Primerjava antioksidativnega potenciala beljakovinskih živil živalskega in rastlinskega izvora

Avtorji: Sara Meze, Jakob Rozman, Maks Ruparčič
Mentorica: mag. Marjetka Kastelic Švab

V človekovi prehrani so poleg ostalih hranil zelo pomembni tudi antioksidanti, saj preprečujejo delovanje prostih radikalov kisika (oksidantov) in posledično varujejo celice, celične membrane pred poškodbami. Nastajanje oksidantov spodbujajo stres in zunanji dejavniki, kot so npr. strupi v zraku, vodi, nikotin v tobaku, alkohol. Antioksidantov je več vrst, ki so med seboj neločljivo povezani, vsi pa so sestavni del hrane. V raziskovalni nalogi smo želeli primerjati antioksidativni potencial živalskih in rastlinskih beljakovinskih živil v surovi in kuhani obliki. Za primerjalne vzorce smo izbrali piščančje, goveje in svinjsko meso, losos, divjačino, goveja jetra, alge (Wakame – morska zelena alga), tofu, kvasne kosmiče, fižol, čičeriko in acai jagode. Vsa živila za analizo smo pripravili surova in kuhana.

Praktičen del raziskave smo začeli s pripravo vzorcev živil v 3% metafosforni kislini in nadaljevali z določanjem antioksidativnega potenciala (AOP) z radikalom DPPH•. Vzorce smo uspešno centrifugirali in mikrofiltrirali. Pred pipetiranjem vzorcev v kivete smo vsakič znova pripravili in z metanolom umerili novo DPPH raztopino. Vzorce smo med raziskavo stalno hranili v zamrzovalniku, DPPH• in druge reagente pa v digestoriju. S kemijsko-instrumentalno analizo s spektrofotometrom smo vzorcem izmerili absorbanco. S pomočjo zbranih rezultatov smo na koncu izračunali AOP 24-ih različnih vzorcev. Vse priprave vzorcev in poskuse smo izvajali v šolskem laboratoriju. Z raziskovanjem smo dokazali, da imajo najvišji AOP kuhane acai jagode, takoj za njimi kuhana jetra, surovi kvasni kosmiči, surove alge, surova goveja jetra, surov fižol in kuhan fižol. Najnižji AOP smo izračunali pri kuhanem govejem mesu. Približno enake vrednosti AOP smo izračunali pri piščančjem mesu in divjačini, kuhanem in surovem tofuju ter kuhanem in surovem lososu. Menimo, da bi se tudi surove acai jagode po rezultatih AOP približale kuhanim, vendar so zaradi močne rdeče barve zmotile analizo. Pokazale so previsoke vrednosti absorbance, kar je pri izračunu dalo netočen rezultat vrednosti AOP. Glede na dobljene rezultate izbranih vzorcev, imajo rastlinska beljakovinska živila v večini višji AOP kot živalski vzorci hrane, razen govejih jeter, ki imajo takoj za acai jagodami najvišje vrednosti AOP. Z grafičnimi prikazi smo tudi potrdili, da imajo surovi vzorci večinoma višji AOP kot vsi kuhani izbrani vzorci beljakovinskih živil.

Antioxidants are very important in the human diet, along with other nutrients, as they prevent the action of oxygen free radicals (oxidants) and consequently protect cells, cell membranes from damage, etc. The production of oxidants is stimulated by stress and external factors such as toxins in the air, water, nicotine in tobacco, alcohol. There are several types of antioxidants, all of which are inextricably linked to each other and all of which are a component of food. In this research we wanted to compare the antioxidant potential of animal and plant protein foods. The comparative samples were chicken, beef, pork, salmon, venison, beef liver, algae (Wakame – green seaweed), tofu, yeast flakes, beans, chickpeas and acai berries. All foods The practical part of the study started with the preparation of food samples in 3% metaphosphoric acid and continued with the determination of the antioxidant potential (AOP) with the DPPH• radical. The samples were successfully centrifuged and microfiltered. Before pipetting the samples into cuvettes, a new DPPH• solution was prepared and recalibrated each time with methanol. The samples were kept in a freezer at all times during the study and the DPPH• and other reagents were stored in a digestory. The absorbance of the samples was measured by chemical-instrumental analysis using a spectrophotometer. Finally, the AOP of the 24 different samples was calculated using the collected results. All sample preparations and experiments were carried out using the laboratory method. We have shown that cooked acai berries have the highest AOP, followed by cooked liver, raw yeast flakes, raw algae, raw beef liver, raw beans and cooked beans. The lowest AOP was calculated for cooked beef. Approximately the same AOP values were calculated for chicken and venison, cooked and raw tofu and cooked and raw salmon. We believe that raw acai berries would also be close to cooked acai berries in terms of AOP results, but due to their strong red colour they showed too high absorbance values, which gave an inaccurate AOP result in the calculation. According to the results obtained for the selected samples, plant protein foods tend to have a higher AOP than animal food samples. However, it was confirmed by graphical representations that the raw samples mostly have a higher AOP than all cooked selected protein food samples.