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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.

Reconstructing detailed aspects of the lives of Lower Palaeolithic hominins, who lived during the Middle Pleistocene, is challenging due to the restricted nature of the surviving evidence, predominantly animal bones and stone tools. Qesem Cave, Israel (420–200 ka) is a site that has produced evidence for a wealth of innovative features including controlled use of fire, represented by a repeatedly used hearth. Numerous charred bone and stone tools as well as wood ash have been found throughout the ten metres of archaeological deposits. Here, we describe the presence of a range of potentially inhaled, and ingested, materials extracted from samples of dental calculus from the Qesem Cave hominins. These finds offer an insight into the environment in and around the cave, while micro-charcoal highlights the need for smoke management in enclosed environments. Plant fibres and a phytolith may be evidence of oral hygiene activities or of using the teeth to work raw materials. Starch granules and chemical compounds provide a direct link to ingested plant food items. This extends the evidence for consumption of plant foods containing essential nutrients including polyunsaturated fatty acids and carbohydrates, into the Lower Palaeolithic. Together, these results represent a significant breakthrough towards a better understanding of Middle Pleistocene dietary breadth and highlight some of the challenges facing the adoption of the habitual use of fire for cooking by the Qesem Cave hominins, as well as offering an insight into their ecological knowledge and technological adaptability.

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 effects of pressure and temperature on the gelatinization properties of wheat starch were investigated. The long-range crystallinity and short-range molecular order were gradually destroyed under both conditions as the degree of gelatinization (DG) increased. With increasing DG, differential scanning calorimetry (DSC) onset (To), peak (Tp) and conclusion temperatures (Tc) increased for the heat-gelatinized samples but did not change greatly for the pressure-gelatinized samples. At similar DG, pressure-gelatinization resulted in less granule swelling than heat-gelatinization. Lower degree of both heat- and pressure-gelatinization resulted in increased pasting viscosities and gel texture parameters, whereas the opposite was noted at higher DG. We conclude that pressure and heat induced starch gelatinization in different ways, resulting in different gel texture properties. Pressure-gelatinization disrupted both less stable and more stable crystallites, whereas less stable crystallites were preferentially disrupted during heat-gelatinization.

Potato starch was pre-treated with CaCl

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.

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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.

Our aim was to study changes in wheat proteomes across different growth locations as the first step in linking protein composition with functional changes in grains produced with commercial production systems. Soluble and insoluble proteins were extracted sequentially from grain of three commercial wheat cultivars grown at four locations in New South Wales, Australia, during a single season. Bands were separated with SDS-PAGE and identified by peptide mass fingerprinting. Quantitative changes in the electrophoretic patterns were observed mainly in the insoluble polypeptides of molecular mass 40,000–70,000 for all three cultivars grown at two of the four locations. These proteins were identified as mainly globulin and serpin isoforms, as well as triticin. Other proteins with changed expression included disease-resistance proteins, class III peroxidase, starch branching enzyme I, β-amylase, and storage proteins. Two-dimensional electrophoretic analysis was performed on two of the same wheat cultiva...

The objectives of this study were to assess how functional properties of proteins in whole meal wheat (Triticum aestivum L.) flour vary across different growth environments. Grain from three commercial Australian Hard milling wheat cultivars was analyzed from four growth locations in 2008 and from two of the corresponding cultivars and locations in 2009. The protein content of the grain, soluble and insoluble extractable protein fractions, swelling index of glutenin (SIG), glutenin-to-gliadin ratio (Glu:Gli), percent unextractable polymeric protein (%UPP), and dough properties including force at maximum resistance (Rmax) and extensibility were measured. Based on analysis of variance of aggregated data for the cultivars, growth locations, and seasons, growth environment factors made significant contributions to variability in the total grain protein, Glu:Gli ratio, %UPP, SIG, Rmax, and extensibility of the wheat flour. Variability of protein content of the soluble and insoluble extractable protein...

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.

The aim of the present study was to characterize the multiscale structures of ternary complexes of a model system of starch, fatty acid (FA), and β-lactoglobulin (βLG) prepared using a Rapid Visco Analyzer (RVA). The addition of βLG to starch-lauric acid or starch-oleic acid RVA pastes resulted in the increased intensity or occurrence of a new viscosity peak during cooling when the RVA protocol was repeated. The viscosity peak was attributed to the formation of starch-βLG-FA complexes. Differential scanning calorimetry (DSC) results showed clearly that the starch-βLG-FAs complex was formed as gelatinized starch was cooled in the presence of βLG and FAs. The results of Raman, FTIR, and X-ray diffraction analyses showed that starch can interact with βLG and FAs to form a ternary V-type crystalline complex, which had a greater short-range molecular order and higher relative crystallinity compared with those of the binary starch-FA complex. The present study provided insights into the structure of a model starch-protein-fatty acid complex as an example of what might occur during food processing.

The effect of high pressure (HP) treatment at 200-600MPa for 30min on properties of three starches with different polymorphs was investigated. HP treatment altered greatly the morphology of wheat starch, especially at 400MPa or higher. The crystallinity of wheat starch decreased from 22.6% for native starch to 3.4% for starch after treatment at 600MPa. The short-range molecular order as measured by FTIR and Raman spectroscopy decreased with increasing treatment pressure. HP treatment had little effect on structural properties of potato and yam starches, except for yam starch after treatment at 600MPa. HP treatment decreased the pasting viscosities of wheat starch except for the treatment at 200MPa, which increased the peak, trough and final viscosities by 6.7, 11.1 and 5.7%, respectively. The peak viscosity of potato and yam starches was increased respectively by 14.0 and 11.3% after HP treatment at 600MPa. HP treatment at 600MPa enhanced greatly the final digestion percentages of wheat and yam starch by 20 and 26.4%, but had little effect on potato starch. The above results showed that wheat starch was more susceptible to the effects of HP treatment than did yam and potato starches, and that C-type yam starch behaved more likely the B-type potato starch to HP treatment.

Sima del Elefante, Atapuerca, Spain contains one of the earliest hominin fragments yet known in Europe, dating to 1.2 Ma. Dental calculus from a hominin molar was removed, degraded and analysed to recover entrapped remains. Evidence for plant use at this time is very limited and this study has revealed the earliest direct evidence for foods consumed in the genus Homo. This comprises starchy carbohydrates from two plants, including a species of grass from the Triticeae or Bromideae tribe, meat and plant fibres. All food was eaten raw, and there is no evidence for processing of the starch granules which are intact and undamaged. Additional biographical detail includes fragments of non-edible wood found adjacent to an interproximal groove suggesting oral hygiene activities, while plant fibres may be linked to raw material processing. Environmental evidence comprises spores, insect fragments and conifer pollen grains which are consistent with a forested environment.

A thorough understanding of starch gelatinization is extremely important for precise control of starch functional properties for food processing and human nutrition. Here we reveal the molecular mechanism of starch gelatinization by differential scanning calorimetry (DSC) in conjunction with a protocol using the rapid viscosity analyzer (RVA) to generate material for analysis under conditions that simulated the DSC heating profiles. The results from DSC, FTIR, Raman, X-ray diffraction and small angle X-ray scattering (SAXS) analyses all showed that residual structural order remained in starch that was heated to the DSC endotherm end temperature in starch:water mixtures of 0.5 to 4:1 (v/w). We conclude from this study that the DSC endotherm of starch at a water:starch ratio of 2 to 4 (v/w) does not represent complete starch gelatinization. The DSC endotherm of starch involves not only the water uptake and swelling of amorphous regions, but also the melting of starch crystallites.

The effect of alkaline treatment on the structural and functional properties of pea starch granules was studied using a range of characterization methods including amylose content, scanning electron microscopy (SEM), X-ray diffraction (XRD), 13 C nuclear magnetic resonance (NMR), swelling power, differential scanning calorimetry (DSC), the Rapid Visco Analyser (RVA) and in vitro digestibility. The amylose content decreased by about 20–25% after 15 days of alkaline treatment and there were small decreases in relative crystallinity and double helix content. Deformations were observed on the surface of alkali-treated granules, and there was evidence of adhesion between some of the granules. There was a 25–30% reduction in peak and final RVA pasting viscosities, but only a small reduction in swelling power. The endothermic transition of alkali-treated starch was broadened with a shift of the endothermic peak to higher temperature. However, the endothermic enthalpy remained largely unaffected. Alkali-treatment greatly increased the rate of in vitro enzymatic breakdown of the pea starch. More prolonged alkaline treatment for 30 days did not cause further significant changes to the structural and functional properties of the starch granules. The effects of alkali on structure and function of pea starch are explained on the basis of limited gelatinization of the granules.

A method is described for extracting and comparing internal granule proteins from a normal commercial soft wheat variety (QAL2000) and related wx starch mutants (QA-Wx-59 and QA-Wx-1). Our results demonstrate that granule-bound starch synthase I (GBSS I) was by far the most abundant internal protein of starch granules from QAL2000. Several minor, smaller bands observed in gels were also identified by MS as GBSS I peptides. The GBSS I peptides were detected in only trace amounts in the wx mutants. Proteins corresponding to other starch biosynthetic enzymes were present in QAL2000 and the wx mutants.

The effect of acid hydrolysis on the swelling power of pea starch granules was studied by field emission SEM (FE-SEM). The swelling power of the native starch granules (g water absorbed/g dry starch) was 13, and this decreased to less than 2 after 1 day of acid hydrolysis. The proportion of the starch that was soluble in hot water increased from 15% for native starch to 75% after 1 day of hydrolysis. The swelling power of the starch decreased further, and solubility increased, with more extended hydrolysis. The decrease in swelling power and increase in solubility were attributed mainly to the disruption of side chains of amylopectin. Observations with FE-SEM indicated that starch granules were still able to melt and coalesce after 1 day of acid hydrolysis, but after 2 days solubilization of starch chains occurred predominantly rather than swelling when the granules were heated in excess water. The intactness of amylopectin is proposed to play a crucial role in the swelling power of starch granules and in the structure of granule ghosts.

The degradation of pea starch granules by acid hydrolysis has been investigated using a range of chemical and structural methods, namely through measuring changes in amylose content by both the iodine binding and concanavalin A precipitation methods, along with small angle X-ray scattering (SAXS), wide angle X-ray diffraction (XRD) and field emission scanning electron microscopy (FE-SEM). The relative crystallinity, intensity of the lamellar peak and the low- q scattering increased during the initial stages of acid hydrolysis, indicating early degradation of the amorphous regions (growth rings and lamellae). In the first 2 days of hydrolysis, there was a rapid decline in amylose content, a concomitant loss of precipitability of amylopectin by concanavalin A, and damage to the surface and internal granular structures was evident. These observations are consistent with both amylose and amylopectin being located on the surface of the granules and attacked simultaneously in the early stages of acid hydrolysis. The results are also consistent with amylose being more concentrated at the core of the granules. More extensive hydrolysis resulted in the simultaneous disruption of amorphous and crystalline regions, which was indicated by a decrease in lamellar peak intensity, decrease in interhelix peak intensity and no further increase in crystallinity. These results provide new insights into the organization of starch granules.

Thermal transitions of native and acid-hydrolysed starch were investigated for the first time by employing differential scanning calorimetry (DSC) in combination with field emission scanning electron microscopy (FE-SEM) to examine morphological changes in the starch after hydrothermal treatment in the DSC pans. The characteristic, well-defined endothermic transition was observed in the DSC traces for native starch and starch after one day of acid hydrolysis, but after two days of hydrolysis the endothermic transition became broad and undefined. After heating in DSC pans, native starch was observed visually and with SEM to have formed a gel, whereas starch granules hydrolysed for one day appeared to have undergone only limited swelling and coalescence. Starch that had been hydrolysed for two or more days appeared powdery and SEM images revealed that the granules had undergone very little swelling. The thermal transitions of native and acid-hydrolysed starch are interpreted in terms of the theory of polymer swelling and dissolution. Native granules and granules with only minimal acid damage are able to swell within the constraints of the water-limited conditions of DSC, but as acid hydrolysis progresses the capacity of the granules to swell is decreased and endothermic transitions are increasingly due to dissolution of polymer chains. An exothermic transition that followed the main endothermic transition is proposed to be due to the condensation of water vapour on the lid of the DSC pan.

The effects of repeated heating and cooling on the properties of pastes prepared from a commercial wheat starch (Triticum aestivum L.) with added monoglycerides were studied using a Rapid Visco Analyser (RVA). The nanostructure of the freeze-dried pastes was determined by X-ray diffraction and small-angle X-ray scattering. Pastes prepared from the wheat starch alone, or from the starch mixed with tripalmitin, which does not form complexes with starch, produced regular viscosity profiles in the RVA when subjected to multiple heat-cool cycles. In comparison, the effects of adding monoglycerides (or monoacylglycerols) depended on the chain length and saturation of the fatty acid of the monoglyceride. Repeated heat-cool cycles in the RVA of the starch with different monoglycerides induced the formation of complexes of varying stability that influenced the viscosity trace of the paste during multiple heating and cooling cycles. Small-angle X-ray scattering in combination with X-ray diffraction proved useful in describing the nanostructural changes in the RVA pastes induced by monoglycerides and temperature cycling. The results indicate that the functional properties of starch pastes may be manipulated through the strategic selection of an added monoglyceride.

Starch was isolated from seven varieties of field peas (Pisum sativum L.) and characterised using a combination of physical, chemical and functional tests. The total starch content of the peas ranged between 34% and 42.7% of dry matter, and the amylose content of the starch was between 35% and 38%. Average particle diameter of the seven starches varied between 21.4 and 26.1 μm. All of the pea starches gave a typical C-type X-ray diffraction pattern, with relative crystallinity ranging between 36% and 55% and the proportion of B-type crystallites between 3.8% and 30.4%. Although there were only small differences between the starches in amylose content, they displayed significant variability in functional properties, including swelling power, pasting characteristics, thermal transition temperatures in the differential scanning calorimeter, and in susceptibility to in vitro attack by α-amylase. The results indicate the importance of structural characteristics of starch molecules, particularly amylopectin, as determinants of the properties of native starch granules.

Scanning electron microscopy (SEM) and X-ray diffraction (XRD) were employed to investigate degradation patterns of native starch granules from wheat (Triticum aestivum L.) by different starch-degrading enzymes. The starches examined were from a waxy wheat and four varieties with slightly elevated amylose content, but with different functional properties. Differences in the digestion patterns after partial α-amylolysis of starch granules were noted between the starches. The waxy starch seemed to be degraded by endocorrosion, whereas the amylose-rich starches followed a slower mode of hydrolysis starting from the granular surface. X-ray diffractograms of the amylose-rich starches were not significantly altered by 2 h of α-amylolysis, whereas partial hydrolysis of the waxy starch decreased scattering intensity at higher 2θ angles, consistent with a different mode of attack by α-amylase in the initial digestion stages of granules of waxy and amylose-rich starches. We propose these differences are due to the combined effects of the change in packing density and partial preference for hydrolysis of amorphous material. The native starch granules were also attacked by beta-amylase, isoamylase and amyloglucosidase, which indicates that α-amylase is not the only starch-degrading enzyme that is able to initiate starch hydrolysis of native granules.

The susceptibility of wheat ( Triticum aestivum L .) starches to hydrolysis by pancreatic α-amylase in vitro was investigated using a series of 35 starches with slightly enriched amylose content within a narrow range (36–43%), but widely differing functional properties. After 2 h of incubation with α-amylase, native starch granules were digested to different extents, but there were no differences between any of the starches once they were gelatinized. Cooling the starch for 72 h at 4 °C after cooking reduced the susceptibility of all of the starches to enzymic digestion by a similar extent, whereas addition of monopalmitin decreased the digestibility of the starches that contained amylose, but did not affect the digestibility of waxy starches that were also included in the study. Amylopectin chain length distribution of partly digested starch granules displayed increased proportion of short and medium chains and decreased proportion of long chains in comparison to native granules. Separated large (A) and small (B) starch granules from three of the starches differed significantly in their susceptibility to in-vitro digestion. A predictive model of the susceptibility of starch in the different forms was developed from the physico-chemical and functional properties of the starches.

Image analysis techniques have been used to investigate the likelihood of being able to classify and assign a probability regarding the plant origin of individual starch granules in a collection of granules. Quantifiable variables were used to characterize the granules, and the assignments and probabilities were calculated objectively. We consider the classification of images containing granules of a single species and of mixed species and the possibility of assigning a class to granules of unknown species in an image of a slide obtained from the dental calculus of chimpanzees.

An experiment was conducted using three related wheat (Triticum aestivum L.) genotypes grown on two different soil types (a grey vertosol and a red kandosol) using two different tillage practices (complete and zero) to test the effects of environmental influence on grain quality. Wheat grains from plants grown in each environment were milled into flour; protein and starch were analyzed. The soil type had the biggest impact on both protein and starch content, with the grains from the grey vertosol soil having higher total, insoluble, and soluble protein contents, and lower starch content and flour swelling values. When protein was analyzed using SDS-PAGE, the major difference observed between grains from the two soil types was an increased intensity of polypeptide bands corresponding to β-amylase in grains from plants grown on grey vertosol soils.

The properties of starch and starch–lipid pastes have been explored using a novel extended Rapid Visco Analyser (RVA) profile, in which the heating and cooling cycles are repeated five times. Starches from four wheat varieties with amylose content ranging from 23 to 27%, and waxy starches of wheat, rice and maize were tested, alone and in mixtures with lauric acid and monopalmitin (glyceryl-1-monopalmitin). Gels of all of the starches formed and melted reproducibly during repeated heating and cooling in the RVA. The addition of lauric acid to the waxy starches had no effect on the multiple RVA profile. Monopalmitin caused an increase in viscosity during the heating stage of the second to the fifth cycles with the waxy starches, which was attributed to the presence of monopalmitin aggregates. Changes in the multiple cycle viscosity traces observed when monopalmitin or lauric acid was added to the amylose-containing starches were complex. It was concluded that RVA paste viscosities were determined by starch–lipid interactions, as well as by free lipid in the starch mixtures. The water solubility of the lipid and association of proteins with starch granules influence these interactions.

Starch is a macro-constituent of many foods and its properties and interactions with other constituents, particularly water and lipids, are of interest to the food industry and for human nutrition. Starch varies greatly in form and functionality between and within botanical species, which provides starches of diverse properties but can also cause problems in processing due to inconsistency of raw materials. Being able to predict functionality from knowledge of the structure, and explain how starch interacts with other major food constituents remain significant challenges in food science, nutrition, and for the starch industry generally. This paper describes our current understanding of starch structure that is relevant to its functionality in foods and nutrition. Amylose influences the packing of amylopectin into crystallites and the organization of the crystalline lamellae within granules, which is important for properties related to water uptake. Thermal properties and gel formation appear to be influenced by both amylose content and amylopectin architecture. While amylose content is likely to have an important bearing on the functional properties of starch, subtle structural variations in the molecular architecture of amylopectin introduces uncertainty into the prediction of functional properties from amylose content alone. Our ability to relate starch granule structure to suitability for a particular food manufacturing process or its nutritional qualities depends not only on knowledge of the genetic and environmental factors that control starch biosynthesis, and in turn granule morphology, but also on how the material is processed.

Germination in the soft wheat (Triticum aestivum L.) cultivar Rosella was followed for three days after imbibition by proteomic analysis of the germ tissue. Two-dimensional electrophoresis was performed in triplicate for proteins extracted from embryos dissected from mature grain and from grains germinated for 1, 2, and 3 days. For this period, 63 proteins (in 86 spots) in the germ were identified as decreasing in abundance, 35 proteins (in 60 spots) as increasing in abundance, and 28 proteins (in 39 spots) as exhibiting no significant abundance change. Proteins with significant abundance changes are discussed in relation to physiology; these include proteases, amylases and amylase inhibitors, enzymes in lipid metabolism, proteins related to water stress, cell wall hydrolases, oxalate oxidase, and H+-ATPases. Functions associated with proteins synthesized during the germination period are inconsistent with the embryo of mature grain being fully primed for germination.

Five wheat (Triticum aestivum L.) starches, from the varieties Sunco, Sunsoft, SM1118, and SM1028, with similar amylose content, and a waxy wheat were separated into large (A) and small (B) granules. The unfractionated starches, and isolated A and B granules, were characterized structurally and evaluated for their functional properties. The amylopectin chain length distribution revealed that A granules had a lower proportion of short chains with degree of polymerization (DP) 6-12 and a higher proportion of chains with DP 25-36 than B granules. X-ray diffraction (XRD) patterns showed predominantly A-type crystallinity for all of the starches. No differences in the crystallinity were found between unfractionated, A and B granules. Small-angle X-ray scattering (SAXS) patterns of the starches at 55% hydration showed that the lamellar repeat distance in A granules was larger than that of B granules for all the starches examined. However, the lamellar distances of both A and B granules from the waxy wheat were smaller than those of Sunco, Sunsoft, SM1118 and SM1028 starches. The swelling power of the B granules was greater than that of A granules from all five starches. The kinetics of digestion of A and B granules with α-amylase in vitro were complex, with B granules initially digested to a greater extent than A granules. After 4 h of incubation, A granules showed greater digestibility than B granules, except in the case of waxy starch where unfractionated and fractionated granules had similar in vitro digestibility. Correlations between structural and functional parameters were more significant for the isolated A and B granules than for the unfractionated starches. This study demonstrates that A and B granules differ in structure and functionality, and that some correlations between these properties could be masked in unfractionated starches with bimodal granule size distribution.