Fruit ripeness and temperature affect friction coefficient of McLemore and Gala apples

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1 Int. Agrophysis, 21, 15, INTERNATIONAL Agrophysis Fruit ripeness nd temperture ffet frition oeffiient of MLemore nd Gl pples C. Puhlski 1 *, G.H. Brusewitz 2 1 Agriulturl University of Crow, Deprtment of Agriulturl Prodution Tehnology, Æwikliñskiej 2, Rzeszów, Polnd 2 Deprtment of Biosystems nd Agriulturl Engineering, Oklhom Stte University, Stillwter, OK, 7478, USA Reeived Novemer 2, 1999; epted Jnury 25, 2 A s t r t.theojetive of this study ws to determine the influene of pple flesh temperture nd ripeness on the stti nd dynmi oeffiients of frition. Two pple ultivrs with two different degrees of ripeness were hnd piked from trees in ommeril orhrd nd pled in the environments with tempertures of either 6, 12, 18, 24 or 3 C. Frition tests were performed on whole pples ginst msonite, ruer, plsti nd rdord pper surfes. Temperture nd pple ripeness hd signifint effet on the stti nd dynmi oeffiients of frition for oth ultivrs. More ripe pples hd higher frition oeffiients thn less ripe pples. Keywords:frition, mesurement, ripeness, temperture, pple INTRODUCTION Frition of produts ginst mhine prts n use mehnil dmge to fruit nd vegetles, prtiulrly during hrvesting nd hndling. Coeffiient of frition is n importnt prmeter in the optimum design of hrvesting nd hndling equipment. Two importnt ftors ffeting the hndling ehviour of fresh fruit nd their qulity re fruit ripeness nd temperture. Hyde nd Ingle (1968) found tht ruise size inresed with inresing mturity nd deresed with inresing storge time. Sltveit (1984) reported tht ruise suseptiility inresed with inresing fruit temperture, ut Shoorl nd Holt (1978) found the opposite effet. Bjem et l. (1998) found tht lower temperture nd higher strin rte redued filure properties of potto tuer tissue. Bourne (1982) stted tht firmness of most fruit nd vegetles showed derese with n inresing temperture over the rnge from to 45 C. Puhlski nd Brusewitz (1996) showed tht the effet of the mesurement dte on the frition oeffiient ws signifint with tendeny to derese with time for wtermelon. The ojetive of this work ws to determine the influene of fruit ripeness nd temperture on the stti nd dynmi oeffiients of frition of pples ginst different sliding surfes. MATERIALS AND METHODS Two pple ultivrs, Gl nd MLemore were tested. Their hrteristis ws presented in Tle 1. They were grown in ommeril orhrd in the estern Oklhom nd hrvested on 24th July (MLemore) nd 15th August (Gl). The pples were hnd piked t two different stges of ripeness, i.e., MLemore - s unripe nd ripe fruit indging y their firmness nd olour nd Gl - from sides of the tree more nd less exposed to the sunlight referred to s south nd north prts of the tree. Fruit were sorted y mss nd size to otin more uniform groups. The fruit were put into plsti gs (to retin moisture) nd stored in the hmers with tempertures t either 6, 12, 18 or 3 C. Additionl fruit were left in the room t 24 C. The pples were tested just fter hrvest (for oth ultivrs) nd on three test dtes within 2 dys of storge (first - efore storge, seond fter 1 dys nd lst t the end of storge of Gl fruit). Fruit firmness ws mesured with n Effegi fruit pressure tester using 11.1 mm dimeter tip. The devie of Puhlski nd Brusewitz (1996) ws used to mesure frition oeffiients ginst vrious sliding surfes (Fig. 1). The min omponents of the devie were: sttionry smple holder, *Corresponding uthor 21 Institute of Agrophysis, Polish Ademy of Sienes

2 11 C. PUCHALSKI nd G.H. BRUSEWITZ Tle 1.Apple hrteristis (n=24) Ftor Weight (g) Min Dimension (mm) Mx Moisture ontent (%) Firmness (N) M. S.D. M. S.D. M. S.D. M. S.D. M. S.D. MLemore Unripe Ripe Gl North South M. - men, S.D. - stndrd devition. Arsive surfe holder w/ erings Cle onnetion to Instron Arsive surfe Adjustle jws Snd g se Smple Pivot rm Frme Counter weight Fig. 1. The devie for testing frition. horizontlly moving frition surfe onneted to the Instron s rosshed, dt quisition system inluding personl omputer to mesure the fritionl fore. The smple holder hs two independently djustle jws tht rigidly hold the smple nd lso pplies the required norml fore with pivoting rm nd ounter weight. A rigid, flt frition surfe of.1 m wide nd.6 m long ws olted to the underside of pulling plte supported y preision ril nd liner ering to minimise frition. The pulling fore ws supplied y the Instron s rosshed with non-strething 1.-mm dimeter steel le. Testing ws done t onstnt norml fore of 17 N nd sliding speed of 4.17 mm s -1 over trvelling distne of 4 mm ginst msonite nd plsti surfes. Stti nd dynmi oeffiients of frition were lulted on the sis of the pek stti fore nd n verge dynmi fore (Puhlski nd Brusewitz, 1996). Dt on the individul ftors were sujeted to the nlysis of vrine (ANOVA) nd the mens were seprted y the Dunn s multiple rnge test. RESULTS AND DISCUSSION Effet of fruit temperture An nlysis of vrine (ANOVA) showed signifint effet (t p <.1) of fruit temperture on the stti nd dynmi oeffiients of frition for oth ultivrs. Generlly, the stti oeffiient of frition deresed with n inrese in

3 FRICTION COEFFICIENT OF APPLES 111 fruit temperture from 6 to 24 C, exept on plsti for the MLemore (Fig. 2). These dereses in the stti oeffiient of frition were 14 to 26% of the initil vlue. An inrese in fruit temperture from 6 to 24 C proly used smoothing of the fruit surfe; hene, derese in the oeffiient of frition. Roy et l. (1994), using snning eletron mirosopy, reveled suh smoothing of pple surfe with no deep rks with het tretment. Figure 2 shows lso the effet of fruit temperture on the dynmi oeffiient of frition relted to the ultivr, nd sliding surfe. The dynmi oeffiient of frition deresed s the temperture ws rising from 12 to 24 C on oth surfes for the unripe Gl fruit. However, for the ripe MLemore, this tendeny ws opposite. For the plsti very smooth surfe, hnges in the dynmi oeffiient of frition were strongly ffeted y ultivr differenes t temperture elow 18 C. It mens tht proly the physil nd hemil proesses involved during ontt with this surfe hnged ehviour of the smples. Effet of ripeness of MLemore Figure 3 shows the effet of ripeness on the stti nd dynmi oeffiients of frition t vrious fruit tempertures nd sliding surfes. Generlly, ripe fruit (with firmness of 37.9 N) exhiit higher oeffiients of frition thn unripe ones (firmness, 71.3 N) t ll fruit tempertures, exept t 3 C on plsti for oth oeffiients. Proly, s pples ripen, there is hnge in the fruit surfe wx, whih ffets the mterils in ontt during the frition test. It ws oserved y Roy et l. (1994) for pple nd Corey et l. (1988) for wtermelon. A signifint differene of 5-32% in oeffiient of frition etween ripe nd unripe fruit ws evident t 6 nd 12 C (for oth oeffiients) on plsti nd 6 nd 18 C (for the stti nd dynmi oeffiients, respetively) on msonite. The iggest differenes of up to 4% in the dynmi oeffiient of frition etween ripe nd unripe fruit were noted t 3 C on msonite. Stti oeffiient of frition,46, Msonite Serie1 Gl Serie3 MLemore Plsti Gl MLemore d Dymmi oeffiient of frition Msonite Temperture ( o C) Serie1 Gl Serie3 MLemore 12 Fig. 2. Effet of fruit temperture on the stti nd dynmi oeffiients of frition ginst msonite nd plsti surfes for oth ultivrs. Different letters represent signifint differene in the men vlues, within the urve, y the Dunn's multiple rnge test t the 5% level Plsti Gl MLemore Temperture ( o C)

4 112 C. PUCHALSKI nd G.H. BRUSEWITZ ripe unripe Stti oeffiient of frition,4 Msonite Serie1 unripe ripe Serie2 Stti oeffiient of frition Plsti Seri unr Seri rip Fruit temperture, C ripe unripe Fruit temperture, C Dynmi oeffiient of frition,4 Msonite Serie1 ripe Serie2 unripe Dynmi oeffiient of frition Plsti Seri1 Seri2 Fruit Fruit temperture, ( o C) C Fruit temperture ( o C) Fig. 3. Effet of ripeness on the stti nd dynmi oeffiients of frition t vrious tempertures ginst msonite nd plsti for MLemore. Different letters represent signifint differene in the men vlues, within ripe nd unripe, y the Dunn's multiple rnge test t the 5% level. Effet of pple lotion on tree for Gl Figure 4 presents the effet of pple lotion on the tree on the oeffiient of frition for the fruit stored t 6 to 3 C. Generlly, the stti nd dynmi frition oeffiients of pples from the south side of trees were higher thn those from the north side. Differenes in the oeffiients of frition etween the smples tken from the south nd north sides of trees were from 4.3 to 37% nd were more evident t 12 C. Apples tken from the north side of trees hd higher firmness (Tle 1) nd were less exposed to sunlight thn those from the south side of trees. Effet of storge dys of Gl Figure 5 shows the effet of storge length on the stti nd dynmi oeffiients of frition ginst msonite nd plsti surfes. Stti nd dynmi oeffiients of frition inresed signifintly with storge length, exept for the stti frition oeffiient on plsti. It grees with wht hs een found for the ripe nd unripe MLemore fruit. The effet of storge time ws more pronouned for the dynmi thn for the stti oeffiient of frition. Liner reltionships fit stti nd dynmi oeffiients of frition versus storge dys well (Tle 2). However, for the stti oeffiient on the plsti surfe, the seond degree polynomils were neessry to get good fit of the dt.

5 FRICTION COEFFICIENT OF APPLES 113 North South Msonite Stti oeffiient of frition,5,,5, Fruit temperture ( o C) Fruit temperture ( o C) Dynmi oeffiient of frition Stti oeffiient of frition, North South Fruit temperture ( o C) Plsti Dynmi oeffiient of frition, Fruit temperture ( o C) Fig. 4. Effet of pple lotion on tree on the stti nd dynmi oeffiients of frition ginst msonite nd plsti for Gl. Different letters represent signifint differene in the men vlues, within North nd South, y the Dunn s multiple rnge test t the 5 % level. Stti oeffiient of frition Msonite Plsti Storge dys Dynmi oeffiient of frition,5 Msonite Plsti Storge dys Fig. 5. Effet of storge dys on the stti nd dynmi oeffiients of frition on the msonite nd plsti surfes for Gl. Tle 2.Reltionship etween oeffiients of frition nd storge time (x = dys) for two sliding surfes ginst Gl Coeffiient of frition Sliding surfe Regression eqution R 2 Stti Msonite Plsti.59x x x Dynmi Msonite Plsti.81x x

6 114 C. PUCHALSKI nd G.H. BRUSEWITZ CONCLUSIONS 1. Some ftors, suh s ripeness, temperture nd pple lotion on the tree, hd signifint effets on oth stti nd dynmi oeffiients of frition. 2. Stti nd dynmi oeffiients inresed from 5 to 4% with fruit ripening, depending on the sliding surfe nd fruit temperture. 3. Stti oeffiient of frition signifintly deresed with higher fruit temperture (from 6 to 24 C), exept for plsti ginst MLemore. 4. Generlly, the stti nd dynmi oeffiients of frition of pples from the side of the tree whih is more exposed to sunlight (south prt of trees), were higher thn those from the opposite side. 5. As pples of Gl were stored for 2 dys fter hrvest, their dynmi frition oeffiients inresed s muh s 53% on the msonite nd plsti surfes. REFERENCES Bjem R.W., Hyde G.M., nd Britelle A.L., Temperture nd strin rte effets on the dynmi filure properties of potto tuer tissue. Trns. ASAE, 41(3), Bourne M.C., Effet of temperture on firmness of rw fruits nd vegetles. J. Food Si., 47, Corey K.A., Shlimme D.V., nd Chney N.A., Chnges in epiutiulr wx on wtermelon fruits during ripening. Hort. Si., 23(4), Hyde J.F. nd Ingle M., Size of pple ruises s ffeted y ultivr, mturity nd time in storge. Pro. Amerin Soiety of Hortiulturl Siene, 92, Puhlski C. nd Brusewitz G.H., Coeffiient of frition of wtermelon. Trns. ASAE, 39(2), Roy S., Conwy W.S., Wtd A.E., Sms C.E., Ere E.F., nd Wergin W.P., Het tretment ffets epiutiulr wx struture nd posthrvest lium uptke in Golden Deliious pples. Hort. Si., 29(9), Sltveit M.E., Effet of temperture on firmness nd ruising of Strkrimson Deliious nd Golden Deliious pples. Hort. Si., 19(4), Shoorl D. nd Holt J.E., The effets of storge time nd temperture on the ruising of Jonthn, Deliious nd Grnny Smith pples. J. Texture Studies, 8,