jfpe_608 1..15

DEVELOPMENT AND OPTIMIZATION OF A DRINK UTILIZINGCITRUS (CITRUS UNSHIU) PEEL EXTRACT

JONG KOOK KIM1, MOO YEOL BAIK1, YOUNG TAE HAHM2 andBYUNG YONG KIM1,3

1Department of Food Science and BiotechnologyInstitute of Life Science and Resources

Kyung Hee UniversityYongin 446-701, Korea

2Department of BiotechnologyChung Ang University

Anseong, Korea

Received for Publication December 16, 2009Accepted for Publication May 4, 2010

ABSTRACTS

Citrus (Citrus unshiu) peel extracts were utilized to develop a drink usinga mixture design and optimization process. The contents of narirutin andhesperidin in the citrus peel extracts, as determined by high-performanceliquid chromatography, were 10.25 and 7.65 mg/g, respectively. Residual pes-ticides in the citrus peel, such as chlorobenzilate, diethofencarb, malathion,methiocarb and carbaryl, were not detected. Heavy metals, including lead(Pb) and cadmium (Cd), were determined as 16.00 and 6.55 mg/g prior towashing the citrus peels, and 5.83 and 5.83 mg/g after washing, respectively.Development of the drink with citrus peel extract was carried out usingfructo-oligosaccharide syrup and water. The interaction effects of these ingre-dients were investigated using a modified distance-based design and analyzedby linear regression models, nonlinear regression models and trace plots.Optimization of the mixture ratio was determined with statistical modelingusing 1,1-diphenyl-2-picrylhydrazyl (DPPH) radical scavenging activity, totalflavonoid content and taste tests, all of which are important target constraintsin a drink. Every constraint demonstrated a nonlinear canonical form. Theresponse trace plot revealed that DPPH radical scavenging activity, totalflavonoid content and taste tests were quite sensitive to citrus peel extractcontent in the drink. The optimal formulation of the drink was set at 1.974%citrus peel extract, 27.543% fructo-oligosaccharide syrup and 70.364% water.

3 Corresponding author. TEL: 82-31-201-2627; FAX: 82-31-202-0540; EMAIL: bykim@khu.ac.kr

Journal of Food Process Engineering •• (2011) ••–••. All Rights Reserved.© 2011 Wiley Periodicals, Inc.DOI: 10.1111/j.1745-4530.2010.00608.x

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PRACTICAL APPLICATIONS

Citrus peels extract can be utilized to functional drinks having a nar-irutin and hesperidin. Mixture design and optimization process enables us toattain the optimal mixture ratio with drink ingredients for the drink. Numeri-cal optimization process can be effectively applied in other food mixturesystems.

INTRODUCTION

About 2,700 thousand tons of fruits were produced in Korea in 2007, withcitrus accounting for 28% of produced fruits (KNSO 2007). Although themajority of citrus is consumed as fresh fruit, some citrus is earmarked forprocessed citrus products, such as fresh juice, concentrated juice, tea andvinegar (Chung et al. 2000). Although a portion of the citrus peel by-productgenerated in processing is used for animal feed, most citrus peels become awaste product. That citrus peels could lead to serious environmental contami-nation (Kim et al. 2004) necessitates the need for the efficient commercialutilization of citrus peels.

Recent studies have investigated the abundant functional materialspresent in the citrus peel, such as bioflavonoids, carotenoids, pectin, polyphe-nol, limonoid and dietary fiber (Rouseff et al. 1987; Eun et al. 1996; Garget al. 2001; Ahn et al. 2007; Lee et al. 2007) that inhibit lipid peroxide for-mation in plasma and the liver (Kim et al. 1999). Other researchers reportedthat citrus peels inhibited TPA-induced tumor promotion (Yoon and Jwa2006), increased antioxidative and antimicrobial activities (Ahn et al. 2007),and facilitated a rapid decrease in blood pressure.

Bioflavonoid content (naringin and hesperidin) and total dietary fiber inthe citrus peel were much higher than in the pulp (Eun et al. 1996), indicatingthat citrus peels can be used as a significant source of dietary fiber. Hesperidinhas a hypotensive effect (Son et al. 1992), whereas narirutin exhibits the sameantioxidant activity as butylated hydroxyanisole, which is a synthetic antioxi-dant (Kim et al. 2007).

In this study, narirutin and hesperidin content in citrus peels(Citrus unshiu) were extracted using 80% ethanol. Citrus peelextract, fructo-oligosaccharide syrup and water were mixed to develop thedrink. To determine the optimal mixture ratio for citrus peel extract in thedrink, 1,1-diphenyl-2-picrylhydrazyl (DPPH) radical scavenging activityanalysis, total flavonoid counts and taste tests of the mixture wereperformed.

2 J.K. KIM ET AL.

MATERIALS AND METHODS

Plant Material

Citrus fruits (Citrus unshiu) harvested from Jeju Island in Korea werepurchased in a local supermarket. The citrus fruits were peeled, the peels werewashed with distilled water three times and the peels were then dried in afreeze dryer. Dried peels were ground into a fine powder in a mixer and storedat -20C until use.

Extraction of Flavonoids from Citrus Peel

Extraction was carried out according to methods described by Kim andLee (2002a). Five grams of ground-up freeze-dried peels were mixed with100 mL of 80% aqueous ethanol and the mixture was homogenized with anUltra-Turrax T25 (IKA Labortechnik, Staufen, Germany) for 2 min at15,000 rpm. Following homogenization, the samples were filled with nitrogengas, immersed into the microprocessor-controlled bench-top ultrasonic cleaner(e-Science, Seoul, Korea) and sonicated for 20 min at room temperature. Theextracts were vacuum filtered through Whatman no. 2 filter paper (WhatmanInternational Ltd., Maidstone, England). Then, the residue with 100 mL of80% aqueous ethanol was re-extracted by repeating the method just described.Ethanol from the filtrates was evaporated in a rotary evaporator (N-1000,Eyela, Tokyo, Japan) under vacuum at 40C until the extract volume wasreduced to 10–30 mL. The concentrate was resolubilized to 100 mL with theaddition of 50% aqueous ethanol. This solution was filtered through a nylon 66syringe filter (13 mm, 0.2 mm, Whatman International Ltd., Maidstone,England) and the filtrate was used to conduct narirutin and hesperidin analysiswith high-performance liquid chromatography (HPLC).

Quantitative Analysis of Flavonoids

The quantitative analysis of flavonoids in citrus peels using HPLC wasconducted with methods described by Kim and Lee (2002b). HPLC analysisconditions for flavonoids are demonstrated in Table 1. Narirutin and hesperi-din standards were purchased from Extrasynthese (Lyon, France) and Fluka(Madrid, Spain), respectively.

Analysis of Residual Pesticides and Heavy Metals in Citrus Peels

Chlorobenzilate, diethofencarb, malathion, methiocarb and carbaryl wereselected for residual pesticide analysis in citrus peels (Liu et al. 2006). Chlo-robenzilate was determined by GC/ECD (Agilent, Santa Clara, CA), whereasdiethofencarb, malathion and methiocarb were determined by GC/NPD

OPTIMIZATION OF A CITRUS PEEL EXTRACT DRINK 3

(Agilent). On the other hand, carbaryl was determined by LC/UV (Agilent)and LC/FLD (Young Lin Instrument Co., Seoul, Korea). Analytical conditionsof the residual pesticides are demonstrated in Tables 2 and 3.

Cadmium and lead were selected to analyze heavy metals in the citruspeels. Citrus peels were washed with distilled water, freeze-dried and groundinto a fine powder. A control was developed using the same treatments withouta wash. Heavy metals in the samples were determined using the DirectReading Echelle ICP (Leeman Laboratories Inc., Hudson, NH).

Processing for Functional Drinks

To make a drink using citrus peel extracts, the previously mentionedextraction method was used for the flavonoids. A sample (5 g per 100 mL ofwater) was homogenized at 15,000 rpm for 10 min and sonicated for 20 min.

TABLE 1.ANALYTICAL CONDITIONS FOR FLAVONOIDS IN

HIGH-PERFORMANCE LIQUID CHROMATOGRAPHY

Instrument SPD-M20AColumn Symmetry C18 5 mm, 4.6 ¥ 250 mmColumn temperature 23CDetector D2 & W, 280 nmFlow rate 1 mL/minInjection volume 20 mLMobile phase Acetonitrile Water

TABLE 2.ANALYTICAL CONDITIONS FOR RESIDUAL PESTICIDES

BY GC-ECD AND GC-NPD

GC-ECD Column DB-5 (30 m ¥ 250 mm ¥ 0.25 mm)Oven 80C (2 min)-10C/min-280C (8 min)Flow rate 1.0 mL/minInlet temperature 260CDet. temperature 300CInjection volume 1 mL

GC-NPD Column DB-5 (30 m ¥ 250 mm ¥ 0.25 mm)Oven 80C (2 min)-10C/min-280C (8 min)Flow rate 1.0 mL/minInlet temperature 260CDet. temperature 300CInjection volume 1 mL

GC-ECD, Gas Chromatography Electron Capture Detector;GC-NPD, Gas Chromatography Nitrogen Phosphorus Detector.

4 J.K. KIM ET AL.

The sample was then centrifuged at 3,100 rpm for 1 h. The supernatant wasvacuum filtered through Whatman No. 2 filter paper (Whatman InternationalLtd., Maidstone, England). Remaining residue and water were re-extractedusing the same method. The filtrates were freeze-dried and ground into a finepowder. The powder was then used to develop the drinks.

The drinks were mixed with different ratios of citrus peel extract powder,fructo-oligosaccharide (CJ Cheiljedang Co., Seoul, Korea), water, a fixed ratioof vitamin C (MSC Co., Seoul, Korea), monohydrate citric acid (MSC Co.)and citrus flavoring (Cosis Co., Seoul, Korea). Concentrations of citrus peelextract powder, fructo-oligosaccharide and water ranged from 0.5–2.0, 10.0–30.0 and 67.7–89.2% (w/w), respectively. Concentrations of vitamin C, mono-hydrate citric acid and citrus flavoring were fixed at 0.05, 0.1 and 0.15% (w/w),respectively.

Determination of DPPH Radical Scavenging Activity for the Drinks

DPPH radical scavenging activity for the drinks was determined using amodified method of that described in Kim et al. 2002. Approximately 7.9 mgof DPPH was dissolved in 80% aqueous methanol. Fifty microliters of thedrink was added to 2.95 mL of methanolic DPPH solution. The mixture wasshaken vigorously and then left in the dark for 30 min at 23C. Decreases in theabsorbance of the resulting solution were monitored at 517 nm at 30 min. Acontrol was developed by mixing 50 mL of distilled water and 2.95 mL ofDPPH solution. The DPPH radical scavenging activity of the drinks were

TABLE 3.ANALYTICAL CONDITIONS FOR RESIDUAL PESTICIDES WITH LC-UV AND LC-FLD

LC-UV Column Capcell pak C18 (Shiseido), 4.6 mm ¥ 250 mm, 5 mmColumn temperature 40CDetector UV 254 nmFlow rate 0.7 mL/minInject volume 20 mLMobile phase Acetonitrile Water

LC-FLD Column Capcell pak C18 (Shiseido), 4.6 mm ¥ 250 mm, 5 umColumn temperature 40CDetector Exciting: 340 nm, Emission 455 nm, Gain 10 nmFlow rate 0.7 mL /minInjection volume 20 uLReagent 1 Hydrolysis reagent (0.05 M sodium hydroxide) 100C, 0.3 mL/minReagent 2 O-Phthalaldehyde (0.05 M sodium borate buffer) 100C,

0.3 mL/minMobile phase Methanol Water

LC-UV, Liquid Chromatography-Absorbance Detector; LC-FLD, Liquid Chromatography-Florescence Detector.

OPTIMIZATION OF A CITRUS PEEL EXTRACT DRINK 5

expressed as mg (vitamin C equivalent)/L (drink with citrus peel extracts). Thefresh radical stock solution was prepared daily.

Determination of Total Flavonoid Content of Drinks

Total flavonoid content was measured using spectrophotometry (Chunet al. 2005). The drink mixture (0.5 mL) was added to a 5 mL volumetric flaskfilled with 3.2 mL double distilled H2O. Five minutes after the start time,0.15 mL of 5% NaNO2 was added to the flask, followed by 0.15 mL of 10%AlCl3. After 6 min, 1 mL of 1 M NaOH was mixed into the solution. Duringthe reaction, a flavonoid–aluminum complex developed in the form of apink-colored compound. Absorbance of the mixture was measured at 510 nm.Total flavonoid content of the samples was expressed as mg (catechinequivalent)/L (drink with citrus peel extract). Samples were analyzed intriplicate.

Drink Taste (Preference) Test

Thirteen trained panelists participated in a taste test. Drink preferencewas determined using 9-point scale method.

Experimental Design and Modeling

Data analysis was carried out using Design-Expert 7 (Stat-Ease Co.;Minneapolis, MN). A mixture design was applied in determining high and lowratio contents of ingredients. DPPH radical scavenging activity, total flavonoidcontent and preference were selected as target points. The effects of ingredientinteractions on drinks are demonstrated on a trace plot. The optimal mixtureratio was selected via numerical optimization of the canonical model. Numeri-cal optimization was carried out by determining a goal for each responseaccording to a canonical model, and calculated using the following equation(Derringer and Suich 1980):

D d d d n n= × × ×( ) = { }. . . n di1 1Π

where D, overall desirability; d, desirability; and n, number of responses.

RESULTS AND DISCUSSION

Flavonoid Content

The flavonoid content of the citrus peels was determined using HPLC.These content values are detailed in Table 4. Flavonoids expressed in large

6 J.K. KIM ET AL.

quantity in the citrus peels were narirutin and hesperidin, with contents of10.25 and 7.65 mg/g, respectively. As demonstrated by Kim et al. 2004, nar-irutin content was higher than hesperidin in citrus.

Residual Pesticides and Heavy Metals

To ensure the citrus peel extract drink was safe, the presence of residualpesticides, including chlorobenzailate, diethofencarb, malathion, methiocarb,carbaryl and heavy metals (lead and cadmium) was determined (Table 5). Forthe most part, residual pesticides were not detected in both washed andunwashed citrus peels.

The contents of heavy metals in citrus peels are outlined in Fig. 1. Whilethe lead content in washed and unwashed citrus peels was 5.83 and 16.00 mg/g,respectively, the cadmium content was 5.83 and 6.55 mg/g, respectively.Washing citrus peels with distilled water decreases their heavy metal content.Generally, less than 0.3 mg/kg lead and 0.1 mg/kg cadmium is considered apermissible amount in fruit juice (KFDA 2008). Compared with the heavymetal content of washed citrus peels, adding up to 17.152 g of citrus peels to1 kg of drink is considered permissible. In this study, the largest amount ofcitrus peel extract powder was 20 g/kg. This content was not representative ofthe citrus peel content itself, but of the powder extract that was obtained withdistilled water and then freeze-dried. In fact, the citrus peel content wassignificantly higher than 17.152 g when obtaining 20 g/kg of extractedpowder.

TABLE 4.COMPOSITION OF FLAVONOIDS IN THE CITRUS PEEL

Flavonoids Contents (mg/g)

Narirutin 10.25 � 0.05*Hesperidin 7.65 � 1.33

* Values are mean � standard deviation, n = 3.

TABLE 5.COMPOSITION OF RESIDUAL PESTICIDES IN THE CITRUS PEEL

Residual pesticides Nonwashed citrus peel Washed citrus peel

Chlorobenzilate Not detected Not detectedDiethofencarb Not detected Not detectedMalathion Not detected Not detectedMethiocarb Not detected Not detectedCarbaryl Not detected Not detected

OPTIMIZATION OF A CITRUS PEEL EXTRACT DRINK 7

In this study, residual pesticides were not detected in the citrus peels andheavy metals were observed in acceptable amounts. Therefore, residual pesti-cides and heavy metals were negligible factors in citrus peel drink processing.

Design Point Selection for a Drink Combination

The mixture ratios of the citrus peel extract, fructo-oligosaccharide syrupand water were 0.5–2.0%, 10.0–30.3% and 67.7–89.2% (w/w), respectively.Total content of these ingredients was 99.7% (w/w). To determine a designpoint for the mixture, the range was applied to a modified distance design.From 16 design points, six experiment points, five experiment points to cal-culate the lack of fit and five replication points were set up. All design pointsand response data are expressed in Table 6. To remove division error involvingthe order that was built into the experimental design, all experiment orderswere performed at random (Han et al. 2002). Drinks made with all ingredientsdemonstrated DPPH radical scavenging activity ranging from 24.263 to80.754 mg/L, total flavonoid content ranging from 19.750 to 85.167 mg/L andpreferences ranging from 1.615 to 7.000, depending on the mixture ratio.

Modeling and Analysis for the Each Response

Analysis of selected models and regression of polynomial equations forthree responses are demonstrated in Table 7. Significance was determinedusing the F-test for the model. Interaction effects based on component changeswere determined using the trace plot (Figs. 2–4). DPPH radical scavenging

CdPb

µg/g

0

5

10

15

20

25

Non-washedWashed

FIG. 1. COMPOSITION OF HEAVY METALS IN WASHED AND UNWASHED CITRUS PEEL

8 J.K. KIM ET AL.

activity, total flavonoid content and preferences were input into a quadraticmodel, which is a nonlinear regression model (P < 0.05). Comparing the purityand surplus error, the lack of fit test demonstrated that the probability values ofDPPH radical scavenging activity, total flavonoid content and preferences

TABLE 6.QUALITY CHARACTERISTICS OF CITRUS PEEL DRINK MADE WITH CITRUS PEEL

EXTRACTS, FRUCTO-OLIGOSACCHARIDE SYRUP (FOS) AND WATER ACCORDING TOMODIFIED DISTANCE DESIGN

Standard Run Factor Response

Citrus peelextract (%)

FOS(%)

Water(%)

DPPH radicalscavengingactivity (mg/L)

Totalflavonoids(mg/L)

Preference

11 1 1.250 10.000 88.450 54.526 53.333 3.0003 2 0.500 20.000 79.200 24.263 20.583 6.0778 3 1.250 15.000 83.450 61.719 53.333 4.3014 4 1.250 30.000 68.450 58.474 55.250 4.2319 5 2.000 20.000 77.700 77.509 84.667 2.6921 6 2.000 30.000 67.700 77.246 84.333 2.846

10 7 1.250 20.000 78.450 52.684 54.167 4.07712 8 2.000 20.000 77.700 73.737 84.500 2.769

6 9 2.000 10.000 87.700 77.947 83.417 1.92316 10 0.500 30.000 69.200 26.105 20.750 6.692

2 11 0.500 30.000 69.200 25.754 21.000 7.0005 12 0.500 10.000 89.200 26.456 19.750 1.6927 13 0.875 25.000 73.825 40.667 36.917 6.000

14 14 2.000 10.000 87.700 73.561 84.25 1.61513 15 0.500 10.000 89.200 26.368 19.833 2.61515 16 2.000 30.000 67.700 80.754 85.167 4.385

DPPH, 1,1-diphenyl-2-picrylhydrazyl.

TABLE 7.ANALYSIS OF SELECTED MODELS AND REGRESSION OF POLYNOMIAL EQUATIONS

FOR THE THREE RESPONSES

Response Model Prob > F Prob > F(lack offit tests)

Equation in terms of pseudo component

DPPH radicalscavenging activity

Quadratic 0.0270 0.2010 -3627.15A + 26.11B + 26.4C +4741.12AB + 4688.74AC - 7.56BC

Total flavonoidcontent

Quadratic 0.0021 0.1869 -258.58A + 20.99B + 19.74C +1286.24AB + 1287.18AC - 0.053BC

Preference Quadratic 0.0419 0.2114 -190.57A + 6.91B + 2.56C +154.38AB + 195.41AC + 3.33BC

DPPH, 1,1-diphenyl-2-picrylhydrazyl.

OPTIMIZATION OF A CITRUS PEEL EXTRACT DRINK 9

were 0.2010, 0.1869 and 0.2114, respectively. As a result, the fitness of eachmodel was determined (Table 7). In particular, coefficients obtained for pre-dicted canonical equations demonstrated each ingredient’s response in anumerical format.

Model Analysis Using the Trace Plot

Trace plots represent the effects of DPPH radical scavenging activity,total flavonoid content and preference on each component (Figs. 2–4). Theslope, as shown in the trace plot, represents their influence on each response.

The trace plot of DPPH radical scavenging activity demonstratesincreases in DPPH as the citrus peel extract powder (A–A) increased. Whenthe quantity of fructo-oligosaccharide (B–B) and water (C–C) in the drinkmixture increased, DPPH radical scavenging activity decreased. Total fla-vonoid content experienced trends similar to DPPH radical scavenging activ-ity. This occurred because narirutin, one of the flavonoids in the citrus peels,has antioxidant properties (Kim et al. 2007). Looking at the slope of the traceplot, the citrus peel extract powder had a significant effect on DPPH radicalscavenging activity and total flavonoid content.

FIG. 2. TRACE PLOT DESCRIBING THE EFFECT OF CITRUS PEEL EXTRACT,FRUCTO-OLIGOSACCHARIDE SYRUP AND WATER ON

1,1-DIPHENYL-2-PICRYLHYDRAZYL (DPPH) RADICAL SCAVENGING ACTIVITYA–A: Citrus peel extract. B–B: Fructo-oligosaccharide syrup. C–C: Water.

10 J.K. KIM ET AL.

The trace plot analyzing preferences demonstrated that panelists pre-ferred drinks with increased fructo-oligosaccharide content (B–B). Drink pref-erence was shown to decrease with increased citrus peel extract powdercontent (A–A). It is suggested that preference decreases because flavonoids incitrus peels have a bitter taste (Benavente-Garcia et al. 1997). This bitternessmay be compensated with fructo-oligosaccharide syrup. Such a finding sup-ports an increased preference based on increases in fructo-oligosaccharidesyrup.

Optimization of Drink Mixture Ratio

Using the methods outlined in Derringer and Suich, optimal mixtureratios were determined for the drinks (Derringer and Suich 1980). The optimalmixture ratio for drinks with citrus peel extract powder, fructo-oligosaccharideand water was determined using the numerical optimization of a canonicalmodel. To determine an optimal design point, the mixture ranges for allconstraints were determined according to maximum response. The optimalmixture of citrus peel extract powder, fructo-oligosaccharide and water was1.794, 27.543 and 70.364%, respectively. Predicted response values according

FIG. 3. TRACE PLOT DESCRIBING THE EFFECT OF CITRUS PEEL EXTRACT,FRUCTO-OLIGOSACCHARIDE SYRUP AND WATER ON TOTAL FLAVONOID CONTENT

A–A: Citrus peel extract. B–B: Fructo-oligosaccharide syrup. C–C: Water.

OPTIMIZATION OF A CITRUS PEEL EXTRACT DRINK 11

to this mixture ratio indicate DPPH radical scavenging activity, total flavonoidcontent and preference to be 73.2777 mg/L, 76.7441 mg/L and 3.8611(Table 8). The desirability of this optimal point was 0.681.

In a previous study, drinks with Houttuynia cordata were enhanced withsweet, savory and fishy sensory properties. Using response surface methodol-ogy, the physical and chemical characteristics of the developed drink wereevaluated (Seung et al. 2008). In a study focused on developing a drink with

FIG. 4. TRACE PLOT DESCRIBING THE EFFECT OF CITRUS PEEL EXTRACT,FRUCTO-OLIGOSACCHARIDE SYRUP AND WATER ON TASTE TESTS (PREFERENCE)

A–A: Citrus peel extract. B–B: Fructo-oligosaccharide syrup. C–C: Water.

TABLE 8.OPTIMAL CONSTRAINT VALUES USING NUMERICAL OPTIMIZATION METHOD

Constraints name Goal Numerical optimization solution

Citrus peel extracts In range 1.794%Fructo-oligosaccharide syrup In range 27.543%Water In range 70.364%DPPH radical scavenging activity Maximize 73.2777 mg/LTotal flavonoid content Maximize 76.7441 mg/LTaste test (preference) Maximize 3.86111

DPPH, 1,1-diphenyl-2-picrylhydrazyl.

12 J.K. KIM ET AL.

Grifola frondosa water extract, oligosaccharide and green tea extract (Lee andLee 2007) as well as a study focused on Hericium erinaceum (Kwon et al.2003), the optimum mixture ratio was determined solely by sensory evalua-tion, without the use of mathematical calculations. To determine the optimaldrink ratio in a drink that is not only preferred, but also healthy, a mixturedesign and optimization process using mathematical modeling is essential.

CONCLUSION

To implement the effective utilization of citrus peels, which are aby-product of citrus juice processing, a mixture design and optimizationprocess was successfully developed to determine the optimal mixture ratio fora drink with citrus peel extract powder. Narirutin and hesperidin content incitrus peels was 10.25 and 7.65 mg/g, respectively. Residual pesticides werenot detected in the citrus peels and heavy metals, lead and cadmium, weredetected at safe levels. The drink was composed of citrus peel extract powder,fructo-oligosaccharide and water. The optimization of the processed drinkbased on the most effective mixture ratio was established through statisticalmodeling and analysis. DPPH radical scavenging, total flavonoid content andpreference, all considered important factors in drink development, influencedthe interaction effect of the each ingredient with the canonical model and traceplot. To determine the optimal mixture ratio of drink ingredients, numericaloptimization was performed using the coefficients from the canonical model.A desirability value of 0.681 was obtained whereas the optimal mixture ratiosof citrus peel extract powder, fructo-oligosaccharide and water were 1.79427.543 and 70.364%. Response values were also predicted according to theoptimal point. Optimal points for DPPH radical scavenging activity, totalflavonoid content and preference were 73.2777 mg/L, 76.7441 mg/L and3.8611.

ACKNOWLEDGMENTS

This study was supported by the OTTOGI Corporation and Kyung HeeUniversity.

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