Faculty of Food Technology and Biotechnology, University of Zagreb
Abstract
Broken rice is an underutilized by-product of milling. Proteins prepared from broken rice by treatments with alkaline protease and papain have been characterized with regard to nutritional and functional properties. The protein content and the protein recovery were 56.45 and 75.45 % for alkaline protease treatment, and 65.45 and 46.32 % for papain treatment, respectively. Protease treatment increased the lysine and valine content, leading to a more balanced amino acid profile. Broken rice proteins had high emulsifying capacity, 58.3–71.6 % at neutral pH, and adequate water holding capacity, ranging from 1.96 to 2.93 g/g of proteins. At pH=7.0, the broken rice protein had the highest water holding capacity and the best interfacial activities (emulsifying capacity, emulsifying stability, foaming capacity and foaming stability), which may be the result of the higher solubility at pH=7.0. The interfacial activities increased with the increase in the mass fraction of broken rice proteins. The proteins prepared by the papain treatment had higher water holding capacity (p>0.05), emulsifying capacity (p0.05) than alkaline protease treatment at the same pH or mass fraction. To test the fortification of food products with broken rice proteins, pork sausages containing the proteins were prepared. Higher yield of the sausages was obtained with the increased content of broken rice proteins, in the range of 2.0–9.0 %. The results indicate that broken rice proteins have potential to be used as the protein fortification ingredient for food products.Nusprodukt meljave riže slabo se iskorištava, pa su stoga pomoću alkalne proteaze i papaina iz njega izdvojeni proteini te određena njihova hranjiva i funkcionalna svojstva. Djelovanjem alkalne proteaze dobiven je udio proteina od 56,45 % pri iskorištenju od 75,45 %, a pomoću papaina udio proteina od 65,45 % uz iskorištenje od 46,32 %. Obrada je proteazom povećala udio lizina i valina te uravnotežila profil aminokiselina. Proteini izdvojeni nakon meljave riže imali su bolja emulgatorska svojstva (58,3-71,6 % pri neutralnoj pH-vrijednosti) i dobru sposobnost vezanja vode (1,96-2,93 g/g proteina). Pri pH=7 dobiveni su proteini, osim najvećeg kapaciteta vezanja, vode imali i najbolja emulgatorska svojstva, najveću stabilnost emulzije, sposobnost stvaranja pjene te njezinu stabilnost, što može biti posljedica veće topljivosti pri toj pH-vrijednosti. Ta su se svojstva poboljšavala s povećanjem masenog udjela proteina. Proteini dobiveni pomoću papaina imali su veću sposobnost vezanja vode (p>0,05), bolja emulgatorska svojstva (p0,05) od proteina dobivenih pomoću alkalne proteaze pri istoj pH-vrijednosti i masenom udjelu. Da bi se ispitala mogućnost obogaćivanja hrane proteinima izdvojenim iz nusprodukta meljave riže, pripremljene su svinjske kobasice, čiji je prinos povećan s povećanjem udjela proteina od 2 do 9 %. Rezultati pokazuju da se tako izdvojeni proteini mogu upotrijebiti za obogaćivanje prehrambenih proizvoda
