Optimiranje i modeliranje procesa sušenja voća i povrća (CROSBI ID 345096)
Ocjenski rad | doktorska disertacija
Podaci o odgovornosti
Velić, Darko
Bilić, Mate
hrvatski
Optimiranje i modeliranje procesa sušenja voća i povrća
Provedeno je optimiranje i modeliranje procesa sušenja voća i povrća na osnovi praćenja kinetike sušenja i pokazatelja o očuvanju nutritivnih i organoleptičkih svojstava. Kinetika sušenja odabranih uzoraka voća i povrća determinirana je kontinuiranim praćenjem: promjene mase uzoraka, temperaturnog profila materijala i medija za sušenje, te profila vlage. Istraživanje je provedeno primjenom termogravimetrijske tehnike s laboratorijskim uređajima koji su u svrhu ovog istraživanja posebno nadograđeni i opremljeni: tunelski sušionik (TD), vakuum sušionik (VK), infracrveni sušionik (IC), te sušionik za sušenje s fluidiziranim slojem (FBD). U svrhu ubrzavanja kinetike sušenja, sprečavanja enzimske aktivnosti kao i neenzimskih promjena tijekom procesa sušenja, primijenjeni su različiti fizikalno-kemijski postupci prethodne obrade uzoraka, te su ovisno o metodi sušenja predložena odgovarajuća rješenja. Za procjenu pojedine metode, te za praćenje utjecaja procesnih parametara na svojstva osušenih uzoraka, primijenjene su standardne analitičke metode termogravimetrija, rehidratacija, kolorimetrija, volumetrija, te tekućinska kromatografija visokog učinka (HPLC). Modeliranjem eksperimentalnih podataka promjene vlažnosti za uzorke marelice i jabuke sušene u tunelskom sušioniku pri različitim temperaturama sušenja (50 °C, 60 °C, 70 °C i 80 °C) i brzinama strujanja zraka (1, 4 m s-1 ; 2, 1 m s-1 ; 2, 8 m s-1) utvrđeno je da najbolje slaganje s eksperimentalnim podacima daje Midilli i Kucukov model. Izrađeni su i novi poluempirijski modeli koji mogu poslužiti za simuliranje kinetike sušenja uzoraka marelice i jabuke unutar granica ispitanih procesnih parametara, temperature i brzine strujanja zraka. Ispitan je utjecaj temperature sušenja i različitih metoda sušenja na sadržaj β -karotena u uzorcima mrkve. Najmanja degradacija  – karotena izmjerena je u neobrađenim uzorcima mrkve koji su sušeni u tunelskom sušioniku pri temperaturi sušenja 70 °C i brzini strujanja zraka 2, 8 m s-1. Najveći rehidratacijski omjer izmjeren je kod uzoraka marelice koje su sušene u tunelskom sušioniku pri temperaturi 80 °C i brzini strujanja zraka 1, 4 m s-1. Najbolji rezultati (visoka vrijednost rehidratacijskog omjera i najmanja ukupna promjena boje) dobiveni su u slučaju sušenja uzoraka jabuke u tunelskom sušioniku (TD) pri temperaturi sušenja 50 °C, te kod sušenja uzoraka mrkve i peršina u tunelskom sušioniku (TD) pri temperaturi sušenja 60 °C i brzini strujanja zraka od 2, 8 m s-1. Dobivena je i ovisnost utjecaja različitih postupaka prethodne obrade na kinetiku sušenja i parametre kvalitete osušenih proizvoda.
modeliranje; optimiranje; kinetika sušenja; voće; povrće; prethodna obrada; poluempirijski modeli
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engleski
Optimisation and modelling of fruits and vegetables drying procesess
The influence of the process parameters on the drying kinetics of different food products, fruits and vegetables, using different dryers was investigated. The dehydration kinetics of samples was determined by continues recording of mass changes, temperature profile of material and drying media as well as moisture profile using computer process control. To speed up the dehydration kinetics, and to eliminate the enzymatic browning activity as well as non enzymatic changes during dehydration process different physical and chemical procedures of samples pre-treatment were applied, depending on method used, related technical solutions were proposed. Evaluation of each method and the influence of the process parameters on the properties of dried materials were performed using standard analytical methods: thermo-gravimetric, rehydration, colorimetric, volumetric and high pressure liquid chromatography – HPLC. The changes in colour and volume as well as rehydration rate (reconstitution characteristic) for each of the drying methods were studied. After defining the optimal drying process parameters, different pre-treatment methods were investigated. The existing mathematical models (thin-layer equations) were tested and new semi-empirical models that describe drying processes of fruits and vegetables using different driers were defined. When modelling the experimental data for apricot and apple samples which were dried in the tunnel dryer at drying temperatures of 50 °C, 60 °C, 70 °C and 80 °C and air flow velocities of 1,4 m s-1; 2,1 m s-1 and 2,8 m s-1, Midilli–Kucuk model proved to be the best and showed a good agreement with the experimental data. A new semi-empirical models were developed for the simulation of apricot and apple drying at temperature range 50–80 °C and velocity range 1,4–2,8 m s-1 of drying air. Furthermore, the influence of the drying temperature and drying methods on the content of the main nutritive components was studied. The degradation of β – carotene was the smallest when non-treated carrot samples were dried in the tunnel dryer (TD) at temperature of 70 °C and at airflow velocities of 2,8 m s-1. The highest rehydration ratio was observed when apricot samples were dried at temperature of 80 °C and airflow velocities of 1,4 m s-1. The best results (good rehydration ratio and colour) were achieved when apple samples were dried in the tunnel dryer (TD) at temperature of 50 °C. As for carrot and parsley root samples, the best results were achieved when drying in the tunnel dryer (TD) at temperature of 60 °C and airflow velocities of 2,8 m s-1. The influence of the different sample pre-treatment procedures on the drying kinetics and the properties of dried materials was determined.
modelling; optimisation; drying kinetics; fruits; vegetables; pre-treatment; semi-empirical models
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Podaci o izdanju
155
17.07.2006.
obranjeno
109:702465
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