In vitro Digestibility of Cereal and Legume (Phaseolus vulgaris) Starches by Bovine,Porcine and Human Pancreatic α-Amylases Effect of Dietary Fiber

The effect of heat treatment and dietary fiber from whole and dehulled black bean (Phaseolus vulgaris) seeds on digestibility of various starches by bovine, porcine and human pancreatic α-amylases was studied. Corn, rice, wheat and black bean starch digestibility increased after heating. The degree of hydrolysis of black bean starch ranged between 56 and 83% of the values obtained for cereal starches depending on the enzyme used. Enzyme activity was: human- > porcine > bovine regardless of the substrate employed. Dietary fiber decreased starch digestibility by porcine enzyme. This effect was more marked when whole grain fiber was used. Black bean and rice starch digestibility by human amylase was not affected by fiber, while corn and wheat starch hydrolysis was slightly inhibited. The use of the human enzyme is recomended for in vitro amylolysis assays. Attention is called on the difficulties of extrapolating results obtained with animal enzymes to humans.     

Characterization of Residues from Partially Hydrolyzed Potato and High Amylose Corn Starches by Pancreatic α‐Amylase

High amylose corn starch (HACS) and potato starch were hydrolyzed by pancreatic α‐amylase in vitro. Residues after hydrolysis were collected and characterized for their physicochemical properties and molecular structure. Compared with raw starches, residues had lower apparent amylose contents and higher resistant starch contents. The gelatinization enthalpy of residues from HACS increased while enthalpy of residues from potato starch decreased from 15.4 to 11.3 J/g. Peak viscosity and breakdown values of the residues from potato starch were markedly decreased but final viscosity values did not show much change. Chain length distribution of debranched amylopectin from the residues indicated that the relative portion of short chain in the residue decreased for both starches. More molecules with intermediate chain length (DP 16—31) were found in residue after 48‐h hydrolysis of potato starch.     

Purification and Characterization of α-Amylases of an Alkalopsychrotrophic Micrococcus sp

Two amylases of an alkalopsychrotrophic Micrococcus were purified by chromatographies of DEAE-Toyopearl, Butyl-Toyopearl and Shodex WS-2003. Molecular weights and pI values of the purified enzymes, I and II, were 185000 and 125000 by SDS-PAGE and 4.8 and 4.3 by isoelectric focusing, respectively. Enzyme I had not only amylase but also pullulanase activity. In the presence of Ca²⁺ ions, other properties of both enzymes were very similar: optimum temperature 55–60°C, optimum pH 7.5–8.0 k_m value for maltopentaose 0.09 mM. Both amylases were completely inactivated after incubation with EDTA at 30°C and thereafter, could be reactivated by an addition of CaCl₂. In the absence of Ca²⁺ ions, amylase I became thermoresistant, while the thermostability of amylase II decreased. Neither amylase activity of enzyme I nor enzyme II was inhibited by pullulan.     

Hydrolysis of Cyclodextrin by Aspergillus oryzae α-Amylase

The hydrolysis of α-, β- and γ-cyclodextrins by Aspergillus oryzae α-amylase was studied at pH 5.2 and 37°C. The kinetic parameters were determined and it was found that the V _max value increased markedly in the order α-, β- and γ-cyclodextrin, but no significant difference was observed in the K_m values. The qualitative and quantitative distribution of the hydrolysis products were determined by HPLC. In the case of γ-cyclodextrin the time course of the kinetic parameters was compared to the qualitative and quantitative distribution of the hydrolysis products.     

Hydrolysis of Various Starches by the Synergistic Action of α-Amylase and Glucoamylase in Aqueous Two Phase Impeller Agitated Systems

Various starches were hydrolyzed by the combination of α-amylase and glucoamylase in aqueous two phase impeller agitated systems. The reaction products were determined by the chromatometric method of phenol-sulfuric acid and by HPLC. The effect of temperature on glucose production was studied for these starches in gelatinized and non gelatinized form. It was found that crude corn starch (not in the gelatinized form) at 150rpm and 40°C gives very good results in terms of glucose concentration.     

On Ultrastructural and Nutritional Aspects of Some Tropical Tuber Starches

Type A starches (Manihot utilissima, Dioscorea dumetorum and Colocasia antiquorum) and type B starches (Canna edulis, Dioscorea alata and Dioscorea cayenensis) are investigated. Results show that the degradation of the pure tuber starch as compared with that of feeds made from a particular starch is more or less the same. However, type A starches are more rapidly degraded by bacterial α-amylase. The susceptibility to attack is compared to the nutritional efficiency of the feeds using axenic and holoxenic chickens. Comparison of the degree of degradation of the starch granules in the crop as well as in the feces (by in vitro and in vivo studies) is made by scanning electron microscopy. Type A starches show always a higher susceptibility to α-amylase attack. The feed efficiency tested on chicken and digestibility of tuber starches in the sheep rumen and in the chicken crop increase as their ease of degradation by bacterial α-amylase (in vitro) increases.     

Comparative immunological and chromatographic study of some plant β-Amylases

A comparative study has been made of the β-amylases of barley, wheat, rye, oats and sweet-potato by means of exclusion chromatography and immunochemical analysis. The reactivity of barley malt and wheat β-amylase was compared with different anti-barley and anti-wheat sera. In exclusion chromatography on Sephadex G100, barley β-amylase yielded four, and both wheat and rye, two active components, whereas oat and sweet-potato had only one active component. During the storage of barley, wheat and rye β-amylases the large-molecule components were split into smaller ones; no changes occurred in oat and sweet-potato β-amylases. On analysis against a specific barley β-amylase antiserum, wheat and rye β-amylase gave a reaction which indicated that they were immunologically partly identical with barley β-amylase, and identical with each other. This serum induced no reaction in β-amylases of sweet-potato and oats. The rye β-amylase precipitation line did not display enzymic activity after reaction with this antiserum. Analyses with different antisera of barley and wheat confirmed the partial immunological identity of barley malt and wheat β-amylase. With some barley antisera, partial inhibition of wheat β-amylase activity was observed. A similar phenomenon was apparent when barley malt β-amylase was precipitated with some wheat antisera.     

Physicochemical and Functional Properties of Tropical Tuber Starches: A Review

The tropical tuber crops contain starch as the major component and thus act as important source of starch. Except cassava and to a smaller extent sweet potato, starch from other tuber crops has not been exploited for industrial applications partly because of difficulty in the extraction of the pure starches and partly because of non‐availability of information about the properties of these lesser known starches. This review attempts at collating data available on the physicochemical and functional characteristics of the tropical tuber starches, highlighting their unique properties and potential field of applications. The physicochemical properties like granule shape and size, X‐ray diffraction (XRD) patterns, amylose content, or content of non‐starchy components, show considerable variation among the tuber starches. In addition, factors like genetic origin, environmental conditions and age of the plant also influence the properties. The starch granules of Colocasia esculenta and Dioscorea esculenta tubers are very small whereas those of Canna edulis are very large. XRD patterns of yam starches are generally ‘B’, while the aroid starches possess ‘A’ patterns. DSC gelatinisation temperatures are low for cassava starch and high for the aroid starches. The functional characteristics like viscosity, swelling power and solubility also depend on a number of factors such as varietal variation, method of extraction, processing conditions and instruments used for analysis. Viscosity is high for cassava and C. edulis starches, but low for most aroid starches. Clarity is good for cassava and yam starches compared to the others. Digestibility also varies among the starches. The diversity available in the tuber starches shows that some of the starches can be used in place of chemically modified starches available on the market. The realisation of their importance can help in value addition of these neglected crops and also provide starch with special properties for specific applications.     

Adsorption of α-Amylase from Streptomyces aureofaciens on Cross-linked Starches

The extracellular α-amylase from Streptomyces aureofaciens is adsorbed on modified starches, which are cross-linked with epichlorhydrine or with phosphorus oxichloride. The affinity of the amylase towards the cross-linked starch is influenced by the presence of soluble substrates, pH medium and accompanying proteins.     

Hydrolysis of galactooligosaccharides by commercial preparations of α-galactosidase and β-fruetofuranosidase: Potential for use as dietary additives

In vitro and in vivo studies were conducted with six commercial enzyme preparations (SP249, Energex, Rohament CW, Novozyme 230 and crude α -galactosidase) to determine their effectiveness in hydrolysing galactooligosaccharides from soya bean and canola meal in the gastrointestinal tract of poultry. The use of the enzyme invertase to enhance galactoside hydrolysis was also studied. A wide range of α -galactosidase activity was observed in vitro, with crude α-galactosidase from Mortirella vinacea and Novozyme 230 preparation showing the highest activity values of 4.3 and 1.5 nkat mg^?1, respectively. All preparations with the exception of crude α-galactosidase showed invertase activity which is known to convert raffinose and stachyose to the corresponding di-and trisaccharide, melibiose and manninotriose. Although the activity of invertase was highest on sucrose, the Novozyme 230 preparation showed activity values of 4.2 and 2.3 nkat mg^?1 toward raffinose and stachyose substrates, respectively. De novo synthesis of raffinose was observed when soya bean meal, canola meal or pure sucrose and galactose were incubated with certain enzyme preparations (ie Energex). In general, preparations possessing hydrolytic activity towards galactooligosaccharides showed very little synthesis of raffinose while preparations capable of generating raffinose were very weak in the hydrolysis of galactooligosaccharides. The best result in terms of galactooligosaccharide in vitro hydrolysis of canola and soya bean meal was obtained with a combination of α-galactosidase and invertase. In the in vivo study with caecectomised hens, hydrolysis of galactooligosaccharides averaged 88% when crude α-galactosidase (2 g kg^?1) and invertase (1 g kg^?1) were added to laying, hen diet containing 200 g soya bean meal per kilogram. A problem identified in the current study was that minerals such as calcium phosphate and calcium carbonate common in poultry diets inhibit the hydrolysis activity of α-galactosidase, indicating that high levels of activity would be required to yield a response in practical poultry feeding.     

Pancreatic Alpha Amylase Hydrolysis Products of Modified and Unmodified Tapioca Starches

Three gelatinized tapioca starches [unmodified (A), hydroxypropyl distarch phosphate (B) and hydroxypropyl starch (C)] were hydrolyzed by hog pancreatic α-amylase (EC 3.2.1.1 α-1,4-glucan 4-glucanohydrolase). Oligosaccharide constituents of the hydrolyzates were separated by thinlayer chromatography and quantified by spectrodensitometry. Glucose, maltose, maltotriose and maltotetraose were identified by cochromatography. Hydrolyzates from starches B and C had lesser amounts of the lower molecular weight oligosaccharides (G₁—G₄) than did those from starch A. The products of hydrolysis varied quantitatively with the degree of hydrolysis.     

The mode of action on Granular Wheat Starch by Bacterial α-Amylase

Large (A) and small (B) granules from wheat starch were subjected to α-amylolysis. The B granules were solubilised faster than the A granules. The solubilised dextrins we separated from the enzyme before a secondary hydrolysis of the products occurred and then characterized. The size-distribution of the hydrolysis products ranged between a degree of polymerization of 2–500. The dextrins solubilised from the B granules contained somewhat more linear fragments and had smaller average chain length than the corresponding dextrins from the A granules. The composition of the residues of the A granules remained practically unchanged, whereas the B granules contained somewhat less amylose. Both granule types possessed extensive fragmentation of some granules, whereas other granules were virtually untouched by the enzyme.     

Effect of Pullulanase and α-Amylase on Hydrolysis of Waxy Corn Starch

Using commercial pullulanase, α-amylase and their mixture, partial hydrolysis of waxy corn starch was characterised for optimising production of maltodextrins free of D-glucose. Compared to pullulanase or α-amylase alone, the mixture of these two (simultaneous or successive addition) on the substrate enhanced the efficiency of maltodextrin turnover with low or traces of D-glucose production in a short time. D-glucose was removed from dextrins by membrane filtration and the yield of dextrin above DP6 was 60–65%.     

Affinity Binding of Higher Plant β-Amylases to Starch. A Rapid Purification Method

A rapid purification method exploiting affinity of higher plant β-amylases to its substrate starch is described. Mustard β-amylase on incubation with starch suspension binds rapidly to starch. The enzyme binds tenaciously to starch as various eluants as concentrated salt solutions, α-cyclodextrin and shift in elution pH could not significantly elute the bound enzyme. Even maltose only partially eluted the bound enzyme at high concentrations (5% w/v) after a prolonged incubation time (24 h). Nevertheless, the enzyme could be rapidly eluted from starch with white dextrin (1% w/v). The eluted enzyme fractions consisted of β-amylase purified to homogeneity. The above starch-affinity purification process could also be applied to other higher plant β-amylases such as sweet potato and barley.     

Comparative study of enzymatic hydrolysis of α/β- and γ-gliadins

Enzymatic hydrolysis of proteins and fractionation of hydrolysates is a route of diversifying their functional properties. Chymotryptic hydrolysis of different sulphur-rich gliadins (α/β- and γ-types), major wheat storage proteins, was studied. The peptides formed in the course of digestion were characterised by polyacrylamide gel electrophoresis in the presence of sodium dodecylsulfate (SDS-PAGE) and reversed-phase high performance liquid chromatography (RP-HPLC). With reference to previous work, a general scheme of degradation was assessed for γ-gliadins. Limited hydrolysis released two types of polypeptides, comprising respectively the repetitive and the non-repetitive moieties of the protein. In spite of strong sequence homologies between the two groups of sulphur-rich gliadins, it was not possible to prepare similar peptide fractions from α/β-gliadins. They were more resistant to hydrolysis and the region where the two domains merge appeared inaccessible to chymotrypsin. Restricted accessibility of cleavage sites was attributed to the less expanded conformation of α/β-type than γ-type gliadins. A first step of scaling-up was performed. This offers opportunities to prepare functional peptides from wheat storage proteins.     

Hydrolysis of lactose by a thermostable β-galactosidase immobilised on DEAE-cellulose

A method is described for the attachment of whole cells of Bacillus stearothermophilus to an ion-exchange support such as DEAE-cellulose by covalent linkage. This system enables full retention of the β-galactosidase activity of the cells. The enzyme activity immobilised in this way is extremely thermostable with a half-life of approximately 15 days at 60°C and pH 7. The pH optimum appears to be about 6.4 and the immobilised system hydrolyses lactose in dairy products such as whey and skim milk.     

Sweet taste and solution properties of α,α-trehalose

α,α-Trehalose, a naturally occurring non-reducing disaccharide (α, D-glucopyranosyl 1–1 α-D-glucopyranoside) is investigated by solution parameters and sensorial effects. Interactions between α, α-trehalose and water give rise to hydration effects which are measurable by intrinsic viscosity [n], apparent specific volume V°₂, and NMR relaxation times. Water-solute interactions are prime determinants of taste qualities. An interpretation of sweetness intensity and persistence of α,α-trehalose is therefore offered, based on its solution properties and its effect on water structure. From the results, it appears that α,α-trehalose undergoes a better packing among water molecules than other sugars. α,α-Trehalose is found to be less sweet but more persistent than sucrose, fructose, glucose or maltose.     

Hydrolysis of Maltoheptaose in Flow through Silicon Wafer Microreactors Containing Immobilised α‐Amylase and Glycoamylase

In this study a silicon micro immobilised enzyme reactor (μIMER) has been applied for hydrolysis of maltoheptaose as a model maltodextrin and starch using immobilised μ‐amylase (from Aspergillus oryzae) and glycoamylase (from Aspergillus niger). The influence of several parameters was investigated such as immobilisation chemistry, buffer constituents, pH, temperature, flow rate and substrate concentration. The conversion efficiency profile of the substrate was measured and the long‐term stability of the reactor was tested. For separation and detection of the formed hydrolysis products, high‐performance anion‐exchange chromatography with pulsed amperometric detection (HPAEC‐PAD) was used. The results show that the μIMERs can also be used for hydrolysis of starch and also additionally be connected directly on‐line with, e.g., liquid chromatography, making it possible to perform on‐line characterisation and analysis of starch hydrolysis products.     

Hydrothermal Modifications of Tropical Tuber Starches. 1. Effect of Heat‐Moisture Treatment on the Physicochemical,Rheological and Gelatinization Characteristics

Cassava, sweet potato and arrowroot starches have been subjected to heat‐moisture treatment (HMT) under different conditions using a response surface design of the variables. A comparative study was performed on the pasting properties, swelling behaviour and the gelatinization properties of the modified starches and also on the rheological and textural properties of their pastes. X‐ray diffraction studies have shown that cassava starch exhibited a slight decrease in crystallinity, whereas sweet potato and arrowroot starches showed an increase in crystallinity after HMT at 120ºC for 14 h with 20% moisture. The swelling volume was reduced and the solubility was enhanced for all three starches after HMT, but both effects were more pronounced in the case of arrowroot starch. The decrease in paste clarity of the starch after HMT was higher in the case of cassava and sweet potato starches. Viscosity studies showed that the peak viscosity of all three starches decreased after HMT, but the paste stability increased as seen from the reduced breakdown ratio and setback viscosity. Studies on rheological properties have shown that storage and loss moduli were higher for the starches heat‐moisture treated at higher moisture and lower temperature levels than the corresponding native starches. Storage of the gel at ‐20ºC resulted in a significant increase in storage modulus for all the three starches. All the textural parameters of the gels were altered after the treatment which depended on the nature of the starch and also the treatment condition.     

α 1,4 — α 1,6 Glucopolysaccharides Contained in Developing Maize Kernels

Corn grains with different filling times were fractionated in order to obtain their α 1,4 — α 1,6 glucopolysaccharide composition and structure. Sugary, waxy, flint and several hybrids were the varieties analyzed. There is an increase in the total content of polysaccharides, as the grain is completed. But, no differences in composition and structure were detected between the first sample analyzed (15th day after pollination) and the last one, which corresponds to the complete grain filling period. The methodology developed by us, allowed us to observe that the introduction of su character on the hybrids (F x S and S x F) has influence on the final polysaccharide structure. Also, in the F x W hybridα 1,4 — α 1,6 glucans, their structural characteristics were different from those of F or W pure.