fruit seeparamesel wibiodieuse in

. The physicochemical properties and fatty acid methyl ester concentrationsyzed. The experimental study revealed that 50 C temperature of reaction,

Biodiesel, a promising renewable substitute source of fuel

depletion and environmental degradation [14]. Even though itwas identied in the beginning of 20th century by Rudolf Diesel,extensive researches have been started in the tail end of 20thcentury, when the demand for fossil fuel increased [58]. Biodieselhas gained greater attention because of the advantages such as

unburnt hydrocarbon and (iv) lower sulfur and aromatic content.l, because of dis-r viscosityaddressed

Through persistent and intensive research, some of theproblems have already been addressed. An antioxidant acan be used to increase the long term storage stability. Oxygantioxidant and cetane improving additives can be used to reducethe NOx emission [1418]. As most of the feed stocks used forbiodiesel are edible and the cost of raw material is very high tothe tune of 6080% of the total cost, it becomes essential now adays to identify new and underutilized feedstock for biodiesel pro-duction [1923]. To overcome the above problems, researchershave turned focusing more attention on non-edible oils such as

Corresponding author at: Department of Mechanical Engineering, B.S. AbdurRahman University, Vandalur, Chennai 600 048, Tamil Nadu, India. Tel.: +919942167709; fax: +91 44 22750520.

E-mail address: sathish.rajamanickam@gmail.com (R. Sathish Kumar).

Fuel 140 (2015) 9096

Contents lists availab

Fue

.eproduced from tree born oils, vegetable based oils, fats of animalsand even waste cooking oil has been identied as one of the keysolutions for the alarming global twin problems of fossil fuel

However, still it is not fully replacing fossil dieseadvantages such as higher NOx emission, higheoxidative and storage stability which need to behttp://dx.doi.org/10.1016/j.fuel.2014.09.1030016-2361/ 2014 Elsevier Ltd. All rights reserved., lower[913].abovedditiveenated,Keywords:Manilkara zapotaOptimizationTaguchi methodBiodieselTransesterication

90 min of time of reaction, 6:1 M ratio of methanol to oil and 1 wt% of concentration of catalyst arethe optimal process parameters. Also the study revealed that out of the four parameters considered,methanol to oil molar ratio is most effective in controlling the optimal biodiesel production. The optimalconditions yielded 94.83% of biodiesel. The biodiesel MZME produced with the optimized processparameters meets the global standards for biodiesel EN 14214 and hence could be considered as asuitable substitute for fossil diesel in unmodied diesel engine applications.

2014 Elsevier Ltd. All rights reserved.

1. Introduction (i) being renewable and biodegradable, (ii) higher cetane number,(iii) lower emission of carbon monoxide, particulate matters andAccepted 25 September 2014Available online 5 October 2014 eters of transesterication

were experimentally analh i g h l i g h t s

Development of a new biodiesel from Optimization of four major inuencing Report on production of the new biodi Physicochemical properties of the new A new renewable source of energy for

a r t i c l e i n f o

Article history:Received 17 April 2014Received in revised form 25 September2014ds which is not yet reported in literatures.eters of transesterication of the new oil using Taguchi method.th optimized process parameters and its physiochemical properties.sel meeting the requirements of EN 14214 standards for biodiesel.unmodied diesel engine applications.

a b s t r a c t

In this work, the optimization of transesterication process parameters for the production of ManilkaraZapota Methyl Ester (MZME) has been studied. Molar ratio of methanol to oil, time of reaction,temperature of reaction, and concentration of catalyst were the four parameters considered in the study.Taguchi experimental design was used for the optimization of the above mentioned four process param-aDepartment of Mechanical Engineering, B.S. Abdur Rahman University, Vandalur, Chennai 600 048, Indiab Institute for Energy Studies, Anna University, Chennai 600 025, IndiaOptimization of biodiesel production fromusing Taguchi method

R. Sathish Kumar a,, K. Sureshkumar a, R. Velraj b

journal homepage: wwwManilkara zapota (L.) seed oil

le at ScienceDirect

l

lsevier .com/locate / fuel

Pongamia, Jatropha, rubber seed, soap seed and neem seed andCamelina [2428].

Manilkara zapota, popularly known as sapodilla, a forest treewith long life span is mostly found in southern Mexico, Caribbeanand Central America. It is also cultivated in larger scale in India,Thailand, Cambodia, Malaysia, Indonesia, Bangladesh mainly forits fruit. It is known as chikoo (chiku) in Northern India, and sapotain southern parts of India. It is evergreen tree grows in wide rangeof climatic conditions and all tropical lands like wet tropics to drycool subtropical areas. The soils can be slightly alkaline, well driedwith medium textured loams. Even though the tree owers andfruits throughout the year, maximum yield occurs during theperiod of March to June.

The evergreen M. zapota (sapota) is a large tree mainly culti-

2. Materials and methods

solid catalyst (KOH) in premeasured quantity of methanol. Once

R. Sathish Kumar et al. / Fu2.1. Materials and experimental setup

M. zapota (L.) seeds were collected. 99.9% pure analytical grademethanol and potassium hydroxide in pellet form of above 85%purity were used for the biodiesel production. The experimentalsetup consists of a half litre four-necked batch type spherical glassreactor, with a water-cooled condenser in one of the necks, a speedcontrolled mechanical stirrer, a temperature controlled heatingmantle and a thermometer. The arrangement of the batch typetransesterication reactor used in the study is shown in Fig. 1.

2.2. Extraction of M. zapota oil and its characterization

The collected seeds were dried in sunlight for about 24 h toremove the 10% moisture content in it. The shell was removedvated for its fruit. Its normal growth can reach up to around30 m height with the maximum diameter of trunk 1.5 m. The fruitshave a rough brownish skin with 112 seeds of color brown orblack. The seeds are covered by a juicy sweet brownish esh whichis eaten raw or made into jam and juice. The seeds are not utilizedfor any major purpose except seedling. M. zapota seeds have an oilcontent of 2330% and hence this underutilized oil seed can beconsidered for biodiesel production.

The primary objective of this investigation is to optimize thekey parameters of transesterication process of M. zapota seedoil (MZO). As MZO has not yet been studied for the biodiesel pro-duction, it is considered essential to optimize the key processparameters like molar ratio of methanol to oil, concentration ofcatalyst, temperature of reaction, and time of reaction. Further-more the properties of M. zapota seed oil and its methyl ester wereestimated and compared with EN 14214 biodiesel standards.Fig. 1. Experimental setup for the batch type transesterication process.the oil reached the required temperature, the prepared methoxidewas slowly poured into the reactor. The completion of pouringinstant was taken as the start of reaction. The condenser wasinstalled on one of the four necks to capture and reuse anyvaporized methanol. Fig. 2 shows the chemical kinetics oftransesterication process [2830]. The major inuencingparameters considered for optimization and testing in the transe-sterication process are molar ratio of methanol to oil, time ofreaction, temperature of reaction, and concentration of catalystand selected values for these parameters are shown in Table 1.

Upon reaching the predened time of reaction, the reactor wastaken out of the heating mantle and the products of the reactionwere shifted to a 500 ml separating conical funnel. After 24 h ofsettling, the heavy glycerol layer settled at the bottom of the funnelwas removed through a drainage valve. The remaining crude bio-diesel produced from MZO was gently washed with distilled waterat 40 C in order to remove the unreacted methanol, catalysts andimpurities. The percentage yield of biodiesel has been calculatedusing the formula:

Biodiesel yield % : Y grams of methyl ester producedgrams of oil used inreaction

1001manually from the dry seeds. Mechanical screw type mini expellermanufactured by M/s. Rajkumar Agro Engineers Private Limited,Pune, India, was used to extract oil from the raw dry seeds. Theapproximate oil content of the M. zapota seed lies between2530% of the weight of the seed. The oil was ltered and driedat 60 C. The various important properties of raw oil and biodieselwere estimated. Fatty acid compositions were measured using agas chromatograph (PerkinElmer Clarus 500 Auto System XL withelite series PE-5 capillary column, 30 m 0.25 mm 1 lm)coupled with a mass spectrometer (GC-MS) (Turbo; EI, 70 eV).DB-1 (100% dimethylpolysiloxane) column with helium as thecarrier gas at a ow rate of 1 ml min1.

Kinematic viscosity was measured at 40 C using a BrookeldDV-II Proviscometer as per the procedure of ASTM D 445. The pourpoint and the cloud point were simultaneously estimated inaccordance with ASTM D 5949 and ASTM D 5773 respectively.Flash point was measured using Pensky Martene open cup appara-tus. Heating value was determined with the use of Parr 6772bomb calorimeter. Density at 15 C was measured using a RudolphDDM 2909 Automatic Density Meter. The values of iodine numberand cetane number were calculated as per the standards of ASTM.The acid value was determined using a suitable titration withstandardized KOH solution with phenolphthalein as the indicator.

2.3. Transesterication process

One of the key properties of raw oil to decide about the type oftransesterication process such as one step or two step transeste-rication process is free fatty acid (FFA) content. If the FFA contentof the oil is less than 2.5%, then one step transesterication processwith a base catalyst should be used and if it exceeds 2.5%, two steptransesterication process should be the choice. In this study as theFFA content of MZO was 1.86%, single step base catalyst transeste-rication method has been adopted.

100 g (0.1) of MZO was placed in a four-necked batch reactorand heated to the required temperature. The stirrer speed wasmaintained at 500 rpm for constant mixing. The methoxide solu-tion was prepared by dissolving the exactly measured quantity of

el 140 (2015) 9096 91The step by step procedure followed in the production ofbiodiesel from M. zapota seed oil through transesterication pro-cess is shown in Fig. 3. The Manilkara Zapota Methyl Ester (MZME)

produced under optimal condition was analyzed. ASTM specica-tions were followed to determine the properties of MZME andthe estimated properties have been compared with EN14214 bio-diesel standards.

H2C

HC

O

O

H2CO

C

C

C

O

O

O

(CH2)n

(CH2)n

(CH2)n

CH3

CH3

CH3

+ 3 CH3OH

triglyceride invegetable oil

methanol

Fig. 2. Transesteric

Table 1Chosen parameters and their levels.

Parameters Levels

1 2 3

A Methanol to oil (molar ratio) 4:1 6:1 8:1B Concentration of catalyst (wt%) 0.5 1 1.5C Time of reaction (min) 60 90 120D Temperature of reaction (C) 50 60 70

92 R. Sathish Kumar et al. / Fu2.4. Design of experiments (DOE) using orthogonal array

Dr. G. Taguchi developed a newmethod to examine the effect ofdifferent parameters of a process on the mean and variance of per-formance characteristic that determines the proper functioning ofthe process. This method for design of experiments makes use oforthogonal arrays for the optimization of different parameters

Manilkara Zapota seed oil MZO

Pre-treatmentTransesterification using base catalyst

Phase separation

Crude biodiesel

Purification using distilled water

Pure biodiesel

Crude glycerol

Titration

FFA 2.5% FFA > 2.5%

Esterification using acid catalyst

KOH

Methanol

Methoxide solution

Fig. 3. Process ow chart of biodiesel production from Manilkara zapota seed oil.inuencing the process and the extent to which they can be varied.The very specialty of this method is not to investigate all the pos-sible parameters combinations but only few pairs of combinations.

This method paves way for collation of data for the determina-tion of factors which most inuence the quality of product withminimal number of experiments so as to reduce precious timeand resources. This method is very effective with nominal numberof parameters (350), few interactions between them and a veryfew contributing signicantly.

From the Orthogonal Arrays (OA), the required number ofexperiments and their conditions can be nalized. The number ofparameters and the variation levels of each parameter decide theOA selection. The least possible number of experiments N isdecided from the number of levels L and number of design andchosen control parameters P using the relation N = (L 1) P + 1.

2.5. Selection of control parameters and their levels

Among the different parameters inuencing the productionyield of biodiesel such as reaction temperature, time for reaction,type of alcohol and its quantity, type of catalyst and its concentra-tion, agitation or stirring speed, quality of the reactants and mois-ture content in the oil, only the four most inuencing parametersand three levels (L = 3, P = 4 as shown in Table 1) have beenconsidered in this study. The effects of the four chosen parametersat three different levels have been studied by conducting only nineexperiments as per L9 OA shown in Table 2. Each experiment hasbeen repeated thrice in order to minimize the errors.

2.6. Signal to noise ratio (SNR) and analysis of variance (ANOVA)

Taguchi suggested to use the loss function to calculate thedeviation between the experimental value and desired value ofperformance characteristics. The value of loss function has furtherbeen converted into a signal to noise ratio (SNR). SNRs are the logfunctions of the expected outcome which would be serving asobjective of optimization problem. Then SNR is used to calculate

H2C

HC

OH

OH

H2COH

C

O

(CH2)n CH3H3CO+ 3

glycerol methyl ester of fatty acid"biodiesel"

ation reaction.

el 140 (2015) 9096the extent of deviation of quality function from the expected value.There are three types of SNRs used in Taguchi method dependingupon the objective of the problem. Larger-the-Better (LTB) formaximization problems, Smaller-the-Better (STB) for minimizationproblem and Nominal-the-Better (NTB) for normalization prob-lems can be adopted. The SNR (dB) for NTB, STB and LTB modelscan be calculated as given below.

Nominal the best SNRi 10 log y2i

s2i

2

Smaller the better SNRi 10 logXnj1

y2jn

!3

Larger the better SNRi 10 log1nXnj1

1y2j

!4

content, suitable production process was selected. Table 3 showsthe composition and the percentage weight content of differenttypes of saturated and unsaturated fatty acids of MZO. The highestcontent of unsaturated fatty acid was found to be oleic acid(64.15%) and the next one was linoleic acid (17.92%). Palmitic acidtops the list with saturated fatty acid content. The total unsatu-rated and saturated fatty acid content of MZO was found to be83.93% and 16.07% respectively.

products of molecular weights of each fatty acid and its constituent

atalyst (wt%) Time for reaction (min) Reaction temperature (C)

1 12 23 32 33 11 23 21 32 1

l. / Fuel 140 (2015) 9096 93where

yi 1n

Xnj1

yi;j

!mean value of response 5

s2i 1

n 1Xnj1

yi;j yi !

variance 6

i is the experiment number, j is trial number and n is the number oftrials.

SNR based experimental data evaluation has been carried outfor the identication of optimal parameter combinations. As theobjective is to attain maximum yield of biodiesel, out of theavailable three different SNR quality characteristics, based on thenature of variables, Larger-the-Better (LTB) has been adopted inthe present study. Accordingly the optimal level of control ordesign parameter will be the level with the highest SNR. By usingSNR analysis, it is possible to obtain optimum level of eachparameter and optimum set of parameters producing themaximum biodiesel yield, however it is incapable of identifyingwhich factor has inuenced the output signicantly and howmucheach factor contributed to the output. This could be achieved byconducting statistical analysis of variance (ANOVA) of the responsedata. For carrying out ANOVA of response data, computation ofsum of squares is essential. The percentage of contribution wascalculated by using the following equations.

% contribution of factor SSfSST

100 7

where SSf is the sum of the squares for fth parameter and SST is thetotal sum of the squares of all parameters.

SSf X3j1

n SNRLfj SNRTh i2

8

Table 2L9 orthogonal array for DOE with four parameters at three levels (34).

Experiment no. Parameters and their levels

Methanol/oil (Molar ratio) Concentration of c

1 1 12 1 23 1 34 2 15 2 26 2 37 3 18 3 29 3 3

R. Sathish Kumar et awhere n is the number of experiments at level j of factor f

SST X9i1

SNRi SNRT2 9

A conrmation test with three trials has been carried out withthe set of optimum parameters and the statistical analysis has beenvalidated.

3. Results and discussion

3.1. Properties of the M. zapota seed oil

Crude MZO has been used for biodiesel production without anyrening process. Its physicochemical properties and fatty acidcomposition have been studied to nd the suitability as feed stockfor biodiesel production. Based on its properties and fatty acidproportion in the total fatty acids content of the oil. As the oil is atriglyceride containing three fatty acids and one glycerol, itsmolecular weight is calculated using

MW 3 AMWFA weight of glycerol backbone 10

3.2. Determination of optimal experimental condition by Taguchimethod

The percentage yield of methyl ester from raw MZO under thedesigned nine set of experiments, their SNRs and overall mean

Table 3Fatty acid composition of Manilkara zapota seed oil.

Fatty acids Content (%) Molecular weight

Palmitic acid (C16:0) 13.27 256.4Stearic acid (C18:0) 2.80 284.5Oleic acid (C18:1) 64.15 282.5Linoleic acid (C18:2) 17.92 280.5Linolenic acid (C18:3) 1.86 278.4Table 4 depicts the physicochemical properties of MZO. Themolecular weight of MZO has been calculated as 873.95 g/mol.The molecular weight of each fatty acid was rst calculated bymultiplying the number of atoms and atomic weights of constitut-ing atoms present in the molecule. The average molecular weightof all fatty acids (AMWFA) was calculated by summing up theTotal saturated 16.07%Total unsaturated 83.93%

Table 4Physicochemical properties of Manilkara zapota seed oil.

Parameters Values

Density at 15 C (g/cm3) 0.887Kinematic viscosity at 40 C (mm2/s) 34.75Free fatty acid (% FFA as oleic acid) 1.89Acid value (mg KOH/g) 3.79Iodine value (g Iodine/100 g) 65.02Peroxide value (g/kg O2) 269.54Color Brownish yellowMolecular weight (g/mol) 873.95Percentage oil content in kernel (%) 2330%Physical state at room temperature LiquidpH 3.5

SNR are tabulated in Table 5. In the present work the maximizationof biodiesel yield is set as objective, hence the larger the better(LTB) SNR model has been used. The results show that theexperiment number 5 has the highest mean yield of 93.6% and

were A (Molar ratio of methanol to oil) at level 2 (6:1), B (concen-tration of catalyst) at level 2 (1%), C (time of reaction) at level 2(90 min) and D (temperature of reaction) at level 1 (50 C).

3.3. Analysis of variance (ANOVA)

The most signicant process parameter was identied bycalculating the percentage contribution of each parameter on thebiodiesel yield. The calculated SSf and % contribution weretabulated in Table 6. From the contribution table it was observedthat concentration of catalyst was the most signicant parameterwith 67.34% contribution on the biodiesel yield from M. zapota

Table 5Percentage of yield and SNR for the 9 set of experiments.

Experiment no. A B C D % of Yield Mean yield (%) SNR

Trail 1 Trail 2 Trail 3

1 4:1 0.5 60 50 70.8 78.4 77.6 75.6 37.572 4:1 1.0 90 60 83.5 87.8 85.6 85.6 38.653 4:1 1.5 120 70 83.3 77.8 79.5 80.2 38.084 6:1 0.5 90 70 82.4 81.8 75.2 79.8 38.045 6:1 1.0 120 50 94.4 91.8 94.6 93.6 39.436 6:1 1.5 60 60 84.5 93.4 87.0 88.3 38.927 8:1 0.5 120 60 70.1 74.4 72.2 72.2 37.178 8:1 1.0 60 70 81.4 84.3 85.3 83.7 38.459 8:1 1.5 90 50 87.2 82.8 85.6 85.2 38.61

Overall mean SNRT 38.32

94 R. Sathish Kumar et al. / Fuel 140 (2015) 9096experiment 7 has the lowest mean yield of 72.2%. Though the setof parameters correspond to experiment 5 has the highest yield,this would not be the optimum set of parameters.

The level mean signal to noise ratio (SNRL), which is thealgebraic mean of all the SNRs of a particular control parameterat a specied level, has been calculated. In this experimental study,for parameter B at level 1, SNRL has been found to be 37.59 usingthe values (37.57, 38.04 and 37.17) taken from experiment Nos. 1,4 and 7 and at level 2, SNRL (38.84) corresponding to the values(38.65, 39.43 and 38.45) taken from experiment Nos. 2, 5 and 8and so on. The SNRL, DSNR (difference in maximum SNRL tominimum SNRL of particular parameter), and rank for all fourparameters have been calculated. The rank was given based onthe value of DSNR. Higher DSNR value was assigned rank 1. Basedon the rank, the concentration of catalyst has been identied as themost inuencing parameter on the yield of MZME. Molar ratio ofmethanol to oil and temperature of reaction are the second andthird inuencing factors followed by time of reaction.

The effects of each parameter at three different levels on MZMEyield in terms of SNRL are shown in Fig. 4. A higher value of SNRLinfers a greater inuence of the particular parameter at that level.The maximum value in each graph species the optimum level ofthat particular parameter on the yield of MZME. Therefore, theoptimum level of each parameter for the maximum yield of MZME

39.0Methanol : oil molar ratio321

38.5

38.0

37.5

321

39.0

38.5

38.0

37.5

Mea

n of

SN

rat

ios

Reaction time

Signal-to-noise: Larger is better

Fig. 4. SNRL of each paramseed oil followed by molar ratio of methanol to oil with 25.85%contribution. The time of reaction was the least inuencing processparameter with 1.6% contribution followed by temperature ofreaction. It shows that the major amount of biodiesel conversionhas attained close to the start of reaction. The rate of conversionis high during the start of reaction and it is not affected after itreached the steady state.

Catalyst concentration

Table 6Percentage contribution of process parameters.

Parameter SSf % Contribution

Methanol/oil (Molar ratio) 0.3269 25.85Concentration of catalyst 0.8517 67.34Time for reaction 0.0203 1.60Reaction Temperature 0.0659 5.21321

321

Reaction Temperature

eter at different levels.

anda

14

.5.90

500

0

822

Free glycerol content % (m/m) Max 0.02Total glycerol % (m/m) Max 0.25

l. / Fu3.4. Prediction of maximum yield and its validation

The prediction of theoretical maximum yield of MZME underthe optimum conditions can be calculated by using the relation.

Yo 10SNRo5 11

where SNRo is the SN ratio under optimum conditions and Yo is thetheoretical optimum yield. The predicted theoretical yield of MZMEunder optimum conditions was 95.83%.

In order to validate the percentage yield of MZME correspond tooptimal conditions predicted from this study, biodiesel MZME wasprepared through transesterication process in three trials underthe optimum level of parameters. The results were 94.50%,93.80% and 96.20% from trail 1, trail 2 and trail 3 respectively.The mean value of the three trails 94.83% closely matches with thatof theoretical estimated value and the slight variation could be dueto the inuence of extraneous variable.

3.5. Properties of Manilkara Zapota Methyl Ester

Major properties of MZME namely density, viscosity, acid value,peroxide value, heating value, pour point, ash point, iodine value,pH, and cetane number were estimated using ASTM standards andreported in Table 7. All the above mentioned properties werecompared with EN 14214 biodiesel standards. The results showTable 7Properties of Manilkara Zapota Methyl Ester (MZME) in comparison with biodiesel st

Properties Units EN 142

Ester content % (m/m) Min 96Density at 15 C g/cm3 0.860Kinematic viscosity mm2/s 3.55Acid value mg KOH/g Max 0.Iodine value g iodine/100 g Max 12Pour point C Max 0Flash point C Min 12Heating value MJ/kg Min 35Cetane number Min 51Sulphur content mg/kg Max 10Monoglyceride content % (m/m) Max 0.Diglyceride content % (m/m) Max 0.Triglyceride content % (m/m) Max 0.

R. Sathish Kumar et athat all the properties of MZME are meeting the requirements ofEN14214 biodiesel standards and hence MZME could be a potentialsubstitute to petrodiesel.

4. Conclusion

In this experimental investigation, the production, characteriza-tion and optimization of critical process parameters inuencingthe transesterication process of a new biodiesel derived fromM. zapota seed oil have been studied and reported.

Methanol with KOH as catalyst was used for the transesterica-tion process. Molar ratio of methanol to oil, concentration ofcatalyst, time of reaction and temperature of reaction were thefour inuencing parameters considered for the optimization ofbiodiesel production using Taguchi method.

The experimentally determined optimum conditions for theproduction of MZME are: 6:1 methanol to oil molar ratio, 1%(w/w) concentration of catalyst, 90 min time of reaction and50 C temperature of reaction and the corresponding yield rateis 94.83%. The concentration of catalyst and the molar ratio of methanol tooil were identied as the two most important process parame-ters inuencing bio diesel formation.

The key properties of MZME are found to meet the require-ments of EN 14214 biodiesel standards.

Hence MZME could be considered as a potential substitute tothe fossil diesel and address the global concerns of energy crisisand environmental degradation.

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96 R. Sathish Kumar et al. / Fuel 140 (2015) 9096

Optimization of biodiesel production from Manilkara zapota (L.) seed oil using Taguchi method1 Introduction2 Materials and methods2.1 Materials and experimental setup2.2 Extraction of M. zapota oil and its characterization2.3 Transesterification process2.4 Design of experiments (DOE) using orthogonal array2.5 Selection of control parameters and their levels2.6 Signal to noise ratio (SNR) and analysis of variance (ANOVA)

3 Results and discussion3.1 Properties of the M. zapota seed oil3.2 Determination of optimal experimental condition by Taguchi method3.3 Analysis of variance (ANOVA)3.4 Prediction of maximum yield and its validation3.5 Properties of Manilkara Zapota Methyl Ester

4 ConclusionReferences