Cell wall polysaccharides of bush butter (Dacryodes edulis (G Don) HJ Lam) fruit pulp and their evolution during ripening

Cell wall material was isolated as alcohol‐insoluble solids (AIS) from bush butter endocarp tissue at different stages of ripeness. AIS were then extracted with 0.05 M CDTA followed by increasing concentrations of KOH (0.05, 1 and 4 M respectively). The chemical extractions solubilised a total of 51.6–60.6% of AIS, the yields of CDTA extracts accounting for approximately 9.6–12.2% of AIS. The extracts as well as the residues were analysed for their sugar composition and protein and starch contents. CDTA extracted the bulk of uronic acid in AIS, but the uronic acid content (after dialysis) of these extracts showed a significant decrease as the fruits ripened (from 439 to 252 mg g^?1 between the first and the last degree of ripeness). Analysis of the CDTA extracts by anion exchange and size exclusion chromatography showed a gradual appearance of new pectic populations at low degrees of methylation and low molecular weights, indicating that CDTA‐soluble pectins are demethylated and depolymerised during ripening. The dilute alkali (0.05 M KOH) extracts were essentially composed of proteins in addition to a minor quantity of pectin. The 1 M KOH and principally 4 M KOH treatments led to the extraction of hemicelluloses, mainly xyloglucan‐like and mannan‐like polymers. These extracts also contained substantial amounts of protein and starch. No variation related to the degree of ripeness was visible in the sugar composition of the alkali extracts. The molecular weight distribution of the hemicelluloses did not change with the degree of ripeness. The final residues accounted for 21.4–27.3% of AIS and were mostly composed of glucose (827–908 mg g^?1). All these results suggested that only CDTA‐soluble pectins were involved in bush butter fruit softening. © 2001 Society of Chemical Industry     

Physicochemical Properties of Casein‐Starch Interaction Obtained by Extrusion Process

Extruded samples of starch‐casein blends were processed by using a single‐screw extruder. The independent variables in the process were temperature (126–194°C), moisture content (18–29%) and starch‐casein blend (5–95%). These independent variables affected significantly the physicochemical and textural properties of the biopolymers. The highest values for expansion (EXP) and water absorption index (WAI) were found when a higher starch proportion was present in the blends, at 126°C barrel temperature and moisture content higher than 25%. By increasing the barrel temperature, from 126°C to 194°C, the water solubility index (WSI) and color parameter were increased. Initial viscosity (IV) and viscosity at 90°C (V90) were mainly affected by the barrel temperature at 194°C. However, the viscosity at 50°C (V50) was affected neither by the different extrusion variables nor by the biopolymer proportion in the blends. Compression force (CF) was strongly dependent on moisture content and casein proportion in the blend. The higher CF values were found at starch concentrations around 50% and 25% moisture content, for higher or lower values than these the obtained extruded products were softer and consequently had lower CF values.     

Effects of soy protein isolate,acid-hydrolysed vegetable protein and glucose on the volatile components of extruded wheat starch

The volatile components produced in wheat starch containing 1% soy protein isolate (SPI), and wheat starch/1% SPI combined with 1% glucose, 1% acid-hydrolysed vegetable protein (aHVP), or 1% glucose and 1% aHVP, extruded under different processing conditions (temperatures of 150 or 180 °C and moisture content of 16% or 20%), were identified by gas chromatography–mass spectrometry (GC–MS). Gas chromatography olfactometry (GCO) was used to assess the odour intensity of volatile components present in the starch/glucose/SPI and starch/glucose/SPI/aHVP extrudates obtained at 180 °C. In total, 94 compounds were identified in the eight extrudates. The smallest number (31) was found in the extrudate of the starch/glucose/SPI feedstock processed at 150 °C and the largest (64) in the extrudate of the starch/SPI feedstock processed at 180 °C. Lipid degradation products, such as alkanals, 2-alkanones, 2-alkenals and 2,4-alkadienals, were present in all extrudates in significant quantities. Strecker aldehydes were also present in all extrudates; however, in those extrudates containing aHVP, these compounds were quantitatively the dominant components. Maillard reaction products, such as pyrroles, pyrazines and oxazoles, were mainly found in extrudates containing aHVP whereas sulphur-containing aliphatic compounds were found in all extrudates. The production of the Maillard reaction products and sulphur-containing compounds was favoured by extrusion at 180 °C. Sensory analyses showed that each of the eight extrudates had different odours, and that the extrudates containing both glucose and aHVP possessed the highest overall odour intensity. In addition, SPI was found to have a modifying effect on the volatile content and odour of extrudates also containing glucose and aHVP.     

Functional properties of granular cold‐water swelling maize starch: effect of sucrose and glucose

In this study, granular cold‐water swelling (GCWS) maize starch was prepared by alcoholic‐alkaline treatment and its functional properties were determined at different concentrations (0%, 10%, 20%, 30% and 40% of dry starch weight basis) of sucrose and glucose as two common sweeteners. Light micrographs revealed that control GCWS starch has a wrinkled surface; however, as the sugar content increased, the granules became smoother and at high sugar levels, the wrinkles were totally diminished. Sugars also brought about significant functional changes. The water absorption, cold‐water viscosity, textural parameters and freeze–thaw stability of the samples increased, whereas turbidity decreased by increasing the concentration of sugars. Generally, the extent of these changes in samples with sucrose was greater than those with glucose.     

Steady and Dynamic Shear Rheology of Fucoidan‐Buckwheat Starch Mixtures

Rheological properties of fucoidan (F) and buckwheat starch (B) mixtures (3% or 6%) at different blending ratios of fucoidans (0, 0.1, 0.2, 0.5 and 1.0%) were investigated in steady and dynamic shear. Steady shear viscosity measurement revealed that aqueous pastes of the BF blends (3%, w/v) had a pseudoplastic and shear‐thinning behavior with flow behavior index (n) values of 0.61–0.68. The substitution of starch with fucoidan polymers significantly lowered the apparent viscosities compared with the pure starch paste and, when mixed with less than 0.5% of fucoidan, the viscosities of the pastes were even lower than those of the starch pastes at the corresponding starch concentrations. According to dynamic viscoelastic measurement performed at 6% total carbohydrate concentration, buckwheat starch mixtures behaved like weak gels and the BF blends containing less than 0.5% fucoidan had considerably lower storage (G') and loss (G') moduli than the starch paste at the corresponding starch concentrations. However, the magnitude of G' increased with fucoidan concentrations over 0.5%, suggesting that a concentration of fucoidans > 0.5% might enhance the formations of three‐dimensional networks and crosslinking of the starch samples, probably because of the mutual exclusion between starch and fucoidan polymers through the phase separation process. This study indicates that it is possible to obtain the BF blends having various rheological properties by changing the concentration of fucoidan polymers.     

Phosphorus and Amylose Branching in Rice Starch Granules

Phosphorus content of rice starch granules prepared by DoBS extraction of milled rice protein was lowest and was mainly 6-phosphoglucose for 2 waxy rices. For 6 nonwaxy rices it was highest and predominantly phospholipid P based on choline content. Defatting with water-saturated butanol reduced both choline and P content of nonwaxy rice starch. Once recrystallized amylose of 7 rices had 72–84% β-amylolysis limit, DP 532–793 glucose units per reducing end, CL 101–157 glucose units per nonreducing end and 3.4–7.5 branches/molecule.     

Structures and Functional Properties of Starch From Seeds of Three Soybean (Glycine max (L.) Merr.) Varieties*

Structures and functional properties of starch from high‐protein, lipoxygenase‐free and low‐linolenic acid soybean variety seeds collected 20 d prior to harvest were investigated. Soybean starches exhibit C_B‐type X‐ray diffraction patterns, and granule diameters were very small (0.7 to 4 µm). Soybeans, 20 d prior to harvest contained 10.9–11.7% starch (dry basis). Apparent amylose content was 19–22% and absolute amylose content was 11.8–16.2%. Amylopectin weight‐average molar mass ranged from 5.1 to 11.3×10⁸ g/mol. Amylopectin average branch chain‐length, determined by anion‐exchange chromatography with an amyloglucosidase post‐column and pulsed amperometric detector, was very short relative to other starches (20.4–20.9). Onset gelatinization temperature ranged from 52–54°C, and ΔH was 12–13 J/g. Paste viscosity was low relative to other starches, especially peak (81–93 RVU) and final (93–106 RVU) viscosity. The apparent amylose content of the low‐linolenic acid soybean starch was significantly higher than that of high‐protein soybean starch, and absolute amylose content of low‐linolenic acid soybean starch was significantly higher than that of lipoxygenase‐free soybean starch. Based on our results, investigations on whether soybeans with different fatty acid oil composition have different starch structures would be worthwhile. Field replicates for each soybean variety exhibited high variation in starch characteristics, with further differences in starch structures and functional properties likely to be determined once variation is minimized.     

Preferential binding of SBD from Arabidopsis thaliana SSIII to polysaccharides: Study of amino acid residues involved

SS III (SSIII) has been reported to play a regulatory role in the synthesis of transient starch. SSIII from Arabidopsis thaliana contains 1025 amino acid residues and has an N‐terminal transit peptide for chloroplast localization followed by three in tandem starch‐binding domains (SBDs D1, D2, and D3, residues 22‐591). Its C‐terminal catalytic domain (residues 592–1025) is similar to bacterial glycogen synthase. Binding studies to raw starch and its individual components, AM or AP show that the SBD region binds preferentially to AM, and that the D1 domain is mainly responsible for this selective binding. The D2 domain contains two binding sites which include amino acid residues Y394 (binding site 1) and W366 (binding site 2) acting cooperatively with the D1 domain in the binding process while G335 and W340 have a minor role. In addition, mutations in these residues also affect the kinetic parameters for the polysaccharide substrate of SSIII.     

Synthesis,characterization and swelling behaviour of superabsorbent polymers from cassava starch‐graft‐poly(acrylamide)

Superabsorbent polymers (SAPs) were prepared from cassava starch by graft copolymerization of acrylamide on to starch using ceric ammonium nitrate (CAN) as free radical initiator, followed by alkali saponification. The reaction parameters such as concentration of acrylamide, concentration of CAN, temperature, and duration of polymerization reaction were optimized for maximum water absorbency using a 4‐factor 3‐level Box‐Behnken design. The highest values of percentage grafting and absorbency obtained were 174.8% and 425.2 g/g, respectively. The polymers were characterized by determination of grafting efficiency, N‐content, acrylamide content, FTIR analysis, SEM and XRD analyses. Thermogravimetric analysis (TG) showed that the SAP has higher thermal stability. The rate of water absorbency and the swelling behaviour of the SAP under different conditions of pH, and different salts were determined. The de‐swelling pattern of the hydrogels over different time durations was also determined.     

Properties of Cassava Starch Modified by Amylomaltase from Corynebacterium glutamicum

Amylomaltase (α‐1,4‐glucanotransferase, AM; EC 2.4.1.25) from Corynebacterium glutamicum expressed in Escherichia coli was used to prepare the enzyme‐modified cassava starch for food application. About 5% to 15% (w/v) of cassava starch slurries were incubated with 1, 3, or 5 units of amylomaltase/g starch. Apparent amylose, amylopectin chain length distribution, thermal properties, freeze–thaw stability, thermo‐reversibility, and gel strength of the obtained modified starches were measured. The apparent amylose content and retrogradation enthalpy were lower, whereas the retrogradation temperatures, freeze–thaw stability, and thermo‐reversibility were higher than those of the native cassava starch. However, when amylomaltase content was increased to 20 units of amylomaltase/g starch and for 24 h, the modified starch showed an improvement in the thermo‐reversibility property. When used in panna cotta, the gel strength of the sample using the 20 units/24 h modified cassava starch was similar to that of using gelatin.     

Cottage Level Cassava Starch Processing Systems in Colombia and Vietnam

In the tropics, cassava starch is produced at artisanal and industrial scales. This paper focuses on a new methodology enabling the technoeconomical comparison of small-scale cassava starch manufacturing process (1–5 t of starch/day) in two markedly different contexts (Colombia and Vietnam). Measurements were conducted during trial runs for each unit operation (washing/pealing, rasping, extraction and separation). Starch mass balance was calculated from sample composition (moisture, starch and crude fiber and ash content). Production capacity, water consumption, electric requirements and capital–labor costs were also measured. The manufacturing processes differed mainly on starch recovery from starch present in washed roots (65 vs. 76%), extraction capacity (0.3 vs. 0.9 t of washed roots/h), water consumption (45 vs. 21 m³/t of dry starch), energy consumption (59 vs. 55 kWh/t of starch) and production costs (1,156 vs. 162 US$/t of starch) for Colombia and Vietnam, respectively. Moreover, the effectiveness of the starch extraction process could largely be attributed to the differences in the extent of root disintegration achieved with different rasping equipment.     

Starch properties of malted barley in relation to real degree of fermentation

Real degree of fermentation (RDF) is an important measure of brewhouse performance in the production of beer. In this work, the relationship of RDF with malted barley starch properties was investigated. Starches were isolated from 25 malted barley samples and analyzed for molecular size distribution (by HPSEC), AP structural features (by high‐performance size exclusion chromatography with multi‐angle laser light scattering and RI detectors), and thermal properties (by DSC). Cluster analysis, analysis of variance, principal component analysis, bivariate correlation, and multiple linear regression analysis were used in establishing correlations. RDF, AM, and AP content were 74.0–80.1%, 25.2–34.4%, and 65.6–74.9%, respectively. Starch gelatinization enthalpy was 6.4–8.1 J/g, and onset gelatinization temperature was 58.5–64.3°C. AP and AM content had a positive and negative impact on RDF, respectively. The effect of thermal properties (starch gelatinization and AM‐lipid complex melting) on RDF was not clear. Starch properties explained up to 86% of RDF variance to indicate that other malted barley constituents and/or properties also contribute to cultivar variations in RDF.     

Macromolecular Changes in Extruded Starch‐Films Plasticized with Glycerol,Water and Stearic Acid

Native corn starch, plasticized with water, glycerol and stearic acid, was extruded in a conical twin‐screw extruder and sheeted into 0.4–0.6 mm thick films. The effects of extrusion and plasticizers on gelatinization, as well as the molecular and structural changes, in thermoplastic starch were analyzed. The onset and peak gelatinization temperatures of extruded starch varied from 42–46°C and 52.9–56.9°C, respectively, depending on the glycerol content. The enthalpy of gelatinization of extruded thermoplastic starch in excess water varied from 3.6–7.6 J/g, which also increased with plasticizer content. Amylose‐lipid complexes were formed during extrusion, and their enthalpies depended on the initial stearic acid and moisture contents. High‐performance size‐exclusion chromatography (HPSEC) data revealed that the starch underwent fragmentation during extrusion even under highly plasticized conditions, but the degradation was not severe as compared to previous findings. The relative percentages of amylopectin and amylose in native starch were 76.9 and 23.1%, respectively, which were changed to 71.3–76.6% and 23.4–28.7% in the extrudates. The average molecular weights of amylopectin and amylose in the extrudates ranged from 1.55×10⁷–2.07×10⁷ and 4.35×10⁵–7.39×10⁵, respectively. On the other hand, the molecular weights of amylopectin and amylose in native corn starch were observed as 2.27×10⁷ and 4.68×10⁵, respectively. Cross‐polarization magical angle spinning (CP/MAS) and high‐power decoupling (HP‐DEC) nuclear magnetic resonance (NMR) spectra of thermoplastic starch revealed the characteristics of amylomaize starch, confirming HPSEC results that the amylopectin macromolecules underwent fragmentation into amylose‐like fractions. In the extrudates, glycerol was found to be less mobile and entrained within the starch network.     

Preparation,digestibility, and glucose response in mice of rice coated with resistant starch type 4 using locust bean gum and agar

This study investigated the technical feasibility of coating type 4 resistant starch (RS4) onto rice with the edible polymers locust bean gum (LBG) and agar. The coating solutions were prepared using LBG, agar, and a mixture of LBG and agar at three concentrations (0.01%, 0.1% and 1%). The raw milled rice was soaked in the prepared coating solutions, rolled in RS4 powder and dried. Microscopic observation revealed that the RS4 coating on the rice surface with 0.1% and 1% LBG–agar mixture had a resistance to washing and cooking and covered the whole surface of the rice with good adherence. The thickness of the RS4 coating on the rice surface with 0.1% and 1% LBG–agar mixture was approximately 74 and 233 μm, respectively. Compared with uncoated rice and rice mixed with RS4, the RS4‐coated rice showed lower starch digestibility, a decreased glucose response and a slower rate of blood glucose decrease.     

Determination of nutritionally important starch fractions of some Turkish breads

By using an in vitro technique that measures the rate and extent of starch digestion, the starch in a food can be classified as rapidly-digestible starch (RDS), slowly-digestible starch (SDS) and resistant starch (RS). The amount of these fractions in rye bread, wheat bran bread and corn flour bread were calculated from the experimentally determined values obtained by controlled enzymatic hydrolysis and measurement of released glucose by colorimetry, using a glucose oxidase kit. Free glucose and total starch analysis were also carried out to calculate rapidly-available glucose (RAG) content and starch digestibility rate index (SDRI) of breads. RDS content of the rye bread was higher than the wheat-bran bread and corn flour bread (P<0.05). SDS contents of all breads were not significantly different from each other. Wheat bran bread was found to have a significant amount of RS (6.6%; on dry matter basis) when compared to the other breads (P<0.05). A significant negative correlation (r=−0.95, P<0.05) was also found between RS content and SDRI value of breads.     

Characterizing starch structure in a gluten‐free pasta by using iodine vapor as a tool

The suitability of starch–iodine complex to highlight differences in chain mobility and crystallinity of starch in rice pasta was investigated. Two pasta samples were produced starting from the same rice flour (RF) and using a conventional extrusion process without (Process A) and with (Process B) a preliminary extrusion‐cooking step. Based on the absorption/scattering coefficient (K/S) spectra (obtained after equilibration above K₂SO₄ and exposure to iodine vapor), Pasta A showed a behavior similar to RF. Process B exhibited a greater iodine binding capacity suggesting greater starch chain mobility. Moreover, the extrusion‐cooking conditions seem to favor the loss of starch crystallinity and the formation of larger amorphous regions. The organization of starch polymers observed in Pasta B could account for its higher capacity to water absorption during cooking.     

Ghosts of B‐type Wheat Starch Granules in Concentrated KI/I2 Solution

When B‐type (2.0–8.0 µm) wheat starch granules containing various amounts (2.1–25%) of amylose were treated with 25% KI/10% I₂ solution, low‐amylose (below 10% amylose) B‐type wheat starch granules changed to the ghost form. It is known that A‐type (25–35 µm) wheat starch granules change to the ghost form and show a typical double structure (a black‐brown central portion and red‐brown surrounding portion), however, the B‐type wheat starch ghosts did not show the same double structure but rather a simple (red‐brown portion) sack form. The relative ghost areas in the B‐type wheat starch granules were highly correlated to the amylose content (%), which was similar to the results of A‐type starch granules. This suggests that the amylose molecule in B‐type starch contributes to the structural stability of the starch granule.     

Development and Physicochemical Characterization of New Resistant Citrate Starch from Different Corn Starches

Resistant starch has drawn broad interest for both potential health benefits and functional properties. In this study, a technology was developed to increase resistant starch content of corn starch using esterification with citric acid at elevated temperature. Waxy corn, normal corn and high‐amylose corn starches were used as model starches. Citric acid (40% of starch dry weight) was reacted with corn starch at different temperatures (120–150°C) for different reaction times (3–9 h). The effect of reaction conditions on resistant starch content in the citrate corn starch was investigated. When conducting the reaction at 140°C for 7 h, the highest resistant starch content was found in waxy corn citrate starch (87.5%) with the highest degree of substitution (DS, 0.16) of all starches. High‐amylose corn starch had 86.4% resistant starch content and 0.14 DS, and normal corn starch had 78.8% resistant starch and 0.12 DS. The physicochemical properties of these citrate starches were characterized using various analytical techniques. In the presence of excess water upon heating, citrate starch made from waxy corn starch had no peak in the DSC thermogram, and small peaks were found for normal corn starch (0.4 J/g) and Hylon VII starch (3.0 J/g) in the thermograms. This indicates that citrate substitution changes granule properties. There are no retrogradation peaks in the thermograms when starch was reheated after 2 weeks storage at 5°C. All the citrate starches showed no peaks in RVA pasting curves, indicating citrate substitution changes the pasting properties of corn starch as well. Moreover, citrate starch from waxy corn is more thermally stable than the other citrate starches.     

Laboratory Wet‐Milling of Grain Sorghum With Abbreviated Steeping to Give Two Products

Short‐time and no‐time steeping were used in the wet‐milling of grain sorghum to give two products, starch in over 78% recovery (starch basis) plus the remaining grain solids. In the wet‐milling process 1.5 parts of fresh water were used per part of grain to compensate for drying and transfer losses. Starting with 100 g (dry solids) of commercial No.2 grain sorghum, steep time (1—3 h), steep temperature (25—60 °C), and coarse‐grinding speed (7, 500—12, 500 rpm with tip speed of 90.4—150.7 km/h) were varied in a model study; starch recovery, starch lightness (L*), and damaged starch were the responses. Grain sorghum was steeped with twice its weight of process water containing 0.2% sulfur dioxide and the steeped kernels were added to an equal volume of process water and the mixture was ground for 6 min in a Waring blender with blunt blades (d = 3.2 cm). The course‐ground material was sieved (opening 1190 μm) to collect the bran/germ, and the throughs were allowed to stand. The sedimented phase was finely ground by one pass through a plate mill, and the fine fiber removed by sieving (opening 73 μm). The slurry was adjusted to a specific gravity of 1.04, and the starch was separated from the protein fraction on a starch table. The protein fraction was combined with the steep‐liquor concentrate (54% solids) plus the bran/fiber and the fine‐fiber fractions to give the co‐product, which contained 70% moisture (wet basis, wb) and 27% protein (dry basis, db). In the surface response study, recovery of starch ranged from 57 to 89%, starch protein content from 0.4 to 0.5%, and lightness (L*) from 90 to 93. Damaged starch content was constant at around 0.4%. Commercial grain sorghum gave the highest starch recovery (90%) after steeping 2 h at 55 °C and coarse‐grinding at 10, 500 rpm; whereas a food‐grade, a white and a red sorghum gave 85, 84, and 80% recoveries, respectively. The four starches had lightness (L*) values of 93—94 and damaged starch contents of 0.4—0.6%. When the commercial grain sorghum was wet‐ground without steeping in 2 parts of water containing 0.2% sulfur dioxide, a 78% recovery of starch was obtained with L* 93.7 and starch damage 0.5%.     

Study on the physicochemical properties and in vitro digestibility of starch from yam with different drying methods

Four methods were applied to dry yam slices, and then, starches were isolated from dried yam slices. Starch isolated from fresh yam was as the study control, and physicochemical properties and in vitro digestibility of starches were studied. The results showed that the amylose content ranged from 12.62% to 28.25%, water‐binding capacity (WBC) from 111.67% to 262.88%, paste clarity from 2.1% to 6.23%, resistant starch (RS) from 66.60% to 88.49% and crystallinity from 11.27% to 25.52%. Compared with the control starch, hot air‐drying at 60 °C significantly decreased amylose content, paste clarity, RS and crystallinity, while increasing the WBC. Low levels of rapidly digestible starch and glucose and high RS levels were found in the starch from freeze‐drying yam. Digestibility of the starches was significantly correlated with amylose content, WBC, paste clarity and swelling power. The starch samples were divided into three groups by principal component analysis (PCA).