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The effect of extracts from four types of tea made from Camelia sinensis (green, white, black, and oolong) on in vitro amylolysis of gelatinized starch and the underlying mechanisms were studied. Of the four extracts, black tea extract (BTE) gave the strongest inhibition of starch digestion and on α-amylase activity. Fluorescence quenching and surface plasmon resonance (SPR) showed compounds in BTE bound to α-amylase more strongly than those in the green, white, and oolong tea extracts. Individual testing of five phenolic compounds abundant in tea extracts showed that theaflavins had a greater inhibitory effect than catechins on α-amylase. SPR showed that theaflavins had much lower equilibrium dissociation constants and therefore bound more tightly to α-amylase than catechins. We conclude that BTE had a stronger inhibitory effect on in vitro enzymatic starch digestion than the other tea extracts, mainly due to the higher content of theaflavins causing stronger inhibition of α-amylase.

Granular starch octenyl succinic anhydride (OSA) esters have most often been prepared in aqueous media, resulting in low reaction efficiencies and degree of substitution. In this study, granular ma...

Structure-function relationships of starch isolated from eight cultivars of foxtail millets grown in China were investigated. The starch granules were polygonal with diameters between 5 μm and 10 μm. The amylose content ranged from 16.8% to 26.8%, and the relative crystallinity and the full width at half maximum (FWHM) of the Raman band at 480 cm−1 varying between 33.2% and 36.4% and 15.72 to 15.91, respectively. There were only small differences in amylopectin chain length distribution of the eight foxtail millet starches. Significant differences were noted in swelling power, gelatinization, pasting, gel textural properties of starches, but not in vitro enzymic digestibility. Correlation analysis results showed that amylose content and chain length distribution of amylopectin were more important determinants of functional properties of starch than the structural order of the starch granules.

Physical interactions often occur between major food components during food processing. These interactions may involve starch, lipids, and proteins forming V-type starch-lipid complexes or ternary starch-lipid-protein complexes of larger molecular size and greater structural order. Complexes between starch and lipids have been the subject of intensive research for over half a century, whereas the study of starch-lipid-protein complexes is a relatively new field with only a limited amount of knowledge being gained so far. The formation of these complexes can significantly affect the functional and nutritional properties of finished food products in terms of flavor, texture, shelf life, and digestibility. This article provides a comprehensive review of starch-lipid and starch-lipid-protein complexes, including their classification, factors affecting their formation and structure, and preparative and analytical methods. The review also considers how complexes affect the physicochemical and functional properties of starch, including digestibility, and potential applications in the food industry.

Starch is a major part of the human diet and an important material for industrial utilization. The structure of starch granules is the subject of intensive research because it determines functionality, and hence suitability for specific applications. Starch granules are made up of a hierarchy of complex structural elements, from lamellae and amorphous regions to blocklets, growth rings and granules, which increase in scale from nanometers to microns. The complexity of these native structures changes with the processing of starch-rich ingredients into foods and other products. This review aims to provide a comprehensive review of analytical methods developed to characterize structure of starch granules, and their applications in analyzing the changes in starch structure as a result of processing, with particular consideration of the poorly understood short-range ordered structures in amorphous regions of granules.

The present study investigated the effect of octenyl succinic anhydride (OSA) modification of starch on the formation of starch-lipid complexes. The complexing index (CI) showed that native maize starch (NMS) formed more complexes with monopalmityl glycerol (MPG) than with palmitic acid (PA), whereas dipalmityl glycerol (DPG) was not effective in forming complexes with NMS. After OSA modification, the complexation between OSA-starch and lipids was greatly enhanced, especially for PA and DPG, and the CI values increased from 79.6 to 93.3% for OSA-starch-PA and from 80.3 to 93.2% for OSA-starch-DPG complexes with increasing DS of OSA-starch. Structural analyses showed that OSA-starch-lipid complexes had higher degrees of long- and short-range molecular orders than the corresponding NMS-lipid complexes. This study showed for the first time that DPG can form complexes with OSA-starch, which was attributed to the increased dispersion of DPG in water by the emulsifying ability of OSA-starch. The finding is of great significance for a better understanding of the formation of starch-lipid complexes.

The effect of the anionic structure of ionic liquids (ILs) and water/IL ratio on the dissolution behavior of maize starch at room temperature (22-23 °C) was investigated. The ILs used were 1-ethyl-3-methylimidazolium chloride ([C2mim][Cl]), 1-ethyl-3-methylimidazolium formate ([C2mim][HCOO]), and 1-ethyl-3-methylimidazolium acetate ([C2mim][CH3COO]). The structural analysis indicated that the long- and short-range molecular order in the starch after treatment with water/[C2mim][Cl] and water/[C2mim][HCOO] mixtures decreased with the decreasing water/IL ratio from 10:1 to 2:1 and was completely disrupted at the 2:1 ratio. However, the ordered structure of starch was disrupted completely in the water/[C2mim][CH3COO] ratio of 5:1. The disruption extent of starch structures followed the order: [C2mim][CH3COO] > [C2mim][HCOO] > [C2mim][Cl] at water/IL ratios of 10:1 and 5:1, but the opposite was observed at lower water/IL ratio (2:1). Our results clearly showed that both the nature of the anion and water/IL ratio affected the dissolution behavior of maize starch. The hydrogen bonding capacity of IL anions and viscosity of water/IL mixtures were proposed to play the key roles in the structural disruption of starch. These findings would be of great importance for rationally designing "green and sustainable" processes for the utilization of promising natural biopolymers.

Potato starch was pre-treated with CaCl2 solutions prior to modification with octenyl succinic anhydride (OSA). Starch pre-treated with 1.0 M CaCl2 showed higher degree of substitution (DS) and reaction efficiency (RE) on OSA modification, whereas pre-treatment with CaCl2 solutions at 0.05 M, 0.1 M and 0.5 M had no effect on DS and RE. CaCl2 pre-treatment decreased the swelling power, paste clarity, peak viscosity (PV), breakdown (BD) and some textural parameters of potato starch, with the effects being greater at higher concentrations of CaCl2. Pre-treatment with 1.0 M CaCl2 caused a small disruption to starch crystallinity and granule morphology. OSA modification significantly decreased the textural parameters, PV, BD, relative crystallinity, swelling power, gelatinization temperatures and enthalpy of potato starch, but it increased the paste clarity and emulsifying activity. OSA-1.0 M-starch showed improved functional properties over OSA-starch, indicating that CaCl2 pre-treatment provides advantages for improving the functional characters of succinylated starch.

The purpose of this study was to understand the dissolution behavior of maize and potato starches in 1-ethyl-3-methylimidazolium acetate ([Emim][OAc]):water mixtures at room temperature. With an increasing ratio of ionic liquid (IL):water, the long- and short-range ordered structures and granule morphology of both starches were disrupted progressively. The multiscale structure of maize starch was disrupted completely after treatment with the [Emim][OAc]:water mixture of 6:4, indicating good dissolution performance of this mixture for maize starch. This mixture seemed to provide a balance between the viscosity of the solvent and availability of ions to disrupt starch H-bonds. The different dissolution behaviors of maize and potato starches in [Emim][OAc]:water mixtures were attributed to structural differences of the granule surfaces. Our results showed that the dissolution behavior of starches was affected by both starch sources and properties of [Emim][OAc]:water mixtures, which may provide guidance for the development of green technology for processing of biopolymers with low energy consumption.

The dissolution behavior of maize starch in water:ionic liquid (IL) mixtures at ambient temperature (22–23 °C) was studied. The ionic liquids used were 1-butyl-3-methylimidazolium chloride ([C4 mim][Cl]), 1-propyl-3-methylimidazolium chloride ([C3 mim][Cl]), and 1-ethyl-3-methylimidazolium chloride ([C2 mim][Cl]). Structural analyses indicated that long- and short-range molecular order in the starch decreased with decreasing water:IL ratio. At water:IL ratios of 10:1 and 5:1, the extent of disruption of starch structure followed the order [C4 mim][Cl] > [C3 mim][Cl] > [C2 mim][Cl]. At lower water:IL ratio (2:1), the complete disruption of starch granule morphology and ordered structures in water:[C3 mim][Cl] and water:[C2 mim][Cl] mixtures indicated these mixtures were more effective in dissolving starch than water:[C4 mim]Cl mixture. Results from rheological, FTIR, and 1H NMR analyses of water:IL mixtures showed that as water:IL ratio decreased, the viscosity of solutions increased, the interaction betwe...

The objective of this research was to compare the in vitro fermentability of three resistant starches (RS2, RS3, and RS5). Structural analyses showed that there were small changes in the long- and short-range ordered structure of three RSs after fermentation by human gut microbiota. The fermentation of RSs by gut microbiota produced large amounts of short-chain fatty acids, with RS5 producing more butyric acid and RS3 producing more lactic acid. RS3 and RS5 decreased the pH of the fermentation culture to a greater extent compared with RS2. Moreover, RS5 increased significantly the relative abundance of Bifidobacterium, Dialister, Collinsella, Romboutsia, and Megamonas. The results suggested that the form of RS was the main factor affecting the physiological function of RS and that RS5, as a recently recognized form of resistant starch, could be a better functional ingredient to improve health compared with RS2 and RS3.

In this study, the effects of debranching on the structure and properties of the starch-lauric acid (LA)-β-lactoglobulin (βLG) complex were studied. Gel permeation chromatography and high-performance anion-exchange chromatography showed that debranching of amylopectin generated short linear chains, which increased in proportions with debranching time. Analyses from differential scanning calorimetry, laser confocal micro-Raman spectroscopy, and X-ray diffraction showed that debranching promoted the formation of starch-LA and starch-LA-βLG complexes, as characterized by the increased enthalpy changes and crystallinity and decreased full width at half maximum of the band at 480 cm-1. Debranching treatment for 6 and 18 h promoted complexation between starch and LA, while extensive debranching was unfavorable for the formation of starch-LA complexes. Similar results were also observed for the starch-LA-βLG complexes. Starch-LA-βLG complexes had more type II and less type I crystallites than starch-LA complexes. From this study, we conclude that debranching of starch favors the formation of starch-LA and starch-LA-βLG complexes, with more type II crystallites formed in starch-LA-βLG complexes.

The effect of interactions between beta-lactoglobulin (βLG) and lauric acid (LA) on the formation of ternary maize starch-LA-protein complexes was investigated. Analysis of the secondary structure of βLG by FTIR and changes in fluorescence λmax and intensity indicated that βLG and LA interacted during heating and cooling in a Rapid Visco Analyser (RVA). Results from RVA, DSC and Raman spectroscopy analyses showed that increasing the concentration of βLG from 25 to 200 mg increased the amount of ternary starch-LA-βLG complexes formed. There was little difference in the amounts of the ternary complexes formed when the amount of βLG was 25–150 mg, but a greater amount of starch-LA-βLG complexes was formed when 200 mg of βLG was pre-mixed with LA. From this study, we concluded that prior interaction between βLG and LA had no significant effect on the formation of ternary starch-LA-βLG complexes.

The effects of cooking and storage on the structure and in vitro enzymatic digestibility of complexes formed between fatty acids and debranched high-amylose starch (DHA7-FA) were investigated for the first time. Cooking greatly decreased the crystallinities of DHA7-lauric acid (LA) and DHA7-myristic acid (MA) complexes but had little effect on the crystallinities of DHA7-palmitic acid (PA) and DHA7-stearic acid (SA) complexes. Cooking increased the enthalpy-change (Δ H) values and short-range molecular orders of DHA7-FA complexes. Cooking decreased the in vitro enzymatic digestibility of DHA7-FA complexes, with the extent of the effect decreasing with increasing fatty acid chain length. Holding the samples at 4 °C for 24 h after cooking did not greatly affect the long- and short-range molecular orders nor the in vitro enzymatic digestibility of DHA7-FA complexes. From this study, we conclude that cooking disrupted the long-range crystalline structures of DHA7-LA and DHA7-MA complexes but enhanced the short-range molecular orders of all of the DHA7-FA complexes. The latter effect accounted mainly for the reduced in vitro enzymatic digestibility of DHA7-FA complexes.

This study aimed to understand mechanisms of starch gelatinization during heating of wheat (Triticum aestivum L.) flour, and its effects on in vitro starch amylolysis of cooked wheat flour. At water content of 20%, cooking did not disrupt greatly the crystalline structures of starch in wheat flour. Considerable disruption of ordered structures of starch occurred with cooking at a water content of 30%, and starch was fully gelatinized at a water content of 40%. The transition of the X-ray diffraction pattern from A to V types with increasing water content suggested the formation of starch-lipid complexes during cooking of flour. Typical starch pasting profiles of cooked wheat flour were observed at water contents of 40 and 50%, whereas longer cooking time decreased the pasting viscosities of the flour. Cooking the flour for only 5 min with 20% water greatly increased the rate and extent of in vitro enzymatic digestion of starch, which were not increased further by longer cooking or higher water content. From this study, we conclude that the progression of starch gelatinization during cooking was not greatly affected by non-starch components in wheat flour, and that some structural order in amorphous regions of starch contributed to the development of pasting viscosities.

Dental calculus is now widely used to recover information on items ingested in the past. It is particularly valuable in the earlier Paleolithic, where recovered data may represent the only evidence for plant use. Several recovery methods are used and each one produces different results. Biomolecular markers and genetic material recovered from dental calculus is providing new data on identifiable dietary and medicinal items and human microbial communities. The recovery of microfossils, in particular, starch granules, has triggered a new awareness of the role of plants in the diet throughout the Paleolithic. However, the minute amount of material recovered has little relationship with food eaten during a person's life, while salivary amylase breaks down cooked starch. Therefore, broader dietary interpretations and detection of cooked food are problematic. The study of ancient dental calculus holds great potential to recover information about past lives, within realistic parameters.

The nature of phase transitions of waxy maize starch heated in mixtures of water and ionic liquid (IL) was elucidated using a variety of analytical methods. The transition from a single endotherm to an exotherm followed by an endotherm, and then to a single exotherm was observed with the increasing concentration of IL. The results showed that at To of DSC phase transition no structural disruption had occurred. Except for the water/IL ratios of 1.5:1 and 1:1, there was considerable structural disruption of starch samples that were preheated to Tp or Tp2 of gelatinization transition. No residual structural order was observed at Tc of the gelatinization transition. An exothermic transition at water:IL ratios of 3:1 and 2:1 was attributed to the interaction of ionic liquid and amorphous regions in starch. The molecular disassembly of starch granules during gelatinization in different water:IL mixtures proceeded to completion at different rates.

The effect of water content and particle size on physicochemical properties and in vitro starch digestibility of three milled wheat fractions was investigated. The crystallinity of three milled fractions of particle sizes

The effects of chain length and degree of unsaturation of fatty acids (FAs) on structure and in vitro digestibility of starch-protein-FA complexes were investigated in model systems. Studies with the rapid visco analyzer (RVA) showed that the formation of ternary complex resulted in higher viscosities than those of binary complex during the cooling and holding stages. The results of differential scanning calorimetry (DSC), Raman, and X-ray diffraction (XRD) showed that the structural differences for ternary complexes were much less than those for binary complexes. Starch-protein-FA complexes presented lower in vitro enzymatic digestibility compared with starch-FAs complexes. We conclude that shorter chain and lower unsaturation FAs favor the formation of ternary complexes but decrease the thermal stability of these complexes. FAs had a smaller effect on the ordered structures of ternary complexes than on those of binary complexes and little effect on enzymatic digestibility of both binary and ternary complexes.

There is evidence that moderate coffee consumption is beneficial in the prevention of type 2 diabetes, however, the underlying mechanism is not understood. In this study, the effects of an extract of ground coffee on the in vitro enzymatic digestion of starch were investigated. The coffee extract decreased the rate and extent of starch digestion, with kinetic analysis showing that the extract reduced the binding affinity of the enzymes for the substrate and their catalytic turnover. Fluorescence quenching indicated that the coffee extract formed complexes with the digestive enzymes through a static quenching mechanism. Ultraviolet absorption and circular dichroism spectra of the digestive enzymes confirmed that the coffee extract decreased the proportion of β-sheet structures in the enzymes. Therefore, we conclude that compounds in the soluble coffee extract can interact with porcine pancreatic amylase and amyloglucosidase causing inhibition of the enzymes and decreasing in vitro starch digestion.

This study aimed to reveal the mechanism of formation of complexes between native maize starch (NMS) and different types of lipids, namely palmitic acid (PA), monopalmitate glycerol (MPG), dipalmitate glycerol (DPG), and tripalmitate glycerol (TPG). The complexing index followed the order of MPG (96.3%) > PA (41.8%) > TPG (8.3%) > DPG (1.1%), indicating that MPG formed more complexes with NMS than PA, and that few complexes were formed between NMS and DPG and TPG. The NMS-PA complex presented higher thermal transition temperatures and lower enthalpy change than the NMS-MPG complex, indicating that although MPG formed more starch complexes, they had less stable crystalline structures than the complex between NMS and PA. X-ray diffraction (XRD) and Raman spectroscopy showed that both MPG and PA formed V-type crystalline structures with NMS, and confirmed that no complexes were formed between NMS and DPG and TPG. We conclude that the monoglyceride formed more starch-lipid complex with maize starch than PA, but that the monoglyceride complex had a less stable structure than that formed with PA. The di- and triglycerides did not form complexes with maize starch.

This study evaluated the effects of different cooking methods on in vitro starch digestibility of three rice varieties. Results from differential scanning calorimetry and X-ray diffraction of cooked rice flours showed that rice starch was completely gelatinized after cooking. The overall paste viscosities of cooked indica hybrid flour (IHF) and japonica flour (JF) were lower than those of their corresponding raw flours. However, cooked waxy flour (WF) showed much higher paste viscosities than raw flours, especially the viscosity at the start of RVA testing. Cooking increased greatly the rate and extent of starch digestion of IHF and JF, but had a small effect on WF. There were small differences in rate and extent of starch digestion of rice after cooking under various conditions. Cooking methods were found to have little effect on in vitro starch digestibility of rice. Viscosity of the gelatinized waxy starch matrix affected in vitro starch digestibility. This study enables us to gain a better understanding of cooking effects on in vitro digestibility of starch in rice flour.

The effects of starch damage and yeast fermentation on the formation of acrylamide in wheat bread were studied. Four wheat cultivars were milled separately by three laboratory mills to obtain wheat flours with damaged starch content ranging from 1.7 to 6.6%. Reducing sugar contents increased with increasing damaged starch content in flour. Yeast fermentation decreased greatly the content of asparagine by 40–60% in the dough, but increased substantially the content of reducing sugar. Compared with the unleavened bread, dough fermentation significantly decreased the content of acrylamide in leavened bread. The content of acrylamide in bread increased with increasing damaged starch content in wheat flours from the same cultivar. This study clearly showed that damaged starch content in wheat flour and dough fermentation are two major determinants of the formation of acrylamide in bread. The mitigation of acrylamide formation in bread can be achieved by reducing damaged starch in flour and by fermentation of the dough.

This chapter considers the digestibility of starch in relation to its nutritional qualities and influences on human health. Rapidly digested starch (RDS) is associated with poor postprandial glycaemic and insulinemic control. Excessive dietary exposure over the long term increases the risks for obesity and diet-related illnesses. Slowly digested starch (SDS) moderates these postprandial responses and has a key role in producing satiety and limiting food intake. Starch that is not digested in the upper human gut is a good source of fermentable food for the gut microbiota, which are now recognised as having an essential role in the health of the host.

This chapter presents a brief overview of key discoveries that led to our current knowledge of starch. Due to the variability of natural starch, and the significance of this biopolymer to humans in foods and industrial applications, much attention has been given to gaining an understanding of its structure and functional properties. Early uses for starch are considered, as are developments in the growth of the starch industries, and how the molecular structure of starch was revealed.

The interaction of polyphenolic catechins from Camellia sinensis tea with α-amylase, and the effects of the interactions on the kinetics of starch amylolysis, were investigated. Binding studies using surface plasmon resonance (SPR) and enzyme kinetic analysis indicated that the in vitro digestibility of gelatinized wheat starch was decreased by the addition of catechins present in tea. Tea catechins decreased enzyme activity by reducing the maximum velocity (Vmax) of the α-amylase, but had little effect on the Michaelis-Menten constant (Km). Binding studies by SPR showed that the structure of the catechins influenced their affinity for α-amylase. Pearson correlation analysis showed that the decreased digestibility of starch in the presence of catechins was due to their binding of α-amylase interaction inhibiting the catalytic effectiveness of the enzyme. From this study, we concluded that the faster and stronger the binding of catechins and α-amylase, the greater reduction of starch digestion is.

Interspecific germplasm from wild species of Oryza will be increasingly applied to breeding programs over the coming decades. However, the concurrent impact of rising atmospheric CO2 concentrations (atm-CO2) on grain properties is unknown. Wild accessions of Australian native rice species (Oryza australiensis and O. meridionalis) and the local cultivar (O. sativa cv. Doongara) were grown to maturity in glasshouses at ambient (400 ppm; aCO2) and elevated (700 ppm; eCO2) atm-CO2 and physicochemical properties of the grains were compared. Seed length (Sl), seed width (Sw) and 1000-seed weight (TSW) were higher at eCO2 than aCO2, while nitrogen content (N) and apparent amylose content (AC) were not significantly changed, irrespective of genotype. Rapid viscosity analyser (RVA) profiles revealed increased peak viscosity (PV) for rice under eCO2, indicating differences in starch gelatinization. However, final viscosity (FV) increased in the wild rices in eCO2, whereas it decreased in Doongara. Increases in PV were accompanied by lower estimates of protein contents (PC) at eCO2 in all species. When AgNO3 was excluded from the RVA, it became apparent that its presence had enhanced the effects of eCO2 on flour pasting properties through inhibition of α-amylase activity of the flour. Our results suggest that grain morphology and pasting properties are differently affected by eCO2 in the wild rices compared with cultivated rice. These data will inform the breeding criteria for rice grain properties and inform the introgression of wild germplasm.

In this study, potato, lotus seed and wheat starch samples with different degree of gelatinization (DG) were prepared and their in vitro digestibility at low α-amylase activity evaluated by measuring the release of reducing sugar. The hydrolysis rate (k) and the final equilibrium concentration (C∞) of the three starches increased with increasing DG. Kinetic analyses showed that the Michaelis-Menten constant (Km) and the catalytic efficiency (kcat/Km) increased with increasing DG, indicative of the increasing affinity and catalytic efficiency of α-amylase with all three starch samples. Of the three starches, lotus seed starch showed a much greater increase in k and kcat/Km than potato and wheat starches as the DG of starch increased. From this study, we concluded that at low activity of α-amylase, DG is a major determinant for the binding affinity and catalytic efficiency of α-amylase to starch and in turn the digestion rate of starch.

The interactions of four starches-waxy maize starch (WMS), non-waxy maize starch (MS), potato starch (PS), wheat starch (WS)-with lauric acid (LA) and β-lactoglobulin (βLG) were investigated. Analysis of mixtures in the Rapid Visco Analyser (RVA) showed that the MS-LA and WS-LA systems presented a viscosity peak during the cooling and holding stages of the profile, PS-LA system showed only an increase in the final viscosity, whereas WMS-LA system displayed no obvious changes during the RVA cooling and holding stages. Structural analyses showed that wheat and maize starches formed more crystalline complexes with LA than potato starch, whereas no complexes were formed between WMS and LA. The addition of βLG increased the final viscosity of all starch-LA systems, with the most obvious increase observed for PS-LA systems. Structural analyses showed that the addition of βLG promoted the formation of starch-LA complexes, even for the WMS-LA system. From this study, it can be concluded that the nature of the starch affects the formation of starch-lipid complexes, and that these effects can be modified by βLG, which promotes the formation of starch-lipid complexes.

In this study, we elucidated the underlying mechanisms that are responsible for the rate-limiting step for wheat starch digestion. Wheat starch samples with a degree of gelatinization (DG) ranging from 0 to 100% were prepared. As DG increased, the ordered structures of the starch were disrupted increasingly. In contrast, almost all of the increase in the rate and extent of in vitro enzymatic digestion coincided with a DG of only 6% and a minor loss of structural order. As DG increased beyond 6%, digestibility of the starch increased only slightly. We propose that the access and binding of enzymes to starch is greatly increased with only a small DG, which is followed by the simultaneous hydrolysis of crystalline and amorphous areas in gelatinized starch. In vitro enzymatic digestibility of starch was determined predominantly by enzyme binding to starch rather than the ordered structures of starch.

An appropriate in vitro starch digestion model is necessary to comparatively evaluate the digestibility of starch samples and to help predict the in vivo glycemic responses of starchy foods. In the present study, the effect of trypsin and chymotrypsin on in vitro digestion of rice starch was studies for the first time. Inclusion of the trypsin and chymotrypsin in the digestion protocols, to more closely simulate intestinal digestion, increased the hydrolysis percentage of cooked rice and rice starch gels. The hydrolysis kinetics results showed that the digestion rate of cooked rice and starch gels was increased with the addition of trypsin and chymotrypsin in the simulated intestinal fluids. This study showed clearly that the addition of proteases during simulated intestinal digestion is necessary to evaluate accurately the in vitro digestibility of starch or starchy foods.

The aim of present study was to investigate the effect of pH on interactions between macro constituents of foods using wheat starch (WS), lauric acid (LA) and β-lactoglobulin (βLG) in a model system. Results from the Rapid Visco Analyzer (RVA) showed that viscosity peaks appeared during the cooling stage and that their intensity increased gradually from 105 to 5565 cP with increasing pH in the WS-LA binary system. With the WS-LA-βLG ternary system, the cooling viscosity peaks occurred throughout the pH range, and the change in intensity (from 1111 to 3688 cP) was not as evident as in binary systems. Results from differential scanning calorimetry (DSC), X-ray diffraction (XRD) and Raman spectroscopy showed that higher pH promoted the formation of both WS-LA binary and WS-LA-βLG ternary complexes, attributed to greater solubility of LA and higher leaching of amylose. The limited effect of pH variation on the formation of ternary complexes compared with binary complexes is proposed to be due to the pH buffering effect of βLG.

The aim of the present study was to investigate the mechanism of formation of maize starch (MS)-lipid complexes during pasting in the Rapid Visco Analyser. MS-lauric acid (LA) and MS-monomyristyl glycerol (MMG) samples with lipid concentrations of 0-5% were prepared and characterized. Complexing index (CI) and rheological analyses showed that the viscosity and gel strength of starch was highly correlated to the amount of starch-lipid complex that formed. An increase followed by a decrease in CI values, enthalpy change and structural order during pasting of MS-2% LA mixture indicated that starch-lipid complexes were mostly formed during the setback stage, and that the disruption of some complexes formed at higher lipid concentration occurred with ongoing cooling. This study revealed the mechanisms of formation of starch-lipid complexes during simulated food processing, and how such complexes affect the viscoelastic properties of starch pastes, which is of relevance to the texture of starchy foods.

This study presents a new method for characterizing short-range molecular order in amorphous starch using Raman spectroscopy and wide-angle X-ray diffraction (XRD). Amorphous wheat and potato starch samples with different degrees of short-range molecular order were prepared by heating starch:water mixtures ranging from 1:1 to 1:19 at 100 °C for 10 min. The XRD and 13C CP/MAS NMR spectroscopy analyses showed that all starch samples had lost their long-range crystallinity and from that perspective were considered to be gelatinized. The peak area and intensity of the Raman bands at 480, 1131 and 1080 cm−1 and the full width at half maximum (FWHM) of XRD peaks at 16.7 and 20.7° (2θ) were correlated strongly to the degree of short-range molecular order in amorphous starch. On the basis of these relationships, we propose a method to analyze the short-range molecular order in amorphous starch, and thereby better characterize its properties.

The aim of the present study was to investigate the interactions between maize starch (MS), β-lactoglobulin (βLG), and monoglycerides (MG) containing different fatty acids in a model system. Results from the Rapid Visco Analyzer (RVA) showed that MS-MG

In this study, the gelatinization behavior of wheat starch was investigated using starch-water mixtures that were heated under different conditions. Heating starch-water mixtures at 50 °C, a temperature below onset temperature (To) of starch gelatinization, resulted in disruption of long- and short-range ordered structure, as measured by differential scanning calorimetry, X-ray diffraction and laser confocal micro-Raman spectroscopy, and the extent of disruption was greater when starch was heated at higher water content. At low water content (23–44%), heating duration had little effect on gelatinization behavior of starch, whereas at higher water content (54–75%), longer duration of heating resulted in greater disruption of multiscale structure of starch. From this study, we concluded that the gelatinization endotherm of starch does not represent the complete gelatinization behavior, and starch gelatinization initiates earlier than To. Longer duration of heating caused a greater disruption of starch structure at high water content than at low water content.

This study aimed to investigate the effect of purple yam (Dioscorea alata L.) flour substitution for wheat flour on in vitro starch digestibility of wheat bread. The enzyme-resistant starch content increased from 34.9% for wheat flour bread to 41.3% for bread made with 70% wheat flour and 30% purple yam flour. Meanwhile, the content of rapidly digestible starch and slowly digestible starch decreased with the addition of purple yam flour in the bread. The results from differential scanning calorimetry, X-ray diffraction, polarized light and scanning electron microscopy showed that purple yam starch granules were not completely disrupted during bread baking. The fluorescence intensity of α-amylase and amyloglucosidase was reduced in bread made with purple yam flour. The decreased digestibility of starch in bread made with purple yam flour was due to the relatively intact starch granules from purple yam flour and possibly an inhibitory effect on digestive enzymes by purple yam flour.

This paper describes a new method to prepare spherulites from normal corn starch by a combination of enzymatic (mixtures of α-amylase and amyloglucosidase) and acid hydrolysis followed by recrystallization of the hydrolyzed products. The resulting spherulites contained a higher proportion of chains with a degree of polymerization (DP) of 6-12 and a lower proportion of chains with DP of 25-36, compared to those of native starch. The spherulites had an even particle size of about 2 μm and a typical B-type crystallinity. The amounts of long- and short-range molecular order of double helices in starch spherulites were larger, but the quality of starch crystallites was poorer, compared to that of native starch. This study showed an efficient method for preparing starch spherulites with uniform granule morphology and small particle size from normal corn starch. The ratios of α-amylase and amyloglucosidase in enzymatic hydrolysis had little effect on the structure of the starch spherulites.

The physicochemical and in vitro digestibility properties of starches isolated from four varieties of field peas grown in China were determined. Field pea starch granules were oval, round, even though there were many irregularly shaped granules with sizes between 21.5 and 23.9 μm. Zhongwan-6 showed the highest amylose content (36.0%), whereas Baofeng-3 showed the lowest amylose content (33.2%). All starches exhibited a C-type X-ray diffraction pattern, with relative crystallinity ranging between 27.0 and 30.2%. Zhongwan-6 had the highest relative crystallinity and the value of 1047/1022 cm −1 . Baofeng-3 exhibited the highest swelling power (10.30 g/g) and Cai exhibited the lowest swelling power (8.45 g/g). Ma had the highest T o and T p , but the lowest Δ H and narrowest R, whereas Zhongwan-6 showed the lowest T o and T p , but the highest Δ H . Zhongwan-6 and Ma starches showed the lowest and highest pasting viscosities. The gel of Zhongwan-6 was the hardest and Baofeng-3 was the softest. The in vitro digestibility studies showed that Baofeng-3 starch may be more effective than other starches in moderating post-prandial blood glucose levels.

The objective of this study is to increase our understanding of the heritability of starch quality characteristics, and of their sensitivity to effects of the growing environment. To this end, variability of pasting, thermal and gel properties of starch was examined using grains of five varieties of wheat (Triticum aestivum L.), grown in commercial cropping systems in five locations in Australia in 2 years. About 60–70% of the variability of DSC thermal properties and hardness of starch gels kept at 4°C for 24 h was contributed by factors related to growing conditions. Starch pasting properties had a higher degree of heritability (30–35%), although environmental conditions also contributed significantly to variability. A key effect of the growing environment appeared to be on the stability of the crystallites in the starch granules. While the results obtained are characteristic of the varieties used in this study, and of the specific environmental factors that influenced crop growth, the results nevertheless indicate that atmospheric and soil conditions can affect functional properties of starch that are important in foods and other applications. The finding that pre-anthesis conditions seem to affect the structure of starch raises interesting questions about the mechanism of starch biosynthesis in wheat grains.

Starch retrogradation is a process in which disaggregated amylose and amylopectin chains in a gelatinized starch paste reassociate to form more ordered structures. Starch retrogradation has been the subject of intensive research over the last 50 years, mainly due to its detrimental effect on the sensory and storage qualities of many starchy foods. However, starch retrogadation is desirable for some starchy food products in terms of textural and nutritional properties. To better understand the effect of starch retrogradation on the quality of starchy foods, measurement methods of starch retrogradation and factors that influence starch retrogradation have been studied extensively. This article provides a comprehensive review of starch retrogradation including the definition of the process, molecular mechanisms of how it occurs, and measurement methods and factors that influence starch retrogradation. The review also discusses the effect of retrogradation on the in vitro enzyme digestibility of starch. Spectroscopic methods such as FTIR and Raman are considered to be very promising in characterizing starch retrogradation at a molecular level, although more studies are needed in the future.

A thorough understanding of starch gelatinization is needed to control starch functional properties for food processing and human nutrition. Here, we reveal the mechanism of structural disassembly of rice, maize and wheat starch granules during thermal transitions in which a Rapid Visco Analyzer (RVA) was used to pre-heat the starches to certain transition points in the differential scanning calorimetry (DSC) heating profiles. This was done to generate sufficient material for structural analyses. The results from DSC, Raman, X-ray diffraction and scanning electron microscopy (SEM) analyses all showed that at the conclusion temperature (Tc) of the DSC endotherm rice starch gelatinization was complete, whereas residual structural order remained in maize and wheat starches. Gelatinization of wheat and maize starch was complete at a temperature higher than Tc in the profile, which we define as the end temperature (Te). We propose that Te would be better to define the completion point of starch gelatinization than Tc.

Acid hydrolysis is an important chemical modification that can significantly change the structural and functional properties of starch without disrupting its granular morphology. A deep understanding of the effect of acid hydrolysis on starch structure and functionality is of great importance for starch scientific research and its industrial applications. During acid hydrolysis, amorphous regions are hydrolyzed preferentially, which enhances the crystallinity and double helical content of acid hydrolyzed starch. This review discusses current understanding of the effect of acid hydrolysis on starch structure and functionality. The effects of acid hydrolysis on amylose content, chain length distribution of amylopectin molecules, molecular and crystalline organization (including lamellar structure) and granular morphology are considered. Functional properties discussed include swelling power, gelatinization, retrogradation, pasting, gel texture, and in vitro enzyme digestibility. The paper also highlights some promising applications of acid hydrolyzed starch (starch nanocrystals) in the preparation of biodegradable nanocomposites, bio-hydrogen, and slowly digestible starch-based healthy foods.

Pre-treatments by freezing/thawing (F/T) and hydrothermal-alkali (HA) were used in the modification of starch with octenyl succinic anhydride (OSA). In comparison with OSA-modified starch prepared without pre-treatment (degree of substitution, DS = 0.0172; reaction efficiency, RE = 73.9%), HA pre-treatment increased the DS of OSA-starch and RE of subsequent OSA modification (0.0185 and 79.7%, respectively). In contrast, F/T pre-treatment gave the opposite results (0.0152 and 65.5%, respectively). OSA modification markedly increased the viscosities but decreased the gelatinization parameters of native starch. Esterification of starch by OSA was confirmed with Fourier transform infrared and Raman spectroscopy, which indicated markedly decreased short-range molecular orders of native starch. The present study showed that HA pre-treatment before OSA modification is an efficient way to improve the reaction efficiency of OSA with starch and thereby to modify the pasting properties of starch. F/T pre-treatment did not increase the reaction efficiency of starch with OSA.

The relationship between swelling behaviour and thermal transitions of starch was investigated by differential scanning calorimetry (DSC) in combination with swelling power of starch. Sodium dodecyl sulphate (SDS)-treated wheat, waxy maize and potato starches showed increasing swelling power with increasing water/starch ratio. In contrast, swelling power of untreated wheat and high-amylose maize starches increased initially with increasing water/starch ratio, and then remained essentially unchanged above a certain ratio. The main endotherm G of native and SDS-treated wheat starch broadened progressively with increasing water/starch ratio up to 10:1. SDS-treated wheat, waxy maize and potato starches showed a typical endotherm over the whole range of water/starch ratios from 0.33:1 to 25:1, but the maximum enthalpy change occurred at different water/starch ratios. Our results indicate that thermal transition behaviour of starch granules is a very complex process, which involves swelling and leaching of starch polymer molecules rather than the dissociation of double helices or melting of crystallites.

Glucosinolates are key metabolites in Brassica plants and known for their anticancer and antimicrobial properties. Biotic stress in plants causes changes in metabolite biosynthesis. Various biosynthetic pathways are also triggered in chemically treated plants. The influence of hydrolyzed glucosinolates and defense activator applications on the plant’s ability to withstand disease infection and the influence of disease on glucosinolate hydrolysis has been examined. Potential effects of white rust disease caused by Albugo candida (Pers. Kuntze) on glucosinolates and their interactions are reviewed here. Effects of external plant defence activators Bion (Syngenta, Inc., Sydney, NSW, Australia) and phosphonate on glucosinolate metabolism in Brassica plants infected with A. candida has also been reviewed.

The aim of this study was to investigate the effect of NaCl on the formation, structure and property of samples formed from wheat starch (WS) and the fatty acids (lauric acid (LA), myristic acid (MA), palmitic acid (PA) and stearic acid (SA)). Results from RVA, DSC, XRD and Raman analyses showed that LA, and to a lesser extent MA, formed complexes with WS. Under the experimental conditions used, only minor amounts of WS-PA and WS-SA complexes formed. The low solubility of PA and SA, and to some extent MA, in water caused these fatty acids to mostly self-aggregate. The presence of NaCl promoted the formation of WS-LA complexes and, to a lesser extent complexes with MA, but had little effect on the formation of WS-PA and WS-SA complexes. Solubility of fatty acids in aqueous medium was proposed to be a major factor for the formation of starch-fatty acid complexes.

Potatoes are a popular source of dietary carbohydrate worldwide and are generally considered to be a high glycemic index (GI) food. Potato starch characteristics play a key role in determining their rate of digestion and resulting glycemic response. Starches isolated from seven potato cultivars with different GI values, including a low GI cultivar (Carisma), were examined for relative crystallinity, granule size distribution, amylopectin chain length, and thermal and pasting properties. Starch from the Carisma cultivar was more thermally stable and more resistant to gelatinization, with significantly higher (p < 0.05) pasting temperature and differential scanning calorimetry (DSC) gelatinization onset, peak and conclusion temperatures, compared to the other cultivars. Differences between the potatoes in the other properties measured did not align with the GI ranking. Thermal analysis and starch pasting properties may be useful indicators for preliminary identification of potato cultivars that are digested slowly and have a lower GI.

Potatoes are usually a high-glycaemic index (GI) food. Finding a low-GI potato and developing a screening method for finding low-GI cultivars are both health and agricultural priorities. The aims of the present study were to screen the commonly used and newly introduced cultivars of potatoes, in a bid to discover a low-GI potato, and to describe the relationship between in vitro starch digestibility of cooked potatoes and their in vivo glycaemic response. According to International Standard Organisation (ISO) guidelines, seven different potato cultivars were tested for their GI. In vitro enzymatic starch hydrolysis and chemical analyses, including amylose content analysis, were carried out for each potato cultivar, and correlations with the respective GI values were sought. The potato cultivars had a wide range of GI values (53–103). The Carisma cultivar was classified as low GI and the Nicola cultivar (GI = 69) as medium GI and the other five cultivars were classified as high GI according to ISO guidelines. The GI values were strongly and positively correlated with the percentage of in vitro enzymatic hydrolysis of starch in the cooked potatoes, particularly with the hydrolysis percentage at 120 min (r 0·91 and P <0·01). Amylose, dietary fibre and total starch content was not correlated with either in vitro starch digestibility or GI. The findings suggest that low-GI potato cultivars can be identified by screening using a high-throughput in vitro digestion procedure, while chemical composition, including amylose and fibre content, is not indicative.