Production and stabilization of cold pressed walnut oil

U ovom radu istraživan je utjecaj procesnih parametara prešanja oraha na efikasnost proizvodnje hladno prešanog orahovog ulja. Prešanje jezgre oraha se provodilo na laboratorijskoj kontinuiranoj pužnoj preši. Prilikom prešanja mijenjali su se procesni parametri: temperature glave preše, brzina pužnice te nastavak za izlaz pogače. Nakon prešanja provedeno je prirodno taloženje sedam dana i centrifugiranje sirovog ulja. Primjenom standardnih metoda određeni su parametri kvalitete ulja: peroksidni broj, slobodne masne kiseline, udio netopljivih nečistoća i udio vlage i hlapljivih tvari. Također, ispitivana je oksidacijska stabilnost proizvedenog hladno prešanog orahovog ulja s i bez dodatka antioksidansa. Korišten je test ubrzane oksidacije ulja (Oven test). Dobiveni rezultati pokazuju da procesni parametri prešanja utječu na iskorištenje ulja. Ekstrakt ružmarina i ekstrakt zelenog čaja dodani u koncentraciji 0,1 % i 0,2 % značajno povećavaju otpornost orahovog ulja prema oksidacijskom kvarenju, u odnosu na druge ispitane antioksidanse. This study researches the influence of process parameters on the efficiency of cold pressed walnut oil production. The walnut core pressing was carried out in a laboratory continuous worm screw press. The process parameters were varied during the pressing: the temperature of the press head, frequency and cake output extensions. After pressing, natural sedimentation was conducted for seven days and centrifugation of crude oil. Walnut oil quality parameters were determined by applying standard methods: peroxide value, free fatty acids, the proportion of insoluble impurities and moisture, and volatile substance. Effect of added antioxidants on the oxidative stability of produced cold pressed walnut oil is also examined, by applying the accelerated oxidation test (Oven test). Obtained results showed the effect of process parameters on the yield of the oil. Compared to other examined antioxidants, rosemary extract and green tea extract added in a concentration of 0.1% and 0.2% are significantly increasing the resistance of walnut oil to oxidative deterioration.