The Effect of Cooking Conditions on Hydrophilic Antioxidants in Brussels Sprouts

Transcription

1 Funtionl Plnt Siene nd iotehnology 1 Glol Siene ooks The Effet of Cooking Conditions on Hydrophili ntioxidnts in russels Sprouts nn Pods dek * Dorot Sosnowsk rr nders Institute of Tehnil iohemistry, Fulty of iotehnology nd Food Sienes, Tehnil University of ód, 9-9 ód, Stefnowskiego /1, Polnd Corresponding uthor: * podsedek@p.lodz.pl STRCT Knowledge on the stility nd ntioxidnt tivity of nturl vegetle ntioxidnts ffeted y ooking onditions n help in plnning diets for enhned ntioxidnt intke. This study evlutes the effet of oiling, mirowving nd steming on ntioxidnt tivity nd ontent of oth vitmin C nd phenoli ompounds present in russels sprouts (vs. jx nd Filemon ). Steming ooking is reommended to minimise the loss of hydrophili ntioxidnts, while onventionl ooking signifintly redues the ontent of vitmin C (up to 53%) nd phenolis (up to %) in ooked russels sprouts. The losses of dietry ntioxidnts tested used derese of the free rdil svenging tivity towrds TS + nd DPPH rdils for ll the smples ooked. Keywords: TS, rssi, ooking methods, DPPH, phenoli ompounds, vitmin C revitions: TS,, -zinois(3-ethyl-enzothizoline--sulphoni id); DPPH, (1,1-diphenyl--pirylhydrzyl); FRP, Ferri Reduing ntioxidnt Power; TEC, Trolox Equivlent ntioxidnt Cpity; Trolox, -hydroxy-,5,7,-tetrmethyhromn-- roxyli id INTRODUCTION diet rih in rssi vegetles (Cruiferous fmily) is thought to e ssoited with redued risk of hroni diseses like rdiovsulr disese nd ner (Cohen et l. ; Chu et l. ; Uhl et l. ; oivin et l. 9). The enefiil dietry properties of these vegetles hve een ttriuted to their dietry ntioxidnts nd lso to the produts of the gluosinoltes hydrolysis. These ntioxidnts inlude wter-solule vitmin C nd phenoli ompounds, s well s lipid-solule toopherols nd rotenoids. mong rssi vegetles russels sprouts (rssi olere vr. gemmifer) re n espeilly rih soure of vitmin C. They lso ontin moderte levels of lipid-solule ntioxidnts (Pods dek 7). ording to numerous reports, the mount of totl phenolis in russels sprouts rnged from 37 to 331 mg/ g fresh weight (Tle 1). russels sprouts hve een lso reported to hve high ntioxidnt tivity (Co et l. 199; Honer nd Cervellti ; oivin et l. 9). Composition nd tivity of russels sprouts ntioxidnts re usully determined on rw mteril; however, from nutritionl point of view it should e onsidered tht efore onsumption this vegetle is ooked in different wys. Vrition in ooking onditions n ffet oth the sensory qulity nd hemil omposition of vegetle, s well s ntioxidnts ontent. Some studies hve indited tht in rssi vegetles sujeted to Tle 1 Literture dt for totl polyphenols ontent (mg/ g) in russels sprouts Vriety Extrtion solvent Content Referenes Zenk % ethnol 37.7 Singh et l. 7 nd 7% methnol 91. Cie lik et l. nd 7% etone 57.1 rt et l. Mzug 7% methnol 331. Sikor et l. ontent is expressed s glli id ontent is expressed s hlorogeni id nd indefinite ooking the mounts of oth vitmin C nd phenolis were redued y -% (Czrniek-Skuin ; Zhng nd Hmuzu ; Lopez-erenguer et l. 7; Pods dek 7; Sikor et l. ; Whtel-Glor et l. ). The losses of dietry ntioxidnts depend on the ooking onditions like type of ooking (onventionl, steming, mirowving, et.), ooking time nd mount of wter. The ojetive of the present work ws to study the influene of severl ooking methods on the ontent of hydrophili ntioxidnts in russels sprouts, suh s vitmin C nd phenoli ompounds nd their svenging pity towrds free rdils, s well s estimtion of the onditions tht mximise retention of these dietry ntioxidnts. MTERILS ND METHODS Chemils Chlorogeni id, glli id, -hydroxy-,5,7,-tetrmethyhromn--roxyli id (Trolox),, -zinois(3-ethylenzo-thizoline- sulphoni id) (TS), dithiothreitol, potssium persulphte nd met-phosphori id were purhsed from Sigm- ldrih (Steinheim, Germny) nd sori id ws otined from Sigm-ldrih (St. Louis, US). HPLC grde methnol, etonitrile nd formi id were purhsed from J.T. ker (Germny). ll other hemils were regent grde produts purhsed from POCh (Gliwie, Polnd). Ultr pure wter ws produed in the lortory using Simpliity TM Wter Purifition System (Millipore, Mrlorough, M, US). Plnt mterils russels sprouts smples (vs. jx nd Filemon ), field-grown in ommeril grdens ner ód (entrl region of Polnd) were hrvested in Novemer. Externl dmged leves were removed, nd edile prts of russels sprouts were ooked in one of three different wys. Eh of the ooking proedures ws repeted in triplite. Rw russels sprouts were used s referene smple. Reeived: 9 Jnury, 9. epted: 7 June, 9. Originl Reserh Pper

2 Funtionl Plnt Siene nd iotehnology (Speil Issue 1), Glol Siene ooks Cooking The ooking onditions were seleted ording to literture dt (Czrniek-Skuin ; Viñ et l. 7; Sikor et l. ) nd trditionl polish style of ooking. For onventionl ooking, fresh russels sprouts smples (5 g) were ooked in 5 or ml of oiling wter for 1 or min. Then, exessive wter ws dripped off nd the ooked vegetle ws homogenized in lender (run GmH Germny). For mirowving, 3 ml (room temperture) of wter were dded to 3 g portion of russels sprouts in glss eker nd mirowved ( W) for 1 min in onventionl mirowve oven (LG Group-Kore). The vegetle ws then drined nd homogenized. For steming, russels sprouts (5 g) were pled on try in pot, nd then overed with lid nd stemed over oiling wter for min. The ooked russels sprouts were then homogenized. Next, one prt of the homogenized smples ws used for determintion of dry mtter nd vitmin C ontents. The seond prt ws lyophilized nd ground into powder nd stored t C for further nlysis (phenoli ompounds ontent nd their svenging tivity). Dry mtter determintion Dry mtter ontent ws determined fter drying smple ( g) t 15 C to onstnt weight. Vitmin C extrtion nd nlysis The extrtion method used ws modifition of tht desried y Howrd et l. (1999). Rw nd ooked russels sprouts smples (1 g) were extrted with 1% solution of met-phosphori id (5 ml) for 15 min t room temperture nd entrifuged t 5 g for 1 min. The residue ws re-extrted with 1 ml of the extrting solution nd entrifuged. The omined superntnts were diluted to 5 ml with 1% met-phosphori id. One ml of this solution nd 1 ml of dithiothreitol (5%) were mixed nd kept in the drk for 1 h t room temperture. Then, fter dilution with met-phosphori id the smples were nlyzed using Knuer high performne liquid hromtogrph equipped with Eurospher- C-1 olumn (5 m. mm; 5 μm) fitted with the sme gurd olumn. The HPLC method ws dpted from Gliszzynsk-Swiglo nd Tyrkowsk (3). For nlysis of vitmin C the following grdient of methnol (solvent ) nd 5 mm KH PO ph. (solvent ) ws used: liner inrese of solvent from 5 to % in min nd then return to the initil onditions within the next 9 min with flow rte of 1 ml/min with UV-Vis detetor set t 5 nm. sori id ws identified y omprison with its genuine smple. Phenolis extrtion nd determintion Lyophilised rw or ooked vegetles ( g) were extrted twie with 5 ml of 7% solution of methnol for 15 min t room temperture (Vllejo et l. 3). The mixture ws then entrifuged t 5 g for 15 min, nd the resulting superntnt ws evported under redued pressure (T< C). The queous extrts were diluted to ml with wter, nd nlysed in order to quntify totl phenolis ontent nd to determine phenoli profiles. Totl phenolis were nlysed spetrophotometrilly y the Folin-Ciolteu proedure (Peri nd Pompei 1971). riefly, 1 ml of wter,.1-. ml of the smple,.5 ml of Folin-Ciolteu regent nd 5 ml of % N CO 3 were mixed nd diluted to 5 ml with wter. fter min of inution in the drk, the sorne ws mesured t 7 nm. The totl phenolis mount ws expressed s glli id equivlent in mg/ g of fresh weight. Phenoli profiles were determined using HPLC Knuer system equipped with UV-Vis detetor nd Eurospher- C-1 olumn. The inry moile phse ording to Tso nd Yng (3) onsisted of % eti id in mm sodium ette (solvent ) nd etonitrile (solvent ). The flow rte ws 1 ml/min nd totl run time ws 7 min. The system ws run with grdient progrm: -15% in 5 min, 15-3% in 15 min, 3-5% in 5 min, nd 5-% in 5 min. sed on the wvelength in whih the mximum of UV Vis sorption ws oserved, the phenolis were divided into two groups. The hydroxyenzoi id derivtives were quntified t nm nd expressed s glli id equivlents, nd hydroxyinnmi id derivtives t 3 nm s hlorogeni id equivlents. TS rdil tion svenging tivity TS + svenging tivity ws determined ording to the proedure desried y Re et l. (1999)., -zinois(3-ethyl-enzothizoline--sulphoni id) rdil tion (TS + ) ws produed y reting 7 mm TS wter solution with.5 mm potssium persulphte (finl onentrtion) followed y n inution of the mixture in the drk for 1 1 h t room temperture. Then, wter phenoli extrt ( μl) ws mixed with 1 ml of diluted TS + solution nd fter min inution t 3 C this mixture ws mesured t 73 nm. Trolox (-hydroxy-,5,7,-tetrmethyhromn--roxyli id) ws used s stndrd nd the ntioxidnt pity ws expressed s μmol of Trolox per 1 g of the vegetle fresh or ooked (TEC - Trolox Equivlent ntioxidnt Cpity). DPPH rdil svenging tivity DPPH svenging tivity ws determined using method of Kim et l. (). Wter phenoli extrt (.1 ml) ws mixed with.9 ml of μm DPPH in % queous methnol nd stored t mient temperture in the drk for 3 min. The derese in sorne of the resulting solutions ws mesured t 517 nm. Trolox ws used s stndrd nd the ntioxidnt pity ws expressed s μmol of Trolox per 1 g of the vegetle fresh or ooked (TEC - Trolox Equivlent ntioxidnt Cpity). Sttistil nlysis The nlysis of vrine ws performed on dt for differenes etween the ooking methods using the NOV (Sttisti Ver.., US), followed y the Tukey s postho test with signifine level p <.5. RESULTS ND DISCUSSION Due to the enefiil effets of vegetle ntioxidnts, there is n inresing interest in evlution of their hnges during posthrvest tretments, tehnology proessing (e.g. lnhing, freezing, nning), nd domesti ooking. russels sprouts n e ooked in vrious wys, ut most ommon re oiling, steming nd mirowving. Our previous studies hve demonstrted tht wter-solule vitmin C nd phenoli ompounds re the min dietry ntioxidnts in russels sprouts. The totl ontent of lipid-solule rotenoids nd -toopherol ws more thn one hundred-fold lower thn tht of hydrophili ntioxidnts. Moreover, the ontriution of lipophili ntioxidnts to the totl ntioxidnt pity of russels sprouts towrds TS rdil ws elow 1% (Pods dek et l. ). The effet of the ooking method on vitmin C ontent The vitmin C ontent in two vrieties of russels sprouts ( jx nd Filemon ) ooked under different onditions is shown in Tle nd Fig. 1. Vitmin C onentrtion signifintly (p <.5) deresed fter ll ooking tretments. The losses of vitmin C ontent in ooked russels sprouts were used y its therml degrdtion nd lehing into the ooking wter. The highest vitmin C retention ws found for stemed russels sprouts (the losses from 9 to 1%). In the se of onventionl ooking, the mount of wter strongly influened the ontent of vitmin C. When the wter to vegetle rtio ws :1 (v/w) nd russels sprouts were ooked for min, 5.7% ( Filemon ) nd 5.% ( jx ) of vitmin C ws retined (Fig. 1). Redution of the wter volume y hlf ( v/w) resulted in slightly higher level of vitmin C (59.% for the Filemon vriety nd.3% for the jx). On the other hnd, shortening of the ooking time from to 1 min ffeted the 9

3 Stility of dietry ntioxidnts of vegetles. Pods dek et l. Tle Effet of vrious ooking methods on the ntioxidnts ontent in two ultivrs of russels sprouts. Cooking Cooking Vegetle: jx method time wter Dry mtter Vitmin C Phenolis Dry mtter (min) (g/ml) (%) (mg/ g) (mg/ g) (%) Rw ge In oiling wter 1 1 1: d d e d In stem In mirowve Men SD, n 3; Tretments with the sme letters re not signifintly different (p <.5; Tukey s test) vitmin C vlues re expressed s sori id equivlents phenolis vlues re expressed s glli id equivlents d Filemon Vitmin C (mg/ g) d f e Phenolis (mg/ g) edile prt ooking wter lost edile prt ooking wter lost Fig. 1 Distriution of vitmin C in edile prt, ooking wter nd lost oserved for two vrieties ( = v. jx, = v. Filemon ) of russels sprouts ooked in different onditions. 1 - onventionl ooking for min, rtio vegetle: wter = 1: (w/v); - onventionl ooking for min, rtio vegetle: wter = 1: 1 (w/v); 3 - onventionl ooking for 1 min, rtio vegetle: wter = 1: 1 (w/v); - steming for min; 5 - mirowving for 1 min. Fig. Distriution of totl phenolis in edile prt, ooking wter nd lost oserved for two vrieties ( = v. jx, = v. Filemon ) of russels sprouts ooked in different onditions. 1 - onventionl ooking for min, rtio vegetle: wter = 1: (w/v); - onventionl ooking for min, rtio vegetle: wter = 1: 1 (w/v); 3 - onventionl ooking for 1 min, rtio vegetle: wter = 1: 1 (w/v); - steming for min; 5 - mirowving for 1 min. retention of vitmin C y 5.3 nd 5.9% in the Filemon nd jx vriety, respetively. The losses of vitmin C during mirowving were omprle with the results otined for the est onventionl ooking method with wter to vegetle rtio (v/w), nd the ooking time 1 min. Regrding the russels sprouts vrieties tested, retention of vitmin C in the ooked vegetle ws etter for the jx vriety. Our results re onsistent with those reported y Czrniek-Skuin (). The onventionl ooking in pot strting with oiling wter (wter to vegetle rtio ws :1 (v/w)) for -7 min, used losses of vitmin C from 35.9 to.% depending on the vegetle vriety. On the ontrry, this uthor hs oserved higher retention of vitmin C during the ooking in mirowve oven (9.3%) in omprison to our results (.-7.%). ording to Sikor et l. () the mount of vitmin C in russels sprouts prepred y the oiling for 1-15 min deresed y 7%. Viñ et l. (7) hve studied the effet of lnhing methods on vitmin C ontent in russels sprouts. The uthors found tht the lnhing in wter for 1 nd 3 min did not use hnges in sori id ontent, ut lnhing for min used % derese in mount of this vitmin. Conversely, mirowve heting for 5 min, followed y lnhing in oiling wter for min gve slight inrese in the sori id ontent. The effet of the ooking method on phenolis ontent The totl phenolis ontent in russels sprouts ooked under different onditions ws determined y Folin-Ciolteu ssy (Tle ) while the ontents of totl hydroxyenzoi nd hydroxyinnmi ids were mesured y HPLC method (Tle 3). The level of totl phenolis in unooked russels sprouts ws 133. mg/ g for Filemon nd 1.13 mg/ g for jx. These vlues were higher thn the ontents (37.7 mg/ g) otined y Singh et l. (7) nd y Cie lik et l. () 91 mg/ g, ut out.5-fold lower thn the mount estimted y Sikor et l. () Tle 1. These differenes re proly used y the use of different russels sprouts vrieties. fter ooking of russels sprouts in oiling wter nd in mirowve, the totl phenolis ontent ws signifintly (p <.5) redued (Tle ). Unlike vitmin C, the losses of phenoli ompounds ontent were used minly y their lehing into the ooking wter (Fig. ). The phenolis level in the oth vrieties tested deresed in the following order: fresh > -min stemed > 1-min mirowved > 1- min ooked in oiling wter > -min ooked in oiling wter. The higher losses (out 1%) were oserved for jx. s for vitmin C, the lower volume of ooking 99

4 Funtionl Plnt Siene nd iotehnology (Speil Issue 1), Glol Siene ooks Tle 3 Hydroxyenzoi ids nd hydroxyinnmi ids ontents (mg/g) in rw nd ooked russels sprouts. Cooking Cooking time Cge: wter jx Filemon method (min) (g/ml) Hydroxyenzoi ids Hydroxyinnmi ids Hydroxyenzoi ids Hydroxyinnmi ids Rw ge In oiling wter 1: In stem In mirowve Dt expressed s mens of two smples; Tretments with the sme letters re not signifintly different (p <.5; Tukey s test) ontent sed upon glli id s stndrd ontent sed upon hlorogeni id s stndrd wter nd shortening of the ooking time led to etter retention of the phenoli ompounds in the ooked vegetle. russels sprouts ooked in stem for min retined % of the totl phenolis present in fresh vegetle. Our results otined for onventionl ooking were similr to those previously reported y Sikor et l. (). russels sprouts oiled for 1-15 min lost % of totl polyphenols. Whtel-Glor et l. () hve exmined the effet of oiling, steming nd mirowving of rooli, uliflower, ge nd Chinese ge on totl phenolis ontent. oiling nd mirowving hd strong effet on ges nd rooli with derese of more thn % in totl phenolis, wheres, for uliflower, loss of 39% ws notied fter mirowving, % fter oiling nd n inrese y 5% ws oserved fter steming. The level of phenoli ids in the russels sprouts tested efore nd fter ooking is shown in Tle 3. Hydroxyinnmi ids ontent ws higher in rw vegetle thn tht of hydroxyenzoi ids, ut hydroxyenzoi ids generlly dominted in the ooked russels sprouts. fter ll ooking proedures, the hydroxyinnmi ids ontent ws signifintly (p <.5) redued. In the se of hydroxyenzoi ids, steming did not ffet signifintly their initil ontent of smples. The lowest redution of oth phenoli ids groups tested ws oserved in the se of onventionl ooking for 1 min in oiling wter in (v/w) rtio to weight of vegetle. To the est of our knowledge, there is no informtion on the qunttive nd qulittive phenoli profiles in russels sprouts. Heimler et l. () presented some dt regrding to the ontent of phenoli ids (.35 mg/g dry weight) nd flvonols (1.1 mg/g dry weight) in russels sprouts, ut ording to the uthors the ttriution of peks ws diffiult euse of very poor qulity of HPLC profile otined. In our study, we hve not deteted peks with mximum sorne t 3 nm t whih flvonols should e quntified (dt not shown). The effet of the ooking method on free rdils svenging tivity TS nd DPPH re ommonly used to ssess ntioxidnt tivity in vitro. Redution of the rdils used y hydrogen-donting ntioxidnt is monitored through derese in optil density t 73 nd 517 nm, respetively. The ntioxidnt tivity, whih reflets the ility of methnoli extrt to svenge the TS + rdil monotion nd DPPH rdil, is presented in Figs. 3,. The results lerly showed tht svenging tivity of russels sprouts towrds the oth syntheti, stle rdils tested signifintly (p <.5) delined during ooking nd showed similr trends for two vrieties tested (Figs. 3, ). Moreover, the tendeny oserved for TEC vlues is in good orreltion with the vlues of vitmin C nd phenoli ompounds losses (Figs. 1, ). The lrgest hnges (losses %) of the TEC vlues were oserved in the smples fter onventionl ooking for min with doule volume of the wter, nd the smllest (losses.7-1.%), in the se of steming. Previous studies hve indited the derese of the ntioxidnt tivity during the ooking of other rssi vegetles suh s rooli, Swmp ge nd kle (Ismil et l. TEC ( mol/g) TEC ( mol/g) rw de rw ; Lin nd Chng 5). Zhng nd Hmuzu () reported 5% derese of the svenging tivity of rooli towrds DPPH rdil during onventionl nd mirowve ooking. However, other studies indited tht oiling, steming, mirowving nd lnhing inresed free rdil svenging tivity of rssi vegetles. Viñ et l. (7) notied tht lnhing for 1- min gve 1-% inreses in the svenging tivity of russels sprouts s determined y the DPPH method. In the sme studies the uthors oserved -fold inrese of the ntioxidnt tivity in se of mirowve heting for 5 min, followed y lnhing in oiling wter for min. Whtel-Glor et l. () found tht steming of uliflower, rooli, ge nd hoy-sum led to n inrese in the FRP (ferri reduing ntioxidnt power) vlues from 13% to 3-fold. In their study the FRP vlues inresed lso for uliflower e d Fig. 3 Effet of different ooking methods on TS + rdil svenging pity of two vrieties ( = v. jx, = v. Filemon ) of russels sprouts methnoli extrt. 1- onventionl ooking for min, rtio vegetle: wter = 1: (w/v); - onventionl ooking for min, rtio vegetle: wter = 1: 1 (w/v); 3 - onventionl ooking for 1 min, rtio vegetle: wter = 1: 1 (w/v); steming for min; 5 - mirowving for 1 min. Dt re mens ± SD (n=3). Columns with the sme letters re not signifintly different (p <.5, Tukey s test).

5 Stility of dietry ntioxidnts of vegetles. Pods dek et l. TEC ( mol/g) TEC ( mol/g) nd rooli oiled nd mirowved for 5 nd 1 min. CONCLUSIONS Our studies hve shown tht losses of vitmin C nd phenoli ompounds in russels sprouts during ooking vry depending on the ooking tretment nd, to lesser extent, on the russels sprouts vriety. The results indite tht mirowve ooking nd oiling use losses of hydrophili ntioxidnts in russels sprouts nd their free rdil svenging tivity. Under these onditions vitmin C is destroyed, while phenoli ompounds re lrgely lehed into the ooking wter. In order to minimise the losses of vitmin C nd phenoli ompounds during ooking, russels sprouts should e ooked in the stem. REFERENCES rw d oivin D, Lmy S, Lord-Dufour S, Jkson J, eulieu E, Cote M, Moghri, rrette S, Gingrs D, eliveu R (9) ntiprolifertive nd ntioxidnt tivities of ommon vegetles: omprtive study. 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