Effect of Ultra-high Pressure Treatment on the Chemical Properties, Colour and Sensory Quality of Young Red Wine

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1 Effect of Ultr-high Pressure Tretment on the Chemicl Properties, Colour nd Sensory Qulity of Young Red Wine X. Sun#, X. Chen#, L. Li, T. M, F. Zho, W. Hung, J. Zhn* College of Food Science nd Nutritionl Engineering, Beijing Key Lbortory of'viticulture nd Oenology, Chin Agriculturl University, Beijing , Chin #These uthors contributed eqully to this work Submitted for publiction: June 2015 Accepted for publiction: August 2015 Key words: UHP, chemicl properties, sensory qulity, colour The effects of ultr-high pressure (UHP) tretment on the chemicl properties, colour nd sensory qulity of young red wine were studied. UP did not significntly ffect the lcohol content, nd the methnol content ws higher thn tht of the control, with the ltter first incresing nd then decresing with the increse in the pressure or period of tretment. The glycerol content ws lso mrkedly chnged by UHP, lthough without regulr pttern. The ph vlue ws not mrkedly chnged by the tretments, nd the contents of totl cids nd voltile cids were scrcely ffected. The fructose nd glucose contents were clerly chnged ccording to the different tretment conditions. The trtric cid, citric cid nd lctic cid levels showed evident chnges, wheres the mlic cid level ws not chnged by UP tretment. The trend of these chnges ws similr to wht occurs during nturl geing. As the pressure of the tretment ws incresed to 200 MP, the chrom vlue incresed, followed by decline upon higher pressure tretments. The hue of the wine ws significntly chnged by tretment t different pressures, reching the highest vlue fter tretment t 400 MP nd then decresing with incresing pressure. The chrom nd hue vlues of the wine were chnged significntly ccording to the durtion of the UP. After UP, the ppernce, rom nd tste of the wine ws improved, with the score for ppernce obviously incresed. When the wine ws treted t 500 MP for 30 min, its sensory qulity received the highest score. NTRODUCTON Ultr-high pressure (UTP) processing, lso clled highhydrosttic pressure (HHP) processing, is method by which food is seled in continers or plced in wter or other liquids under pressure to sterilise it nd inctivte enzymes, or to chnge the functionl properties of product (Chen et l., 2012; Zho et l., 2014). Becuse this tretment hs severl dvntges over the trditionl methods for food conservtion nd hygiene, U}P tretment is of gret vlue to the food-processing industry nd hs been widely pplied to rnge of different foods over the lst severl decdes. Wine is the second most populr lcoholic drink in the world (M et l., 2014; Sun et l., 2014). The U}P processing of wines hs been studied, including its use in sterilistion s substitute for the ddition of sulphur dioxide nd in ccelerting geing, mong others (Sencer, 2012). Wine is trditionlly ged in ok brrels, which is lengthy, very expensive nd risky process (Chen et l., 2012). Using dvnced technologies such s UHP tretment, high-voltge pulsed electric field tretment, electromgnetic field tretment nd microwve tretment to simulte this process would sve much time nd expense. Due to these dvntges, whole rnge of food products treted using the dvnced methods, such s fruit juices, sefood nd met products, cn be found on mrket shelves throughout the world, but no UHP-treted wine hs been introduced into the mrket (Mtser et l., 2004; Prk et l., 2007; 2009; Sencer, 2012), minly becuse the correltion studies re still not sufficiently mture. Mny reserchers hve reported on the effects of the U}P tretment of wines, focusing mostly on certin spects. Firstly, the effect of U}P tretment on the chemicl composition of functionl components, including phenolic cids, flvn-3-ols, pronthocynidins (Chen et l., 2012), nthocynins (Mort et l., 2012; Del Pozo-nsfrn et l., 2007) ndvoltile compounds (Mort etl., 2012), hvebeen studied. After U}P tretment, the concentrtion of phenolic cids ws incresed, wheres the levels of flvn-3-ols were decresed. The content nd structure of pronthocynidins ws lso chnged by this tretment, with trend tht ws *corresponding uthor: E-mil ddress: zhnjichengcu.edu. cii [Tel/Fx: ] Acknowledgements: We express our grtitude for funding from the Fundmentl Reserch Funds for the Centrl Universities in Chin (2015SP004), the Ntionl Nturl Science Foundtion Project ( ) nd the Specil FundforAgro-scientic Reserch in the Public nterest (2012BAD31B05) 393

2 Effect of UHP on Young Red Wine 394 similr to tht occurring during nturl geing (Del Pozo- nsfrn et l., 2007; Chen et l., 2012; Mort et l., 2012). Furthermore, UHP tretment voided the reduction of the voltile compound contents tht occurs when using trditionl techniques for microbiologiclly stbilising wines (Mort et l., 2012). Secondly, the effect of UHP tretment on the stbility of wines hs been studied (Corrles et l., 2008; Tbilo-Munizg et l., 2014). t ws found tht UHP tretment my contribute to protein stbilistion (Tbilo- Munizg et l., 2014) nd cuse nthocynin condenstion (Corrles et l., 2008) in wines. Thirdly, the effect of UHP tretment on psteuristion or its use s substitute for the ddition of sulphur dioxide ws studied, nd the fesibility of UHP tretment for wine psteuristion ws demonstrted (Delfini & Conterno, 1995; Mok et l., 2006; Mort et l., 2012; Sntos et l., 2013; 2013b; Mort et l., 2015). n ddition to the spects mentioned bove, the bsic physicl nd chemicl indices, sensory properties nd colour re the foundtion of wine qulity (Li et l., 2006). Whether UHP tretment ffects these indices is lso very importnt to the ppliction of UHP technology by the wine industry. However, to the best of our knowledge, few studies hve focused on the effect of UHP tretment on these indices. Therefore, the im of the present investigtion ws to nlyse the effects of different UHP tretments on the bsic physicl nd chemicl indices, sensory properties nd colour of wine. These results re expected to fcilitte the successful use of UHP technology by the wine industry s soon s possible. MATERALS AND METHODS Preprtion of wine smples The wine smples were obtined from Xinjing, Chin, from the 2009 vintge, nd the vriety ws Cbernet Suvignon. Fresh wine ws smpled directly from the fermenttion tnk, filtered nd then stored t 15 C in bottles in the drk until the experiments were conducted. All of the experiments were completed within two weeks. The first group of wine ws treted t 100 MP, 200 MP, 300 MP, 400 MP, 500 MP nd 600 MP for 30 min. The second group of wine ws treted for 5 min, 10 min, 20 min, 30 min, 45 min nd 60 min t 500 MP. Untreted wine ws used s the control group. The wine ws plced in 100 ml polyethylene terephthlte bottles for UHP processing. The UHP tretments were conducted using hydrosttic pressuristion unit (HPP- 650, Botou Kef Co. Ltd., Botou, nner Mongoli, Chin) with cpcity of 7.0 L t mbient temperture (pproximtely 25 C). This unit pressurised t 2 MP/s, nd the decompression time ws less thn 3 s. Distilled wter ws used s the pressure-trnsmitting fluid. The pressureholding tretment period in this study did not include the pressuristion nd decompression periods. Under dibtic compression, the temperture of the wter increses pproximtely 3 C for every 100 MP pressure increse t room temperture (Pehl et l., 2000; Blsubrmnim et l., 2008). When pressuristion ws ccomplished, the smple temperture quickly dropped to its initil temperture due to the het trnsfer from the smples to the stinless steel wll of the vessel (Chen & Hoover, 2003). Therefore, when the initil temperture of the treted wine ws pproximtely 25 C, due to the non-dibtic conditions nd the compressedhet trnsfer, the highest smple temperture reched (when the pressure ws 600 MP) ws fr less thn 40 C during the UHP tretments in this study. The contribution of the estimted highest smple temperture reched during UHP tretment to the tested indices ws considered negligible (Zho et l., 2014). All of the treted smples were filtered through 0.45 pm orgnic Millipore filter prior to nlysis (Merck Millipore, Billeric, MA, USA). Determintion of the physicl nd chemicl properties Fourier trnsform infrred spectroscopy (FTR) ws conducted using wine nlyser (F17-WineScn FT120, Foss Co., Ltd., Hillerød, Denmrk) to determine the physicl nd chemicl properties of the smples. This instrument could rpidly nlyse mny indices of the wine smples, including the contents of lcohol, methnol nd glycerol, the ph vlue nd the contents of totl cids, voltile cids, fructose, glucose, trtric cid, citric cid, lctic cid nd mlic cid, mong others (Sorino et l., 2007). Before nlysis, stndrds were used to clibrte the instrument. The wine smples were nlysed directly without ny further tretment. Determintion of the chrom nd hue vlues After the ph of the smples ws djusted to 3.6, the smples were filtered through 0.45 pm membrne, nd then, using deionised wter s the blnk control, the bsorbnce vlues t wvelengths of 420 nm, 520 nm nd 620 nm were mesured in triplicte using UV ultrviolet spectrophotometer (Shimdzu Co. Ltd., Kyoto, Jpn). The chrom vlue ws the sum of the bsorbnce vlues t 620 nm, 520 nm nd 420 rn-n, nd the hue vlue ws the rtio of the bsorbnce vlues t 420 nm nd 520 nm (Wyszecki & Stiles, 1982; CE, 2004). Evlution of the sensory qulity The smples treted using UHP were evluted in triplicte by six professionls skilled in blind tsting (GB/T 15038, 2006; Hn & Tong, 2009). The pnellists were trined t the Beijing Key Lbortory of Viticulture nd Oenology of the Chin Agriculturl University, nd included two mles nd five femles of ges rnging from 20 to 50 yers, ll of whom were experienced tsters nd hd previously prticipted in similr studies. The sensory evlution ws performed using the descriptive nlysis method (Winirski et l., 1996; GB/T ; Hn & Tong, 2009). Judging ws performed in professionl-stndrd room tht met the SO Norm 8589 (1988). The tste evlution tble ws slightly modified from tht of Winirski et l. (1996) nd is shown in Tble 1. Sttisticl nlysis The experimentl results were presented s the men vlues ± SE of three prllel mesurements. The sttisticl nlyses were performed using the SigmPlot 11.0 progrm nd SPSS 17.0 softwre. S. Afr. J. EnoL Vitic., VoL 36, No. 3,2015

3 395 Effect of UHP on Young Red Wine TABLE 1 Regultions for the evlution of wine No. Stndrd for evlution Appernce (10) 0-3 Dull or slightly off-colour Colour Bright with chrcteristic colour Clrity Brillint with rich colour Arom (30) Cler/mrginl expression of n off-odour Fruity rom 6-40-No chrcteristic vrietl-regionl-stylistic frgrnce or ged bouquet Fermented rom Hierrchy Tste (40) Richness Clrity & ftertste Blnce Deepness & length Totl qulity (20) Ageing potentil Typiclity Totl description Totl score (100) Mild vrietl-regionl-stylistic frgrnce or ged bouquet Stndrd presence of vrietl-regionl-stylistic frgrnce or ged bouquet Vrietl-regionl-stylistic frgrnce or ged bouquet distnce nd complex Vrietl-regionl-stylistic frgrnce or ged bouquet rich, complex, refined Acidity either too high (shrp) or too low (flt); or cid/sweetness rtio inhrmonious, excessively/moderte bitter nd stringent; or wtery or excessively lcoholic; or bsence/presence of typicl vrietl, regionl, or stylistic flvour in the mouth; or little/moderte lingering flvour in the mouth, plesnt ftertste Acidity pproprite for the wine style; or cid/sweetness blnce invigorting, smooth mouth feel; or typicl feeling of weight (substnce) in mouth; or superior expression of vrietl, regionl, or stylistic flvour chrcteristics; or prolonged flvour in the mouth (> 10 to 15 s), delicte nd fined ftertste Distinctly off-chrcter Acceptble representtion of trditionl spects of the wine type Clerly better thn the mjority of the wines of its type So nerly prefect in ll sensory qulities s to be memorble RESULTS Effects of UP tretment on the physicl nd chemicl properties of young red wine Alcohol, methnol, glycerol ndph The effects of the tretments on the lcohol, methnol nd glycerol contents nd the ph vlue of the wine re shown in Tble 2 nd Tble 3. After tretment t incresing pressure levels or durtions, the lcohol content ws decresed, but not significntly so. The methnol content of lmost ll of the U}P-tretment groups ws higher thn tht of the control, with n initil upwrd trend nd then downwrd trend s the pressure level or tretment period ws incresed. The glycerol content ws lso mrkedly chnged by the JHP tretment, lthough there ws no regulr pttern of chnge. The ph level ws not mrkedly chnged by tretment. Totl cids, voltile cids, glucose ndfructose The effects of U}P tretment on the totl cid, voltile cid, glucose nd fructose contents of the wine were investigted. The totl cid content (TC), lso known s the titrtble cidity, reflects the degree of dissocition of the totl cids nd their bility to form slts, which determines the cidity of the wine. U}P tretment (using different pressure levels or tretment periods) hd little effect on the TC, s shown in Fig. 1. The voltile cid content of wine cn reflect its hygienic condition (Li et l., 2006), nd it cn lso be seen from Fig. 1 tht the different U}P levels nd tretment period hd little effect on the voltile cid content. The min monoscchrides in grpe juice re glucose nd fructose. Both of these re fermentble sugrs, but their fermenttion pthwys re different. During wine fermenttion, yest will give priority to glucose (Li et l., 2006; Tronchoni et l., 2009); hence, the rtio of the glucose nd fructose contents will decline. At the end of fermenttion, fructose is the remining monoscchride in wine (Li et l., 2006). As seen in Fig. 1, fter tretment under different conditions, the contents of fructose nd glucose showed certin degree of fluctution, wheres the chnge in the glucose content ws more obvious. Orgnic cids Vritions in the four types of orgnic cids in the tretment groups, nmely trtric cid, citric cid, lctic cid nd mlic cid, re shown in Fig. 2. n generl, the contents of trtric cid, citric cid nd lctic cid were significntly ltered by tretment (P < 0.05), wheres the mlic cid content ws not drmticlly different from tht of the control. Specfficlly, s the pressure ws incresed, the trtric cid content first decresed nd then incresed, wheres the contents of citric cid nd lctic cid showed n overll rising trend. Secondly, fter tretment for different periods, the levels of the four orgnic cids were lso significntly chnged (P < 0.05), with the trtric cid content declining s the tretment period incresed, wheres the content of lctic cid incresed nd tht of citric cid nd mlic cid fluctuted nd chnged. Effects of LJHP tretment on the chrom nd hue vlues of the young red wine The chnges in the chrom nd hue vlues of the wine due to the processing conditions re shown in Fig. 3. After tretment with different levels ofutp, the chrom vlue of the wine ws

4 Effect of UHP on Young Red Wine 396 TABLE 2 The effects of different tretment pressures on the lcohol, methnol, nd glycerol contents nd the ph level Pressure (MP) lcohol (v/v) methnol (g/l) glycerol (g/l) ph Control ± ± 0.01 c ± 0.02 c 4.37 ± ± ± ± 0.01 b 4.34 ± ± ± 0.00 b ± 0.03 c 4.36 ± ± ± 0.01 b ± 0.00 b 4.37 ± ± ± 0.00 b ± ± ± ± 0.01 b ± 0.00 d 4.37 ± ± ± 0.01 c ± 0.00 d 4.38 ± 0.00 The different letters in the columns indicte significnt differences (Duncn's multiple rnge test, p < 0.05). The vlues re the men vlues ± SE. TABLE 3 The effects of different tretment periods on the lcohol, methnol, nd glycerol contents nd the ph level Time (mm) lcohol (v/v) methnol (g/l) glycerol (g/l) ph Control ± ±0.00 c ± 0.01 b 4.37 ± ± ± 0.01 b ± 0.01 c 4.38 ± ± ± 0.00 b ± 0.00 b 4.36 ± ± ± ± ± ± ± 0.00 b ± 0.00 b 4.35 ± ± ± ±0.00b 4.36± ± ± ± ± 0.01 The different letters in the columns indicte significnt differences (Duncn's multiple rnge test, p < 0.05). The vlues re the men vlues ± SE ȧ S S S S Totl ced -0- Volble cids : Totl ced cids Lii volw e_] (A) (B) o ioo Treting pressure (MP) Treting time (mm) b ( Fructose S Fructose -0-- Gkico Gcose ( 4 (C) : OLb (D) Treting pressure (MP) Treting time (mm) FGURE 1 Chnges in the contents of the totl cids, voltile cids, fructose nd glucose in the red wine treted using UHP. (A) Totl cid nd voltile cid contents fter tretment t different pressures; (B) Totl cid nd voltile cid contents fter tretment for different periods; (C) Fructose nd glucose contents fter tretment t different pressures; (D) Fructose nd glucose contents fter tretment for different periods; the different letters indicte significnt differences (Duncn's multiple rnge test, p < 0.05). The vlues re the men vlues ± SE. S. Afr. J. EnoL Vitic., VoL 36, No. 3,2015

5 397 Effect of UHP on Young Red Wine drmticlly chnged (P < 0.05). As the tretment pressure ws incresed, the chrom vlue ws incresed, reching the mximl level fter 200 MP of tretment, followed by decline s the pressure incresed, until it reched the lowest level fter 500 MP of tretment nd then plteued. The hue vlue of the wine fluctuted nd ws significntly chnged (P < 0.05) by tretments t different pressures, reching the highest vlue fter tretment t 400 MP nd then decresing s the pressure incresed. The chrom nd hue vlues of the wine were significntly chnged by U}P tretment for different periods. t is evident from Fig. 3 tht the hue vlue ws incresed by 5 min of tretment, but when the tretment period ws incresed to 10 min, the hue vlue dropped to the lowest level, fter which it followed n upwrd trend, reching the highest vlue t 30 min of tretment, fter which the vlue decresed s the tretment period incresed. U}P tretment incresed the chrom vlue of the wine, which reched the mximl level fter 200 MP tretment nd then followed downwrd trend with tretment t b (A) T1ric cid Citric cid -,--- L-Lctic cid ---- L-MiC cid k c 1,0 c b 20 b --- Trtric cid 0-- Citrc cid v L-Loctic cid -- L-Mlic cid b bbj bb Treting pressure (MP) Treting time (min) FGURE 2 Chnges in the contents of four orgnic cids in the red wine treted using U}P. (A) Contents fter tretment t different pressures; (B) Contents fter tretment for different periods; the different letters indicte significnt differences (Duncn's multiple rnge test, p < 0.05). The vlues re the men vlues ± SE , (A) 1,95 (B) Treting pressure (MP) 185 Treting time (min) 1, CQCth hixt , C 1, (C) Treting pressure (MP) (D) Treting time (min) FGURE 3 Chnges in the chrom nd hue vlues of the red wine treted using UHP. (A) Levels fter tretment t different pressures; (B) Levels fter tretment for different periods; the different letters indicte significnt differences (Duncn's multiple rnge test, p < 0.05). The vlues re the men vlues ± SE.

6 Effect of UHP on Young Red Wine 398 incresed pressure levels. As the tretment period ws extended, the chrom vlue first decresed nd then showed n upwrd trend. The totl vlues fluctuted but generlly incresed. Certin levels of high pressure cn promote the prticiption of nthocynin in condenstion rections, resulting in the formtion of the pigment polymers tht deepen the colour of wine nd rises its chrom nd hue vlues (Wng et l, 2012; Hung et l, 2013). However, higher level of pressure my dmge the structure of nthocynin nd other pigmented substnces, resulting in lower colour vlues. Effects of UHP tretment on the sensory qulity of young red wine The effects of the tretments on the sensory qulity of the wine were evluted by six professionl tsters, nd the results re shown in Fig. 4. Fig. 4A shows the effects of UHP tretment t different pressures on the ppernce, rom nd tste of the wine. t cn be seen from this figure tht the ppernce nd tste of the wine were improved by these U}P tretments, but the chnges re not pprent. Wheres the rom score ws not signfficntly chnged by tretment, the ppernce score ws obviously incresed, with the highest score chieved when using 100 MP. As shown in Fig. 413, s the tretment period ws prolonged, the ppernce nd tste vlues of the wine were incresed significntly, wheres the rom vlue ws not. Figure 5 shows the trends in the sensory evlution scores ccording to the pressure nd durtion of tretment. After tretment t 100 MP, the sensory score ws gretly incresed but, s the pressure ws incresed the score decresed, nd then it ws incresed to n even higher level fter tretment t 500 MP. As the tretment period ws prolonged, the sensory score showed n upwrd trend in voltility, nd reched the highest score t 30 mm. DSCUSSON After wter, ethnol is the second most bundnt compound in wine, nd it is produced minly from sugr during lcoholic fermenttion; the lcohol content is lwys represented by the volume percentge of ethnol (Li et l., 2006). During fermenttion, the solvent properties of ethnol my promote bb ppeernce (A) rom 20 s--- oppernce.2 o--- rom ro p----tve 15 _ b b 10 b (B), Treting pressure (MP) Treting time (mm) FGURE 4 Chnges in the ppernce, rom nd tste of the red wine treted using UHP. (A) Vlues fter tretment t different pressures; (B) Vlues fter tretment for different periods; the different letters indicte signfficnt differences (Duncn's multiple rnge test, p < 0.05). The vlues re the men vlues ± SE u) C, 0 H le 82 ü) 0 U " (A) (B) Treting pressure (MP) Treting time (mirl) FGURE 5 Chnges in the sensory qulity of the red wine treted using U}P. (A) Scores fter tretment t different pressures; (B) Scores fter tretment for different periods; the different letters indicte sigthficnt differences (Duncn's multiple rnge test, p < 0.05). The vlues re the men vlues ± SE. S. Afr. J. EnoL Vitic., VoL 36, No. 3,2015

7 399 Effect of UHP on Young Red Wine the dissolution of polyphenols nd romtic substnces, wheres the presence of ethnol nd cids mintins the stbility of wine (Li et l., 2006; Villmor & Ross, 2013). Ethnol cn rect with cids such s trtric cid or mlic cid to generte the corresponding ester compounds, nd cn rect with ldehydes to generte cetl derivtives, but sulphur cn prevent these rections. After the vrious U}P tretments, the lcohol content of the wine ws slightly lower, which my be becuse the JHP tretments promoted the ssocition of ethnol nd wter molecules, or esterifiction rections (Sencer, 2012). Glycerol, the third most bundnt compound in wine, is by-product of lcohol fermenttion nd gives wine smooth tste (Li et l., 2006). Under high-pressure conditions, intermoleculr distnces re shortened, which is beneficil for the ssocition of these molecules; however, the highpressure energy cn promote the esterifiction rection of lcohol molecules, which my be the reson for the chnge in the glycerol content (To et l., 2012; 2013; Zho et l., 2014). However, it is difficult to provide resonble explntion for the irregulr pttern of chnge. Orgnic cids re the importnt tste compounds in wine. Mny fctors cn ffect the types nd levels of these compounds in wine, including the grpe vriety, the production re nd the brewing nd geing processes used (Zheng et l., 2009). The orgnic cid content lso ffects the cidity of wine nd plys n importnt role in its colour (Li et l., 2006). Trtric cid, mlic cid, lctic cid, citric cid nd succinic cid re the five most importnt types of orgnic cids in wine, with lctic cid nd succinic cid being produced during fermenttion. The solubility of trtric cid is ffected by temperture, nd some trtric cid will precipitte during storge; moreover, during geing, trtric cid is esterified to generte the corresponding ester compound. During the mlolctic fermenttion step in the winemking process, the mlic cid content rpidly declines, while lctic cid is generted, mking the tste of the wine softer. During the geing process, mlic cid nd lctic cid prticipte in vriety of rections, such s enzymtic rections nd oxidtion-reduction rections (Lmiknr, 1997). Studies hve shown tht, during geing in bottles, the contents of trtric cid nd mlic cid in wine decrese nd the contents of citric cid nd lctic cid increse (Wng et l., 2013). With the incresed pressure levels nd tretment periods, the trtric cid content followed downwrd trend, wheres the contents of citric cid nd lctic cid incresed with trend similr to wht occurs during nturl geing. The degrees of chrom nd hue re importnt indices tht reflect the qulity of wine. The chrom level reflects the degree of colour depth, nd fctors such s the concentrtion of nthocynin nd the ggregtion of nthocynin nd uxiliry pigments ffect the chrom level. The min pigment compound in young wine is nthocynin. Free nthocynin monomers mke wine purple nd, during the process of wine mturtion nd storge, nthocynin nd tnnin polymerise to form new pigmented compounds (Grc-Puente et l, 2006), with the nthocynin monomers grdully being replced by oligomers nd polymers, which grdully turns the colour of the wine brick-red. During wine geing, the unstble nthocynin monomers re grdully replced by stble pigmented polymers, which increse the chrom vlue. The level of hue reflects the degree of mturity of the wine, nd the higher the vlue, the more yellow is the colour of the wine, nd vice vers. The hue of wine is closely relted to the types nd levels of polyphenols present. During the lter stge of wine fermenttion nd in the geing period, the 4-C nd 5-OH groups of nthocynin rect with cetldehyde, pyruvic cid, vinyl phenol, ctechol vinyl, 4-ethylguicol, pronthocynidin dimers or cetone, foiming pyrn ring structures nd generting pyrnonthocynin, which turns the colour of wine from purple to brick-red nd increses the hue vlue (Hn et l., 2008; 2009). U}P tretment chnged the chrom nd hue vlues of the wine, with the chrom vlue generlly decresing nd the hue vlue generlly incresing. Under U}P, the volume of the wine is compressed nd the internl moleculr-energy level is incresed, both of which could promote the formtion of pigment polymers. As result, fter tretment t 200 MP for 30 mm, the chrom nd hue vlues of the wine were significntly incresed. Moreover, U}P tretment cn force the residul oxygen in the continer into the wine, promoting the oxidistion of pigmented compounds (lnd et l., 1998), which my reduce the chrom level. Ageing is n importnt prt in the process of wine production; it is the mturtion process of wine (Li et l., 2006). n the geing process, series of slow nd complicted chnges in the physicl, chemicl nd biologicl chemistry will occur in wines, which will then be endowed with complex flvour nd more soft nd mellow tste, while the stbility will lso be improved (Li et l., 2006). Wter nd lcohol re the min components in wine, nd in the geing process the wter molecules become ssocited with the lcohol molecules to mke the tste more soft nd mellow. At the sme time vriety of complex chemicl rections tke plce, including the degrdtion of nthocynidin, the polymeristion of nthocynins nd tnnins nd the oxidtion of phenolic substnces. U}P compresses the wine volume nd chnges the distnce between the molecules nd rerrnges them, promoting ssocitions between the molecules. The energy provided by U}P could enhnce the moleculr ctivtion energy, promote the rection of esterifiction, polymeristion nd oxidtion, nd hence improve the colour, rom nd tste of wine (Sencer, 2012). This is supported by the results of the sensory qulity test, which showed tht the sensory scores for the wine undergoing 100 MP to 600 MP pressure tretments were ll incresed. The highest scores, nd thus the gretest sensory qulity of the wine, were recorded fter tretment t 500 MP for 30 min. CONCLUSONS The U}P tretment of the wine chnged the levels of some of its physicl nd chemicl prmeters, s well s its sensory qulity. The lcohol content ws decresed by U}P tretment, but not signfficntly so. The methnol content of lmost ll of the TJHP-tretment groups ws higher thn tht of the control, with trend of first incresing nd then decresing with the increse in the pressure or the tretment period. The glycerol content ws lso mrkedly chnged, lthough no regulr pttern ws observed. The ph level ws not mrkedly

8 Effect of UHP on Young Red Wine 400 chnged by the tretments. The U}P tretments (t incresed pressure levels or durtions) hd little effect on the totl cid or voltile cid contents. The fructose nd glucose contents were chnged by tretment under the different conditions, with the fructose content showing certin degree of fluctution, wheres the chnge in the glucose content ws more obvious. Moreover, the contents of trtric cid, citric cid nd lctic cid were significntly ltered by the U}P tretment (P < 0.05), wheres the chnge in the mlic cid content ws not drmtic. These re trends similr to those observed in nturl geing. As the pressure level of the tretment incresed, the chrom vlue incresed up to 200 MP, when this vlue peked, fter which incresing the pressure decresed this vlue nd it reched the lowest level fter 500 MP of tretment nd then plteued. The hue vlue of the wine ws significntly chnged (P < 0.05) by tretments t different pressures, reching the highest vlue upon tretment t 400 MP nd then decresing with incresing pressure. The chrom nd hue vlues of the wine were significntly chnged by U}P tretment for different durtions. The hue vlue ws incresed by 5 min of tretment, but when the tretment period ws incresed to 10 min, the hue vlue dropped to its lowest level, nd then followed n upwrd trend, reching the highest vlue t 30 min of tretment, fter which the vlue decresed with the incresed tretment period. A sensory evlution is n importnt supplement to instrumentl determintions becuse it is n effective method of describing the sensory qulity nd style of wine nd mking n intuitive, comprehensive judgement of its complex composition. After U}P tretment, the ppernce, rom nd tste of the wine were improved, nd the ppernce score obviously incresed. 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