Rancimat method

Početkom 21. stoljeća borovnice zbog svojih nutritivnih svojstava plodova postaju popularne među potrošačima, a što povećava njihovu potražnju. Kultivirane borovnice stoga zauzimaju sve veći značaj kako u svjetskoj tako i u hrvatskoj proizvodnji voća. Mineralni sastav plodova je važna komponenta koja utječe na kvalitetu plodova i njihovu nutritivnu vrijednost. U ovom radu napravljen je prikaz mineralnog sastava plodova borovnice, kao i nutritivne vrijednosti. Na temelju proučene literature utvrđeno je kako su u plodovima borovnice najzastupljeniji makroelementi dušik i kalij dok su kod mikroelemenata to mangan i željezo. Obrađeni su i najvažniji čimbenici koji imaju utjecaj na mineralni sastav borovnica, kao što su: sorta, klima, tlo, agrotehnički i pomotehnički zahvati. Odabirom i upravljanjem navedenih čimbenika moguće je povećati kvalitetu ploda, ali i utjecati na mineralni sastav plodova borovnica.

Biljna ulja predstavljaju proizvod ograničenog vremena trajnosti jer brzo podliježu nepoželjnim promjenama (enzimski ili mikrobiološki procesi, kemijske reakcije) što rezultira kvarenjem ulja. Održivost biljnih ulja ili oksidacijska stabilnost predstavlja vrijeme kroz koje se ulja mogu sačuvati od procesa autooksidacije, od jače izražene oksidacije, bez bitnih promjena kvalitete. Oksidacijsko kvarenje biljnih ulja najčešći je tip kvarenja, a predstavlja proces oksidacije nezasićenog lanca masne kiseline (Dimić, 2000.). Poznavanje održivosti biljnih ulja važno je i za definiranje roka upotrebe ulja. Pojava i brzina procesa autooksidacije biljnih ulja ovisi o sastavu ulja, uvjetima čuvanja, prisutnosti sastojaka koji ubrzavaju (prooksidansi) ili usporavaju (antioksidansi) ovu reakciju oksidacije (Martin-Polvillo, 2004.). U malim količinama nastali produkti procesa autooksidacije narušavaju senzorska svojstva biljnih ulja tako da daju uljima neugodan miris i okus (Broadbent i Pike, Sažetak Jestiva ulja s visokim udjelom nezasićenih masnih kiselina,a naročito s polinezasićenim masnim kiselinama, osjetljivija su na oksidaciju. Oksidacijska stabilnost različitih smjesa biljnih ulja, s dodanim sintetskim i prirodnim antioksidansom i bez njega, ispitivana je primjenom Rancimat testa. Ispitivana je kombinacija suncokretovog ulja (50%) i ostalih pojedinih vrsta biljnih ulja (50%): repičino ulje, ulje kukuruzne klice, sojino ulje i ulje pšeničnih klica. U ovom je radu istraživan utjecaj sintetskog antioksidansa propil galata (0,01%), prirodnog ekstrakta ružmarina Oxy´Less ® Clear (0,5%) i prirodnog ekstrakta zelenog čaja (0,3%) na oksidacijsku stabilnost smjese suncokretovog ulja i ostalih vrsta biljnih ulja (50:50). Oksidacija smjese dviju vrsta biljnih ulja (50:50) inducirana je i mjerena primjenom Rancimat testa (model 743, Metrohm). Rezultat oksidacije ulja izražen je s indukcijskim periodom (IP) na bazi kojih je računat i zaštitni faktor (PF). Prirodni antioksidans ekstrakt zelenog čaja uspješnije povećava oksidacijsku stabilnost smjese suncokretovog ulja i ostalih ispitivanih ulja (50:50) u testiranim dozama u odnosu na prirodni ekstrakt ružmarina Oxy´Less ® Clear i sintetski propil galat. Rezultat istraživanja pokazuje da veću antioksidacijsku aktivnost, mjerenu kao indukcijski period, ima ekstrakt zelenog čaja u odnosu na ekstrakt ružmarina Oxy´Less ® Clear i propil galata u svim ispitivanim smjesama biljnih ulja.

Bučino ulje pripada grupi ekskluzivnih i vrlo skupih ulja gdje nutritivna kvaliteta opravdava visoku cijenu. U ovom radu istraživan je utjecaj parametara hladnog prešanja bučinih koštica na iskorištenje ulja. Ispitivani su parametri frekvencija elektromotora, veličina otvora glave preše te dodatak ljuske suncokreta i mikrovalno zagrijavanje bučine koštice na proizvodnju ulja. Porastom frekvencije elektromotora i veličine otvora glave preše za izlaz pogače dolazi do smanjenja količine proizvedenog ulja. Primjenom standardnih metoda određeni su osnovni parametri kvalitete ulja: peroksidni broj, slobodne masne kiseline, udio netopljivih nečistoća i udio vlage. Također, ispitivan je dodatak mješavine prirodnih antioksidanasa na oksidacijsku stabilnost hladno prešanog bučinog ulja. Od antioksidanasa korišteni su ekstrakt nara, ekstrakt ružmarina (tip Oxy’Less Clear), eterično ulje primorskog vriska i eterično ulje bosiljka u kombinaciji sa ekstraktom zelenog čaja. Određivanje oksidacijsk...

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Kultivirana borovnica (Vaccinium corymbosum L.) predstavlja jedan od najbogatijih prirodnih izvora polifenola u prehrani čovjeka. Raznolikost biološkog potencijala polifenolnih spojeva potvrđena je rezultatima brojnih znanstvenih studija. U ovom je istraživanju ispitan utjecaj fenolnih ekstrakata dobivenih iz svježih plodova te nakon različitih načina obrade plodova borovnice (liofilizacija, pasterizacija, obrada ultrazvukom visokog intenziteta) na povećanje oksidacijske stabilnosti ekstra djevičanskog maslinovog ulja. U cilju povećanja biološkog potencijala fenolnih ekstrakata u kombinaciji s njima korištene se dvije vrste emulzija tretirane postupkom mehaničke homogenizacije i ultrazvukom visokog intenziteta. Oksidacijska stabilnost ekstra djevičanskog maslinovog ulja mjerena Rancimat uređajem pokazala je značajan porast primjenom smjese emulzija i ekstrakata borovnice u odnosu na primjenu čistih fenolnih ekstrakata borovnice.Cultivated blueberry (Vaccinium corymbosum L.) represen...

Oksidacijska stabilnost ulja je parametar koji predstavlja vrijeme tokom kojeg se ulja mogu sačuvati od promjena uzrokovanih autooksidacijom. Brzina autooksidacije ovisi o sastavu ulja i može se produžiti ili skratiti u prisustvu sastojaka koji ju usporavaju ili ubrzavaju. U ovom radu analiziran je utjecaj dodataka biljnih ekstrakata (lavande, matičnjaka, mravinca, ružmarina i vriska) na oksidacijsku stabilnost ulja konoplje, lana, sezama i suncokreta. Oksidacijska stabilnost testirana je Rancimat metodom (temperatura 120°C, protok zraka 20 L/h). Sastav masnih kiselina u uljima je određen tehnikom plinske kromatografije sa plameno-ionizacijskim detektorom (GC-FID). Prema dobivenim rezultatima najveću oksidacijsku stabilnost između testiranih ulja pokazalo je ulje sezama (3,43 h), dok je najmanju oksidacijsku stabilnost imalo ulje lana (0,17 h). Dodatak ekstrakata je različito utjecao na stabilnost ulja. Ekstrakti matičnjaka, vriska i mravinca su kod ulja konoplje i lana izazvali ubr...

In this paper, walnut oil at four different temperatures (353, 363, 373 And 383 K) were oxidized under the rancimat test conditions, it was observed that the rate of oxidation increases with increasing temperature. The natural logarithm of the reaction rate constant (k) had a linear relationship with temperature changes, according to the Arrhenius equation and activated complex theory, reaction rate constant (A), energy of activation (Ea), Q10 value, enthalpy (∆H ++ ), entropy ( ∆S ++ ) was used to assess oxidative stability of walnut oil, the values of A, E a, Q10, ∆H ++ , ∆S ++ was 2.78 ⨯ 10 13 (per hour), 80.32 (kJ /mole), 2.077, 77.27(kJ /mole), -55.76 joule per

Mastic gum is a resinous sap produced by Pistacia lentiscus growing in the island of Chios (Greece) and has been recognized since Antiquity for its distinctive aroma as well as medical properties (antimicrobial, antioxidant, anti-inflammatory ones). The oral absorption of Chios Mastic gum (an insoluble polymer of poly-β-myrcene is among the most abundant contents) is poor due to its low water-solubility. We report in this study, two different Chios mastic gum extracts, the acidic mastic gum extract—AMGE—and the neutral one—NMGE, both prepared after removal of the contained polymer in order to ameliorate solubility and enhance in vivo activity. Liposomes are presented as a promising delivery system due to their physicochemical and biophysical properties to increase stability and absorption efficiency of the mastic gum extracts within the gastrointestinal (GI) tract. The aim of this study was to evaluate the stability in GI simulated conditions together with cytotoxic and antimicrobia...

In this paper, walnut oil at four different temperatures (353, 363, 373 And 383 ̊ K) were oxidized under the rancimat test conditions, it was observed that the rate of oxidation increases with increasing temperature. The natural logarithm of the reaction rate constant (k) had a linear relationship with temperature changes, according to the Arrhenius equation and activated complex theory, reaction rate constant (A), energy of activation (E a), Q10 value, enthalpy (∆H ++), entropy (∆S ++) was used to assess oxidative stability of walnut oil, the values of A, E a , Q10, ∆H ++ , ∆S ++ was 2.78 ⨯ 10 13 (per hour), 80.32 (kJ /mole), 2.077, 77.27(kJ /mole),-55.76 joule per mole kelvin, respectively.

Fruits and vegetables are major sources of antioxidants. These are substances that remove free-radical intermediates by being oxidized themselves and delay or inhibit other oxidation reactions. Recent studies make clear that an antioxidant-rich diet acts as a health protecting factor. The antioxidant that was used in this study was 2,5-dimethyl-4-hydroxy-3(2H)-furanone (HDMF). Two frying methods (with and without antioxidant) were used: the first one with no replenishment of oil and the second one with frequent replenishment of oil. As it was proved by the induction period, using the Rancimat method, HDMF increased the resistance against oxidation not only of the frying oils but also of the oil that was absorbed by the chips. The results were in line with those of croissants when they were baked with or without HDMF. Taste panel test confirmed those results as panelists showed a clear preference for those products that were protected against oxidation by HDMF.

Mastic is a well-known natural resin from the trunk and branches, of Pistacia lentiscus var. chia (Anacardiaceae), which is grown as endemic only in the Greek island of Chios. During this work, a total mastic gum extract was prepared after removal of the contained insoluble polymer in order to ameliorate solubility and enhance in vivo activity. To overcome the drawbacks (i.e solubility, bioavailability, etc.) of mastic gum extracts (acidic and neutral fraction), the selection of a suitable carrier is crucial. Three different methods of preparation, thin-film evaporation, freezing-thawing, and ethanol injection were used for the preparation of liposomes consisting of Phosphatidylcholine (PC) and Cholesterol (CH). The effect of PC: CH molar ratio on the percentage of mastic extract encapsulated was investigated. Mastic gum extracts components-liposomes interaction was studied using Fourier transform infrared (FT-IR) spectroscopy. The effects of different preparation methods on the physicochemical properties of colloidal systems were evaluated by means of surface morphology, field emission Scanning Electron Microscopy (SEM), and size distribution using a particle size analyzer. For the determination of the antioxidant activity two methods were used: I) The Rancimat method where the protection factor was determined for each sample and compared with known antioxidants. II) Differential Scanning Calorimetry (DSC) where the temperature of oxidation for each sample was determined. Moreover, the crude extract (EtOAc-MeOH) of mastic, as well as, its acidic and neutral fractions was assayed against a panel of 9 human and food pathogenic gram (±) bacteria and fungi.

The possibility to increase the nutritional value of table olives using polyphenols extracted from olive leaves was studied. Leaves were subjected to extraction using water with proportions of 1%, 5% and 10% of leaves and various temperatures and times (room temperature/24 h, 40 °C/10 min and 70 °C/5 min). The antioxidant activity of extracts was determined using the Rancimat method and their content in oleuropein and hydroxytyrosol was determined by HPLC. The extract with the highest antioxidant activity and polyphenol content (10% ratio of olive leaves extracted at room temperature for 24 h) was used for the treatment of debittered table olives. The treated and untreated olives were subjected to determination of their α-tocopherol, oleuropein and hydroxytyrosol content. A 457% increase was observed for oleuropein and 109% for hydroxytyrosol content after treatment. Sensory evaluation of treated table olives showed an increase in bitterness. However, treated and untreated table olives showed equal overall acceptability and overall preference.