Evaluating the Effect of Electromagnetic Stir-Frying Barley Flour on Yoghurt Quality

Abstract

There is a great interest in the use of natural ingredients as functional components in food products. Barley is considered as a natural thickener substitute due to its high dietary fiber content. In this work, electromagnetic stir-frying barley flour (ESBF) was developed and applied in yoghurt. The yoghurt samples were prepared by adding 10, 20, 30, and 40 g L-1 of ESBF, respectively; the control sample was made with 20 g L-1 of whey protein concentrate (WPC), and the yoghurt without any thickener was regarded as blank. The rheological, microstructural, and sensory properties were investigated to evaluate the effect of ESBF on yoghurt quality. Compared to the blank and control samples, the yoghurt with ESBF had higher contents of total solids ranging from 232.5 ± 1.2 g·kg-1 mix to 241.6 ± 1.4 g·kg-1 mix, and crude fiber ranged from 1.6 ± 0.4 g·kg-1 mix to 4.5 ± 0.6 g·kg-1 mix according to the added amount of ESBF. Representing the rheological characteristics of yoghurt, the storage modulus (G′), loss modulus (G″), and apparent viscosity increased with the amount of ESBF. Scanning electron microscope images exhibited that both WPC and barley starch were distributed uniformly in a yoghurt sample, with starch strands between and attached to the protein aggregates reducing the free end. In addition, increased stability of viscosity, water-holding capacity, and bacteria were obtained with the addition of ESBF whether after postripening or during storage of yoghurt. The highest viscosity was up to 3305 MPa s in the yoghurt with 4% ESBF. Current results indicate that ESBF could be used as a suitable natural ingredient and thickener in food.