<p>Važnost istraživanja fizičkih osobina ogleda se u tome, što su neke od tih osobina prvo što<br />se uočava na sušenom voću. Druge fizičke osobine spoznaju se tokom konzumiranja. Osim<br />toga, fizičke osobine su i od značaja prilikom projektovanja opreme za preradu<br />poljoprivrednih proizvoda. Predmet istraživanja doktorske disertacije su promene fizičkih<br />osobina dunje tokom osmotskog i konvektivnog sušenja. Istraživane su promene sledećih<br />osobina: vlažnosti, zapremine, mehaničkih osobina i boje. Kao dodatak osnovnim merenjima<br />obavljene su hemijska i senzorska analiza finalnog proizvoda. Eksperiment osmotskog<br />sušenja obavljen je kao dvofaktorni. Faktori eksperimenta su temperatura i koncentracija<br />osmotskog rastvora. U eksperimentu je korišćena dunja sorte leskovačka. Ovu sortu odlikuje<br />prijatna aroma, oblik i dimenzije pogodne za sušenje.<br />Disperzionom analizom rezultata merenja fizičkih osobina tokom eksperimenta<br />osmotskog sušenja potvrđeno je da izabrani nivoi temperature i koncentracije osmotskog<br />rastvora utiču na promenu vlažnosti dunje tokom 180 minuta osmotskog sušenja. U slučaju<br />povećanja mase suve materije disperzionom analizom potvrđen je statistički značajan uticaj<br />koncentracije i interakcije koncentracije i temperature na promenu ispitivane veličine.<br />Najintenzivnije promene vlažnosti i povećanja suve materije izmerene su u prvih 20 minuta<br />osmotskog sušenja.<br />Promena oblika dunje u formi kocke, do kojih dolazi tokom osmotskog sušenja je<br />anizotropna. Razlog anizotropnog skupljanja tkiva može biti orijentacija vlakana i<br />nehomogena struktura materijala. Promena zapremine izražena je zapreminskim skupljanjem<br />SV. Izvedena je jednačina kojom je utvrđena zavisnost promene zapremine od količine<br />razmenjene materije tokom osmotskog sušenja. Najveća promena zapremine izmerena je pri<br />osmotskom sušenju pri najvišim vrednostima temperature i koncentracije osmotskog<br />rastvora.<br />Mehaničke osobine dunje tokom osmotskog sušenja predstavljene su sa dva pokazatelja,<br />otpornošću na razaranje i modulom elastičnosti. Otpornost na razaranje je u ovoj tezi<br />originalno predstavljena parametrom f. Ovaj parameter predstvalja relativnu promenu sile<br />razaranja tokom osmotskog sušenja. Disperzionom analizom utvrđen je uticaj temperature<br />osmotskog rastvora na mehaničke osobine dunje. Osmotski rastvor temeperature 60oC<br />izaziva omekšavanje tkiva dunje. Međutim, omekšavanje tkiva dunje pozitivno utiče na<br />čvrstoću krajnjeg proizvoda. Kao drugi pokazatelj mehaničkih osobina upotrebljen je modul<br />elastičnosti. Promene modula elastičnosti slične su promenama f parametra. Na osnovu<br />promena oba pokazatelja mogu se doneti isti zaključci o uticaju faktora eksperimenta na<br />mehaničke osobine tkiva dunje.<br />Tkivo dunje je izloženo vazduhu tokom konvektivnog sušenja intenzivno menja boju. U<br />eksperimentu je upotrebljen sumpordioksid kao zaštita od tamnjenja tkiva. Ukupna promena<br />boje najveća je na uzorcima dunje koji su sušeni rastvorom koncentracije 65oBx. Međutim,<br />tokom konvektivnog sušenja ističe se pozitivan uticaj ovog tretmana na promenu boje dunje.<br />Veća količina saharoze koja se zadržava na površini uzoraka dunje predstavlja barijeru<br />između između materijala i vazduha i spračava tamnjenje tkiva.<br />Regresionom analizom rezultata merenja promene vlažnosti, zapremine i boje pronađeni<br />su empirijski modeli koji opisuju merene veličine tokom osmotskog sušenja. Jednačine<br />odabrane za modelovanje promene vlažnosti proširene su uticajnim faktorima u<br />bezdimenzionalnom obliku. Proširenjem matematičkih modela stiče se njihova univerzalnost<br />u opsegu istraživanih vrednosti temperature i koncentracije osmotskog rastvora. Primenjeni<br />modeli mogu se uspešno koristiti za predviđanje svih merenih veličina. Uspešnost modela<br />potvrđena je visokim vrednostima koeficijenta korelacije i niskim vrednostima srednje<br />procentualne greške.<br />Senzorskim analizama obavljenim panelnim ispitivanjem, uzorci tretirani osmotskim<br />rastvorom ocenjeni su kao kvalitetniji od onih koji su samo konvektivno osušeni.<br />Poređenjem rezultata kvantitativnih i kvalitativnih analiza može se zaključiti da osmotsko<br />sušenje kao predtretman konvektivnom sušenju pozitivno utiče na kvalitet sušene dunje kao<br />finalnog proizvoda.<br /> </p> / <p>The importance of researching physical properties lies in the fact that some of these<br />properties are what we first notice about dried fruit. Other physical properties are<br />experienced during consumption. Moreover, physical properties are also important when<br />designing equipment for processing agricultural products. The subject of the research in this<br />doctoral dissertation is changes in physical properties of quince during osmotic and<br />convective drying. The investigation included changes in the following properties: moisture,<br />volume, mechanical properties and colour. Apart from the basic measurements, the research<br />also included chemical and sensory analyses of the final product. The experiment of osmotic<br />drying was performed as a two-factor experiment, while factors were the temperature and the<br />concentration of osmotic solution. The variety of quince used in the experiment was<br />“Leksovačka”, which is a variety with a pleasant aroma, and the shape and dimensions<br />suitable for drying.<br />Dispersion analysis of the measured results in the experiment of osmotic drying showed<br />that the temperature and concentration of osmotic solution affect the changes in moisture of<br />quince during 180 minutes of osmotic drying. In the case of the increased mass of dry matter,<br />analysis of variance pointed to statistically significant effect of concentration and interaction<br />of concentration and temperature on the change in the examined size. The most intense<br />changes in moisture and increase of dry matter were measured in the first 20 minutes of<br />osmotic drying.<br />The change of the shape of quince into the shape of a cube, which occurs during osmotic<br />drying, is anisotropic. The reason of anisotropic shrinkage of tissue can be fibre orientation<br />and inhomogeneous structure of the material. The volume change is expressed in volumetric<br />shrinkage SV. The equation derived was used to determine the dependence of the change in<br />volume on the amount of the matter exchanged during osmotic drying. The greatest change<br />in volume was measured during osmotic drying at the highest values of temperature and the<br />highest values of concentration of osmotic solution.<br />Mechanical properties of quince during osmotic drying were represented by two<br />indicators: resistance to rupture and modulus of elasticity. Resistance to rupture in this thesis<br />was originally presented by the parameter f. This parameter represents a relative difference of<br />force of rupture. Dispersion analysis determined the effect of the temperature of osmotic<br />solution on mechanical properties of quince. The solution temperature of 60oC causes<br />softening of the quince tissue. However, softening of the tissue has positive effects on<br />firmness of the final product. The other indicator of mechanical properties was modulus of<br />elasticity. The changes in the modulus of elasticity are similar to the changes of the<br />parameter f. The changes in both indicators lead to the same conclusions about the impact of<br />the factors of the experiment on the mechanical properties of quince tissue.<br />Quince tissue exposed to air changes its colour intensely. In this experiment, sulphur<br />dioxide is used as protection against darkening of the tissue. The total colour change was the<br />greatest in the quince samples dried using a solution with the concentration of 65oBx.<br />However, during convective drying one can see the positive impact of this treatment on the<br />colour change in quince. A larger amount of saccharose which is retained on the surface of<br />the samples acts as a barrier between the material and the air, preventing darkening of the<br />tissue.<br />Regression analysis of the measured results of the changes in moisture, volume and<br />colour, generated empirical models that describe the measured values during osmotic drying.<br />The equations selected for modelling of moisture changes were extended to include<br />influential factors in dimensionless form. What is achieved by extending the mathematical<br />models is universality of the models in the range of the investigated values of temperature<br />and concentration of osmotic solution. The used models can be successfully applied for<br />prediction of all of the measured values. The successfulness of the model is confirmed by<br />high values of the correlation coefficient and low values of the mean percentage error.<br />Sensory analyses performed using panel testing showed that the samples treated with osmotic<br />solution were evaluated to be of higher quality than the samples that were only convectively<br />dried. By comparing the results of quantitative and qualitative analyses, it can be concluded<br />that osmotic drying, as a pre-treatment to convective drying, positively affects the quality of<br />dried quince as a final product.</p>
| Identifer | oai:union.ndltd.org:uns.ac.rs/oai:CRISUNS:(BISIS)94094 |
| Date | 19 May 2015 |
| Creators | Radojčin Milivoj |
| Contributors | Babić Mirko, Pavkov Ivan, Bajkin Anđelko, Dimitrijević Aleksandra, Bikic Sinisa |
| Publisher | Univerzitet u Novom Sadu, Poljoprivredni fakultet u Novom Sadu, University of Novi Sad, Faculty of Agriculture at Novi Sad |
| Source Sets | University of Novi Sad |
| Language | Serbian |
| Detected Language | Unknown |
| Type | PhD thesis |
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