DETERMINATION OF DIETARY FIBRE – THE INFLUENCE OF MILLING FRACTION AND MIXING PROCESS | Problematika določanja vsebnosti prehranske vlaknine – vpliv frakcije mletja in načina mešanja vzorca

anglais. Dietary fibre is an important constituent of a healthy diet, composed of non-digestible carbohydrates and lignin. Over the last decades dietary fibre has gained importance for human nutrition, due to its beneficial effects on health. In addition to classical enzyme-gravimetric methods, new methods for the determination of total, insoluble and soluble dietary fibres in foods have recently been developed, but have not yet been fully implemented for use. For the purpose of creating food composition databases and for food labelling, the classical AOAC 985.29 and 991.43 methods are still widely used. The methods are enzyme-gravimetric and therefore sensitive to enzyme kinetics. The aim of the study was to investigate the effect of milling fraction and mixing of the sample on dietary fibre content determined with the AOAC method 991.43. The results showed that milling fraction significantly influences the content of dietary fibre, especially in unprocessed or slightly processed cereals, the mixing acts synergistically with milling. According to the results it is proposed to mill the sample between 200 and 500 μm. For accurate determination of dietary fibre content, it is necessary to prepare the sample correctly, since the AOAC 991.43 method is, despite its robustness, sensitive during the sample preparation step.

slovène. Prehranska vlaknina je pomembna sestavina zdrave prehrane, predstavlja neprebavljive ogljikove hidrate in lignin. V zadnjih desetletjih je zaradi dokazanih ugodnih vplivov na zdravje pridobila na pomenu za humano prehrano. Poleg klasičnih encimsko-gravimetričnih metod so bile v zadnjem času razvite nove metode za določanje skupne, netopne in topne prehranske vlaknine v živilih, vendar še niso popolnoma vpeljane v uporabo. Za namen oblikovanja podatkovnih baz o sestavi živil in za označevanje živil se še vedno uporabljata klasični metodi AOAC 985.29 in 991.43. Metodi sta encimsko-gravimetrični in zaradi tega občutljivi na encimsko kinetiko. Cilj študije je bil preveriti vpliv frakcije mletja vzorca in mešanja vzorca na določitev vsebnosti prehranske vlaknine z metodo AOAC 991.43. Rezultati so pokazali, da mletje pomembno vpliva na določitev prehranske vlaknine, še posebej, če določamo prehransko vlaknino v nepredelanih ali malo predelanih žitih. Kot najbolj primerno se je izkazalo mletje vzorca med 200 in 500 µm, mešanje pa je delovalo sinergistično z mletjem. Za natančno določitev vsebnosti prehranske vlaknine je potrebno pravilno pripraviti vzorec, saj je metoda AOAC 991.43 kljub svoji robustnosti občutljiva v fazi priprave vzorca.