B4 Physical And Functional Properties

Low-DE maltodextrins derived from potato starch are free-flowing white powders with a bland flavor and generally have a bulk density of around 300 to 450 kg per m3. They are easily blended with the other dry ingredients. Maltodextrins are easy to dissolve in cold water, are clear in solution and provide, even at very high concentration, low viscosity. The viscosity depends however, on the degree of hydrolysis (DE). Low-DE maltodextrins have higher viscosity than their higher-DE counterparts as shown in Figure 6B.1.

Figure 6B.1 Effect of DE on the viscosity of three maltodextrin solutions at 40% dissolved solids with increasing temperature. Data were obtained using a Brookfield Viscometer. (From Avebe Company Brochure, Veendam, The Netherlands, 1993. With permission.)

As correct preparation of a maltodextrin gel is of some importance in achieving optimal functional performance, the detailed method is described here. For a 25% potato maltodextrin gel, 375 g of cold tap water is placed into a 600 ml glass beaker. The beaker is placed under a mixer with a propeller-type stirrer (e.g., Janke and Kunkel). The mixer is started on medium to high speed (approximately 1500 rpm) and 125 g of maltodextrin is added slowly by sprinkling it into the vortex, until a smooth, lump-free, opaque solution of low viscosity is obtained. The opacity is caused by small air bubbles. If available, the solution can be deaerated by placing it into an ultrasonic waterbath to give a clear solution with a layer of foam on top. Ultrasonication is a good way of ensuring that the malto-dextrin has been fully dissolved. However, deaeration is not necessary for good gel formation as the air bubbles do not affect gel strength. After covering and refrigerating overnight, a white, smooth, and spreadable gel ready for further processing is obtained.

Maltodextrin gels derived from potato starch have plastic, fat-like characteristics. The texture is short, spreadable, and nonelastic in nature and the gels are thermoreversible, which means that they melt upon heating and reset to a comparable gel strength when cooled down again. The gels are also shear-thinning and reform when shearing is stopped. Maltodextrin gels are pH-stable, retaining the same gel strength in the pH range 3 to 7. Gel strengths increase with higher concentrations, as shown in Figure 6B.2. The hydration temperature is also of interest; when the product is dissolved in hot water, the gel is stronger, as shown in Figure 6B.3. However, if higher water temperatures are used, more vigourous homogenization might be required as lumps may appear more quickly in hot than in cold water.

Figure 6B.2 Effect of maltodextrin concentration on the gel strength (g/mm) of a low-DE potato maltodextrin gel. Data were obtained using a Stevens Texture Analyzer. (From Avebe Company Brochure, Veendam, The Netherlands, 1993. With permission.)

Low-DE maltodextrins can be used directly as powders or in the form of pre-prepared gels, depending on the processing conditions and the desired characteristics of the final product. In either case, low-DE maltodextrins enhance creaminess, provide body, and give a fatty mouthcoating to the food product in which they are used. Examples of applications where low-DE maltodextrins exhibit these functionalities particularly well are cream soups and sauces, frozen desserts, and bakery fillings. Maltodextrins also often contribute to a fat-like (short, spreadable, or spoonable) texture, when the concentration in the available water in the formulation is sufficiently high for gel formation to take place. This property is particularly useful in products such as cheesecake or low-fat spreads.

Figure 6B.3 Effect of hydration temperature on gel strength (g/mm) of a low-DE potato mal-todextrin. Data were obtained using a Stevens Texture Analyzer. (From Avebe Company Brochure, Veendam, The Netherlands, 1993. With permission.)

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