Control of viscosity in starch and polysaccharide solutions with
ultrasound after gelatinization
Yasuo Iida ?,Toru Tuziuti,Kyuichi Yasui,Atsuya Towata,Teruyuki Kozuka
Ultrasonic Processing Group,Advanced Manufacturing Research Institute,National Institute of Advanced Industrial Science and Technology (AIST),
2266-98Shimoshidami,Moriyama-ku,Nagoya 463-8560,Japan
Received 16November 2006;accepted 25March 2007
Abstract
Application of power ultrasound has immense potential for a wide variety of processes in the food industry which include sterilization,emulsification,extraction,crystallization,degassing,filtration,drying,and more.Controlling the viscosity of starch (polysaccharide)solutions is one of the most promising processes to be developed.Power ultrasound can effectively decrease the viscosity of starch solutions after gelatinization.At the high starch concentrations (20–30%),starch gel can be liquidized by sonication.The viscosity of the starch solution of moderate concentration (5–10%)can be reduced about two orders of magnitude to 100mPa·s by the ultrasonic irradiation for 30min.The treated solution can be efficiently powdered by a spray-dryer after the sonication.The effectiveness of the ultrasonic process has been evaluated by measuring the changes in viscosity.Granule disintegration was determined using a method which measures the swelling power of starch.Change in molecular weight of the starch was monitored by gel permeation chromatography and a static light scattering method.The depolymerization process of the starch has been also monitored by NMR spectroscopy.The elucidated merits of the ultrasonic process are:1)the process does not require any chemicals and additives;2)the process can be simple and rapid,which means that the process is cost effective;and 3)the process will not induce large changes in the chemical structure and in particular,the properties of starches.The ultrasonic process has been confirmed to be applicable for many kinds of starches (corn,potato,tapioca,and sweet potato)and polysaccharides.?2007Elsevier Ltd.All rights reserved.
Keywords:Starch;Polysaccharide;Ultrasound;Cavitation;Viscosity;Gelatinization
Industrial relevance:Starches and a variety of polysaccharides are used in a multitude of applications throughout the food industry.Ultrasonically assisted modification of their chemical and physical characters is an important process and has commercial potential.In this paper,the changes in their viscosity,molecular weight,and the NMR spectra have been measured to evaluate the effectiveness of the ultrasonic process for the depolymerization and the viscosity control of the starch and polysaccharide solutions after gelatinization.
1.Introduction
Application of power ultrasound has immense potential for a wide variety of processes in the food industry (Mason,Paniwnyk and Lorimer,1996;Knorr,Zenker,Heinz and Lee,2004).The U.S.Food and Drug Administration (FDA)(2000)released a report entitled “Kinetics of Microbial Inactivation for Alternative Food Processing Technologies ”,and ultrasound was
among one of the alternative methods featured.A number of papers have been published dealing with the ultrasonically assisted extraction of different vegetable materials.The possible benefits of ultrasound in extraction are mass transfer intensifica-tion,cell disruption,improved penetration and capillary effects.For example,Toma,Vinatoru,Paniwnyk and Mason (2001)have reported that the amounts of extractable compounds from fennel,hops,marigold,mint and lime were increased about 20–40%by ultrasound extraction in comparison with the classical extraction procedure.Ultrasonic filtration of particulate matter or colloidal particles from a liquid is arousing interests
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since the rate of flow through a filter can be increased sub-stantially on application of ultrasound(Kobayashi,Kobayashi, Hosaka and Fujii,2003).Ultrasonic drying is also an important technique as it has commercial potential.Sonically enhanced drying can be carried out at lower temperature than conventional methodology,which reduces the probability of oxidation or degradation of the food(Gallego-Juarez,1998).
Ultrasonic depolymerization has been applied on a variety of homo-and heteropolysaccharides such as dextran(Lorimer, Mason,Cuthbert and Brookfield,1995),pullulan(Koda,Mori, Matsumoto and Nomura,1994),chitosan(Chen,Chang,and Shyur,1997),hyaluronic acid(Miyazaki,Yamamoto and Okada, 2001),xyloglucan(Vodeni?arová,D?imalová,Hromádková, Malovíková,and Ebringerová,2006)and starch(Chung,Moon, Kim and Chun,2002;Azhar and Hamdy,1979).Starch is a main source of carbohydrate in the human diet.It also contributes as a valuable ingredient to the food industry,being widely used as a thickener,gelling agent,bulking agent and water retention agent. Natural starch is partially crystalline in its native granule form. During food processing,starch granules gelatinize as a result of heating in the presence of water,i.e.the granules swell,crys-talline regions melt and starch chains become hydrated.The structure changes that take place during gelatinization include a crystallite melting and double-helix unwinding(Waigh,Gidley, Komanshek and Donald,2000),absorption of water in the amorphous background region(Jenkins and Donald,1998), displacement of amylopectin units and leaching of amylose from the granules(Atkin,Abeysekera,Cheng and Robards,1998).In this way,aqueous suspensions of discrete semi-crystalline granules are transformed into a continuous amorphous gel phase.Starch in amorphous gel phase is highly viscous,which is important for a specific application:to provide thickening,im-prove binding,increase stability,improve mouth feeling and sheen.However,the viscous nature of the starch gel is unde-sirable in the other applications,such as in the post-processing of starch gel for spray-drying,where the viscosity of the solution will encumber the spraying process.Ultrasound can reduce the viscosity of the starch solution as described in the pioneering work by Szent-Gy?rgyi(1933).
Many physical and functional properties of starch,similarly as those of other polysaccharides,depend on the molecular mass of the product used.For certain applications,polysaccharides of lower molecular mass have selected advantages over the high-molecular mass candidates due to their improved diffusion into biological tissues.Shortening of the polysaccharide macromole-cular chains can be achieved by various methods.In any case,a prerequisite is to prepare depolymerized polysaccharides without alteration of the chemical structure and particular properties.
In this study,the effectiveness of the ultrasonic process has been evaluated by measuring the changes in viscosity.Granule disintegration was determined using a method to measure the swelling power of starch.The changes in the molecular weight of starch were monitored by a gel permeation chromatography and a static light scattering method.The depolymerization process of the starch by ultrasound has also been monitored by NMR spectroscopy.From the results,the mechanism of the control of viscosity of starch and polysaccharide solutions with ultrasound after gelatinization has been discussed and the merits of the ultrasonic process have been elucidated.
2.Experimental
Samples of various starches and polysaccharides were ob-tained from Futamura Starch Corp.(Tahara,Japan)and were used as received.
For the viscosity measurements,starch(polysaccharide) samples were prepared as follows;500g of starch slurry(10%or 5%solids)were heated at90°C for60min in a glass vessel with a mantle heater for uniform heating.Starch pastes thus prepared were cooled down to60°C and100g of starch paste batched off from the vessel was sonicated for30min at the temperature using a sonifier(model D250,Branson Ultrasonics Corp., Danbury,USA)equipped with a tapered horn tip(end diameter of12.7mm).The output energy was usually set to120W.The sample was held in the temperature controlled water bath to prevent the temperature rise by the sonication.Sonication with bath type equipment(Honda Electronics,HSR-11-45,Toyoha-shi,Japan)was also utilized for sonicating the starch paste.In this set up,500g of sample paste was sonicated for30min with mechanical stirring for achieving homogeneous irradiation of ultrasound to the sample.The output energy was usually set to 100W.Viscosity of the samples continued to measure using a viscometer(RVDV-I+,Brookfield Engineering Laboratories, Middleboro,USA)at60,50,40,30and20°C.The viscometer was a spindle type with a spring of0.72mN-m in torque and the spindle was rotated at100rpm.The sample was cooled in a water bath to the specified temperature with the cooling rate of 10°C/30min.
Granule disintegration was determined using a method to measure the swelling power of starch(Chung et al.,2002).Five grams of sample was mixed with500mL of water in a beaker. The slurry was heated at65,75,and85°C for30min while stirring at200rpm.Two hundred grams of pastes were then sonicated for1or5min with the horn type sonicator at the output power of120W.The sonicated pastes were immediately cooled down to room temperature and centrifuged at7000rpm for 15min.The precipitated portion was weighed and which is expressed as the degree of granule disintegration(DGD); DGD=(grams of wet precipitated weight)/(grams of dry starch), usually termed as swelling power.In addition,the supernatant liquid was collected and evaporated at90°C for8h.The amount of solubilized starch in the supernatant as the dried residue was also weighed and used in order to express the degree of solubilization(DSOL);DSOL=(grams of dried residue weight)/(grams of dry starch).
Molecular weight distribution of the depolymerized starch samples were determined by high performance gel permeation chromatography(HPGPC)on exclusion columns(TSK gelα-M (300×7.8mm I.D.)with a TSK guard columnα(40×6mm I.D.), (Tosoh Corp.,Tokyo,Japan),calibrated with pullulan standards, Shodex?P-82series(Showa Denko K.K.,Tokyo,Japan),using aqueous0.1mol dm?3sodium nitrate as eluent(Jackson,Waniska and Rooney,1989).The eluate was monitored by refractometry. The molecular weight of the starch after sonication was also
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Y.Iida et al./Innovative Food Science and Emerging Technologies9(2008)140–146
determined by the static laser scattering method(Zetasizer Nano ZS,Malvern,Worcs,UK).
1H and13C NMR spectra were recorded in D
2
O at25°C using the FT NMR spectrometer(Inova300,Varian Inc.,Palo Alto,USA).
3.Results
3.1.Effect of sonication on the changes in viscosity
Fig.1shows the typical changes in viscosity which have been observed by sonicating5%and10%of waxy maize starch solution after gelatinization.It can be observed that there is a drastic decrease in viscosity of these solutions.The decrease in the viscosity was about two orders of magnitude.For example, the viscosity of2000mPa·s for10%solution decreased to 20mPa·s after sonication for30min.The low viscosity of the sonicated starch solutions were also obtained even by cooling down to room temperature.It should be noted that the viscosity of the sonicated starch solution fall below the viscosity limit for
spray-drying process,～100mPa·s.Higher concentration of starch slurries,i.e.15–20%seemed to be the limit for the depression of viscosity because the firm gel formed at the con-centration range might not be effectively affected by sonication. The other starches studied,i.e.,potato,tapioca,sweet potato, corn starch,also showed the same tendency as the waxy maize starch.Whereas,for the polysaccharides,the effect of sonication was intensely dependent on the species.For pectine,rather a small change,i.e.～50%decrease in viscosity was only ob-served.On the other hand,glucomannan,which is highly viscous and thus the experiment was carried out at lower concentration of1%,showed a drastic depression in viscosity by the sonication.The viscosity changes were nearly in the same order as shown by the starches.The results of changes in viscosity of starches and polysaccharides by the sonication process have summarized in Table1at the typical experimental conditions,i.e.with the horn type sonicator and at a slurry concentration of5%.
Fig.2shows the effect of sonication temperature with10% waxy maize starch solution.It is clearly indicated that the differences in the changes in viscosity are not so large with changes in sonication temperature,but still significant.The viscosity of the sonicated solution was decreased in the following order;80°C N60°C N40°C.These results should be considered by the influences of sonication temperature operated in the opposite direction;the mechanical effects of ultrasound effec-tively develop in relatively low viscosity condition,which is in favor of higher temperature.Alternatively,the cavitational
effects Fig.1.Depression of viscosity of5and10wt.%waxy maize starch solution by
sonication for30min at60°C using a horn type sonicator:□=10%
unsonicated,■=10%sonicated,Δ=5%unsonicated,▲=5%sonicated.The
viscosity was continued to measure from60°C to20°C at the step of10°.The
experiments were repeated3times and the error bars indicate2σ.
Table1
Changes in the viscosity of starches and polysaccharides by sonication
Samples Viscosity(mPa·s)
60°C50°C40°C30°C20°C
Waxy maize Silent254300372440586
US8681014
Potato Silent528782210031105410
US88101620
Tapioca Silent574900142021103200
US68101416
Sweet potato Silent65676091211401310
US466812
Glucomannan(1%)Silent34804480440065207600
US6478104178250
Pectine Silent2302064807421110
US134190296424700
Sonication was carried out at60°C for30min,and viscosities were measured at
60,50,40,30,and20°C with the same sample but without additional agitation.
The concentrations of slurries were5%except for glucomannan(1%).The
experiments were repeated2times to check the repeatability.The data on the
table show the averaged
values.
Fig.2.Effect of sonication temperature on the depression of viscosity of10wt.%
waxy maize starch solution.The samples were sonicated at80°C(○),60°C(Δ),
and40°C(?),respectively.The viscosities of the samples before the sonication
were shown in the parentheses.The viscosity was continued to measure from the
sonication temperature to20°C,halted at60°C,40°C and30°C.The
experiments were repeated3times and the error bars indicate2σ.
142Y.Iida et al./Innovative Food Science and Emerging Technologies9(2008)140–146
of ultrasound work well at the lower temperature.The results indicate that the cavitation effects at lower temperature were more effective than the mechanical effects at higher temperature in the viscosity depression of starch solutions.
The effect of sonication frequency was studied with5% waxy maize starch solution at several frequencies at100W output power using bath type sonicator.The viscosity of the solution before sonication was214mPa·s.After the sonication, the viscosity decreased down to36,20,12and8mPa·s at183, 143,99and44kHz,respectively.The result indicates that the depression of viscosity can be effectively performed at the lower ultrasound frequency.
3.2.Degree of disintegration and solubilization
The degree of granule disintegration(DGD)and the degree of solubilization(DSOL),the definitions are given in the experi-mental section,of starches and polysaccharides are summarized in Table2.DGD increases at first as the swelling of the granules
proceed by the heat treatment.In this experimental condition the maximum value,which means that the amount of the added water is completely absorbed by the starch(polysaccharides), will be about100because500mL water was added to5g of sample.The DGD values of potato starch exceed the value of 100at the temperature higher than75°C.This indicates that the total volume of the sample was gelatinized and the separation of liquid portion was impossible.DGD values of the starches without sonication increased with increasing the treatment temperature.This means that the swelling of starch granules progressed by the heat treatment.On the other hand,with the sonication even as short as1min,the swelled granule will disintegrate and a certain amount of contents in the granule will be solubilized.At this stage,DGD will decrease toward zero and DSOL will increase toward its maximum value of1.For all starches tested,except for the corn starch,DSOLs attain and exceed the value of0.9and approaching the maximum value of1 by the sonication carried out for1or5min.The results clearly show the effectiveness of sonication for the solubilization of starch solutions after the gelatinization.DSOLs will depend on the temperature of gelatinization.Though the sonication can directly disintegrate the starch granules(Azhar and Hamdy, 1979),it works more efficiently after the gelatinization.The gelatinization temperature of the corn starch(95°C)is higher than the other starches;waxy maize(60°C),potato(65°C), tapioca(60°C),sweet potato(75°C),and even higher than the attainable temperature by a water bath.The low DSOL value of the corn starch is caused by this insufficient gelatinization.
The polysaccharides,i.e.,glucomannan and pectine,showed a unique character,respectively,and differ in behavior from those of the starches.The glucomannan samples completely gelatinized at all temperatures as in the case of potato starch at high temperature.On the other hand,the pectine samples became viscous clear solutions.For both glucomannan and pectine,the measurements of DGD and DSOL values were meaningless and thus omitted from the table.
3.3.Molecular weight distribution
To investigate the mechanism of viscosity depression by ultrasound irradiation,the changes in molecular weight dis-tribution of waxy maize by sonication after gelatinization were monitored by HPGPC.Fig.3shows the molecular weight distribution of the waxy maize starch before and after sonication for30–120min.Before sonication,the molecular weight peak located at around3×106.The molecular weight sharply decreased in the initial30min and thereafter the depolymeriza-tion proceeded slowly.The peaks of molecular weight decrease to5×105,3×105and2×105after the sonication for30min, 60min and120min,respectively.The molecular weight distribution pattern shows some changes as seen in the data of sonication for120min,where a shoulder at around1×105 becomes obvious.
Table2
The degree of granule disintegration and the degree of solubilization,the definitions are given in the experimental section,of starches and polysaccharides at65,75and85°C
Samples Sonication
time(min)Degree of granule
disintegration
Degree of
solubilization
65°C75°C85°C65°C75°C85°C
Waxy maize0 3.525.722.60.0040.2820.483
1 2.90.60.50.1150.9650.941
5 2.50.50.40.1610.9930.95
6 Potato028.8104.5110.20.0840.0000.000
1 2.9 1.8 2.30.6300.8940.908
5 1.10.5 1.20.7100.9390.942 Tapioca022.026.931.00.1300.1710.241
1 1.70.80.80.8060.9620.965
50.60.50.80.8430.993 1.027 Sweet potato0 2.5 6.519.70.0100.0560.153
1 2.1 2.40.50.0210.3880.911
5 2.0 1.70.30.0370.4370.909 Corn0 4.49.19.50.0250.0530.089
1 4.7 6.47.70.0270.0930.220
5 4.2 4.8 3.10.0390.4510.718 The experiments were repeated2times to check the repeatability.The data on the table show the averaged
values.
Fig.3.Molecular weight distribution of waxy maize starch as a function of
sonication time.
143 Y.Iida et al./Innovative Food Science and Emerging Technologies9(2008)140–146
The depolymerization process was also monitored by static light scattering measurement.The averaged molecular weight is obtained by the Debye plot based on the Rayleigh's equation. Before sonication,the average molecular weight was around 3.6×106.The average molecular weights decrease to2.9×106, 1.4×106and1.0×106after the sonication for10,30and60min, respectively.
The peak molecular weight of HPGPC curves and the average molecular weight by the static light scattering contain the different information and the exact consistency between the values obtained by the two different methods will not be necessary.However,the depolymerization process by sonication indicated by the molecular weight measurements show the identical tendency;the molecular weight sharply decreased in the initial period of10–30min and thereafter the depolymerization proceeded slowly.
3.4.NMR spectroscopic characterization of sonicated starch solution
To confirm the structural changes of starch introduced by the sonication process,1H and13C NMR spectra of the sonicated samples were recorded and compared to that of the gelatinized starch sample.The1H NMR spectra of waxy maize starch (Fig.4A)was measured with D2O to reduce the intensity of H2O peak,and to obtain better detection of starch peaks.The starch resonance peaks at around3.7ppm correspond to CH protons except for the anomeric protons and the peak at 5.4ppm corresponds to anomeric protons.The peak at4.8ppm arises as a result of proton–deuteron exchange of D2O with–OH of starch and moisture(H2O)in the starch granules(Wu and Eads,1993).If we can make the reasonable assumptions that this peak at4.8ppm contains all the protons from the granule moisture and all starch hydroxyl protons,that all water molecules are highly mobile,and that the fraction of immobile exchangeable protons is negligible, then this peak can serve as an internal standard.The integrated intensity of the starch peaks apparently increases with sonication. It indicates that the fraction of the mobile starch molecules increased by the sonication.In quantitative terms,the fraction of starch which is highly mobile can be calculated as follows;
f mobile?I starch=X CH I water=X OH
where I starch is the sum of NMR integrals of the peaks of CH protons at3.7and5.4ppm,I water is the integral of the water peak. X CH is the mole fraction of non-exchangeable CH protons of starch,and X OH is the mole fraction of exchangeable protons from the starch hydroxyl group and moisture(Wu and Eads,1993). From the1H NMR spectra shown in Fig.4A and assuming the moisture content in the starch granules to be10%,we can calculate the value of highly mobile fraction of starch which is 38%for the gelatinized starch and then the fraction increased to 95%by the sonication.
13C NMR spectra of waxy maize starch after gelatinization and after the additional sonication have been shown in Fig.4B.In these spectra,each carbon of the glucose unit appears as a single line and six main peaks are attributed to as C-1(102.0ppm),C-4(79.2ppm),C-3(75.7ppm),C-5(75.0ppm),C-2(73.5ppm)and C-6(62.8ppm),respectively(Morris and Hall,1982;McIntyre, Ho,V ogel and Alberta,1990).Starch is a mixture of two main components;amylose,a linear(1→4)-α-D-glucan and amylopectin,a highly branched macromolecule consisting of (1→4)-α-D-glucan short chains linked throughα-(1→6)lin-kages.The relatively low intensity of C-4peak indicates that the waxy maize starch is mainly composed of a highly branched amylopectin.The spectra suggested two important features about the sonication process;the first is that the changes in spectral patterns before and after the sonication is not noticeable.This means that the damages in the macromolecular chain or the production of small fragmental units are not detectable in the NMR spectra.The second point is that the spectral intensity was largely increased by the sonication.This result supports that,as quantitated by the1H NMR spectra,the highly mobile fraction of starch was largely increased by the sonication.
4.Discussion
The heating process induces many physical changes within the starch granule resulting in gelatinization.In order to
understand Fig.4.Proton(A)and Carbon-13(B)NMR spectra of10wt.%waxy maize starch/D2O gel before(upper trace)and after(lower trace)the sonication for60min.
144Y.Iida et al./Innovative Food Science and Emerging Technologies9(2008)140–146
the changes occurring during gelatinization,the molecular events taking place within the granule during the processing conditions have been investigated.A summary of the macromolecular events resulting during starch gelatinization in the presence of excess water has been shown in Fig.5based on the observation by Atkin,Abeysekera,Cheng and Robards (1998).The scheme is as follows;swelling due to hydration increases granule diameter;ring structure become visible in granules;an increase in tempera-ture further causes swelling of granules;granular rings breakdown homogeneously into particles of approximately 400nm size;the particles are then displaced from their original position in the rings and thus appeared randomly distributed within the swollen granule;application of temperature deforms and ruptures the granule and thereby releasing the granular contents;once the contents are released,the granular surface,often called granular ghosts,collapses and frequently remains intact in solution,the gelatinized solution will exhibit retrogradation to form a sticky solid.Ultrasound can expedite the depolymerization process of the starch gel by separating the amylopectin units and leaching out amylose units from the collective entity remained in the amorphous gel phase (Jackson et al.,1989).The interactions between the polymer molecules will be weakened and,as a result,the viscosity would be decreased by the destruction of the polymer network.The important point revealed in this study is that the sonication process will drastically depress the solution viscosity without alteration of the chemical structure of the polymer chains as indicated by the NMR spectra.A decrease in molecular weight by the sonication observed with HPGPC seems to be mainly caused by the increase in the number of free mobile polymer molecules from the intertwisted polymer aggregate.V odeni ?arová,D ?imalová,Hromádková,Malovíková,and Ebringerová(2006)have recently investigated the characteristics of three different radiation sources,i.e.,ultrasound,γ-radiation and microwave in the degradation process of xyloglucan.Their
results showed that depolymerization by ultrasound for 120min yielded products without significant alteration of primary struc-ture of the polysaccharide.Degradation by microwave changed the composition of sugar due to cleavage of glycosyl side chains.Furthermore,γ-radiation induced chain cleavage and formation of high-molecular mass components.They concluded that ultra-sonication was the most convenient procedure to decrease the molecular mass of xyloglucane.5.Conclusions
The present investigation shows that power ultrasound can effectively decrease the viscosity of starch solutions after gela-tinization.The viscosity of the starch solution after gelatinization can be reduced by about two orders of magnitude toward below 100mPa·s by the ultrasonic irradiation applied for 30min.The treated solution can be efficiently powdered by a spray-dryer after the sonication.The elucidated merits of the present ultrasonic process are:1)the process does not require any chemicals and additives;2)the process can be simple and rapid,which means that the process is cost effective;and 3)the process will not induce large changes in the chemical structure,and in particular,the properties of starches.Also,the ultrasonic process has been confirmed to be applicable for many kinds of starches (corn,potato,tapioca,and sweet potato)and polysaccharides.Acknowledgements
This work is supported by a Grant from the Ministry of Economy,Trade and Industry,Japan.The authors thank Futamura Starch (Tahara,Japan)for the collaboration through-out this project.The authors also would like to thank Dr.K.Ohta (HPGPC),Dr.M.Nishida (NMR)and Ms.E.Tatsukawa for their support in conducting some of the
experiments.
Fig.5.A diagrammatic description of swelling and gelatinization of starch granule.Ultrasound expedites the depolymerization process by separating the amylopectin units and leaching out amylose units from the collective entity remained in the amorphous gel phase.
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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。
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.
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。
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.
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”。
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）
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：
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
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
初中英语形容词比较级和最高级讲解与练习 形容词比较级和最高级 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。 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"
◇下列形容词和副词没有比较级和最高 （即表示“最高程度”或“绝对状态”的形容词和副词没有比较级和最高级） empty, wrong, perfect, unique, extreme, excellent, favourite, true, right, correct, extremely ... 形容词副词比较级最高级使用注意事项 ◇比较应在同类事物之间进行。 误：Your English is better than me. 正：Your English is better than mine. ◇比较级前可以有一个表示程度的状语，最常见的三大修饰词是：a little, much, even。 以下单词也可用来修饰：any, far, still, a lot, yet, rather。 My sister is a little taller than me. Their house is much larger than ours. 另外，名词短语也可修饰比较级，说明程度。 I’m three years older than he. 特别提醒：very, quite, too不可修饰比较级。 ◇避免重复使用比较级。 误：He is more kinder to small animals than I. 正：He is much kinder to small animals than I. 误：He is more cleverer than his brother. 正：He is cleverer than his brother. ◇比较要符合逻辑，在同一范围内比较时，避免将主语含在比较对象中，这时需使用other来排除自身。 误：China is larger that any country in Asia. 正：China is larger than any other country in Asia. 误：John studies harder than any student in his class. 正：John studies harder than any other student in his class. 正：John studies harder than any of the other students in his class. 正：John studies harder than anyone else in his class. ◇比较要遵循前后一致的原则，注意前后呼应。 The population of Shanghai is larger than that of Beijing. It is easier to make a plan than to carry it out. ◇序数词通常只修饰最高级。 Africa is the second largest continent. The Yellow River is the second longest river in China. This is the third most popular song of Michael Jackson. ◇为避免重复，我们通常用that, those, one, ones代替前面出现的名词。that 代替可数名词单数和不可数名词，those代替可数名词复数。one既可指人又可指物，只能 代替可数名词。 The weather in China is different from that in America. The book on the table is more interesting than that(或the one)on the desk. A box made of steel is stronger than one made of wood. 误：In winter, the weather of Beijing is colder than it of Shanghai. 正：In winter, the weather of Beijing is colder than that of Shanghai. ◇“否定词 + 比较级”相当于最高级。
英语比较级和最高级
一、比较级和最高级的讲解 变化规则 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 n arrow→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 d ifferent 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"。
形容词的比较级和最高级: 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。 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) 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。 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) 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。 big (原级) bigger (比较级) biggest (最高级) ) 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)? difficult (原级) more beautiful (比较级) more difficult (比较级) 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 little less least ill worse worst far farther(further) farthest(furthest) 形容词前如加less 和lest 则表示"较不"和"最不" important 重要 less important 较不重要 lest important 最不重要 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。 It is warmer today than it was yesterday. 今天的天气比昨天暖和。 This picture is more beautiful than that one.
little:形容词比较级littler/less/lesser 形容词最高级littlest/least 副词比较级less 副词最高级least far:形容词比较级farther/further 形容词最高级farthest/furthest 副词比较级farther/further 副词最高级farthest/furthest well:形容词比较级better 形容词最高级best 副词比较级better 副词最高级best ill:形容词比较级worse 形容词最高级worst 副词比较级worse 副词最高级worst many:形容词比较级more 形容词最高级most bad:形容词比较级worse 形容词最高级worst good:形容词比较级better 形容词最高级:best old:形容词比较级:older/elder 形容词最高级:oldest/eldest good:比较级better 最高级the best hot:比较级hotter 最高级the hottest heavy:比较级heavier 最高级the heaviest fine:比较级finer 最高级the finest exciting:比较级more exciting 最高级the most exciting bad:比较级worse 最高级the worst creative:比较级more creative 最高级the most creative boring:比较级more boring 最高级the most boring far:比较级farther/further 最高级the farthest/the furthest near:比较级nearer
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：beautiful→more beautiful→most beautiful different→more different→most different easi ly→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. 6.有少数形容词、副词的比较级和最高级是不规则的，必须熟记。 如：good→better→best well→better→best bad→worse→worst ill→worse→worst