Abstract/Summary

Barley has been cultivated since antiquity and is the richest source of beta-glucans among all other cereals. Consumption of beta-glucans has been associated with positive health effects in humans. Specifically, the Federal Drug Administration (FDA) supports the claim that beta-glucans can reduce serum cholesterol and insulin levels and recommends consumption of three grams of beta-glucans per day for health benefits. Although barley is widely available, barley grain consumption is currently quite low, as rice and wheat are more popular types of cereals. The overarching purpose of this research project was to identify alternative ways for the utilisation of barley in the food industry and explore the technological properties of barley beta-glucans as a functional food ingredient. To this end, the main goal of the present study was to develop an efficient extraction process for beta-glucans from barley grains grown under different environmental conditions (Jordan and the UK) and incorporate these extracts into a food product to investigate the main physicochemical properties they impart in the food matrix. The experimental work of this thesis included the investigation of two extraction methods targeting beta-glucan extraction from barley flour. The first was conventional hot water extraction (HWE) method, in which different extraction times (90 min, 3 h and 4 h) and temperatures (50°C, 60°C and 70°C) were tested on defatted UK and Jordanian barley flour. The highest beta-glucan recoveries for the UK (9.3%, w/w) and the Jordanian barley (10.5%, w/w), respectively, were achieved at 60°C for 4 h and 50°C for 3h, respectively. Due to the low recovery yields of HWE, another method was investigated, that of ultrasound assisted extraction (UAE). Optimisation of the UAE conditions was followed by characterisation of the physicochemical and functional properties of the extracts. At the optimum extraction conditions for each barley cultivar, the highest beta-glucan recovery of 73.2% (w/w) was obtained for the Jordanian barley at a UAE amplitude of 15 for 35 min, which provided extracts with beta-glucan purity of 12.9% (w/w). For the UK barley, 10 A ultrasonication for 20 min resulted in beta-glucan recovery of 55.5 % (w/w), containing 10% (w/w) beta-glucans. The extracts contained also low amounts of protein (less than 0.35%, w/w) but considerable amounts of starch (53.3% for Jordanian 22.4% for UK barley, respectively). Subsequently, the effect of barley flour substitution levels, as well as the addition of UAE extracts in cracker formulations was investigated. Six cracker formulations were prepared with barley flour inclusions of 10–60% (w/w). Two wheat cracker formulations enriched with beta-glucan extracts obtained via UAE were also developed. The resulting products were evaluated for their beta-glucan content, colour (L*, a* and b*), texture (hardness and crispness), water activity, moisture content, and dough penetration. Crackers produced with various proportions of barley flour demonstrated, as predicted, higher beta-glucan content than wheat crackers (control), ranging from 0.377 g/100 g for 10% UK barley flour to 1.542 g/100 g for 60% Jordanian barley. Wheat crackers with beta-glucan extracts demonstrated the highest beta-glucan content of 2.436 g/100 g and 2.673 g/100 g using the UK and Jordanian barley extracts, respectively. Barley flour cracker formulations exhibited darker colour, had greater redness values, were harder and less crispy than control wheat crackers. When comparing the replacement 60% wheat flour by barley flour with the addition of beta-glucan extract, a significant improvement in water activity and textural properties of the final product was observed. Moreover, UAE beta-glucan extracts were considered suitable to produce crackers with a high beta-glucan content that could meet the US FDA requirement.