Increasing agar content improves the sol-gel and mechanical features of starch/agar binary system.

Starch/agar systems are highly potential for versatile applications such as packaging and biomedical materials. Here, how combined factors affect the features of a starch/agar binary system were explored. An increase of starch amylose/amylopectin ratio from 0/100 to 50/50 increased the sol-gel transition temperature and gel hardness of the aqueous starch/agar mixture. An increased agar content (mainly from 30% to 70%) allowed increases in both the tensile strength (reaching 50-60 MPa) and elongation at break of the starch/agar binary films. This phenomenon should be related to the strengthened crystalline structure and the weakened hydrogen bonding between starch chains (reflected by infrared spectroscopy). Furthermore, a higher relative humidity (from 30% to 70%) allowed enhanced chain interactions and probably nanoscale molecular order but weakened the crystalline structure, leading to reduced tensile strength and increased elongation at break. This work could facilitate the design of starch/agar binary systems with improved sol-gel and mechanical performance.

Increasing the pH value during thermal processing suppresses the starch digestion of the resulting starch-protein-lipid complexes.

To date, how the pH conditions of thermal processing tailor the structure and digestibility of resulting starch-based complexes remains largely unclear. Here, indica rice starch (IRS), stearic acid (SA), and a whey protein isolate (WPI) were used as materials. Increasing the pH value from 4 to 8 during thermal processing (pasting) mainly suppressed the starch digestion of starch-WPI-SA complexes rather than starch-SA counterparts. The starch-SA complexes showed moderate structural changes as the pH value rose, and there was less rapidly digestible starch (RDS) only at pH 8. For the starch-WPI-SA complexes, an increased pH value allowed larger nonperiodic structures and more V-type starch crystallites, with almost unchanged short-range orders but apparently collapsed networks at pH 8. Such ternary complexes displayed more resistant starch (RS) as the pH value rose. The ternary sample at pH 8 contained ca. 29.87% of the RS fractions.

Introduction of octenylsuccinate and carboxymethyl onto starch for strong bonding to fiber and easy removal from sized yarn.

Amphipathic starch (AS) with hydrophobic octenylsuccinate (OS) and hydrophilic carboxymethyl (CM) substituents was prepared by the carboxymethylation and octenylsuccinylation of starch for strong bonding to fiber and easy removal from sized yarn. Two series of AS derivatives with differential degrees of substitution (DS) and differential mole percentages of OS to total substituents (Pos) were examined to reveal the effects of Pos and DS values on bonding of the starch to cotton and polyester fibers. It was found that the amphipathic modification was able to significantly increase bonding strength of the starch. Combination of the CM and OS substituents could increase the bonding strength more than each one alone. Furthermore, desizing trial proved that the AS was desizable by either enzyme or oxidant desizing. Starch octenylsuccinylation and carboxymethylation was a good way for corn starch to achieve strong bonding to fibers and easy removal from sized yarns.

Effect of annealing and heat-moisture pretreatments on the oil absorption of normal maize starch during frying.

The impacts of two hydrothermal pretreatments, annealing (ANN) and heat moisture treatment (HMT), on oil-absorption by normal maize starch (NMS) during frying were investigated using low-field nuclear magnetic resonance (LF-NMR). The structural organizations of the fried samples were also evaluated using SEM, XRD, ATR-FTIR, and DSC, respectively. Both hydrothermal pretreatments significantly reduced the total oil content in the starch after frying, with the magnitude of the effect depending on the treatment conditions used. SEM showed that the pretreated fried starch granules preserved more of their original morphology. XRD, FTIR, and DSC showed that both pretreatments preserved more of the short-range double helices and long-range organizations within the orthorhombic crystalline structure for NMS during frying. The promoting effect of ANN/HMT on the interactions of starch molecules and the rearrangement of double helices were hypothesized to be responsible for the increased thermal stability of starch granules in the present work. As a result, fried starch pretreated by ANN/HMT were more organized and more compact than fried NMS, thus inhibiting oil absorption during frying.

Analysis of porous structure of potato starch granules by low-field NMR cryoporometry and AFM.

Pore size distribution is a crucial structural element affecting the adsorption and diffusion of reagents and enzymes within starch granules. An accurate and credible method of determining the pore size distribution of starch granules especially for smooth ones is therefore required. In this work, low-field NMR cryoporometry (LF-NMRC) was applied to analyze the pore structure of potato starch (PS). The reliability of the LF-NMRC method is verified by comparing with the traditional method, i.e. the low temperature nitrogen adsorption (LT-NA). Both LF-NMRC and LT-NA could characterize the PS pore structure in mesoporous range. However, LF-NMRC has superiority over LT-NA in terms of the distinguishment and determination of pore size distribution approaching to the micropores, gives more accurate and reliable results than LT-NA does. Structural evidences from scanning electron microscope (SEM) and atomic force microscope (AFM) further indicated that the new proposed method is a non-destructive method that does not induce structural changes during sample preparation.

Opportunities for fraudsters: When would profitable milk adulterations go unnoticed by common, standardized FTIR measurements?

Milk is regarded as one of the top food products susceptible to adulteration where its valuable components are specifically identified as high-risk indicators for milk fraud. The current study explores the impact of common milk adulterants on the apparent compositional parameters of milk from the Dutch market as measured by standardized Fourier transform infrared (FTIR) spectroscopy. More precisely, it examines the detectability of these adulterants at various concentration levels using the compositional parameters individually, in a univariate manner, and together in a multivariate approach. In this study we used measured boundaries but also more practical variance-adjusted boundaries to set thresholds for detection of adulteration. The potential economic impact of these adulterations under a milk payment scheme is also evaluated. Twenty-four substances were used to produce various categories of milk adulterations, each at four concentration levels. These substances comprised five protein-rich adulterants, five nitrogen-based adulterants, seven carbohydrate-based adulterants, six preservatives and water, resulting in a set of 360 samples to be analysed. The results showed that the addition of protein-rich adulterants, as well as dicyandiamide and melamine, increased the apparent protein content, while the addition of carbohydrate-based adulterants, whey protein isolate, and skimmed milk powder, increased the apparent lactose content. When considering the compositional parameters univariately, especially protein- and nitrogen-based adulterants did not raise a flag of unusual apparent concentrations at lower concentration levels. Addition of preservatives also went unnoticed. The multivariate approach did not improve the level of detection. Regarding the potential profit of milk adulteration, whey protein and corn starch seem particularly interesting. Combining the artificial inflation of valuable components, the resulting potential profit, and the gaps in detection, it appears that the whey protein isolates deserve particular attention when thinking like a criminal.

Effect of pullulan on oil absorption and structural organization of native maize starch during frying.

The oil-absorption behavior of native maize starch (NMS) during frying was investigated in the presence or absence of pullulan (PUL) using a LF-NMR method. The morphology, long-range order, short-range order, and thermal properties of fried NMS-PUL mixtures were further evaluated using SEM, XRD, ATR-FTIR, and DSC, respectively. Pullulan addition significantly reduced the oil content of the fried starch samples: 0.395, 0.310, 0.274, and 0.257 g/g in NMS with addition of 0, 1, 3, and 5% PUL, respectively (p < 0.05). SEM analysis showed that the intact granular morphology of the starch granules was preserved upon addition of pullulan. The XRD, FTIR, and DSC results showed that pullulan protected both the short-range double helices and long-range crystalline structure of the granules during frying. As a result, fried NMS-PUL mixtures were denser than fried NMS, thus inhibiting oil absorption during frying. These results may have important implications for creating healthier reduced-fat fried food products.

How rheological behaviors of concentrated starch affect graft copolymerization of acrylamide and resultant hydrogel.

Corn starches with different amylose/amylopectin ratios were used to explore the effect of rheological behaviors of concentrated system on the graft copolymerization of acrylamide and resultant hydrogels, which sheds a light on their reactive extrusion process. The viscoelastic moduli of starch melts increased with increasing amylose content (AC), leading to a decreased extent of micro-mixing detected by a reduced rheokinetic rate. With increasing AC, the graft efficiency was decreased but with almost similar monomer conversion (about 87.5%) and nearly equivalent graft content. XRD and SAXS spectra revealed that the extent of retrogradation of the starches were increased and two-phase separation was enhanced for hydrogels with increasing AC. Interestingly, microscopic analysis showed the superabsorbent hydrogel from the starch with AC of 50% exhibited a gridding membrane porous structure, resulting in a higher water absorbent capacity of 550 g/g. This was attributed to the moderate crosslinking and the slightly greater graft content.

Digestibility and structures of vinasse starches with different types of raw rice and fermented leaven.

In consideration of health benefits, more digestible vinasses were investigated, which are associated with the use of different raw cereals and fermented leavens. In an in vitro digestibility test, milled long-grain glutinous rice vinasse with Taibai rice leaven showed a slow glucose-controlled release potential, which contained 37.08% slowly digestible starch, after complete vinasse consumption. The crystalline structure, thermal properties and morphology of vinasse starches were analysed. The relatively long amylopectin chains, which originated from the starch structure present in raw rice and the higher glucoamylase activity of the fermented leaven, partly explained the slower digestion of vinasse. By the optimization of the type of fermented leaven used and the starch structure of the raw rice in fermentation, the rate of vinasse starch digestion could be controlled, resulting in improved nutritional value. The results of this study are important for designing healthy vinasse products by controlling starch structures and digestion rates.

Effect of dietary fibers on the structure and digestibility of fried potato starch: A comparison of pullulan and pectin.

The granular morphology, long-range and short-range ordered structures of fried potato starch were measured in the absence and presence of the dietary fibers. The in vitro digestibility of the fried starchy samples was also quantified using the Englyst method with logarithm-of-slope (LOS) analysis. After frying, the starch granules disintegrated, their internal crystalline structure disappeared, and the quantity of double helices present decreased. As a result of these changes, the fried starch was digested rapidly. Addition of pullulan or pectin to the samples prior to frying, reduced the structural changes observed in the starch granules during frying. Consequently, the fractions of slowly digestible and resistant starch (SDS and RS) increased significantly in the presence of the dietary fibers. These effects were attributed to the ability of the dietary fibers to sequester some of the water, thereby reducing starch granule structural changes, as well as due to their ability to coat the starch granules and interfere with the starch digestion process.

Multi-scale structure and pasting/digestion features of yam bean tuber starches.

This work discloses the multi-scale structure and pasting/digestion behaviors of yam bean tuber starches (YB-GD and YB-SC). Compared to potato starch, YB starches exhibited varied pasting/digestion features that were understood from a multi-scale structural view. Especially, YB starches showed relatively polydisperse lamellae, less perfect crystallites, and fewer amylose molecules. These features should reduce the bulk density of starch chain packing, and could facilitate the water or enzyme diffusion in starch matrixes. Consistently, not only was starch's resistance to hydrothermal effects weakened (shown by reduced pasting temperature), but also the enzyme absorption to starch chains and the subsequent hydrolysis events were accelerated. Furthermore, YB starch molecules had more short chains, which played roles in reducing the paste viscosity along with the reduced granule size and in enhancing the paste stabilities during heating and cooling. Also, those molecular features tended to speed up the enzyme diffusion and digestion events.

Effects of stearic acid and irradiation alone and in combination on properties of amylose-lipid nanomaterial from high amylose maize starch.

This study determines the effects of stearic acid and gamma irradiation, alone and in combination, on properties of amylose-lipid nanomaterials from pasted high amylose maize starch (HAMS) with and without alpha amylase hydrolysis. HAMS was incorporated with stearic acid (0, 1.5% and 5%, w/w), irradiated at 0, 30 and 60 kGy and pasted under pressure in a rheometer. Isolated materials after thermostable alpha amylase or hot water washing were freeze-dried and characterised using differential scanning calorimetry (DSC), X-ray diffraction (XRD), Atomic Force Microscopy (AFM) and Transmission Electron Microscopy (TEM). The isolated materials contain amylose-lipid complexes (ALCs) as determined by DSC and XRD. Pasting of gamma irradiated HAMS produced type I ALCs, whereas that for un-irradiated HAMS produced type II ALCs. The ALCs occurred at nanoscale with sizes ranging from 10 to 110 nm as observed with AFM and TEM. Tailor-made ALCs nanomaterials can be produced from HAMS (with and without added stearic acid).

Impact of amylose content on structural changes and oil absorption of fried maize starches.

The absorption of oil during frying has important implications for food quality, cost, and nutrition. Maize starches with low (WMS), intermediate (NMS), and high amylose (HAMS) contents were therefore heated in oil to mimic the frying process, and the impact of amylose content on the hierarchical structures and oil absorption of the fried starches was evaluated. Amylose affected the oil absorption by interfering with the structural evolution of the starch or by directly interacting with the lipids during frying. At low moisture level (20%), the granular state was preserved after frying and so the size and porosity of the granules played a dominant role in the oil absorption process, explaining why the highest oil absorption occurred in WMS. At 40% moisture content, NMS absorbed the most oil because of its granular morphology and lower crystallinity. At 60% moisture content, HAMS absorbed more oil than NMS, because more amylose molecules in HAMS provided more hydrophobic helical cavities available for lipids.

Low cost in situ digital image method, based on spot testing and smartphone images, for determination of ascorbic acid in Brazilian Amazon native and exotic fruits.

In this work, we propose a method that employed a smartphone to capture images obtained from a colorimetric spot test to determine ascorbic acid (AA) in Brazilian Amazon native and exotic fruits. The spot test reaction was based on reduction of Fe(III) by AA and further complexation with 1,10-phenanthroline. After optimization, the limit of detection was 8.5 × 10-7 mol L-1. Brazilian Amazon native fruits such as bacuri, cupuaçu, muruci, yellow mombin, as well as others as cashew, mango, orange and passion fruit, were analyzed. In order to determine the accuracy of this method, iodometric titration was used; results were in close agreement with a confidence level of 95% (paired t-test). Moreover, recoveries ranged from 87.1 to 116%. The method is economic, environmentally friendly, and portable, and might useful for small producers and family agriculture businesses unable to afford specialized laboratory analysis in the north region of Brazilian Amazon.

Dispersion of reduced graphene oxide within thermoplastic starch/poly(lactic acid) blends investigated by small-angle X-ray scattering.

Reduced graphene oxide (rGO) was incorporated into plasticized cornstarch (TPS), poly(lactic acid) (PLA) and their blends. Small-angle X-ray scattering (SAXS) was used to investigate rGO dispersion within the materials. For the TPS/PLA blend at 70:30 composition, the incorporation of rGO led to a larger fraction of small-sized rGO sheets, which at 5.0 mass% content developed stable fractal structures and domains of correlated sheets. The formation of fractal structures resulted in substantial enhancements in macroscopic properties. For these hybrids, the electrical conductivity, melt viscosity, storage moduli and biodegradation rates presented enhancements in relation to the neat blend. For the TPS/PLA blend at 30:70 composition, SAXS results indicated the formation of smaller fractions of well-dispersed rGO sheets and of segregated larger rGO sheets. With rGO at 5 mass% content, less expressive increases in electrical conductivity, melt viscosity, storage moduli and biodegradation rates were observed.

A simple and green method for preparation of non-crystalline granular starch through controlled gelatinization.

Non-crystalline granular starch (NCGS) is of considerable interest because of its unique functional properties. In this study, controlled gelatinization combined with sedimentation was used to prepare the NCGS from normal maize starch. The morphology and crystalline state of the NCGS were investigated using optical and electron microscopy, calorimetry, and X-ray diffraction (XRD). These methods showed that starch granules maintained a granule structure up to around 80 °C but they completely dissociated at higher temperatures. The number of the granules that disappeared the birefringence gradually increased with the temperature increase, and completely disappeared at 75 °C. The DSC results indicated that the crystalline structure of amylopectin was totally destroyed when the treating temperature was greater than or equal to 75 °C. The XRD patterns showed that the crystalline structure of native starch was thoroughly disappeared at 75 °C. However, B-type and V-type crystals formed in the samples heated at 80 °C or higher, corresponding to the short-term retrogradation of amylose and the formation of amylose-lipids complexes, respectively.

Starch-zinc complex and its reinforcement effect on starch-based materials.

In this work, we found that ZnCl2 solution can not only be used as a plasticizer for starch but also provide a mechanical reinforcement effect to the resultant starch-based materials. By a one-step compression molding process, well-plasticized starch-based films could be obtained at 120 °C with a 15 wt.% ZnCl2 solution. Both the tensile strength and elongation at break of the films increased with a rise in ZnCl2 concentration, which demonstrates a mechanical reinforcement. This reinforcement could be mainly ascribed to the in-situ formed starch-zinc complexes and the enhanced starch molecular interactions. Moreover, if the processing method was changed into firstly mixing followed by compression molding, the tensile strength increased by more than three folds at no cost of the elongation at break. Regarding this, we propose that shear could further enhance the molecular interactions within the material. However, if the ZnCl2 concentration was too high, the mechanical properties were then reduced irrespective of the processing protocol, which could be due to the weakened molecular interactions by ZnCl2. Thus, we have demonstrated a new, simple method for preparing starch-based composite materials with enhanced mechanical properties, which could be potentially applied to many fields such as packaging, coating and biomedical materials.

Rheokinetics of graft copolymerization of acrylamide in concentrated starch and rheological behaviors and microstructures of reaction products.

A widely recognized challenge in starch chemistry is to manipulate the graft copolymerization onto starch melt by reactive extrusion (REX). To understand the complex in-situ graft copolymerization in highly concentrated systems, we firstly used a mixer to achieve a homogeneous viscous starch melt, and then undertook dynamic rheological measurements to study the rheokinetics of the reaction. The in-situ synthesis also facilitated the characterization of the microstructures of reaction products. The melt mixture could be regarded to be completely micromixed since the rheokinetics was predominated by the reaction kinetics. The rheological characterization revealed that G'of hydrogels followed a linear progression with the crosslinker concentration. Nevertheless, the reaction temperature and initiator content had little influence on the final microstructure of hydrogels, most likely due to the strong chain transfer reaction in the melt. Additionally, high-amylose starches tended to form grafted hydrogels with a high physical crosslinking density.

Starch film-coated microparticles for oral colon-specific drug delivery.

The aim of this study was to prepare and characterize a novel type of starch-coated microparticles (MPs) allowing site-specific delivery of bioactives to the colon. An oral colon-specific controlled-release system was developed in the form of MPs coated with a resistant starch (RS2/RS3) film (RS@MPs) through an aqueous suspension coating process. The RS2 was chosen from a high-amylose cornstarch with 88.5% digestion resistibility. The RS3 was prepared by a high-temperature/pressure (HTP) treatment, with the following of enzymatic debranching, and retrogradation, resulting in a dramatic increase in enzymatic resistance (RS3 content: 76.6%). RS@MPs showed 40.7% of 5-aminosalicylic acid release within 8 h. The in vivo study of fluorescein-loaded RS@MPs indicated the high acidic and enzymatic resistibility of RS@MPs and a restrained release in the upper GIT. Therefore, RS@MPs has revealed to be a high potential system for accurately targeting bioactive compound delivery to the colon.

Effects of dextran with different molecular weights on the quality of wheat sourdough breads.

This research aimed at investigating the effects of different weight-average molecular weights (Mw: T10, T70, T250, T750, T2000) of dextran (α-(1 → 6)-linked linear backbone, α-(1 → 3)-linked branching) on wheat sourdough bread qualities. Texture analyzer showed that dextran contributed to a significant inhibition of bread staling, particularly dextran T2000. Pasting profiles (Rapid visco-analysis) and steady rheological properties (steady shear measurements) of samples indicated that dextran T2000 suppressed the swelling and gelatinization of wheat starch granules and bound a great amount of water, thus retarding the aging process. Dextran T2000 markedly improved the elastic properties of sourdough-containing dough. Wheat sourdough breads containing dextran T10 exhibited unexpected less firm crumb structure. The improvement of bread qualities was a function of the Mw of dextran. Dextran with high Mw values has the potential for improving the quality of wheat sourdough breads, especially extending shelf life.