COLOR QUALITY OF ROSE LIQUEUR

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1 SZU-CHUAN SHEN 1, KUO-CHAN TSENG, FENG-TING CHAO and JAMES SWI-BEA WU,3 1 Department of Medical Nutrition I-Shou University 8 Kaohsiung county, Taiwan Institute of Food Science and Technology National Taiwan University PO Box 3-14, Taipei 1067, Taiwan Accepted for Publication February 10, 07 ABSTRACT The effect of pretreatments and soaking conditions on the color quality of rose liqueur was investigated. Results show that (1) most of the anthocyanin in rose petals was dissolved within 48 h of soaking; () a longer soaking time led to a lower color quality due to browning; (3) a base spirit at lower ethanol content extracted more anthocyanin and also resulted in more browning; (4) 50C air-drying to % water content retained 90% of anthocyanins in rose petals; and (5) the soaking of dried petals in the base spirit yielded a product with less browning as compared with that of fresh petals. The process for making rose liqueur with the best color quality was found to be by soaking dried rose petals at a 1:10 ratio (rose petal : ethanol, w/w) in a base spirit containing % ethanol added with % citric acid for 4 h, then diluting the extract to 16% ethanol content. PRACTICAL APPLICATIONS This study provides an adequate process for the making of rose liqueur. Pre-dehydration treatment can be applied on the raw material in the making of various anthocyanin-containing beverages to improve the color quality. Findings in regard to the effect of ethanol concentration on anthocyanin extraction and the color stability of the product can also be valuable references to wine industry. 3 Corresponding author. TEL: ; FAX: ; jsbwu@ ntu.edu.tw Journal of Food Quality (07) 17. All Rights Reserved. 07, The Author(s) Journal compilation 07, Blackwell Publishing

2 3 INTRODUCTION Rose liqueur is becoming popular as a dessert wine. A common way of making this product is to soak fresh rose petals in clear spirit. The most important quality attributes of rose liqueur are color and aroma. Ethanol concentration influences extraction efficiency (Metivier et al. 1980) and color phenomena (Tseng et al. 06) in anthocyanin-containing liqueurs. To establish a process that effectively extracts and preserves the color is worthwhile. There are many publications pertaining to the pigment, anthocyanin, in rose flowers, mainly in its content, composition, structure, stability and color phenomenon (Asen et al. 1971; Biran and Halevy 1974; Biran et al. 1973; Dela et al. 03; Eugster and Märki-Fischer 1991; Mikanagi et al. 1995, 00; Oren-Shamir et al. 01). However, no reports on rose liqueur have been published in common scientific journals. Our objective was to investigate the effect of pretreatments, formulation and soaking conditions on the color quality of rose liqueur, and to develop an adequate process for making this product. MATERIALS AND METHODS Materials A cut flower of rose (Rosa hybrida cv. Grand Gala) was purchased from Nei-Hu floral market in Taipei City, Taiwan in March 04 within 4 h after plucking, and was transported to the laboratory in 1 h. The petals were stripped off the flower immediately after, washed and left in an ambient condition until the surface was dry. Evaluation of the Physicochemical Properties of Rose Liqueur Extraction of Rose Petal Anthocyanin. The rose petals were soaked in % (v/v) ethanol solution (Taiwan Tobacco and Liquor Corporation, Taipei, Taiwan) as the base spirit at a 1:10 ratio (w/w) at 5C for up to 10 days. Samples of the extract were taken during the soaking process, and were filtered through Whatman No. 1 filter paper (Whatman International Ltd, Maidstone, England). Titratable Acidity. Sodium hydroxide solution (Sigma, St. Louis, MO) at 0.1 N was used to titrate the filtered extract to ph 8.1. The titratable acidity was calculated as percent malic acid. The ph value of the filtered extract was measured using a commercial ph meter.

3 4 S.-C. SHEN ET AL. Total Phenol. The content of total phenolic compounds in the extract was determined according to the method reported by Amerine and Ough (1980). Distilled water was added to a 0.-mL aliquot of the filtered extract to make up the volume to.0 ml. The diluted extract was first mixed with a 1.0-mL Folin-Ciocalteu Phenol Reagent (Sigma), then with 5.0 ml of % sodium carbonate solution (Sigma). The mixture was set aside for min before its absorbance at 765 nm was taken. The standard curve was prepared using gallic acid (0 0 ppm) (Sigma). Total Anthocyanin. The total anthocyanin content was determined referring to Fuleki and Francis (1968) and Cheng and Breen (1991) with modifications. The filtered petal extract in 5-mL aliquots was diluted either with 0.-N KCl (Fluka, Buchs, Switzerland)/0.-N HCl (Merck, Darmstadt, Germany) (5:67, v/v) buffer to 100 ml and adjusted to ph 1.0 with concentrated HCl or NaOH solution (Fluka), or with 1.0-N sodium acetate (Sigma)/ 1.0-N HCl/water (10:6:9, v/v) to 50 ml and adjusted to ph 4.5. The A 5 values of these diluted solutions were taken. The total anthocyanin content (TAC; in mg/100 ml) was calculated using the following equation: TAC = ([ A F A F ] 100 V MW) 1 1 e where A 1 : A 5 of the extract buffered at ph 1.0; A : A 5 of the extract buffered at ph 4.5; F 1 : volume of the extract buffered at ph 1.0 (100 ml); F : volume of the extract buffered at ph 4.5 (50 ml); V: volume of sample before dilution (5.0 ml); MW: the molecular weight of cyaniding-3-glucoside (484 g/mol) to represent anthocyanins; and e: the molar absorbance coefficient of cyaniding- 3-glucoside ( ). Reducing Sugar. The reducing sugar content in the extract was determined using the method of Miller et al. (1959) with modifications. DNS reagent was prepared by adding 1.0 g of 3,5-dinitrosalicylic acid (Sigma) and g of potassium-sodium tartarate (Fluka) to ml of.0-n NaOH solution, then making up the volume to 100 ml with distilled water. A.0-mL aliquot of the filtered extract was added with 1.0 ml of the reagent, mixed, heated in boiling water bath for 10 min, then diluted with 5.0-mL distilled water. The absorbance at 5 nm was measured. The standard curve was prepared using % glucose solutions (Sigma). Color Measurement. The A 4 and A 5 values of the filtered petal extract were evaluated using a spectrophotometer (Model 8500; Lab Alliance, State College, PA) and were taken as indices of brown and red colors, respectively. The Hunter L, a, b values were read using a TC-1500 DX color and

4 5 color difference meter (Tokyo Denshoku, Tokyo, Japan). A standard white plate (X, Y, and Z values set at 90.85, 9.85 and 103.1, respectively) was used as the reference. The DE value ([DL +Da +Db ] 1/ ) and Hue angle (Tan -1 [b/a]) were calculated (Brewer et al. 01). Evaluation of the Effect of Petal Pre-dehydration on the Color of Rose Liqueur Fresh rose petals were air-dried at C 95% relative humidity, 50C 93% relative humidity or C 9% relative humidity, respectively, in a constant temperature drying chamber operated at 1. m/sec air flow velocity. The moisture content and total anthocyanin content in the dehydration process were evaluated. The dried petals were then soaked in % ethanol solution. The changes in total anthocyanin content and browning index (A 4 ) in the extraction process were monitored. Control samples were prepared using the fresh rose petals. Design of Experiments in Response Surface Methodology Referring to Box and Behnken (19), a three factors three levels response surface design was used for the optimization of extraction conditions. The critical factors involved were acidity (X 1 ) and ethanol concentration (X ) of the base spirit, and soaking time (X 3 ). These factors and the level at which the experiments were carried out are given in Table 1. A total of 15 runs with center points were generated. The central point of the design was citric acid, 1.0%; ethanol concentration, %; and soaking time, 4 h. The responses Y 1 (total anthocyanin content) and Y (A 4 ) of the liqueur produced in each treatment were evaluated (Table 1). The response surface analysis of the data was performed using RSREG program in Statistical Analysis System (SAS, Cary, NC), referring to the method reported by Giovanni (1983). The regression equations between variables and the total anthocyanin content or the A 4 value were composed. The response surface contours were mapped to find the optimized condition. Finally, the extract was diluted to a 16% ethanol concentration to mimic the commercial rose liqueur. The sensory evaluation was then conducted. RESULTS AND DISCUSSION Effect of Soaking Time on the Physicochemical Properties of Rose Liqueur The ph value of the liqueuer stayed between 4.3 and 4.5 in the soaking of rose petals in % ethanol (data not shown).

5 6 S.-C. SHEN ET AL. TABLE 1. PROCESS VARIABLES AND LEVELS IN THE THREE FACTORS THREE LEVELS RESPONSE SURFACE EXPERIMENT DESIGN IN ROSE LIQUEUR MAKING Runs Independent variables (coded-level) Observed value X 1 X X 3 Y 1 Y Citric acid added (wt %) Ethanol (vol %) Time (hr) Anthocyanins (mg/100 ml) A (-1) (-1) 4 (0) (1) (-1) 4 (0) (0) (-1) 36 (1) (0) (-1) 1 (-1) (-1) (0) 36 (1) (1) (0) 36 (1) (1) (0) 1 (-1) (-1) (0) 1 (-1) (0) (0) 4 (0) (0) (0) 4 (0) (0) (0) 4 (0) (-1) (1) 4 (0) (1) (1) 4 (0) (0) (1) 36 (1) (0) (1) 1 (-1) Changes in the contents of titratable acids, reducing sugars, phenolic compounds and total anthocyanin extracted from the rose petals in 8% ethanol solution are presented in Fig. 1. A soaking time of days appeared to be adequate in the making of rose liqueur. The titratable acidity and the content of phenolic compounds in the soaking process were between 0.04 and 0.06% (Fig. 1A) and between,0 and,500 ppm (Fig. 1B), respectively. The total anthocyanin content reached the highest value of 8 mg/100 ml in days, and then decreased (Fig. 1C). It indicates that most of the anthocyanin in petals is extracted in the ethanolic solution within days. The decrease in the anthocyanin content after then can be explained by the continuation of polymerization and degradation reactions of anthocyanin in the solution (Tseng et al. 06). The reducing sugar content decreased from 3.6 to 3.5 g/l in days, and then increased (Fig. 1D). The rose petal extract contained much less reducing sugar than many fruit liqueurs, e.g., the reducing sugar content in lychee liqueur is between 70 and 180 g/l (Chiang 01), indicating that Maillard browning might not play an important role in the color stability of rose liqueur before the addition of sucrose in formulation.

6 7 Titratable acidity (wt %) (A) Total phenol (ppm) (B) Time (day) Time (day) Total anthocyanin (mg/100 ml) (C) Time (day) Reducing sugar (g/l) (D) Time (day) FIG. 1. CHANGES IN THE SOAKING OF ROSE PETALS IN % ETHANOL SOLUTION AT 1:10 (W/W) RATIO AT 5C, (A) TITRATABLE ACIDITY, (B) TOTAL PHENOL, (C) TOTAL ANTHOCYANIN AND (D) REDUCING SUGAR The A 4 and A 5 values of rose petal extract are shown in Fig.. The degree of browning, as shown by A 4, increased with soaking time (Fig. A). Possible browning mechanisms include the enzymatic browning catalyzed by polyphenol oxidase and the nonenzymatic oxidative condensation of tannin compounds (Cheynier et al. 1988). There was no significant change in the intensity of red color, as shown by A 5, in the soaking process (Fig. B). Hunter s values of the extract are shown in Table. A reduction in L value (lightness) and an increase in a value (redness) of the extract were observed during the soaking process. A majority of the change was completed in the first days, in accordance with the extraction of soluble solids (Fig. 1). The b value (yellowness) increased with soaking time, reflecting the influence of browning reaction. The hue angle showed a gradual increase from 8.8 (day 0) to (day 10), indicating that the color of extract shifted from red to yellow (Table ).

7 8 S.-C. SHEN ET AL..5 (A) Abs (4 nm) Time (day) (B) Abs (5 nm) Time (day) FIG.. CHANGES IN ABSORBANCE OF THE % ETHANOL EXTRACT OF ROSE PETALS DUE TO THE SOAKING TIME, (A) A 4 AND (B) A 5

8 9 TABLE. COLOR CHANGES OF THE % ETHANOL EXTRACT OF ROSE PETALS DUE TO THE SOAKING TIME Soaking time (hr) Hunter s values DE* Hue angle** L a b * DE = (DL +Da +Db ) 1/. ** Hue angle = Tan -1 (b/a). Effect of Pre-dehydration of Petals on the Color of Rose Liqueur In the extraction process, enzymes may meet and act on substrates to catalyze various reactions that normally do not proceed to a significant extent in intact cells. Dehydration at a high temperature as a pretreatment may inactivate the anthocyanin-degrading enzyme and the browning enzymes in the petals, thus improves the color quality of rose liqueur. Meanwhile, dehydration is also an effective way to preserve rose petals as a semiproduct. However, too high a temperature itself may destruct anthocyanins. A temperature higher than 63 or C has been reported to cause the destruction of anthocyanin in strawberry (Decareau et al. 1956) or grape (El-Gindy et al. 197), respectively. Therefore, dehydration temperatures at, 50 and C were chosen for the experiments in our investigation. The moisture content and anthocyanin retention in rose petals as a result of dehydration are shown in Fig. 3. Dehydration at or 50C preserved anthocyanin satisfactorily with a loss of approximately 10% only (Fig. 3A,B). However, the C dehydration process was too slow to reduce the moisture content below % in the experiment period. Significant reduction in anthocyanin content occurred at C dehydration, amounting to more than % loss before the moisture content dropped to % (Fig. 3C). Taking all the abovementioned factors into consideration, the dehydration pretreatment condition for rose petals was chosen to be 1 h at 50C. The extraction of anthocyanins from the rose petals with and without the 50C 1 h dehydration pretreatment is shown in Fig. 4A. In earlier stage, the rate of extraction from dried petals was slower than that from fresh petals, presumably because it takes time for the solvent to flow in the shrunken cells in dried petals to dissolve anthocyanins. In the latter stage, the extract from

9 10 S.-C. SHEN ET AL. Total anthocyanin retention (%) or Moisture content (%) Total anthocyanin retention (%) or Moisture content (%) Total anthocyanin retention (%) or Moisture content (%) Moisture content Total anthocyanin retention (A) Time (hr) (B) Moisture content Total anthocyanin retention Time (hr) (C) Time (hr) Moisture content Total anthocyanin retention FIG. 3. MOISTURE CONTENT AND TOTAL ANTHOCYANIN RETENTION IN ROSE PETALS AIR-DRIED AT (A), (B) 50 AND (C) C

10 11 Total anthocyanin (mg/100 ml) (A) 0 80 Time (hr) (B) fresh rose dried rose 0.8 Abs (4 nm) fresh rose dried rose 0 80 Time (hr) FIG. 4. CHANGES IN (A) TOTAL ANTHOCYANIN AND (B) A 4 OF THE % ETHANOL EXTRACT OF ROSE PETALS dried petals showed a higher concentration of anthocyanins than that from fresh petals. This can be attributed to the dilution effect by the cell sap from fresh petals. Figure 4B shows the browning in the extracts. The extract of the dried petals was less browned than that of the fresh petals, presumably benefited from the inhibition of browning enzymes as a result of the dehydration process. Optimization of Extraction The code values obtained in the response surface experiment design are shown in Table 1. The regression equations for the prediction of anthocyanin content and browning index (A 4 ) in the liqueur are:

11 1 S.-C. SHEN ET AL. Total anthocyanins ( mg 100 ml)= X X X XX XX XX X X X 3 A4 = X1 0. X X X1X X X X X X X X where X 1, X and X 3 refer to citric acid added (wt %), ethanol concentration (vol %) and soaking time (h), respectively. The response surfaces for total anthocyanins in the extract at 1, 4 and 36 h of soaking time are shown in Fig. 5. A soaking time of 4 h was sufficient to extract most of the anthocyanins. Higher acidity was also found to favor the extraction. The response surfaces for browning index in the extract are shown in Fig. 6. Longer soaking time and lower ethanol concentration corresponded to more serious browning. The addition of citric acid at approximately 0.6% inhibited browning to some extent. Figure 7 was generated by the superposition of the response surfaces for total anthocyanin and browning index at 4-h soaking time. In sensory test (data not shown), we found that high acidity (when rose liqueur containing acidity higher than 1.0%) affected the mouth-feel of rose liqueur. Therefore, in considering high recovery of anthocyanins with low browning side effect, we recommend the optimized condition for the extraction operation in the processing of rose liqueur to be by soaking in a spirit at % ethanol concentration containing % citric acid for 4 h. CONCLUSION Drying is a good way for preserving rose petals and for inhibiting enzymatic browning in the making of rose liqueur. The ethanol concentration, titratable acidity, and soaking time in the base spirit may influence the color quality of the product. The process for the making of rose liqueur with the best color quality was found to be soaking dried rose petals at 1:10 ratio (rose petal : ethanol, w/w) in a base spirit containing % ethanol added with % citric acid for 4 h, then diluting the extract to 16% ethanol content.

12 (A) (B) (C) acid acid ethanol ethanol ethanol acid FIG. 5. THE RESPONSE SURFACE FOR TOTAL ANTHOCYANIN IN THE EXTRACT AT VARIOUS ACIDITIES AND ETHANOL CONCENTRATIONS AFTER SOAKING ROSE PETALS FOR (A) 1, (B) 4 AND (C) 36 H (TOTAL ANTHOCYANIN [mg/100 ml])

13 14 S.-C. SHEN ET AL (A) (B) (C) acid acid ethanol ethanol ethanol acid FIG. 6. THE RESPONSE SURFACE FOR A4 IN THE EXTRACT AT VARIOUS ACIDITIES AND ETHANOL CONCENTRATIONS AFTER SOAKING ROSE PETALS FOR (A) 1, (B) 4 AND (C) 36 H

14 ethanol acid FIG. 7. OVERLAP CONTOUR PLOT FOR TOTAL ANTHOCYANIN AND A 4 IN THE ROSE PETAL EXTRACT AT VARIOUS ACIDITIES AND ETHANOL CONCENTRATIONS (SOAKING TIME: 4 H) A 4, total anthocyanin (mg/100 ml). The area marked indicates the optimum condition. REFERENCES AMERINE, M.A. and OUGH, C.S Methods for Analysis of Musts and Wines p. 341.Wiley, New York, NY. ASEN, S., NORRIST, K.H. and STEWART, R.N Effect of ph and concentration of the anthocyanin-flavonol co-pigment complex on the color of Better Times roses. J. Am. Soc. Hortic. Sci. 96, BIRAN, I. and HALEVY, A.H Effect of varying light intensities and temperature treatments applied to whole plants, or locally to leaves or flower buds, on growth and pigmentation of Baccara rose. Physiol. Plant. 31, BIRAN, I., ENOCH, H.Z., ZIESLIN, N. and HALEVY, A.H The influence of light intensity temperature and carbon dioxide concentration on anthocyanin content and blueing of Baccara rose. Sci. Hortic. 1,

15 16 S.-C. SHEN ET AL. BOX, G.E.P. and BEHNKEN, D.W. 19. Some new three level designs for the study of quantitative variable. Technometrics, BREWER, M.S., ZHU, L.G., BIDNER, B., MEISINGER, D.J. and MCKEITH, F.K. 01. Measuring pork color: Effects of bloom time, muscle, ph and relationship to instrumental parameters. Meat Sci. 57, CHENG, G.W. and BREEN, P.J Activity of phenylalanine ammonialyase (PAL) and concentrations of anthocyanins and phenolics in developing strawberry fruit. J. Amer. Soc. Hortic. Sci. 116, CHEYNIER, V., OSSE, C. and RIGAUD, J Oxidation of grape juice phenolic compounds in model solutions. J. Food Sci. 53, CHIANG, H.C. 01. The changes of components and color of Lichee liqueur. MS Thesis, Graduate Institute of Food Science and Technology, National Taiwan University, Taipei, Taiwan. DECAREAU, R.V., LIVINGSTON, G.C. and FELLERS, C.R Color changes in strawberry jellies. Food Res. 10, DELA, G., OR, E., OVAADIA, R., NISSIM-LEVI, A., WEISS, D. and OREN-SHAMIR, M. 03. Changes in anthocyanin concentration and composition in Jaguar rose flowers due to transient high-temperature conditions. Plant Sci. 164, EL-GINDY, M., RAUOF, M.S. and EL-MANAWATY, H A study on the effect of processing temperature and time on the colour loss of anthocyanin pigments in grapes. Agric. Res. 50, EUGSTER, C.H. and MÄRKI-FISCHER, E The chemistry of rose pigments. Angewandte Chemie: International Edition in English, FULEKI, T. and FRANCIS, F.J Quantitative methods for anthocyanins.. Determination of total anthocyanin and degradation index for cranberry juice. J. Food Sci. 33, GIOVANNI, M Response surface methodology and product optimization. Food Technol. 37, METIVIER, R.P., FRANCIS, F.J. and CLYDESDALE, F.M Solvent extraction of anthocyanins from wine pomace. J. Food Sci. 45, MIKANAGI, Y., SAITO, N., YOKOI, M. and TATSUZAWA, F. 00. Anthocyanins in flowers of genus Rosa, sections Cinnamoneae (= Rosa), Chineses, Gallicanae and some modern garden roses. Biochem. Syst. Ecol. 8, MIKANAGI, Y., YOKOI, M., UEDA, Y. and SAITO, N Flower flavonol and anthocyanin distribution in subgenus Rosa. Biochem. Syst. Ecol. 33,

16 17 MILLER, G.L., DEAN, J. and BLUM, R A study of methods for preparing oligosaccharides from cellulose. Arch. Biochem. Biophys. 91, 1 6. OREN-SHAMIR, M., DELA, G., OVADIA, R., NISSIM-LEVI, A., PHILOSOPH-HADAS, S. and MEIR, S. 01. Differentiation between petal blueing and senescence of cut Mercedes rose flowers. J. Hortic. Sci. 76, TSENG, K.C., CHANG, H.M. and WU, J.S.B. 06. Degradation kinetics of anthocyanin in ethanolic solutions. J. Food Process Pres.,

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