KINETICS OF TEXTURE DEGRADATION IN APPLES DURING

Transcription

1 KINETICS OF TEXTURE DEGRADATION IN APPLES DURING THERMAL PROCESSING EV ANGELOS S. LAZOS, DIONY<>SIOS C. SERVOS AND DEMETRIOS PARLIAROS Depatment of Food Technology, Faculty of Food Technology & Nutition, TEl of Athens, Agiou Spiidonos SI., Egaleo , Athens, Geece Instumental Textue Pofile Analysis can be used in studying themal degadation of apple textue. Heating time and tempeatue significantly educed factuability, hadness, enegy equied duing fist compession and gumminess in both Red and Golden Delicious apples. Heating time did not significantly affect changes of spinginess, cohesiveness and chewines in both vaieties. The changes in enegy equied duing second compession wee significant fo Red but not fo Golden Delicious apples. Two fist-ode kinetic mechanisms (I & 2) ae equied to descibe changes of apple textue duing themal pocessing. The ate constant fo I was at least 16 times that fo 2; activation enegy was kjm-1 fo both. The z values wee C and QIO coefficients fo both mechanisms_ Such esults can be used to impove themal pocesses fo apples. KEY WORDS: activation enegy, fist ode kinetic mechanism, heat teatment, mechanical popeties, heology

2 Duing heat teatment, foods undego changes in nutients, textue, flavou and colou; of these textue is the most appaent and the most impotant, especially in fim, fleshy fuits such as apples and peasl. The tem textue is used to descibe both sensoy attibutes and mechanical popeties of food in esponse to applied foces, and thee have been many attempts to coelate sensoy and instumental (heological) measuements of textuel s,6 Instumental measuement was advanced by the Geneal Foods Textue Pofile Analysis (TPA) technique2.7. 8,9.lo, in which the foce-time cuves yielded seven paametes, namely Factuability, Hadness, Cohesiveness, Adhesiveness, Spinginess, Gumminess and Chewiness. As all plant species and individuals diffe in chemical composition and histological stuctuell, thee is inheent vaiability and nonhomogeneity which inceases the vaiance of instumental measuementsl2. Holdswothl) has eviewed the effect of heating on fuits and Fletche14 epoted that the vaiation in mechanical popeties of apple slices was highe in pocessed than in aw fuit. Van Woensel and de BaedemaekelS epoted that the change of apple fimness with ipening and pocessing is a vey complex phenomenon. Wothington and Yeatmanl6 epoted that fimness vaies between tees, apples, vaieties, type of pobe, size of apple and position on apple. Boune l7 attibuted the lack of a eliable measue of apple textue to high fuit-to-fuit vaiability, substantial diffeences among seasons, modeate softening duing stoage and the tendency of attibutes to change in diffeent diections and at diffeent ates. Kinetic data on themal degadation of food textue can be used fo design of impoved pocesses to educe loss of all aspects of poduct quality. The ate of softening of vaious fuits and vegetables is appaently fist-ode" 12,18,19,2o Huang and Boune20 suggested that in seveal vegetables the ate of softening is consistent with two appaent fist-ode kinetic mechanisms, I and 2; mechanism I is pobably due to pectin changes in the intelamella spaces. The ate constants fo mechanism I wee moe than 20 times geate than those of mechanism 2, and the appaent Ahenius activation enegy values anged between 21.4 and kjm-1 fo both mechanisms. Anantheswaan et al.12 epoted that the loss of hadness in apples followed a fist-ode kinetics and the activation enegy was found to be and 65.3 kjm 1 fo Cotland and Spigold vaieties, espectively. They also epoted z values of 24.8 and 42.4 C fo the two vaieties, espectively. Physical

3 textual chaacteistics wee found to be a function of heating time and tempeatue, and apple vaietyi The pesent study was undetaken to detemine the effect of shot and long heating times and of tempeatue on loss of physical textue of apples, and to veify the "appaent fistode kinetic model" fo vaious instumental textual paametes. Red and Golden Delicious apples, gown in Volos aea, wee puchased fom the Cental Fuit and Vegetable Maket of Athens (Geece). They wee held unde efigeation (O C, 90% RH) fo a few days until pocessing. Only undamaged apples wee manually peeled and coed and then diced into 10 mm cubes in a dice (SOLlA-M 10, Fance) and kept unde tap wate. Afte emoval of ove- and undesized pieces, the pocessing method of Anantheswaan et al.12 was applied with some modifications. Apple dice (120 g) wee filled into a 40 Ix200 (I03x5! mm) can followed by 240 g wate at a tempeatue equal to that of pocessing o 100 C when pocessing tempeatues geate than 100 C wee used. They wee then pomptly sealed and placed in a peheated, themostatically contolled wate o oil bath. Tempeatue vaied fom C, heating times fom 5 to 35 min (long heating times). At the end of heating, the cans wee apidly cooled by cold (lo C) unning wate. The pocessed cans wee stoed at 0-2 C fo 24 h and then measued. Thee to 5 cans pe apple vaiety wee used fo each time-tempeatue combination. Huang and Boune20 and Anantheswaan et al12 obseved steep initial loss in seveal textual paametes, mainly softening, attibuted to a fist-ode kinetic mechanism-i. These shot heating time textual changes wee measued as follows: Five eplicates of apple dice (20-25 g) wee added to peheated (60-90 C) test tubes (50x300 mm) in a wate bath and wate (50 ml) at the same tempeatue was quickly added. At the designated time (1-15 min), sufficient ice-wate was added to cool the dice, which wee dained, wamed to 25 C and then foce-defomation cuves wee measued on at least IOdice fo Textue Pofile Analvsis (TPA) using an Inston Univesal Testing Machine model 1140 (Inston, High Wycombe, England). Factuability (the foce at the fist significant beak), hadness I (fist compession), hadness 2 (second compession), spinginess, cohesiveness, chewiness and gumminess wee detemined fom the cuves. Each dice was compessed twice to 80% of its oiginal height using a cosshead and chat speed of 100 mmmin-i. Regession and analysis of vaiance wee used to assess esults.

4 The vaious textual paametes wee detemined fom the foce-time cuves, which wee typical of those nomally obtained fo apples9.lo. Factuability, hadness I and hadness 2, significantly (p<o.ooi) deceased with pocessing time and tempeatue fo both vaieties. The enegy in Joules duing the fist compession (aea AI) also significantly (p<o.ooi) deceased with heating time and tempeatue fo Red and Golden Delicious apples. Duing second compession thee was a significant (p<o.ooi) decease in enegy (aea A2) with heating time and tempeatue fo Red Delicious apples, while, fo Golden Delicious apples, pocessing time and tempeatue had no significant effect. Spinginess, a measue of sample elasticity, was found to change with an incease in tempeatue fo both Red (p<o.05) and Golden (p<o.oi) Delicious apples, while no significant changes occued with changing heating time fo eithe cultiva. Anantheswaan et ali2 epoted that in Spigold apples thee wee no significant changes in spinginess with pocessing time and tempeatue, while in the case of Cotland significant (p<o.05) inceases occued with pocessing time. Cohesiveness was inceased significantly with heating tempeatue fo both vaieties, wheeas heating time had no significant effect. Anantheswaan et ali2 found cohesiveness to change with heating tempeatue fo Spigold and Cotland apples; heating time had no significant effect on cohesiveness fo Cotland apples. Gumminess, as a poduct of hadness and cohesiveness, significantly (p<o.ooi) deceased with pocessing time and tempeatue fo both vaieties. Chewiness significantly deceased with tempeatue of heating fo both cultivas. In Golden Delicious apples no significant changes occued with healing time. Simila esults fo chewiness have been obtained by Anantheswaan el a1.12, who epoted no significant changes with pocessing time in Spigold apples. As it has been stated by Anantheswaan et ali2 and showed hee, textual changes in apples duing themal pocessing ae vey complex and vey dependent on vaiety. It should be noted that thee is a diffeent behaviou of stem o oot tissues and fuit tissues. The last showed lage deviation fom the fist-ode kinetic model. Apples showed multi oute textual changes owing to the exceptionally high content of intecellula ai and elative weak o thin cell walls nomally occuing in apple paenchyma" 2J 24 Semilogaithmic plots descibing the change of seveal textual paametes showed two staight lines (Fig. I & 2). So, two fist-ode kinetic mechanisms, as poposed by Huang

5 and Boume 20, can be used to descibe this behaviou. To calculate the ate constants duing the fist few minutes of heating, the gaphical pocedue of Huang and Boune 20 was followed. The linea potion obtained afte polonged heating times (mechanism 2) was extapolated to zeo heating time and the extapolated line subtacted fom the line above it (Fig. 1 & 2). The staight line obtained in this way pemitted the calculation of ate constants fo mechanism 1 of Huang and Boume20. Figlie I: Effect of heating time at 80 C on hadness of Red Delicious apples. (.) expeimental points, (0) points epesenting diffeences betlveen extapolated lille a/l(1 expeimental points.

6 10 Heating Time, min Figue 2: Effect of heating time at 80 C on hadness of Golden Delicious apples. (.) expeimental points. (0) points epesenting diffeences between extapolated line and expeimental points. Long Heating Times The lage dop in the magnitude of most of the textual paametes that occued duing the initial 3 min of heating, is attibuted to mechanism po Changes fo heating times geate than 5 min could be attibuted to mechanism 2 of Huang and Boune 20 The esults obtained fo all textual paametes wee plotted vs heating time to evaluate the possibility of using the fist-ode kinetic model. The linea elationship between log values of factuability, hadness I & 2, and heating time was significant (Table la & Ib) and the fist-ode kinetic model is adequate. Loh and Beene" have stated that

7 factuability is the best available objective paamete fo monitoing deceases in cispness of fesh vegetables duing the heating pocess. Howeve, poblems in its measuement may aise afte polonged heating times and at high tempeatues when a athe smooth gaph without the peak of factuability is obtained by Inston due to loss of cispness and high softness, as well as to inadequate load cell sensitivity of the instument. So, the peak foce epesenting factuability is not easily detectable. When such a poblem is faced anothe paamete must be used fo monitoing of textue degadation. Loh and Beene ll have used chewiness fo pineapple, papaya and zucchini. Anantheswaan et al.12 have used hadness to descibe the themal degadation of apple textue. Indeed, log of hadness I and hadness 2 wee found to decease linealy with heating time (Table Ia & Ib) and ae adequately descibed by the fist-ode model. Hadness can always be easily measued. Hadness 2 measues the esidual amount of hadness left afte the fist compession and is highly elated to hadness 1. Tables Ia & Ib list the decimal eduction times o D values, the ate constants (k) and the coelation coefficients () fo vaious textual paametes. The D values wee calculated fom the slope of log(paamete) vs time cuves and ae included as they ae moe familia to food technologists than the ate constants. The enegy equied duing the fist compession (aea A I) was modelled as a fist-ode pocess, fo both vaieties, and deceased with inceasing tempeatue (Table Ia & lb). Hence, in 'cases whee the foce fo factuability o hadness o the maximum foce duing the compession is difficult to measue, the aea A I (expessed in Joules o abitay units) could be used fo monitoing of textue changes. The enegy duing second compession (aea A2) showed a simila behaviou fo Red Delicious apples, while fo Golden Delicious thee wee no significant changes with heating time and tempeatue. Good coelations wee obtained fo tempeatues highe than 80 C. Gumminess, as a poduct of cohesiveness and hadness I, is geatly affected by changes in hadness and its decease was also modelled as a fist-ode pocess. By the same kinetics, the decease in chewiness, can also be descibed, especially at high pocessing tempeatues (Table Ia & Ib). This last paamete has been aleady used in monitoing textual changes in edible plant tissues 1I.

8 Table Ia D values (min) and ate constants, k (min l) fo Red Delicious apples long heating times. ;; Temp. Kinetic Factuability Hadness I Hadness 2 AI A2 Gumminess Chewiness O( Paamete D 180.0± ± ± ,4± ± ± ± k ±0.00 I 0.015± ± OO7±0.OO ± ± ±0.OOI O.SO 0, D 212.9± ± ,4± ± ± ± ± k 0.011± OO9± ±0.OO4 0.OO9±0.OOI 0.008± ± ± D 88.2± ± ± ± ± ± ± k 0.026± ±0.OOI 0.022± ±0.OO ± ±0.OO ±0.OOI D 85.6±7.7 I 12.7± ± ±17, ± ± ± k 0.027±0.OO ± ±0.00 I 0.023±0.OO ± ±0.OO4 0.OO8±0.OO D 31.7± ± ± ±0.2 65,4± ± ±90.5 m k 0.073± ± ± ±0.00 I 0.035±0.02I ± OO8±0.002 <» z 0 D 21.2± ±0.2 m 34,4± ±1.l 33.1± ± ± k ±0.OO ± ±0.00 I 0.102±0.OO ± ± ±0.014 en en D 7,4± ±0.7 18,4± ± ± ± ±0.3» N 120 k 0.3 I3± ± ± ±0.01O 0.113± ± ±0.OOI 0 en m -l =coelation coefficient, ±=standad deviation»

9 Table Ib D values (min) and ate constants, k (min' I) fo Golden Delicious apples - long heating times. Temp. Kinetic Factuability Hadness I Hadness 2 Al A2 Gumminess Chewiness 0 (I) (I) Paamete C 0 "Tl :> "1J D 313.5i i i i i i iI6.8 "1J 60 k 0.007iO.00 I 0.008iO OO8iO IOiO.OO iO iO iO.005 [T] >-l [T] ><..., D 146.2i23.1 /59.6i iI i i4.6 /38.6i63.5 /88./i47.2 c: ;;0 70 k 0.016iO.OO ± iO.OOl 0.015iO.OO iO I7iO iO.OO8 [T] D Inli i i34.5 4O.0i i32J 196.liI ilO.9 80 k 0.013±0.OO iO OO8iO.OO iO.OO7 0.OO4iO.OO iO iO.00 I D 50.0i ± iI i i i43.9 J42.2i k O.046iO.OIO 0.036iO.OO iO iO iO iO iO D 197i io iO i08 34.li2.1 M.5i3.0 M.4i k 0.117iO iO iO.OO I 0.094iO.OO iO.OO iO.OO iO.OO D 17.0i iO iO iO iOJ 28.6i li k 0.136iOOO iO iO iO.OO iO.OO io.oo iO.OO D 15.9iO.6 208i il iO i i6J 37.4i k 0.145iO.OO io IiO.OO iO.OO iO.OO iO.OO iOOI2 :c =coelatiol1 coefficient. i=standad deviation._--_.. >-l :::: tn ;<l $: :>

10 Fom the slope of the plot of 10g(D) vs heating tempeatue (Fig. 3), the z values (the deges of tempeatue needed fo a 10 times change in D values o in time) fo the change of the above textual paametes wee calculated (Table II). The z values that esultec fom hadness I wee found to be 53.7 and 45.7 C fo Red and Golden Delicious apples espectively. A z value of 42.2 C has been epotedl2 fo Spigold apples, while a lowel value of 24.8 C has been epoted fo Cotland apples. These diffeences show that apple vaiety is one of the dominant factos detemining the changes of textue duing themal pocess. Using vaious TPA paametes a ange of z values between C was calculated (Table II). Activation enegies calculated fom In(k) vs Iff plots fo vaious TPA paametes wee between 30.7±3.8 and 89.3±6.8 kjm-1 (Table II). These values wee within the ange of kjm 1 epoted fo vaious fuits and vegetablesll.12,20 and dy legumes25. Based on hadness I, the activation enegy was 46.1±3.2 and 55.S±6.4 kjm-1 fo Red and Golden Delicious apples espectively. Highe values fo activation enegy have been epoted fo Cotland (11O.95±33.0S kjm-i) and Spigold (65.31 ± kjm-i) apples12 The QIO values I:: '5 u ' 0' ::> <;j > 0. Red Delicious. Golden Delicious D = x 1O-o. 0119T = z-- z = 45.7 C D = x 1O-o.0186T = 0.93 z = 53.7 e Tempeatue, C

11 of the micobial death ae usually geate than 10. Theefoe, high pocessing tempeatues could esult in a themally pocessed fuit with low o minimal degadation in textue. Table II Tempeatue dependence of textue degadation ate long heating times. Textual Paamete Red Delicious Factuability Hadness I Hadness 2 Gumminess Chewiness 42.4±0.8(0.96) 53.7±3.5(0.93) 60.4±9.0(0.93) 41.0±3.7(0.99) 49.0±0.6(0.97) 76.1 ± 1.0(0.85) 54.1±11.9(0.78) 58.6±0.9(0.95) 46.1 ±3.2(0.92) 41.0±6.9(0.92) 61.1±6.1(0.98) 51.1 ± 1.3(0.97) 32.4±0.6(0.84) 46.1 ±2.8(0. 77) Golden Delicious Factuability 41.7±0.6(0.95) 50.6± 1.2(0.82) 1.74 Hadness ±4.5(0.92) 55.8±6.4(0.73) 1.66 Hadness ±0.7(0.93) 53.8± 1.1(0.93) 1.64 AI 50.0± 1.4(0.94) 50.6±1.1 (0.95) 1.58 A2 39.5±9.5(0.88) 89.3±6.8(0.91) 1.79 Gumminess 76.0±6.1 (0.88) 32.8±2.! (0.87) 1.35 Chewiness 79.9±9.8(0.76) 30.8±3.8(0.74) 1.33 Table IlIa & I1Ib list the D values, the ate constants (k) and coelation coefficients () fo textue degadation duing shot heating times. As can be seen the ate constants fo mechanism I wee moe than 16 times geate than the ate fo mechanism 2 (Table [a &

12 N Table IIIa D values (min) and ate constants, k, (min-!) fo Red Delicious apples - shot heating times. Iv Temp. Kinetic Factuability Hadness I Hadness 2 Al A2 Gumminess Chewiness C Paamete D 4.2±01 7.2± ± ± ± ± ± k 0.55± ± ± ± ± ± ± D 2.8± ± ± ± ± ± ± k 0.82± ± ± ± ± ± ± D 2.4± ± ± ± ± ± ± k 0.96± ± ± ± ± ± ± < ;J> z D 1.8± ± ± ± ± ±0.1 1.l±0.2 0 IT1 90 k 1.30± ± ± ± ± ± ± on on ;J> N 0 on ±=standad deviation, =coelation coefficient IT1 -l IT1 ;J>

13 Table IIIb..., :: n ;:0 s:: ;l> D values (min) and ate constants, k, (min l) fo Golden Delicious apples shot heating times. 0Vl Temp. Kinetic Factuability Hadness I Hadness 2 AI A2 Gumminess Chewiness C Paamete ;l> -c -c D 3.SiO i i iO.4 6.2iLO 20.7iO i3.2 n..., 60 k 0.60iO.OS 0.13iO iO iO.04 a.37io.06 a.llia.oo a.2iio.06 n ><..., S a a.99 c ;:0 n D 3.7± ±a.2 4.liO.0 4.6iO.7 6.li1.3 II.SiO iO.S 70 k 0.62iO iO.a3 0.56iO.00 0.SOiO SiO.OS 0.20iO iO D 26i02 l.9io.6 2.5± iO.2 2JiO.2 2.7iO.2 L7±0.3 SO k 0.S9iO.05 l.19io iO.19 L06iO.ll O.99iO.OS 0.S4i ± LOO 0.9S 0.97 D 2.OiO.9 LOiO.l 1.5iO.1 2.liOJ 2.2iO.2 2.6iO.2 LliO.l 90 k LI5iO iO.11 LSOiO.14 LlliO.17 L03iO.10 O.90iOOS 2.06iO S S Vl 0 "TJ i=standad deviation, =coelation coefficient '"w

14 Ib). The z values calculated using D values, wee between 25 and 99 C fo both vaieties. Based on hadness, Golden Delicious apples exhibited a lowe z value than Red Delicious, showing a geate dependence on tempeatue, which is also evident fom the geate activation enegies (Table IV) and QIO values of vs espectively. This could be attibuted to diffeences in flesh stuctue between the two cultivas. Diene et al. 26have epoted that the ate of fimness decease fo Golden Delicious duing matuation was about 70% highe than Red Delicious apples. So, the matuity and condition of apples can affect textual changes. Activation enegies wee within the ange epoted fo vaious fuits and vegetablesll.12.2o and QIO coefficients lowe than The change of othe textual paametes, namely chewiness, gumminess, and enegy duing fist and second compession, was also modelled as a fist-ode pocess and kinetic constants can be obtained by following the above descibed pocedue. Values fo these paametes ae,shown in Table IV. The change of gumminess and chewiness in Golden Delicious apples showed a geate dependence on tempeatue than Red Delicious apples (Table IV). The above data and analysis show that textual changes in apples duing the heating pocess ae vey complex and affected by vaiety. Heating time and tempeatue geatly affect most textual paametes. Heating time did not significantly affect spinginess and cohesiveness in both vaieties, and chewiness in Golden Delicious apples. The ate of change of vaious textual chaacteistics was consistent with two fist-ode kinetic mechanisms as poposed by Huang and Boume20 Duing the fist 2 o 3 minutes of heating thee was a geat decease in vaious textual paametes which confimed what had been epoted by Anantheswaan et al.ll. The ate constants fo mechanism 1 wee at least 16 times geate than those of mechanism 2. Activation enegies wee between 27.7 and 92.6 kjm-1 and QIO values between 1.26 and 2.50 fo both mechanisms. QIO values show that the use of high tempeatue - shot time (HTST) pocesses will esult in a pocessed poduct of bette textue. The z values fo vaious paametes wee between 25.1 and 99.0 C. The z values fo loss of hadness, gumminess and chewiness due to mechanism I in Red Delicious apples was about twice of that in Golden Delicious apples.

15 THERMAL LOSS OF APPLE TEXTURE 25 Table IV Tempeatue dependence of textue degadation ate - shot heating times. Textual z value, C Ea, kjm" QIO Paamete Red Delicious Factuability 83.8±0.8(O.98) 27.2±0.0(0.99) 1.32 Hadness I 45.8±6.5(O.99) 50.5±5.7(0.99) 1.65 Hadness ±71(O.90) 45.4±5.6(0.91) 1.56 Al 76.2±0.9(0.78) 31.0±0.2(0.80) 1.35 A2 48.3±3.9(O.89) 48.5±5.0(0.91) 1.61 Gumminess 42.7± 1.6(0.95) 60.0±2.3(0.96) 1.71 Chewiness 49.7±4.4(0.97) 46. 7±4.1 (0.97) 1.59 Golden Delicious Factuability 99.0±3.6(0.96) 24.2±9.3(0.95) 1.26 Hadness I 25.1 ±4.4(0.97) 92.7± 15.5(0.98) 2.50 Hadness ±5.9(0.96) 74. I± 14.9(0.97) 2.08 AI 65.7±8.4{0.93) 35.0±4.4(O.93) 1.42 A2 57.4±5.1(0.91 ) 4O.3±3.5(0.90) 1.49 Gumminess 29.8±0.9(0.95) 77.9±2.3(0.95) 2.16 Chewiness 25.7±2.0(0.89) 89.5± 14.8(0.89) 2.45 ±=standad deviation, in paenthesis coelation coefficient H KINHTIKH TIn:: YTIOBA0MU::HI: TIll:: YcI>ll:: TnN MHAnN KAT A TH 0EPMIKH EIIESEP ALIA H EvopyllVT] TPA IlVaAUO'T] ~l1topei Vil XPT]O'lJ.!01tOI1')EJEic1') ilea. 't:t]'t:1')~ EJ PilIKt1~ u1to~aejillo't]~'t:t]~uq>t1~ 't:wvilt1awv. 0 XPovo~ Kill 1') EJEPilOKpllO'l1l EJEPilIlvO'1')~il iwvuv O'T[ilIlV't:IKa't:T]v Eu8pllucO't:T['t:Il, 't:t]o'ka,1]p6't:1]'t:il,'t:1')vevepyeiil1tou 1l1tIll't:Ei't:lll KU1:a 1:T[v

16 ltpw1:tlo"ufllti ct]kat to KOflfll(iJO ~Kat CITI~OUO1!OIKIAi ~flt]acilvred Kat Golden Delicious. a xpovo~ etp).ulvo"tl~ OEV EltTlptai; O"Tl).UlvtlKlltl~ fleta~oa.t~ ttl<; EA.aCITlKOtTlta~, O"UVEKtlKOtTlta<;Kal ).UlO"TltIKOtTlta~Kat CITl~ Mo ltolkiaie<;. 01 fle ta~oat~ CITTlVEvtpyElU 1!OUa1!atEItUl Kata tt] O UtEPTlO"Ufl1!iEO"Tl T]tav O"ll).UlvtIKt~ ylu 'llv 1!OlKIA.iaRed, aa.a.a0xi Kal Yla tllv 1!OlKIAiaGolden Delicious. A1!attoUvtUl OE Mo KlVTltlKOiflllxavlO"floi (I & 2) 1!PW1:11~ tc'u, ~ u<pt]~tmv flt]amvkata tll e pfllkt] 1! 1; pyao"ia.01 CITaeEpt~ taxutllt~ Yla va 1! piypa<pouv 01!J. ta~oat~ ttl~ I T]tav touauxlcitov16 <popt~ EKEivTl~Yla to flllxav10"flo 2. H Evtpy la tou flllxavlo"flou EVEPY01!oillcT]~ T],av kjm-1 Kat ylu tl~ Mo. 01 tlfle~ z T]tav C Kat 01 O"UvtEAECITe~QIO Kat ylu tou~ QUoflllXavlc!J.OUs-TholU CITOlXEiafl1tOPOUVva XPllclflO1!0l1l80uv ylu ttl ~EAtiCilcTl tmv 8EpfllKcOVE1!E1; pyamcovtmv flt]amv. I. Bennan, J.G., Jowitt, R., and Mohamed, A.M.A.: Ann. Appl. BioI. 87,12\ (1977)_ 2. Szczesniak, A.S., Bandt, M.A., and Fiedman, H.H.: J. Food Sci. 28, 397 (1963). 3. Boune, M.C.: Food Technol. 19,413 (1965). 4. Bowman, F., Kylen, A.M., and Adam, S.F.: J. Text. Stud. 3, 478 (1972)- 5. Hovath-Mosonyi, M. and Hovath, L.: Acta Alimentaia 11(\), 65 (1982). 6. Abbott, J.A., Watada, A.E., and Massie, D.R.: J. Am. Soc. Hot. Sci. 109(2),221 (1984). 7. Beene, W.M.: J. Text. Stud. 6, 53 (1975). 8. Szczesniak, A.S.: J. Text. Stud. 6, 5 (1975). 9. Boune, M.C.: Food Techno\. 32(7), 62 (1978). 10. Boune, M.C., Kenny, J.F., and Banad, J.: J. Text. Stud. 9,481 (1978). II. Loh, J. and Beene, W.M.: J. Text. Stud. 12,457 (1981). 12. Anantheswaan, R.C., McLellan, M.R., and Boune, M.C.: J. Food Sci. 50, 1136 (1985). 13. Holdswoth, S.D.: In "Effects of Heating on Foodstuffs", R.J. Piestley (Ed.), pp Applied Science Publishes, London (1979). 14. Fletche, S.W.: Tans. ASAE 14(1),14 (1971). 15. Van Woensel, G. and de Baedemaeke, J.: Leben. Wiss.-u.-Techno\. 16, 367 (1983).

17 16. Wothington, J.T. and Yeatman, J.N.: Poc. Am. Soc. Hot. Sci. 92, 739 (1968). 17. Boune, M.C.: Food Techno!. 33,67 (1979). 18. Nicolas, R.C. and Pflug, I.J.: Food Techno!. 16(2), 104 (1962). 19. Paulus, K. and Saguy, I.: J. Food Sci. 45, 239 (1980). 20. Huang, V.T. and Boune, M.C.: J. Text. Stud. 14, 1 (1983). 21. Luie, S. and Klein, J.D.: HotScince 27,36 (1992). 22. Kim, D.M., Smith, N.L., and Lee, c.y.: J. Food Sci. 58, I11I (1993). 23. Van Buen, J.P.: J. Text. Stud. 10, 1 (1979). 24. Van Buen, J.P.: ACS Symp. Se. 310, 190 (1986). 25. Quast, D.C. and dasilva, S.D.: J. Food Sci. 45, 370 (1977). 26. Diene, R.G., Singha, S., and Petit, J.: J. Food Pocess Eng. 6, 85 (1982).