Nikola Pšenica and Nobel laureate Ružička

U radu se govori o životu i radu vukovaraca Nikole Pšenice i Nobelovca Ružičk

Utjecaj sušenja, prešanja i antioksidansa na prinos i oksidativnu stabilnost hladno prešanih ulja

Investigated were the influence of drying and pressing parameters of rapeseed, sunflower, and safflower seeds on oil yield, as well as antioxidant addition on the oxidative stability of cold pressed oils. The parameters of the oilseeds and cold pressed oils quality (moisture content, iodine value, saponification value, peroxide value, free fatty acids, and insoluble impurities content) were determined using standard methods. In terms of oxidative stability, rosemary, green tea, and pomegranate extracts were used as natural antioxidants, and propyl gallate was used as synthetic antioxidant. The results showed that the moisture content of the oilseeds, as well as nozzle size and electromotor frequency of the press had an effect on the yield of cold pressed oil. By reducing the nozzle size and electromotor frequency, the volume of produced cold pressed oil increased. Rosemary extract effectively increased the oxidative stability of sunflower and safflower oils, and green tea extract increased the stability of rapeseed oil. Greater stabilisation of the tested oils was achieved with the addition of 0.4% of natural antioxidants compared to the addition of 0.2 %. The synthetic antioxidant, propyl gallate, failed to stabilise safflower oil, and unlike the natural antioxidants, it was less protective for rapeseed and sunflower oil.U ovom radu istražen je utjecaj parametara sušenja (temperatura) i prešanja (veličina otvora glave preše, frekvencija elektromotora) sjemena uljane repice, suncokreta i šafranike na prinos ulja te dodatka antioksidansa (prirodnog, sintetičkog) na oksidacijsku stabilnost hladno prešanih ulja. Standardnim metodama određeni su parametri kvalitete uljarica (sadržaj vlage) i hladno prešanih ulja (jodni broj, saponifikacijski broj, peroksidni broj, slobodne masne kiseline, vlaga i sadržaj netopljivih nečistoća). Što se tiče oksidacijske stabilnosti, kao prirodni antioksidansi upotrijebljeni su ekstrakti ružmarina, zelenog čaja i nara, a kao sintetski propil galat. Rezultati su pokazali da vlažnost uljarica te veličina otvora glave preše i frekvencija elektromotora utječu na iskorištenje hladno prešanog ulja. Smanjenjem veličine otvora glave preše i frekvencije elektromotora povećava se volumen proizvedenog hladno prešanog ulja. Ekstrakt ružmarina učinkovito je povećao oksidacijsku stabilnost ulja suncokreta i šafranike, a ekstrakt zelenog čaja povećao je stabilnost repičina ulja. Veća stabilizacija ispitivanih ulja postignuta je dodatkom 0,4 % prirodnih antioksidansa u odnosu na dodatak od 0,2 %. Sintetski antioksidans propil galat nije stabilizirao ulje šafranike, a za razliku od upotrijebljenih prirodnih antioksidansa, manje štiti repičino i suncokretovo ulje od oksidacije

An Application of Image Analysis and Colorimetric Methods on Color Change of Dehydrated Asparagus (Asparagus maritimus L.)

Shape and color are key factors in quality evaluation of fresh asparagus (Asparagus maritimus L.). Typical green color of asparagus comes from the chlorophyll, pigment which has been degradated during drying process. The aim of this paper was to compare color changes of asparagus dried in laboratory tray drier equipment at different temperatures (40 °C, 50 °C, 60 °C and 70 °C) at airflow velocity of 2.75 ms-1. Color changes were obtained by digital image analysis in RGB color model and by chromameter in L*a*b* color model. Basic elements of image analysis system were low voltage halogen lamps with reflector, digital camera and programs for image pre-processing and analysis. Mean values of color parameters, color changes and correlation coefficients for asparagus were calculated for both color models. An analysis showed statistically significant influence of drying temperature on hue angle and total color change for both chosen color models of dehydrated asparagus. Represented results show that there was no statistically significant difference according to color changes between drying at 50 °C and 60 °C. Calculated correlation coefficient between color changes for used models was found to be 0.9167