Effect of Rice Bran Protein Extract on Enzymatic Browning Inhibition in Vegetable and Fruit Puree

Transcription

1 Ksetsrt J. (Nt. Sci.) 48 : (214) Effect of Rice Brn Protein Extrct on Enzymtic Browning Inhiition in Vegetle nd Fruit Puree Suptch Kuglomsong nd Chockchi Theerkulkit* ABSTRACT The effect of rice rn protein extrct (RBPE) on enzymtic rowning inhiition in vegetle nd fruit puree ws investigted. Protein from deftted rice rn ws prepred y lkline extrction nd isoelectric point precipittion. RBPE ws prepred y dispersing rice rn protein precipitte in distilled wter (DW) t.8% protein (weight per volume). Potto, nn or pple ws lended with RBPE nd their color vlues (L*, * nd *) were mesured. Polyphenol oxidse (PPO) inhiition ws studied y mesuring sornce t 42 nm with ctechol s the sustrte. It ws found tht the rowning vlues in potto, nn nd pple puree treted with RBPE were lower thn those treted with DW (P.5). The L* vlues nd hue ngles in potto, nn nd pple puree treted with RBPE were higher thn those treted with DW (P.5). RBPE showed the highest percentge rowning inhiition in potto puree, followed y pple nd nn puree, respectively (P.5). Moreover, RBPE hd higher percentge of PPO inhiition in potto thn pple nd nn, respectively (P.5). Therefore, RBPE could inhiit enzymtic rowning in vegetle nd fruit puree, especilly potto puree. Keywords: enzymtic rowning, rice rn protein, potto, nn, pple INTRODUCTION Enzymtic rowning hs mjor impct on the qulity of mny fruit nd vegetles. It might lso produce undesirle chnges in flvor, texture nd nutritionl vlues of the product during hndling, processing nd storge, resulting in shorter shelf life nd reduced mrket vlue (Fu et l., 25). Enzymtic rowning is minly cused y polyphenol oxidse (PPO; EC ) tht ctlyzes the hydroxyltion of monophenols to o-diphenols nd the oxidtion of o-diphenols to o-quinones in the presence of oxygen. These o-quinones re very rective compounds which self-polymerize or interct with other molecules in foodstuffs, leding to high moleculr weight drk pigments commonly clled melnins (Cntos et l., 22; Girelli et l., 24). There re severl methods to inhiit enzymtic rowning such s pplying cheltors, reducing gents nd cidulnts (But nd Moline, 21; Zhu et l., 27); however, there is n incresing consumer demnd for sustituting synthetic compounds with nturl sustnces (Jng et l., 22). Therefore, nturl ntirowning gents hve een widely investigted. Rice is one of the importnt stple foods for the world s popultion with glol rice production in 212 of out 69 million t (Interntionl Rice Reserch Institute, 213). This huge mount of production results in commensurtely lrge mounts of rice yproducts Deprtment of Food Science nd Technology, Fculty of Agro-Industry, Ksetsrt University, Bngkok 19, Thilnd. * Corresponding uthor, e-mil: fgicct@ku.c.th Received dte : 27/5/13 Accepted dte : 11/12/13

2 26 Ksetsrt J. (Nt. Sci.) 48(2) (Sereewtthnwut et l., 28). Rice rn is the mjor yproduct generted mounting to out 5 8% of the rice grin during the milling process (Julino, 1985). It is source of protein, minerls, unsturted ft, vitmins nd dietry fier (Adul- Hmid nd Lun, 2). Due to its high content of hypollergenic protein (Helm nd Burks, 1996), rice rn hs high potentil to e used s n ingredient in food pplictions. There hve een severl studies on the inhiition of enzymtic rowning in fruit nd vegetles using proteins, peptides nd mino cids such s the proteins, protein hydrolystes nd mino cids from milk (Khn, 1985), peptide from honey (Oszminski nd Lee,199; Ates, 21), hen egg white lysozyme (Li et l., 26), whet rn protein (Cmps-Ríos et l., 212; Ortíz- Estrd et l., 212), sericin (Kto et l., 1998; Thongsook nd Tiyoonchi, 211) nd peptides from onion (Gnngui et l., 21). From previous study, rice rn wter extrct hs een reported s n enzymtic rowning inhiitor (Kewk et l., 29; Theerkulkit nd Boonsiripipht, 29; Sukhonthr nd Theerkulkit, 212); however, no dequte informtion hs een pulished to dte on the effect of rice rn protein on enzymtic rowning in fruit nd vegetles. Therefore, the ojective of this reserch ws to study the effect of rice rn protein extrct on enzymtic rowning inhiition in vegetle nd fruit puree. MATERIALS AND METHODS Mterils nd chemicls Potto (Solnum tuerosum L.), nn (Mus (AAA Group) Gros Michel ) nd pple (Mlus pumil cv. Fuji) were purchsed from locl mrket in Bngkok, Thilnd. Full-ftted rice rn from the romtic rice (Oryz stiv L. cv. Kho Dwk Mli 15) ws otined from Ptum Rice Mill nd Grnry Pulic Co. Ltd., Pthum Thni, Thilnd. Polyvinylpyrrolidone nd ctechol were purchsed from Sigm Chemicl (St Louis, MO, USA). Triton X-1 ws purchsed from Fluk Chemik (Buchs, Switzerlnd). The other chemicls were nlyticl grde. Preprtion of deftted rice rn Full-ftted rice rn ws sieved through 5-mesh screen nd extrcted twice with hexne t rtio of rice rn to hexne of 1:3 (weight per volume; w/v) for 3 min nd centrifuged t 4, g t 25 ºC for 3 min. The deftted rice rn ws ir-dried overnight under fume hood, ground nd sieved through 5-mesh screen nd stored in luminum foil gs t -2 ºC until used ( modified method of Wng et l., 1999). Preprtion of rice rn protein extrct Rice rn protein ws extrcted y dispersing deftted rice rn in distilled wter (DW) t rtio of rice rn to DW of 1:4 (w/v). The ph of the slurry ws djusted nd mintined t 9.5 with 1. N NOH during stirring with n overhed stirrer t 5 rpm t room temperture for 45 min, then centrifuged t 15,2 g t 25 ºC for 3 min. The superntnt ws djusted to ph 4.5 with 1. N HCl nd centrifuged using the sme conditions. The rice rn protein precipitte (RBPP) ws otined ( modified method of Gnnsmndm nd Hettirchchy, 1995; Theerkulkit et l., 26). The protein content of RBPP ws determined y the Kjeldhl method (Assocition of Officil Anlyticl Chemists, 1995); the vlue of 5.95 ws used s protein conversion fctor (Julino, 1985). Rice rn protein extrct (RBPE) ws prepred y dispersing RBPP in DW t.8% protein (w/v). DW ws used s control. Browning inhiition in potto, nn nd pple puree nd PPO inhiition were studied. Effect of rice rn protein extrct on rowning inhiition in vegetle nd fruit puree Smples of potto, nn or pple were lended with RBPE t rtio of potto, nn or pple to RBPE of 2:1 (w/v) for 2 s. DW ws used s control. The color vlues (L*, * nd *) of the

3 Ksetsrt J. (Nt. Sci.) 48(2) 27 smples were mesured y spectrophotometer (CM-35D; Minolt; Tokyo, Jpn) t, 1, 2, 3, 4, 5 nd 6 hr of storge t room temperture. The rowning vlue ws clculted s ( L*/L *) 1; where L* is the chnge of L* t storge time nd L * is the initil L* mesurement (Luz et l., 199). The percentge rowning inhiition ws clculted s (Browning vlue control - Browning vlue inhiitor ) 1 / Browning vlue control. The hue ngle ws clculted using tn -1 */* for the first qudrnt (+*, +*), 18 + tn -1 */* for the second qudrnt ( *, +*) nd the third qudrnt ( *, *) nd 36 + tn -1 */* for the fourth qudrnt (+*, *), respectively (McGuire, 1992; McLelln et l., 1995). Effect of rice rn protein extrct on vegetle nd fruit polyphenol oxidse inhiition Potto, nn or pple (2 g) ws lended for 2 s with 2 ml of cold.1 M sodium phosphte uffer (ph 6.6) contining 1% polyvinylpyrrolidone nd.5% Triton X-1. The homogente ws centrifuged t 25,56 g t 4 ºC for 3 min ( modified method of Glezzi et l., 1981). The superntnt ws collected nd stored t -2 ºC to e used s crude enzyme. One unit of enzyme ctivity ws defined s the mount of enzyme cusing chnge in sornce of.1 t 42 nm in 1 min t 25 ºC nd ph 6.6. The PPO ctivity in crude enzyme of ech plnt ws djusted to 49 unit.ml -1 y.1 M sodium phosphte uffer (ph 6.6). RBPE diluted t 1:1 (v/v) or DW (1. ml),.9 ml of.5 M sodium phosphte uffer ph 6.6 nd 1. ml of.2 M ctechol in.5 M sodium phosphte uffer ph 6.6 were mixed nd incuted for 3 s. Then,.1 ml of crude enzyme ws dded nd mixed. The sornce t 42 nm ws immeditely mesured for 1 min using the spectrophotometer ( modified method of Lee et l., 22). The percentge PPO inhiition ws clculted s ( A 42, control - A 42, inhiitor ) 1 / A 42, control ; where A 42 is the chnge in A 42 etween time t nd the initil time t (Özoğlu nd Byındırlı, 22). Sttisticl nlysis All experiments were performed with three replictions. Sttisticlly significnt difference ws ssessed y one-wy nlysis of vrince. Significnt differences (P.5) mong tretments were detected using Duncn s multiple rnge test. Results nd Discussion Effect of rice rn protein extrct on vegetle nd fruit puree rowning nd polyphenol oxidse inhiition In previous study, the concentrtion of RBPE t.8% protein (w/v) could inhiit rowning in potto, nn nd pple puree nd it ws found tht.8% protein (w/v) RBPE inhiited rowning in potto puree slightly less thn 1% protein (w/v) RBPE; however, when the protein concentrtion incresed from 1 to 1.5 nd 2% protein (w/v), the inhiitory effect ws not significntly incresed (dt not shown). Moreover, the RBPE itself ws light rown color nd hd rice rn odor. This might led the products to e uncceptle if RBPE were pplied t high concentrtion. Therefore, RBPE t.8% protein (w/v) ws used in the current study. Kuglomsong nd Theerkulkit (214) lso found tht RBPE t.8% protein (w/v) effectively inhiited enzymtic rowning in potto. The rowning vlues of potto, nn nd pple puree treted with RBPE compred to DW re shown in Figure 1. The rowning vlues of potto puree treted with RBPE were lower thn those treted with DW for ll storge times (P.5) with vlues t 6 hr storge of nd 58.21, respectively (Figure 1). The rowning vlues of nn puree treted with RBPE were lower thn those treted with DW t 2 to 6 hr storge (P.5) with vlues t 6 hr storge of 18.4 nd 2.84, respectively (Figure 1). Moreover, the rowning vlues of pple

4 28 Ksetsrt J. (Nt. Sci.) 48(2) puree treted with RBPE were lower thn those treted with DW for ll storge times (P.5) with vlues t 6 hr storge of nd 38.2, respectively (Figure 1c). The L* vlue provides mesure of lightness. A decrese in the L* vlue indictes drker color tht is relted with higher rowning formtion (Spers nd Dougls, 1987; İyidoğn nd Byındırlı, 24). The L* vlues of potto, nn nd pple puree treted with RBPE compred to DW re shown in Figure 2. It ws found tht the L* vlues of potto puree treted with RBPE were higher thn those treted with DW for 1 to 6 hr (P.5; Figure 2), the L* vlues of nn puree treted with RBPE were higher thn those treted with DW for 2 to 6 hr (P.5; Figure 2) nd the L* vlues of pple puree treted with RBPE were higher thn those treted with DW for ll storge times (P.5; Figure 2c). The L* vlues of potto, nn nd pple puree treted with RBPE t 6 hr storge were 52.79, nd 37.19, respectively; wheres, those treted with DW hd the L* vlues of 33.65, 5.93 nd 29.49, respectively. Browning vlue DW Browning vlue RBPE c A decrese in the hue ngle indictes chnge of color from yellow to red which is indictive of enzymtic rowning (Nicoli et l., 1994). The hue ngles of potto, nn nd pple puree treted with RBPE compred to DW re shown in Figure 3. The hue ngles of potto puree treted with RBPE were higher thn those treted with DW for 1 to 6 hr (P.5) with vlues fter 6 hr storge of nd 53.24, respectively (Figure 3) The hue ngles of nn puree treted with RBPE were higher thn those treted with DW for storge time of 1, 2, 3, 5 nd 6 hr (P.5) with vlues t 6 hr storge of nd 62.91, respectively (Figure 3). The hue ngles of pple puree treted with RBPE were lso higher thn those treted with DW for 1 to 5 hr (P.5) with vlues t 5 hr storge of nd 61.7, respectively (Figure 3c). The results of the L* vlues nd hue ngles indicte tht potto, nn nd pple puree treted with RBPE hd lower rowning color thn those treted with DW. These were in ccordnce with the results for the rowning vlue. The rowning inhiition might hve een Figure 1 Browning vlues of potto (), nn () nd pple (c) puree treted with distilled wter (DW) nd rice rn protein extrct (RBPE). All smples were stored t room temperture for up to 6 hr., Mens with different letters re significntly different (P.5) for the sme storge time. Error rs indicte ± SD. Browning vlue

5 Ksetsrt J. (Nt. Sci.) 48(2) 29 due to the proteins nd peptides in RBPE. Proteins nd peptides cn ffect the PPO ctivity in t lest two wys: y recting with the o-quinone nd y chelting on copper t the ctive site of PPO (Khn, 1985). Moreover, severl reserchers hve reported tht rice rn contins ntioxidtive peptides nd sulfur mino cids (Prrdo et l., 26; Sereewtthnwut et l., 28; Adeiyi et l., 29); thus, these peptides might e the cuse of rowning inhiition in potto, nn nd L* vlue c L* vlue L* vlue Figure 2 L* vlues of potto (), nn () nd pple (c) puree treted with distilled wter (DW) nd rice rn protein extrct (RBPE). All smples were stored t room temperture for up to 6 hr., Mens with different letters re significntly different (P.5) for the sme storge time. Error rs indicte ± SD. Hue ngle c Hue ngle DW Hue ngle RBPE Figure 3 Hue ngles of potto (), nn () nd pple (c) puree treted with distilled wter (DW) nd rice rn protein extrct (RBPE). All smples were stored t room temperture for up to 6 hr., Mens with different letters re significntly different (P.5) for the sme storge time. Error rs indicte ± SD.

6 21 Ksetsrt J. (Nt. Sci.) 48(2) pple puree. Browning of potto nd pple ws lso inhiited y whey protein (Tien et l., 21), synthetic dipeptide (Girelli et l., 24) nd honey (Oszminski nd Lee, 199). The results of the percentge rowning inhiition in potto, nn nd pple puree fter storge t room temperture for up to 6 hr compred to DW re shown in Tle 1. It ws found tht RBPE could inhiit rowning in potto puree to greter level thn pple nd nn puree for ll storge times (P.5). The percentge rowning inhiition in potto, pple nd nn puree t 6 hr storge were 45.7, nd 13.47, respectively. Moreover, the effects of RBPE on potto, nn nd pple PPO inhiition (Figure 4) indicted tht RBPE produced higher percentge PPO inhiition in potto thn in pple nd nn (P.5) with vlues of 15.94, 9.9 nd 5.85, respectively. This greed with the percentge rowning inhiition in potto, pple nd nn puree. The results for the percentge rowning inhiition nd percentge PPO inhiition indicted tht RBPE could inhiit enzymtic rowning in potto more effectively thn in pple nd nn. This might hve een due to the specific inhiition of RBPE on potto PPO isozymes eing greter thn the PPO from the other sources. The PPO isozymes in plnts hve een reported to e different (Flurkey, 1986). Theerkulkit nd Boonsiripipht (29) reported tht rice rn extrct inhiited potto PPO more effectively thn nn nd pple PPO. Sukhonthr nd Theerkulkit (212) lso reported tht rice rn extrct produced greter level of potto PPO inhiition thn nn PPO. In ddition, the effectiveness of RBPE compred to commercil ntirowning gents on enzymtic rowning in potto puree ws nlyzed. It ws found tht RBPE inhiited rowning in potto puree more thn 5, 1 nd 2 mm scoric cid; nd 5 nd 1 mm citric cid (Kuglomsong nd Theerkulkit, 214). CONCLUSION RBPE could inhiit enzymtic rowning in potto, nn nd pple puree. RBPE produced greter level of percentge rowning inhiition nd percentge PPO inhiition in potto thn in pple nd nn. Therefore, RBPE hs potentil to e used s n enzymtic rowning inhiitor in vegetle nd fruit puree, especilly potto puree. Percentge PPO inhiition Figure 4 Percentge polyphenol oxidse (PPO) inhiition of potto, nn nd pple in model system treted with rice rn protein extrct.,, c Mens with different letters re significntly different (P.5). Error rs indicte ± SD. c Potto Bnn Apple Tle 1 Percentge rowning inhiition in potto, nn nd pple puree treted with rice rn protein extrct. All smples were stored t room temperture for up to 6 hr. Source Percentge rowning inhiition (t storge time; hr) Potto 66. ± ± ± ± ± ±.96 Bnn ± 4.81 c 2.33 ± ± ± ± 1.62 c ± 2.77 c Apple 3.49 ± ± ± ± ± ±.8,, c Men vlues (± SD) with different letters re significntly different (P.5) for the sme storge time.

7 Ksetsrt J. (Nt. Sci.) 48(2) 211 Acknowledgements The uthors would like to express their sincere grtitude to the Ksetsrt University Reserch nd Development Institute (KURDI) nd the Thilnd Reserch Fund through the Royl Golden Juilee Ph.D. Progrm (Grnt No. PHD/5/2551). Specil thnks re recorded to Ptum Rice Mill nd Grnry Pulic Co. Ltd., Pthum Thni, Thilnd for providing the rice rn for the reserch. LITERATURE CITED Adul-Hmid, A. nd Y.S. Lun. 2. Functionl properties of dietry fire prepred from deftted rice rn. Food Chem. 68: Adeiyi, A.P., A.O. Adeiyi, J. Ymshit, T. Ogw nd K. Murmoto. 29. Purifiction nd chrcteriztion of ntioxidtive peptides derived from rice rn protein hydrolystes. Eur. Food Res. Technol. 228: Assocition of Officil Anlyticl Chemists Officil Methods of Anlysis. 16th ed. Assocition of Officil Anlyticl Chemists, Arlington, VA, USA. 155 pp. Ates, S., S. Pekyrdimci nd C. Cokmus. 21. Prtil chrcteriztion of peptide from honey tht inhiits mushroom polyphenol oxidse. J. Food Biochem. 25: But, J.G. nd H.E. Moline. 21. Prevention of rowning of potto slices using polyphenoloxidse inhiitors nd orgnic cids. J. Food Qul. 24: Cmps-Ríos, M.D.J., J.N. Mercdo-Ruiz, M.A. Vldéz-Covrruis, A.R. Isls-Ruio, A.M. Mendoz-Wilson nd R.R. Blndrán- Quintn Hydrolystes from whet rn lumin s color-dding gents nd inhiitors of pple polyphenol oxidse. J. Food Biochem. 36: Cntos, E., J.A. Tudel, M.I. Gil nd J.C. Espín. 22. Phenolic compounds nd relted enzymes re not rte-limiting in rowning development of fresh-cut pottoes. J. Agric. Food Chem. 5: Flurkey, W.H Polyphenoloxidse in higher plnts. Plnt Physiol. 81: Fu, B., H. Li, X. Wng, F.S.C. Lee nd S. Cui. 25. Isoltion nd identifiction of flvonoids in licorice nd study of their inhiitory effects on tyrosinse. J. Agric. Food Chem. 53: Glezzi, M.A.M., V.C. Sgrieri nd S.M. Constntinides Isoltion, purifiction nd physicochemicl chrcteriztion of polyphenoloxidses (PPO) from dwrf vriety of nn (Mus cvendishii, L). J. Food Sci. 46: Girelli, A.M., E. Mttei, A. Messin nd A.M. Trol. 24. Inhiition of polyphenol oxidses ctivity y vrious dipeptides. J. Agric. Food Chem. 52: Gnnsmndm, R. nd N.S. Hettirchchy Protein concentrtes from unstilized nd stilized rice rn: Preprtion nd properties. J. Food Sci. 6: , 174. Gnngui, S.N., S.L. Nimke nd L.P. Koume. 21. Prtil chrcteriztion of new peptide from Ivorin red onion tht inhiits polyphenol oxidse nd enzymtic rowning of edile ym (Dioscore cyenensis-rotundt cv Longô). Ching Mi J. Sci. 37: Helm, R.M. nd A.W. Burks Hypollergenicity of rice protein. Cerel Foods World 41: Interntionl Rice Reserch Institute World Rice Sttistics. [Aville from: [Sourced: 19 Ferury 213]. İyidoğn, N.F. nd A. Byındırlı. 24. Effect of l-cysteine, kojic cid nd 4-hexylresorcinol comintion on inhiition of enzymtic rowning in Amsy pple juice. J. Food Eng. 62: Jng, M.S., A. Snd, H. Ushio, M. Tnk nd T. Ohshim. 22. Inhiitory effects of

8 212 Ksetsrt J. (Nt. Sci.) 48(2) Enokitke mushroom extrcts on polyphenol oxidse nd prevention of pple rowning. LWT-Food Sci. Technol. 35: Julino, B.O Rice: Chemistry nd Technology. 2nd ed. Americn Assocition of Cerel Chemists Inc. St Pul, MN, USA. 774 pp. Kewk, K., K. Portongkum nd C. Theerkulkit. 29. Preprtion of ultrfiltered rice rn extrct nd some fctors ffecting its rowning inhiition in potto puree. Prep. Biochem. Biotechnol. 39: Khn, V Effect of proteins, protein hydrolyztes, nd mino cids on o-dihydroxyphenolse ctivity of polyphenol oxidse of mushroom, vocdo nd nn. J. Food Sci. 5: Kto, N., S. Sto, A. Ymnk, H. Ymd, N. Fuw nd M. Nomur Silk protein, sericin, inhiits lipid peroxidtion nd tyrosinse ctivity. Biosci. Biotechnol. Biochem. 62: Kuglomsong, S. nd C. Theerkulkit Effect of rice rn protein extrct on enzymtic rowning inhiition in potto puree. Int. J. Food Sci. Technol. 49: Luz, T.P., J.H. Lillemo nd P.S. Toukis Inhiition of polyphenol oxidse y proteolytic enzymes Killer Enzymes, pp In Proceedings of the Symposium on the 2th Interntionl Symposium Interntionl Federtion of Fruit Juice Producers, My Pris, Frnce. Lee, M.K., Y.M. Kim, N.Y. Kim, G.N. Kim, S.H. Kim, K.S. Bng nd I. Prk. 22. Prevention of rowning in potto with het-treted onion extrct. Biosci. Biotechnol. Biochem. 66: Li, B., Y. Hung nd S.M. Pskewitz. 26. Hen egg white lysozyme s n inhiitor of mushroom tyrosinse. FEBS Lett. 58: McGuire, R.G Reporting of ojective color mesurements. HortScience 27: McLelln, M.R., L.R. Lind nd R.W. Kime Hue ngle determintions nd sttisticl nlysis for multiqudrnt Hunter L,, dt. J. Food Qul. 18: Nicoli, M.C., M. Anese nd C. Severini Comined effects in preventing enzymtic rowning rections in minimlly processed fruit. J. Food Qul. 17: Ortíz-Estrd, A.M., J.N. Mercdo-Ruiz, J.M. Grcí-Roles, A.R. Isls-Ruio, A.M. Mendoz-Wilson nd R.R. Blndrán- Quintn Whet rn gloulins: Competitive inhiitors of mushroom tyrosinse. Food Sci. Biotechnol. 21: Oszminski, J. nd C.Y. Lee Inhiition of polyphenol oxidse ctivity nd rowning y honey. J. Agric. Food Chem. 38: Özoğlu, H. nd A. Byındırlı. 22. Inhiition of enzymic rowning in cloudy pple juice with selected ntirowning gents. Food Cont. 13: Prrdo, J., E. Mirmontes, M. Jover, J.F. Gutierrez, L.C. de Terán nd J. Butist. 26. Preprtion of rice rn enzymtic extrct with potentil use s functionl food. Food Chem. 98: Spers, G.M. nd F.W. Dougls Mesurement of enzymtic rowning t cut surfces nd in juice of rw pple nd per fruits. J. Food Sci. 52(5): Sereewtthnwut, I., S. Prpintip, K. Wtchirruji, M. Goto, M. Sski nd A. Shotipruk. 28. Extrction of protein nd mino cids from deoiled rice rn y sucriticl wter hydrolysis. Bioresour. Technol. 99: Sukhonthr, S. nd C. Theerkulkit Inhiitory effect of rice rn extrct on polyphenol oxidse of potto nd nn. Int. J. Food Sci. Technol. 47: Theerkulkit, C. nd K. Boonsiripipht. 29.

9 Ksetsrt J. (Nt. Sci.) 48(2) 213 Extrction of rice rn extrct nd some fctors ffecting its inhiition of polyphenol oxidse ctivity nd rowning in potto. Prep. Biochem. Biotechnol. 39: Theerkulkit, C., S. Chiseri nd S. Mongkolknchnsiri. 26. Extrction nd some functionl properties of protein extrct from rice rn. Ksetsrt J. (Nt. Sci.) 4: Thongsook, T. nd W. Tiyoonchi Inhiitory effect of sericin on polyphenol oxidse nd its ppliction s edile coting. Int. J. Food Sci. Technol. 46: Tien, C.L., C. Vchon, M.A. Mteescu nd M. Lcroix. 21. Milk protein cotings prevent oxidtive rowning of pples nd pottoes. J. Food Sci. 66: Wng, M., N.S. Hettirchchy, M. Qi, W. Burks nd T. Sieenmorgen Preprtion nd functionl properties of rice rn protein isolte. J. Agric. Food Chem. 47: Zhu, Y., Z. Pn nd T.H. Mchugh. 27. Effect of dipping tretments on color stiliztion nd texture of pple cues for infrred drylnching process. J. Food Process. Preserv. 31: