Effect of extrusion cooking on chemical structure,morphology, crystallinity and thermal properties of sorghum flour extrudates

The effect of feed moisture content (10, 14 and 18%) and die temperature (110 and 160 °C) on functional properties, specific mechanical energy (SME), morphology, thermal properties, X-ray diffraction pattern (XRD), Fourier transform infrared spectroscopy (FTIR) and amylose-lipid complex formation of extruded sorghum flour was investigated. Results showed that the extrusion cooking significantly changed the functional properties of extruded sorghum flour. Increasing feed moisture increased the peak gelatinization temperature (T_p), the degree of gelatinization (%) and starch crystallinity (%) while it decreased the gelatinization temperature ranges (T_c - T₀), starch gelatinization enthalpy (ΔH_G) and amylose-lipid complex (%) formation. With increasing die temperature, the degree of gelatinization and amylose-lipid complex formation increased and the starch T_p, T_c-T₀, ΔH_G and crystallinity decreased. The FTIR spectra also showed that the extrusion cooking did not create new functional groups or eliminate them in sorghum protein, whereas the sorghum extrudate protein had random coil conformation.     

Retrogradation of waxy and normal corn starch gels by temperature cycling

Gelatinized waxy and normal corn starches at various concentrations (20–50%) in water were stored under temperature cycles of 4°C and 30°C (each for 1 day) up to 7 cycles or at a constant temperature of 4°C for 14 days to investigate the effects of temperature cycling on the retrogradation of both starches. Compared to starches stored only at 4°C, both starches stored under the 4/30°C temperature cycles exhibited smaller melting enthalpy for retrogradation (ΔH_r), higher onset temperature (T_o), and lower melting temperature range (T_r) regardless of the starch concentration tested. Fewer crystallites might be formed under the temperature cycles compared to the isothermal storage, but the crystallites formed under temperature cycling appeared more homogeneous than those under the isothermal storage. The effect of starch content on the retrogradation was greater when the starch gels were stored under cycled temperatures. The reduction in ΔH_r and the increase in conclusion temperature (T_c) by retrogradation under 4/30°C temperature cycles became more apparent when the starch concentration was lower (20 or 30%). Degree of retrogradation based on melting enthalpy was greater in normal corn starch than in waxy corn starch when starch content was low.     

Development of biodegradable films based on blue corn flour with potential applications in food packaging. Effects of plasticizers on mechanical,thermal, and microstructural properties of flour films

In the present study, blue corn flour films were developed. The cereal grain’s total composition (excluding the pericarp) is used to obtain the films. The plasticizing effects of two different polyols such as glycerol and sorbitol on the mechanical, thermal, and microstructural properties of flour films were researched. The results showed that films plasticized with sorbitol had better mechanical properties and less affinity for water than those plasticized with glycerol. The sorbitol-plasticized films were more rigid and did not lose their integrity when immersed in water. The ATR-FTIR spectra of blue corn flour plasticizer with sorbitol showed the presence of the additional band at 1745 cm⁻¹ characteristic of the vibrational carbonyl peak, which confirms the chemical linkages between sorbitol and a polymeric matrix. The effect of the plasticizer on the glass transition temperature (T_g) was characterized using differential scanning calorimetry (DSC). T_g decreased as the plasticizer content increased. Plasticized glycerol films showed lower T_g values than those with sorbitol. SEM observations showed that it was necessary to add plasticizer to maintain film integrity. The sorbitol-plasticized flour films revealed better adhesion between phases, and these films showed a compact structure.     

Impact of amylose content on starch retrogradation and texture of cooked milled rice during storage

Milled rice from 11 varieties, with amylose levels from 1.2 to 35.6% dry base, were collected to study the impacts of amylose content on starch retrogradation and textural properties of cooked rice during storage. The relationship between amylose content and different properties was determined using Pearson correlation. Starch retrogradation enthalpy (ΔH_r) of cooked rice was determined by differential scanning calorimetry. ΔH_r values were found to be positively correlated with amylose content (0.603 ≤ r ≤ 0.822, P < 0.01) during storage. Textural properties were determined by a Texture Analyser. The hardness of cooked rice showed a positive correlation with amylose content (0.706 ≤ r ≤ 0.866, P < 0.01) and a positive correlation with ΔH_r of cooked rice (r = 0.650, P < 0.01) during storage. The adhesiveness showed a negative correlation with amylose content (−0.929 ≤ r ≤ −0.678, P < 0.01) and a negative correlation with ΔH_r of cooked rice (r = −0.833, P < 0.01) during storage. Hardness showed a negative correlation with adhesiveness (r = −0.820, P < 0.01). These results indicated that amylose content has significant effects on starch retrogradation and textural properties of cooked rice. The cooked rice with high amylose content is easy to retrograde, the cooked rice with low amylose content retrograded slowly. Sarch retrogradation contributes to the changes of textural properties of cooked rice during storage.     

鲜食糯玉米品种热力学特性评价

热力学特性是评价鲜食糯玉米子粒均匀性、热稳定性和回生程度的重要指标。为了解我国鲜食糯玉米品种热力学特性,利用差示扫描量热法(DSC)测定104个鲜食糯玉米品种的热力学特性,并采用主成分分析方法对其结果进行评价。结果表明,鲜食糯玉米104个品种间淀粉热力学特征参数有显著差异,且不同参数中以回生值变异最大,回生样品的终值温度变异最小。相关分析表明,糯玉米淀粉胶凝特征参数起始温度、峰值温度、终值温度两两极显著正相关,糊化范围与峰值指数呈极显著负相关,回生热焓值和回生值呈极显著正相关。将热力学特征参数可简化为4个主成分,累计方差贡献率为86.11%。104个糯玉米品种可分为8大类,其中I和II类分别有53和43个品种,共占供试材料的92.3%,是最主要的两种类型。糯玉米淀粉热力学特征值间有良好的相关性,影响鲜食糯玉米子粒品质最重要的热力学特征值为回生值、热焓值和胶凝温度。     

Differences of Physicochemical Properties Between Chalky and Translucent Parts of Rice Grains

Rice grain chalkiness is an important characteristic, but the difference between chalky and translucent parts in grains is still unclear. Here, we investigated the differences of flour made from the chalky or translucent part of rice grains in three indica and three japonica rice varieties. The chalky flour had significantly lower amylose and protein contents and looser starch granule morphology, and starches in the chalky flour had higher relative crystallinity, higher short chain content but lower long chain content than those in the translucent flour. The water states, determined with nuclear magnetic resonance, differed between the chalky and translucent flour after soaking, cooking and retrograding, and the chalky flour had more bound and free water but less constructural water than the translucent flour. Mostly, the chalky flour had lower viscosity and shorter gel consistency, but higher onset temperature and gelatinization enthalpy than the translucent flour. The results indicated that starch granule morphology would be more indicative than other attributions on pasting and gelatinization properties of chalky and translucent parts of rice grains.     

Microwave irradiation differentially affect the physicochemical properties of waxy and non-waxy hull-less barley starch

Waxy and non-waxy hull-less barley kernels and their isolated starches were irradiated under different microwave conditions (power 640, 720, and 800 W, time 60, 120 and 180 s). Changes in physicochemical properties were studied to investigate the effects of microwave irradiation (MWI) on in-kernel starches and isolated starches. For in-kernel starch, microwave reduced the ratio of 1047/1022 cm⁻¹ wavelengths, gelatinization enthalpy (ΔH_g) and relative crystallinity (RC), indicating that microwave of starch within the cells disrupted the crystalline regions. For isolated starch, microwave decreased the ratio of 1047/1022 cm⁻¹ wavelengths but increased ΔH_g of isolated starch, indicating that microwaving resulted in disruption of amorphous structure and an increase in the amount of remaining double helix structure. Moreover, viscosities of in-kernel starches decreased as microwave power and time increased, but this was not observed in isolated starches. Microwave treatment induced an enhancement of gelatinization temperature for non-waxy starches (NWS) but decreased in waxy starches (WS). Microwave had a greater effect for swelling power and solubility on in-kernel MWI-WS than MWI-WS, whereas the reverse results were found between in-kernel MWI-NWS and MWI-NWS. The results indicated that amylose plays a profound role in the properties of isolated and in-kernel starches during microwaving.     

Study of the mechanism of improvement due to waxy wheat flour addition on the quality of frozen dough bread

Waxy wheat flour (WWF) was substituted for 10% regular wheat flour (RWF) in frozen doughs and the physicochemical properties of starch and protein isolated from the frozen doughs stored for different time intervals (0, 1, 2, 4 and 8 weeks) were determined to establish the underlying reasons leading to the effects observed in WWF addition on frozen dough quality. Using Nuclear Magnetic Resonance (NMR), Differential Scanning Calorimeter (DSC) and X-ray Diffraction (XRD) among others, the gluten content, water molecular state, glutenin macropolymer content, damaged starch content, starch swelling power, gelatinization properties, starch crystallinity and bread specific volume were measured. Compared to RWF dough at the same frozen storage condition, 10% WWF addition decreased dry gluten and glutenin macropolymer contents and T₂₃ proton density of frozen dough, but increased the wet gluten content, T₂₁ and T₂₂ proton density. 10% WWF addition also decreased damaged starch content, but increased starch swelling power, gelatinization temperature and enthalpy, crystallinity of starch and bread specific volume of frozen dough. Results in the present study showed that the improvement observed due to WWF addition in frozen dough bread quality might be attributed to its inhibition of redistribution of water molecules bound to proteins, increase in damaged starch content and decrease in starch swelling power.     

淀粉老化调控对燕麦全粉挤压面条蒸煮品质的影响

燕麦粉不含面筋蛋白,使燕麦全粉面条煮熟后易浑汤、蒸煮损失率大,目前只能温水浸泡复水食用,是限制燕麦更广泛推广的难题之一。为了满足市场对燕麦全粉面条的需求,以利用二级挤压技术生产的燕麦全粉挤压面条为试材,对成型面条进行了调湿老化、蒸制老化及冷冻老化处理,比较了不同老化方式对燕麦全粉挤压面条蒸煮品质的影响。结果表明,调湿老化处理的面条蒸煮损失率最小(2.26%~3.34%),蒸制老化次之(4.19%~5.19%),冷冻老化最大(5.16%~7.97%)。不同老化处理的面条感官评分差异不显著,以调湿老化处理24h的面条感官评分最高(87.2分);调湿老化处理面条的淀粉相对结晶度(12.47%~16.10%)、热焓值(1.044 0~1.056 0J·g-1)及回生值(519.5~558.0cP)均最大,蒸制老化次之,冷冻老化最小。综合分析可知,对燕麦挤压面条进行淀粉老化处理,能够显著降低燕麦全粉挤压面条的蒸煮损失率,最优方式为调湿老化24h。     

Physicochemical characterization and in-vitro digestibility of extruded rice noodles with different amylose contents based on rheological approaches

The physicochemical properties and in-vitro digestibility of extruded rice noodles with different amylose contents were characterized from a rheological point of view. Thermo-mechanical measurements showed that the rice flour with higher amylose contents exhibited greater stability to dual-mixing and higher degrees of starch gelatinization and retrogradation. In addition, greater elastic properties were clearly observed in the high amylose rice samples. The use of high amylose rice flour produced noodles with a harder texture, consequently contributing to reduced cooking loss. Furthermore, the rheological changes of extruded rice noodles were monitored in real time during the in-vitro starch digestion. The rice noodle digesta with higher amylose contents exhibited greater viscosities throughout the simulated oral-gastric-intestinal digestion steps. The flow behaviors of the rice noodle digesta consisted of the Power-law region and infinite shear plateau that were satisfactorily characterized by the Sisko model (R² > 0.99).     

Effect of microwave irradiation on composition,structure and properties of rice (Oryza sativa L.) with different milling degrees

Effects of microwave irradiation on composition, structure, thermal and storage properties of rice with different milling degrees were investigated. Microwave irradiation partially inactivated the lipase and lipoxidase, damaged thiamine, and created puffed rice. In addition, the transition temperatures (T_o and T_P) of rice were shifted to higher temperatures, and the enthalpy of gelatinization decreased after irradiation. The effect was more obvious when the power of microwave was increased. Microstructure analysis showed that stress cracks and some “explosion” were created in rice kernels after microwave irradiation. Storage property analysis indicated that free fatty acid content of all rice samples increased gradually in the process of storage. Microwave irradiation reduced the release of free fatty acids during storage. The higher the power, the lesser the free fatty acids generated. The results suggested that microwave irradiation was potentially applicable for improving storage properties of brown and milled rice.     

Molecular basis of the gelatinisation and swelling characteristics of waxy barley starches grown in the same location during the same season. Part II. Crystallinity and gelatinisation characteristics

Nine waxy barley samples (grown at the same site during the same season) were investigated to identify those molecular aspects of amylopectin structure and architecture which define the order and gelatinisation characteristics. Using ¹³C CP-MAS/NMR it was confirmed that the number of double helices within the starches were approximately constant although differences in crystallinity were identified by X-ray diffraction. These differences in terms of amount of crystalline order correlated well with gelatinisation temperatures. The onset (T_o), peak (T_p) and conclusion (T_c) gelatinisation temperatures were 53.4, 59.2 and 68.1 °C on average with the associated enthalpy (ΔH) of 11.0 and 13.5 J g⁻¹ on a starch and amylopectin basis. Annealing of the starches below T_o elevated T_o, T_p and T_c by +11.9, +8.2 and +5.1 °C on average and sharpened the gelatinisation range (T_c−T_o). Acid hydrolysis after annealing increased T_o, T_p and T_c (especially T_c) by +2.3, +17.4 and +34.7 °C on average. Annealing in the presence of α-amylase elevated similarly the gelatinisation parameters by +10.2, +7.1 and +2.8 °C for T_o, T_p and T_c, respectively. Crystalline lamellae lengths were found to be 5.2±0.7 and 6.2±0.4 nm using high sensitivity differential scanning micro-calorimetry and differential scanning calorimetry, respectively.     

吐丝后不同阶段干旱胁迫对糯玉米子粒产量和淀粉品质的影响

以苏玉糯5号和渝糯7号为材料,试验对照和干旱处理下土壤相对含水量分别为75%和55%,干旱胁迫时间分别为子粒建成期和灌浆充实期,研究结实期不同阶段(子粒建成期和灌浆充实期)干旱胁迫对糯玉米子粒产量和淀粉品质的影响。结果表明,结实期干旱胁迫显著降低子粒产量,且降幅子粒建成期大于灌浆充实期。干旱胁迫下淀粉含量显著降低,总蛋白、球蛋白、谷蛋白含量显著增加,淀粉平均粒径增大、支链淀粉平均链长增加,相对结晶度升高,且影响子粒建成期大于灌浆充实期。糯玉米粉峰值黏度受灌浆充实期干旱胁迫影响较小,在子粒建成期干旱胁迫下显著降低。糯玉米粉热焓值在子粒建成期干旱胁迫下降低,灌浆充实期干旱胁迫下增加。苏玉糯5号回生值干旱胁迫下显著降低,且降幅灌浆充实期较大;渝糯7号回生值受子粒建成期干旱胁迫影响较小,灌浆充实期干旱胁迫下显著增加。     

Analysis of yield attributes and crop physiological traits of Liangyoupeijiu,a hybrid rice recently bred in China

Crop physiological traits of Liangyoupeijiu, a “super” hybrid rice variety recently bred in China, were compared with those of Takanari and Nipponbare in 2003 and 2004 in Kyoto, Japan. Liangyoupeijiu showed a significantly higher grain yield than Nipponbare in both years, and achieved a grain yield of 11.8 t ha⁻¹ in 2004, which is the highest yield observed under environmental conditions in Kyoto. Liangyoupeijiu had longer growth duration and larger leaf area duration (LAD) before heading, causing larger biomass accumulation before heading than the other two varieties. Liangyoupeijiu had a large number of grains and translocated a large amount of carbohydrates from the vegetative organ to the panicle during the grain filling period. The three yield components measured were panicle weight at heading (P₀), the amount of carbohydrates translocated from the leaf and stem to the panicle during the grain filling period (ΔT), and the newly assimilated carbohydrates during grain filling (ΔW). It was found that the sum of P₀ and ΔT were strongly correlated with grain yield when all the data (n = 8) were combined (r = 0.876**). However, there was no significant difference in the radiation use efficiency (RUE) of the whole growth period between Liangyoupeijiu and Nipponbare for both years. Even though the growth duration was shorter, Takanari, an indica/japonica cross-bred variety, showed a similar yield to Liangyoupeijiu in both years. The mean RUE of the whole growth period was significantly higher in Takanari, 1.60 and 1.64 g MJ⁻¹ in 2003 and 2004, respectively, than in Liangyoupeijiu, which had a RUE of 1.46 and 1.52 g MJ⁻¹ in 2003 and 2004, respectively. The high grain yield of Takanari was mainly due to its high RUE compared with Liangyoupeijiu and its large P₀ and ΔT. Our result showed that the high grain yield of Liangyoupeijiu was due to its large biomass accumulation before heading, which resulted from its large LAD rather than its RUE.     

Analysis of quantitative trait loci for some starch properties of rice (Oryza sativa L.): thermal properties, gel texture and swelling volume

To understand the genetic basis of gelatinization temperature (GT), gel textural traits and flour swelling volume, quantitative trait loci (QTL) were mapped for these traits using a doubled haploid (DH) population derived from a cross between indica variety Zai-Ye-Qing 8 (ZYQ8) and japonica variety Jing-Xi 17 (JX17). The results indicated that the starch property parameters were continuously distributed among the DH lines, and some DH lines showed transgressive segregation for all the parameters. A total of 16 QTLs were identified for seven traits. A major QTL, the alk gene on chromosome 6 was significant for the three GT traits, onset temperature (T_o), peak temperature (T_p), and completion temperature (T_c). This locus could explain 49.4, 38.9, and 28.3% of the total variance, respectively, indicating that GT parameters were substantially controlled by the alk gene which has previously been identified for alkali spreading value (ASV). The additive effects of alk on T_o,T_p and T_c were from ZYQ8. Another two QTLs on chromosomes 1 and 7 were also identified for the three GT parameters, whose positive effects were contributed from JX17. Another QTL on chromosome 10 with the positive effects coming from ZYQ8 was significant only for T_c. However, the enthalpy (ΔH) of gelatinization was controlled by two minor QTLs on chromosomes 1 and 7. A major QTL, the Wx gene on chromosome 6 was identified for gel hardness and flour swelling volume which explained 58.8 and 36.6% of the total variances, respectively. Another two QTLs were also detected for flour swelling volume, one of which (qSV-7) could explain 21.4% of the total variance. However, gel cohesiveness was controlled by a major QTL located between alk and Wx on chromosome 6.     

Effect of glutathione on gelatinization and retrogradation of wheat flour and starch

Reduced glutathione (GSH) commonly exists in wheat flour and has remarkable influence on gluten properties. In this study, effect of GSH on the gelatinization and retrogradation of wheat flour and wheat starch were investigated to better understand the GSH-gluten-starch interactions in wheat flour. Compared with wheat starch, wheat flour showed significant decreases in peak and final viscosity, and gelatinization onset temperature with increasing GSH concentration. GSH depolymerized gluten and thereby broke down the protein barrier around starch granules to make the starch easily gelatinized. However, the interaction between GSH and wheat starch restrained starch swelling. GSH addition resulted in weakened structure with higher water mobility in freshly gelatinized wheat flour dispersions but decreased water mobility in wheat starch dispersions. After storage at 4 °C for 7 d, GSH increased elasticity and retrogradation degree in wheat flour dispersions but retarded retrogradation in wheat starch dispersions. The results indicated that GSH promoted retrogradation of wheat flour, which mainly attributed to the depolymerized gluten embedding in the leached starch chains, and inhibiting the re-association of amylose, and subsequently promoted the starch intermolecular associations and starch retrogradation. This study could provide valuable information for the control of the quality of wheat flour-based products.     

Effects of amylose content,cooling rate and aging time on properties and characteristics of rice starch gels and puffed products

This study aimed at investigating the effects of amylose content (AC) of 0.12–19.00% w/w on dry basis, cooling rate (1, 3, 5, and 9 °C/min), and aging time (24, 48, and 72 h) on structure, physical properties and sensory attributes of rice starch-based puffed products. They had an influence upon the crystalline type, and the relative crystallinity (RC). The thermal and physical properties of starch gels were also determined. Amorphism was found for starch gels with 0.12% AC. The polymorphisms (B and V) and differential scanning calorimetric endotherms were found for those with AC ≥4.00%. The RC, retrogradation enthalpy (ΔH_r) and gel hardness increased with AC and aging time. The cooling rate did not affect RC, but increased ΔH_r and gel hardness. The higher AC and aging time resulted in higher hardness, fracturability, crispiness and bulk density, but lower expansion ratio and less oiliness of the puffed products. The hardness, fracturability, crispiness and bulk density of puffed products were well correlated with the RC of starch gel.     

Characterizing leaf gas exchange responses of cotton to full and limited irrigation conditions

Plant responses to water deficit need to be monitored for producing a profitable crop as water deficit is a major constraint on crop yield. The objective of this study was to evaluate physiological responses of cotton (Gossypium hirsutum) to various environmental conditions under limited water availability using commercially available varieties grown in South Texas. Soil moisture and variables of leaf gas exchange were measured to monitor water deficit for various varieties under different irrigation treatments. Lint yield and growth variables were also measured and correlations among growth parameters of interest were investigated. Significant differences were found in soil moisture, leaf net assimilation (A_n), stomatal conductance (g), transpiration rate (T_r), and instantaneous water use efficiency (WUE_i) among irrigation treatments in 2006 while no significant differences were found in these parameters in 2007. Some leaf gas exchange parameters, e.g., T_r, and leaf temperature (T_L) have strong correlations with A_n and g. A_n and WUE were increased by 30–35% and 30–40%, respectively, at 600 μmol (CO₂) m⁻² s⁻¹ in comparison with 400 μmol (CO₂) m⁻² s⁻¹. Lint yield was strongly correlated with g, T_r, WUE, and soil moisture at 60 cm depth. Relative A_n, T_r, and T_L started to decrease from FTSW 0.3 at 60 cm and FTSW 0.2 at 40 cm. The results demonstrate that plant water status under limited irrigation management can be qualitatively monitored using the measures of soil moisture as well as leaf gas exchange, which in turn can be useful for describing yield reduction due to water deficit. We found that using normalized A_n, T_r, and T_L is feasible to quantify plant water deficit.     

Modification of physicochemical properties and in vitro digestibility of wheat flour through superheated steam processing

Native and moistened wheat flours (moisture contents were 13.5 and 27.0%, respectively) were treated with superheated steam (SS) at different temperatures (140 and 170 °C) and times (1, 2 and 4 min). Their physicochemical and digestive properties were analyzed. For native flour, SS treatment altered the starch molecular structure and behavior slightly. While for moistened flour, crystalline degree, gelatinization enthalpy, amylose leaching (AML) and falling number significantly decreased, but thermal transition temperatures increased with the rise of treating severity. Clumping of starch granules, aggregation of proteins and formation of amylose-lipid complexes occurred in both native and moistened flours. Broader pasting temperature ranges and higher viscosities were found on SS-modified flours. Additionally, SS treatment on moistened flours increased resistant and slowly digestible starch contents. In general, SS treatment induced changes in starch molecular structure and reactions among flour components leading to more stable structures, thus affecting their pasting behavior, thermal properties and in vitro digestion.     

Effect of high-pressure treatment on rheological,thermal and structural changes in Basmati rice flour slurry

Rheological, thermal and structural changes in high pressure (HP) treated Basmati rice flour dispersions were studied as function of pressure level (350–650 MPa), slurry concentration (with 1:5, 1:3 and 1:2 flour-to-water ratios) and holding time (7.5–15 min). Rice flour dispersions exhibited a gradual liquid–solid gel transformation as they gelatinized and/or denatured and behaved as viscoelastic fluid following HP treatment. Mechanical strength (G′) of pressurized gel increased with applied pressure and rice concentration. Differential scanning calorimeter (DSC) thermograms of rice slurry measured after pressure treatment indicated a reduction in peak enthalpy in proportion with the extent of gelatinization and/or denaturation of starch and proteins. Pressure-treated rice samples had a progressively lower gelatinization temperature. A 15 min pressure treatment at 550 MPa was found sufficient to complete gelatinization of protein free isolated rice starch while the slurry required 650 MPa. The presence of proteins might have been responsible for the slower starch gelatinization in the rice slurry during pressure treatment. The sodium dodecyl sulfate polyacrylamide gel electrophoresis (SDS-PAGE) and Fourier-transform infrared (FTIR) spectroscopy results indicated some minor changes in protein subunits and secondary structure of rice protein. This study has provided complementary information on pressure-induced changes in physical (thermal stability, overall structure) and molecular level (secondary structure) of rice protein.