14A-22 |
Effect of yogurt fortification with calcium and fiber on physicochemical and rheological properties |
J. F. VÉLEZ-RUIZ1, M. E. SOSA-MORALES1, and K. Alatriste-Montiel2. (1) Chemical and Food Engineering, Universidad de las Américas - Puebla, Ex-Hda. Sta. Catarina Mártir, Cholula, Puebla, 72820, Mexico, (2) Chemical and Food Eng. Dept., Sta. Catarina Martir, Cholula, Pue., Puebla, MEXICO, 72820 Foods fortification with calcium has recently received a great attention, because of its role in human nutrition. Additionally, it is generally acknowledged that the best dietary sources of calcium are milk products, thus a yogurt fortified with calcium and dietetic fiber may be considered a nutritive and functional product. Obviously the presence of calcium salt and fiber change the structure arrangement, and consequently some properties are modified. Therefore, the aim of this study was to manufacture yogurt at different levels of fortification, and to analyze the influence of the added calcium salt and fiber on their physicochemical and flow properties. The yogurts were prepared from whole milk powder by following the next steps: rehydration of the milk powder, pasteurization, cooling, fortification, inoculation, incubation, and a final treatment depending of the desired product, stirred (STY) or settled (SEY). Two levels (20, and 40 mg /100 mL of milk) of calcium, three concentrations of fiber (0.75, 1.0 and 1.25%) from coconut and fig were added to the fortified yogurt. All samples were characterized at the beginning and during three weeks of storage. As expected the calcium, density, fiber, and moisture contents of both yogurt types did not change through the storage time. pH exhibited a decreasing trend (4.6 to 4.3), showing a reverse relationship to acidity, that augmented from 0.72 to 1.18 depending of the specific formulation. Properties modified were color, syneresis, water activity and viscosity. Water activity had values from 0.954-0.993; syneresis ranged from 42 to 72% as a function of the yogurt composition; particularly, syneresis showed an increasing when calcium salt was augmented and a decreasing trend with increasing fiber content. All samples showed a shear-thinning behavior, being higher the apparent viscosity of fortified SEY (33000-2100 cP) with respect to STY (27000-1800 cP) at shear rates lower than 65 s-1.
Session 14A, Dairy Foods: General developments in dairy technology I
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