Enhanced efficiency fertilizers (EEFs) can reduce nitrogen (N) losses in temperate agriculture but are less effective in the tropics. We aimed to design a new EEF and evaluate their performance in simple-to-complex tests with tropical soils and crops. We melt-extruded urea at different loadings into biodegradable polymer matrix composites using biodegradable polyhydroxyalkanoate (PHA) or polybutylene adipate-co-terephthalate (PBAT) polymers with urea distributed throughout the pellet. These contrast with commercially coated EEF that have a polymer-coated urea core. We hypothesized that matrix fertilizers would have an intermediate N release rate compared to fast release from urea or slow release from coated EEF. Nitrogen release rates in water and sand-soil columns confirmed that the matrix fertilizer formulations had a more progressive N release than a coated EEF. A more complex picture emerged from testing sorghum [Sorghum bicolor (L.) Moench] grown to maturity in large soil pots, as the different formulations resulted in minor differences in plant N accumulation and grain production. This confirms the need to consider soil interactions, microbial processes, crop physiology, and phenology for evaluating fertilizer performance. Promisingly, crop δ15N signatures emerged as an integrated measure of efficacy, tracking likely N conversions and losses. The three complementary evaluations combine the advantages of standardized high-throughput screening and more resource-intensive and realistic testing in a plant-soil system. We conclude that melt-blended biodegradable polymer matrix fertilizers show promise as EEF because they can be designed toward more abiotically or more microbially driven N release by selecting biopolymer type and N loading rate.

Dietary fibre fortified products have increased in popularity as health-conscious consumers seek convenient ways to increase fibre intake. Fibres from wholegrains are particularly desirable inclusions in food products because of their proven physiological health-benefits. When fortifying beverages with fibre, however, the insoluble dietary fibre components present in wholegrains often contribute to unpleasant gritty sensations making the products unpalatable. Consequently, designing wholegrain-fortified beverages with sufficient fibre-content to make health related fibre claims is a major challenge in the food manufacturing industry. This work aims to take a systematic approach in identifying the texture/mouthfeel related sensory impact and interaction between two commercial oat fibre ingredients (Oatwell28XF® and Milled Oats) when added to a model beverage system. Eighteen samples were prepared containing either or both the ingredients, at varying levels, and were assessed by a trained panel using conventional sensory descriptive techniques. The results indicate that the two different oat bran fibres produced distinct mouthfeel perceptions which could be attributed to the varying soluble and insoluble fibre content of the samples. Insoluble dietary fibre concentrations above 2% (w/w) resulted in particle-related sensory properties chalkiness, dryness and particle perception, which dominated the overall mouthfeel and textural sensory perception of the samples. Samples with predominantly soluble β-glucan, resulted in perceptions of smoothness, sliminess and stickiness residue, while thickness, mouthcoating and cloying sensations were driven by total fibre concentration, irrespective of fibre solubility. This work provides a solid foundation for food manufacturers aiming to rationally design and develop nutritionally superior fibre-fortified beverages and is relevant to fibre content concentrations required for labelling/nutrition claims for consumer products in many developed nations.

High-moisture rice snacks, such as steamed rice cakes, develop firmness on storage which decreases shelf life significantly. By analogy with lower moisture bread systems, this staling was hypothesised to be due to a combination of starch retrogradation and moisture re-distribution. Therefore, food additives which are commonly used to retard starch retrogradation during bread staling, including enzymes, hydrocolloids and emulsifiers (alpha-amylase, alginate, xanthan, guar gum, carrageenan, carboxymethyl cellulose, distilled monoglyceride, and sodium stearoyl lactylate) were investigated for their anti-hardening effects in high-moisture rice snacks. The results showed that only alginate significantly reduced the firming rate of rice cakes. However, differential scanning calorimetry measurements surprisingly indicated that rice cakes with alginate had higher levels of starch retrogradation than the control after storage for 7 days. Magnetic resonance imaging results were characterised by a redistribution of signal intensity from the edge to the centre of rice cakes and the formation of high intensity regions. These features were stronger with the addition of alginate. We propose that the alginate forms a continuous phase with water that has high mobility, whereas the partially gelatinized starch granules are an included phase distributed within the continuous phase. The reduced hardness of aged rice cakes with alginate is more dependent on the soft continuous phase than the hard starch granules, therefore leading to a softer texture. This mechanism is different to that proposed to operate for lower water content baked systems, therefore hydrocolloid and other anti-staling agents which are effective in bread systems may not be applicable in higher moisture starchy foods.

The by-products of rice milling (BRM), which are predominately rice bran, are a potential source of soluble protein that has been underexploited due to difficulties in extraction. Significant advances have been made understanding how protein content changes with degree of milling (DOM) at the laboratory scale. However, these results cannot be compared due to the lack of information on how DOM affects protein extractability in industrially produced BRM. The colorimetry or particle size analysis may estimate milling degree in industrial scale, and protein extractability changes due to a series of abrasive milling passes. Both colorimetry and particle size could differentiate the industrial abrasive passes and correlated with the amount of bran/protein present. Both the 1st and 2nd pass of milling were suitable sources for the extraction. While the relative amount of protein extracted in each fraction changed, the protein profile of the major fractions was conserved between mill passes.

Causal relationships between physical properties and structure/composition of cooked rice are difficult to quantify when mechanical measurements are performed on bulk samples using large deformations that alter the structure irreversibly. We demonstrate here methods involving small-deformation to characterise the elastic modulus (E), adhesion and cohesion at the individual grain level, and show distinct differences between freshly cooked rice and shelf-stable retorted rice. On average, retorted rice is harder and less adhesive and cohesive than freshly cooked rice, but their distributions in each of these mechanical properties overlap. E is independent of adhesion and weakly correlated with moisture content. In addition, a ring-shear tester is shown to distinguish the bulk cohesion and flowing ability between rice samples. Measuring the inherent physical properties of individual grains has the potential to enable a more sensitive evaluation of new processes and grain varieties, and development of quantitative structure-property-processing relationships for rational design of products to perform optimally at different stages, from manufacturing through to oral processing.

5 Centre for Nutrition and Food Sciences, Queensland Alliance for Agriculture and Food Innovation, 6 University of Queensland, Brisbane 4072, Australia; 7 School of Agriculture and Food Sciences, University of Queensland, Brisbane 4072, Australia; 8 School of Chemical Engineering, University of Queensland, Brisbane 4072, Australia; 9 Basque Centre for Applied Mathematics (BCAM), Alameda de Mazarredo 14 48009 Bilbao, Bizkaia, 10 Spain. 11

High-moisture snacks, such as steamed buns and rice cakes, are traditional and popular in Asian countries. However, their shelf life is short, primarily due to microbial spoilage. Current manufacturing methods address this shortcoming through the use of chemical preservatives. To satisfy consumers’ demand for preservative-free food, thermal sterilisation of a model high-moisture snack (steamed rice cakes) is investigated in this work. Bacillus cereus spores are heat-resistant pathogens typically found in rice products; hence, they constitute a suitable candidate to assess the effectiveness of thermal sterilisation. A validated combination of predicted temperature profile of rice cakes based on thermal properties extracted experimentally with thermal inactivation kinetics of B. cereus spores allows us to assess the sensitivity of processing conditions to sterilisation efficiency. Using both experimentation and modelling, it is shown that enhancement of heat transfer by improving convection from the heating medium (either water or steam) has a limited effect on inactivation due to the intrinsic kinetics of spore inactivation.

Background: Commercially available convenience rice such as retorted, quick cooking or frozen rice suffers from sensory deficiencies compared to home cooked rice. The mechanisms causing deterioration in texture and flavour during convenience rice processing are, in many cases, poorly understood. Scope and approach: This review describes pre-cooking methods including washing and soaking, cooking methods including cooking in excess water, by absorption and by high pressure; and post-cooking technologies including cooling, freezing, retorting, canning, drying and storage, as well as the influence of each process on physical properties and sensory attributes of cooked rice. Key findings and conclusions: Water diffusion and starch leaching, which occur in many processing steps, are important factors affecting cooked rice quality. Soaking saves energy by reducing cooking time. Cooking by absorption increases stickiness, but does not ensure uniform moisture distribution compared to cooking in excess water, thus is not applicable for rice manufacturers. Amylose leaching during soaking and cooking affects hardness and stickiness of cooked rice significantly. Non-thermal treatments such as high pressure soaking and cooking have potential to improve rice sensory properties compared to high temperature treatments, which change colour and flavour of convenience rice. Drying and freezing results in a porous structure resulting in spongy texture after rehydration and thawing, respectively. During storage, starch retrogradation deteriorates texture, but can be retarded by high pressure processing or storage below the glass transition temperature. Much is known about processing factors that affect freshly cooked rice, but more substantial knowledge of how processing steps affect the structure property relationships and sensory properties of convenience rice will assist manufacturers to specifically design products to meet the ever growing consumer demands for convenience food. (C) 2016 Published by Elsevier Ltd.

The influences of molecular, crystalline and granular structures on the biodegradability of compression-molded starch films were investigated. Fungal α-amylase was used as model degradation agent. The substrates comprised varied starch structures obtained by different degrees of acid hydrolysis, different granular sizes using size fractionation, and different degrees of crystallinity by aging for different times (up to 14 days). Two stages are identified for unretrograded films by fitting degradation data using first-order kinetics. Starch films containing larger molecules were degraded faster, but the rate coefficient was independent of the granule size. Retrograded films were degraded much slower than unretrograded ones, with a similar rate coefficient to that in the second stage of unretrograded films. Although initially the smaller molecules or the easily accessible starch chains on the amorphous film surface were degraded faster, the more ordered structure (resistant starch) formed from retrogradation, either before or during enzymatic degradation, strongly inhibits film biodegradation.

Recent studies on the oral processing of hard and soft foods are presented with consideration for the underlying physics involved during the transformation of food to a semifluid bolus for swallowing. Significant insights are being realised about the temporal aspects of the dominant processes of comminution, agglomeration, hydration and dilution, and connections to the dominant textural properties are emerging. The field is still challenged by inter-individual differences in oral physiology, but in vitro approaches to characterise the evolution of the food bolus have the potential to provide structure-property-oral processing relationships. Integrated approaches and development of techniques to measure the in-use physics of oral processing are critical for advanced food structure design.

The effects of molecular and crystalline structures on the tensile mechanical properties of thermoplastic starch (TPS) films from waxy, normal, and high-amylose maize were investigated. Starch structural variations were obtained through extrusion and hydrothermal treatment (HTT). The molecular and crystalline structures were characterized using size-exclusion chromatography and X-ray diffractometry, respectively. TPS from high-amylose maize showed higher elongation at break and tensile strength than those from normal maize and waxy maize starches when processed with 40% plasticizer. Within the same amylose content, the mechanical properties were not affected by amylopectin molecular size or the crystallinity of TPS prior to HTT. This lack of correlation between the molecular size, crystallinity and mechanical properties may be due to the dominant effect of the plasticizer on the mechanical properties. Further crystallization of normal maize TPS by HTT increased the tensile strength and Young's modulus, while decreasing the elongation at break. The results suggest that the crystallinity from the remaining ungelatinized starch granules has less significant effect on the mechanical properties than that resulting from starch recrystallization, possibly due to a stronger network from leached-out amylose surrounding the remaining starch granules.

The objective of the present study is to understand the changes in starch structures during digestion and the structures contributing to slow digestion properties. The molecular, crystalline, and granular structures of native waxy maize, normal maize, high-amylose maize, and normal potato starch granules were monitored using SEC, XRD, DSC, and SEM. The amylose and amylopectin molecules of all four starches were hydrolyzed to smaller dextrins, with some having linear molecular structure. Neither the A- nor B-type crystallinity was resistant to enzyme hydrolysis. Starch crystallites with melting temperature above 120°C appeared in waxy and normal maize starches after digestion, suggesting that the linear dextrins retrograded into thermally stable crystalline structure. These crystallites were also observed for high-amylose maize starch before and after digestion, contributing to its low enzyme digestibility. On the contrary, the enzyme-resistant granular structure of native normal potato starch was responsible for its low susceptibility to enzyme hydrolysis.

The relationships were determined between molecular properties of amylopectin, a hyperbranched glucose polymer and the major component of starch, and higher-level structures in native starch (double helices, crystallinity and crystalline-amorphous lamellae). Parameters from NMR, differential scanning calorimetry, and size exclusion chromatography of β-limit dextrins of a series of waxy starches, together with literature data, gave information on relationships between the structure of the interior of the amylopectin molecule and crystallinity. The structure of internal B chains (those with one or more branches) of amylopectin influences both crystalline properties and crystallinity. More B chains produce larger crystalline-amorphous lamellae, probably by expanding the amorphous lamellae, while larger B chains increase the ability of annealing to increase order through greater mobility for the chains to rearrange at higher temperatures. This study brings into question the common assumption that A chains (unbranched chains) are necessarily smaller than B chains.

Glycogen is a hyperbranched glucose polymer comprised of glycogen beta particles, which can also form much larger composite alpha particles. The recent discovery using size-exclusion chromatography (SEC) that fewer, smaller, alpha particles are found in diabetic-mouse liver compared to healthy mice highlights the need to achieve greater accuracy in the size separation methods used to analyze alpha and beta particles. While past studies have used dimethyl sulfoxide as the SEC eluent to analyze the molecular size and structure of native glycogen, an aqueous eluent has not been rigorously tested and compared with dimethyl sulfoxide. The conditions for SEC of pig-liver glycogen, phytoglycogen and oyster glycogen were optimized by comparing two different eluents, aqueous 50 mM NH4NO3/0.02% NaN3 and dimethyl sulfoxide/0.5% LiBr, run through different column materials and pore sizes at various flow rates. The aqueous system gave distinct size separation of alpha- and beta-particle peaks, allowing for a more detailed and quantitative analysis and comparison between liver glycogen samples. This greater resolution has also revealed key differences between the structure of liver glycogen and phytoglycogen. (C) 2014 Elsevier B.V. All rights reserved.

ABSTRACT A survey is given of methods to characterize the lowest three levels of starch structural features: individual chains, branched molecules, and the arrangement of branched molecules in a sample (e.g., crystalline and amorphous lamellae of starch granules in grain). The survey also covers ways of treating the results so as to understand starch structure–property correlations: for example, the structural characteristics that control the rate of digestion of a starch‐containing food. A number of studies are then examined not only to show how these techniques have been used to discover correlations between these structural characteristics and properties of importance but also to deduce reasonable causal explanations for the correlations. An overview of problems that have not yet been solved in each of these starch structural levels is also given. The applications of these characterization methods have considerable potential as tools to choose and process native starches with improved functional properties for human food, animal feed, and industrial uses, including biomaterials.

Starch is the primary mechanism of energy storage in plants, is the single most important source of human food energy and is commonly used as an animal feed. It also has many significant industrial uses in adhesives, packaging materials, pharmaceutical excipients and in the production of textiles and papers. Due to its ubiquity, both as a food and as a food additive, starch structure has been examined in relation to its physical and nutritional properties extensively. There has also been significant success in understanding the biochemical/biosynthetic pathways of aspects of its production and how these affect individual starch structures. The various structural features of starch can be divided into several structural levels, the first four of which are most relevant to this research. Level 1 starch structure is the chain length distribution of starch. Level 2 structure relates to the whole individual molecule, such as whole molecule size and branching pattern. Level 3 structure is the aggregated structures of the molecules such as double helices, crystallites and crystalline-amorphous lamellae. Level 4 starch structures relate to the compartmentalisation of the granule into the hilum and semi-crystalline and amorphous growth rings. This project aims to increase understanding of the influence of the molecular structures (levels 1 and 2) of starch upon the larger scale aggregated structures (level 3) that are present in native starch. The crystalline structure as well as the crystalline-amorphous (C-A) lamellae are known to be produced by the amylopectin molecule while the amylose molecules modifies the size and stability of these structures. Thus, waxy starches (those without amylose) can be used to explore the influence of molecular properties of amylopectin on native starch structure. These results can be used to give an indication about which native starch structures are influenced by the underlying molecular structures and which are mediated by biological changes during synthesis that do not affect the molecular structure. The chain length distribution (CLD) of the amylopectin is observed via debranching followed by size characterization, and parameterised by two different techniques to describe the changes in the branch pattern of the different waxy starches. One technique is the empirically based division iii of chains, the other is based upon biosynthetic modelling. Enzymatic techniques are used to probe the assembly of the branches that produce the whole amylopectin molecule. The enzymes degrade the exterior starch chains allowing the observation of the core of the amylopectin molecule which contains all of the branching. These molecular parameters are then to be compared to the aggregated native structures of starch which are most likely to be related to the molecular structure parameters. The first of these aggregated structures are the crystalline properties of the starches, with an observation of the proportion of crystallinity, the proportion of double helices which make up these crystallites as well as the thermal stability of both the double helices and crystallites. The majority of the eleven waxy starches used, which are from a variety of botanical sources, are A-type starches with a single B-type starch which is used to observe whether B-type starches follow the same trends as A-type starches. The results showed that there was a strong correlation between the molecular parameters of amylopectin, the aggregated starch parameters and the crystalline-amorphous lamellae of native starch. The amylopectin molecule chains that were branched were more likely to be the shoulder length chains in the CLD; increases in these branched shoulder length chains increased the size of the C-A lamellae. No other branch parameters of amylopectin correlated with the CLD of the amylopectin. This indicates that the commonly held belief, that A-chains are more likely to have a lower degree of polymerisation (DP) than B-chains, is questionable. The increase in lamellar size was linked to an increase in the amorphous region of the lamellae which contains the majority of the branch points. The crystalline region of the lamellae increased in size with an increase in the number of longer chains in the first, approximately linear, region of the CLD. The number of longer chains in the linear region increases the likelihood that the starch may produce longer helices, which leads to an increase the crystalline region of the lamellae. Increasing proportions of DP 13-24 and DP 25-36 chains were observed to correlate with an increase in the size of the lamellae while the DP 6-12 chains correlated with a decrease. The DP 13-24 and DP 25-36 chains are likely related to the approximately linear crystalline regions, as iv above, while the DP 6-12 chains decrease the lamellar size by making the production of longer helices unlikely. An increase in the degree of branching of starch was linked to an increase in the number of crystalline defects within starch that is removed with annealing. This was related to the smaller size of the internal chains of the amylopectin molecule which decrease the mobility of the helices during synthesis preventing their correct alignment, which is ameliorated by the annealing process. Speculation about the biosynthesis of starch in light of these discoveries is given with a focus upon starch branching enzyme 1 and the role of the rate of starch synthesis. Starch branching enzyme 1 seems to be the enzyme that specifically produces the shoulder length CLD chains. This results in an increase in the proportion of the B-chains and the placement of these chains in the amorphous lamellar region. There is an apparent lack of difference in the amylopectin molecules in different areas of the granule. The role of the changing rate of starch synthesis in the production of the amorphous and semi-crystalline growth rings is suggested as a reason for the similarity in molecular structure despite the large differences in granular structure.

Improving starch-containing materials, whether food, animal feed, high-tech biomaterials, or engineering plastics, is best done by understanding how biosynthetic processes and any subsequent processing control starch structure, and how this structure controls functional properties. Starch structural characterization is central to this. This review examines how information on the three basic levels of the complex multi-scale structure of starch – individual chains, the branching structure of isolated molecules, and the way these molecules form various crystalline and amorphous arrangements – can be obtained from experiment. The techniques include fluorophore-assisted carbohydrate electrophoresis, multiple-detector size-exclusion chromatography, and various scattering techniques (light, X-ray, and neutron). Some examples are also given to show how these data provide mechanistic insight into how biosynthetic processes control the structure and how the various structural levels control functional properties.

Chain (branch) length distributions (CLD) from size-exclusion chromatography of a series of waxy starches were parametrized using both an empirical and a biosynthesis-based method and correlated with their crystalline-amorphous lamellar properties obtained from X-ray scattering. Correlations were best seen with the biosynthesis-based parametrization. This showed for the first time that the following links between the CLD and lamellar parameters, the average interlamellar repeat distance and the distribution of these distances, were decreased by an increase in the proportion of very short branches and were increased by an increase in the proportion of intermediate and longer chains; further, the shoulder and linear sections of the CLD were found to affect the lamellar repeat distance and distribution. These effects are rationalized in terms of branch-length effects on the production of crystallites and the presence of portions of longer branches in the amorphous regions.