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The ever increasing power demand has forced the power sector companies to increase their generation, transmission and distribution in turn increasing the number of power transformers in the system where necessary. Depending on the nature of operations, the transformers are chosen as either dry-type or liquid-cooled and the preference is mostly liquid cooled. Naphthenic oils have been the primary choice over the years and alternative solutions in the form of natural esters are researched extensively due to the environmental effects of Mineral Oil (MO). One such ester, Marula is presented in this research. The experiment places its focus on measurement of electrical, physical, chemical and thermal characteristics as per the standards of ASTM and IEC. The results prove the superior dielectric performance of MAO over MO. The antioxidant rich MAO exhibits superior dielectric properties and restores faster than MO after the instances of breakdown phenomena. The antioxidants show stability at both the low and high temperatures, and temperature causes minimum damage to antioxidants. In addition to that the use of such dielectric coolant minimizes the winding damage inside the transformer tank. Thus, it can be said that MAO is an excellent coolant and improves the efficiency of the transformer without the requirements of additional cooling devices.

Tijekom proizvodnje, skladištenja i toplinske obrade guščja mast podliježe oksidacijskom kvarenju. U ovom radu istraživan je utjecaj dodatka prirodnih i sintetskih antioksidanasa te sinergista (ekstrakt ružmarina, ekstrakt zelenog čaja, ekstrakt kadulje, alfa tokoferol, mješavina tokoferola, propil galat, limunska kiselina, askorbinska kiselina, kofeinska kiselina, ružmarinska kiselina) na oksidacijsku stabilnost guščje masti. Oksidacijska stabilnost masti, sa i bez dodanog antioksidansa i sinergista, ispitivana je primjenom Schaal Oven testa. Rezultati testa prikazani su kao vrijednost peroksidnog broja nakon određenog vremena držanja masti pri temperaturi 63 °C. Rezultati istraživanja pokazuju da dodani antioksidansi i sinergisti uspješno stabiliziraju guščju mast, osim α-tokoferola. Od prirodnih antioksidanasa najveću antioksidacijsku aktivnost u guščjoj masti ima ekstrakt zelenog čaja. Postigao je najveću efikasnost zaštite od oksidacijskog kvarenja. Ekstrakt ružmarina u kombinaciji sa sinergistom pokazuje veću razinu zaštite masti od oksidacije u odnosu na čisti ekstrakt ružmarina. Dodatkom mješavine tokoferola postignuta je bolja stabilizacija masti u odnosu na ekstrakt kadulje. Sintetski antioksidans propil galat uspješno je povećao stabilnost guščje masti., During production, storage and heat treatment, goose fat is subject to oxidative deterioration. This paper investigated the influence of natural and synthetic antioxidants and synergists (rosemary extract, green tea extract, sage extract, alpha tocopherol, tocopherol mixture, propyl gallate, citric acid, ascorbic acid, caffeic acid, rosmarinic acid) on the oxidative stability of goose fat. Oxidation stability of fat, with and without added antioxidants and synergists, was investigated using the Schaal Oven test. The test results are presented as the value of the peroxide number after a certain time of keeping the fat at a temperature of 63 °C. The results of the study showed that applying antioxidants and synergists successfully stabilises goose fat, with exception of α-tocopherol. Of the natural antioxidants, green tea extract has the highest antioxidant activity in goose fat. It achieved the highest efficiency of protection against oxidative deterioration. Rosemary extract in combination with a synergist shows a higher level of fat protection against oxidation compared to pure rosemary extract. By adding a tocopherol mixture, a better stabilization of the fat was achieved compared to sage extract. The synthetic antioxidant propyl gallate successfully increased the stability of goose fat., Während der Herstellung, Lagerung und Wärmebehandlung unterliegt Gänseschmalz einem oxidativen Verfall. In dieser Arbeit wurde der Einfluss von natürlichen und synthetischen Antioxidantien und Synergisten (Rosmarinextrakt, Grüntee-Extrakt, Salbeiextrakt, Alpha-Tocopherol, Tocopherol-Mischung, Propylgallat, Zitronensäure, Ascorbinsäure, Kaffeesäure, Rosmarinsäure) auf die Oxidationsstabilität von Gänseschmalz untersucht. Die Oxidationsstabilität von Schmalz, mit und ohne zugesetzte Antioxidantien und Synergisten, wurde mit dem Schaal-Ofen-Test untersucht. Die Testergebnisse werden als Wert der Peroxidzahl nach einer bestimmten Zeit der Lagerung von Schmalz bei einer Temperatur von 63 °C angegeben. Die Ergebnisse der Studie zeigen, dass die Anwendung von Antioxidantien und Synergisten Gänseschmalz erfolgreich stabilisiert, nicht aber α-Tocopherol. Von den natürlichen Antioxidantien hat Grüntee-Extrakt die höchste antioxidative Aktivität in Gänseschmalz. Er erreichte die höchste Schutzwirkung gegen oxidativen Verfall. Rosmarinextrakt in Kombination mit einem Synergisten zeigt im Vergleich zu reinem Rosmarinextrakt einen höheren Schutz von Schmalz gegen Oxidation. Durch Zugabe einer Tocopherolmischung wurde eine bessere Stabilisierung von Schmalz erreicht als mit Salbeiextrakt. Das synthetische Antioxidans Propylgallat erhöhte erfolgreich die Stabilität von Gänseschmalz., Durante la producción, el almacenamiento y el tratamiento térmico, la grasa de ganso está sujeta a deterioro oxidativo. En este trabajo se analiza la influencia de la adición de antioxidantes y sinergistas naturales y sintéticos (el extracto de romero, el extracto de té verde, el extracto de salvia, el a-tocoferol, la mezcla de tocoferoles, el galato de propilo, el ácido cítrico, el ácido ascórbico, el ácido cafeico, el ácido rosmarínico) sobre la estabilidad oxidativa de la grasa de ganso. La estabilidad a la oxidación de la grasa, con y sin antioxidantes y sinergistas añadidos, fue investigada mediante la prueba del Schaal. Los resultados de la prueba se presentan como el valor del número de peróxido después de un cierto tiempo de mantenimiento de la grasa a una temperatura de 63 °C. Los resultados de la investigación muestran que los antioxidantes y sinergistas agregados estabilizan con éxito la grasa de ganso, excepto el α-tocoferol. De los antioxidantes naturales, el extracto de té verde tiene la mayor actividad antioxidante en la grasa de ganso. Logró la más alta eficiencia de protección contra el deterioro oxidativo. El extracto de romero en combinación con un sinergista muestra un mayor nivel de protección de las grasas contra la oxidación en comparación con el extracto de romero puro. Al agregar una mezcla de tocoferoles, se logró una mejor estabilización de la grasa en comparación con el extracto de salvia. El antioxidante sintético galato de propilo aumentó con éxito la estabilidad de la grasa de ganso., Durante la produzione, lo stoccaggio e il trattamento termico, il grasso d'oca è soggetto a irrancidimento ossidativo. In questo lavoro, è stata studiata l'influenza dell'aggiunta di antiossidanti e sinergizzanti naturali e sintetici (estratto di rosmarino, estratto di tè verde, estratto di salvia, alfa tocoferolo, miscela di tocoferoli, gallato di propile, acido citrico, acido ascorbico, acido caffeico, acido rosmarinico) sulla stabilità ossidativa del grasso d'oca. La stabilità ossidativa del grasso, con e senza l'aggiunta di antiossidanti e sinergizzanti, è stata studiata utilizzando il test Schaal Oven. I risultati del test sono presentati come il valore del numero di perossidi dopo che il grasso è stato mantenuto per un certo tempo alla temperatura di 63 °C. I risultati della ricerca mostrano che gli antiossidanti e i sinergizzanti aggiunti stabilizzano efficacemente il grasso d'oca, ad eccezione dell'α-tocoferolo. Tra gli antiossidanti naturali, l'estratto di tè verde ha evidenziato la più alta attività antiossidante rispetto al grasso d’oca; ha raggiunto, infatti, la massima efficienza di protezione contro l’irrancidimento ossidativo. L'estratto di rosmarino, in combinazione con un sinergizzante, mostra un livello di protezione dei grassi contro l'ossidazione più elevato rispetto all'estratto di rosmarino puro. Aggiungendo una miscela di tocoferolo, si ottiene una migliore stabilizzazione del grasso rispetto a quella ottenuta con l'estratto di salvia. L'antiossidante sintetico gallato di propile ha aumentato efficacemente la stabilità ossidativa del grasso d'oca.

Za proizvodnju jestivih biljnih ulja uzgajaju se biljne kulture uljarica. Kod industrijske proizvodnje biljna ulja mogu se dobiti prešanjem i ekstrakcijom s organskim otapalima. Biljna ulja i masti pokazuju različitu stabilnost, otpornost prema oksidacijskom kvarenju zbog različitog sastava masnih kiselina kao i udjela tokoferola. Rok trajanja jestivih ulja i masti može se produžiti dodatkom antioksidanasa i sinergista uz određene uvjete skladištenja ovih proizvoda. Oilseed crops are grown for the production of edible vegetable oils. In industrial production, vegetable oils can be obtained by pressing and extraction with organic solvents. Vegetable oils and fats show different stability, resistance to oxidative spoilage due to different fat acid composition as well as tocopherol content. The shelf life of edible oils and fats can be extended by the addition of antioxidants and synergists under certain storage conditions of these products.

Sikavica (Silybum marianum L.) je dvogodišnja, zeljasta, krupna i razgranata biljka do 2 m visine. Sikavica je poznata po tvari silimarin koja povoljno djeluje na jetru, a nalazi se u sjemenkama. U ovom radu istraživana je održivost hladno prešanog ulja sikavice s dodatkom prirodnih antioksidanasa, umjetnog antioksidansa i sinergista, primjenom Schaal Oven testa pri 63 ᵒC tijekom četiri dana. Od antioksidanasa korišteni su: ekstrakti ružmarina (tip StabilEnhance i tip OxyLess CS), α-tokoferol, mješavina tokoferola, ekstrakt kadulje, eterično ulje (lavanda, slatki pelin, smilje, lovor, timijan i komorač), propil galat i sinergist limunska kiselina. Rezultati su pokazali da ekstrakt ružmarina (tip OxyLess CS 0,2 %) i ekstrakt ružmarina (tip OxyLess CS 0,2 %) sa sinergistom limunskom kiselinom (0,01 %) imaju najbolje antioksidacijsko djelovanje kod stabilizacije hladno prešanog ulja sikavice. Milk thistle (Silybum marianum L.) is a biennial, herbaceous, tall and branched plant, which can grow up to 2 metres. It is known to contain silymarin, which is a substance that has a positive effect on the liver and it is found in the seeds of the plant. This is a research on the sustainability of milk thistle's cold pressed oil with the addition of natural antioxidants, artificial antioxidants and synergist. The method used for this research is the Schaal Oven test, which was applied for 4 days at 63°C. The antixodiants used were the rosemary extracts (StabilEnhance and Oxyless CS types), alpha tocopherol, mixed tocopherols, sage extract, essential oil (lavander, sweet wormwood, helichrysum, bay leaves, thyme), propyl gallate and a citric acid synergist. The results have shown that the rosemary extract of type Oxyless CS 0,2% and the rosemary extract of type Oxyless CS 0,2% with a citric acid synergist (0,02%) have the most prominent antioxidant effect on the cold pressed oil of milk thistle.

U ovom istraživanju određivana je oksidacijska stabilnost hladno prešanog lanenog ulja, s i bez dodataka prirodnih i sintetskih antioksidanasa te sinergista. Prvo su određeni parametri kvalitete ulja (peroksidni broj, slobodne masne kiseline), primjenom standardnih metoda. Antioksidansi koji su korišteni u ovom istraživanju su: ekstrakt ružmarina, α-tokoferol, mješavina tokoferola, ekstrakti kadulje, propil galat, butil hidroksianisol te sinergisti askorbinska i limunska kiselina. Oksidacijska stabilnost hladno prešanog lanenog ulja ispitivana je primjenom Oven testa na 63 ˚C. Rezultati ovog istraživanja prikazani su vrijednostima peroksidnog broja tijekom 5 dana provedbe testa. Dodatkom ekstrakta ružmarina postignuta je bolja zaštita od oksidacijskog kvarenja u odnosu na ispitivane antioksidanse. Sintetski antioksidansi propil galat i butil hidroksianisol pokazali su zaštitu, ali ne značajnu, dok α-tokoferol i mješavina tokoferola uopće nisu pokazali zaštitu od oksidacijskog kvarenja. Najveća zaštita hladno prešanog lanenog ulja od oksidacijskog kvarenja ostvarena je dodatkom askorbinske kiseline prirodnom antioksidansu ekstraktu ružmarina. In this research the oxidation stability of cold-pressed linseed oil, with and witout natural and synthetic antioxidants and synergists was determined. First, oil quality parameters (peroxide number, free fatty acids) were defined, using standard methods. Antioxidants used in this research were: rosmary extract, α-tocopherol, tocopherol mix, sage extract, propyl galate, butyl hydroxyanisole and synergistic ascorbic acid and citric acid.Oxidation stability of cold-pressed linseed oil was tested using Oven test on 63 ˚C. The results of the testing are shown in peroxide number value during the 5 days of testing. Addition od rosmary extract reached better protection from oxidation in comparison with tested antioxidants. Synthetic antioxidant propyl galate and butyl hydroxyanisole showed protection, but not a significant one, while α-tocopherol and tocopherol mix did not show protection from oxidation. The greatest protection of cold-pressed linseed oil from oxidation, was realized with the addition of synergist ascorbic acid in natural antioxidant rosmary extract.

U ovom radu ispitan je utjecaj dodatka prirodnih i sintetskih antioksidanasa te sinergista na promjenu oksidacijske stabilnosti (održivosti) hladno prešanog konopljinog ulja. Od prirodnih antioksidanasa korišteni su ekstrakt ružmarina OxyLess CS, ekstrakt kadulje, alfa tokoferol, mješavina tokoferola, ekstrakt maslinove komine i katehin, a od sintetskih antioksidanasa propil galat te butil hidroksianisol. Kao sinergisti korištene su askorbinska i limunska kiselina. Efikasnost dodatka navedenih antioksidanasa i sinergista u stabilizaciji ulja određena je SchaalOven testom oksidacijske stabilnosti kod konstantne temperature 63 ⁰C. Također, primjenom standardnih metoda određeni su osnovni parametri kvalitete konopljinog ulja: peroksidni broj, slobodne masne kiseline, netopljive nečistoće i udio vlage. Rezultati pokazuju da je dodatkom prirodnih antioksidanasa postignuta bolja zaštita ulja od oksidacijskog kvarenja, nego dodatkom sintetskih antioksidansa. Najbolje djelovanje na usporavanje oksidacijskog kvarenja konopljinog ulja pokazao je ekstrakt ružmarina. Sinergisti su dodatno povećali otpornost ulja konoplje prema oksidacijskom kvarenju, a bolje sinergističko djelovanje pokazala je askorbinska kiselina. Aim of this study was to examine the influence of the addition of natural and synthetic antioxidants and synergists on the oxidative stability of cold pressed hemp oil. The natural antioxidants used were rosemary OxyLess CS extract, sage extract, alpha tocopherol, a mixture of tocopherol, olive pomace and catechin, and synthetic antioxidants propyl gallate and butyl hydroxyanisole. Ascorbic and citric acid were used as synergists. The effectiveness of the addition of these antioxidants and synergists in oil stabilization was determined by the Schaal Oven oxidation stability test at a constant temperature of 63 ⁰C. Also, by using standard methods, basic parameters of hemp oil quality were determined: peroxide number, free fatty acids, insoluble impurities and moisture content. The results showed that the addition of natural antioxidants results in better protection of the oil from oxidative deterioration than the addition of synthetic antioxidants. Rosemary extract showed the best effect in slowing down the oxidative degradation of hemp oil. Synergists further increased the resistance of hemp oil to oxidative degradation, and ascorbic acid showed better synergistic activity.

Mikrovalno zagrijavanje je široko primjenjiva i veoma moderna metoda koja se koristi u pripremi hrane. U ovom radu istraživan je utjecaj mikrovalnog zagrijavanja, dodatka antioksidansa i sinergista na oksidacijsku stabilnost hladno prešanog ulja konoplje. Od prirodnih antioksidanasa korišteni su ekstrakt ružmarina, ekstrakt kadulje, sintetski antioksidans BHA te sinergist limunska kiselina. Uzorci ulja zagrijavani su u mikrovalnoj pećnici kod konstantne snage u različitom vremenskom periodu. Također su uzorci zagrijavani kod različite snage uređaja i konstantnom vremenskom periodu. Rezultati ispitivanja prikazani su vrijednostima peroksidnog broja koji predstavlja stupanj oksidacijskog kvarenja ulja. Rezultati pokazuju da mikrovalnim zagrijavanjem ulja u vremenu 10-50 minuta dolazi do porasta temperature i peroksidnog broja ulja. Najveća stabilnost ulja konoplje postignuta je kombinacijom ekstrakta ružmarina i sinergista limunske kiseline. Microwave heating is a widely-applicable and quite modern method used in food preparation. In this thesis, we research the influence of microwave heating, addition of antioxidants and synergists on oxidation stability of cold pressed hemp oil. Natural antioxidants used are rosemary extract, sage extract, synthetic antioxidant of BHA and citric acid synergist. Samples of oil were heated in a microwave oven under constant power in a different time period. Samples were also heated under different power in a constant time period. Test results are presented in peroxide values which represent the rancidification of oil. The results show that by using microwave heating in a time period of 10 - 50 minutes, temperature and peroxide value of oil rises. The greatest stability of hemp oil was achieved by a combination of rosemary extract and citric acid synergist.

U ovom radu određena je oksidacijska stabilnost mješavine biljnih ulja. Ispitana je oksidacijska stabilnost mješavine hladno prešanog lješnjakovog ulja i hladno prešanog ulja koštica grožđa (70:30) bez dodatka antioksidansa, te sa dodatkom prirodnih i sintetskih antioksidanasa uz dodatak limunske kiseline. Parametri kvalitete ulja (peroksidni broj, slobodne masne kiseline) određeni su primjenom standardnih metoda. Prirodni antioksidansi koji su korišteni u ovom ispitivanju su: ekstrakt nara, ružmarina i kadulje, udjela 0,2 %, mješavina tokoferola udjela 0,2 % te eterična ulja konopljike, lavande, smilja, slatkog pelina i divlje mrkve udjela 0,05 %. Kao sinergist korištena je limunska kiselina udjela 0,01 %. Kao sintetski antioksidans korišten je propil galat u udjelu 0,01 %. Oksidacijska stabilnost mješavine ulja ispitivana je Oven testom na temperaturi od 63 ˚C tijekom 4 dana. Kroz rezultate ispitivanja prikazana je vrijednost peroksidnog broja za pojedinačni uzorak. Ekstrakt ružmarina pokazao je najbolju zaštitu mješavine ulja od oksidacije, dok ekstrakt nara i mješavina tokoferola ne pokazuju zaštitu mješavine ulja. Dodatkom eteričnog ulje smilja postignuta je najbolja zaštita mješavine ulja, dok podjednako dobru zaštitu pokazuju eterično ulja lavande i slatkog pelina. Limunska kiselina djeluje kao sinergist uz ekstrakt ružmarina zbog čega je postignuta najbolja zaštita mješavine ulja od oksidacijskog kvarenja. In this study the oxidative stability of mixture consisted of vegetable oils was determined. The oxidative stability of mixture of cold-pressed walnut oil and cold pressed grape seed oil (70:30) was tested without the addition of antioxidants, and with the addition of natural and synthetic antioxidants with added synergist citric acid. The oil quality parameters (peroxide number, free fatty acids) was determined by using standard methods. The natural antioxidants used in this study are: pomegranate extract, rosemary and sage extract, 0.2%, a mixture of 0.2% tocopherol and essential oils of hemp, lavender, immortelle, sweet wormwood and wild carrot 0.05%. As a synergist, the citric acid content was 0.01%. As a synthetic antioxidant, propyl galate was used in the share of 0.01 %. Oxidative stability of the oil mixture was tested by the Oven Test at a temperature of 63 °C for 4 days. The test results show the peroxide number for the individual sample. Rosemary extract showed the best protection of the oil blend from oxidation, while the pomegranate extract and tocopherol blend show no protection for the oil blend. The best protection of oil blend is achieved by the addition of essential immoretelle oil, while equally good protection is shown by lavender and sweet wormwood essential oils. The best protection against oil oxidation for this mixture of oils was by citric acid which acts as a synergist with rosemary extract.

U ovom istraživanju određivana je oksidacijska stabilnost mješavine hladno prešanog lješnjakovog ulja i lanenog ulja u omjeru 50 : 50 sa i bez dodataka prirodnih i sintetskih antioksidanasa te sinergista. Primjenom standardnih metoda, određeni su parametri kvalitete ulja (peroksidni broj, slobodne masne kiseline). Antioksidansi koji su korišteni u ovom radu su ekstrakti nara, ružmarina i kadulje, eterično ulje konopljike, lavande, slatkog pelina, divlje mrkve, smilja, propil galat i mješavina tokoferola te sinergist limunska kiselina. Oksidacijska stabilnost ulja ispitivana je primjenom Oven testa. Rezultati ispitivanja prikazani su vrijednostima peroksidog broja tijekom 4 dana trajanja testa. Primjena ekstrakta ružmarina pokazala je bolju zaštitu mješavine ulja od oksidacije u odnosu na ekstrakt kadulje i nara. Dodatkom eteričnog ulja smilja i lavande postignuta je veća zaštita mješavine hladno prešanog lješnjakovog ulja i lanenog ulja prema oksidacijskom kvarenju. Dodatkom sinergista limunske kiseline, prirodnom antioksidansu ekstraktu ružmarina ostvarena je najveća zaštita mješavine ulja od oksidacijskog kvarenja. In this research was determined oxidation stability of mixture consisted of cold-pressed oil of hazelnut and linseed oil in ratio 50 : 50, with and without natural and synthetic antioxidants and synergists. Using standard methods it was defined oil quality parameter (peroxide number, free fatty acids). Antioxidants that were used in this research are: pomegranate extract, rosmary and sage extract, essential oils of hemp, lavander, sweet wormwood, wild carrot, immortelle, propyl galate, tocopherol mix and syinergistic citric acid. Oil oxidation stability was tested using Oven test. The results of testing are shown in peroxide number value during the 4 days of testing. Use of rosmary extract showed better protection of oil mixture from oxidation in comparison with pomegranate and sage extract. By adding essential oil of immortelle and lavander it was achieved greater protection of mixture consisted of cold-pressed oil of hazelnut and linseed to oxidation degradation. With the addition of synergistic citric acid to natural antioxidant rosemary extract, has been proven the highest protection against oil oxidation.

U ovom radu istraživan je utjecaj procesnih parametara hladnog prešanja sjemenki konoplje na iskorištenje ulja. Ispitivani su parametri frekvencija elektromotora, veličina otvora glave preše za izlaz pogače i temperatura grijača glave preše. Također je istraživan utjecaj mikrovalnog zagrijavanja na oksidacijsku stabilnost ulja konoplje, sa i bez dodatka antioksidansa i sinergista. Od prirodnih antioksidansa korišteni su ekstrakt ružmarina, ekstrakt kadulje, sintetski antioksidans BHA te sinergist limunska kiselina. Uzorci ulja zagrijavani su u mikrovalnoj pećnici kod konstante snage u različitom vremenskom periodu. Također su uzorci zagrijavani kod različite snage uređaja i konstantnom vremenskom periodu. Rezultat testa ubrzane oksidacije ulja konoplje izražen je peroksidnim brojem. Porastom frekvencije elektromotora i veličine otvora glave preše za izlaz pogače dolazi do smanjenja količine proizvedenog ulja konoplje. Porastom temperature glave preše povećava se proizvodnja sirovog ulja i hladno prešanog ulja. Mikrovalnim zagrijavanjem uzoraka ulja u vremenu 10-50 minuta dolazi do porasta temperature i peroksidnog broja, dolazi do porasta oksidacijskog kvarenja ulja. Najveća stabilnost ulja konoplje postignuta je kombinacijom ekstrakta ružmarina i sinergista limunske kiseline., In this study the influence of process parameters of cold pressing hemp seeds on yield oil was researched. Electric motor frequency, nozzle size and nozzle heater temperature were the investigated parameters. The effect of microwave heating to oxidative stability of hemp oil, with and without the addition of antioxidants and synergists, was also researched. Out of natural antioxidants there were used rosemary extract and sage extract, BHA synthetic antioxidant and citric acid synergist. Oil samples were heated in microwave oven at constant power in different time intervals. Samples were also heated with different appliance power and in constant period. The result of accelerated hemp oil oxidation test is expressed by peroxide number. The increase in electric motor frequency and nozzle size results in the quantity decrease of produced hemp oil. The increase in the nozzle size temperature increases the production of crude oil and cold pressed oil. Microwave heating of oil samples in the period of 10 to 50 minutes leads to the increase of temperature and peroxide number which further leads to oxidative degradation. The highest hemp oil stability was achieved by the combination of rosemary extract and citric acid synergists.

Djevičansko maslinovo ulje ima veliku otpornost prema oksidacijskom kvarenju, zbog sastava triacilglicerola s niskim udjelom polinezasićenih masnih kiselina i skupine fenolnih antioksidansa sastavljenih uglavnom od polifenola i tokoferola. U ovom radu istraživan je utjecaj mikrovalnog zagrijavanja na oksidacijsku stabilnost ekstra djevičanskog maslinovog ulja, sa i bez dodatka antioksidansa i sinergista. Od prirodnih antioksidansa korišteni su ekstrakt ružmarina i ekstrakt zelenog čaja te sinergist limunska kiselina. Uzorci ulja sa i bez dodatka antioksidansa i sinergista zagrijavani su u mikrovalnoj pećnici kod konstante snage 300 W u različitom vremenskom periodu (5, 10, 15 i 20 minuta). Uzorci su također zagrijavani i kod različite snage uređaja (180, 300, 450W) u konstantnom vremenskom periodu 5 minuta. Rezultat testa ubrzane oksidacije ekstra djevičanskog maslinovog ulja izražen je peroksidnim brojem. Mikrovalnim zagrijavanjem uzoraka tijekom duljeg vremena zagrijavanja dolazi do porasta temperature i vrijednosti peroksidnog broja, odnosno dolazi do porasta oksidacijskog kvarenja ulja. Dodatkom antioksidansa i sinergista povećana je stabilnost ekstra djevičanskog maslinovog ulja. Najveća stabilnost ekstra djevičanskog maslinovog ulja postignuta je kombinacijom ekstrakta zelenog čaja i sinergista limunske kiseline., Virgin olive oil has a high resistance to oxidative deterioration due to both a triacylglycerol composition low in polyunsaturated fatty acids and a group of phenolic antioxidants composed mainly of polyphenols and tocopherols. This essay discusses the effect of microwave heating on the oxidative stability of extra virgin olive oil with or without the addition of antioxidants and synergists. Of natural antioxidants are used rosemary extract and green tea extract and citric acid synergist. Oil samples with or without the addition of antioxidants and synergists were heated in a microwave oven at a constant power of 300 W over a different time period (5, 10, 15 and 20 minutes). Samples were also heated at different power levels (180, 300, 450W) in a constant time period of 5 minutes. The result of the accelerated oxidation test of olive oil is expressed by the peroxide number. Microwave heating of the samples during a longer heating time increases the temperature and the value of the peroxide number, which results in an increase in oxidative oil degradation. Addition of antioxidants and synergists increased the stability of olive oil. The highest stability of extra virgin olive oil was achieved by a combination of green tea extract and synergistic citric acid.

U ovom radu istraživan je utjecaj mikrovalnog zagrijavanja na oksidacijsku stabilnost ekstra djevičanskog maslinovog ulja, sa ili bez dodatka antioksidanasa i sinergista. Od prirodnih antioksidanasa korišteni su ekstrakt ružmarina i ekstrakt zelenog čaja te sinergist limunska kiselina. Uzorci ulja sa ili bez dodatka antioksidanasa i sinergista zagrijavani su u mikrovalnoj pećnici kod konstante snage 300 W u različitom vremenskom periodu (5, 10, 15 i 20 minuta). Uzorci su također zagrijavani i kod različite snage uređaja (180, 300, 450 W) u konstantnom vremenskom periodu 5 minuta. Rezultat testa ubrzane oksidacije maslinovog ulja izražen je peroksidnim brojem. Mikrovalnim zagrijavanjem uzoraka tijekom duljeg vremena zagrijavanja dolazi do porasta temperature i vrijednosti peroksidnog broja, odnosno dolazi do porasta oksidacijskog kvarenja ulja. Dodatkom antioksidanasa i sinergista povećana je stabilnost maslinovog ulja. Najveća stabilnost ekstra djevičanskog maslinovog ulja postignuta je kombinacijom ekstrakta zelenog čaja i sinergista limunske kiseline. This essay discusses the effect of microwave heating on the oxidative stability of extra virgin olive oil with or without the addition of antioxidants and synergists. Of natural antioxidants are used rosemary extract and green tea extract and citric acid synergist. Oil samples with or without the addition of antioxidants and synergists were heated in a microwave oven at a constant power of 300 W over a different time period (5, 10, 15 and 20 minutes). Samples were also heated at different power levels (180, 300, 450W) in a constant time period of 5 minutes. The result of the accelerated oxidation test of olive oil is expressed by the peroxide number. Microwave heating of the samples during a longer heating time increases the temperature and the value of the peroxide number, which results in an increase in oxidative oil degradation. Addition of antioxidants and synergists increased the stability of olive oil. The highest stability of extra virgin olive oil was achieved by a combination of green tea extract and synergistic citric acid.

Hladno prešano konopljino ulje proizvodi se prešanjem visokokvalitetnih sjemenki industrijske konoplje kroz nekoliko osnovnih koraka pripreme sirovine(čišćenje, sušenje, ljuštenje i mljevenje). Nakon pripreme slijedi cijeđenje sirovog ulja iz sjemenki, tj. prešanje te čišćenje prešanog sirovog ulja za očuvanje senzorskih svojstava ulja. Za stabilizaciju ulja i spriječavanjeautooksidacije, koriste se prirodni (ekstrakti začinskih biljaka) i sintetski antioksidansi te sinergisti. Kako bi ulje bilo što kvalitetnije, prate se osnovni parametri kvalitete koji su pokazatelji da li je došlo do kvarenja ulja još u sjemenkama, tijekom loših uvjeta skladištenja ili se prerađivala sjemenka loše kvalitete. Cold-processed hemp oil is produced by pressinghigh quality industrial hemp seedsthrough some key steps in preparing (cleaning, drying, peeling and grinding). After preparation, crude oil issqueezed by pressing the seeds, and cleaned in order to maintain its good sensory properties. Natural (extracts of herbs) and synthetic antioxidants, as well as synergists are used for stabilization and prevention of autooxidation. To get high oil quality, we used monitored parameters of quality which are indicators of oil deterioration during storage or processing of seeds of poor quality.

Pistacija je nutritivno bogat orašasti plod. Sadrži 40-63 % ulja te je pogodna sirovina za proizvodnju ulja. U ovom istraživanju određivana je oksidacijska stabilnost hladno prešanog ulja pistacije sa i bez dodatka prirodnih i sintetskih antioksidanasa te sinergista. Primjenom standardnih metoda, određeni su parametri kvalitete ulja: peroksidni broj, udio slobodnih masnih kiselina. Antioksidansi koji su korišteni u ovom radu su ekstrakti zelenog čaja, nara, ružmarina, eterično ulje rtanjskog čaja, propil galat te sinergisti askorbinska i limunska kiselina. Oksidacijska stabilnost ulja ispitana je primjenom Oven testa. Rezultati ispitivanja prikazani su vrijednostima peroksidnog broja tijekom 4 dana trajanja testa. Primjena ekstrakta ružmarina pokazuje bolju zaštitu ulja od oksidcije u odnosu na ekstrakt zelenog čaja i nara. Dodatkom eteričnog ulja rtanjskog čaja postignuta je najveća zaštita ulja pistacije prema oksidacijskom kvarenju. Korištenjem sinergista boljim se pokazala limunska kiselina u odnosu na aksokrbinsku kiselinu u kombinaciji sa prirodnim antioksidansom. Pistachio is a nutritrive rich nut. It contains 40-63% of oils and therefore it is suitable for oil production. In this research oxidation stability of cold pressed pistachio oil, with or without added natural and sintetic antioxidants and synergist, is examined. With the application of standard methods, the oil quality parameters: peroxide number and free fat acids content were determined. Antioxidants used in this research were as follows:green tea extract,pomegranate extract,rosemary extract, essential oil of winter savory tea and propyl gallate. Synergists used in this research were ascorbic and citric acid.The oxidation stability of oil was tested using the Oven test. Test results are shown as a peroxide number value over the 4 days duration of the test.Extract of rosemary oil has better protection against oxidation as compared to the green tea extract and pomegranate.The most significant antioxidant effect is shown with addition of essential oil of winter savory tea. As a synergist better effect is shown by citric acid in regard to ascorbic acid in a combination with natural antioxidans.

U ovome radu je ispitan dodatak antioksidanasa na oksidacijsku stabilnost palmine masti. Osnovni parametri kvalitete palmine masti su peroksidni broj (Pbr) i slobodne masne kiseline (SMK). Od antioksidansa korišteni su ekstrakt zelenog čaja, ekstrakt ružmarina (Oxy 'Less CS), ekstrakt maslinovog lista, ekstrakt nara u koncentraciji 0,1 i 0,3 %, te eterična ulja bosiljka, majčine dušice i rtanjskog čaja u koncentraciji 0,05%. Održivost palmine masti prikazana je kroz Pbr tijekom 4 dana provedbe Oven testa i Testa održivosti na 98°C. Najveća razina zaštite palmine masti od oksidacijskog kvarenja postiže se dodatkom ekstrakta ružmarina(Oxy 'Less CS) kod obje koncentracije. Primjena sinergista limunske kiseline s ekstraktom ružmarina (Oxy 'Less CS), postignuta je dodatna zaštita palmine masti od oksidacijskog kvarenja. Eterično ulje rtanjskog čaja (0,05%) pokazuje veću zaštitu palmine masti od oksidacije u odnosu na eterično ulje bosiljka i majčine dušice. In this study is monitored the influence of antioxidants on oxidative stability of palm fat. The basic parameters of quality palms fats are: peroxide value and free fatty acids.The antioxidants used in this study are: green tea extract, rosemary extract (Oxy 'Less CS), olive leaf extract, pomegranate extract, at concentractions of 0,1% and 0,3%, thyme and basil volatie oil as well as sovary tea volatile oil at concntraction of 0,05 %. Sustanbility of palm grease is show trough the peroxide value, during the four days of the implementation of the Oven test and oxidation stability test 98 The higest efficiency of palm fat is shown on the rosemary extract (Oxy 'Less CS)at the both of concentraction. Application synergist of citric acid with rosemary extract (Oxy 'Less CS), additional protection palm fats from oxidative deterioration.The essential oil of sovary tea shows greater protection palm fat from oxidation in relation to the essential oil of basil and thyme.

Mikrovalno zagrijavanje je moderna i široko primjenjivana metoda za pripremanje hrane. U ovom radu je istraživan utjecaj mikrovalnog zagrijavanja na oksidacijsku stabilnost hladno prešanog ulja pistacije, sa i bez dodatka antioksidanasa i sinergista. Uzorci ulja su zagrijavani u mikrovalnoj pećnici kod različite snage uređaja u vremenu 5 minuta. Također, uzorci su zagrijavani u mikrovalnoj pećnici kod konstantne snage 300 W u različitom vremenskom periodu. Rezultati testa prikazani su vrijednostima peroksidnog broja nakon mikrovalnog zagrijavanja. Primjenom veće snage uređaja i duljeg vremena trajanja mikrovalnog zagrijavanja dolazi do povećanja oksidacijskog kvarenja ispitivanog ulja. Dodatkom antioksidanasa i sinergista postignuta je veća otpornost ulja prema oksidaciji. Nakon 25 minuta mikrovalnog zagrijavanja dobivene su niže vrijednosti peroksidnog broja u odnosu na uzorak ulja bez dodanog antioksidansa (kontrolni uzorak). Najbolju otpornost prema oksidacijskom kvarenju pokazao je dodatak eteričnog ulja rtanjskog čaja, u odnosu na dodatak drugih ispitivanih antioksidanasa. Microwave heating is a contemporary and widely applied method of food preparation. This essay discusses the influence of microwave heating on the oxidation of cold-pressed pistachio oil with and without the addition of antioxidants and synergists. Oils samples with and without the addition of antioxidants and synergists were heated in a microwave oven using different power settings at 5 minute intervals. Samples were also heated in microwave oven using constant power settings of 300 W at different time intervals. The test results are shown through peroxide value and measured after microwave heating. Higher power settings and prolonged microwave heating are causing more massive oxidative damage of the tested oil. The addition of antioxidants and synergists achieved greater resistance to oil oxidation. Microwave heating with duration of 25 minutes resulted with lower peroxide value comparing to the oil sample without added antioxidant (control sample). Best resistance to oxidation deterioration showed the addition of essential oil of winter savory, comparing to the addition of other antioxidants that were examined.

Hladno prešano suncokretovo ulje proizvodi se prešanjem najkvalitetnijih suncokretovih sjemenki. Postoji nekoliko faza pripreme sirovine: čišćenje, sušenje, ljuštenje i mljevenje. Sušenjem se odstranjuje voda, to je vrlo važna faza pripreme sirovine za preradu jer se osušene sjemenke mogu duže čuvati (skladištenje vlažne sirovine pogoduje razvoju plijesni), a osim toga i bolje se prerađuje od vlažne sirovine. Nakon pripreme sirovine, sirovo ulje se iz sjemenki cijedi prešanjem, a zatim se čisti kako bi se očuvala dobra senzorska svojstva ulja. Dobiveno ulje se može kvariti zbog brojnih utjecaja, od kojih je najčešće kvarenje uzrokovano oksidacijskim procesom. Kako bi se produljila trajnost hladno prešanog ulja i spriječila autooksidacija, primjenjuju se antioksidansi i sinergisti, koji usporavaju oksidacijsko kvarenje ulja. Za stabilizaciju biljnih ulja koriste se prirodni i sintetski antioksidansi. Danas se prednost daje prirodnim antioksidansima (ekstrakti začinskih biljaka). Cold-pressed sunflower oil is produced by pressing of the finest sunflower seeds. There are several stages in the preparation of raw materials: cleaning, drying , peeling and grinding. Drying implies removing the water, so this is a very important phase in preparation of raw materials for processing, because the dried seeds can be stored longer (wet storage of raw materials is suitable for the mold development), and better processing than wet materials. After preparation of raw materials, crude oil is squeezed by pressing the seeds, and then cleaned in order to maintain its good sensory properties. The resulting oil can spoil due to numerous influences, and the most common spoilage is caused by the oxidation process. To prolong the shelf life of the cold pressed oil and prevent autoxidation, producers apply antioxidants and synergists, which inhibit oil deterioration. The natural or synthetic antioxidants are used for stabilization of vegetable oils. The natural antioxidants are preferred today (extracts of herbs).