starches with Amylose Content and Molecular Properties

The increases in storage modulus (G′), retrogradation enthalpy change (ΔH) and ΔH‐related Avrami kinetic parameters of gelatinized rice starch dispersions at 25% (w/w) were investigated with respect to storage period, amylose content (AC), and molecular properties. Three high‐AC and five low‐AC rice cultivars were compared for understanding the multiple influences of AC and molecular properties involved. After refining the results of correlation analysis, the G′ of just‐cooled samples changed positively, mainly with AC and additionally with the average chain length of amylose (CL_AM) and the weight ratio of extra‐long plus long chains to short chains of amylopectin (AP) (r_APchain). The developed ΔH on short‐term storage (10 days) elevated with increasing AC and CL_AM and decreasing degree of polymerization of AP (DP_AP), but after long‐term aging for one to three months with increasing r_APchain, especially for the low‐AC cultivars examined. Greater Avrami rate constants for retrogradation could be attributed to the combination of a lower DP_AP and r_APchain or AP chain length and a greater CL_AM. The polynomials using these critical factors to describe the retrogradation parameters were elucidated and could account for 85–99.6% of data deviations.     

Effect of Whole Grain Wheat Flour on the Mixing Properties,Oil Uptake,and In Vitro Starch Digestibility of Instant Fried Noodles

The effects of whole grain wheat (WGW) flour on the quality attributes of instant fried noodles were characterized in terms of mixing and oil‐resisting properties as well as in vitro starch digestibility. Higher water absorption and shorter kneading time were required to obtain the optimally mixed dough from WGW flour, and the presence of nonstarch components in the WGW flour lowered the thermal conductivity of the noodles. The use of WGW flour produced instant fried noodles with oil uptake reduced by 30%, which could be correlated with the less porous structure confirmed by the surface and cross‐sectional scanning electron microscope images. When the instant fried noodles were subjected to in vitro starch digestion, the use of WGW flour was effective in suppressing the hydrolysis of starch in the noodles, and the predicted glycemic index of the WGW noodles (80.6) was significantly lower than that of the white wheat noodles (83.3).     

超声处理对糯米与非糯米淀粉结构和消化性的影响

为了探究超声处理对糯米和非糯米淀粉颗粒结构和功能特征的影响,改善稻米淀粉的品质,本试验以糯稻(Y26)、非糯稻(Y9)淀粉为材料,对其进行超声处理,分析处理后淀粉的结构热力学性质及消化特性。结果表明,与对照组相比,两种淀粉经超声处理后各性质变化趋势相似,淀粉颗粒表面产生凹陷、直链淀粉含量升高、结晶度下降、傅立叶变换红外光谱(FTIR)的1 047 cm^-1/1 022 cm^-1比值先增加后降低,弹性模量(G′)降低,凝胶强度减弱,糊化终止温度与起始温度之差(Tc-To)减小,快速消化淀粉(RDS)和抗性淀粉(RS)含量增加,但两种淀粉的变化程度有一定差异。本研究初步奠定了生产中根据对淀粉性质的需求来确定合适超声处理条件的理论基础。     

Investigation of Digestibility In Vitro and Physicochemical Properties of A‐ and B‐Type Starch from Soft and Hard Wheat Flour

In this study, the functional properties of A‐ and B‐type wheat starch granules from two commercial wheat flours were investigated for digestibility in vitro, chemical composition (e.g., amylose, protein, and ash content), gelatinization, retrogradation, and pasting properties. The branch chain length and chain length distribution of these A‐ and B‐type wheat starch granules were also determined using high‐performance anion exchange chromatography (HPAEC). Wheat starches with different granular sizes not only had different degrees of enzymatic hydrolysis and thermal and pasting properties, but also different molecular characteristics. Different amylose content, protein content, and branch chain length of amylopectin in A‐ and B‐type wheat starch granules could also be the major factors besides granular size for different digestibility and other functional properties of starch. The data indicate that different wheat cultivars with different proportion of A‐ and B‐type granular starch could result in different digestibility in wheat products.     

Effect of Growth Location in the United States on Amylose Content,Amylopectin Fine Structure,and Thermal Properties of Starches of Long Grain Rice Cultivars

Starch was isolated from kernels of 27 rice samples consisting of nine U.S. long grain rice cultivars grown in three different locations (Missouri, Arkansas, Texas). Amylose (AM) content of the starches and the fine structure of the respective amylopectin (AP) were determined and used to explain differences observed in gelatinization properties. The AM content of rice cultivars grown at the lower temperature Missouri location increased 0.4–3% and 0.5–4% when compared with the same rices grown in Arkansas and Texas, respectively. AP values of the rice samples were isolated, debranched, and separated by low‐pressure size‐exclusion chromatography. The eluted AP linear chains were divided into three fractions to represent extra long (FrI), long (FrII), and short chains (FrIII). The corresponding average degree of polymerization (DP_n) at the peaks of fractions FrI, FrII, and FrIII were 100, 39, and 16, respectively. Total carbohydrate analysis of the fractions indicated that cultivars grown in Missouri had a consistently higher proportion of FrIII and lower proportion of FrII as the same cultivars grown in Arkansas and Texas. Furthermore, the Missouri samples showed a shift toward shorter DP_n in FrII and FrIII and had more of the shortest chain components (DP_n < 6) of AP. The proportion of FrI did not follow a trend and varied depending on the cultivar and across location. Thermal analysis indicated that the higher temperature growth environments (Arkansas and Texas) resulted in higher onset, peak, and heat of gelatinization for the starches, suggesting longer cooking time and higher heat requirement. Overall, the data support the nonfield findings of other researchers that higher growing temperature results in AP with more DP_n short chains that are within a range of DP >10 to form consistent crystallites, and thus results in higher gelatinization temperatures and enthalpies.