サツマイモの熱風乾燥における含水率および L- アスコルビン酸の変動解析

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1 サツマイモの熱風乾燥における含水率および L- アスコルビン酸の変動解析誌名宮城大学食産業学部紀要 = Jurnal f Miyagi University Schl f Fd, Agricultural and Envirnmental Sciences ISSN 著者巻 / 号折笠, 貴寛椎名, 武夫田川, 彰男 5 巻 1 号掲載ページ p 発行年月 211 年 3 月農林水産省農林水産技術会議事務局筑波産学連携支援センター Tsukuba Business-Academia Cperatin Supprt Center, Agriculture, Frestry and Fisheries Research Cuncil Secretariat

2 ':OJ,x j ;::!.f-; 1:1: ill" f: ;\il*c It: 5 (l ) : (2 ll) J lviiyagi Univ. Sch. Fd Agri. Envirn. Sci. 5 (1 ) :35-42 (211 ) Analysis f Changes in Misture Cntent and L-Ascrbic Acid f Sweet Ptates during Ht Air Drying Takahir ORTKASA*, Take SHIINA 1, Aki TAGAWA 2 Abstract Changes in misture cntents and L-ascrbic acid f sweet ptates during ht air drying were investigated at temperatures f and 6 C. The drying prcess was evaluated using measured misture cntent data f the drying test. The measured data was fitted t a cmbinatin f the expnential drying mdel and an infinite plane sheet mdel fr the diffusin equatin. The empirical misture cntent changes agreed well with the mdels. An Arrhenius-type equatin was used t estimate the temperature dependency f the diffusin cefficient f sweet ptates. Changes in the L-ascrbic acid cntent f sweet ptates during ht air drying were analyzed using a first-rder reactin rate equatin t mdel changes in the decmpsitin f the L-ascrbic acid cntent. The activatin energy required fr the decmpsitin reactin during the ht air drying f sweet ptates was estimated t be 48.8 kj ml-i. (Received September : Accepted February ) Key wrds: sweet ptat, ht air drying. misture cntent, L-ascrbic acid. Arrhenius-type equatin 1. Intrductin The sweet ptat (lp17wea batatas Lam.) is an imprtant agricultural prduct; it is ne f the mst efficient fd crps in terms f calric value per area cultivatin and is relatively easy t grw. even in pr. dry sil (Antni et al.. 28). The sweet ptat greatly cntributes t the nutritinal needs f the human diet by prviding at least 9% f daily dietary requirements. except prtein and niacin (Buwkamp. 1985). because the rt prtin f the plant is rich in nt nly /3 -cartene, fd fiber. and ptassium ins (Lin et al.. 25) but als carbhydrate and fat. Sweet ptates must be cnsumed within a few weeks after they are harvested r must be dried t lwer the misture cntent fr lng-term strage (Diamante and Ivlunr. 1991). Ht air drying has been used as a simple and cmmn methd fr drying fruits and vegetables (Ogura. 1993: Lenid et al.. 26). Althugh sme studies described the ht air drying characteris- tics f ther fruits and vegetables with high misture cntents. such as tmates (Dymaz, 27), apples (Sjhlm and Gekas. 1995). kiwifruits (Orikasa et al.. 28), garden beets. and carrts (Pabis and Jars. 22), a suitable drying mdel fr sweet ptates has nt yet been established. The change in nutrient cntent during drying is an imprtant factr in the prductin f high-quality dried prducts. The sweet ptat is rich in L-ascrbic acid, a functinal nutrient cnstituent. H wever, the amunt f L-ascrbic acid in sweet ptates decreases with drying time, and details cncerning the changes in L-ascrbic acid f sweet ptates during ht air drying have nt yet been reprted. The bjectives f this study were as fllws: (1) T investigate the ht air drying characteristics f sweet ptates: (2) evaluate a suitable drying mdel fr sweet ptates using misture cntent data: and (3) analyze changes in the L-ascrbic acid cntent f I Natinal Fd Research InslilLlle, Graduare Schl f Hrticulture. Chiba Uni versity * Crrespndi ng aulhr (E mail : rikasa(c!.myu.ac.jp) 35

3 Jurnal f Miyagi University Schl f Fd. Agricultural and Envirnmental Sciences 5 ( 1), 211 sweet ptates during ht air drying. 2. Materials and methds 2.1. Materials Sweet ptates were purchased frm a lcal market and stred in a refrigeratr at 15 C until needed, The initial misture cntent f the sweet ptates, which was measured using a methd that uses film with diatmite (Japan Fd Research Labratries, 1973), was 1.94 ±.9 n a dry basis (d,b.. decimal) (=.645 ±.1 n a wet basis) (n = 1), The experimental samples cnsisted f rectangular blcks f 5 x 2 x 1 mm cut frm the center f each sweet ptat, 2.2. Ht air drying test Drying tests [frm the initial misture cntent t.5 (d.b.. decimal)j were carried ut at temperatures f 3. 4, 5. and 6 C using a ht air drying chamber (WFO-7, EYELA. Japan) The air velcity during drying was.3 m s J, and the chamber vlume was 7 L The samples were weighed with a digital balance at,5-h intervals, and the misture cntent was calculated (d,b.. decimal). The misture rati. MR, f each sample was determined using the fllwing equatin: M-M MR= (. M-M" Orikasa et al. (21) reprted that equilibrium misture cntents f sweet ptates during ht air drying at temperatures f 3, 4, 5. and 6 C were.115,.49,.38. and.29, respectively. These values were substituted in equatin (1) t estimate the misture rati. MR. fr this study. Drying tests at each predetermined temperature were repeated three times. (1) cntents f the samples were measured at five r six misture cntent levels frm the initial misture cntent t apprximately.5 (d.b.. decimal) at temperatures f 3, 4, 5. and 6"C. Ttal quantities f L-ascrbic acid in the test samples [mg] were calculated by multiplying the measured cntent [mg/ loo g fresh weight] by the initial sample weight [g]. L-ascrbic acid cntents were cnsiderably different between samples, In this study, changes in L ascrbic acid cntent were evaluated using the residual rati f L-ascrbic acid cntent. which was defined as the value btained by dividing the ttal quantity f L-ascrbic acid in a dried sample by the ttal quantity f L-ascrbic acid in the initial sample befre drying. IvIeasurements f each sample at each predetermined temperature were repeated three times Data analysis Analysis f variance (ANOV A) was cnducted using Micrsft Excel t determine the effect f variable data n drying parameters. The LSD multiple range test methd at a significance level f.5 was used when a difference in means was detected. The parameters f equatins (3). (4). and (5) were estimated by the nnlinear least squares methd using Visual Basic fr Applicatins (VBA) and Micrsft Excel. 3. Results and discussin 3.1. Ht air drying characteristics f sweet ptates In this study. the diffusin thery was used t mdel the drying f sweet ptates. The slutin f the diffusin equatin is an infinite series (Crank. 1975). as shwn in the fllwing equatin (2) 2.3. L-Ascrbic acid cntent L-ascrbic acid was measured accrding t the methd f Nishiyama and Ota (25). A reflectin phtmeter (RQ-flex-plus, Merck. Japan) was used t measure the L-ascrbic acid cntent [mg/ loo g fresh weight] in the sample material. The L-ascrbic acid The infinite series n the right side f equatin (2) rapidly cnverges t the first term when the Furier number (F = Dl/l2) becmes large. yielding equatin (3): 36

4 OR JI< r\sa " Anal)"sis f Changes in :\'Iislure Cn lent and L-Ascrbic Acid f Sweel POlales during HOl Air Drying T he relatinship between the misture rati, MR. and drying time is pltted n a semilgarithmic scale. The parameter BI in equatin (3) is the intercept n the MR axis (lgarithmic axis). Figure 1 shws that a linear relatinship is btained fr the first few hurs f drying [frm an apprximate misture cntent f 1.1 (d.b, decimal) t the final stage f drying], and the intercept. BI. is apprximately O.S. Using the measured misture cntent. the parameter B I in equatin (3) at the fur predetermined temperatures was determined thrugh the nnlinear least squares methd (Deming methd). The determined values fr parameter BI were.s s5. and.86 at , and 6 e. respectively (RMS =.814 x x 1-:l). In cntrast. BI in equatin (3) during the first few hurs [frm initial misture cntent t apprximately 1.1 (d.b.. decimal)j was estimated t be apprximately 1.. Substituting B I = 1. int equatin (3) crrespnds t the fllwing expnential mdel [equatin (4)]: M-M, '- = exp(-k/) MO-M,. Values fr BI in equatin (3) fr a sphere mdel. an infinite plane sheet mdel. and an expnential mdel (3) (4) are 6/ 1\:2 =.61. 8/ rr< =.81. and 1., respectively (Tagawa et al., 23). In this study, the expnential mdel as a drying mdel with misture cntent ranging frm the initial value t apprximately 1.1 (db.. decimal) and the infinite plane sheet mdel fr the diffusin equatin frm apprximately 1.1 (d.b. decimal) t the final stage f drying were used fr the drying mdel f sweet ptates during ht air drying Mdeling the ht air drying prcess fr sweet ptates The misture cntent change in sweet ptates ranging frm the initial value t apprximately 1.1 (d.b., decimal) was mdeled with the expnential mdel [equatin (4)] because the value f BI in equatin (3) fr this perid was arund 1.. The parameter kl in equatin (4) was determined by a least squares methd using measured misture cntent data. Table 1 shws the calculated values fr parameter!n in equatin (4) at the [ur predetermined temperatures. Figure 2 cmpares the measured and calculated results frm equatin (4). The slid lines in Fig. 2 represent the calculated results frm equatin (4). The measured results agree well with the calculated results [RMS = (db., decimal)j. Frm apprximately 1.1 (d. b., decimal) t the final stage f drying. an infinite plane sheet mdel was Q) , --- Cf).2 2: D:,. 3 uc 4 u C 5 C 6 C Calc IS Drying time [h] Fig. 1. Relatinship between the misture rati MR and the drying time f sweet ptat during ht air drying. 37

5 Jurnal f ivliyagi University Schl f fd. Agriculwral anc! Envirnmental Sciences 5 (I ). 211 Table 1 Calculated values f parameter k1, k2 and Me the rt mean square errr (RMS) fr equatin (3) and (4) Equatin (3) Equatin (4) Temperature [nc] kl [h IJ RMS [decimal (d.b.l] k, [h ll,\ie RMS [decimal (d.b.)l[decimal (d.b.)] O. \ used fr the diffusin equatin t predict the change in misture cntent f the sweet ptates. The slutin t the diffusin equatin fr an infinite plane sheet mdel is given by equatin (5) (Crank. 1975): 2 M - Me _ 8 {_ D(2i + 1)21[ t} ---'- - L... " ex p, M - Me i _ O (21 + 1)- 1[- 4/- (5) Of) 8 =L. "exp{-(2i+i)2k2 t} i O (21 + I) - 1[- where k2 is equal t DAI2 = (Drr2)/ (4/2) and AI/, = rr12. The parameters k2 and JV1e in equatin (5) were determined by a nnlinear least squares methd (false psitin methd) (Tagawa et al 23) using the measured misture cntent data frm the sweet ptat samples. Table 1 shws the calculated values f parameters k2 and lvie fr equatin (5). Figure 2 shws the cmparisn belween the measured and calculated results frm equatin (5) fr the sweet ptates. The dashed lines in Fig. 2 represent the calculated results frm equatin (5). The measured results agree well with the calculated results [RMS = (d.b.. decimal)]. The results supprt the ntin that the drying prcess fr the sweet ptat samples frm apprximately 1.1 (d. b.. decimal) t the final stage f drying is in the secnd falling rate perid and that the drying characteristic can be explained using the infinite plane sheet mdel. Hence. changes in the misture cntent f the sweet ptat samples during ht air drying were well estimated by a cmbinatin f an expnential mdel and an infinite plane sheet diffusin mdel. The diffusin cefficient. D. has been extensively used t evaluate the fundamental parameters f the drying prcess (Wu et a l.. 27). The diffusin 2., , /""' C...c: " '-' 4 C (;i 1.5 r C SO C U (.) 6 C 1. Calc.... c E r U... ill O.S.... :...,2 [/'J IS Drying time [h] Fig. 2. Cmparisn f measured and calculated results frm equatins (3) and (4) fr sweet ptat. The slid line represents data calculated using equatin (3) The dashed line represents data calculated using equatin (4) 38

6 ORTKASA. Analysis f Changes in :vliswre Cntent and L-r\scrbic Acid f Sweet POLates during I-IL Air Drying cefficient. D. was estimated using the assumptin that the half-thickness. l (l = half-thickness fr an infinite plane = 3.5 mm frm the previus measurement). is cnstant within the examined range. The calculated D values were.95 x X 1' X 1. 1 and 3.9 x 1. 1 m 2 S I fr the drying lemperatures f and 6 C, respectively. The temperature dependency f the diffusin cefficient. D. is expressed by the fllwing Arrheniustype equatin (Pinaga et a ): The parameters D and E in equatin (6) were determined by a least squares methd using the estimated diffusin cefficient. D. fr the ht air drying f sweet ptates. The calculated cnstants were D = 3.17 X 1. 5 m! S-I and E = 31.8 k] ml l. Figure 3 shws the relatinship between the diffusin cefficients and the reciprcal f abslute temperature fr sweet ptates. The calculatins frm equatin (6) agree well with the diffusin cefficient values. The results cnfirmed that an Arrhenius-type equatin is useful fr describing the relatinship between the diffusin cefficient. D. and the abslute temperature. T. fr sweet ptates. (6) 3.3. Residual rati f L-ascrbic acid cntent The residual rati f L-ascrbic acid cntent decreased as drying time increased. Hsaka (1972) demnstrates that the decmpsitin reactin fr L ascrbic acid may be represented by a first-rder reactin. Therefre, the measured residual rati during drying was applied t the first-rder reactin rate equatin. as fllws: dx =k'(i-x) dt Equatin (7) (7) can be slved under the initial cnditin f x: = t t = ; thus. equatin (8) is given as fllws: 1 In-- = k't I-x A least squares methd was applied t equatin (8) with a measured residual rati. The estimated decmpsitin rate cefficient. if'. was and.111 h- I at and 6 c' respectively The values fr k' increased as drying temperature increased. The temperature dependency f k' was examined using the fllwing equatin: k'=d.exp (- RET J (9) (8) The cnstant. d. and the activatin energy. E. in V, '" Q... c <l.) 1-9,- 'u 1-1 4: <l.) u c D=3.17X lo-a'exp - [-T- 383 J VJ.,-' ii: R2= Reciprcal f the drying temperature TI X 1 3 [K-I] Fig. 3. Arrhenius relatinship fr the diffusin cefficients f misture in sweet ptat. 39

7 Jurnal f i\iiyagi University Schl f Fd. Agricultural and Envirnmemal Sciences 5 (j l. 211 equatin (9) were determined by a least squares methd using the decmpsitin rate cefficient. k'. The calculated cl and E values were 5.22 x 1 6 h ' and 48.8 kj ml", respectively. Figure 4 shws the Arrhenius relatinship fr the decmpsitin rate cefficient. k'. F igure 4 cnfirms that an Arrheniustype equatin [equatin (9)] was applicable t the relatinship between the decmpsitin rate cefficient. k', and the drying temperature, T, fr the ht air drying f sweet ptates. These experimental results culd cntribute the prductin f high quality dried sweet ptat and t the develpment f drying thery fr sweet ptat. 4. Cnclusins Drying characteristics f sweet ptat samples after ht air drying were investigated. The predicted drying mdel f the samples was als cnsidered, and changes in L-ascrbic acid cntent f the samples during ht air drying were examined. The cnclusins are summarized as fllws: 1) Misture cntent changes in the sweet ptat samples during ht air dryi ng were predicted by a cmbinatin f an expnential drying mdel and an infinite plane sheet mdel fr the diffusin equatin. 2) The diffusin cefficient. D, was related t the drying temperature by an Arrhenius-type equatin. and the activatin energy fr misture diffusin was estimated t be 31.8 kj ml". 3) The decmpsitin rate cefficient. k,'. fr L ascrbic acid cntent depended n the drying temperature. The activatin energy fr the decmpsitin f L-ascrbic acid was estimated t be 48.8 kj ml-' using an Arrhenius-type equatin. Nmenclature B c/, D D E /(2 k i\tl Me M i'vir shape factr (decimal) parameter f equatin (9) diffusin cefficient [m 2 s"] cnstant equivalent t the diffusivity at infinitely high temperature [m 2 s"] activatin energy [kj ml"] drying cnstant f first falling rate perid [h l] drying cnstant f secnd falling rate perid [h 11 decmpsitin rate cefficient fr the L ascrbic acid cntent [h l ] characteristic length [m] misture cntent (db. decimal) equilibrium misture cntent (d.b. decimal) initial misture cntent (d.b. decimal) misture rati (decimal) R universal gas cnstant (8.314 J ml' K-') RMS rt mean square k'=5.22 X l6. exp [ 5!7 ] ::: R"=.996 Vl..1 E u Cl) '" Cl) a:i u Cl) U Reciprcal f the drying temperature TI X 1 3 [K I] Fig. 4. Arrhenius relatinship fr the decmpositin rate cefficient k' f ascrbic acid in sweet ptat. 4

8 OR1K ASA : Analysis f Changes in i\l[isture C11lel1l and L- Ascrbic Acid f Sweet Ptates during Ht Air Drying T,1: abslute temperature [KJ drying time [h] residual rati f L-ascrbic acid decreased after t, h (decimal) characteristic value [m- I ] References Antni, G. c.. Alves. D. G.. Azubel. P. M.. MUH. F. E. X.. & Park. K. ]. (28). Influence f smtic dehydratin and high temperature shrt time prcesses n dried sweet ptat (lpo?nea balalas Lam.). JvnwL f Fel Engineering, 84, Buwkamp. ]. C. (1985). Sweet, pl.al prelvcl.s: A 1wt,um.l, 1'C.SO'LI,rce Jr lhe t1'op1:cs Press, Flrida. (pp.3-7). CRC Crank, ]. (1975). The lvicli,hematics f D1:jJilsin (2nd ed.. pp.47-49). Oxfrd University Press. New Yrk. Diamante. L. M., & Munr. A. P. (1991). Mathematical mdeling f ht air drying f sweet ptat slices. Inlenwlin.l Jnrnal f Fel Science Clnel Technlgy, 26, Dymaz, I. (27). Air-drying characteristics f tmates. Jv?'Jwl j Fel ElI.g1:neering, Hsaka. H. (1972). Handbk qf Jel engineering (pp.57-6). Kagakukugyusya, Tky. (In ]apanese) Japan Fd Research Labratries. (1973). Reprt, qf Japan Fel Research Labratries, (In Japanese) Lenid, A. B.. Vladimir, P. G.. Andrew, V. B.. Alexander. M. L.. V aleriy. L.. & Vladimir, A K. (26). The investigatin f lw temperature vacuum drying prcesses f agricultural materials. Jurnal qf Fel Engineering, 74, Lin. Y. P.. Tsen. ]. II., & King. V. A E. (25). Effects f far-infrared radiatin n the freeze-drying f sweet ptat. Jurnal qf Fel En,Cj1:neeri17,g, 68, Nishiyama, 1.. & Ota, T (25). Applicatin f RQflex methd fr the rapid measurement f ascrbic acid in the fruit f Act1:m:clia species. The Faculty j1lrnal qf KmazC/,wa Wmen's Jvnir Cllege, (In] apanease) Ogura. N. (1993). Thery and Methd f Preserving fr Fd. In Fel Prcessing Sluely (pp.3-35). Kenpakusha, Tky. (In] apanese) Orikasa. T, Wu, L.. Shiina, T, & Tagawa, A (28). Drying characteristics f kiwifruit during ht air drying. J'umal JJcl enginee? i17,g. 85(2) Orikasa, T, Wu, L.. And. Y., Muramatsu, y', Ry, P.. Y an, T. Shiina, T, & Tagawa. A (21). I-lt air drying characteristics f sweet ptat using misture srptin istherm analysis and its quality changes during drying, Inlenwlinal, JOl.l.?'7w.l j Fel Eng'i?teen:17g, 6(2). Article 12. Pabis, S., & ] ars, M. (22). The first perid f cnvectin drying f vegetables and the effect f shape-dependent shrinkage. B1'syslems Eng i- 17,ee1'1:17, 81(2), Pinaga, F.. CarbnelL]. V., Pena, ]. L.. & Miguel. ]. ]. (1984). Experimental simulatin f slar drying f garlic using an adsrbent energy strage bed, JwnaL qf'fel En1:1Iee1'/;ng, 3, Sjhlm, 1.. & Gekas, V. (1995). Apple shrinkage upn drying. JO'Li?'Jwl q/ Fel Eng'i1We?'ing, 25, Tagawa, A., IVluramatsu, Y.. Nagasuna, T, Yan, A, Iimt, M.. & Murata, S. (23). Water absrptin characteristics f wheat and barley during saking. T1'cLTlsacl'in qf Ihe ASAE, 46(2), , Wu, L.. Orikasa, T.. Ogawa, Y., & Tagawa, A (27), Vacuum drying characteristics f eggplants. JO'U?'Jwl q/fel Eng'inee?'ing, 83,

9 J llrnal f :Vliyagi University Schl f Fd. AgriclilLUral and Envirnmental Sciences 5 (l I, 211 -lj- '/? 1 1:- )1l1:t:J3 t -B'-7J($J3 J: O"L- 7 A :1 )v' /O) fjj"*jf ' 3, 4, 5il J:. (Y6 C (J)ilTIUtlci" -f = il v \ -C, -IT 'J? 1.:c (J)\JffiUliZ:):tJ;' ffv \, -IT 'J? 1.:c *Z::): ;jq (J) t%? 7J( ' 1til J:. [f'l - 7 A )v t:' :/ Wi1>:1U="":) v \ -C tlj,'ijj!t L t.:: '2?7J($ 1ttii::1Wx:.:c T')v il J:. U'iJ1:1X7]'l! :ito);firr;iuff1r.:c T' )H= J:. WI1rI-" L, jilj"j.:c T')v J:. 1' G Lt.:: l'\ilfu:: iwj 7t ln((il < - 1]: L t.:: t?*,'.:c y)v J: G Lt.::i)tlrHt,Wx: = Ii, 7 v'=:' rj A :J (J) ijii\j1t\tr t1ij{ Nz,66 G Lt.:: \)ffiu1hutl i! f= il ft l.l L - 7 A )v t:' :/ f)l1>: 1t ti 1 ij(j3jt- f= f/(: -J -=- C ij' 7J 2 L, +r 'J? 1.:c(J)rMffiUliZ::):tJ;'<)fQTin=ilft l.ll- 7 A )v t:' :/M5j'-fiJ!O)ij!"Tt11t.l;;f, )v+- ti48. 8 kj m]'[ C the 2 Lt.:: I 11 : JLlrfjli1;AJm ' i:{.if,t' jiwi;f.i:'>ft l ij f ':i'ti)!kllil it.if,ititfof':i\:jj!j, -=r';\r'k't:j("it I'll';:"i" l ij f :Jl 42

水槽中で培養したマコンブ胞子体の子嚢斑形成と生長におよぼす水温及び光周期の影響

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サツマイモの熱風乾燥における含水率および L- アスコルビン 酸の変動解析

サツマイモの熱風乾燥における含水率および L- アスコルビン酸の変動解析