The Influence of Rehydration on Breakage Susceptibility of Corn Kernels Hybrid Bc 492

Lom kukuruznog zrna moguće je djelotvorno smanjiti primjenom postupka rehidracije. U ovim istraživanjima primjenjivane su dvije rehidracijske metode: dodavanjem destilirane vode uzorcima kukuruznog zrna vlažnosti 10 %, i miješanjem zrnja kukuruza hibrida Bc 492 dviju vlažnosti 10 i 18 %. Uzorci su rehidrirani, jednom ili drugom metodom, do vlažnosti od 14,5 %. Vrijeme potrebno za kondicioniranje primjenom metode dodavanja vode bilo je oko 16 sati, dok je to vrijeme za metodu miješanjem iznosilo oko 72 sata nakon miješanja. Promjena vrijednosti loma varirala je u odnosu na primjenjivanu rehidracijsku metodu, kao i na količinu vode dodane u jednom rehidracijskom koraku. Sama uspješnost rehidracijske metode dodavanjem destilirane vode bila je ograničena porastom unutarnjih naprezanja u zrnu. Minimalni porast unutarnjih naprezanja postignut je primjenom postupnog dodavanja vode u koracima do 1,5 % porasta vlažnosti zrna. Granica loma revalvirala je s rehidracijskom metodom s početnom vlagom i brojem rehidracijskih koraka. Lom za miješane uzorke bio je općenito manji, i kretao se u rasponu od 3,0 do 3,3 %, dok je za kukuruzno zrno rehidrirano dodavanjem destilirane vode lom bio u rasponu od 3,3 do 6,3 %.Rehydrating corn kernels hybrid Bc 492 from 10% to 14,5% moisture content by adding distilled water or by mixing with higher moisture content corn kernels was effective in reducing breakage susceptibility. The extent to wich breakage susceptibility was reduced varied with the rehydration method and the amount of moisture added in a single rehydration step. Approximately 16 h were required for the rehydration process when adding water, and about 72 h for mixing samples. Mixing was a more effective rehydration method, resulting in breakage susceptibility levels no higher than for a control samples dried to 14,5%. The effectiveness of rehydrating by adding distilled water was limited by stress cracks which developed during the rehydration process. Stress crack developed was minimized by rehydrating in moisture content steps of 1,5% or less when adding distilled water. Brekage susceptibility for the mixing samples was generally lower than for the corn kernels rehydrated by water addition. Values for the mixing samples ranged from 3,0 to 3,5%. This compares to a range of 3,3 to 6,3 for the water addition samples

Breakage of Corn Kernel on an Vertical Elevator Transportation

Ispitivanja mehaničkog oštećivanja zrna kukuruza provedena su na elevatoru, transportnom sredstvu okomitog transporta. Rad predstavlja usporedbu dinamičke otpornosti zrna kukuruza hibrida OSSK 552 na ulazu i izlazu iz elevatora tijekom transporta. Deklarirani kapacitet elevatora bio je 64 m3/h, volumen pojedine vjedrice iznosio je 2,1 dm3, a na traci je bilo pričvršćeno 360 vjedrica. Broj okreta reduktora, a samim time i pogonske glave elevatora bio je 80 min-1. Utvrđeno je da se tijekom navedenog transporta povećava udio loma, no ne u istom iznosu. Ispitivanja oštećivanja su obavljana na uzorcima različite vlažnosti, podijeljenih u 4 grupe i to: 28-30 %;23-25 %;17-19 % i 11-13 %. Kod vlažnosti materijala 29 %, izlazni lom bio je za 1,33 % veći od ulaznog. Ako se iskaže u relativnim odnosima onda je to razlika od 19,32 %. Kod vlažnosti kukuruznog zrna od 23 %, ta je razlika iznosila 1,03 %, relativno 22,94 %, dok je kod vlažnosti materijala 18 %, razlika bila 2,34 %, relativno 30,51 %. Na najsuhljem uzorku materijala od 12 %, ta je razlika iznosila 2,57 %, u relativnim iznosima čak 94,83%.Examining breakage of corn kernel on an elevator, the means for vertical transportation, the paper compares the mechanical resistance of the OSSK 552 maize hybrid when entering and leaving the elevator. The declared capacity of the elevator was 64 m3/h, the volume of each of the 360 buckets contained 2.1 dm3, the number of turns of the reductor and consequently of the upper drive pulley of the elevator amounted to 80 min-1. It was established that during the mentioned transportation the breakage had increased, but not in same amount. The damage was examined on samples of different moisture content distributed into four groups: 28-30 %;23-25 %;17 19 % and 11-13 %. In the 29 % moisture content of the material the end of breakage was 1,33% higher than the beginning one. If expressed relatively, this is a difference of 19,32 %. In the moisture of the corn kernel of 23 %, this difference amounted to 1,03 %, relatively 22,94 %, while in the moisture of the material of 18 %, the difference was 2,34 %, relatively 30,51 %. In the driest sample of the material, of 12 %, the difference amounted to 2,57 %, relatively even 24,83 %

Thin-layer drying of mint (Mentha piperita) leaves

List paprene metvice (Mentha piperita) bio je sušen u elemen-tarnom (tankom) sloju u sušnici na temperaturama zraka raspona od 35 do 60 °C. Porast temperature radnog medija (zraka) značajno je smanjio vrijeme sušenja lista. Podaci o sušenju lista paprene metvice analizirani su i u pogledu difuzije u periodima sušenja.The thin-layer drying of mint leaves for a temperature range of 35–60 °C was determined in a (cabinet) dryer. The increase in air temperature significantly reduced the drying time of the mint leaves. Drying data of this material were analysed to obtain diffusivity values from the falling rate-drying period