Starch pastes thinning during high-pressure homogenization

High-pressure homogenization induced thinning of potato and cassava starch paste was investigated. The starch slurries at a concentration of 2.0 wt.% were heated at 90 °C for 1 h and then rapidly cooled in tap water. The cooled starch pastes were homogenized at various pressures ranging from 0 to 100 MPa using a lab-scale high-pressure homogenizer. The influence of homogenizing pressure on the temperature, apparent viscosity, electrical conductivity, and percent light transmittance of homogenized starch pastes were determined. Temperatures of homogenized starch pastes increased linearly with the increase of the applied pressure, and the rate was 0.177 °C/MPa and 0.186 °C/MPa for potato and cassava starch pastes, respectively. After high-pressure homogenization, the apparent viscosities of the starch pastes decreased, while the percent light transmittances of them increased. However, the electrical conductivities of starch pastes were not affected by homogenization.     

Controlling the Three-Dimensional Printing Mechanical Properties of Nostoc Sphaeroides System

The main purpose of this paper is to explore the opportunities for fresh Nostoc sphaeroides (N. sphaeroides) to be applied to 3D food printing. N. sphaeroides is rich in nutrients and its paste possesses shear thinning properties. It was found the product obtained by 3D food printing with fresh N. sphaeroides had poor printability and was easy to collapse. In this study, we compared the addition of different potato starch (2%, 4%, 6% and 8%) to the characteristics of 3D printing of the N. sphaeroides gel system. The results obtained from the rheological analysis showed that the 6% potato starch added to of N. sphaeroides gel can be utilized for 3D food printing. The addition of potato starch increased the viscosity of the mixture so the printed lines were not easily broken, and the “self-supporting ability” of the material itself was enhanced to maintain a good shape without collapse. Texture profile analysis also showed that the 6% starch added printed product had the best gumminess parameter. In order to get a better printed product, the effects of printing parameters (nozzle diameter (Dn), extrusion rate (Vd) and nozzle moving speed (Vn)) on material printing performance and product formability was tested. When Dn, Vd, Vn were = 1.2 mm, 20 mm³/s, 25 mm/s, respectively, the printed product was having similar to the target product, with less breakage and less the changing of shape. Overall results show that 3D printing technology is a rising method for producing N. sphaeroides-based new products.

     

Structure of potato starch pastes in the ageing process by the measurement of their dynamic moduli

The effect of ageing on the rheological properties of potato starch pastes was investigated by measurement of dynamic viscoelasticity. The value of the storage modulus (G′) increased rapidly with time for the first few hours, but attained equilibrium after a long period of ageing. The relation between the concentration and the storage modulus showed a c^1·6 dependence. The Avrami exponent (n) obtained in this study was 0·66 and deviated significantly from the value (n = 1), corresponding to rod-like growth of crystal. The rate of storage modulus increase decreased with increasing concentrations up to 10%, and at higher concentrations little or no increase was observed. In addition, the rate of storage modulus increase increased dramatically when the NaCl concentration was raised to levels of 0·01 or above. An even greater increase in rate occurs on addition of AlCl₃.     

Starch phosphorylation associated SNPs found by genome-wide association studies in the potato (Solanum tuberosum L.)

Background

The natural variation of starch phosphate content in potatoes has been previously reported. It is known that, in contrast to raw starch, commercially phosphorylated starch is more stable at high temperatures and shear rates and has higher water capacity. The genetic improvement of phosphate content in potato starch by selection or engineering would allow the production of phosphorylated starch in a natural, environmentally friendly way without chemicals. The aim of the current research is to identify genomic SNPs associated with starch phosphorylation by carrying out a genome-wide association study in potatoes.

Results

A total of 90 S. tuberosum L. varieties were used for phenotyping and genotyping. The phosphorus content of starch in 90 potato cultivars was measured and then statistically analysed. Principal component analysis (PCA) revealed that the third and eighth principal components appeared to be sensitive to variation in phosphorus content (p = 0.0005 and p = 0.002, respectively). PC3 showed the correlation of starch phosphorus content with allelic variations responsible for higher phosphorylation levels, found in four varieties. Similarly, PC8 indicated that hybrid 785/8–5 carried an allele associated with high phosphorus content, while the Impala and Red Scarlet varieties carried alleles for low phosphorus content. Genotyping was carried out using an Illumina 22 K SNP potato array. A total of 15,214 scorable SNPs (71.7% success rate) was revealed. GWAS mapping plots were obtained using TASSEL based on several statistical models, including general linear models (GLMs), with and without accounting for population structure, as well as MLM. A total of 17 significant SNPs was identified for phosphorus content in potato starch, 14 of which are assigned to 8 genomic regions on chromosomes 1, 4, 5, 7, 8, 10, and 11. Most of the SNPs identified belong to protein coding regions; however, their allelic variation was not associated with changes in protein structure or function.

Conclusions

A total of 8 novel genomic regions possibly associated with starch phosphorylation on potato chromosomes 1, 4, 5, 7, 8, 10, and 11 was revealed. Further validation of the SNPs identified and the analysis of the surrounding genomic regions for candidate genes will allow better understanding of starch phosphorylation biochemistry. The most indicative SNPs may be useful for developing diagnostic markers to accelerate the breeding of potatoes with predetermined levels of starch phosphorylation.

     

Osmoregulation in Cotton in Response to Water Stress : III. Effects of Phosphorus Fertility

Cotton (Gossypium hirsutum) (L.) was grown in a sand and nutrient solution system at two levels of phosphorus (0.5 and 5.0 millimolar). Within each phosphorus treatment, plants were either watered daily or acclimated to water stress by subjection to several water stress cycles.

Stress acclimation increased leaf starch at the low phosphorus level, but not at the high phosphorus level. High phosphorus increased leaf sucrose and glucose concentration in both acclimated and nonacclimated plants, but had little effect on osmotic adjustment or the relationship between turgor and water potential.

In nonacclimated plants, high phosphorus increased both leaf conductance and photosynthesis at high water potentials. In acclimated plants, high phosphorus increased photosynthesis but decreased conductance, thus increasing water use efficiency at the single leaf level.

     

Glucoamylase production by the marine yeast Aureobasidium pullulans N13d and hydrolysis of potato starch granules by the enzyme

Under the optimal conditions, 10 U/ml of glucoamylase was produced by the marine yeast Aureobasidium pullulans N13d. It was noticed that the crude glucoamylase actively hydrolyzed potato starch granules, but poorly digested raw corn starch and sweet potato starch, resulting in conversion of 68.5, 19 and 22% of them into glucose within 6 h of incubation in the presence of 40 g/l of potato starch granules and 20 U/ml of the crude enzyme. When potato starch granules concentration was increased from 10 to 80 g/l, hydrolysis extent was decreased from 85.6 to 60%, while potato starch granules concentration was increased from 80 to 360 g/l, hydrolysis extent was decreased from 60 to 56%. Ratio of hydrolysis extent of potato starch granules to hydrolysis extent of gelatinized potato starch was 86.0% and the hydrolysis extent of potato starch granules by action of the crude glucoamylase (1.0 U/ml) was 18.5% within 30 min at 60 °C. Only glucose was detected during the hydrolysis, indicating that the crude enzyme could hydrolyze both α-1,4 and α-1,6 linkages of starch molecule in the potato starch.     

Effect of salinity on physiological characteristics,yield and quality of microtubers <Emphasis Type="Italic">in vitro</Emphasis> in potato

In vitro microtuberization provides an adequate experimental model for the physiological and metabolic studies of tuberization and the preliminary screenings of potential potato genotypes. The effects of saline stress at 0–80 mmol concentration on in vitro tuberization of two potato cultivars were investigated in this study. With an increase in the salt concentration, the microtuberization of potato was either delayed by 5–10 days (20 and 40 mmol NaCl) or inhibited completely (80 mmol NaCl) in addition to the reduction in microtuber yields. The two potato genotypes studied showed different trends in total soluble sugars, sucrose and starch contents of microtubers under NaCl stress, while glucose and fructose levels remained unchanged. The vitamin C content in microtubers of two potato genotypes was reduced by salt stress. Salinity applied from 20 to 60 mmol progressively increased proline and malondialdehyde (MDA) levels in microtubers of both the potato cultivars. In genotype Zihuabai, NaCl at a low concentration (20 mmol) led to a significant increase in peroxidase (POD) and polyphenoloxiadase (PPO) activities, while in Jingshi-2, the PPO activity decreased progressively with an increase in NaCl concentrations. Genotype Zihuabai exhibited higher tolerance to salt stress than Jingshi-2 under in vitro conditions. These results could be used for preliminary selections of salt tolerance in potato breeding programmes.     

Effect of orientation on the physical properties of potato amylose and high-amylose corn starch films

The effect of orientation on the properties of amylose and starch films was studied in order to determine if film strength, flexibility, and water resistance could be improved. Potato amylose and high (70%) amylose corn starch were peracetylated, cast into films, stretched in hot glycerol 1-6 times the original length, and deacetylated. Molecular orientation of potato amylose films was much higher than for high-amylose corn starch films as determined by optical birefringence. For potato amylose films, orientation resulted in large increases in tensile strength and elongation but little change in modulus. For high-amylose corn starch films, tensile strength and modulus did not change with draw ratio but elongation to break increased from about 8% to 27% as draw ratio increased from 1 to 5. Scanning electron micrographs revealed many small crazes in the drawn starch films, suggesting that the improved film toughness was due to energy dissipation during deformation of the crazes. Annealing of drawn films at 100% humidity resulted in partial crystallization and improved wet strength.     

Effect of amylose deposition on potato tuber starch granule architecture and dynamics as studied by lintnerization

The effect of amylose deposition on the amylopectin crystalline lamellar organization in potato starch granules was studied by mild acid, so‐called lintnerization, of potato tuber starch transgenically engineered to deposit different levels of amylose. The starch granules were subjected to lintnerization at different temperatures (25, 35, and 45°C) and to two levels of solubilization, ～ 45 and 80%. The rate of the lintnerization increased with temperature but was suppressed by amylose. The molecular size of the lintner dextrins increased with temperature, but this effect was suppressed by the presence of amylose. At high temperatures and low‐amylose content, the degree of branches was high with the concomitant increase in size in the dextrins. A portion of the branches was resistant to debranching enzymes possibly due to specific structural formations. The effects of temperature suggested a unique granular architecture of potato starch, and a model showing the dependence of temperature on the dynamic arrangement of amylopectin and amylose in the crystalline and amorphous lamellae for the potato starch is suggested. © 2012 Wiley Periodicals, Inc.     

Effect of substitution of wheat starch by potato starch on the performance,digestive physiology and health of growing rabbits

The goal of this research was to study the effect of the substitution of wheat starch by potato starch (PS) on the performance, health and digestion of growing rabbits. Three experimental diets were formulated with 0%, 7% and 14% PS (PS0, PS7 and PS14, respectively) and similar starch contents (22% dry matter basis), proteins and fibre. The three diets were administered to three groups of 48 rabbits from weaning (28 days) to slaughter (70 days), and growth and health measurements were made. Another 10 rabbits per diet (30 rabbits at each age), reared under similar conditions, were slaughtered at 6 to 10 weeks of age, and the digesta were collected to analyse the caecal microbial activity (pH, volatile fatty acids (VFA) levels, fibrolytic activity) and the starch concentration in the ileal digesta. At the same ages, the whole tract digestibility coefficients were measured in 10 other rabbits for each treatment (30 rabbits). The feed intake between 28 and 42 days of age (days) increased by 11% (P < 0.05) in PS0 v. PS14. Over the whole growth period (28 to 70 days), weight gain was similar among diets (40.5 g/day), whereas the feed intake and feed conversion increased (8.5% and 5.2%, respectively; P < 0.05) with the PS14 diet. Mortality and morbidity were not affected by the diets. The starch concentration of the ileal contents increased (P < 0.01) with the addition of PS to the diet (0.39%, 0.77% and 1.08% for diets PS0, PS7 and PS14, respectively). Starch digestibility was 0.8 percentage units higher (99.8% v. 99.0%) with the PS0 diet than the PS14 diet (P = 0.04). The bacterial cellulolytic activity in the caecum tended to be higher with the PS14 diet (P = 0.07). The total VFA caecal concentration increased (P < 0.01) only in 6-week-old rabbits with PS7 compared with PS0 (54.7 v. 74.5 mmol/l). Protein digestibility and ileal starch concentration decreased (P < 0.05) with age (6 v. 10 weeks), and hemicelluloses digestibility increased (P < 0.05). At 10 weeks of age, rabbits showed a higher VFA pool (6.25 mol) and proportion of butyrate (15.9%) and a lower proportion of acetate (79.3%), ammonia level (7.5 mmol/l) and C3/C4 ratio (0.31) than at 6 weeks of age. The intake of potato starch had no effect on the performance, caecal microbial activity or digestive health of growing rabbits.     

Studies on the Amylolytic System of the Black-koji Molds

Saccharogenic and dextrinogenic amylase fractions were prepared from Black-koji amylase system and their actions investigated with a number of different substrates.

It was found that saccharogenic amylase fraction completely hydrolyzes glutinous rice starch and glycogen to glucose, without leaving any limit dextrin. On the other hand, this enzyme fraction converts potato starch to an extent of about 90% theoretical glucose, the remainder being left as limit dextrin, which is colored purple by iodine. The complete hydrolysis of the branched substrates except potato starch shows that the saccharogenic amylase fraction is capable of hydrolyzing the l,6-α-d-glucosidic linkage besides the 1,4-linkage, while the branched fraction of potato starch may contain some sort of anomaly to the enzyme. Dextrinogenic amylase fraction hydrolyzes starch and glycogen just as malt α-amylase.     

Modified natural halloysite/potato starch composite films

Halloysite/potato starch composites were prepared by adding modified natural halloysite nanotubes into potato starch matrices to reenforce the mechanical properties of potato starch films. The halloysite/potato starch films were characterized by X-ray diffraction, scanning electron microscope and infrared spectrometry. Meanwhile, the mechanical properties and transparency of the films were studied. The results show that the modified halloysite nanotubes can be well distributed in the starch matrix and thus the tensile strength of the films was clearly enhanced. The flexibility of the films could be improved through adding glycerol although at the cost of reducing tensile strength. But incorporation of PVA could further improve the tensile strength of the halloysite/potato starch films.     

MARINE CRYPTOMONAD STARCH FROM AUTOLYSIS OF GLYCEROL-GROWN CHROOMONAS SALINA1

The extracellular starch released by autolysis of glycerol-grown Chroomonas salina (Wislouch) Butcher was purified and chemically characterized. It contained 99%D-glucose, formed a blue complex (λmax at 605 nm) with iodine, and showed an optical rotation value more positive than that of potato starch. Methylation analysis established the presence of 1,4- and 1,4,6-glucoside linkages in the proportion 15:1. These properties indicate the cryptomonad starch to be an iodophilic α-(1,4)-glucan, composed of ca. 30% amylose with amylopectin, and broadly resembling potato, Chilomonas and other unicellular algal starches.     

Production of an amylase-degrading raw starch by Gibberella pulicaris

An endophytic fungus, Gibberella pulicaris, produced an amylase which degraded raw starches from cereals and other crops including raw potato, sago, tapioca, corn, wheat and rice starch. In each case, glucose was the main product. Among the raw starches used, raw potato starch gave the highest enzyme activity (85 units mg^–1 protein) and raw wheat starch the lowest (49 units mg^–1 protein). The highest amylase production (260 units mg^–1 protein) was achieved when the concentration of raw potato starch was increased to 60 g l^–1. Optimum hydrolysis was at 40°C and pH 5.5.     

A rheological comparison between the effects of sodium caseinate on potato and maize starch

The differences in response of 1% potato and 4% maize starch pastes to sodium caseinate inclusion were investigated. Pasting of the starches was performed at 95 °C for l h in a range of concentrations of sodium caseinate. Caseinate levels as low as 0.01% dramatically reduced the swelling volume of potato starch and hence the viscosity of the system. Since sodium chloride addition shows similar effects, it appears that caseinate acts through a non-specific ionic strength effect. The influence of caseinate on maize starch was less clear since it depended on the solvent medium. In distilled, deionized water, there was an increase in viscosity with increasing caseinate concentration, which may simply be explained by a contribution of the caseinate to the viscosity of the continuous phase. However, in 0.1M, pH 7.0 buffer the results suggest that caseinate may inhibit retrogradation as the viscosity of the system after ageing is reduced by its inclusion. It is suggested that phase separation between starch and caseinate is encouraged at high salt concentrations. As a consequence, both starch granule swelling and subsequent retrogradation are discouraged by caseinate in the buffer system, but not when pasting is carried out in distilled, deionized water.     

Physicochemical and Binder Properties of Starch Obtained from Cyperus esculentus

The purpose of this study was to isolate starch from the tubers of Cyperus esculentus L. and evaluate its physicochemical and binder properties. Extraction of starch using sodium metabisulfite yielded 37 g of starch per 100 g of the tubers. Scanning electron microscopy indicated that Cyperus starch consists of oval to elliptical particles with a smooth surface. Cyperus starch demonstrates a narrow particle size distribution with a mean of 8.25 μm. Cyperus starch conforms well to United States Pharmacopeia standards established for widely used starches like maize and potato. The X-ray powder diffraction pattern and moisture sorption profile of Cyperus starch were comparable to that of maize starch. Cyperus starch had lower swelling power than maize and potato starch, indicative of stronger associative forces within the granules. Carr’s index and Hausner ratio indicate that Cyperus starch should have comparable flow properties with respect to maize and potato starch. Cyperus starch was employed as binder for the formulation of metronidazole tablets. Formulations containing 5%, 7.5%, and 10% Cyperus starch were compared with those containing 10% potato starch. At 10% binder concentration, the tablets containing Cyperus starch exhibited better hardness and negligible friability as compared with those with potato starch. Although the binder concentration had a significant effect on the disintegration time of the tablets, it did not seem to affect the dissolution profile. These results indicate that Cyperus starch provides excellent binding properties without compromising drug release characteristics and should be explored in pharmaceutical formulations.Key words: Cyperus esculentus, Cyperus starch, pharmaceutical excipient, physicochemical evaluation, starch characterization     

Characterization of films made with chayote tuber and potato starches blending with cellulose nanoparticles

The aim of this study was to characterize chayotextle starch films reinforced with cellulose (C) and cellulose nanoparticle (CN) (at concentrations of 0.3%, 0.5%, 0.8% and 1.2%), using thermal, mechanical, physicochemical, permeability, and water solubility tests. C was acid-treated to obtain CN. The films were prepared by casting; potato starch and C were used as the control. The solubility of the starch films decreased with the addition of C and CN compared with its respective film without C and CN. No statistical difference (α = 0.05) was found in the films added with different concentrations of C and CN. In general, the mechanical properties were improved with the addition of C and CN, and higher values of tensile strength and elastic modulus were determined in the films reinforced with CN. The melting temperature and enthalpy increased with the addition of C and CN, and the values of both thermal parameters were higher in the films with CN than with C; the enthalpy value of the film decreased when the concentration of C or CN increased in the composite. Low concentration of C and CN is better distributed in the matrix film. The addition of C and CN in the starch films improved some mechanical, barrier, and functional properties.     

A novel raw starch digesting thermostable α-amylase from Bacillus sp. I-3 and its use in the direct hydrolysis of raw potato starch

A new strain of Bacillus sp. I-3, isolated from natural soil samples, showed a high raw starch digesting activity towards potato starch. Upon optimization of various environmental and cultural conditions, the yield of α-amylase reached 642 U/mL. The kinetic characterization of partially purified enzyme exhibited the maximum activity at 70 °C, pH 7.0 and revealed a high thermostability in the presence of 10 mM CaCl₂·2H₂O where it could retain more than 90% residual activity at 70 °C after 3.5 h. At 80, 90 and 100 °C, the enzyme retained 80, 59 and 26% of its maximum activity after 2.5, 0.5 and 0.5 h, respectively. The enzyme preparation had a strong affinity towards raw potato starch granules and was almost completely adsorbed onto it. It also hydrolyzed raw potato starch at a concentration of 12.5% significantly in a short period of time of 12 h.