Application of Protease and High Intensity Ultrasound in CornStarch Isolation from DegermedCornFlour

Application of Protease and High-Intensity Ultrasound in Corn Starch

Isolation from Degermed Corn Flour

Devon K. Cameron1 and Ya-Jane Wang1,2

ABSTRACT

Cereal Chem. 83(5):505–509

The conventional corn wet-milling process requires a long steeping time and has environmental and health concerns from the use of SO2. A recently proposed two-stage enzymatic milling procedure with the first stage of water soaking and coarse grinding of corn and the second stage of incubating with enzymes has been shown to reduce the soaking time and possibly eliminate the need for SO2 addition. This current work explored the applications of protease and high-intensity ultrasound in the second stage of the two-stage enzymatic milling for corn starch isolation to further shorten the process time without use of SO2. The starch yield from sonication alone was 55.2–67.8% (starch db) as compared with 53.4% of the water-only control with stirring for 1 hr and 71.1% of the conventional control with SO2 and lactic acid steeping for 48 hr. Protease digestion alone for 2 hr was not effective (45.8–63.9% yield) in isolating corn starch, but the starch recovery was increased to 61.2–76.1% when protease was combined with sonication. The preferred combination was neutral protease digestion for 2 hr followed by sonication at 75% ampli-tude for 30 min. The results demonstrated that combinations of high-intensity ultrasound and neutral protease could replace SO2 and shorten the steeping time in the enzymatic wet-milling process for corn starch isolation.

The conventional corn wet-milling process involves the soak-ing of corn kernels in an aqueous solution containing 0.1–0.2% (w/v) SO2 and 0.5–1.5% (v/v) lactic acid at 45–55°C for 24–40 hr (Shandera and Jackson 1996). Because the pericarp creates a barrier to the diffusion of water and SO2 (Syarief et al 1987; Eck-hoff and Okos 1989; Ruan et al 1992), the long steeping time is required to achieve sufficient release of starch granules from the protein matrix. The SO2 provides a combination of antimicrobial, softening, and protein-dispersing characteristics that are essential for high starch yields; however, it also causes environmental and health concerns. Additionally, the long steeping time and use of chemicals have been shown to affect starch properties. For exam-ple, lactic acid can have an acid-thinning effect on starch granules, which can reduce pasting viscosities (Shandera and Jackson 1996; Pérez et al 2001). Reducing the steeping time could lower pro-duction and energy cost, increase productivity, and lessen the changes of starch properties.

Enzymes, such as proteases and cellulases, have been evaluated in the conventional corn wet-milling steeping process to reduce the steeping time and to further improve starch yield (Hassanean and Abdel-Wahed 1986; Caransa et al 1988; Steinke and Johnson 1991; Steinke et al 1991; Moheno-Perez et al 1999). These studies showed small but significant improvements over the conventional wet-milling with the addition of high doses of enzyme in addition to SO2 during steeping. Recently, Johnston and Singh (2001, 2004), Singh and Johnston (2002), and Johnston et al (2003) demonstrated that enzymatic milling could reduce soaking time and possibly eliminate the need for SO2 addition. They proposed a two-stage procedure with the first stage of water soaking and coarse grinding of corn and the second stage of incubating with enzymes. The grinding of hydrated corn kernels for size reduction removed the diffusion barriers because enzymes were not able to penetrate the kernels and break down the protein matrix sur-rounding starch granules (Singh and Johnston 2004). The enzyme diffusion rate increased in the hydrated ground corn, and the overall steep time was reduced to 4–6 hr. Proteases were more effective in starch recovery compared with other types of enzymes.

High-intensity ultrasound, which uses large power levels (10–1,000 W/cm–2 range), has been effective in isolating rice starch from rice flour both alone and in combination with neutral protease in <3 hr (Wang and Wang 2004a,b). Rice flour treated with sonication at 75% amplitude (750W, 20 kHz) for 30 min and combinations of neutral protease and sonication produced signifi-cantly higher rice starch yields of 74.1–76.2% and 79.8–86.7% (starch db), respectively, compared with 71.6% from the conven-tional alkaline steeping method. The isolated rice starch from treatments combining neutral protease and sonication displayed similar gelatinization properties as measured by differential scan-ning calorimetry but slightly different pasting properties as measured by a Rapid Visco-Analyser when compared with the alkali-iso-lated treatments. Zhang et al (2005) tested the use of ultrasound to recover starch from degermed corn flour and hominy feed and reported significantly higher starch yields with sonication than with the control of water stirring only.

The objective of this study was to evaluate protease and ultra-sound as alternatives in the second stage of the enzymatic milling process to further shorten the soaking time without the usage of SO2. Degermed corn flour was used as the model system to better compare the effectiveness of protease and sonication on corn starch isolation.

MATERIALS AND METHODS

Materials

Degermed yellow corn flour was purchased from ADM Milling (Milwaukee, WI). A high-intensity ultrasonic processor (750W, model, 20 kHz) with a three-quarter inch high gain probe was pur-chased from Sonics and Materials (Newtown, CT). Acid casein (purity 99.9%) was purchased from New Zealand Milk Products North America (Santa Rosa, CA). L-Tyrosine and trichloroacetic acid were purchased from EMD Chemicals (Gibbstown, NJ). Folin’s reagent was purchased from Sigma-Aldrich (St. Louis, MO). Sodium hydroxide, sodium bisulfite, and phosphoric acid were purchased from J.T. Baker (Phillipsburg, NJ).

Three types of proteases, provided by Amano Pharmaceutical (Nagoya, Japan) were studied. Neutral protease, N “Amano”, in the dry powder form is from Bacillus subtilis with protease activity ≥150,000 units/g, optimum pH 7.0, and 55°C. Alkaline protease, P “Amano” 6, in the dry powder form is from Apergillus melleus with protease activity ≥60,000 units/g, optimum pH 8.0, and 45°C. Acid protease, “A”, in dry powder form is from A. niger with protease activity ≥35,000 units/g, optimum pH 2.5, and 55°C. Three levels from each protease were evaluated at pH 7.0 and 50°C, and the selected amounts for neutral protease were 0.01, 0.03, and 0.05, which corresponded to activities of 1,500,

1 Department of Food Science, University of Arkansas, Fayetteville, AR 72704.

2 Corresponding author. Phone: 479-575-3871. Fax: 479-575-6936. E-mail:

yjwang@https://www.sodocs.net/doc/2c5476763.html,

DOI: 10.1094/CC-83-0505

? 2006 AACC International, Inc.

Vol. 83, No. 5, 2006 505

4,500, and 7,500 units/g of flour (as-is basis), respectively. Selec-ted amounts and activities chosen for alkaline and acid protease were slightly higher than those of neutral protease because the incubation pH was not the optimum pH for either enzyme. Starch Isolation

Controls. A conventional control was conducted by treating corn flour with SO2 and lactic acid, which are used in the conven-tional corn wet-milling process. Degermed corn flour (100 g, as-is) was steeped in 200 g of deionized water with 0.5% (w/w) lactic acid, and 0.2% (w/w) SO2 (as sodium bisulfite) at 50°C for 48 hr.

A water-only control was also included for comparison by stirring the same amount of flour slurry at room temperature for 1 hr. After the steeping, the flour slurry was milled using a homemade centri-fugal mill, passed through a 63-μm screen, and centrifuged at 1,400 ×g for 10 min. The centrifugal mill consisted of a cone-shaped rotor and stator to regulate the shear gap to produce intense friction on the flour for size reduction. The soft, top yellowish protein layer was carefully removed with a spatula, and the bottom starch layer was reslurried. This purification process of reslurring, centrifugation, and protein removal was repeated two more times. The purified starch was dried in a forced-air oven at 40°C for 48 hr, ground using a mortar and pestle, passed through a 150-μm sieve, and stored in a plastic jar at room temperature. The starch yield was calculated as the amount of starch recovered after drying by the amount of starch present in the degermed corn flour.

High-intensity ultrasound. Three factors were studied for starch isolation by high-intensity ultrasound: sonication amplitude, soni-cation duration, and temperature. Deionized water (200 g) was warmed to 30 or 42°C in a 500-mL reaction beaker by a circulator before the addition of the corn flour (100 g, as-is). The corn flour was stirred for 5 min before sonication began. The amplitude is related to the energy content, the greater the amplitude, the greater the distance the probe tip travels. The 100% amplitude setting for the three-quarter inch high gain probe used in this study was 61 μm. The 6.5-cm probe tip was placed ≈3 cm deep into the starch slurry. The sonication amplitude was set at 25, 50, or 75% with a pulsed time of 5-sec on and 5-sec off. The sonication duration was 15, 30, or 60 min, excluding the off time of pulsing soni-cation. The corresponding total time of sonication would be 30, 60, and 120 min, respectively. The maximum sample temperature was maintained at 40 or 50°C by the circulator and monitored by a temperature probe. After the treatment, the same procedure was followed for wet-milling, centrifugation, protein removal, drying, and storage as described above.

Protease treatment. Acidic, neutral, and alkaline proteases at concentrations of 0.01–0.25% (flour as-is) were applied to the corn flour (100 g, as-is) at 50°C for 2 hr with constant stirring to evaluate their effectiveness in isolating corn starch. Neutral protease at 0.03% was selected to be studied in combination with soni-cation because it produced the highest starch yield. Combinations of protease and sonication. Three factors were studied for starch isolation from corn flour by combining sonica-tion and protease: sonication duration, sonication amplitude, and sequence of application. The sonication amplitude was set at 25, 50, or 75% with 5 sec on and 5 sec off, and the maximum sample temperature was controlled at 50°C by the circulator. The soni-cation duration was set for 15, 30, or 60 min, which included only the on time. Sonication was applied before, during, or after protease digestion. Corn flour (100 g, as-is) was mixed with deionized water (200 g) in the reaction beaker. Neutral protease of 0.03% (w/w, flour as-is) was added to the corn flour at 50°C with constant stirring for 2 hr either before or after sonication at 50 or 75% for 15 or 30 min of on time. When sonication was applied during protease digestion, the total treatment duration, including both on and off time, was 60 or 120 min for 25% amplitude and 30 or 60 min for 50% amplitude. The 75% amplitude was not employed when sonication was used during protease digestion to avoid potential inactivation of protease. Wang and Wang (2004b) reported that simultaneous sonication and protease digestion gave slightly lower starch yield possibly due to shorter reaction time or protease inactivation by sonication. After the treatment, the same procedure was followed for wet-milling, centrifugation, drying, and storage as before. Duplicates were performed for each control and experimental starch isolation sample.

Chemical Composition and Physicochemical Properties

of Isolated Starch

The moisture, protein, damaged starch, and total starch contents of the isolated starches were determined in duplicate following Approved Methods (AACC 2000). Samples (2 g) were placed in aluminum moisture dishes and dried at 130°C in a convection oven for 60 min according to Approved Method 44-15A. Crude protein was measured by micro-Kjeldahl according to Approved Method 46-13. Damaged starch content was determined using the spectrophotometric method of the Megazyme Starch Damage kit according to Approved Method 76-31. Total starch content was determined following the Megazyme Amyloglucosidase/α-Amylase Method according to Approved Method 76-13.

The pasting characteristics were measured in duplicate at 7.5% (w/w) concentration using a Micro ViscoAmyloGraph (C.W. Brabender Instruments, South H ackensack, NJ) equipped with a 300-cmg cartridge and operated at a speed of 250 rpm. The starch slurry was heated from 50 to 95°C at a rate of 7°C/min, held at 95°C for 5 min, and cooled down to 50°C at a rate of 7°C/min. The breakdown viscosity is the peak minus trough viscosity, and the total setback is the final minus trough viscosity. The gela-tinization properties were assessed in duplicate using differential scanning calorimetry (DSC) (model Pyris-1, Perkin-Elmer, Nor-walk, CT). Starch (≈4 mg, db) was weighed accurately into an alu-minum DSC pan and then moistened with 8 μL of DI water using a microsyringe. The pan was hermetically sealed and allowed to stand for at least 1 hr before thermal analysis. Samples were heated from 25 to 130°C at a rate of 10°C/min. Enthalpy, onset, peak, and end temperatures were computed automatically. The scan-ning electron micrographs of isolated starches were taken with an XL30 ESEM (environmental scanning electron microscope) (FEI Corporation, Eindhoven, The Netherlands) at an accelerating voltage of 10 kV. Starch granules were sprinkled onto double-backed cellophane tape attached to a stub before coating with gold-palladium.

Residual Protease Activity

The residual protease activity in the isolated starch was assayed following the procedure provided by Amano Pharmaceutical (Na-goya, Japan). Milk casein was used as the substrate for protease assay and prepared by heating 1.50 g of milk casein in 25 mL of 0.1M NaOH in a water bath at 90–95°C for 10 min. The solution was cooled to room temperature and adjusted to pH 7.0 with 0.033M phosphoric acid. Then 20 mL of 0.1M phosphate buffer (pH 7.0) was added and the solution was diluted to 100 mL. The neutral protease used in this study was diluted 60,000 times for activity measurement. Starch samples (1 g) were mixed with water to a final volume of 5 mL, and the protein content in the starch was used to determine the dilution factor to calculate the protease activity. A calibration curve was prepared with tyrosine at 0, 10, 20, 30, 40, and 50 μg/mL in 0.1M H Cl. Tyrosine standard solution (1 mL) was added to 5 mL of 0.4M Na2CO3 and 1 mL of undiluted (fivefold) Folin’s reagent. The solution was mixed and maintained at 37°C for 20 min; thereafter the absorbance was measured at 660 nm. The standard curve was constructed by plotting tyrosine concentration versus absorbance, and the slope was determined. For protease activity assay, 1 mL of casein substrate solution equilibrated at 37°C for 10 min was added with 1 mL of neutral protease solution or the supernatant from the starch

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slurries and incubated at 37°C for 60 min. Two blanks were included with one containing 1 mL of DI water and 1 mL of 60,000-fold diluted neutral protease solution but no substrate, and the other containing 1 mL of DI water and 1 mL of the super-natant from the starch slurry without substrate. At the end of incu-bation, 2 mL of 0.4M trichloroacetic acid was added, the solution stood for 25 min, and then it was filtered through a filter paper (Whatman No. 42) to remove the precipitate. To 1 mL of each filtrate, 5 mL of 0.4M sodium carbonate and 1 mL of undiluted (fivefold) Folin’s reagent were added. The solutions were mixed and stood at 37°C for 20 min before the absorbance was measured at 660 nm. One unit of protease activity is defined as the quantity of the enzyme to produce amino acid equivalent to 100 μg of tyrosine in 1 mL of filtrate under the conditions of the assay. Protease activity = (absorbance of sample – absorbance of both blanks) × (slope of the tyrosine standard curve) × (dilution factor of enzyme or protein in starch) × (1/100).

Statistical Analysis

Experimental data were analyzed by using the GLM procedure (SAS Institute, Cary, NC), and Duncan’s multiple range was used to compute the least significance differences at P < 0.05.

RESULTS AND DISCUSSION

Ultrasonic Treatments

The degermed corn flour used in the present study contained 5.9% protein, 67.9% total starch, and 2.35% damaged starch on a dry-weight basis. The starch yield, residual protein content, damaged starch content, and pasting properties of the isolated starches from the treatments of conventional control, water-only control, and high-intensity ultrasound alone are listed in Table I. The conventional control with 48 hr of steeping produced the highest starch yield but also the highest damaged starch content. The water-only control had the lowest starch yield and damaged starch content. The starch yield, residual protein, and damaged starch content of sonicated samples were 55.2–67.8%, 0.20–0.79% and 0.64–1.15% (db), respectively. When the sonication amplitude and duration increased, the starch yield was significantly improved, and the residual protein content was notably decreased under the same treatment temperature. The starch yield was not affected by the temperature (40 or 50°C), but the protein and damaged starch

contents varied with treatment temperature. In general, the residual protein content decreased with increasing sonication amplitude, duration, and temperature. H owever, the opposite trend was ob-served for the damaged starch content, presumably because a higher temperature coupled with a higher amplitude and a longer duration resulted in more damage to the starch granules. Similar trends were also observed for sonication-assisted isolation of rice starch reported earlier (Wang and Wang 2004a). The sonication treatment with 75% amplitude at 50°C for 30 min produced a comparable starch yield but a lower residual protein and damaged starch content as compared with the conventional control.

Zhang et al (2005) also observed significantly higher starch yields when corn flour was treated with ultrasound (100% ampli-tude, 20 kHz) than with water only for the same reaction time (30 min); however, they did not include a SO 2 control. They reported much higher starch yields than the present study, which was as-cribed to the different methods used to separate protein from starch. Zhang et al (2005) used the tabling procedure described in Eckhoff et al (1996), whereas centrifugation was used in this study, by which more starch was lost to the protein fraction. Sig-nificantly higher starch yields relative to the conventional control was observed in rice starch recovery from rice flour (Wang and Wang 2004a) compared with the present study using the same sonication conditions, suggesting that differences exist between corn and rice flours in terms of interactions between starch and protein or susceptibility of protein to sonication.

TABLE I

Starch Yield, Protein Content, Damaged Starch Content, and Pasting Properties of Corn Starch Isolated by Different Methods a

Starch Yield Protein Damaged Starch Viscosity (BU)

Treatment

(% starch db)

(% flour db)

(% flour db)

Peak

Breakdown

Final

Total Setback

Conventional control b 71.1a 0.33h 1.22a 570ab 183a–c 737cd 348c Water-only control c 53.4f 0.56d 0.59h 599a 185ab 859ab 445a 40°C U30m25%amp d 55.6ef 0.78a 0.99d 481d 137f 739cd 395b U60m25%amp 60.1de 0.76a 0.97de 596a 138f 864a 406b U15m50%amp 61.6cd 0.79a 0.93ef 536bc 166de 701d–f 331cd U30m50%amp 62.3cd 0.64c 0.67h 589a 187ab 756c 354c U15m75%amp 63.8b–d 0.54de 0.77g 559ab 142f 810b 393b U30m75%amp 64.0b–d 0.34h 0.81g 575ab 184ab 744cd 353c 50°C U30m25%amp 55.2ef 0.78a 0.64h 500cd 151ef 653ef 304de U60m25%amp 63.0b–d 0.52ef 0.97de 541bc 163de 726cd 348c U15m50%amp 59.9de 0.71b 0.81g 557ab 198a 651f 292e U30m50%amp 63.1b–d 0.50f 0.95de 559ab 179b–d 719cd 339c U15m75%amp 65.3bc 0.40g 1.07c 570ab 177b–d 729cd 336c U30m75%amp 67.8ab 0.20i 1.15b 538bc 167c–e 706c–e 335c

a Values followed by the same letter in the same column are not significantly different (P < 0.05).

b Steeping with 0.2% (w/w) SO

2 solution and 0.5% (w/w) lactic acid at 50oC for 48 hr. c Steeping in water with stirring at room temperature for 1 hr. d U, ultrasound, m, minute, amp, amplitude.

TABLE II

Starch Yield of Corn Starch Isolated by Different Proteases

at Various Concentrations at 50°C for 2 hr a

Treatment

Activity (U) Starch Yield (% starch, db)

0.05% Acid protease 1,750 47.4d 0.15% Acid protease 5,250 46.9d 0.25% Acid protease 8,750 57.9bc 0.01% Neutral protease 1,500 54.3c 0.03% Neutral protease 4,500 63.9a 0.05% Neutral protease 7,500 58.4b 0.03% lkaline protease 1,800 47.3d 0.09% Alkaline protease 5,400 58.2bc 0.15% Alkaline protease 9,000

45.8d

a Values followed by the same letter in the same column are not significantly

different (P < 0.05).

508 CEREAL CHEMISTRY

The improved starch yield and increased damaged starch content for the samples treated with sonication relative to the water-only control imply that the acoustic cavitation of high-intensity ultrasound disrupted the protein matrix or the interactions between protein and starch, which helped starch recovery. At the same time, some starch granules were damaged from exposure to sonication. It was observed that separation of protein and starch fractions became easier after 30 or 60 min of sonication.

The isolated starch from the conventional control treatment showed a reduction in peak, final, and total setback viscosities rela-tive to the water-only control, agreeing with Shandera and Jackson (1996) and Perez et al (2001). In their studies, the physicochemical properties of the isolated starch were affected as a result of the annealing effect from the steeping conditions. The sonicated starch samples displayed similar pasting properties as the conventional control but lower final and total setback viscosities when compared with the water-only control. There was no clear trend among different treatments in terms of pasting properties.

For gelatinization properties, the onset temperature, peak temper-ature, and enthalpy of the isolated starch from the water-only treatment were 66.2°C, 72.2°C, and 10.9 J/g, respectively, whereas those of the isolated starch from the conventional control were 71.7°C, 74.8°C, and 10.6 J/g, respectively. The increased gelatin-ization temperatures were attributed to the annealing effect as

TABLE III

Starch Yield, Protein Content, Damaged Starch Content, and Pasting Properties of Corn Starch Isolated

by Different Combinations of Protease and Sonication a

Starch Yield Protein Damaged Starch Viscosity (BU)

Treatment

(% starch db)

(% flour db)

(% flour db)

Peak

Breakdown

Final

Total Setback

Conventional control b 71.1b–d 0.33hi 1.22b–e 570b 183ab 737b 348b

Water-only control c 53.4g 0.56a 0.59f 599a 185ab 859b 445a

U15min50%amp-P2h d 61.2f 0.47b 1.14e 545b 170b–e 696bc 321b U30min50%amp-P2h 68.4c–e 0.36fg 1.32bc 545b 169b–e 709bc 333b U15min75%amp-P2h 65.2ef 0.37ef 1.31b–d 547b 166c–e 703bc 322b U30min75%amp-P2h 74.2ab 0.30ij 1.20c–e 569b 179a–c 727bc 337b PU30min25%amp e 72.0bc 0.46bc 1.15de 544b 181a–c 680c 317b PU60min25%amp 73.2ab 0.40d 1.24b–e 568b 187a 716bc 335b PU15min50%amp 67.6de 0.43c 1.22b–e 566b 175a–d 710bc 319b PU30min50%amp 66.7e 0.39de 1.22b–d 561b 178a–d 712bc 329b P2h-U15min50%amp f 67.5de 0.34gh 1.24b–e 556b 174a–d 720bc 338b P2h-U30min50%amp 67.3e 0.29j 1.52a 547b 162de 727bc 342b P2h-U15min75%amp 71.4bc 0.25k 1.37b–e 544b 157e 724bc 337b P2h-U30min75%amp 76.1a 0.24k 1.52a 563b 177a–d 736b 350b

a Values followed by the same letter in the same column are not significantly different (P < 0.05).

b Steeping with 0.2% (w/w) SO

2 solution and 0.5% (w/w) lactic acid at 50°C for 48 hr. c Steeping in water with stirring at room temperature for 1 hr.

d Sonication 15 min at 50% amplitud

e and then protease digestion for 2 hr. e Protease digestion and sonication 30 min at 25% amplitude concurrently. f

Protease digestion 2 hr and then sonication 15 min at 50% amplitude.

Fig. 1. Scanning electron micrographs of corn starch isolated by conventional control (A ), water-only control (B ), sonication at 75% amplitude and 40°C for 30 min (C ), protease digestion for 2 hr followed by sonication at 75% amplitude for 30 min (D ).

observed in the pasting properties. The gelatinization properties of the sonicated starch were similar to those from the water-only control, confirming the effect of annealing on starch properties. Treatments Combining Protease and Sonication

Proteases of different types (acidic, neutral, and alkaline) at different concentrations based on a similar range of activity were compared to select the best protease and concentration to be com-bined with sonication. The results showed that protease alone was not effective in improving corn starch isolation under the condi-tions with stirring at 50°C for 2 hr (Table II). Neutral protease at 0.03% was more effective in assisting starch isolation producing a starch yield of 63.6%, which was nevertheless much lower than the conventional control of 71.1%. Previously neutral protease at 0.03 or 0.05% was effective in isolating rice starch from rice flour, which produced a similar starch yield as the conventional alkaline steeping method (Wang and Wang 2004b).

Table III presents the starch yield, residual protein content, damaged starch content, and pasting properties of the corn starch isolated by combining 0.03% neutral protease with different soni-cation conditions. With increased sonication amplitude and duration, starch yield was significantly improved, residual protein content was greatly decreased, and damaged starch content was slightly increased, with the exception of the treatments where sonication and protease were employed together. The damaged starch content for all treatments was similar to or slightly higher than the con-ventional control of 1.22%. With simultaneous sonication and protease, treatments with 25% amplitude produced higher starch yields than treatments with 50% amplitude. These results indicate that the protease was possibly partially inactivated from exposure to higher intensity (50%) sonication, resulting in a lower starch yield. The protease digestion treatment followed by sonication at 75% amplitude for 30 min produced a higher starch yield (76.0%) than the conventional method (71.1%). Previously, combinations of protease and sonication produced starch yields 8–15% higher than the conventional method (Wang and Wang 2004b). The much improved starch yield could not be achieved for corn starch isolation with combinations of protease and sonication, probably because the majority of corn protein, zein, is hydrophobic, and protein-starch interaction is stronger in corn flour than in rice flour. The starch isolated by combining protease and sonication gen-erally displayed peak, breakdown, final, and total setback viscosi-ties similar to the starch isolated from the conventional control. The gelatinization properties of the starch isolated from the combi-nations protease and sonication had ranges of 66.2–68.7°C for onset temperature, 71.7–72.8°C for peak temperature, and 11.6-12.4 J/g for enthalpy, which were similar to those of the starch from the water-only control except a slight higher enthalpy values. The residual protease activity in the isolated starch samples was determined to ensure most protease was washed out during the process. The residual protease activity in isolated starches from all treatments had a range of 0.63–2.32 units/g of starch based on the equation described previously. This low residual protease activity probably would not cause adverse effects if the isolated starch is to be incorporated in most food systems.

Starch Morphology from Different Treatments

The micrographs of starch from selective treatments as revealed by ESEM are shown in Fig. 1. No noticeable difference in starch appearance was observed among the different treatments, indica-ting the conditions used in the present study did not result in any change in starch surface structure.

CONCLUSIONS

High-intensity ultrasound demonstrated the capability of isola-ting starch without causing undue starch damage within a short period of time. Combinations of neutral protease and sonication were most effective in isolating starch from degermed corn flour with low residual protein, damaged starch, and protease activity. The preferred combination was neutral protease digestion for 2 hr followed by sonication at 75% amplitude for 30 min. The results of this study suggest that use of SO2 can be eliminated, and the steeping process can be further shortened in the enzymatic milling process when combined with protease and sonication. The combi-nation of protease and sonication can be incorporated in the second stage of enzymatic milling to increase the productivity and lessen changes of starch properties from the traditional wet-milling process.

ACKNOWLEDGMENTS

Financial support received under USDA CSREES Award No. 2003-35503-12486 is gratefully acknowledged. We thank Linfeng Wang for assistance with scanning electron microscopy.

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Syarief, A. M., Gustafson, R. J., and Morey, R. V. 1987. Moisture diffusion coefficients for yellow dent corn components. Trans. ASAE 30:522-528. Wang, L., and Wang, Y.-J. 2004a. Application of high-intensity ultrasound and surfactants in rice starch isolation. Cereal Chem. 81:140-144. Wang, L., and Wang, Y.-J. 2004b. Rice starch isolation by neutral protease and high-intensity ultrasound. J. Cereal Sci. 39:291-296.

Zhang, Z., Feng, H., Niu, Y., and Eckhoff, S. R. 2005. Starch recovery from degermed corn flour and hominy feed using power ultrasound. Cereal Chem. 82:447-449.

[Received October 10, 2005. Accepted May 5, 2006.]

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英语中的比较级与最高级 详解

比较级与最高级 1.as...as 与(not) as(so)...as as...as...句型中，as的词性 第一个as是副词，用在形容词和副词的原级前，常译为“同样地”。第二个as是连词，连接与前面句子结构相同的一个句子(相同部分常省略)，可译为“同..... He is as tall as his brother is (tall) . (后面的as 为连词) 只有在否定句中，第一个as才可换为so 改错: He is so tall as his brother.（X） 2.在比较状语从句中，主句和从句的句式结构一般是相同的 与as...as 句式中第二个as一样，than 也是连词。as和than这两个连词后面的从句的结构与前面的句子大部分情况下结构是相同的，相同部分可以省略。 He picked more apples than she did. 完整的表达为: He picked more apples than she picked apples. 后而的picked apples和前面相同，用did 替代。 He walked as slowly as she did.完整表达为: He walked as slowly as she walked slowly. she后面walked slowly与前面相同，用did替代。

3.谓语的替代 在as和than 引导的比较状语从句中，由于句式同前面 主句相同，为避免重复，常把主句中出现而从句中又出现的动词用do的适当形式来代替。 John speaks German as fluently as Mary does. 4.前后的比较对象应一致 不管后面连词是than 还是as,前后的比较对象应一致。The weather of Beijing is colder than Guangzhou. x than前面比较对象是“天气”，than 后面比较对象是“广州”，不能相比较。应改为: The weather of Bejing is colder than that of Guangzhou. 再如: His handwriting is as good as me. 应改为: His handwriting is as good as mine. 5.可以修饰比较级的词 常用来修饰比较级的词或短语有: Much,even,far,a little,a lot,a bit,by far,rather,any,still,a great deal等。 by far的用法: 用于强调，意为“...得多”“最最...”“显然”等，可修饰形容词或副词的比较级和最高级，通常置于其后，但是若比较级或最高级前有冠词，则可置于其前或其后。

The way常见用法

The way 的用法 Ⅰ常见用法： 1)the way+ that 2)the way + in which（最为正式的用法） 3)the way + 省略（最为自然的用法） 举例：I like the way in which he talks. I like the way that he talks. I like the way he talks. Ⅱ习惯用法： 在当代美国英语中，the way用作为副词的对格，“the way+ 从句”实际上相当于一个状语从句来修饰整个句子。 1)The way =as I am talking to you just the way I’d talk to my own child. He did not do it the way his friends did. Most fruits are naturally sweet and we can eat them just the way they are—all we have to do is to clean and peel them. 2）The way= according to the way/ judging from the way The way you answer the question, you are an excellent student. The way most people look at you, you’d think trash man is a monster. 3）The way =how/ how much No one can imagine the way he missed her. 4）The way =because

人教版(新目标)初中英语形容词与副词的比较级与最高级

人教版（新目标）初中英语形容词与副词的比较级与最高级 （一）规则变化： 1．绝大多数的单音节和少数双音节词，加词尾-er ，-est tall—taller—tallest 2．以不发音的e结尾的单音节词和少数以-le结尾的双音节词只加-r，-st nice—nicer—nicest , able—abler—ablest 3．以一个辅音字母结尾的重读闭音节词或少数双音节词，双写结尾的辅音字母，再加-er，-est big—bigger—biggest 4．以辅音字母加y结尾的双音节词，改y为i再加-er，-est easy—easier—easiest 5．少数以-er，-ow结尾的双音节词末尾加-er，-est clever—cleverer—cleverest, narrow—narrower—narrowest 6．其他双音节词和多音节词，在前面加more，most来构成比较级和最高级 easily—more easily—most easily （二）不规则变化 常见的有： good / well—better—best ; bad (ly)/ ill—worse—worst ; old—older/elder—oldest/eldest many / much—more—most ; little—less—least ; far—farther/further—farthest/furthest

用法： 1．原级比较：as + adj./adv. +as（否定为not so/as + adj./adv. +as）当as… as中间有名字时，采用as + adj. + a + n.或as + many / much + n. This is as good an example as the other is . I can carry as much paper as you can. 表示倍数的词或其他程度副词做修饰语时放在as的前面 This room is twice as big as that one. 倍数+as+adj.+as = 倍数+the +n.+of Your room is twice as larger as mine. = Your room is twice the size of mine. 2．比较级+ than 比较级前可加程度状语much, still, even, far, a lot, a little, three years. five times,20%等 He is three years older than I (am). 表示“（两个中）较……的那个”时，比较级前常加the（后面有名字时前面才能加冠词） He is the taller of the two brothers. / He is taller than his two brothers. Which is larger, Canada or Australia? / Which is the larger country, Canada or Australia? 可用比较级形式表示最高级概念，关键是要用或或否定词等把一事物（或人）与其他同类事物（或人）相分离 He is taller than any other boy / anybody else.

英语中的比较级和最高级

大多数形容词有三种形式,原级,比较级和最高级, 以表示形容词说明的性质在程度上的不同。 形容词的原级: 形容词的原级形式就是词典中出现的形容词的原形。例如: poor tall great glad bad 形容词的比较级和最高级: 形容词的比较级和最高级形式是在形容词的原级形式的基础上变化的。分为规则变化和不规则变化。 规则变化如下: 1) 单音节形容词的比较级和最高级形式是在词尾加 -er 和 -est 构成。 great (原级) (比较级) (最高级) 2) 以 -e 结尾的单音节形容词的比较级和最高级是在词尾加 -r 和 -st 构成。wide (原级) (比较级) (最高级) 3)少数以-y, -er, -ow, -ble结尾的双音节形容词的比较级和最高级是在词尾加 -er 和 -est 构成。 clever(原级) (比较级) (最高级) 4) 以 -y 结尾,但 -y 前是辅音字母的形容词的比较级和最高级是把 -y 去掉,加上 -ier 和-est 构成. happy (原形) (比较级) (最高级) 5) 以一个辅音字母结尾其前面的元音字母发短元音的形容词的比较级和最高级是双写该辅音字母然后再加 -er和-est。 big (原级) (比较级) (最高级) 6) 双音节和多音节形容词的比较级和最高级需用more 和 most 加在形容词前面来构成。 beautiful (原级) (比较级) (比较级) difficult (原级) (最高级) (最高级) 常用的不规则变化的形容词的比较级和最高级: 原级------比较级------最高级 good------better------best many------more------most much------more------most bad------worse------worst far------farther, further------farthest, furthest 形容词前如加 less 和 least 则表示"较不"和"最不 形容词比较级的用法: 形容词的比较级用于两个人或事物的比较,其结构形式如下: 主语+谓语(系动词)+ 形容词比较级+than+ 对比成分。也就是, 含有形容词比较级的主句+than+从句。注意从句常常省去意义上和主句相同的部分, 而只剩下对比的成分。

The way的用法及其含义(二)

The way的用法及其含义（二） 二、the way在句中的语法作用 the way在句中可以作主语、宾语或表语： 1.作主语 The way you are doing it is completely crazy.你这个干法简直发疯。 The way she puts on that accent really irritates me. 她故意操那种口音的样子实在令我恼火。The way she behaved towards him was utterly ruthless. 她对待他真是无情至极。 Words are important, but the way a person stands, folds his or her arms or moves his or her hands can also give us information about his or her feelings. 言语固然重要,但人的站姿,抱臂的方式和手势也回告诉我们他(她)的情感。 2.作宾语 I hate the way she stared at me.我讨厌她盯我看的样子。 We like the way that her hair hangs down.我们喜欢她的头发笔直地垂下来。 You could tell she was foreign by the way she was dressed. 从她的穿著就可以看出她是外国人。 She could not hide her amusement at the way he was dancing. 她见他跳舞的姿势，忍俊不禁。 3.作表语 This is the way the accident happened.这就是事故如何发生的。 Believe it or not, that's the way it is. 信不信由你, 反正事情就是这样。 That's the way I look at it, too. 我也是这么想。 That was the way minority nationalities were treated in old China. 那就是少数民族在旧中

英语比较级和最高级的用法归纳

英语比较级和最高级的用法归纳 在学习英语过程中，会遇到很多的语法问题，比如比较级和最高级的用法，对于 这些语法你能够掌握吗？下面是小编整理的英语比较级和最高级的用法，欢迎阅读！ 英语比较级和最高级的用法 一、形容词、副词的比较级和最高级的构成规则 1.一般单音节词和少数以-er，-ow结尾的双音节词，比较级在后面加-er，最高级 在后面加-est; (1)单音节词 如：small→smaller→smallest short→shorter→shortest tall→taller→tallest great→greater→greatest (2)双音节词 如：clever→cleverer→cleverest narrow→narrower→narrowest 2.以不发音e结尾的单音节词，比较在原级后加-r，最高级在原级后加-st; 如：large→larger→largest nice→nicer→nicest able→abler→ablest 3.在重读闭音节(即：辅音+元音+辅音)中，先双写末尾的辅音字母，比较级加-er，最高级加-est; 如：big→bigger→biggest hot→hotter→hottest fat→fatter→fattest 4.以“辅音字母+y”结尾的双音节词，把y改为i，比较级加-er，最高级加-est; 如：easy→easier→easiest heavy→heavier→heaviest busy→busier→busiest happy→happier→happiest 5.其他双音节词和多音节词，比较级在前面加more，最高级在前面加most; 如：bea utiful→more beautiful→most beautiful different→more different→most different easily→more easily→most easily 注意：(1)形容词最高级前通常必须用定冠词 the，副词最高级前可不用。 例句： The Sahara is the biggest desert in the world. (2) 形容词most前面没有the，不表示最高级的含义，只表示"非常"。 It is a most important problem. =It is a very important problem.

(完整版)the的用法

定冠词the的用法： 定冠词the与指示代词this ,that同源,有“那(这)个”的意思,但较弱,可以和一个名词连用,来表示某个或某些特定的人或东西. (1)特指双方都明白的人或物 Take the medicine.把药吃了. (2)上文提到过的人或事 He bought a house.他买了幢房子. I've been to the house.我去过那幢房子. (3)指世界上独一无二的事物 the sun ,the sky ,the moon, the earth (4)单数名词连用表示一类事物 the dollar 美元 the fox 狐狸 或与形容词或分词连用,表示一类人 the rich 富人 the living 生者 (5)用在序数词和形容词最高级,及形容词等前面 Where do you live?你住在哪? I live on the second floor.我住在二楼. That's the very thing I've been looking for.那正是我要找的东西. (6)与复数名词连用,指整个群体 They are the teachers of this school.(指全体教师) They are teachers of this school.(指部分教师) (7)表示所有,相当于物主代词,用在表示身体部位的名词前 She caught me by the arm.她抓住了我的手臂. (8)用在某些有普通名词构成的国家名称,机关团体,阶级等专有名词前 the People's Republic of China 中华人民共和国 the United States 美国 (9)用在表示乐器的名词前 She plays the piano.她会弹钢琴. (10)用在姓氏的复数名词之前,表示一家人 the Greens 格林一家人(或格林夫妇) (11)用在惯用语中 in the day, in the morning... the day before yesterday, the next morning... in the sky... in the dark... in the end... on the whole, by the way...

英语比较级和最高级的用法

More than的用法 A. “More than+名词”表示“不仅仅是” 1)Modern science is more than a large amount of information. 2)Jason is more than a lecturer; he is a writer, too. 3) We need more than material wealth to build our country.建设我们国家，不仅仅需要物质财富. B. “More than+数词”含“以上”或“不止”之意，如： 4)I have known David for more than 20 years. 5)Let's carry out the test with more than the sample copy. 6) More than one person has made this suggestion. 不止一人提过这个建议. C. “More than+形容词”等于“很”或“非常”的意思，如： 7)In doing scientific experiments, one must be more than careful with the instruments. 8)I assure you I am more than glad to help you. D. more than + (that)从句，其基本意义是“超过（=over）”，但可译成“简直不”“远非”.难以，完全不能（其后通常连用情态动词can） 9) That is more than I can understand . 那非我所能懂的. 10) That is more than I can tell. 那事我实在不明白。 11) The heat there was more than he could stand. 那儿的炎热程度是他所不能忍受的 此外，“more than”也在一些惯用语中出现，如： more...than 的用法 1. 比……多，比……更 He has more books than me. 他的书比我多。 He is more careful than the others. 他比其他人更仔细。 2. 与其……不如 He is more lucky than clever. 与其说他聪明，不如说他幸运。 He is more （a）scholar than （a）teacher. 与其说他是位教师，不如说他是位学者。 注：该句型主要用于同一个人或物在两个不同性质或特征等方面的比较，其中的比较级必须用加more 的形式，不能用加词尾-er 的形式。 No more than/not more than 1. no more than 的意思是“仅仅”“只有”“最多不超过”，强调少。如： --This test takes no more than thirty minutes. 这个测验只要30分钟。 --The pub was no more than half full. 该酒吧的上座率最多不超过五成。-For thirty years，he had done no more than he （had）needed to. 30年来，他只干了他需要干的工作。 2. not more than 为more than （多于）的否定式，其意为“不多于”“不超过”。如：Not more than 10 guests came to her birthday party. 来参加她的生日宴会的客人不超过十人。 比较： She has no more than three hats. 她只有3顶帽子。（太少了） She has not more than three hats. 她至多有3顶帽子。（也许不到3顶帽子） I have no more than five yuan in my pocket. 我口袋里的钱最多不过5元。（言其少） I have not more than five yuan in my pocket. 我口袋里的钱不多于5元。（也许不到5元） more than, less than 的用法 1. （指数量）不到，不足 It’s less than half an hour’s drive from here. 开车到那里不到半个钟头。 In less than an hour he finished the work. 没要上一个小时，他就完成了工作。 2. 比……（小）少 She eats less than she should. 她吃得比她应该吃的少。 Half the group felt they spent less than average. 半数人觉得他们的花费低于平均水平。 more…than,/no more than/not more than (1)Mr．Li is ________ a professor; he is also a famous scientist． (2)As I had ________ five dollars with me, I couldn’t afford the new jacket then． (3)He had to work at the age of ________ twelve． (4)There were ________ ten chairs in the room．However, the number of the children is twelve． (5)If you tel l your father what you’ve done, he’ll be ________ angry． (6)－What did you think of this novel? －I was disappointed to find it ________ interesting ________ that one． 倍数表达法 1. “倍数+形容词（或副词）的比较级+than+从句”表示“A比B大（长、高、宽等）多少倍” This rope is twice longer than that one.这根绳是那根绳的三倍（比那根绳长两倍）。The car runs twice faster than that truck.这辆小车的速度比那辆卡车快两倍（是那辆卡车的三倍）。 2. “倍数+as+形容词或副词的原级+as+从句”表示“A正好是B的多少倍”。

“the way+从句”结构的意义及用法

“tｈｅwａｙ+从句”结构的意义及用法 首先让我们来看下面这个句子: Ｒead the foｌloｗｉnｇpassagｅａnd talkａbout ｉt wi ｔh your classmaｔes．Try tｏｔeｌl whaｔyｏu thiｎk ｏf Tom aｎd ｏｆｔhe ｗay the chiｌｄrenｔrｅated ｈim. 在这个句子中，ｔhe waｙ是先行词,后面是省略了关系副词that或in whｉch的定语从句。 下面我们将叙述“the ｗaｙ+从句”结构的用法。 1.tｈe wａy之后，引导定语从句的关系词是tｈat而不是hoｗ,因此，<<现代英语惯用法词典＞＞中所给出的下面两个句子是错误的：Ｔhｉs is ｔｈeｗayｈowｉtｈａppened. This is the way how he ａlwａｙs treats me. 2．在正式语体中,thaｔ可被in which所代替;在非正式语体中，ｔhat则往往省略。由此我们得到theｗay后接定语从句时的三种模式：1) tｈe ｗaｙ＋ｔhａt-从句２）the way +ｉn whiｃh－从句3) the ｗay +从句 例如：Ｔｈe way(in whiｃh ，thａt) ｔhｅｓｅｃomｒade ｓloｏｋａｔｐrobｌems is wrong．这些同志看问题的方法

不对。 Ｔｈｅｗａy(that ,ｉn ｗhiｃh)yoｕ’ｒe doinｇit is comple ｔeｌy crａzy.你这么个干法,简直发疯。 Wｅａdmiｒｅd him for thｅｗay ｉｎｗhｉch he fａｃeｓdiｆficultieｓ． Waｌlａｃe ａｎd Ｄarwiｎｇreed ｏn the way ｉｎwhi ｃh ｄｉfｆｅrｅnt forms ｏf life had ｂegｕn.华莱士和达尔文对不同类型的生物是如何起源的持相同的观点。 Thｉs is ｔｈe ｗaｙ（tｈａｔ) hｅdｉd it. I lｉkeｄｔhe waｙ(ｔhat) ｓｈeｏｒganized ｔhe ｍeetｉng． 3.theｗay(tｈat)有时可以与hｏw(作“如何”解）通用。例如： That’s tｈe ｗaｙ(tｈaｔ) shｅspoke. = Tｈat’s how shｅspoke.

初中英语比较级和最高级讲解与练习

初中英语比较级和最高级讲解与练习 形容词比较级和最高级 一．绝大多数形容词有三种形式,原级,比较级和最高级, 以表示形容词说明的性质在程度上的不同。 1. 形容词的原级: 形容词的原级形式就是词典中出现的形容词的原形。例如: poor tall great glad bad 2. 形容词的比较级和最高级: 形容词的比较级和最高级形式是在形容词的原级形式的基 础上变化的。分为规则变化和不规则变化。 二．形容词比较级和最高级规则变化如下: 1) 单音节形容词的比较级和最高级形式是在词尾加-er 和-est 构成。 great (原级) greater(比较级) greatest(最高级) 2) 以-e 结尾的单音节形容词的比较级和最高级是在词尾加-r 和-st 构成。 wide (原级) wider (比较级) widest (最高级) 3) 少数以-y, -er, -ow, -ble结尾的双音节形容词的比较级和最高级是在词尾加 -er 和-est构成。 clever(原级) cleverer(比较级) cleverest(最高级)， slow(原级) slower(比较级) slowest (最高级) 4) 以-y 结尾,但-y 前是辅音字母的形容词的比较级和最高级是把-y 去掉,加上-ier 和-est 构成. happy (原形) happier (比较级) happiest (最高级) 5) 以一个辅音字母结尾其前面的元音字母发短元音的形容词的比较级和最高级是双写该 辅音字母然后再加-er和-est。 原形比较级最高级原形比较级最高级 big bigger biggest hot hotter hottest red redder reddest thin thinner thinnest 6) 双音节和多音节形容词的比较级和最高级需用more 和most 加在形容词前面来构 成。 原形比较级最高级 careful careful more careful most careful difficult more difficult most difficult delicious more delicious most delicious 7)常用的不规则变化的形容词的比较级和最高级: 原级比较级最高级 good better best 好的 well better best 身体好的 bad worse worst 坏的 ill worse worst 病的 many more most 许多 much more most 许多 few less least 少数几个 little less least 少数一点儿 （little littler littlest 小的） far further furthest 远（指更进一步，深度。亦可指更远） far farther farthest 远（指更远，路程）

way 用法

表示“方式”、“方法”，注意以下用法： 1.表示用某种方法或按某种方式，通常用介词in(此介词有时可省略)。如： Do it (in) your own way. 按你自己的方法做吧。 Please do not talk (in) that way. 请不要那样说。 2.表示做某事的方式或方法，其后可接不定式或of doing sth。 如： It’s the best way of studying [to study] English. 这是学习英语的最好方法。 There are different ways to do [of doing] it. 做这事有不同的办法。 3.其后通常可直接跟一个定语从句(不用任何引导词)，也可跟由that 或in which 引导的定语从句，但是其后的从句不能由how 来引导。如： 我不喜欢他说话的态度。 正：I don’t like the way he spoke. 正：I don’t like the way that he spoke. 正：I don’t like the way in which he spoke. 误：I don’t like the way how he spoke. 4.注意以下各句the way 的用法： That’s the way (=how) he spoke. 那就是他说话的方式。 Nobody else loves you the way(=as) I do. 没有人像我这样爱你。 The way (=According as) you are studying now, you won’tmake much progress. 根据你现在学习情况来看，你不会有多大的进步。 2007年陕西省高考英语中有这样一道单项填空题： ——I think he is taking an active part insocial work. ——I agree with you_____. A、in a way B、on the way C、by the way D、in the way 此题答案选A。要想弄清为什么选A，而不选其他几项，则要弄清选项中含way的四个短语的不同意义和用法，下面我们就对此作一归纳和小结。 一、in a way的用法 表示：在一定程度上，从某方面说。如： In a way he was right.在某种程度上他是对的。注：in a way也可说成in one way。 二、on the way的用法 1、表示：即将来(去)，就要来(去)。如： Spring is on the way.春天快到了。 I'd better be on my way soon.我最好还是快点儿走。 Radio forecasts said a sixth-grade wind was on the way.无线电预报说将有六级大风。 2、表示：在路上，在行进中。如： He stopped for breakfast on the way.他中途停下吃早点。 We had some good laughs on the way.我们在路上好好笑了一阵子。 3、表示：(婴儿)尚未出生。如： She has two children with another one on the way.她有两个孩子，现在还怀着一个。 She's got five children，and another one is on the way.她已经有5个孩子了，另一个又快生了。 三、by the way的用法

英语比较级和最高级

形容词比较级和最高级的形式 一、形容词比较级和最高级的构成 形容词的比较级和最高级变化形式规则如下 构成法原级比较级最高级 ①一般单音节词末尾加 er 和 est strong stronger strongest ②单音节词如果以 e结尾，只加 r 和 st strange stranger strangest ③闭音节单音节词如末尾只有一个辅音字母， 须先双写这个辅音字母，再加 er和 est sad big hot sadder bigger hotter saddest biggest hottest ④少数以 y, er(或 ure), ow, ble结尾的双音节词， 末尾加 er和 est(以 y结尾的词，如 y前是辅音字母， 把y变成i，再加 er和 est，以 e结尾的词仍 只加 r和 st) angry Clever Narrow Noble angrier Cleverer narrower nobler angriest cleverest narrowest noblest ⑤其他双音节和多音节词都在前面加单词more和most different more different most different 1) The most high 〔A〕mountain in 〔B〕the world is Mount Everest，which is situated 〔C〕in Nepal and is twenty nine thousand one hundred and fourty one feet high 〔D〕 . 2) This house is spaciouser 〔A〕than that 〔B〕white 〔C〕one I bought in Rapid City，South Dakota 〔D〕last year. 3) Research in the social 〔A〕sciences often proves difficulter 〔B〕than similar 〔C〕work in the physical 〔D〕sciences. 二、形容词比较级或最高级的特殊形式：

高中英语的比较级和最高级用法总结

比较级和最高级 1.在形容词词尾加上―er‖ ―est‖ 构成比较级、最高级： bright（明亮的）—brighter—brightest broad（广阔的）—broader—broadest cheap（便宜的）—cheaper—cheapest clean（干净的）—cleaner—cleanest clever（聪明的）—cleverer—cleverest cold（寒冷的）—colder—coldest cool（凉的）—cooler—coolest dark（黑暗的）—darker—darkest dear（贵的）—dearer—dearest deep（深的）—deeper—deepest fast（迅速的）—faster—fastest few（少的）—fewer—fewest great（伟大的）—greater—greatest hard（困难的,硬的）—harder—hardest high（高的）—higher—highest kind（善良的）—kinder—kindest light（轻的）—lighter—lightest long（长的）—longer—longest loud（响亮的）—louder—loudest low（低的）—lower—lowest near（近的）—nearer—nearest new（新的）—newer—newest poor（穷的）—poorer—poorest quick（快的）—quicker—quickest quiet（安静的）—quieter—quietest rich（富裕的）—richer—richest short（短的）—shorter—shortest slow（慢的）—slower—slowest small（小的）—smaller—smallest smart（聪明的）—smarter—smartest soft（柔软的）—softer—softest strong（强壮的）—stronger—strongest sweet（甜的）—sweeter—sweetest tall（高的）-taller-tallest thick（厚的）—thicker—thickest warm（温暖的）—warmer—warmest weak（弱的）—weaker—weakest young（年轻的）—younger—youngest 2.双写最后一个字母,再加上―er‖ ―est‖构成比较级、最高级： big（大的）—bigger—biggest fat（胖的）—fatter—fattest hot（热的）—hotter—hottest red（红的）—redder—reddest sad（伤心的）—sadder—saddest thin（瘦的）—thinner—thinnest wet（湿的）—wetter—wettest mad（疯的）—madder—maddest 3.以不发音的字母e结尾的形容词,加上―r‖ ―st‖ 构成比较级、最高级：able（能干的）—abler—ablest brave（勇敢的）—braver—bravest close（接近的）—closer—closest fine（好的,完美的）—finer—finest large（巨大的）—larger—largest late（迟的）—later—latest nice（好的）—nicer—nicest ripe（成熟的）—riper—ripest

The way的用法及其含义(一)

The way的用法及其含义（一） 有这样一个句子：In 1770 the room was completed the way she wanted. 1770年，这间琥珀屋按照她的要求完成了。 the way在句中的语法作用是什么？其意义如何？在阅读时，学生经常会碰到一些含有the way 的句子，如：No one knows the way he invented the machine. He did not do the experiment the way his teacher told him.等等。他们对the way 的用法和含义比较模糊。在这几个句子中，the way之后的部分都是定语从句。第一句的意思是，“没人知道他是怎样发明这台机器的。”the way的意思相当于how；第二句的意思是，“他没有按照老师说的那样做实验。”the way 的意思相当于as。在In 1770 the room was completed the way she wanted.这句话中，the way也是as的含义。随着现代英语的发展，the way的用法已越来越普遍了。下面，我们从the way的语法作用和意义等方面做一考查和分析： 一、the way作先行词，后接定语从句 以下3种表达都是正确的。例如：“我喜欢她笑的样子。” 1. the way+ in which +从句 I like the way in which she smiles. 2. the way+ that +从句 I like the way that she smiles. 3. the way + 从句(省略了in which或that) I like the way she smiles. 又如：“火灾如何发生的，有好几种说法。” 1. There were several theories about the way in which the fire started. 2. There were several theories about the way that the fire started.

(完整版)初中英语比较级和最高级的用法

英语语法---比较级和最高级的用法 在英语中通常用下列方式表示的词:在形容词或副词前加more(如 more natural,more clearly )或加后缀 -er(newer,sooner )。典型的是指形容词或副词所表示的质、量或关系的增加。英语句子中，将比较两个主体的方法叫做“比较句型”。其中，像“A比B更……”的表达方式称为比较级；而“A最……”的表达方式则称为最高级。组成句子的方式是将形容词或副词变化成比较级或最高级的形态。 一、形容词、副词的比较级和最高级的构成规则 1．一般单音节词和少数以-er，-ow结尾的双音节词，比较级在后面加-er，最高级在后面加-est； （1）单音节词 如：small→smaller→smallest short→shorter→shortest tall→taller→tallest great→greater→greatest （2）双音节词 如：clever→cleverer→cleverest narrow→narrower→narrowest 2．以不发音e结尾的单音节词，比较在原级后加-r，最高级在原级后加-st； 如：large→larger→largest nice→nicer→nicest able→abler→ablest 3．在重读闭音节（即：辅音＋元音＋辅音）中，先双写末尾的辅音字母，比较级加-er，最高级加-est； 如：big→bigger→biggest hot→hotter→hottest fat→fatter→fattest 4．以“辅音字母＋y”结尾的双音节词，把y改为i，比较级加-er，最高级加-est； 如：easy→easier→easiest heavy→heavier→heaviest busy→busier→busiest happy→happier→happiest 5．其他双音节词和多音节词，比较级在前面加more，最高级在前面加most； 如：beautiful→more beautiful→most beautiful different→more different→most different easily→more easily→most easily