The freezing point of pure water is 0☌ (32☏). Dervisoglu & Yazici 14, however, found that the use of citrus fiber led to the significant improvement of the melting quality of ice cream but failed to improve viscosity, overrun, and texture. Smaller dispersed air cells produce a creamier mouthfeel during consumption ( 17), and higher overrun values ( 18 19). In turn, higher overrun values result in slower melting, since air cells act as an insulator medium ( 20 21 8 22)Īn increased overrun in reduced-fat ice creams employing inulin was reported by Akalin and Erisir 22, and by Akalin et al. Effect of increased viscosity on overrunĪn increase in the viscosity of the serum phase enhances the stabilisation of air cells and allows them to be reduced to smaller sizes ( 15 16). Studies have found that increasing inulin ( 12 13) and citrus fiber ( 14) concentrations decreases the ice cream melting rate. An increase in the viscosity of the unfrozen serum phase will significantly slow the rate at which ice cream melts ( 11 12). The three main structural phases are air cells, ice crystals, and fat globules, which are dispersed in an unfrozen, high-viscosity aqueous phase with sugars, milk proteins, and unfrozen water, called serum ( 8). Ice cream is a system composed of four structural phases. Effect of increased viscosity on meltdown rate Second, the mix has a higher resistance to water diffusion to the ice crystal surface, which reduces the growth rate ( 10). First, the higher viscosity promotes crystal melting and attrition. This effect can be explained by two facts. As the viscosity of an ice cream mix increases, the smoothness of texture increases owing to a reduction in the average crystal size. If many crystals are large, the ice cream will be perceived as being coarse or icy. Smooth and creamy ice cream requires the majority of its ice crystals to be small. Effect of increased viscosity on ice crystal size The viscosity values of samples with added fiber. Pectin, which is naturally found in apples and is well known for its gel-forming ability, can explain the intense enhancement of viscosity, which was 3-15 times greater than the control (the sample without added fiber). The researchers found that the addition of 4% fiber significantly enhanced viscosity, with apple fiber leading to the most pronounced increase. The composition of the ice cream mix tested was 6% fat, 11% milk solids not fat, 16% sugar solids, 0.2% stabiliser, 0.2% emulsifier, and 2% or 4% dietary fiber. Soukoulis et al.( 9) investigated the effects of four dietary fiber sources (oat, wheat, apple, and inulin) on the rheological and thermal properties of ice cream.
In general, as the viscosity of an ice cream mix increases, the smoothness of texture, body, and resistance to melting increase, but the overrun (the air that is whipped into the ice cream) decreases ( 8). Viscosity can be loosely defined as the thickness of a liquid, with thicker liquids having higher viscosities (honey has a higher viscosity than water for example). Smooth and creamy texture, primarily associated with a high milk fat content and small ice crystal size, is also strongly influenced by the viscosity of the ice cream mix ( 6 7 ). Improve textureĭietary fiber can be used in ice cream production to improve texture through its viscosity enhancement and freezing point depression. T o make dietary-fiber claims, fiber should be added to ice cream in amounts that range from 3g to 6g per 100 g or per 100 ml ( 5). Effect of increased viscosity on overrunĭietary fiber has been associated with a wide range of health benefits, including a reduced risk of coronary heart disease, postprandial blood glucose levels, type 2 diabetes, obesity, dyslipoproteinaemia, cardiovascular disease, and colon cancer the lowering of cholesterol the increase of calcium bioavailability and the reinforcement of the immunological system ( 1 2 3 4).
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