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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.

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.

Dental calculus (mineralized dental plaque) was first recognised as a potentially useful archaeological deposit in the 1970s, though interest in human dental calculus as a resource material has increased sharply in the past few years. The majority of recent research has focused on the retrieval of plant microfossils embedded in its matrix and interpretation of these finds as largely the result of deliberate consumption of plant-derived food. However, while most of the material described in published works does represent food, dental calculus is in fact a "depositional environment" as material can enter the mouth from a range of sources. In this respect, it therefore represents an archaeological deposit that can also contain extensive non-dietary debris. This can comprise a wide variety of cultural and environmental material which reaches the mouth and can become embedded in dental calculus through alternative pathways. Here, we explore the human behaviors and activities besides eating that can generate a flux of particles into the human mouth, the broad range of additional cultural and environmental information that can be obtained through the analysis and contextualisation of this material, and the implications of the additional pathways by which material can become embedded in dental calculus.

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.

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...

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.

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.

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.

Grains of two wheat (Triticum aestivum L.) cultivars, Sunco and Sunsoft, were stored at 4°C and 30°C for 270 days to examine changes in proteins during storage. When whole meal flour extracted from the grains was analyzed using an unfractionated protein extraction procedure, no significant changes were found in protein content or SDS-PAGE profile for either cultivar in samples stored at 30°C compared with those stored at 4°C. Fractionation of the flour samples from stored grain into soluble and insoluble proteins revealed increases in soluble protein content for both cultivars stored at 30°C compared with 4°C. The soluble protein content, expressed as a percentage of the total protein, increased by 1.5% (P = 0.032) for Sunco and by 8.0 % (P = 0.158) for Sunsoft during storage at 30°C compared with those samples stored at 4°C. Analysis by SDS-PAGE and subsequent protein identification revealed that the most evident change that occurred during storage at 30°C was an increase in the content of high ...

Two cultivars of wheat (Triticum aestivum L.), Sunco and Sunsoft, were used to study the influence of storage time and temperature on the formation of starch-lipid complexes in flour pastes. Untreated and fat-reduced whole meal flours were stored separately for up to 12 months at 4, 20, and 30°C. The stored samples were analyzed for fat acidity, pasting properties, and iodine binding values. Fat acidity increased significantly in the untreated flour samples stored at 30 and 20°C compared with 4°C. Starch pasting properties, as measured using a Rapid Visco Analyser (RVA) indicated that the final viscosity of untreated flour samples of both cultivars increased significantly with storage time and elevated temperature, and correlated positively with increased fat acidity. Iodine binding values of the RVA pastes decreased with storage time and elevated temperature, and correlated negatively with fat acidity and final viscosity. The fat-reduced Sunco and Sunsoft flours showed less pronounced changes co...

Morphological and structural features of starch from potato (Solanum tuberosa) and rice (Oryza sativa) have been examined using atomic force microscopy. Amylose from potato and rice was observed in aggregated structures, which are suggested to be a result of retrogradation during sample preparation. The degrees of polymerization of amylose from potato and rice starches were calculated from the mean contour lengths of the observed structures to be approximately 1440 and 1860, respectively. Potato amylopectin appeared as a highly branched and extended molecule. Our results show that atomic force microscopy provides a useful method for examining the fine structural features and estimating the dimensions of starch molecules.

The pasting behavior of flour from several Australian rice (Oryza sativa L.) cultivars, differing in amylose content and grown in three different locations and three seasons, were determined using the Rapid Visco Analyser. Genotype, growth season, and growth location all affected the pasting behavior of rice flour. The amylose content of the same cultivar was significantly higher in the coolest growing season, resulting in RVA traces with lower peak viscosity and higher setback than samples with lower amylose content. When the same cultivar of rice was grown in different locations in the same season, there were no significant differences in the total starch, protein, lipid, and amylose content of the flour, but there were significant differences in the pasting behavior. This indicates that environmental as well as genetic factors influence the pasting behavior of rice flour. Flour from parboiled and quick-cooking rice did not paste and had low viscosities compared with unprocessed rice. Results f...

Raw and processed grains of rice (Oryza sativa) were examined using the environmental scanning electron microscope (ESEM), which allows specimens to be imaged at high resolution with minimal preparation. Images were obtained for milled rice grains that were fractured along natural transverse fracture planes. The images showed two distinct features: a smooth surface, where the fracture plane is suggested to be between endosperm cells, and a rough, more disorganised surface, which is likely to correspond to the fracture plane passing through an endosperm cell. Individual starch granules exposed in the fractured surface ranged from 3 to 11 µm in diameter. The ESEM revealed morphological differences between grains of different varieties. Parboiled rice showed a glassy fracture surface in which features of endosperm cells and starch granules were clearly recognisable but smaller than those of uncooked rice grains. Rice grains that had been heated and puffed showed a complete loss of organisational structure. The ESEM was able to capture the effect of processing treatments on the organisational structure of the grains. Copyright © 2004 Society of Chemical Industry

The present study addresses an aspect of genotype by environmental influences on cereal grain quality that has not been researched extensively. The susceptibility of raw and cooked starch to enzymic hydrolysis has been examined using a set of well-chararcterised wheat endosperm starch samples obtained from five wheat varieties grown in four different locations in two years. Native starch granules were hydrolyzed slowly, with genotype contributing most of variance between the samples during the initial stages of hydrolysis. Surface properties of the granules influenced the initial stages of hydrolysis. Environmental factors become increasingly influential as hydrolysis progressed, accounting for almost 50% of variance at 24 h, when 70-80% of the starch had been hydrolysed. Of the environmental conditions associated with growing locations, temperatures before flowering and during grain filling were identified as contributing to variability in the susceptibility of native starch to enzyme hydrolysis. Cooked starch was hydrolysed much more rapidly than native granules, with 80% of starch breakdown occurring within 90 min. For cooked starch, genotype contributed about 60-70% of the variance in the amount of starch hydrolysed within 30 min and in the amount of starch remaining after 2 h. The strong genetic influence on the susceptibility of both native and cooked wheat starch to enzymic hydrolysis indicates the heritability of these characters.

Acetohydroxyacid synthase (AHAS, EC 4.1.3.18; also known as acetolactate synthase), which catalyses the first reaction common to the biosynthesis of the branched-chain amino acids, L-valine, L-leucine and L-isoleucine, and is the target of several classes of herbicides, has been studied in hydroponically-grown seedlings of wheat (Triticum aestivum L. cv. Vulcan). Enzyme activity was greater in leaves than roots, reaching a maximum between 4 and 6 days after germination. AHAS was associated with the chloroplasts after centrifugation in a density gradient. A preparation of the enzyme was obtained from wheat leaves which gave a single band after electrophoresis in native gels but was resolved by denaturing sodium dodecyl sulphate-polyacrylamide gel electrophoresis into three polypeptide bands of molecular mass 58, 57 and 15 kDa. The native molecular mass was approximately 128 kDa. AHAS had optimum activity at pH 7 and did not require the addition of flavin adenine dinucleotide (FAD), thiamine pyrophosphate (TPP) and MgCl 2 for activity. The enzyme did not display typical hyperbolic kinetics, in that the double reciprocal plot of activity against pyruvate concentration was non-linear. The concentration of pyruvate that gave half of the maximum activity was 4 mM. Sulfonylurea and imidazolinone herbicides were potent inhibitors of wheat leaf AHAS, with 50% inhibition being observed at concentrations of 0.6 and 0.3 μM for chlorsulfuron and metsulfuron methyl, respectively, and at 2.5, 5 and 10 μM for imazaquin, imazethapyr and imazapyr. Inhibition by both classes of compounds was reversed by removal of the inhibitor. Progress curves of product formation against time in the presence of the herbicides were non-linear, and based on the assumption that inhibition by the sulfonylureas was of the slow, tight-binding type, estimates of 0.17 and 0.1 nM were obtained for the dissociation constants of chlorsulfuron and metsulfuron methyl, respectively, from the steady-state enzyme-inhibitor complex.

Two phosphofructokinases (EC 2.7.1.11; PFK) have been isolated from the host fraction of nitrogen–fixing chickpea (Cicer arietinum L.) root nodules that were formed with Rhizobium sp. (Cicer) CC1192. The predominant enzyme, which is suggested to be cytosolic, was isolated as a large aggregate of molecular mass near 2 000 kDa and was purified to a high degree. The less abundant enzyme, suggested to be of plastid origin, had a native molecular mass of 186 kDa. Both forms of PFK displayed typical hyperbolic kinetics with MgATP and fructose-6-phosphate. The major form of PFK was strongly inhibited by phosphoenolpyruvate, 2-phosphoglycerate and 3-phos-phoglycerate, and to a lesser extent by ADP, pyrophosphate, glucose-6-phosphate and 6-phosphogluconate. KCl and phosphate were activators and relieved the effect of inhibitors. The major PFK was disaggregated in the presence of ATP into a species which had a molecular mass of approximately 550 kDa and a lower affinity for fructose-6-phosphate.

The effects of aluminium ions on respiration of excised root apices from wheat (Triticum aestivum L. cv. Vulcan) and on isolated mitochondria have been investigated. Addition of 75μ M aluminium to the growth medium of 4-day-old seedlings inhibited O2 uptake by excised root apices by 23 and 35% after 12 and 24 h, respectively. This decreased rate of respiration was initially caused by inhibition of the cytochrome pathway of mitochondrial electron transport. The cyanide-insensitive, alternative pathway was inhibited only after more prolonged exposure to aluminium. Mitochondria isolated from roots of aluminium-treated seedlings had reduced oxidative capacity with substrates that supply electrons to Complexes I and II, compared with mitochondria from roots of untreated control seedlings. The state 3 and state 4 rates of O2 uptake and the uncoupled rates with these substrates were also inhibited when aluminium was added directly to reaction mixtures containing mitochondria isolated from untreated plants. In contrast, when aluminium was added to reaction mixtures oxidizing exogenous NADH, state 4 O2 uptake was stimulated, whereas no effect was observed on the state 3 rate or the rate in the presence of uncoupler. The results suggest that aluminium initially affects electron flow through Complexes I and II, and that after more prolonged exposure, aluminium may also interact with other sites in mitochondria.

Polyclonal antibodies raised against NAD-dependent glyceraldehyde-3-phosphate dehydrogenase (D-glyceraldehyde-3-phosphate:NAD+ oxidoreductase [phosphorylating], EC 1.2.1.12) from the plant cytosolic fraction of soybean [Glycine max (L.) Merr. cv. Williams] nodules were used to study the subcellular location of the enzyme and its relative distribution between infected, interstitial and cortical cells of soybean (cv. Lincoln) nodules. Post-embedding immunogold labelling was carried out on nodules harvested 5, 12, 19 and 25 days after the first sign of nodulation. Labelling for glyceraldehyde-3-phosphate dehydrogenase was observed over the cytoplasm and nuclei of infected and uninfected cells, as well as over the nucleoid regions of bacteroids. In 5-day-old nodules, label also bound adjacent to the peribacteroid membranes. Statistical analysis of the number of gold particles per cell area indicated that in 5-day-old nodules, glyceraldehyde-3-phosphate dehydrogenase was distributed equally between infected, interstitial and cortical cells, but in older nodules the enzyme was more prominent in the interstitial and cortical cells than in infected cells.

UDP-glucose pyrophosphorylase (EC 2.7.7.9) has been highly purified from the plant fraction of soybean (Glycine max L. Merr. cv Williams) nodules. The purified enzyme gave a single polypeptide band following sodium docecyl sulphate polyacryla-mide gel electrophoresis, but was resolved into three bands of activity in non-denaturing gels. The enzyme appeared to be a monomer of molecular weight between 30 and 40 kDa. UDP-glucose pyrophosphorylase had optimum activity at pH 8.5 and displayed typical hyperbolic kinetics. The enzyme had a requirement for divalent metal ions, and was highly specific for the substrates pyrophosphate and UDP-glucose in the pyrophosphorolysis direction, and glucose-1-phosphate and UTP in the direction of UDP-glucose synthesis. The Km values were 0.19 mM and 0.07 mM for pyrophosphate and UDP-glucose, respectively, and 0.23 mM and 0.11 mM for glucose-1-phosphate and UTP. The maximum velocity in the pyrophosphorolysis direction was almost double that for the reverse reaction. UDP-glucose pyrophosphorylase did not appear to be subject to a high degree of fine control, and activity in vivo may be regulated mainly by the availability of the substrates.

The wheat-grain proteome was investigated, as a basis for devising more efficient methods of cultivar identification or discrimination. Australian wheats (Halberd, Cranbrook, CD87 and Katepwa) were used as the basis of this study. These cultivars were selected on the basis of differences in the quality types represented, in terms of dough-processing attributes that can suit one cultivar better than another for specific types of industrial utilisation. Total wheat endosperm (flour) protein extracts were prepared from mature wheat for two-dimensional electrophoresis, across both acidic (pH 4-7) and basic (pH 6-11) pH ranges. Three particular regions of the proteome maps were chosen for close comparison, involving two sets of gluten proteins and a nongluten protein region (involving small heat shock proteins), based on previous protein characterisation. Differences in the nongluten protein regions (heat shock proteins and other unidentified polypeptides) are of particular interest as being possible targets for use in developing new approaches to cultivar discrimination, such as the development of simple immunoassays.

The subcellular location and properties of enzymes concerned with the phosphorylation of glucose and fructose in avocado (Persea americana Mill. cv. Hass) have been studied. A substantial amount of glucose-phosphorylating activity was particulate and fractionation of extracts by sucrose density gradient centrifugation indicated that most of this activity was associated with the mitochondria. Three hexose-phosphorylating enzymes were resolved by DEAE-cellulose chromatography of the cytosolic fraction. These were a hexokinase (EC 2.7.1.1), which had strong preference for glucose as substrate, and two specific fructokinases (EC 2.7.1.4). ATP was the preferred phosphoryl donor for the hexose kinases of avocado.

By feeding (methylene-14C)-L-tryptophan, a biosynthetic precursor of the alkaloid harman, to Passiflora edulis it can be shown that the concentration of (3-14C)-harman initially increases and then decreases. By feeding (3-14C)-harman, the decrease has been further investigated and found to be due to excretion and not catabolic reactions.