The impact of microwave heating and antioxidants on oxidative stability of cold-pressed apricot kernel oil

Abstract

Postupkom prešanja koštice marelice proizvedena su tri proizvoda: sirovo ulje, uljni talog i pogača. Nakon postupka centrifugiranja sirovog ulja dobiveno je hladno prešano ulje koštice marelice i određeni su mu parametri kvalitete ulja (SMK, Pbr, vode, netopljivih nečistoća, saponifikacijski i jodni broj). Ispitivali smo utjecaj procesnih parametara prešanja (temperatura, veličina otvora glave preše i frekvencija elektromotora) na iskorištenje ulja kao i utjecaj mikrovalnog zagrijavanja i dodatka antioksidanasa na oksidacijsku stabilnost hladno prešanog ulja iz koštice marelice. Antioksidansi koji su korišteni u ovom ispitivanju su: ekstrakt ružmarina, ekstrakt zelenog čaja i ekstrakt nara te eterično ulje majčine dušice, origana, bosiljka i rtanjskog čaja. Nakon istraživanja utvrđeno je: najveće iskorištenje ulja kod prešanja sjemenki koštica marelica dobiveno je kod procesnih parametara nastavak za izlaz pogače 6 mm, frekvencija elektromotora 20 Hz i temperatura glave preše 100 °C. Dužim zagrijavanjem i porastom snage uređaja kod mikrovalnog zagrijavanja povećava se i brzina oksidacije ulja marelice. Od ispitivanih prirodnih antioksidanasa najbolji antioksidacijski utjecaj pokazuju ekstrakt nara (0,1%), ekstrakt ružmarina (0,3%) i eterično ulje majčine dušice (0,05%).In the process of molding apricot kernels three products are produced: crude oil, oil sludge and cake. After ten days of deposition and vacuum filtration of crude oil we obtained cold-pressed apricot kernel oil and quality parameters were determined (SMK, PBR, water insoluble impurities, saponification and iodine number). We examined the impact of molding process parameters (temperature, size of the press head hatch and electromotor frequency) to utilization of oil and the impact of microwave heating and the addition of antioxidants on oxidative stability of cold-pressed oil from the apricot kernel. Antioxidants used in this assay are: rosemary extract, green tea extract, pomegranate extract and essential oil of thyme, oregano, basil and heather (savory) tea. After research it was found that maximum utilization of oil during pressing seeds of apricot kernel is obtained by the process parameters: cake extension length 6 mm, electromotor frequency 20 Hz, and the press head temperature of 100 °C. Increased power and longer microwave heating increases the rate of oxidation of apricot oil. Of the tested natural antioxidants the best antioxidant effect showed pomegranate extract (0.1%), rosemary extract (0.3%) and the essential thyme oil (0.05%)