Rheological behaviour of fruit and milk-based smoothies

Rheological behaviour of fruit and milk-based smoothiesl J. Rubio-Merino1, F.J. Rubio-Hernández2, A.I. Gómez-Merino2 1Unidad Docente Multiprofesional de Atención Familiar y Comunitaria Distrito Málaga-Guadalhorce, Málaga (Spain) 2Departamento de Física Aplicada II, Universidad de Málaga, Málaga (Spain) Background • Two of the most important food attributes for today´s fast-moving lifestyle are convenience and healthiness [1-2]. Fast-moving lifestyle specifically affects to elderly people, who are prone to bad-nutrition due to their dental status reducing the consumption of fruits and vegetables [3]. • Smoothies are blended beverages, and good examples of convenient and healthy foods for helping to reduce this problem. So, they are gaining increasing market leverage in the beverage sector. • Texture and rheological behaviour of foods can determine their acceptability. Therefore, added to nutritious features, smoothies must also account with outstanding mechanical properties. Stability of the products is also a main quality, which can be gained adding a small amount of stabiliser to beverage formulations. But, to avoid opposite effects, stabilisers addition should ameliorate the product texture. References [1] Verbeke W, Scholderer J, Lähteenmäki L (2009) Consumer appeal of nutrition and health claims in three existing product concepts Appetite 52:684-692. [2] Williams E, Stewart-Knox B, Rowland I (2004) A qualitative analysis of consumer perceptions of mood, food and mood-enhancing functional foods Journal of Nutraceuticals, Functional & Medical Foods 4:61-83. [3] Walls AWG, Steele JG (2004) The relationship between oral health and nutrition in older people Mechanisms of Ageing and Development 125:853-857. Experimental • Materials: bananas (BB), apples (AA), and pears (PP) (purchased in a local market). Lactose-free cow milk (LL) (COVAP, Córdoba, Spain). Xanthan gum (XX) (Sigma-Aldrich). • Stress controlled rheometer: Haake MARS (Thermo Scientific, Germany). Cone-plate (35mm, 1o). • Methods: Samples stored at 4oC during 3h prior to measurement. Pre-shear of 50s-1 during 60s and rest during 120s. Temperature control with a Peltier system. • Nomenclature: BBAAPPLLXX in %w/w Steady Flow. SFC Dynamical Analysis. SAOS Highlights • SFC of the smoothy composed by 14%w/w banana, 14%w/w apple, 14%w/w pear and 58%w/w milk at different temperatures. Error bars (lower than 5%) are omitted for clarity. Power law model was fitted (only fitting corresponding to 20oC is shown for clarity). Smoothy K (Pa·sn) n r2 1414145800 0.95±0.05 0.39±0.02 0.987 1313136100 0.90±0.06 0.42±0.04 0.979 1212126400 0.85±0.04 0.45±0.03 0.992 1414145801 1.54±0.03 0.39±0.04 0.977 1313136101 1.40±0.07 0.43±0.03 0.984 1212126401 1.33±0.05 0.45±0.02 0.982 • SAOS analysis of the smoothy composed by 14%w/w banana, 14%w/ w apple, 14%w/w pear and 58%w/w milk at 20oC. Smoothy fcritic (Hz) 1414145800 7.2±0.5 1313136100 8.5±0.3 1212126400 9.7±0.4 1414145801 7.8±0.4 1313136101 8.9±0.5 1212126401 10.5±0.5 • Very low influence of temperature on the viscosity was observed in all smoothies. • Slope and intercept increase with the amount of fruit (see table). • Slope does not vary but intercept increases with the presence of xanthan gum (see table). • Elastic behavior dominates only at high frequencies . • The critic frequency for the transition from viscous to elastic behavior decreases with the amount of fruit (see table). • The critic frequency for the transition from viscous to elastic behavior increases with the presence of xanthan gum (see table).