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Antioxidant properties of Maillard reaction products obtained by gamma-irradiation of whey proteins

S.P.Chawla *,Ramesh Chander,Arun Sharma

Food Technology Division,Bhabha Atomic Research Centre,Trombay,Mumbai 400085,India

a r t i c l e i n f o Article history:

Received 8September 2008

Received in revised form 12January 2009Accepted 12January 2009

Keywords:

Maillard reaction Gamma-irradiation Antioxidant Free radicals Whey protein

a b s t r a c t

The radiation processing of sugar–amino acid solutions results in formation of Maillard reaction products (MRPs).In the present study,the ef?cacy of gamma-irradiation in the formation of MRPs from whey pro-tein powder was investigated.The formation of MRPs in whey protein suspension was studied by mon-itoring spectrophotometeric and chemical changes.A dose-dependent increase in UV absorbance and development of ?uorescence was observed.Formation of brown pigments was established by increased A 420nm and Hunter colour upon irradiation.These MRPs exhibited antioxidant activity as measured by 1,1-diphenyl-2-picrylhydrazyl and b -carotene bleaching assays.Reducing power and iron-chelating abil-ities of MRPs also increased upon irradiation.These MRPs were able to scavenge hydroxyl and superoxide anion radicals under in vitro conditions.Dose-dependent decrease in free amino groups and lactose sug-gested the formation of glycated proteins upon irradiation treatment.SDS–PAGE analyses indicated for-mation of crosslinked proteins upon irradiation.

1.Introduction

The Maillard reaction or non-enzymatic browning corresponds to a set of reactions resulting from the initial condensation be-tween an available amino group and a carbonyl-containing moiety,usually a reducing sugar.This reaction is known to be responsible for the attractive ?avour and brown colour of some cooked foods (Jing &Kitts,2002).It is one of the major reactions taking place during thermal processing,cooking,and storage of foods.A myriad of products are formed,which have direct impact on nutritional and sensory qualities of foods.The Maillard reaction products (MRPs)formed in an amino acid–sugar model system have been known to be associated with the formation of compounds with pronounced antioxidant activity.The development of antioxidant molecules is one of the desirable effects of the Maillard reaction.The antioxidative properties of MRPs produced by heat treatment of amino acid–sugar have been studied in model systems (Jayathil-akan &Sharma,2006).

The majority of studies have been carried out on the sugar–ami-no acid and sugar–protein model systems.Radiation processing enhances shelf-life and/or improves the microbiological safety of raw and processed food materials without compromising nutri-tional quality (WHO,1999).The majority of chemical changes caused due to radiation processing of food are similar to those of

other preservation methods (Diehl,1995).The chemical changes taking place during irradiation are the result of the direct effect of radiation on the food components or by indirect action,through reactive intermediates formed by radiolysis of water (Diehl,1995).The majority of these chemical changes are similar to those pro-duced by heat treatment.However,information on the formation of MRPs by radiation processing is scanty.Non-enzymatic brown-ing in gamma-irradiated aqueous solutions of different sugars with lysine has been reported (Oh et al.,2006).Formation of antioxidant compounds in sugar–amino acid solutions upon irradiation has also been reported recently from this laboratory (Chawla,Chander,&Sharma,2007).

Whey is an abundant by-product of the dairy industry.It is the portion of milk left after the manufacture of cheese.It consists of about 96%water but also contains valuable proteins and lactose.The disposal of whey is dif?cult due to its high biological oxygen demand.In developing countries whey is dumped into streams thereby polluting them.The objective of the present study was to investigate radiation-induced changes in whey protein disper-sion in terms of formation of MRPs and to examine their antioxi-dant activity.

2.Materials and methods 2.1.Chemicals

b -Carotene,2,2,-diphenyl-1-picryl hydrazyl (DPPH),thiobarbi-turi

c aci

d (TBA),nitroblu

e tetrazolium (NBT)and linoleic acid were

*Corresponding author.Tel.:+912225593296/25595374;fax:+912225505151/25519613.

E-mail address:spchawla@https://www.wendangku.net/doc/284698646.html,.in (S.P.Chawla).Food Chemistry 116(2009)

122–128

Contents lists available at ScienceDirect

Food Chemistry

j o u r n a l ho m e p a g e :w w w.e l s e v i e r.c o m /l o c a

te/foodchem

purchased from Sigma Chemical Co.(St.Louis,MO).All other chemicals used were of analytical grade and procured from HiMe-dia Laboratories(Mumbai,India)or Sisco Research Laboratories (Mumbai,India).

2.2.Preparation of radiation induced MRPs

Whey protein concentrate(WPC)solution was prepared in dis-tilled water to give a?nal concentration of1%.The WPC solutions were subjected to different doses of gamma-irradiation(0–100kGy)in a Gamma-Cell5000(BRIT,Mumbai)at a dose rate of 9.87kGy per hour.Dosimetry was performed by ceric-cerous dosimeter calibrated against Fricke’s dosimeter.Dosimetry inter-comparison was carried out with National Standards established by the Radiological Physics and Advisory Division(RP&AD),Bhabha Atomic Research Centre(BARC),Mumbai,India.

2.3.Spectrophotometric analyses

The radiation-treated whey protein dispersions were appropri-ately diluted and absorbance at284nm(early Maillard reaction products)and420nm(late Maillard reaction products)were mea-sured.Fluorescence of samples was determined after100-fold dilu-tion.The?uorescence intensity was measured at an excitation wavelength of365nm and emission wavelength of440nm using a?uorescence spectrophotometer(Chawla et al.,2007).

2.4.Measurement of colour

The evaluation of colour of the gamma-irradiated whey protein dispersion was carried out using a colorimeter(MiniScan MS/S-4000S;Associates Laboratory Inc.,Reston,VA)according to the CIE Lab scale.The system provides the values of three colour components:L*(black–white component,luminosity),and the chromaticity coordinates,a*(+red toàgreen component)and b* (+yellow toàblue component)(Hunter,1942).Samples were placed into a cell.The samples were illuminated with D65-Arti?-cial Daylight(10°standard angle),according to conditions pro-vided by the manufacturer.The E index is calculated from the equation:

E?eL?2ta?2tb?2T1=2

and chroma value according to the equation:

C?ea?2tb?2T1=2

Each colour value reported was the mean of four determina-tions at25±3°C.

2.5.Determination of reducing power

Reducing power was determined by the ferricyanide method of Yen and Duh(1993).Appropriately diluted sample(1ml)was added to2.5ml of phosphate buffer(200mM,pH6.6)followed by2.5ml of1%potassium ferricyanide.The reaction mixture was incubated for20min in a water bath at50°C.After incubation, 2.5ml of10%trichloroacetic acid(TCA)was added,followed by cen-trifugation at3000rpm for10min.The upper layer(5ml)was mixed with5ml distilled water and1ml of0.1%ferric chloride. Absorbance of the resultant solution was measured at700nm.A high absorbance was indicative of strong reducing power.

2.6.Determination of DPPH radical-scavenging activity

Electron-donating ability of radiation-induced MRPs was deter-mined by employing DPPH radical-scavenging assay(Blois,1958).To a1ml aliquot of appropriately diluted solution,1ml of etha-nolic DPPH solution(0.2mM)was added.The mixture was vor-texed and left to stand at ambient temperature for30min.A reaction mixture containing1ml distilled water and1ml of etha-nolic DPPH solution(0.2mM)served as the control.The absor-bance of the solution was measured spectrophotometrically at 517nm.The percentage of DPPH scavenging was calculated from the equation:

Radical scavenging activitye%T?100?eA controlàA sampleT=eA controlTwhere A control is the absorbance of the control and A sample the absor-bance of the sample.

2.7.Determination of antioxidant activity by b-Carotene bleaching assay

Antioxidant activity of the aqueous solution was determined by a b-carotene/linoleic acid system,as described by Matthaus(2002). Brie?y,1ml of b-carotene solution(1mg/ml in chloroform),40l l of linoleic acid,and400l l of Tween80were transferred into a round-bottomed?ask.Chloroform from the sample was evapo-rated using a stream of nitrogen.Then100ml of distilled water was added slowly to the residue and vigorously agitated to give a stable emulsion.To an aliquot of4.5ml of this emulsion,500l l of appropriately diluted samples were added.To the control reac-tion mixtures,500l l of distilled water were added.Absorbance was measured immediately at470nm.The tubes were placed in a water bath at50°C and the absorbance was measured after 120min.Antioxidant activity index(AAI)was calculated as

AAI?100?

A se0TàA se120T

A be0TàA be120T

where A s(0)is absorbance of the sample at0min,A s(120)is the absor-bance of the sample at120min,A b(0)is the absorbance of the con-trol at0min,A b(120)is the absorbance of the control at120min. 2.8.Determination of hydroxyl radical-scavenging activity

Hydroxyl radical-scavenging activity of radiation-induced MRPs was determined according to the modi?ed method of Halliwell, Gutteridge and Aruoma(1987).To1ml of the appropriately di-luted sample,1ml phosphate buffer(0.1M pH7.4)containing 1mM ferric chloride,1mM EDTA,1mM ascorbic acid,30mM deoxyribose,and20mM hydrogen peroxide were added.After incubation at37°C for90min,2ml of2%(w/v)TCA and2ml of 1%(w/v)TBA was added.The reaction mixture was heated in a boiling water bath for15min.The absorbance of the pink colour that developed was measured at532nm using a spectrophotome-ter.The percentage of hydroxyl radical-scavenging activity was calculated as:

%inhibition?100??eA ControlàA SampleT=A Control

where A Control is the absorbance of the control and A Sample the absor-bance of the sample.

2.9.Measurement of superoxide anion scavenging activity

Superoxide anion scavenging activities of radiation induced MRPs were determined according to the method of Liu,Ooi,and Chang(1997)with some modi?cations.The reaction mixture con-sisted of1ml of NBT(156l M in0.1M potassium phosphate buffer pH7.4), 1.0ml of nicotinamide adenine dinucleotide reduced (NADH468l M in0.1M potassium phosphate buffer pH7.4)and

S.P.Chawla et al./Food Chemistry116(2009)122–128123

0.5ml of appropriately diluted sample.The reaction was initiated by addition of100l l of phenazine methosulphate(PMS60l M in 0.1M potassium phosphate buffer pH7.4)to the mixture.The tubes were incubated at ambient temperature for5min.and the absorbance was measured at560nm.Decreased absorbance of the reaction mixture indicated increased superoxide anion scav-enging activity.The percentage inhibition of superoxide anion gen-eration was calculated using the following formula:

%inhibition?100?eA0àA sT

where A0is the absorbance of the control and A s is the absorbance of the sample.

2.10.Determination of iron chelation activity

The ferrous ion chelation potentials of radiation-induced MRPs were investigated by estimating the ferrous iron–ferrozine com-plex at562nm(Decker&Welch,1990).Brie?y,the reaction mix-ture consisted of1.0ml of appropriately diluted sample,3.7ml distilled water,0.1ml ferrous chloride(2mM)and0.2ml ferrozine (5mM).The reaction mixture containing1ml of distilled water in-stead of sample served as control.Tubes were incubated at ambi-ent temperature for20min.The absorbance of the colour developed was measured at562nm.A high ferrous chelation abil-ity of sample results in low absorbance at562nm.The ability of sample to chelate ferrous ions was calculated using the following equation:

Chelation activitye%T?100?eA0àA ST

where A o is absorbance of the control and A s is the absorbance of the sample.

2.11.Determination of free amino group content

Free amino group content was determined according to the method of Benjakul,Lertittikul,and Bauer(2005).Appropriate volume of sample was mixed with2ml of200mM phosphate buffer(pH8.2)and1ml of0.01%TNBS solution was added.The reaction mixture was vortexed and incubated in water bath at 50°C for30min in the dark.The reaction was stopped by adding 2ml of100mM sodium sul?te solution.The tubes were allowed to cool at room temperature.The absorbance was measured at 420nm.

2.12.SDS–polyacrylamide gel electrophoresis(SDS–PAGE)

SDS–PAGE was performed using4%stacking gel and10%run-ning gel,according to the method of Laemmli(1970),with a verti-cal gel electrophoresis unit(Mini-Kin,Techno Source,Mumbai, India).Protein(25l g)was applied to the gel.The electrophoresis was carried out at20mA.After separation,protein bands were stained using Coomassie Brilliant Blue R-250(0.2%)in25%metha-nol and10%acetic acid.Destaining was performed using40% methanol and10%acetic acid.

2.1

3.Fractionation of MRPs

The whey protein dispersion was subjected to fractionation using ethanol(Jing&Kitts,2004).The samples were mixed with absolute ethanol(9:1v/v)and allowed to stand for2h at4°C. The MRP ethanol suspension was centrifuged at5000g for10mins. The resulting supernatant which contained low molecular weight MRPs was decanted and separated from the precipitate.Both eth-anol-soluble supernatant and precipitate were analysed for DPPH radical-scavenging activity.

2.14.Statistical Analysis

All results given in the?gures are mean±standard deviation. Differences between the variables were tested for signi?cance by one-way ANOVA with Tukey’s post test using GraphPad InStat ver-sion3.05for Windows95,GraphPad Software,San Diego,CA.Dif-ferences at p<0.05were considered to be signi?cant.

3.Results

In the present study an aqueous suspension of whey protein concentrate was used as a representative of a natural food pro-tein/sugar mixture,to investigate the effect of radiation processing. Effect of gamma-irradiation on spectrophotometric analysis of whey protein dispersion is shown in Fig.1.A sharp increase in UV absorbance at284nm of samples was observed with irradia-tion dose(r2=0.99)(Fig.1A).The UV absorption of samples irradi-ated at100kGy was corrected for dilution factor and the value was found to be69.3,suggesting formation of UV-absorbing intermedi-ate products upon irradiation.The Maillard reaction is associated with development of UV-absorbing intermediate compounds,prior to generation of brown pigments.This increased UV absorbance is attributed to decomposition of sugars by dehydration and sugar fragmenation(Hodge,1953).Dose-dependent formation of UV-absorbing compounds upon irradiation of sugar/amino acid solu-tions has been reported previously(Chawla et al.,2007;Oh et al., 2006).UV-absorbing intermediate compounds are formed prior to heat-induced MRPs(Ajandouz,Tchiakpe,Ore,Benajiba,&Puig-server,2001).

It can be seen that the browning intensity,as measured by A420‘nm for whey protein dispersion increased(r2=0.99)with the radiation dose(Fig.1A).Dose-dependent increase in browning in sugar/amino acid solution has been reported previously(Chawla et al.,2007;Oh et al.,2006).These?ndings are in concurrence with other studies where browning of protein/sugar solutions due to heat-induced Maillard reaction is reported(Benjakul et al.,2005; Jing&Kitts2002).Development of brown colour,due to the forma-tion of chromophores,has been widely studied in different model systems,and studies on melanoidin formation have been summa-rised(Rizzi,1997).

The extent of browning due to Maillard reaction is regularly measured as a single wavelength absorbance.Wavelengths be-tween360and470nm are frequently used for the purpose.How-ever,it may not be a reliable way to describe visual colour changes, in terms of the visual properties of the coloured compounds.We attempted to correlate visual colour with browning,by applying the colour parameters provided by a tristimulus colourimeter. The CIE Lab system established a system of numerical coordinates to locate individual colour in uniform visual colour spacing.The re-sults of the evaluation of colour of the gamma-irradiated whey protein dispersion are shown in Table1.It can be seen that there was no signi?cant change in a*value whereas b*value increased with irradiation dose.These?ndings suggest a net increase in yel-low–brown colour as a result of radiation treatment of whey pro-tein dispersion.The colour index(E),which is in?uenced by L*,a* and b*values.It was observed that L*values decreased upon irradi-ation due to loss of lightness whereas b*values increased upon irradiation,due to formation of yellow–brown colour.The E index could describe how far apart two colours are in the colour space.It was seen that there was a slow increase in E index upon irradia-tion,as a net effect of reduced lightness and increased yellow–brown colour.The parameter C*indicates the degree of saturation,

124S.P.Chawla et al./Food Chemistry116(2009)122–128

purity or intensity of visual colour and is de?ned as the degree of departure from grey(a*and b*=0)towards pure chromatic colour. The increased values of C*signify that the irradiated model system shows more red or yellow characteristics and no saturation was observed at the doses investigated in the present study.In the heat-induced Maillard reaction of a sugar/amino acid model sys-tem it was reported that E index decreases signi?cantly with heat-ing time,whereas,the C*value increases with heating time to a maximum after which the colour of the system becomes more complicated(Morales&Jimenez-Perez,2001).

Development of?uorescent compounds has been reported to be associated with heat-induced Maillard reaction(Jing&Kitts,2000, 2002).In the present study dose-dependent formation of?uores-cent compounds was observed in irradiated whey protein disper-sion(Fig.1B).These?uorescent compounds are known to be precursors of brown pigments formed during the Maillard reaction. Similar results in heat-induced the Maillard reaction in a model system consisting of bovine serum albumin and sugar have been reported,where the?uorescence intensity of the system increased with time(Yeboah,Alli,&Yaylayan,1999).However,in a number of other studies it has been reported that?uorescence intensity reached a maximum during heat treatment and further heating re-sulted in a gradual decrease in intensity(Benjakul et al.,2005;Jing &Kitts,2002).

Iron reducing power of the whey protein dispersion before and after subjecting to gamma-irradiation is shown in Fig.1B.It was seen that non-irradiated whey protein dispersion had negligible reducing power,which increased signi?cantly(p<0.05)upon irradiation treatment.It has been reported that compounds responsible for reducing activity are formed during thermolysis of Amadori products in the primary phase of Maillard reactions (Hwang,Shue,&Chang,2001)or could be heterocyclic products of Maillard reaction or caramelisation of sugars(Charurin,Ames, &Castiello,2002).Possibly,gamma-irradiation induces similar changes in whey protein dispersion,resulting in the formation of products which contribute towards the reducing power. Heat-induced MRPs from xylose/lysine(Yen&Hsieh,1995),glu-cose/glycine(Yoshimura,Ujima,Watanabe,&Nakazawa,1997) and porcine plasma protein/glucose models(Benjakul et al., 2005;Lertittikul,Benjakul,&Tanaka,2007)possessed reducing power.

We estimated the effect of radiation dose on free amino groups in whey protein dispersion.In the present study a dose-dependent reduction in free amino groups was observed in irradiated whey protein dispersion(Fig.2A).The decrease in free amino groups was coincidental with increase in the browning intensity (Fig.1A).A reduction of free amino groups,which are major reac-tants of the Maillard reaction is also reported in other studies in su-gar/amino acid systems(Sun,Hayakawa,&Izumori,2004).

The changes in sugar content of whey protein dispersion,as a function of irradiation dose,are also shown in Fig.2A.In the pres-ent study a signi?cant dose-dependent decrease in the reducing sugar content was observed in irradiated whey protein dispersion. Reduction in reducing sugar content during heat-induced Maillard reaction in fructose/lysine(Ajandouz et al.,2001)and porcine pro-tein/glucose(Lertittikul et al.,2007)model systems has been reported.

Table1

Effect of gamma-irradiation on Hunter colour values of whey protein dispersion.

Irradiation dose L*a*b*c E

Control86.7 1.259.119.287.4

20kGy85.60.0912.712.787.0

40kGy84.3à0.8822.122.187.1

60kGy82.3à0.9730.130.187.6

80kGy81.4à0.9835.935.988.9

100kGy80.9à0.9837.637.689.2

L*(black–white component,luminosity),chromaticity coordinates,

a*(+red toàgreen component),

b*(+yellow toàblue component),

C=(a*2+b*2)1/2,

E=(L*2+a*2+b*2)1/2.

Each colour value reported was the mean of four determinations at25±3°C.

S.P.Chawla et al./Food Chemistry116(2009)122–128125

These results indicated the involvement of amino group and reducing sugar in formation of MRPs during irradiation treatment, as substantiated by the lower free amino groups and reducing sug-ars remaining upon irradiation treatment.

To evaluate the free radical-scavenging,whey protein disper-sions subjected to different doses of gamma-irradiation were al-lowed to react with stable DPPH free radical.The scavenging of DPPH free radical,indicating a positive antiradical activity,was fol-lowed by monitoring reduction in the absorbance at517nm.DPPH free radical-scavenging activity increased with the irradiation dose in whey protein dispersion(r2=0.90).In whey protein dispersion irradiated at40kGy it was observed to be33.8%(Fig.2B).Upon fur-ther irradiation to80kGy,the increase was not linear and tended to plateau at a higher irradiation dose.Capability of heat-induced MRPs to scavenge DPPH radical have been reported in a number of studies(Benjakul et al.,2005;Jing&Kitts,2002;Lertittikul et al.,2007;Morales&Jimenez-Perez,2001).In our previous stud-ies,on radiation-induced Maillard reaction in sugar/amino acid model system,similar?ndings were observed,where the radical-scavenging activity saturated with an irradiation dose of40kGy (Chawla et al.,2007).These?nding are also in agreement with pre-vious studies on heat-induced MRPs,where radical-scavenging activities tend to saturate after a certain heating time(Jing&Kitts, 2002;Lertittikul et al.,2007;Morales&Jimenez-Perez,2001).

It was observed that b-carotene bleaching was signi?cantly (p<0.05)inhibited in the presence of irradiated whey protein dis-persion,compared to that offered by its non-irradiated counterpart (Fig.2B).These?ndings indicated that irradiation of whey protein dispersion resulted in formation of compounds having signi?cant antioxidant potential.These?ndings are similar to our previous re-sults on radiation induced Maillard reaction in sugar/amino acid model system(Chawla et al.,2007).As in the case of DPPH radi-cal-scavenging,inhibition of b-carotene bleaching tended to max-imize at a higher irradiation dose.Synthesis of antioxidative compounds upon heat treatment of sugar/amino acid solutions is reported in a number of studies(Jayathilakan&Sharma,2006;Jing &Kitts,2002;Morales&Jimenez-Perez,2001;Yoshimura et al., 1997).

The hydroxyl radical is the most reactive of species and induces most severe damage to adjacent biomolecules,resulting in lipid peroxidation in biological systems.In the present study the Fenton reaction system was used in deoxyribose degradation by generat-ing hydroxyl radicals.The treatment of deoxyribose with Fenton reaction reagent resulted in a high rate of deoxyribose degradation. Hydroxyl radical-scavenging activity of irradiated whey protein dispersion was signi?cantly higher than that of its non-irradiated counterpart(Fig.3A).These?ndings revealed that compounds formed upon irradiation treatment of whey protein dispersion have the potential of being antioxidants in biological systems. Development of compounds capable of scavenging hydroxyl radi-cals and the utility of this test in studies to demonstrate in vitro hy-droxyl radical-scavenging activity of heat-induced MRPs has been reported(Jing&Kitts,2000,2002).

The superoxide radicals are generated by a number of biological reactions.Although they do not directly initiate lipid oxidation, superoxide radical anions are precursors of highly reactive hydro-xyl radical,which contributes towards lipid peroxidation in biolog-ical systems.Thus superoxide anion scavenging activity indirectly contributes towards antioxidant potential.Irradiated whey protein dispersion showed dose-dependent superoxide anion radical-scav-enging activity(Fig.3A).Our results are in agreement with a pre-vious study on heat induced MRPs formed from glucose/glycine that were reported to scavenge superoxide anion radical(Yoshim-ura et al.,1997).Formation of compounds that are capable of scav-enging hydroxyl and superoxide anion radicals,as result of radiation-induced Maillard reaction in sugar/amino acid model systems,has been reported(Chawla et al.,2007).

In contrast to DPPH radical-scavenging and inhibition of b-car-otene bleaching activity,scavenging of hydroxyl and superoxide anion radical did not stabilise at higher irradiation dose.These ?ndings probably suggest involvement of different compounds in various radical-scavenging reactions.

Metal chelation activity plays an important role in antioxidant action as it results in reduction in the concentration of the transi-tion metals required for lipid peroxidation.The Fe2+ion is the most powerful pro-oxidant amongst various species of metal ions.In the

126S.P.Chawla et al./Food Chemistry116(2009)122–128

present study we studied the effect of gamma-irradiation on fer-rous ion chelating activities of whey protein dispersion(Fig.3B). It can be seen that iron chelation activity of whey protein disper-sion signi?cantly(p<0.05)increased upon irradiation at20kGy. However,further irradiation did not result in any signi?cant in-crease in iron chelation activity.Formation of compounds that are able to chelate ferrous ions as a result of radiation-induced Maillard reaction in sugar/amino acid model systems,has been re-ported in our previous study(Chawla et al.,2007).Our?ndings are in concurrence with an earlier report where iron chelation activity was observed in glucose/glycine model system,as a result of MRPs formed due to heat treatment(Yoshimura et al.,1997).

The SDS–PAGE pattern of the whey protein dispersion subjected to different doses of gamma-irradiation is shown in Fig.4.The non-irradiated whey protein dispersion consisted of a number of pro-teins with molecular weight in the range of14–97kDa.Low molec-ular weight proteins( 14and20kDa)were highly predominant (Fig.4,lane2).Upon irradiation there was a dose-dependent reduction in low molecular weight bands with coincidental forma-tion of high molecular weight bands(Fig.4,lanes3–7).At irradia-tion doses of60kGy and above a high molecular weight band, which was unable to move in gel,was formed.These results sug-gested that there was a dose-dependent polymerisation of whey proteins upon irradiation.The formation of high molecular weight proteins during heat-induced Maillard reaction in b-lactoglobulin/ chitosan(Miralles,Martinez-Rodriguez,Santiago,Lagemaat,& Heras,2007)and porcine plasma protein/glucose model(Lertittikul et al.,2007)has been reported.The formation of cross-linked pro-tein chains during the advanced and?nal stages of Maillard reac-tion,and the types of cross-link involved have been widely studied in different model systems(Oliver,Melton,&Stanley, 2006).

The results of DPPH-scavenging activity of ethanol-fractionated

radiation-induced MRPs in whey protein dispersion as a function of irradiation dose are shown in Fig.5.It can be seen that both etha-nol-soluble supernatant and precipitate from non-irradiated whey protein dispersion did not yield any DPPH-scavenging activity. However,DPPH radical-scavenging activity was evident in both the fractions of irradiated samples.When comparison was made between the supernatant and precipitate from samples subjected to the same irradiation dose,it was observed that the radical-scav-enging activity was signi?cantly higher in the precipitate fraction. These?ndings suggested that the high molecular weight fraction contained more potent antioxidants than the low molecular weight fraction.These results are in agreement with a previous study on

Fig.4.SDS–PAGE protein pattern of gamma-irradiated whey protein dispersion.

Lane1Molecular weight markers;lanes2–7,whey protein dispersion subjected to

0,20,40,60,80and100kGy,respectively.

S.P.Chawla et al./Food Chemistry116(2009)122–128127

heat-induced MRPs where both DPPH as well as hydroxyl radical-scavenging activity were greater in the high molecular weight frac-tion compared to the low molecular weight fraction(Jing&Kitts, 2004).

4.Conclusion

Ionizing radiation,such as gamma rays,can be successfully em-ployed to produce MRPs in whey protein dispersion.The MRPs are probably produced because of a carbonyl-amine reaction,similar to heat-induced Maillard reaction.This study con?rms our earlier report that compounds of antioxidant potential are formed upon irradiation of glucose/amino acid solutions(Chawla et al.,2007). Covalent bonding of proteins to reducing sugars has been shown to alter their functional properties.Maillard reaction is one of the technologically feasible methods to prepare conjugates(Oliver et al.,2006).The results of the present study demonstrated the for-mation of MRPs with antioxidant potential when whey protein dis-persion was irradiated.The formation of protein conjugates is evident from the results.Further studies are needed to elucidate the mechanism and explore radiation as a tool to form protein con-jugates with novel functional properties.

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新型聚氨酯固化剂的研究与发展张修景(菏泽学院化学与化工系，山东菏泽274015) 摘要：阐述了颜色低于铁钴比色计1号，游离TDI含量小于0.5%，贮存稳定性达2年以上的新型聚氨酯固化剂的生产工艺；确定了含羟基丙烯酸树脂与该固化剂的质量比为：m(含羟基丙烯酸树脂)∶m(新型聚氨酯固化剂)=10∶4～6；分析了碱性物质是导致聚氨酯固化剂成胶的原因；提出了保证聚氨酯固化剂低色值、低游离TDI含量和高贮存稳定性的方法。关键词：新型聚氨酯固化剂；色值；游离TDI含量；稳定性 0.引言国内科研单位及相关企业、院校对于聚氨酯固化剂的研究做了大量工作，朱吕民[1]介绍了色泽为8号(铁钴比色计)TDI加成物的制法；彭红为，等[2-3]报道的产品的游离TDI含量高达3.0%～5.0%，配制的涂料在施工过程中对人体伤害很大，环境污染严重，不仅远远高出世界卫生组织游离TDI含量≤0.5%的要求，而且很难达到我国《室内装饰装修材料溶剂型木器涂料中有害物质限量》GB18581—2001强制标准中≤0.7%的规定。国外通常采用薄膜蒸发法，如Bayer公司采用该技术产品的游离TDI含量<0.5%。国内相关研究[4-10]对于降低游离TDI做了大量积极工作，并提出了在聚氨酯生产中推行清洁生产的建议和措施，但实现工业化生产的报道很少。赵文斌，等[10]的产品通过热重分析(TG)显示，改性TDI三聚体的热稳定性有一定下降。为此，本文研究了颜色低于铁钴比色计1号，游离TDI<0.5%，贮存稳定性达2年以上的TDI-TMP加成物，找到了该固化剂与含羟基丙烯酸树脂的最佳配比，可赋于漆膜多种优良的性能。 1.实验部分 1.1原料甲苯二异氰酸酯(TDI)：80/20，国产；三羟甲基丙烷(TMP)：美国产；乙酸丁酯：工业一级品，无水；二月桂酸二丁基锡、缩二脲：工业一级品；磷酸(85%)、三正丁基膦、对硝基苯甲酰氯：分析纯；氮气(99199%)。 1.2反应原理 TDI-TMP加成物主要是指3分子的甲苯二异氰酸酯(TDI)与1分子的三羟甲基丙烷(TMP)的加成物，反应如式1。 1.3方法新型聚氨酯固化剂的中试配方见表1。

石墨电极

石墨电极石墨电极(graphite electrode) 以石油焦、沥青焦为颗粒料，煤沥青为黏结剂，经过}昆捏、成型、焙烧、石墨化和机械加工而制成的一种耐高温的石墨质导电材料。石墨电极是电炉炼钢的重要高温导电材料，通过石墨电极向电炉输入电能，利用电极端部和炉料之间引发电弧产生的高温为热源，使炉料熔化进行炼钢，其他一些电冶炼或电解设备也常使用石墨电极为导电材料。2000年全世界消耗石墨电极100万t左右，中国2000年消耗石墨电极25万t左右。利用石墨电极优良的物理化学性能，在其他工业部门中也有广泛的用途，以生产石墨电极为主要品种的炭素制品工业已经成为当代原材料工业的重要组成部门。简史早在1810年汉佛莱?戴维(Humphry Davy)利用木炭制成通电后能产生电弧的炭质电极，开辟了使用炭素材料作为高温导电电极的广阔前景，1846年斯泰特(Stair)和爱德华(Edwards)用焦炭粉及蔗糖混合后加压成型，并在高温下焙烧从而制造出另一种炭质电极，再将这种炭质电极浸在浓糖水中以提高其体积密度，他们获得了生产这种电极的专利权。1877年美国克利夫兰(Cleveland)的勃洛希(C.F.Brush)和劳伦斯(https://www.wendangku.net/doc/284698646.html,wrence)采用煅烧过的石油焦研制低灰分的炭质电极获得成功。1899年普利查德(O.G.Pritchard)首先报道了用锡兰天然石墨为原料制造天然石墨电极的方法。1896年卡斯特纳(H.Y.Gastner)获得了使用电力将炭质电极直接通电加热到高温，而生产出比天然石墨电极使用性能更好的人造石墨电极的专利权。1897年美国金刚砂公司(Carborundum Co.)的艾奇逊(E.G.Acheson)在生产金刚砂的电阻炉中制造了第一批以石油焦为原料的人造石墨电极，产品规格为22mm×32m mX380mm，这种人造石墨电极当时用于电化学工业生产烧碱，在此基础上设计的“艾奇逊”石墨化炉将由石油焦生产的炭质电极及少量电阻料(冶

抗氧化因子与天然抗氧化剂研究综述

万方数据

抗氧化因子与天然抗氧化剂研究综述作者：乔凤云，陈欣，余柳青， QIAO Feng-yun， CHEN Xin， YU Liu-qing 作者单位：乔凤云,QIAO Feng-yun(浙江大学,生命科学学院,杭州,310029;中国水稻研究所,杭州 ,310006)，陈欣,CHEN Xin(浙江大学,生命科学学院,杭州,310029)，余柳青,YU Liu- qing(中国水稻研究所,杭州,310006) 刊名：科技通报英文刊名：BULLETIN OF SCIENCE AND TECHNOLOGY 年，卷(期)：2006,22(3) 被引用次数：9次参考文献(22条) 1.Hallwell B Free Radical and antioxidation 1990 2.Wu G;Fang Y Z;Yang S Glutathione metabolism in antimals:nutritional regulation and physiologyical signi-ficance 2003 3.Jacob;Robert A The integrated antioxidant system 1995(05) 4.Arora A;Nair M G;Strasburg G M Antioxidant activities of isoflavones and their metabolites in a liposomel system 1998 5.Kameoka S;Leavitt P;Chang C Expression of antioxidant proteins in human intestinal Caco-2 cells treated with dietary flavonoids[外文期刊] 1999 6.句海松抗氧化剂研究进展 1990(12) 7.Ng T B;Liu F;Wang Z T Antioxidative activity of nature products from plants[外文期刊] 2000(08) 8.Morel I;Cillard J;Lescoat G Antioxidant and free radical scavenging activities of the iron chelators pyoverdin and hydroxypyrid-4-ones in iron-loaded hepatocyte cultures:comparison of their mechanism of protection with that of desferrioxamine 1992(05) 9.Ozturk G;Erol D D;Uzbay T Synthesis of 4(1H)-pyridinone derivatives and investi-gation of analgesic and anti-inflammatory activities 2001(04) 10.Huang D R;Proctor G R;Driscoll S D Pyridones as potential antitumor agents Ⅱ:4-pyridones and bioisosteres of 3-acetoxy-2-pyridone 1980(03) 11.Cragg L;Hebbel R P;Miller W The iron chelator L1 potentiates oxidative DNA damage in iron-loaded liver cells 1998(02) 12.Sadrzadeh S M;Nanji A A;Price P L The oral iron chelator,1,2-dimethyl-3-hydroxypyrid -4-one reduces hepatic-free iron,lipid peroxidation and fat accumulation in chronically ethanol-fed rats 1994(02) 13.Helliwell B;Jello M C Gutteridge Free Radicals in Biology and Medicine 1985 14.Wickens;Andrew P Ageing and the free radical theory[外文期刊] 2001(03) 15.Vimala S & Adenan MI Malaysian tropical forest medicinal plants:a source of natural antioxidants 1999 16.Loliger Free Radicals and food additive 1991 17.Hudson B J F Food Antioxidants.Elsevier 1990 18.LOLIGER Free Radicals and Food Additive 1991 19.Arora A;Byrem T M;Nair M G Modulation of liposomeal membrane fluidity by flavonoids and

石墨电极的生产工艺流程和质量指标的及消耗原理知识讲解

石墨电极的生产工艺流程和质量指标的及消耗原理

目录一、石墨电极的原料及制造工艺二、石墨电极的质量指标三、电炉炼钢简介及石墨电极的消耗机理石墨电极的原料及制造工艺 ●石墨电极是采用石油焦、针状焦为骨料，煤沥青为粘结剂，经过混捏、成型、焙烧、浸渍、石墨化、机械加工等一系列工艺过程生产出来的一种耐高温石墨质导电材料。石墨电极是电炉炼钢的重要高温导电材料，通过石墨电极向电炉输入电能，利用电极端部和炉料之间引发电弧产生的高温作为热源，使炉料熔化进行炼钢。其他一些冶炼黄磷、工业硅、磨料等材料的矿热炉也用石墨电极作为导电材料。利用石墨电极优良而特殊的物理化学性能，在其他工业部门也有广泛的用途。生产石墨电极的原料有石油焦、针状焦和煤沥青 ●石油焦是石油渣油、石油沥青经焦化后得到的可燃固体产物。色黑多孔，主要元素为碳，灰分含量很低，一般在0.5%以下。石油焦属于易石墨化炭一类，石油焦在化工、冶金等行业中有广泛的用途，是生产人造石墨制品及电解铝用炭素制品的主要原料。 ●石油焦按热处理温度区分可分为生焦和煅烧焦两种，前者由延迟焦化所得的石油焦，含有大量的挥发分，机械强度低，煅烧焦是生焦经煅烧而得。中国多数炼油厂只生产生焦，煅烧作业多在炭素厂内进行。 ●石油焦按硫分的高低区分，可分为高硫焦（含硫1.5%以上）、中硫焦(含硫0.5%-1.5%)、和低硫焦(含硫0.5%以下)三种，石墨电极及其它人造石墨制品生产一般使用低硫焦生产。 ●针状焦是外观具有明显纤维状纹理、热膨胀系数特别低和很容易石墨化的一种优质焦炭，焦块破裂时能按纹理分裂成细长条状颗粒（长宽比一般在1.75以上），在偏光显微镜下可观察到各向异性的纤维状结构，因而称之为针状焦。 ●针状焦物理机械性质的各向异性十分明显, 平行于颗粒长轴方向具有良好的导电导热性能，热膨胀系数较低，在挤压成型时，大部分颗粒的长轴按挤出方向排列。因此，针状焦是制造高功率或超高功率石墨电极的关键原料，制成的石墨电极电阻率较低，热膨胀系数小，抗热震性能好。 ●针状焦分为以石油渣油为原料生产的油系针状焦和以精制煤沥青原料生产的煤系针状焦。 ●煤沥青是煤焦油深加工的主要产品之一。为多种碳氢化合物的混合物，常温下为黑色高粘度半固体或固体，无固定的熔点，受热后软化，继而熔化，密度为1.25－1.35g/cm3。按其软化点高低分为低温、中温和高温沥青三种。中温沥青产率为煤焦油的54－56％。煤沥青的组成极为复杂，与煤焦油的性质及杂原子的含量有关，又受炼焦工艺制度和煤焦油加工条件的影响。表征煤沥青特性的指标很多，如沥青软化点、甲苯不溶物（TI）、喹啉不溶物（QI）、结焦值和煤沥青流变性等。

腰果酚应用研究进展..

12应用化学（职教本科1班彭思20120651 腰果酚应用研究进展摘要：本文从官能团改性方面，综述了近几年国内外腰果酚衍生物的化学合成及在材料与精细化学品中的潜在应用，其中包括腰果酚酚羟基、腰果酚苯环及腰果酚侧链的改性。关键词：腰果酚;腰果壳油;衍生物;应用;进展前言：随着全球化石资源日趋减少，可再生资源的开发利用越来越引起人们的重视[1]。腰果壳液(CNSL)是腰果加工中的一种副产品，其含量约占腰果的25%-30%，世界年产量约50万吨，是一种价廉丰富的可再生资源[2-3]。CNSL 的最主要成分是腰果酚(cardanol)(1)，含量可达90%。从结构来看，腰果酚属于苯酚的衍生物，在苯酚的间位被15个碳的直链(含0-3个碳碳双键)所取代(图1)(如无特殊说明，本文其它图中的R基团都代表腰果酚的侧链)。腰果酚可改性合成很多衍生物，包括功能小分子与聚合物，它们在涂料、摩擦材料、抗氧化剂、杀虫杀菌剂等方面都极具应用价值[4]。本文主要从腰果酚所含的三种官能团出发，总结通过酚羟基、苯环、不饱和侧链上的反应来制备各种有价值的腰果酚衍生物。 1利用腰果酚的羟基制备腰果酚衍生物 1.1腰果酚的酯类衍生物腰果酚分子中含有活泼的酚羟基，可通过酯化、醚化反应制备相应的衍生物。例如张中云等[5]在-15℃左右使腰果酚与ClCN反应，生成腰果酚氰酸酯(2)，2再与双酚A型氰酸酯(NCO-BPA-OCN)反应，制得了新型热固性树脂(图2)。由于树脂中引进了腰果酚所含的15个碳的柔性链，有效地提高了氰酸酯树脂的柔韧性，同时提高了其介电性能和耐吸水性能。

林金火课题组[6]用马来酸酐和腰果酚反应得到马来酸腰果酚单酯，然后与乙二醇进一步发生酯化反应 (图3)，最后将酯化产物进行缩甲醛化反应，合成了同时具有软段结构(顺丁烯二酸乙二醇酯结构单元)和硬段结构(酚醛结构单元)的多羟基腰果酚醛树脂，该树脂具有优良的涂膜性能；所得的多羟基腰果酚醛树脂也可与聚氨酯预聚体组成性能优良的双组分聚氨酯漆，可改善普通腰果漆的柔韧性和附着力。为了制备新型抗氧化剂，Lomonaco等[7]用腰果酚和强心酚(cardol,腰果壳油的另一种成分)与二乙氧基硫代磷酰氯反应，制备了相应的硫代磷酸酯化合物（3）和（4）(图4)。将所制硫代磷酸酯在聚甲基丙烯酸甲酯中掺入1%的量，结果聚合物的热稳定性提高了很多。特别是化合物4中既含有硫代磷酸酯结构，又含有酚羟基结构，同时具有一类和二类抗氧化剂的功能，因此对材料的热稳定性提高最明显。

聚氨酯

聚氨酯基本理论知识一. 聚氨酯(polyurethane)大分子主链上含有许多氨基甲酸酯基：它由二（或多）异氰酸酯、二（或多）元醇与二（或多）元胺通过逐步聚合反应生成，除了氨基甲酸酯基(简称为氨酯基）外，大分子链上还往往含有醚基、酯基、脲基、酰胺基等基团，因此大分子间很容易生成氢键。二.聚氨酯主要原料 N H C O O O C O O NH O NH NH O

1、异氰酸酯及其结构特征一、结构特点在分子结构中含有异氰酸酯基团(－N＝C＝O）的化合物，均称为异氰酸酯（isocyanate）,其结构通式如下：R－（NCO）n式中R为烷基、芳基、脂环基等；n＝1、2、3….整数。在聚氨酯材料合成中，主要使用n≥2的异氰酸酯化合物。二、异氰酸酯的分类（1）异氰酸酯基团数量 1.异氰酸酯异氰酸酯（Isocyanate）是一大类含有异氰酸基（—N=C=O）的有机化合物。异氰酸酯基由于其累积双键和碳原子两边的电负性很大的氮氧原子作用，使之具有很高的反应活性，能与绝大多数含活泼氢的物质发生反应。常用的异氰酸酯主要有芳香族类和脂肪类两种。⑴芳香族类的主要有：TDI（2, 4—甲苯二异氰酸酯或2, 6—甲苯二异氰酸酯）、MDI（二苯基甲烷- 4, 4’二异氰酸酯）、NDI （1, 5—萘二异氰酸酯）、PAPI（多亚甲基多苯基多异氰酸酯）等；芳香族多异氰酸酯合成的聚氨酯树脂户外耐候性差，易黄变和粉化，属于“黄变性多异氰酸酯”，但价格低，来源方便，在我国应用广泛，如TDI常用于室内涂层用树脂；聚氨酯树脂中90%以上属于芳香族

多异氰酸酯。与芳基相连的异氰酸酯基对水和羟基的活性比脂肪基异氰酸酯基团更活泼。基于TDI 的聚氨酯由于高的苯环密度，其力学性能也较脂肪族多异氰酸酯的聚氨酯更为优异。以下是一些常用的产品。（1）甲苯二异氰酸酯（tolulene diisocyanate ，TDI ）甲苯二异氰酸酯是最早开发、应用最广、产量最大的二异氰酸酯单体；根据其两个异氰酸酯（—NCO ）基团在苯环上的位置不同，可分为2,4-甲苯二异氰酸酯（2,4-TDI,简称2,4-体）和2，6-甲苯二异氰酸酯（2,6-TDI ，2,6-体）。室温下，甲苯二异氰酸酯为无色或微黄色透明液体，具有强烈的刺激性气味。市场上有3种规格的甲苯二异氰酸酯出售，T-65为2,4-TDI 、2,6-TDI 两种异构体质量比为65%/35%的混合体；T-80为2,4-TDI 、2,6-TDI 两种异构体质量比为80%/20%的混合体，其产量最高、用量最大，性价比高，涂料工业常用该牌号产品；T-100为2，4-TDI 含量大于95%的产品，2，6-TDI 含量甚微，其价格较贵。2,4-TDI 其结构存在不对称性，由于－CH3的空间位阻效应，4位上的－NCO 的活性比2位上的－NCO 的活性大，50℃反应时相差约8倍，随着温度的提高，活性越来越靠近，到100 ℃时，二者即具有相同的活性。因此，设计聚合反应时，可以利用这一特点合成出结构规整的聚合物。TDI 的弱点是蒸汽压大，易挥发，毒性大，通常将其转变成齐聚物（oligomer ）后使用；而且由其合成的聚氨酯制品存在比较严重的黄变性。黄变性的原因在于芳香族聚氨酯的光化学反应，生成芳胺，进而转化成了醌式或偶氮结构的生色团。2,4-TDI 凝固点6-20度，TDI 的含量越高凝固点。 NCO CH 3NC O O CH 3 OCN 2,6-TDI 2,4-TDI

碳素材料简介

碳素材料简介炭和石墨材料是以碳元素为主的非金属固体材料，其中炭材料基本上由非石墨质碳组成的材料，而石墨材料则是基本上由石墨质碳组成的材料。为了简便起见，有时也把炭和石墨材料统称为炭素材料（或碳材料）。主要分类：碳素散热片是以不干胶的形色直接将碳素散热片贴在芯片表面，碳素散热片因其柔软可与所贴附对象十分紧密的粘合，另外因其高热传导性（树脂的5-15倍）、横向的高热传导性（铜的两倍），与传统使用中的导热硅胶、硅胶片、金属片等比较，高碳素散热片能将热量均匀扩散更大幅度的散热。高热传导平面用散热片：利用其平面的高热传导性（铜的两倍），可将热迅速传递到金属壳以及散热型材上，降低发热点的温度，从而达到更好的散热效果。炭素制品按产品用途可分为石墨电极类、炭块类、石墨阳极类、炭电极类、糊类、电炭类、炭素纤维类、特种石墨类、石墨热交换器类等。石墨电极类根据允许使用电流密度大小，可分为普通功率石墨电极、高功率电极、超高功率电极。炭块按用途可分为高炉炭块、铝用炭块、电炉块等。炭素制品按加工深度高低可分为炭制品、石墨制品、炭纤维和石墨纤维等。炭素制品按原

料和生产工艺不同，可分为石墨制品、炭制品、炭素纤维、特种石墨制品等。炭素制品按其所含灰分大小，又可分为多灰制品和少灰制品（含灰分低于l％）。我国炭素制品的国家技术标准和部颁技术标准是按产品不同的用途和不同的生产工艺过程进行分类的。这种分类方法，基本上反映了产品的不同用途和不同生产过程，也便于进行核算，因此其计算方法也采用这种分类标准。下面介绍炭素制品的分类及说明。主要制品碳素行业的上游企业主要有：1、无烟煤的煅烧企业；2、煤焦油加工生产企业；3、石油焦生产及煅烧企业。炭和石墨制品： (一)石墨电极类主要以石油焦、针状焦为原料，煤沥青作结合剂，经煅烧、配料、混捏、压型、焙烧、石墨化、机加工而制成，是在电弧炉中以电弧形式释放电能对炉料进行加热熔化的导体，根据其质量指标高低，可分为普通功率、高功率和超高功率。石墨电极包括：（1）普通功率石墨电极。允许使用电流密度低于17A／厘米2的石墨电极，主要用于炼钢、炼硅、炼黄磷等的普通功率电炉。（2）抗氧化涂层石墨电极。表面涂覆一层抗氧化保护层的石墨电极，形成既能导电又耐高温氧化的保护层，降低炼钢时的电极消耗。

(整理)体外诊断试剂分析性能评估系列指导原则.

附件：《体外诊断试剂分析性能评估系列指导原则（征求意见稿）》

目录 1.体外诊断试剂分析性能评估指导原则――编制说明 2.体外诊断试剂分析性能评估指导原则——检测限 3.体外诊断试剂分析性能评估指导原则——线性范围 4.体外诊断试剂分析性能评估指导原则——可报告范围 5.体外诊断试剂分析性能评估指导原则——准确度（回收实验） 6.体外诊断试剂分析性能评估指导原则——准确度（方法学比对） 7.体外诊断试剂分析性能评估指导原则——精密度 8.体外诊断试剂分析性能评估指导原则——干扰实验 9.体外诊断试剂分析性能评估指导原则——稳定性 10.体外诊断试剂分析性能评估指导原则——参考值（参考区

间）附件1：体外诊断试剂分析性能评估指导原则编制说明《体外诊断试剂注册管理办法（试行）》颁布后，体外诊断试剂产品的注册过程中要求提供申报产品的分析性能评估资料，产品性能评估是产品研发、制定产品标准等过程的重要技术支持研究过程，并可能对产品的质量造成一定的影响。目前国际上对体外诊断试剂的性能评估通常是以美国临床实验室标准化组织（Clinical and Laboratory Standards Institude以下称为CLSI）的相关标准为依据，也是美国FDA 推荐采用的评价标准，但我国还没有相关的标准及指导原则的要求。为进一步明确体外诊断试剂分析性能评估的技术要求，

我中心组织有关专家起草产品分析性能评估指导原则，以明确体外诊断试剂产品性能评估的技术要求。体外诊断试剂产品性能评估包括检测限、线性范围、可报告范围、准确度（回收实验）、准确度（方法学比较）、精密度、干扰实验、稳定性、参考区间共九个项目。起草的主要依据CLSI发布的以下标准: 1. C28-A2: How to define and determine reference intervals in the clinical laboratory; Approved Guideline-Second Edition. 2. EP5-A: Evaluation of precision performance of clinical chemistry devices; Approved Guideline. 3. EP6-A: Evaluation of the linearity of quantitative measurement procedures; A Statistical Approach; Approved Guideline. 4. EP7-A: Interference testing in clinical chemistry; Approved Guideline. 5. EP9-A2: Method comparison and bias estimation using patient samples; Approved Guideline-Second Edition. 每项性能的主要研究方法均采用以上标准和国内实际采用的评价方法相结合的方法。我中心对于专家起草的指导原则的初稿进行了适当的文字调整，之后将分析性能评估指导原则发给十位相关专业的专家征求意见。意见返回后我们对专家的回复意见进行了