Combined effect of autoclaving‐cooling and cross‐linking treatments of normal corn starch on the resistant starch formation and physicochemical properties

Normal corn starch (NCS) was treated by both autoclaving‐cooling and cross‐linking to produce resistant starch (RS). The RS yield, crystalline structure, as well as other physicochemical properties of the modified starch were investigated. The yield of RS was 12.2% by four autoclaving‐cooling cycles, and it could be further increased up to 31.0% by the subsequent cross‐linking using sodium trimetaphosphate/sodium tripolyphosphate. The scanning electron microscopy images clearly illustrated that the granular structure of native starch was disrupted and a continuous network with irregular shape was formed after autoclaving‐cooling cycles. The subsequent chemical cross‐linking appeared to make the network structure more compact and dense. X‐ray diffraction patterns showed that B‐ and V‐types coexisted in all the modified corn starches, and all these modified starches exhibited very low viscosity which remained almost constant regardless of temperature changes.     

Effect of heat-moisture treatment on the formation and physicochemical properties of resistant starch from mung bean (Phaseolus radiatus) starch

Mung bean starch was subjected to a range of heat-moisture treatments (HMT) based on different moisture contents (15%, 20%, 25%, 30%, and 35%) all heated at 120 °C for 12 h. The impact on the yields of resistant starch (RS), and the microstructure, physicochemical and functional properties of RS was investigated. Compared to raw starch, the RS content of HMT starch increased significantly, with the starch treated at 20% moisture having the highest RS content. After HMT, birefringence remained at the periphery of the granules and was absent at the center of some granules. The shape and integrity of HMT starch granules did not change but concavity was observed under scanning electronic microscopy. Apparent amylose contents of HMT starch increased and the HMT starch was dominated by high molecular weight fraction. Both the native and HMT starches showed A-type X-ray diffraction pattern. Relative crystallinity increased after HMT. The gelatinization temperatures (To, Tp, and Tc), gelatinization temperature range (Tc–To) and enthalpies of gelatinization (ΔH) increased significantly in HMT starch compared to native starch. The solubility increased but swelling power decreased in HMT starches. This study clearly shows that the HMT exhibited thermal stability and resistance to enzymatic hydrolysis owing to stronger interactions of starch chains in granule.     

Production and physicochemical properties of resistant starch from hydrolysed wrinkled pea starch

The content and physicochemical properties of resistant starches (RS) from wrinkled pea starch obtained by different molecular mass reduction processes were evaluated. Native and gelatinised starches were submitted to acid hydrolysis (2 m HCl for 2.5 h) or enzymic hydrolysis (pullulanase, 40 U g^?1 for 10 h), followed by hydrothermal treatment (autoclaving at 121 °C for 30 min), refrigeration (4 °C for 24 h) and lyophilisation. Native starch showed RS and total dietary fibre contents of 39.8% and 14.3%, respectively, while processed ones showed values from 38.5% to 54.6% and from 22.9% to 37.1%, respectively. From these, the highest contents were among acid‐modified starches. Processed starches showed endotherms between 144 and 166 °C, owing to the amylose retrogradation. Native and processed starches showed low viscosity, which is inversely proportional to the RS concentration in samples. The heat treatment promoted an increase in the water absorption index. The pea starch is a good source for obtaining resistant starch by acid hydrolysis.     

Structural and physicochemical properties of resistant starch from Chinese chestnut (Castanea mollissima) prepared by autoclaving treatment and pullulanase hydrolysis

The purpose of this study was to evaluate the properties of resistant starch (RS) from Chinese chestnut (Castanea mollissima), which was prepared by autoclaving treatment and pullulanase hydrolysis. Scanning electron microscopy (SEM) revealed that the chestnut resistant starch (CRS) granules had a cohesive structure, an irregular shape, and diameters ranging from 6.0 to 7.2 µm. The enzymatic and retrogradation processes increased the yield of RS, and also decreased its swelling power, water solubility, and viscosity. An increase in transparency was also observed. The percent syneresis of the two starches increased steadily over time. X‐ray diffraction (XRD) analyses revealed that autoclaving and pullulanase hydrolysis converted C‐type native starch into a B‐type pattern and increased the crystallinity. In addition, differential scanning calorimetry (DSC) results indicated a reduction in gelatinization temperature and enthalpy compared with native starch. The thermal properties of RS increased due to the retrogradation and recrystallization (p < .05).

Practical applications

Chinese chestnut (Castanea mollissima) is an important nut crop with high nutrition and planted in China widely. High water content in fresh chestnut leads to mildew attack easily, which will affect the chestnut market value and trade business. Therefore, it has great significance and practical demand to develop the deep processing technology and diversify its products. The resistant starch has been implemented as an ingredient for its resistant digestion properties for making flour food and functional food. However, the research and application of resistant starch from Chinese chestnut (Castanea mollissima) has been rarely seen. This study investigated the structural and physicochemical properties of chestnut resistant starch and provided a reference for the application of chestnut resistant starch in the food processing industries. For example, an increase in transparency and syneresis suggested chestnut resistant starch could be potentially used as a functional ingredient in jelly, beverages, and other food products, but not be possible for use in the frozen food industry.     

Physicochemical and structural characteristics of cross‐linked banana starch using three cross‐linking reagents

Banana starch was cross‐linked using different cross‐linking reagents, phosphoryl chloride (POCl₃), sodium trimetaphosphate (STMP), and epichlorohydrin (ECH), under alkaline conditions. The reaction conditions were selected to produce similar pasting profiles. The effects of the different cross‐linking reagents on the physicochemical and structural characteristics of cross‐linked starches were evaluated. The microscopy study did not show difference on the surface of the granules. Slight decrease in the peak temperature and enthalpy were found in the cross‐linked banana starch. The chemical groups introduced in the starch molecules by the diverse reagents promoted the re‐association of starch chains during storage. The rheological analysis of all starch dispersion at 10% (flow curves) showed a non‐Newtonian shear‐thinning; pastes obtained were time‐independent, suggesting an important contribution of the continuous phase. Structural study showed that the cross‐linked STMP‐starch had the lowest level of amylose and the ratio short/long amylopectin chains. The three reagents used for cross‐linking presented different action mode on starch granule and its components.     

Quantification of Resistant Starch in Several Starch Sources Treated Thermally

The purpose of the research was to determine the effect of heat-moisture treatment at different phases and temperatures on resistance starch (RS) level on native starches samples of several botanical sources and to evaluate the thermal stability of different granules. Samples of potato, cassava, wheat, and corn starches were moisturized up to 30% wet basis and then treated in a convection oven at 80, 100, and 120°C during 40 and 60 minutes. RS was determined gravimetrically by a modification of Method 991.43 of the AOAC for the determination of total dietary fibre. All samples were submitted to different thermal analysis in a range from 40 to 180°C at 10°C/min. Overall, in the treated samples an increase of RS was observed, being the corn starch sample treated at 120°C and 60 minutes – the one that presented the highest content of RS (4.2%). Other treated samples showed a decrease in the gelatinization enthalpies with the presence of granular fusion, indicating internal re-arrangement, an increase in the gelatinization temperature and the thermo stability below 95°C.     

Effect of acid‐ethanol treatment followed by ball milling on structural and physicochemical characteristics of cassava starch

Structural and physicochemical characteristics of cassava starch treated with 0.36% HCl in anhydrous ethanol during 1 and 12 h at 30, 40, and 50°C followed by ball milling for 1 h were analyzed. Average yield of acid‐ethanol starches reached 98% independent of the treatment conditions. Solubility of acid‐ethanol starches increased with reaction temperature and time, but it did not change after ball milling. Granule average size reduced with chemical treatment from 25.2 to 20.0 µm after 12 h at 50°C. Ball milling decreased the granule average diameter of the native starch and those chemically treated at 30°C/1 h or 40°C/1 h, but it did not alter the starches treated for 12 h, independent of temperature. From scanning electron microscopy (SEM), starch granules presented round shape and after modification at 50°C/12 h, before and after ball milling, showed a rough and exfoliated surface. Some granules were deformed, suggesting partial gelatinization that was more intense after milling. Starch crystallinity increased as temperature and time of chemical treatment were increased, while amylose content, intrinsic, and pasting viscosities decreased. Gelatinization temperatures increased for all chemical starches. The findings can be related to the preferential destruction of amorphous areas in the granules, which are composed of amylose and amylopectin. After ball milling, the starch crystallinity decreased, amylose content, intrinsic, and pasting viscosities kept unchanged and gelatinization temperatures and enthalpy reduced. Ball milling on native and chemical starches caused the increase of amorphous areas with consequent weakening and decreasing of crystalline areas by breaking of hydrogen bonds within the granules.     

Effect of storage on resistant starch content and in vitro starch digestibility of some pressure‐cooked cereals and legumes commonly used in India

Resistant starch (RS) is that fraction of starch, which escapes enzymic hydrolysis in the small intestine and passes in the colon. Effect of storage time (12 and 24 h) and temperature (4 °C and 25 °C) was studied on RS content of the pressure‐cooked cereal and legume grains/seeds and their flours. RS content was observed to increase in the stored cereals and legumes, with more enhanced increase in the flour samples stored at refrigeration temperature for longer duration (41.4% in wheat flour and 85.4% in pea flour). Significant positive correlations were observed between RS content (4 °C, 24 h) and amylose (y = 0.388 × –5.948, r = 0.840, P ≤ 0.05, n = 7) as well as between % increase in insoluble dietary fibre content (4 °⁰C, 24 h) and amylose (y = 2.257 × –27.724, r = 0.971, P ≤ 0.05, n = 7). Reduced in vitro starch digestibility of the cooked/stored samples (4 °C, 24 h) was observed when compared to freshly cooked samples.     

Structural and physicochemical characterization of RS prepared using hydrolysis and heat treatments of chickpea starch

The aim of this study was to evaluate the production and the structural and physicochemical properties of RS obtained by molecular mass reduction (enzyme or acid) and hydrothermal treatment of chickpea starch. Native and gelatinized starch were submitted to acid (2 M HCl for 2.5 h) or enzymatic hydrolysis (pullulanase, 40 U/g per 10 h), autoclaved (121°C/30 min), stored under refrigeration (4°C/24 h), and lyophilized. The hydrolysis of starch increased the RS content from 16% to values between 20 and 32%, and the enzymatic treatment of the gelatinized starch was the most efficient. RS showed an increase in water absorption and water solubility indexes due to hydrolytic and thermal process. The processes for obtaining RS changed the crystallinity pattern from C to B. Hydrolysis treatments caused an increase in relative crystallinity due to the greater retrogradation caused by the reduction in MW. RS obtained from hydrolysis showed a reduction in viscosity, indicating the rupture of molecules. The viscosity seemed to be inversely proportional to the RS content in the sample.     

Effect of single and dual hydrothermal treatments on the crystalline structure,thermal properties,and nutritional fractions of pea,lentil, and navy bean starches

Pea, lentil and navy bean starches were annealed at 50 °C (70% moisture) for 24 h and heat-moisture treated at 120 °C (30% moisture) for 24 h. These starches were also modified by a combination of annealing (ANN) and heat-moisture treatment (HMT). The impact of single and dual modifications (ANN–HMT and HMT–ANN) on the crystalline structure, thermal properties, and the amounts of rapidly digestible starch (RDS), slowly digestible starch (SDS), and resistant starch (RS) were investigated. Birefringence remained unchanged on ANN but decreased on HMT. Granular swelling and amylose leaching decreased on ANN and HMT. Relative crystallinity, gelatinization enthalpy, and short-range order on the granule surface increased on ANN but decreased on HMT. Gelatinization transition temperatures increased on ANN and HMT. Gelatinization temperature range decreased and increased on ANN and HMT, respectively. ANN and HMT increased SDS and decreased RS levels in all starches. However, RDS levels increased on ANN and HMT in pea and lentil starches but decreased in navy bean starch. In gelatinized starches, ANN and HMT decreased RDS level and increased SDS and RS levels. Changes to crystalline structure, thermal properties and amounts of RDS, SDS, and RS were modified further on ANN–HMT and HMT–ANN.     

Synthesis and evaluation of physicochemical properties of cross‐linked Phaseolus aconitifolius starch

Highly substituted moth bean starch (MBS) phosphate ester was synthesized using POCl₃ as cross‐linking reagent. Titrimetric and FT‐IR spectral analysis was used to characterize the substitution. The physicochemical properties of cross‐linked moth bean starch (CLMBS) were done by using X‐ray powder diffractometer (XRD), thermogravimetric analysis (TGA) and swelling study at various temperatures. The change in starch morphology was done using scanning electron micrograph (SEM), and found that it lost its crystallinity after cross‐linking. The results revealed that crystalline nature of native MBS was transformed into amorphous after cross‐linking. TGA report exhibited higher thermal stability, which make it suitable for various industrial applications. Swelling behavior showed high swelling at low temperatures (30 and 60°C) as compared to at high temperature (90°C).     

Improving gel formation of rice starch added with cross‐linked resistant starch prepared from rice starch

The gel formation properties of non‐waxy rice starch with cross‐linked resistant starch with phosphate (RS4, 10, 20, and 30% based on rice starch) prepared from three rice varieties with different amylose (AM) content were investigated to increase dietary fiber content, improve gel structure, and reduce the glycemic index of rice products. The AM contents of rice starches were 1.71% in Hanganchal1, 22.47% in Nampyeong, and 33.39% in Goamy. All RS4 showed A‐type crystallinity and their RS levels were 46.91, 54.54, and 66.01%, respectively. The initial pasting temperatures of RS4 added rice starches increased as RS4 contents increased, but peak and breakdown viscosities and enthalpy change (△H) reduced. The RS4 addition improved gel shape and texture properties including hardness, cohesiveness, and gumminess, except the 30% Goamy RS4 added gel. The 20% RS4 addition was appropriate to form rice starch gels. The network structure of RS4 added gel formed more regular and firmer than that of control, because RS4 granules were entrapped within the gel matrix like observed by light microscope and scanning electron microscopy. It is suggested that RS4 not only assist in forming a rigid network structure but also increasing a dietary fiber content.

     

Resistant starch prepared from high-amylose maize starch with citric acid hydrolysis and its simulated fermentation in vitro

Resistant starch (RS) was prepared from high-amylose maize starch through two autoclaving–cooling cycles and then acid hydrolysis of retrograded starch. Experimental results showed that hydrolysis of retrograded high-amylose maize starch with 0.1 mol L⁻¹ citric acid at room temperature for 12 h would increase RS yield to 39%. At simulated conditions of large intestine (anaerobic and 37 °C), the prepared RS product was fermented in culture by fresh feces extract from healthy adult or healthy infant to produce short chain fatty acids. Formic, acetic, propionic and butyric acid produced in culture were analyzed by GC with capillary column. The GC analysis results showed that as the increase of fermentation time and the addition level of RS in culture, the production of short chain fatty acids was increased. However, the production of short chain fatty acids (especially butyric acid) in culture fermented by healthy infant feces extract was much higher than that fermented by healthy adult feces extract. It suggested that the production of short chain fatty acids from RS in simulated intestinal conditions might be affected by the intestinal microflora.     

New starch preparations resistant to enzymatic digestion

BACKGROUND: New starch preparations were produced by thermolysis of potato starch in the presence of inorganic (hydrochloric) and organic (citric and tartaric) acids under controlled conditions. The starch preparations were physicochemically and structurally characterised and analysed for their resistance to enzymatic digestion in vitro. RESULTS: The content of resistant fraction in dextrin D1, obtained by heating starch acidified with hydrochloric and citric acids, determined by the AOAC 2001.03 and pancreatin‐gravimetric methods was similar (～200 g kg^?1). In the case of dextrin D3, obtained by heating starch acidified with hydrochloric and tartaric acids, the result of determination by the pancreatin‐gravimetric method was almost four times higher than that obtained with the AOAC 2001.03 method. The enzymatic tests revealed that dextrin D3 obtained with excess tartaric acid can be classified as RS4, which can only be partially determined by enzymatic‐gravimetric methods. Tartaric acid at high concentration had a significantly stronger influence on starch hydrolysis than citric acid. This was confirmed by chromatographic analysis of dextrins and chemical investigation of the reducing power. CONCLUSION: The results confirmed the possibility of applying dextrins, prepared under specific conditions, as soluble dietary fibre. Copyright © 2011 Society of Chemical Industry     

Digestibility of common native starches with reference to starch granule size,shape and surface features towards guidelines for starch-containing food products

Influence of diverse botanical sources (wheat, maize, waxy maize, cassava, potato, rice or waxy rice) on in vitro native starch digestibility has been investigated. Physicochemical properties (chemical composition, particles size and shape, surface features) of starch granules were determined with a view to explaining digestibility differences between samples. Rapidly digestible starch (RDS), slowly digestible starch (SDS) and resistant starch (RS) contents were measured according to Englyst method. Potato starch was shown to be composed of large rounded granules having smooth surfaces, which explains its slow enzymatic breakdown. Potato starch displayed the highest RS (86%) content and the lowest RDS content (9.9%). Since RS positively influences health and SDS may result in cell, tissue and/or organ damages, potato starch is an ideal starch nutrient. Conversely, waxy rice starch was rich in amylopectin and displayed small diameters and angular shapes, which are both known to facilitate enzymatic starch hydrolysis. It exhibited a near-zero RS content (0.9%) and a high RDS fraction (60%). According to this study, potato starch exhibited the best nutrient profile, followed up in this order by cassava, waxy maize, wheat, maize and waxy rice starches.     

In vitro Digestibility of Cross‐Linked Starches – RS4

In vitro digestibility of cross‐linked starches (RS4 type), which were prepared from wheat, corn, rice, potato, and high‐amylose corn starches, was determined by Prosky AOAC and pancreatin gravimetric (P/G) methods. The RS levels of RS4 starches obtained by the AOAC method were higher than those by the P/G method. Pronase treatment before digestion with heat‐stable α‐amylase (AOAC method) gave similar RS levels as those by P/G method. The shapes of residues after digestion by the AOAC method were not different from untreated ones, but those after digestion by the P/G method showed irregular and fluffy forms. It was found that the P/G method provided more exhaustive digestion of RS4 starches than the AOAC method.     

超声波辅助酶解制备多孔淀粉的研究

以玉米淀粉为原料酶解制备多孔淀粉,在酶解前、中、后分别用超声波处理,以水解率和吸油率为指标,探讨了超声波频率、超声时间、淀粉乳浓度等因素对所得产品成孔情况的影响;同时,用扫描电镜对多孔淀粉颗粒的微观形态进行了分析。结果表明,在酶解中用超声波间歇处理效果最好。在超声功率50%、超声时间30 min、淀粉乳浓度70%的条件下,所得多孔淀粉的水解率和吸油率最高,成孔情况最好,其吸油率比普通多孔淀粉提高56%。电镜微观形态分析显示,多孔淀粉微孔的水解率和吸油率的变化与其孔径、孔深及数目的变化相吻合。     

不同物理方法处理对碎米中淀粉特性的影响

采用挤压、微波、超声波三种物理方法对水分含量18%的碎米淀粉进行处理,研究分析碎米淀粉经物理方法处理前后的理化性质和结构变化。结果表明,碎米淀粉经微波和超声处理后酶解力增加,糊化黏度下降,而溶解度、膨胀力、糊化温度和直链淀粉含量变化不显著;两种淀粉颗粒表面棱角减少,淀粉颗粒晶型基本没有发生变化,淀粉结晶区降低。挤压后的碎米淀粉变化较大,颗粒形状为片状,凝沉性强,1.0 h后体积仅为3 mL,糊化温度明显降低至55.0 ℃,直链淀粉含量增长为30.75%,溶解度强,为0.59%,酶解力达到45%,X-射线主要衍射峰的强度降低。     

Swelling Characteristics of Native and Chemically Modified Wheat Starches as a Function of Heating Temperature and Time

The effects of hydroxypropylation (molar substitution, MS 0.05, 0.12, and 0.18) and cross‐linking (0.03%, 0.1%, and 0.2%) on swelling properties of wheat starch granules at several temperatures and heating times were investigated by laser diffraction particle size analysis. Starch samples were dispersed in water at temperatures ranging from 30 to 90°C, for 1 to 360 min. All starch granules exhibited distinct bimodal size distributions: small B‐granules with mean diameter of 2.3 μm and large A‐granules with mean diameter of 20.4 μm. As temperature increased, the B‐granules swelled more than A‐granules. Swelling of A‐granules sharply increased at 60°C. Swelling was more pronounced with increasing molar substitution of hydroxypropyl groups, while increased swelling was not observed in cross‐linked starches. The dependence of swelling capacity on heating time was different at 60 and 80°C as well as amongst modified starches. As heating time was prolonged, mean granule sizes for native, control, and hydroxypropylated starches at 80°C decreased after reaching maximum size due to loss of granule integrity, while those at 60°C showed no significant change.     

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.