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The physicochemical properties of jackfruit seed starch (JSS) were investigated and compared with rice (RS) and potato (PS) starch. The amylose content of JSS (25%) was similar to PS (27%) but higher than RS (17%). The small granules of JSS (7.9 μm) was comparable to RS (9.7 μm), and both starches had A-type crystallinity. In contrast, PS had larger granules (43.4 μm) and displayed B-type crystallinity. The DSC results showed that peak gelatinization temperature of JSS (85.0°C) was significantly higher than RS (66.9°C) and PS (63.7°C), corresponding to higher pasting temperatures and lower swelling power at lower temperatures. There was no significant difference in stability between the starch gels after four freeze-thaw cycles. Formation of JSS gels with significantly higher hardness, chewiness and elastic modulus (G′), but lower fracturability demonstrated JSS ability to form strong gels. This would be beneficial for food applications requiring gelation with firm and elastic textural attributes.

Type 2 diabetes is increasingly prevalent in Asia, which can be attributed to a carbohydrate-rich diet, consisting of foods in the form of grains, for example, rice, or a food product made from flours or isolated starch, for example, noodles. Carbohydrates become a health issue when they are digested and absorbed rapidly (high glycemic index), and more so when they are consumed in large quantities (high glycemic load). The principal strategies of glycemic control should thus aim to reduce the amount of carbohydrate available for digestion, reduce the rate of digestion of the food, reduce the rate of glucose absorption, and increase the rate of glucose removal from blood. From a food perspective, the composition and structure of the food can be modified to reduce the amount of carbohydrates or alter starch digestibility and glucose absorption rates via using different food ingredients and processing methods. From a human perspective, eating behavior and food choices surrounding a meal can also affect glycemic response. This review therefore identifies actionable strategies and opportunities across foods and meals that can be considered by food manufacturers or consumers. They are (a) using alternative ingredients, (b) adding functional ingredients, and (c) changing processing methods and parameters for foods, and optimizing (a) eating behavior, (b) preloading or co-ingestion of other macronutrients, and (c) meal sequence and history. The effectiveness of a strategy would depend on consumer acceptance, compatibility of the strategy with an existing food product, and whether it is economically or technologically feasible. A combination of two or more strategies is recommended for greater effectiveness and flexibility.

A water-soluble polysaccharide (type II arabinogalactan-protein) extracted from the gum exudate of the native New Zealand puka tree (Meryta sinclairii), was characterised for its molecular, rheological and physicochemical properties. In 0.1 M NaCl, the weight average molecular weight (Mw) of puka gum is 5.9 × 106 Da with an RMS radius of 56 nm and z-average hydrodynamic radius of 79 nm. The intrinsic viscosity of the polysaccharide is 57 ml/g with a coil overlap concentration 15% w/w. Together, the shape factor, p, of 0.70 (exponent of RMS radius vs. hydrodynamic radius), Smidsrod-Haug’s stiffness parameter B of 0.031 and Mark-Houwink exponent α of 0.375 indicate that the polysaccharide adopts a spherical conformation in solution, similar to gum arabic. The pKa is 1.8. The polysaccharide exhibits a Newtonian to shear-thinning behaviour from 0.2 to 25% w/w. Viscosity of the polysaccharide (1 s−1) decreases with decreasing concentration, increasing temperature, ionic strength, and at acidic pH.

Intragastric gelation is a mechanism whereby a consumed liquid food gels under the acidic gastric condition. It was hypothesised that intragastric gelation would result in satiety due to delayed gastric emptying. Three treatment beverages that is soya protein isolate (SPI) with λ-carrageenan (SPI-LC; high viscosity, gelling), guar gum (SPI-GG; high viscosity) and no polysaccharide (SPI; low viscosity) were given to twenty participants in a randomised 3 × 3 double-blind within-subject crossover design trial and asked to rate their hunger and fullness scores (visual analogue scale; VAS) before and up to 60 min after consumption of the beverage. Results show that there were no significant effects on hunger, fullness and energy intake after consuming the SPI-LC (gelling) beverage compared to the SPI-GG beverage, but did evoke weak satiety signals up to 20 min after consumption when compared to the control (low-viscosity) SPI beverage. Therefore, intragastric gelation does not result in satiety in this study.

Growing health concerns have increased interest in reducing the consumption of added sugars, which can be achieved by substituting or replacing sugar with sweeteners to maintain sensory intensity and quality. The growing availability of sweeteners has increased the complexity of the perceptual landscape as sweeteners differ in the qualitative, intensity, and temporal properties. A sweetener that can match the perceptual properties of sucrose in different food matrices is likely to have broad applications. In complex foods, sweetness is influenced by the taste interactions with the existing tastants and possible matrix effects that influence release and perception of sweetness. The current study compared the taste properties of three food matrices (black tea, chocolate milk, and natural yogurt) sweetened by sucrose to those sweetened using eight different sweeteners (acesulfame-K, aspartame, erythritol, luo han guo (Mogroside), palatinose (iso-maltulose), stevia (Reb-A), sucralose, and sucrose–allulose mixture) using Rate-All-That-Apply. The sensory properties of each sweetener differed across matrices, with sucrose–allulose mixture, aspartame, erythritol, palatinose, and sucralose having the most similar taste to sucrose across all foods. By contrast, acesulfame-K, stevia, and luo han guo had taste profiles that most varied from sucrose, characterized by side tastes such as bitterness, chemical taste, and a low sweetness. Sweeteners differed most from sucrose when presented in natural yogurt compared to tea and chocolate milk. A food's taste properties can suppress sweetness intensity and promote undesirable side tastes. Taken together, these findings highlight the importance of testing sweeteners in complex foods and help identify sweeteners and sweetener combinations that can replicate the sweetness of sucrose and support sugar reduction. Practical Application: Food manufacturers and researchers can refer to the results of the sensory profiles to identify suitable sweeteners substitutes for sucrose in foods with similar taste profiles to those tested. The current article highlights important changes to sweetener sensory properties when presented in different complex foods, and provides an indication of the potential for calorie reduction by substituting sucrose with a range of low or no calorie sweeteners.

We examined the effect of gavage of 4 ml of a viscous shear-thickening polysaccharide solution (15% w/w) extracted from the fronds of the mamaku tree fern (Cythea medullaris) in reducing appetite and delaying gastric emptying in twenty six Sprague Dawley rats. After two weeks habituation to a pelleted chow, the rats were gavaged on alternate days with either the mamaku extract or with the same volume of deionised water for a total of five times over a period of two weeks. The body mass and food intake of each rat were determined daily and the weights of their stomach contents determined on euthanasia two hours after the final gavage. The rats gavaged with the mamaku gum consumed significantly lower quantities of chow on the day of gavage. The weights of the stomach contents of rats two hours after gavage with mamaku extract were significantly greater than those following gavage with water. The failure of the rats dosed with mamaku to lose body weight likely resulted from the overall adverse effect of gavage on food intake, the limited numbers of doses of the gum and the rebound hyperphagia on days when the rats were not gavaged. Together the results indicate that gavage with mamaku gum delayed gastric emptying with respect to that of rats dosed with water and supressed appetite for 12-24 hours after dosage.

An increase in consumer awareness around the negative health impacts of consuming excess added sugars has led to a rise in the replacement of sucrose in foods and beverages. This replacement is often through the use of low or no calorie sweeteners to reduce total calories while maintaining sweetness and palatability. There are a wide variety of sweeteners with diverse physical and caloric compositions which can be used at concentrations estimated to be equi-sweet to sucrose in food products. However, many of the available sweeteners are known to differ in their temporal profiles and may have other side and aftertastes alongside sweetness that need to be considered when comparing their suitability as potential sucrose substitutes. The objective of the current study was to profile and compare the temporal sweetness and qualitative differences of 15 sweeteners to sucrose across nutritive saccharide (sucrose, dextrose, fructose, allulose (D-psicose), palatinose (isomaltulose), sucrose-allulose mixture), nutritive polyol (maltitol, erythritol, mannitol, xylitol, sorbitol) and non-nutritive (acesulfame-k, aspartame, sucralose, stevia (rebaudioside-A or rebA), luo han guo (monk fruit extract or mogroside)) groups, at equi-sweet intensity to 10% w/v sucrose based on a previous psychophysical dose-response study. Using the Temporal Check-all-that-Apply (TCATA) method, 20 participants evaluated a set of 17 sweetener samples (including a sucrose duplicate) in triplicates across three 1-h sessions for the occurrence of six attributes (sweetness, bitterness, metallic taste, chemical taste, honey taste and mouth-drying) over a 60 s period. Sucrose was characterised by a rapid sweetness onset (within first 10 s) to peak citation, and subsequent decay of sweetness with minimal side tastes noted. Acesulfame-K, stevia (rebA) and luo han guo had prominent and long-lasting citations of the undesirable bitter, metallic and chemical side tastes and significantly lower sweetness citations. Allulose, erythritol, sorbitol, aspartame and sucralose were perceived to have bitter, metallic and chemical side tastes, but retained a largely sweet taste profile, with longer residual sweetness for aspartame and sucralose. Nutritive sweeteners dextrose, fructose, maltitol, mannitol, sucrose-allulose mixture, palatinose and xylitol had the most similar temporal and qualitative taste profiles when compared to sucrose, in terms of their sweetness onset, peak sweetness citations, sweetness decay, and side taste profiles.

Wheat noodles with added native or denatured pea-protein isolate were characterised for their starch-protein interaction, degree of starch gelatinisation, starch digestibility, textural and sensory properties using light microscopy, differential scanning calorimetry (DSC), in vitro digestion, textural profile analysis (TPA) and descriptive analysis respectively. It was hypothesised that denatured proteins with an unfolded structure, would have greater interaction with starch, thereby reducing the extent of gelatinisation and subsequent glucose release compared to native proteins. Results showed that the addition of denatured pea protein to a wheat noodle matrix produced a reduction in in vitro glucose release, which was supported by a lower degree of gelatinisation and greater binding of protein to the starch matrix visually. Addition of native protein to the noodles had less impact on degree of gelatinisation and glucose release. Addition of both proteins had a negligible effect on product texture and sensory perceptual properties.

Faster eating rates have previously been associated with higher ad libitum energy intakes, and several studies have manipulated eating rates and intake by changing food textures. Food texture based changes to slow eating rates can produce reductions in energy intake without affecting post-meal satisfaction or re-bound hunger. However, an understanding of how specific food textures and instrumental texture properties influence oral processing behaviour remains limited. The current study sought to establish relationships between objective measures of oral processing behaviour (i.e. number of bites, average bite size, total chews, chews per bite, oro-sensory exposure time and eating rate) and instrumental measures of a food texture including hardness, adhesiveness, springiness, cohesiveness, chewiness, resilience and modulus. Across two studies, behavioural coding analysis was completed on video-recordings of participants consuming fixed portions of a wide range of different solid foods (n = 59) to derive objective measures of oral processing behaviours. These measures were correlated with instrumental Textural Profile Analysis (TPA) for the same set of foods. Significant correlations (p < 0.05) were found between oral processing parameters and texture properties (i.e. springiness, cohesiveness, chewiness and resilience). No significant correlations were found between hardness and modulus and oral processing parameters. Protein content of the food was associated with springiness and chewiness, which may help to further reduce eating rates. In terms of the ‘breakdown path model', hardness and modulus might represent degree of initial food structure while springiness, cohesiveness, chewiness and resilience seem to determine how fast the degree of structure is reduced to the swallowing plane. Water content and adhesiveness were associated with level of lubrication that is required before reaching the swallowing plane. The current study highlights opportunities to understand eating rate (g min−1) through the breakdown path model and the potential for specific features of a foods texture to influence rate and extent of energy intake. The correlation between instrumental texture properties and oral processing patterns provides guidance on the parameters that are likely to produce ‘faster' and ‘slower' versions of foods, and suggests how texture modifications could be applied to moderate eating rate and energy intake within meals.

The shear-thickening rheological behaviour (between 5 and 20s(-1)) of a 5% (w/w) viscoelastic gum extracted from the fronds of the native New Zealand black tree fern or mamaku in Māori was further explored by manipulating the salt content. The freeze-dried mamaku gum contained a high mineral content and sugars which upon removal via dialysis, resulted in the loss of shear thickening. However, this loss was reversible by the addition of salts to the dialysed dispersion. The mechanism of shear-thickening behaviour was therefore hypothesised to be due to shear-induced transition of intra- to intermolecular hydrogen bonding, promoted by the screening effect of cations. Mono-, di- and trivalent salts, i.e. Na(+), K(+), N(CH3)4(+), Ca(2+), Mg(2+), Al(3+) and La(3+) at concentrations between 0.001 and 1.0M were tested to support the hypothesis as well as to demonstrate the sensitivity of the biopolymer to cation valency and concentrations. The cation valency and concentration were crucial factors in determining: (i) zero-shear viscosity, (ii) critical shear rate, γ˙c (or shear rate at the onset of shear-thickening) and (iii) the extent of shear-thickening of the solution. For mono- and divalent cations these parameters were similar at equivalent ionic strengths and fairly independent of the cation type. Trivalent cations (La(3+)) however caused precipitation of the gum in the concentration range of 0.005-0.05 M but clear dispersions were obtained above 0.05 M.

A shear-thickening polysaccharide extracted from the New Zealand black tree fern was characterized for its time-dependent rheology and the effects of shear-history. The material exhibited antithixotropic behavior at shear rates between 4 and 10 s−1. The parallel growth of normal stresses with time at these shear rates indicated the development of an elastic network under shear. The formation of association structures is proposed to take place via cooperative zipping of stretched chains where associative groups are exposed only on shearing. Hysteresis effects were also observed at shear rates between 4 and 10 s−1. This was probably caused by rapid structure formation at these shear rates, which cannot be easily disrupted at subsequent lower shear rates (

Puka gum (PG), a high molecular weight arabinogalactan-protein (AGP) polysaccharide extracted from the native New Zealand Meryta sinclarii tree formed electrostatic complexes with whey protein isolate (WPI) under specific conditions. The PG and WPI mixtures were slowly acidified using glucono-delta-lactone (GDL), and the progressive change from soluble polymer solution to soluble complexes and to the formation of insoluble complexes (through the association of soluble complexes) were monitored using visual examination, turbidity, particle size (dynamic light scattering) and zeta-potential measurements at total biopolymer concentration C p = 0.3% w/w, protein:polysaccharide ratio Pr:Ps = 2:1, [GDL] = 0.14% w/w, and T = 20 °C. This process was characterised by identifying the phase boundaries, pH c (pH = 5.7 at which soluble complexes of WP and PG were formed) and pH Φ (pH = 4.7 at which complexes associated to form coacervates). The coacervates formed under these conditions appeared as a sticky, viscoelastic and highly extensible material. The effect of ionic strength (0–100 mM NaCl) on complex formation was also studied and a pH c /pH Φ -ionic strength phase diagram was constructed. Coacervation was fully suppressed at ionic strengths above 60 mM NaCl. Rheological measurements of the insoluble coacervate phase at different final coacervation pH (Pr:Ps = 2:1 and 4:1; C p = 3.0% w/w) showed highest complex modulus G * at approx. pH 3.6 for both Pr:Ps = 2:1 and 4:1, i.e. electrical equivalence pH (EEP), where electrostatic interactions are strongest and the overall charge on the insoluble complex is neutral.

A shear-thickening water-soluble polysaccharide was purified from mucilage extracted from the fronds of the New Zealand black tree fern ( Cyathea medullaris or ‘mamaku’ in Māori) and its structure characterised. Constituent sugar analysis by three complementary methods, combined with linkage analysis (of carboxyl reduced samples) and 1 H and 13 C nuclear magnetic resonance spectroscopy (NMR) revealed a glucuronomannan comprising a backbone of 4-linked methylesterified glucopyranosyl uronic acid and 2-linked mannopyranosyl residues, branched at O-3 of 45% and at both O-3 and O-4 of 53% of the mannopyranosyl residues with side chains likely comprising terminal xylopyranosyl, terminal galactopyranosyl, non-methylesterified terminal glucopyranosyl uronic acid and 3-linked glucopyranosyl uronic acid residues. The weight-average molecular weight of the purified polysaccharide was ∼1.9 × 10 6 Da as determined by size-exclusion chromatography coupled with multi-angle laser light scattering (SEC–MALLS). The distinctive rheological properties of this polysaccharide are discussed in relation to its structure.

Wheat noodles are a staple commonly consumed in Asia, but high intakes have been associated with type 2 diabetes due to its rapid starch digestibility. We hypothesised that protein network-binding via transglutaminase (TG) would form a stronger barrier encapsulating the starch granules to limit enzymatic access and digestion. The amount of glucose release decreased significantly with increasing TG concentration, with a reduction of approximately 16% with 2% TG after 120 min of digestion. The slower rate of glucose release during the first 60 min of digestion for 2% compared to 0% TG suggested impeded first stage enzymatic access rather than second stage starch hydrolysis into glucose. Upon increasing the TG concentration, confocal microscopy revealed a denser protein network with increased connectivity, supported by a decrease in protein solubility and gelatinisation enthalpy, and increased firmness and work of shear. Therefore, transglutaminase can potentially be used to reduce starch digestibility in wheat noodles via protein network-binding.

The aim of this investigation was to characterize and explain the rheological behaviour observed for mixed solutions of maltodextrin and galactomannans. When 1% w/w guar gum was mixed with 3% w/w low DE maltodextrin (DE 1 or DE 2), the viscosity at low shear rates (~0.1 to 10 s(-1)) decreased by approximately a decade, and exhibited Newtonian behaviour. At intermediate shear rates (~10 to 50 s(-1)), shear thickening was observed, followed by shear thinning at higher rates. The magnitude of these effects increased with increasing concentration and increasing molecular weight (i.e. decreasing DE) of maltodextrin. The underlying mechanism was investigated by studying the stability, rheology and microstructure of the mixtures. The reduction in viscosity at low shear rates is attributed to partial segregation of the more viscous component, guar gum, into a dispersed phase; shear thickening can then be explained by phase inversion under shear, giving a dispersed phase rich in maltodextrin surrounded by a continuous matrix consisting predominantly of guar gum.