MILK BEVERAGES AND FERMENTED MILK DRINKS
It is well-known that the use of common and established foods like milk and daily products is a simple and convenient way to incorporate carbohydrate- based bioactive components including dietaiy fibers into a daily diet and many fiber-enriched dairy products are now available in the market (Table 3.1) (Chen et al., 2010). Villegas et al. (2007) studied the effect of different types of inulin, i.e., short-chain, native, and long-chain (6.0, 8.0, and 10.0% w/w) as a fat substitute on the creaminess and thickness of whole milk-beverage model system and skimmed-milk beverage. Inulin-fortified samples were thicker and creamier than the insulin-free zones and the authors suggested that high concentrations of long-chain inulin (over 8.0%) can be used to create functional reduced-fat milk beverages with similar thickness and creaminess compared to the full-fat milk beverages. In another study, they also tested the concentrations of 2.0, 4.0, 6.0, 8.0 and 10.0% inulin with different chain lengths (oligofructose, native, and long-chain) on the flow behavior of milk beverages and reported that the beverages containing low concentrations of inulin (2.0, 4.0 and 6.0%) showed Newtonian flow behavior, while a shear-thinning behavior was observed in samples containing 8.0 and 10.0% concentrations of long-chain inulins (Villegas and Costell, 2007). Abbasi and Mohammadi (2013) used the Persian gum (soluble and insoluble fractions) and a mixture of soluble fractions of gum tragacanth and Persian gum to stabilize the acidified milk-orange juice mixture. The use of Persian gum (2.20%), its soluble fraction (1.0%), and the mixture of gums (0.37%) significantly lowered serum separation of the mixture. In the presence of gums, viscous, and elastic behaviors were observed at low and high frequencies, respectively. They hypothesized that stabilizing activity of soluble fraction of Persian gum is due to its adsorbing nature, which can be adsorbed onto casein micelles and subsequently can stabilize the system through electrostatic and steric repulsions (Abbasi and Mohammadi, 2013). A wide types and names of fermented milk beverages are found in different countries like Lassi in India, Ayran in Turkey, drinking yogurt in Europe, kefir, and kumis in the Middle East and Doogh in Iran (Karim et al., 2017). 'Doogh’ (Iranian fermented dairy-based drink) is a native beverage in Iran, which is produced through mixing set/stirred yogurt, water, salt, and in some cases aromatic compounds. It is an acidified milk drink with low pH values (<4.0), which leads to aggregation of protein caseins followed by the phase separation (Azarikia and Abbasi, 2010). Therefore, some bioactive hydrocolloids have been used to stabilize this product (Azarikia and Abbasi, 2010; Hashemi et al., 2015; Karim et al., 2017). In this regard, Nabizadeh et al. (2014) used a mixture of Persian gum (0, 0.2, and 0.4%) and milk permeates (0, 25.0, and 50.0%) to stabilize Doogh against phase separation. Results showed that increasing the levels of Persian gum and milk permeate increased the viscosity and declined the phase separation. High concentrations of Persian gum caused an increase in acidity of product, while did not affect the pH value probably due to the buffering capacity of Persian gum derived from its protein moiety. Milk permeates and Persian gum decreased the flavor score and increased the consistency score of functional Doogh, respectively. In another study, Karim et al. (2017) evaluated the physical stability and rheological attributes of Doogh containing long-chain inulin (0-2.34%) and modified starch (0-0.58%) during 30 days of refrigerated storage. The addition of inulin and modified starch resulted in a functional Doogh with improved physical stability, apparent viscosity, and viscoelastic attributes. G' was higher than G" in fortified Doogh and they finally stated that the samples containing 2.0% inulin and 0.5% modified starch or 1.18% inulin and 0.58% modified starch can be used to produce a functional Doogh having appropriate physicochemical and rheological attributes besides their health benefits.
Starch-based dairy desserts comprised of milk, sucrose, thickeners (starch and hydrocolloids), aroma, and colorants. They are extensively consumed in Europe as commercial products like ‘Vanilla via’ in The Netherlands, ‘Natillas’ in Spain and ‘Creme dessert’ in France. These products are consumed by children or elderly people due to their nutritional and sensory attributes (Tarrega and Costell, 2006). Incorporation of inulin into fat-free starch-based desserts containing 2.5, 3.25, and 4.0% starch resulted in a functional product with improved G' and complex viscosity and reduced tan 6 value, except for the sample contained 4.0% starch. The sweetness, thickness, and creaminess of fat-free dairy model desserts were also increased upon inulin addition. Furthermore, skimmed-milk desserts containing inulin at low starch levels were sweeter and showed more vanilla flavor and same thickness compared to the whole milk desserts, but the latter was creamier and thicker at 4.0% starch (Tarrega and Costell, 2006). In another study, Gonzalez-Tomas et al. (2008) studied the effect of inulin average chain length on the viscoelasticity of starch-based dairy systems. A significant interaction effect was observed between inulin-type, concentration, and starch concentration on the G', G", tan 6, and complex viscosity in both inulin-enriched desserts obtained from full-fat and skimmed-milks. The addition of 7.5% long-chain inulin significantly increased G', G", and complex viscosity and declined tan 6 levels in all desserts (Gonzalez-Tomas et ah, 2008). In addition, the inclusion of 7.5% inulin into starch-based dairy systems led to a system with more pseudoplastic, thixotropic, consistent, and elastic behaviors (Torres et ah, 2010).
Dietary fibers and some plant-based carbohydrate hydrocolloids have been used as fat replacers in whipped cream. The effect of inulin on the rheological attributes of whipped cream was studied by Hu and Jin (2008). Functional whipped creams containing 50% inulin as a fat replacer presented similar yield stress, thixotropy, G', and G" compared to the full-fat cream. The physical, textural, and rheological characteristics of low-fat whipped cream (30% fat content) were also evaluated in the presence of different gums (0.1 and 0.3%) extracted from Basil, Cress, and Quince seeds (Farahmandfar et ah, 2017). All fortified samples exhibited shear-thinning behavior and had yield stress and thixotropy properties. Gum addition and also increase the level of gum supplementation led to an increase in viscosity and overrun and low-fat whipped creams containing basil seed gum showed higher G', G", complex viscosity, hardness, and adhesiveness than those obtained from two other gums. All the above-mentioned gums can be used as fat replacers in the formulation of low-fat whipped cream.